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U.H.F. radio echo sounding of Yukon glaciers 1979

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4 " U.H.F. BADIO ECHO SOUNDING OF YUKON GLACIERS by BRIAN BASRY NAROD B . S c , U n i v e r s i t y of B r i t i s h Columbia, 1970 13.Sc., U n i v e r s i t y of B r i t i s h Columbia, 1975 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY ' i n THE FACULTY OF GRADUATE STUDIES (Department of Geophysics and Astronomy) We accept t h i s t h e s i s as conforming to the r e q u i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA June, 1979 ((c) B r i a n Barry Narod, 1979 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the Head of my Department or by his representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my wri tten permission. GEOPHYSICS & ANSTRONOMY Department of The University of British Columbia 2075 Wesbrook P l a c e Vancouver, Canada V6T 1W5 June 25, 1979 Date F r o n t i s p i e c e . An a e r i a l f i s h e y e photograph taken over the Hazard G l a c i e r . These photographs provide : f l i g h t l i n e c o n t r o l . The s u r f a c e drainage f e a t u r e seen i n t h i s photograph i s v i s i b l e on a government a e r i a l photograph taken at 15,000 m e l e v a t i o n . The l o c a t i o n of t h i s photograph i s marked by an a s t e r i s k on F i g u r e A2.2. iii i v IBST RACT - a h i g h - r e s o l u t i o n r a d i o echo sounder o p e r a t i n g at a freguency of 840 MHz has been developed f o r sounding of s m a l l and medium-sized p o l a r g l a c i e r s and i c e caps. The sounder uses a compact, hi g h - g a i n antenna which improves the system performance, suppresses v a l l e y w a l l echoes and s i m p l i f i e s o p e r a t i o n from l i g h t a i r c r a f t . S u c c e s s f u l f i e l d t r i a l s were c a r r i e d out on the Eusty, T r a p r i d g e and Hazard G l a c i e r s , Yukon T e r r i t o r y , Canada. R e s u l t s of a i r b o r n e surveys compare w e l l with i c e depths o b t a i n e d from e a r l i e r ground-based soundings on the Rusty and Tra p r i d g e G l a c i e r s . The maximum i c e t h i c k n e s s encountered was 200 m on Hazard G l a c i e r . Owing to the high o p e r a t i n g freguency, random s c a t t e r i n g from inhomogeneities w i t h i n the i c e i s a major cause of s i g n a l d e g r a d a t i o n . For t h i s reason the sounder cannot penetrate great t h i c k n e s s e s of temperate o r d e b r i s - r i c h i c e . S p a t i a l a v e r a g i n g , an immediate r e s u l t of o p e r a t i n g from a moving p l a t f o r m , reduces the e f f e c t s of b a c k - s c a t t e r e d " c l u t t e r . " R e s u l t s of ground-based t e s t s on the Hazard G l a c i e r y i e l d a value f o r f t a n 8 = 0.26 at - 5 0 C , i n agreement with p r e d i c t e d values. The t o t a l r e c e i v e d power and the echo d e t a i l s have both been found to be very s e n s i t i v e to s m a l l (<<I0 cm) changes i n antennae p o s i t i o n . Large f l u c t u a t i o n s i n power, caused by roughness a t or near the i c e / a i r s u r f a c e , prevented using s i n g l e coverage data t o d e t e c t b i r e f r i n g e n c e i n g l a c i e r i c e . The r e s u l t s a l s o i n d i c a t e that the standard photographic r e c o r d s should be r e p l a c e d by a r e c o r d i n g medium capable of V s t o r i n g more p r e c i s e and a c c e s s i b l e data. A storage medium such as magnetic tape should not degrade the radar data, and would at the same time r e l i e v e a data p r o c e s s i n g burden. v i TABLE OF CONTENTS Ab s t r a c t - i v L i s t Of Tables v i i i L i s t Of F i g u r e s i x Acknowledgements x i i Chapter 1: I n t r o d u c t i o n 1 1.1 Background 2 1.2 Program Development ... 4 1.3 F i e l d Work 6 Chapter 2: Airborne Sounding Of G l a c i e r s .................. 8 2.1 I n s t r u m e n t a t i o n 8 2.2 Survey Procedure 12 2.2.1 F l i g h t L i n e A n a l y s i s 16 2.3 R e s u l t s 17 2.4 Concluding Remarks To A i r b o r n e Surveys 24 Chapter 3: P h y s i c a l P r o p e r t i e s Of G l a c i e r s ................ 26 3.1 Experimental D e s c r i p t i o n 26 3.2 Data A n a l y s i s 27 3.2.1 E r r o r s In Power Measurements - 28 3.2.2 D i e l e c t r i c A t t e n u ation 38 3.2.3 S c a t t e r e d Power Densi t y Vs. Depth ............ 41 3.3 D e t e c t i o n Of Large Conduit S c a t t e r e r s 43 3.3.1 T h e o r e t i c a l P a t t e r n s For Conduit S c a t t e r e r s ...-43 3.3.2 Comparisons With The F i e l d Experiments 59 3.4 Concluding Remarks To Chapter 3 59 Chapter 4. Concluding Remarks And Recommendations For Future Experiments 61 v i i L i t e r a t u r e C i t e d 63 Appendix 1; D e t a i l s Of The Radio Echo Sounder 67 A1.1 General D e s c r i p t i o n And Operation 67 A1. 1 - 1 System Assembly 68 A1.1.2 Operation Of The Radio Echo Sounder 75 A1.2 The T r a n s m i t t e r 78 A1.2. 1 Power Supply .. 79 A1.2.2 Modulator 89 A 1.2. 3 The R. F. Chain 92 A1.3 The Re c e i v e r 106 A1.3.1 The R.F. Chain And Video A m p l i f i e r . . i 107 A1.3.1.1 P h y s i c a l D e c r i p t i o n 107 A1.3. 1.2 C i r c u i t D e s c r i p t i o n ,. 108 A i l . 3.2 Receiver D i g i t a l C i r c u i t r y .- 115 A1.4 The Switching Regulator Power Supply 138 A1.4.1 P r a c t i c a l C o n s i d e r a t i o n s 141 A 1.4. 2 C i r c u i t D e t a i l s .......... 142 A1.5 The Corner R e f l e c t o r Antenna 145 A1.5.1 Design D e t a i l s 146 A1.5.2 C a l i b r a t i o n : VSWR and Forward Gain 151 Appendix 2: T r a p r i d g e G l a c i e r And Hazard G l a c i e r F l i g h t L i n e Maps 154 Appendix 3; D i f f r a c t i o n From A L i n e a r Ribbon S c a t t e r e r .... 157 A3.1 Coordinate Systems : 157 A3.2 The K i r c h h o f f I n t e g r a l 160 A3.3 Numerical R a t i o n a l i z a t i o n ... 168 A3.4 Numerical A n a l y s i s ..... 172 A3.5 P h y s i c a l R e a l i z a t i o n ,. 179 V l l l LIST OF TABLES 2.1 System D e s c r i p t i o n And Parameters QJ^notmclukc 2.2 Compass E r r o r s 18 3.1 D i e l e c t r i c Loss Computation 39 A1: Power Connector P i n Des i g n a t i o n s 98 A2: T r a n s m i t t e r : Required Major Components ................ 99 A3: T r a n s m i t t e r : D i s c r e t e Components Part s L i s t 100 A4: Re c e i v e r R.F. Module Components 133 A5: Receiver Components: Required I n t e g r a t e d C i r c u i t s 134 A6: Beceiver D i s c r e t e Components P a r t s L i s t 135 A7: Switching Begulator P a r t s L i s t .........., 144 A8: Forward Gain Measurement Data 153 i x LIST OF FIGURES F r o n t i s p i e c e . i i i 2.1 Continuous Echogram From Hazard G l a c i e r . Surface. ....... 9 2.2 Antenna I n s t a l l a t i o n On A B e l l 206 H e l i c o p t e r ......... 12 2.3 Rusty G l a c i e r . F l i g h t L i n e 15 2.4 Rusty G l a c i e r A e r i a l S e c t i o n 16 2.5 T r a p r i d g e G l a c i e r Ice Thickness Map 20 2.6 Hazard G l a c i e r Ice Thickness Map 22 2.7 Transverse S e c t i o n Of Hazard G l a c i e r 23 3.1 Schematic Of The Antenna R o t a t i o n Experiments ......... 29 3.2 The 36 C o r r e c t e d Records Of Experiment TX.O ... 30 3.3 The 36 C o r r e c t e d Records Of Experiment TX.9 31 3.4 Averages Of TX.O, TX.9 Power Vs. Time 34 3.5 R e l a t i v e S c a t t e r e d Power Vs.. Azimuth ( l i n e a r ) ........ 35 3.6 R e l a t i v e S c a t t e r e d Power Vs. Azimuth (logarithm) 36 3.7 D i s c r e t e F o u r i e r Spectra Of Azimuthal Power 38 3.8 Thermal P r o f i l e Of Hazard G l a c i e r D r i l l S i t e #1 ,. 41 3.9 D i e l e c t r i c Losses And S c a t t e r e d Power 42 3.10 T h e o r e t i c a l R o t a t i o n P a t t e r n s For Corner R e f l e c t o r Antennae 45 3.11 T h e o r e t i c a l R o t a t i o n P a t t e r n s For Di p o l e Antennae .... 47 3.12 Rosette P l o t s Of Se l e c t e d Data From TX.O ............. 51 3.13 Rosette P l o t s Of S e l e c t e d Data From TX.9 . , . 53 3.14 Rosette P l o t s Of S e l e c t e d Data From TX.O A f t e r Azimuthal Smoothing 55 3.15 Rosette P l o t s Of S e l e c t e d Data From TX.9 A f t e r Azimuthal Smoothing 57 A1.1 Badio Echo Sounder Block Diagram 69 A1.2 T r a n s m i t t e r P i c t o r i a l Diagram ........................ 79 A1.3 26 V Begulator C i r c u i t Diagram 80 A1.4 Power Supply Timer C i r c u i t Diagram 81 A1.5 Power Supply Wiring Diagram 84 A1.6 Power Supply D r i v e r Schematic Diagram ................ 85 A1.7 T r a n s m i t t e r I n t e r n a l Layout 87 A1.8 Pulse A m p l i f i e r C i r c u i t Diagram 90 A1.9 Cathode Modulator C i r c u i t Diagram .................... 91 A1.10 120 MHz O s c i l l a t o r - A m p l i f i e r C i r c u i t Diagram ........ 93 A1.11 x6, x7 M u l t i p l i e r s C i r c u i t Diagram 94 A1. 12 840 MHz B. F. A m p l i f i e r C i r c u i t Diagram ., .,- 96 A'1.13 T r a n s m i t t e r Block Diagram ........................... 97 A1.14 Receiver P i c t o r i a l Diagram .. ... 107 A1.15 B. F. Module Connection Diagram ................... 109 A1.16 I . F. F i l t e r Bandpass C h a r a c t e r i s t i c .............. 111 A 1.17 Log. I. F. A m p l i f i e r C h a r a c t e r i s t i c 112 A1.18 Power Supply & Video A m p l i f i e r C i r c u i t Diagram 114 A1.19 High Speed Logic; L o g i c Diagram ...................., 117 A1.20 High Speed L o g i c ; C i r c u i t Diagram ...118 A1.21 High Speed L o g i c Timing Diagram 1 119 A1.22 High Speed Logic Timing Diagram 2 ................... 122 A-1.23 Low Speed L o g i c ; L o g i c Diagram 123 A1.24 Low Speed L o g i c ; C i r c u i t Diagram 125 A 1.25 Low Speed L o g i c Timing.Diagram 1 .................... 126 A1.26 Low Speed L o g i c Timing Diagram 2 .................... 128 A1.,27 Low Speed L o g i c Timing Diagram 3 129 A1.28 Fr o n t Panel D i s p l a y ; C i r c u i t Diagram 131 x i A1.29 Receiver Connection Diagram ......................... 132 A1.30 Switching Regulator Block Diagram 139 A1.31 Switching R e g u l a t o r C i r c u i t Diagram 141 A1.32 Corner R e f l e c t o r Gain Vs. Spacing .................. 146 A1.33 Corner R e f l e c t o r Impedance Vs. Spacing ............. 146 A1.34 The Corner R e f l e c t o r Antenna - 148 A 1.35 T h e o r e t i c a l P a t t e r n s For Vari o u s Corner R e f l e c t o r Antennae 150 A1.36 A-scope Echogram Over Kluane Lake 152 A2.1 T r a p r i d g e G l a c i e r Composite Map Of C o n t r o l l e d F l i g h t L i n e s «... . 155 A2.2 Hazard G l a c i e r Composite Map Of C o n t r o l l e d F l i g h t L i n e s ..................................................156 A3.1 P i c t o r i a l Of S c a t t e r i n g Coordinate Systems ........... 158 A3.2 K i r c h h o f f D i f f r a c t i o n : P i c t o r i a l Of Numerical Model .. 173 A3.3 T y p i c a l F u n c t i o n J For Corner R e f l e c t o r Antennae ..... 178 x i i ACKNOWLEDGEMENTS I wish to thank Dr. G. K. C. C l a r k e f o r h i s support of t h i s p r o j e c t and f o r h i s i n v a l u a b l e a s s i s t a n c e d u r i n g a l l phases o f the f i e l d t r i a l s . I thank the N a t i o n a l Research C o u n c i l of Canada, Environment Canada and the U n i v e r s i t y of B r i t i s h Columbia Committee on A r c t i c and Alpine.Research f o r f i n a n c i a l support. The system development was f i n a n c e d by N a t i o n a l Research C o u n c i l g r a nts 67-3479 and 67-3809. Dr R. H. Goodman was generous with h i s time and a d v i c e . I am g r a t e f u l t o Parks Canada f o r a l l o w i n g t h i s work to be undertaken i n Kluane N a t i o n a l Park. While conducting the a e r i a l surveys we were based at the Kluane Research S t a t i o n of the A r c t i c I n s t i t u t e of North America; {I thank the I n s t i t u t e f o r l o g i s t i c support extending over many f i e l d seasons.) I thank P. Cary f o r h i s a s s i s t a n c e during the 1975 Yukon f i e l d t e s t . I thank Dr. S. G. C o l l i n s and J . G. Napoleoni f o r t h e i r a s s i s t a n c e d u r i n g the 1976 f i e l d work. The U.B.C. computing c e n t r e supported the production of the t h e s i s t y p e s c r i p t . I thank Dr. E. Hutchings f o r h i s e d i t o r i a l a s s i s t a n c e . 1 CHAPTER J : INTRODUCTION Th i s t h e s i s i s concerned with the development of U l t r a High Freguency (UHF) r a d a r s f o r the purpose of echo sounding p o l a r i c e masses. The work reported here i n c l u d e s the development at U.B.C. of an 840 MHz r a d i o echo sounder and the r e s u l t s of f i e l d t e s t s made during the. 1976 f i e l d season. This chapter i n c l u d e s a b r i e f background t o UHF echo sounding as w e l l as a d e s c r i p t i o n of the p r o j e c t development and the f i e l d work. Chapter 2 d e s c r i b e s the radar developed at U.B.C. as w e l l as the procedures and r e s u l t s o f a i r b o r n e t e s t s . Appendix 1 i s a complete t e c h n i c a l d e s c r i p t i o n of the system.. Chapter 3 with Appendix 3 d e s c r i b e s the r e s u l t s of attempts to use the sounder t o study g l a c i e r i c e f a b r i c and i n t r a g l a c i a l s t r u c t u r e s . Chapter 4 summarizes the r e s u l t s and c o n s i d e r s how t o improve f u t u r e experiments. T h i s r e s e a r c h was motivated p r i m a r i l y by the d e s i r e to develop a r a d i o echo sounder optimized f o r i c e depths t y p i c a l l y expected i n the Canadian A r c t i c , of p a r t i c u l a r i n t e r e s t were the c o l d v a l l e y g l a c i e r s of the northern St. E l i a s Mountains, and the i c e caps of the A r c t i c A r c h i p e l a g o , although our f i e l d work di d not i n c l u d e the l a t t e r area. V a l l e y g l a c i e r s have s u f f i c i e n t l y d i f f e r e n t flow c h a r a c t e r i s t i c s from the more commonly s t u d i e d i c e caps, t h a t we a l s o wished to develop a technique f o r monitoring t h e i r p h y s i c a l p r o p e r t i e s . Features o f i n t e r e s t i n c l u d e d g l a c i a l p r o p e r t i e s such as bedrock roughness, and the d i s t r i b u t i o n s of s c a t t e r i n g o b j e c t s , l a y e r s and c o n d u i t systems (Clough, 1977; H a r r i s o n , 1973; Smith and Evans, 1972). Ice f a b r i c p r o p e r t i e s i n c l u d e d p o s s i b l e s t r a i n alignment of 2 o p t i c a l axes and s t r e s s induced o p t i c a l ( R . F . ) a n i s o t r o p y (Campbell, and Orange, 1974; J o h a r i , and Jones, 1975). A h i g h r e s o l u t i o n UHF radar o f f e r e d both an i c e depth measurement c a p a b i l i t y f o r A r c t i c g l a c i e r s as well as a p o t e n t i a l s e n s i t i v i t y t o p h y s i c a l p r o p e r t i e s of g l a c i e r s . A wavelength i n a i r of about 30 cm would make p o s s i b l e the use of hi g h gain aperture antennae as w e l l as s i m p l i f y i n g the ex e c u t i o n of most s u r f a c e experiments. A wavelength i n i c e of about 20 cm would make a radar s e n s i t i v e to e f f e c t s caused by s m a l l e r v a r i a t i o n s i n bedrock roughness, i n t r a g l a c i a l s t r u c t u r e s , and c r y s t a l l o g r a p h i c p r o p e r t i e s than those v a r i a t i o n s d e t e c t a b l e at lo n g e r wavelengths. Although i n s t r u m e n t a t i o n design and development were the most time-consuming p a r t s of t h i s r e s e a r c h , the. motivation was p r i m a r i l y g l a c i o l o g i c a l . For t h i s reason the d e t a i l e d system d e s c r i p t i o n and o p e r a t i n g manual are r e l e g a t e d to the appendix. The r e s u l t s presented here demonstrate the usefulness of UHF r a d i o echo sounders f o r the study o f g l a c i e r s . 1.1 BACKGROUND The behaviour of UHF (300 MHz-3 GHz) ele c t r o m a g n e t i c waves i n l a r g e i c e masses and the u t i l i t y of UHF r a d i o echo sounding have r e c e i v e d r e l a t i v e l y l i t t l e i n v e s t i g a t i o n compared with r a d i o echo sounding i n the lower VHF (30-300 MHz) band. Greater d i e l e c t r i c l o s s e s and high e r s u s c e p t i b i l i t y to s c a t t e r i n g have l i m i t e d the u s e f u l n e s s o f UHF sounders on l a r g e p o l a r i c e sheets, the f i r s t r e g i o n s of e x t e n s i v e r a d i o echo sounding. Waite (1966), using an SCR-718 440 MHz a i r c r a f t a l t i m e t e r i n 3 northwest Greenland, rep o r t e d l o s s of s i g n a l at depths exceeding 400 m. VHF sounders have, no d i f f i c u l t y sounding i c e many times t h i s t h i c k n e s s . On smal l .and medium-sized v a l l e y g l a c i e r s , v a l l e y - w a l l r e f l e c t i o n s and a i r c r a f t man-oeuvrability, r a t h e r than i c e p e n e t r a t i o n depth, are the main c o n s i d e r a t i o n s ; thus the s m a l l s i z e and d i r e c t i v i t y of DHF antennae become a t t r a c t i v e - In 1970 on R o s l i n G l e t s c h e r , Davis and others (1973> used, a UHF sounder to measure i c e t h i c k n e s s e s i n a c o l d v a l l e y g l a c i e r . Man-hauling a modified SCR 718 r a d i o a l t i m e t e r they were ab l e to measure i c e t h i c k n e s s e s up t o 400 m; a l l p r e v i o u s soundings using the SCR 718 had been made on p o l a r i c e caps. They r e p o r t e d t h a t s c a t t e r e d r e t u r n s at many l o c a t i o n s o f t e n made i d e n t i f i c a t i o n of a d i s t i n c t bottom echo d i f f i c u l t (Smith and Evans, 1972). The f i r s t UHF radar designed s t r i c t l y as an i c e depth sounder was a 620 MHz instrument b u i l t f o r the Department of the Environment o f Canada (DOEC) by Goodman (1975). R e s u l t s of man- hauled surveys of the Rusty and Trap r i d g e G l a c i e r s demonstrated t h a t the DOEC system was capable of f i n e r r e s o l u t i o n than e x i s t i n g VHF systems, and th a t v a l l e y w a l l echoes and r a p i d l y v a r y i n g bedrock topography did not s e r i o u s l y a f f e c t the sounder's performance. As with the SCR 718, i n t e r n a l s c a t t e r e r s c o u l d have made the i d e n t i f i c a t i o n of a d i s t i n c t bottom echo ambiguous. Sondergaard and Skou (1976) using a 6 Kw, 300 MHz radar have reported some successes with a i r b o r n e sounding of the Greenland Ice Cap, however as an i c e depth measurement t o o l i t 4 l a c k s the p e n e t r a t i o n of t h e i r 60 MHz system. B o g o r o d s k i i has operated a 700 MHz system with a range l i m i t of about 300 m (Bentley, 1979). 1.2 PEOGEAM DEVELOPMENT In 1973 we began development of a r a d i o echo sounder f o r use i n northern Canada. The need t o operate on small g l a c i e r s d i c t a t e d the sounder's p r o p e r t i e s . We chose 840 MHz i n the u l t r a h i g i . frequency (DHF) band as the ce n t r e frequency f o r s e v e r a l reasons. Although d i e l e c t r i c l o s s e s and random s c a t t e r i n g i n c r e a s e with frequency, a high^-gain. antenna can o f f s e t much of the l o s s ; the s m a l l s i z e of an DHF antenna s i m p l i f i e s a i r b o r n e o p e r a t i o n . Most Canadian polar i c e masses are expected to be w i t h i n the maximum range of an UHF sounder (Narod, unpublished)* The system development took p l a c e at U.B.C. We completed the system s p e c i f i c a t i o n s i n 1974, and completed the f i r s t working v e r s i o n of the sounder i n the s p r i n g of 1975. The r e c e i v e r , antennae, power supply, intercom and camera i n t e r v a l o m e t e r were a l l designed a t U.B.C. The t r a n s m i t t e r design and f a b r i c a t i o n were completed by Microwave C o n t r o l Co., New J e r s e y , U.S.A. We proposed s e v e r a l experiments, each designed to t e s t the c a p a b i l i t y and l i m i t a t i o n s o f . t h e new sounder. By working with two antennae on a g l a c i e r s u r f a c e .we hoped t o d e t e c t b i r e f r i n g e n c e i n the g l a c i e r i c e . We f e l t t h a t the s h o r t wavelength (20 cm i n ice) would f a c i l i t a t e t h i s t e s t because the r e l a t i v e l y s m a l l antennae (1.5 m) would be e a s i l y manipulated. Using a s i n g l e antenna we proposed to operate the system 5 from l i g h t a i r c r a f t . These f l i g h t t e s t s would measure the sounder's a b i l i t y t o penetrate both p o l a r and temperate i c e . Two o t h e r a s p e c t s of these t e s t s would be the determination of the i n t e r f e r i n g e f f e c t s of v a l l e y w a l l s , and the problems a s s o c i a t e d with o p e r a t i n g a e r i a l surveys i n s m a l l v a l l e y s and i n other areas where very p r e c i s e f l i g h t l i n e c o n t r o l i s necessary. Photographic data r e c o r d s were to be used f o r a l l t e s t s . The f i r s t f i e l d t r i a l took p l a c e i n May, 1975 on the Athabasca G l a c i e r , A l b e r t a , Canada. The t e s t was terminated e a r l y as a r e s u l t of a f a i l u r e of the t r a n s m i t t e r high v o l t a g e supply, but not before we observed a very high l e v e l of r e t u r n i n g s c a t t e r e d power. F u r t h e r p r e l i m i n a r y f i e l d t r i a l s took p l a c e d u r i n g June and J u l y , i n the St. E l i a s Mountains, Yukon T e r r i t o r y , Canada. R e s u l t s o f t e s t s c a r r i e d out on the s u r f a c e of the Rusty G l a c i e r prompted m o d i f i c a t i o n s to the antennae and t o the t r a n s m i t t e r t r i g g e r c i r c u i t . Airborne t e s t s were c a r r i e d out from a Hughes 500 h e l i c o p t e r . These r e s u l t e d i n m o d i f i c a t i o n s to the video a m p l i f i e r . The 1975 f l i g h t t e s t s were made without f l i g h t l i n e c o n t r o l . A f i n a l f l i g h t check, p r i o r to the 1976 f i e l d work, took p l a c e i n e a r l y August, i n the Vancouver, Canada area. Operating from a Cessna 180 a i r c r a f t a s u c c e s s f u l systems check was performed with the modified radar, a new intercom and a f l i g h t l i n e camera. The t e s t was simply a hardware check, and although the f l i g h t i n c l u d e d passes over s e v e r a l temperate g l a c i e r s no i n t e r n a l echoes were detected. 6 1.3 FIELD WORK In August 1976 we t e s t e d the sounder on g l a c i e r s i n the S t . E l i a s Mountains, Yukon T e r r i t o r y , Canada. The f i e l d work took two forms, a i r b o r n e sounding, and g l a c i e r p h y s i c s experiments. The a i r b o r n e experiments took place p r i m a r i l y on three g l a c i e r s i n the S t e e l e Creek b a s i n . E x t e n s i v e g l a c i o l o g i c a l work had p r e v i o u s l y been done on two of these g l a c i e r s , the Rusty and T r a p r i d g e , so the thermal regime and i c e depth were known a t a number of s i t e s ; a network of survey markers provided ground c o n t r o l p o i n t s . To get s i m i l a r i n f o r m a t i o n about Hazard G l a c i e r we set up a f i e l d camp and c a r r i e d out a l e v e l l i n g survey, ground-based experiments with the radar, hot-water d r i l l i n g and i c e temperature measurements. L a t e r i n August, using a B e l l 206 h e l i c o p t e r , we d i d the a e r i a l surveys of t h e s e : g l a c i e r s . The g l a c i e r p h y s i c s experiments took place at our camp on the Hazard G l a c i e r at d r i l l s i t e #1 (Appendix 2) . These experiments i n v o l v e d r o t a t i n g a r e c e i v e r antenna about a v e r t i c a l a x i s f o r one of two orthogonal t r a n s m i t t e r antenna o r i e n t a t i o n s . These experiments were designed t o recover the e l l i p s e s of p o l a r i z a t o n of r e f l e c t i o n s from s c a t t e r i n g o b j e c t s and from the bedrock. The e l l i p s e s would p r o v i d e i n f o r m a t i o n about a n i s o t r o p y w i t h i n the i c e and about d e p o l a r i z a t i o n due to s c a t t e r i n g (Beckmann and S p i z z i c h i n o , 1963). I t i s worth n o t i n g here t h a t the i n s t a n t photography used f o r data r e c o r d i n g would not allow f o r any a n a l y s i s i n the f i e l d , and hence the g u a l i t y of the data gathered from the Hazard G l a c i e r s u r f a c e c o u l d not be e f f e c t i v e l y judged t h e r e . 7 On the other hand, the i n s t a n t photography was very s u c c e s s f u l at i n d i c a t i n g data q u a l i t y d u r i n g the a i r b o r n e t e s t s . There the t a s k mainly r e q u i r e d the d e t e c t i o n of a bedrock echo, a f a r s i m p l e r task than a n a l y s i n g an e n t i r e waveform. Oswald (1975) has a l s o commented on the d i f f i c u l t y with which he. used photographic r e c o r d s f o r s t a t i s t i c a l a n a l y s e s . The m o t i v a t i o n f o r using frame by frame photography was two-fold. Photography i s an e a s i l y a c q u i r e d technique f o r r e c o r d i n g broadband data both c o n t i n u o u s l y and i n s t a n t a n e o u s l y . A l s o , o t h e r i n v e s t i g a t o r s have had a long h i s t o r y of using photographic r e c o r d i n g (Sobin, 1975; Gudmandsen and o t h e r s , 1976). We were guided to some extent by t h e i r experience. 8 CHAPTER 2: AIRBGfiNE SGUNDMG OF GLACIERS The U n i v e r s i t y o f B r i t i s h Columbia (UBC) r a d i o echo sounder, which i s s i m i l a r i n concept to the DOEC system, has been s p e c i f i c a l l y designed t o sound the smaller polar g l a c i e r s and i c e caps found i n northern Canada (Narod, u n p u b l i s h e d ) . I t s c e n t r e frequency i s 840 MHz, bandwidth 40 MHz and system performance i s 124 dB. The 35% i n c r e a s e i n frequency over t h a t of the DOEC system b r i n q s i n c r e a s e d s u s c e p t i b i l i t y t o i n t e r n a l s c a t t e r i n g and i i g h e r d i e l e c t r i c l o s s e s , but these drawbacks are o f f s e t by the high g a i n and smal l s i z e of the antenna and the ease with which the e n t i r e system i s made a i r b o r n e . Surface echograms demonstrate t h a t s c a t t e r i n g r e t u r n s vary g r e a t l y with minute changes i n antenna p o s i t i o n ( B a i l e y and o t h e r s , 1964). By moving the antenna while c o n t i n u o u s l y r e c o r d i n g , (Fig..2.1) the r e l a t i v e l y constant bottom echo can be i d e n t i f i e d among the h i g h l y . v a r i a b l e . s c a t t e r i n g r e t u r n s . When a i r b o r n e , the s c a t t e r i n g r e t u r n s vary too r a p i d l y t o be v i s i b l e on an o s c i l l o s c o p e phosphor. 2.1 INSTRUMENTATION The UBC echo sounder comprises a t r a n s m i t t e r , r e c e i v e r , c i r c u l a t o r , antenna and o s c i l l o s c o p e d i s p l a y . Table 2.1 l i s t s r e l e v a n t system parameters; complete system d e t a i l s are i n c l u d e d i n Appendix 1. The system performance of the radar t r a n s c e i v e r ( t r a n s m i t t e r , r e c e i v e r and c i r c u l a t o r ) i s 124 dB. Adding the two-way antenna gain of 31 dB, the e f f e c t i v e system performance i s 155 dB. Both the t r a n s m i t t e r and r e c e i v e r are i n t e r n a l l y F i g u r e 2.1 A Continuous Echogram From Hazard G l a c i e r S u r f a c e A continuous echogram taken on the s u r f a c e , near d r i l l s i t e 1 on Hazard G l a c i e r , showing s i g n i f i c a n t s c a t t e r e d power r e t u r n i n g both before and a f t e r the dominant bottom echo. T h i s r e c o r d was made by r o t a t i n g the antenna 360<> around a v e r t i c a l a x i s . The b i t code a t the l e f t i s a system-generated data i d e n t i f i e r (see Appendix 1.3). protected a g a i n s t abnormal power surges caused by c a b l e f a i l u r e s . A 120 hHz s i g n a l from a c r y s t a l o s c i l l a t o r i s 10 Table 2.1 System Description, And Parameters T r a n s m i t t e r : Gated dual microwave c a v i t y t r i o d e a m p l i f i e r . Frequency i s s e t by c r y s t a l . Power 4.1 Kw peak rms (+66 dBm) Pulse l e n g t h & r a t e 50 ns at 10 KHz R i s e time 18 ns F a l l time 28 ns R e c e i v e r : T h i n f i l m s o l i d s t a t e h y b r i d . Logarithmic response. Bandwidth 40 MHz Intermediate frequency 120 MHz Dynamic range 80 dB S e n s i t i v i t y -70 dBm System l o s s e s 12 dB ( i n c l u d i n g I.F. c o n v e r s i o n loss) T/R Switch: Passive c i r c u l a t o r I s o l a t i o n 25 dB 1 dB Bandwidth >40 MHz Antenna: Two d i p o l e c o l i a e a r a r r a y with a t h i r d p a r a s i t i c element and a 90° corner r e f l e c t o r . 1 dB Bandwidth >40 MHz VSWR 1.14 Forward gain 15.5 dB ± 1 dB Depth 0.30 m Width 0.59 m Length 1.18 m Weight 9 Kg General: T o t a l system weight 50 Kg Power r e g u i r e d 28V 5) 10A Estimated maximum range i n c o l d i c e 650 m m u l t i p l i e d t o 720 MHz and 840 MHz t o provide the l o c a l o s c i l l a t o r and c a r r i e r f r e q u e n c i e s r e s p e c t i v e l y . The c a r r i e r i s then a m p l i f i e d , gated and i s o l a t e d a t the 4 Kw l e v e l . The c i r c u l a t o r i s a t h r e e - p o r t f e r r i t e d e v i c e which allows the system t o operate with a s i n g l e antenna. The r e c e i v e r i n p u t i s p r o t e c t e d by a s o l i d - s t a t e l i m i t e r . The s i g n a l i s converted to 11 the 120 MHz intermediate frequency and f i l t e r e d . The I.F. a m p l i f i e r - d e t e c t o r has a l o g a r i t h m i c response c h a r a c t e r i s t i c with a u s e f u l dynamic range of 80 dB. The antenna i s a 90° corner r e f l e c t o r with two d r i v e n d i p o l e elements. I t s measured forward g a i n i s 15.5±1.0 dB. The estimated E-plane and H-plane h a l f power beamwidths are 18<> and 44° r e s p e c t i v e l y . The antenna i s compact enough t o be a t t a c h e d to the cargo hook of any h e l i c o p t e r with high s k i d gear. On our August 1976 f l i g h t s we o u t r i g g e d the antenna from the h e l i c o p t e r , i n an experimental i n s t a l l a t i o n ( F i g . . 2 . 2 ) . The video output from the r e c e i v e r modulates the phosphor i n t e n s i t y of a T e k t r o n i x model 475 o s c i l l o s c o p e . A slow ramp on the v e r t i c a l i n p u t scans the t r a c e through the f u l l s creen h e i g h t i n one minute. The o p e r a t o r manually c o n t r o l s the v e r t i c a l scan and a Polaroid-backed o s c i l l o s c o p e camera r e c o r d s the data. T h i s r e s u l t s i n approximately 20% dead time. (We recommend t h a t i n f u t u r e the photographic r e c o r d i n g system be r e p l a c e d by a magnetic r e c o r d e r or g r a p h i c r e c o r d e r and a r e , i n f a c t , developing such a system.) 2.2 SURVEY PROCEDURE As w e l l as the a r r i v a l time of the bed echo, u s e f u l sounding data r e q u i r e knowledge of a i r c r a f t p o s i t i o n and ground c l e a r a n c e . The UBC sounder, when used as i t s own r a d i o O v e r l e a f : F i g u r e 2.2. The UBC r a d i o echo sounder antenna i n s t a l l e d on a B e l l 206 h e l i c o p t e r . 12 13 a l t i m e t e r , r e c e i v e s a s t r o n g echo from the i c e s u r f a c e . I t i s necessary, however, t o f l y at l e a s t 40 m above.the i c e s u r f a c e i n order to separate the t r a n s m i t t e d pulse from the f i r s t r e c e i v e d p u l s e . The smal l dynamic range of the phosphor and f i l m cause t h i s l i m i t a t i o n , An improved r e c o r d i n g system could reduce the minimum r e q u i r e d e l e v a t i o n to l e s s than 25 m above the i c e s u r f a c e . A l t e r n a t e l y , f l y i n g as c l o s e to the s u r f a c e as p o s s i b l e , the p i l o t can use v i s u a l r e f e r e n c e s (survey markers, etc.) to c o n t r o l h i s e l e v a t i o n and maintain a c o n s t a n t c l e a r a n c e above the i c e s u r f a c e . The advantage of the l a t t e r procedure i s a g r e a t e r s i g n a l - t o - n o i s e r a t i o (Swithinbank, 1968) . I t s disadvantages are s e v e r a l : reduced a i r speed, reduced accuracy (the p i l o t cannot maintain a p e r f e c t l y constant h e i g h t above the s u r f a c e ; we have estimated our low l e v e l height at 6±2 m) and poor f l i g h t - l i n e photography—-not to mention d i s c o m f o r t due to a i r s i c k n e s s and i n c r e a s e d r i s k o f c r a s h i n g . Data f o r Busty G l a c i e r were c o l l e c t e d from h i g h e l e v a t i o n ( F i g s . 2.3 and 2.4); data from the Trap r i d g e G l a c i e r were c o l l e c t e d from both high and low e l e v a t i o n s ; data from the Hazard G l a c i e r were c o l l e c t e d o n l y a t low e l e v a t i o n . For f l i g h t l i n e r e c o r ds we used a combination of dead reckoning and a e r i a l photography. A tape r e c o r d i n g of the a i r c r a f t intercom was -verbally synchronized with the data c o l l e c t i o n . N a v i g a t i o n i n f o r m a t i o n i n c l u d e d compass headings, a i r s p e e d s , and v i s u a l r e f e r e n c e s . A e r i a l photography with a 210°-coverage f i s h e y e l e n s was a l s o synchronized with the data c o l l e c t i o n . Our i n t e n t i o n was t o take photographs every 10 s, which, when compared t o l a r g e - s c a l e photographs, would provide 14 l o c a t i o n s and headings ( f r o n t i s p i e c e ) . U n f o r t u n a t e l y photographic f l i g h t c o n t r o l was incomplete due to e r r a t i c behaviour o f t h e motor-driven Nikon camera caused by a i r c r a f t v i b r a t i o n s (the camera has now been r e p l a c e d by a 70 mm V i n t e n a e r i a l r e c o n n a i s s a n c e camera). 2.2.1 FLIGHT LINE ANALYSIS Ve r b a l r e f e r e n c e s to a i r s p e e d and a i r c r a f t heading are r e c o v e r a b l e with a t i m i n g accuracy of s e v e r a l seconds. S i n c e these values change r e l a t i v e l y s l o w l y , more p r e c i s e t i m i n g i s not needed. References t o v i s u a l cues such as s t a k e s l o c a t e d i n the- g l a c i e r can be r e f e r e n c e d to the data with an accuracy of about 1 second. With t y p i c a l a i r s p e e d s of 40-60 Km hr~* (10- 15 m s -*) on the Hazard G l a c i e r and Rusty G l a c i e r and l e s s on the T r a p r i d g e G l a c i e r along-path plan accuracy can be kept to l e s s than 50 m. Across-path dead reckoning t o l e r a n c e s are determined by the O v e r l e a f ; F i g u r e 2 .3 . The f l i g h t path of the p r o f i l e reproduced i n F i g u r e 2.4. The r e g i o n shown i s at 61°15'N, 140O20«W. Second o v e r l e a f : F i g u r e 2 .4 . C r o s s - s e c t i o n of the Rusty G l a c i e r showing p h o t o g r a p h i c a l l y - r e c o r d e d data. The s m a l l c i r c l e s a t the i c e s u r f a c e r e p r e s e n t the c e n t r e l i n e survey s t a k e s . The l a r g e r c i r c l e s a t the bedrock boundary i n d i c a t e the i c e depths measured with the DOEC system (Clarke and Goodman, 1975). V e r t i c a l e x a g g e r a t i o n i s 4 : 1 . The data records show c l e a r s e p a r a t i o n of the t r a n s m i t t e d p u l s e , i c e s u r f a c e r e f l e c t i o n and i c e bottom r e f l e c t i o n , even over i c e as t h i n as 30 m. The dark v e r t i c a l bars are s y n c h r o n i z i n g marks with the 35 mm camera or with v e r b a l cues recorded on the f l i g h t r e c o r d e r . The v e r t i c a l s c a l e i s 500 ns d i v i s i o n - 1 . Data f o r the c r o s s - s e c t i o n were compiled from two passes of i d e n t i c a l plan and o v e r l a p p i n g p r o f i l e (one not shown).  16 NOI1VA313 17 accuracy of compass and v i s u a l cue r e f e r e n c e s . Headings were r e f e r r e d from the a i r c r a f t magnetic compass. We found an apparent s y s t e m a t i c d i s c r e p a n c y of 12° between observed headings and headings p l o t t e d on a e r i a l photographs using a l l a v a i l a b l e i n f o r m a t i o n . T h i s d i f f e r e n c e can be accounted f o r by c o n s i d e r i n g s e v e r a l p o s s i b l e sources of e r r o r (Table 2.2). Values f o r a i r c r a f t d e v i a t i o n were provided by the c h a r t e r i n g a i r l i n e . Magnetized m a t e r i a l s i n the r a d i o echo sounder ( i s o l a t o r and c i r c u l a t o r ) i n t r o d u c e d e v i a t i o n . Rosette e r r o r r e f e r s t o our i n a b i l i t y t o match our ground survey c o o r d i n a t e system to p a r a l l a x - a f f e c t e d l a r g e s c a l e a e r i a l photos. C a r t e s i a n e r r o r r e f e r s t o our i n a b i l i t y t o o r i e n t the a e r i a l photo with r e s p e c t to p u b l i s h e d maps of the area. D i s t o r t i o n . e r r o r r e f e r s to n o n l i n e a r i t i e s i n t r o d u c e d by photographic enlargement o p t i c s . However, the accepted f l i g h t l i n e s are w e l l t i e d to v i s u a l r e f e r e n c e s . Across path plan accuracy from dead reckoning . has been estimated a t b e t t e r than 50 m. The best q u a l i t y f l i g h t l i n e c o n t r o l came from the f i s h e y e f l i g h t l i n e photography. These photographs provided t i e p o i n t s accurate t o about 10 m (the drainage f e a t u r e i n the f r o n t i s p i e c e i s approximately 10 m a c r o s s ) . We have estimated our o v e r a l l plan accuracy a t b e t t e r than 50 m f o r accepted data. 2.3 RESULTS The p r o f i l e of the Rusty G l a c i e r presented i n F i g u r e s 2.3 and 2.4, except f o r c r o s s i n g the terminus of the Backe G l a c i e r at the lower end, f o l l o w s the c e n t r e l i n e of survey markers down 18 Table 2.2 Compass E r r o r s T y p i c a l Maximum To Be Ex p l a i n e d .12° A i r c r a f t D e v i a t i o n 2° 5° Introduced D e v i a t i o n * 5° Rosette E r r o r 3° C a r t e s i a n E r r o r 4° D i s t o r t i o n E r r o r 1" Reading E r r o r 5° * T e s t s f o r t h i s value were performed i n Vancouver, Canada. The survey area was much f u r t h e r n o r t h , p o s s i b l y w i t h i n the area of compass u n r e l i a b i l i t y . The a c t u a l value thus may be l a r g e r . . the g l a c i e r . The p r o f i l e i s i n e x c e l l e n t agreement with an e a r l i e r survey made by man-hauling the DOEC system (Clarke and Goodman, 1975). For ready comparison with t h i s work we have taken 176 m u s - 1 as the v e l o c i t y o f e l e c t r o m a g n e t i c waves i n i c e . At the t e n l o c a t i o n s where d i r e c t comparison i s p o s s i b l e seven of the measured i c e depths agree wit h i n the r e s o l u t i o n of the system. The remaining t h r e e d i s c r e p a n c i e s , a l l l e s s than 10 m, have been a t t r i b u t e d t o a d e v i a t i o n o f the f l i g h t path near the headwall, or to d i f f i c u l t i e s of i n t e r p r e t a t i o n of ground survey data. I t i s a l s o p o s s i b l e t h a t the a i r b o r n e system c o u l d y i e l d data imp l y i n g shallower i c e , s i n c e i t i l l u m i n a t e s a l a r g e r area of the bedrock. The Rusty G l a c i e r p r o f i l e demonstrates s e v e r a l f e a t u r e s o f the echo sounder. R e s o l u t i o n (about 4 m or one-tenth of a 19 g r a t i c u l e d i v i s i o n ) i s c u r r e n t l y l i m i t e d by the photographic r e c o r d i n g scheme. The averaging e f f e c t o f the photographic f i l m suppresses s c a t t e r i n g r e t u r n s s i n c e each g r a i n i s exposed by the accumulated output o f over 1000 t r a n s m i t t e r p u l s e s . Data f o r the i c e t h i c k n e s s map o f Trapridge G l a c i e r ( F i g . 2.5) were compiled from three of the f o u r f l i g h t s made d u r i n g the two days, r e s u l t i n g i n more e x t e n s i v e coverage than on the Busty G l a c i e r . The Trapridge G l a c i e r a l s o has an array of survey markers u s e f u l d u r i n g the f l i g h t s as v i s u a l n a v i g a t i o n a i d s . Again, where i t i s p o s s i b l e to compare the a i r b o r n e i c e t h i c k n e s s measurements with those made from the s u r f a c e with the DOEC system (Goodman and o t h e r s , 1975) , agreement i s very good, w i t h i n the r e s o l u t i o n l i m i t of the present a i r b o r n e system. There are a number of f e a t u r e s i n the new i c e t h i c k n e s s map t h a t were not i n d i c a t e d by the ground survey data. A shallow r i b extends from the northern edge, about h a l f way up the g l a c i e r , a c r o s s the g l a c i e r towards an i c e f a l l . T h i s zone of shallow i c e may s p l i t the g l a c i e r i n t o two separate dynamic zones. The major rock r i d g e which s p l i t s the terminus extends under the i c e about o n e - t h i r d of the -way up the g l a c i e r . A b a s i n of i c e has been found between the . two rock spurs near the ce n t r e of the headwall. The new f e a t u r e s are c o n s i s t e n t with the ground survey O v e r l e a f : F i g u r e 2.5. Trapridge G l a c i e r i c e t h i c k n e s s map.. The contours are computer generated by i n t e r p o l a t i n g from the a i r b o r n e data onto an a r b i t r a r y square g r i d . The i n t e r p o l a t i o n uses an inverse^-distance-squared weighted average, of the n e a r e s t datum i n each of e i g h t egual s e c t o r s . In re g i o n s of low d e n s i t y coverage and p a r t i c u l a r l y near the southwest headwall, the map r e f l e c t s the a r b i t r a r y nature of the i n t e r p o l a t i o n scheme. 20 21 data and are r e s u l t s of the more e x t e n s i v e coverage of our a i r b o r n e programme. The most s e r i o u s l i m i t a t i o n of the sounder i s i t s i n a b i l i t y to p e n e t r a t e great t h i c k n e s s e s of temperate or d e b r i s - r i c h i c e . We b e l i e v e the i c e t h i c k n e s s map of Hazard G l a c i e r ( F i g . 2.6) owes much of i t s c h a r a c t e r to an i n t e r n a l moraine l a y e r formed by the merging of the g l a c i e r ' s two main t r i b u t a r i e s . The map shows, along the northern edge of the g l a c i e r , a shallow ledge of r e l a t i v e l y c onstant (60-80 m) i c e depth. The boundary of the ledge i s d e f i n e d by a tortuous 80 m i c e depth contour. We do not b e l i e v e t h a t i n t h i s r e g i o n we have a c t u a l l y measured t o t a l i c e depth. More l i k e l y the r a d i a t i o n has been s c a t t e r e d by the i n t e r n a l moraine l a y e r . The evidence f o r an i n t e r n a l r e f l e c t o r i s t w o - f o l d . Each t r a n s v e r s e f l i g h t l i n e y i e l d e d data showing an extremely steep r i s e from the "deeper" southern r e g i o n o f the g l a c i e r to the northern ledge ( F i g . 2.7). These very s t r o n g boundary p o i n t s do O v e r l e a f : F i g u r e 2.6. Hazard G l a c i e r i c e t h i c k n e s s map. The contour i n t e r v a l i s 20 m. The major medial moraine i s shown as a shaded area. Second o v e r l e a f : F i g u r e 2.7. A t r a n s v e r s e s e c t i o n of the Hazard G l a c i e r showing the i n t e r p r e t a t i o n and a r e p r o d u c t i o n of the data. The c r o s s - s e c t i o n i s shown l o o k i n g u p - g l a c i e r , with the northern boundary to the r i g h t . The s o l i d l i n e r e p r e s e n t s the f i r s t i n t e r p r e t a t i o n of the data.. The f l i g h t l i n e shown on F i g u r e 2.6, went from the northern boundary to the southern boundary. The steep r i s e c o i n c i d e s with the edge of the major medial moraine. The shallow ledge d e p i c t e d by the s o l i d l i n e above a shaded band i s probably.not bedrock but a d e b r i s l a y e r , perhaps brought with o v e r l a i n i c e from the northern arm of the g l a c i e r . The dashed l i n e r e p r e s e n t s a h y p o t h e t i c a l bedrock s u r f a c e .  23 24 not d e f i n e a smooth v a l l e y f l o o r . Instead they cause the tor t u o u s 80 m contour i n F i g u r e 2.6. We b e l i e v e that the r i s e s are too ste e p f o r a reasonable v a l l e y c o n f i g u r a t i o n and t h a t the i r r e g u l a r c ontours r e s u l t from the o c c a s i o n a l p e n e t r a t i o n of the r a d i a t i o n through the i n t e r n a l l a y e r . Secondly, the edge of the shallow i c e depths c o i n c i d e s with the major surface medial moraine. The s t r u c t u r e which has caused the formation of the medial moraine could a l s o have caused the formation of an i n t e r n a l moraine l a y e r which t e r m i n a t e s i n the v i c i n i t y of the medial moraine. P o s s i b l y i c e from the northern arm has ov e r r i d d e n i c e which o r i g i n a t e d at the southern headwall (Sharp, 1960, p. 13). 2.4 CONCLUDING REMARKS TO AIRBORNE SURVEYS Our f i e l d t e s t s demonstrate t h a t a i r b o r n e UHF echo sounders can be used to measure the i c e t h i c k n e s s of s m a l l and medium- s i z e d c o l d v a l l e y g l a c i e r s . The compact s i z e of the antenna and instruments makes them e a s i l y deployable from even the s m a l l e s t a i r c r a f t . Using a small h e l i c o p t e r , complete i c e t h i c k n e s s data can be c o l l e c t e d g u i c k l y and e f f i c i e n t l y . The deepest i c e encountered was 200 m on Hazard G l a c i e r , though t h i s i s not the d e p t h . l i m i t of our sounder. During an a i r b o r n e survey of the g l a c i e r ,. l y i n g i n , the northwest c o l . of l i t . Logan, Yukon T e r r i t o r y , we sounded 430 m of ice. under . c o n d i t i o n s t h a t were f a r from i d e a l (Clarke and Narod, unpublished). The major drawback o f UHF .echo sounders i s t h e i r i n a b i l i t y t o p e n e t r a t e temperate or d i r t y i c e . .-• S e v e r a l improvements to the sounder are now being 25 undertaken: these i n c l u d e the o r g a n i z a t i o n of the radar i n t o a s i n g l e rack-mounted package f o r e a s i e r a i r b o r n e deployment, i n c r e a s e d p r e - a m p l i f i c a t i o n f o r improved system performance, a d d i t i o n o f a g r a p h i c d i s p l a y f o r monitoring and f i e l d r e p l a y , a magnetic r e c o r d e r f o r d i g i t a l or analogue data, and d i r e c t r e c o r d i n g n a v i g a t i o n a i d s . 26 CHAPTER 3: PHYSICAL PROPERTIES OF GLACIERS 3.1 EXPERIMENTAL DESCRIPTION The experiments performed with the UBC sounder at our Hazard G l a c i e r f i e l d camp ( d r i l l s i t e #1) were designed to measure e l l i p s e s of p o l a r i z a t i o n of r e f l e c t e d power, and to gather s t a t i s t i c a l data on r e f l e c t i o n s t r e n g t h s . The data d i s c u s s e d here are the products of two experiments which have f o r convenience been l a b e l l e d experiment TX.O and experiment TX.9. The p h y s i c a l e x e c u t i o n of the experiments i n v o l v e d the r o t a t i o n of a r e c e i v e r antenna about the v e r t i c a l a x i s , while a t r a n s m i t t e r antenna was l e f t s t a t i o n a r y . For TX.O the E - v e c t o r of the t r a n s m i t t e r antenna was a l i g n e d approximately p a r a l l e l to the flow a x i s of the g l a c i e r . For TX.9 t h e E-vector of the t r a n s m i t t e r was a l i g n e d at a r i g h t angle t o the TX.O o r i e n t a t i o n , approximately p e r p e n d i c u l a r t o the flow a x i s of the g l a c i e r ( F i g . 3.1). Two high-gain corner r e f l e c t o r antennae (App. 1.5) were used f o r these experiments. Because o f t h e i r s m a l l s i z e we were able t o mount the antennae on r o t a t i n g p l a t f o r m s , l e v e l l e d approximately 60 cm above the i c e s u r f a c e . For each experiment we r e c o r d e d 36 echograms, taken a t 10<> increments of the r e c e i v e r antenna azimuth. We made a t o t a l of 72 r e c o r d s by photographing an A-scope (X-Y) o s c i l l o s c o p e d i s p l a y on P o l a r o i d f i l m . 27 We then d i g i t i z e d these r e c o r d s on a "Gradicon" f l a t b e d d i g i t i z e r . T h i s d i g i t i z e r has a p r e c i s i o n of 0.001" (0.025 mm). The d i g i t a l r e c o r ds were n u m e r i c a l l y i n t e r p o l a t e d to 10 ns increments, and c o r r e c t e d f o r t r a c e r o t a t i o n on the. f l a t b e d d i g i t i z e r . A f i n a l time base c o r r e c t i o n brought the l e a d i n g edges of the t r a n s m i t t e d pulses i n t o alignment ( F i g s . 3.2 and 3.3) . 3.2 DATA ANALYSIS The i n t e n t o f the two experiments was to e s t a b l i s h a q u a s i - s t a t i o n a r y EM f i e l d with the s t a t i o n a r y t r a n s m i t t e r antenna, and then to use the r e c e i v e r antenna as an analyser o f the r e f l e c t e d f i e l d . I f the r e t u r n i n g power were l i n e a r l y p o l a r i z e d we should expect to d e t e c t a c o s 2 v a r i a t i o n of power with azimuth. The t w o - f o l d symmetry of the r e c e i v e r antenna p a t t e r n i m p l i e s t h a t we should expect always t o have a two-fold symmetry i n the r e t u r n e d power vs. azimuth. Nonpolarized r e t u r n i n g power should r e s u l t i n the measurement of a c i r c u l a r power d i s t r i b u t i o n . Our data show l i t t l e evidence f o r any of these e f f e c t s . 28 3.2.1 EBBOES IN POWEB MEA SUREMENTS PROCESSING ERRORS The p h o t o g r a p h i c / d i g i t i z i n g procedure i n t r o d u c e s e r r o r s which c o u l d have been avoided had a more s o p h i s t i c a t e d r e c o r d i n g medium been e a s i l y a v a i l a b l e . Due t o cathode ray tube w r i t i n g speeds the photographic process cannot d e l i v e r uniform image d e n s i t y (brightness) along the t r a c e . Together with the f i n i t e width of the o s c i l l o s c o p e t r a c e , t h i s can r e s u l t i n s u b s t a n t i a l timing/power e r r o r s s i n c e the user must v i s u a l l y s e l e c t v a l i d p o i n t s along the t r a c e . In our case an o p t i m a l l y sharp t r a c e had a width cor r e s p o n d i n g to approximately 100 ns or 1.5 dB. The d i g i t i z i n g process can a l s o c o n t r i b u t e t o timing/power e r r o r s . A p r e c i s i o n i n our case of 0.001" (0.025 mm) corresponds to 2.5 ns or 0.04 dB, and i s hence not a s i g n i f i c a n t e r r o r source. However user i m p r e c i s i o n and f a t i g u e c o u l d i n t r o d u c e e r r o r s many times l a r g e r . We kept s e s s i o n s a t the d i g i t i z e r to l e s s than 1 hour to minimize t h i s problem. Time base c o r r e c t i o n values were taken from p o i n t s sampled O v e r l e a f : F i g u r e 3.1. Schematic of the plan views of the antenna r o t a t i o n experiments. Second o v e r l e a f : F i g u r e 3.2 the 36 records f o r experiment TX.O. The numbers to the l e f t of each r e c o r d , i n d i c a t e the r e c e i v e r azimuth i n degrees. T h i r d o v e r l e a f : F i g u r e 3.3. The 36 re c o r d s of experiment TX.9. 29 FIG. 3.1 SCHEMATIC OF ANTENNA ROTATION EXPERIMENTS, PLAN VIEW FIG. 3.2 CORRECTED RECORDS OF EXPERIMENT "TX.O"  32 along the l e a d i n g edge of the o s c i l l o s c o p e t r a c e ; these were the only s h a r p l y v i s i b l e edges on a l l of the r e c o r d s . However because o f v a r i a t i o n s i n the s t r e n g t h of the d i r e c t a r r i v a l power, t h i s c o r r e c t i o n i s not l i k e l y to have improved the gross t i m i n g accuracy to b e t t e r than 20 ns, nor has i t a f f e c t e d random measurement e r r o r s w i t h i n the t r a c e s . F i n a l l y , a f t e r c o r r e c t i o n , t r a c e r o t a t i o n was not c o n s i d e r e d to be a s i g n i f i c a n t e r r o r source* SYSTEM INDUCED EBBOBS Three a d d i t i o n a l e f f e c t s , each caused by the g l a c i e r not being an i d e a l h a l f - s p a c e , r e s u l t i n r e c e i v e d power v a r y i n g with antenna p o s i t i o n . Two of these e f f e c t s , i n v o l v i n g the i n t e r a c t i o n of the antenna with m a t e r i a l s i n i t s near f i e l d , are changes i n the antenna's e f f e c t i v e impedance and gain p a t t e r n . Impedance changes r e s u l t i n mismatches with t he. antenna feed l i n e and f l u c t u a t i o n s i n power fed to the r e c e i v e r . V a r i a t i o n s i n the antenna p a t t e r n , caused by r e f r a c t i o n at random v a r i a t i o n s i n the i c e / a i r s u r f a c e , r e d i s t r i b u t e the r e c e i v e d power. I t i s w e l l known t h a t roughness can cause bedrock echoes to vary s i g n i f i c a n t l y with s m a l l antenna movements (Nye, and o t h e r s , 1972). I c e / a i r s u r f a c e roughness could cause a s i m i l a r e f f e c t . With a 36 cm wavelength, roughness on the s c a l e of 36 cm c o u l d i n f l u e n c e the antenna p a t t e r n . F i n a l l y , having an e l l i p t i c a l beam (approximately 18° x 44° semi-axes) guarantees t h a t the r e c e i v e r antenna "sees" d i f f e r e n t s c a t t e r e r s as the 33 antenna i s r o t a t e d , i n t r o d u c i n g more v a r i a t i o n i n the r e c e i v e d power. Our data e x h i b i t l a r g e v a r i a t i o n s , from r e c o r d to r e c o r d , of t o t a l r e c e i v e d power. We estimated these v a r i a t i o n s as f o l l o w s . By t a k i n g the average over the 36 r e c o r d s of power vs. time ( F i g . 3.4A) we noted t h a t the power r e t u r n i n g between 0.5 us and 1.5 us f a l l s o f f roughly as 1/R2 - 5 dB/100 m. We then c a l c u l a t e d the average power i n each r e c o r d , between 0.5 us and 1.5 us, using the 1/R2 - 5 dB/100 m curve as a weighting f u n c t i o n t o f l a t t e n the records. The r e s u l t s are p l o t t e d as a f u n c t i o n o f azimuth on a l i n e a r p l o t ( F i g . 3.5) and a l o g p l o t ( F i g . 3.6). The a l g o r i t h m d e s c r i b e d above i s t o some extent a r b i t r a r y . However, t h e r e are f e a t u r e s i n F i g s . 3.5 and 3.6 which would c e r t a i n l y occur with any e s t i m a t o r . One i s the very l a r g e d i f f e r e n c e between the s t r o n g e s t and weakest r e t u r n s w i t h i n one experiment. In both experiments the d i f f e r e n c e exceeds 25 dB. Another f e a t u r e i s the apparent randomness of the estimated power. At s e v e r a l l o c a t i o n s jumps i n power exceeding ±10 dB occur between adjacent antenna p o s i t i o n s . I f these v a r i a t i o n s have been caused by e f f e c t s other than O v e r l e a f : F i g u r e 3.4. Averages of power vs. time. These r e c o r d s are the averages of the 36 i n d i v i d u a l r e c o r d s of each experiment. In 3.4A the o r i g i n a l data have been averaged. In 3.4B each i n d i v i d u a l record has been s c a l e d up or down t o an average l e v e l by s u b t r a c t i n g the r e l a t i v e power f i g u r e p l o t t e d i n F i g 3.6. We have c a l l e d t h i s process "azimuthal smoothing". Superimposed on each r e c o r d i s a curve which r e p r e s e n t s a 1/R2 - 5 dB/100 m f a l l - o f f of power with depth. RELATIVE POWER (10dB/DIV) RELATIVE POWER (10 dB/DIV) 7C RELATIVE POWER RELATIVE POWER (5dB/DIV.) 37 the random i n t e r a c t i o n between the antenna and the i c e / a i r s u r f a c e we should expect to see a two-fold symmetry i n the azimuthal f u n c t i o n s of power. Examination of the d i s c r e t e F o u r i e r s p e c t r a ( F i g . 3.7) of the r e l a t i v e power r e v e a l s t h a t there i s no tendency f o r the even harmonic terms to dominate, and thus t h a t these v a r i a t i o n s are not caused by bulk p r o p e r t i e s of the g l a c i a l i c e mass. E l l i p t i c i t y of p o l a r i z a t i o n should a l s o be estimated by e x t r a c t i n g even harmonics from azimuthal power f u n c t i o n s . The magnitudes of these a d d i t i o n a l random v a r i a t i o n s i n our data thus precl u d e measurement o f e l l i p t i c i t y of p o l a r i z a t i o n , and the d e t e c t i o n of b i r e f r i n g e n c e . 3.2.2 DIELECTRIC ATTENUATION The 72 r e c o r d s of experiments TX.O and TX.9 provide a b a s i s f o r e s t i m a t i n g the d i e l e c t r i c l o s s e s i n the g l a c i e r i c e . The averages of the records have been p l o t t e d i n F i g 3.4A. To estimate the e f f e c t of the l a r g e random v a r i a t i o n s d i s c u s s e d i n Sec. 3.2 .1 , we have a l s o averaged the r e c o r d s a f t e r having s c a l e d each r e c o r d to c o r r e c t f o r these l a r g e v a r i a t i o n s . T h i s was done by s u b t r a c t i n g the r e l a t i v e power f i g u r e p l o t t e d i n F i g . 3.6 from i t s r e s p e c t i v e r e c o r d , and adding the average power f i g u r e from F i g . 3.6 t o a l l the re c o r d s . In t h i s way the power e s t i m a t i n g - a l g o r i t h m d e s c r i b e d i n the p r e v i o u s s u b s e c t i o n would always y i e l d a r e l a t i v e power f i g u r e equal to the average power f i g u r e . This procedure, which we have c a l l e d azimuthal smoothing, changes the peak power r e f l e c t e d at the bedrock by ±1 dB. We can conclude from t h i s s m a l l d e v i a t i o n t h a t the l a r g e °(1112) * (843) FIG. 3.7 HARMONIC NUMBER DISCRETE FOURIER SPECTRA OF AZIMUTHAL POWER 39 record to r e c o r d v a r i a t i o n s do not a d v e r s e l y a f f e c t our a b i l i t y t o measure an average bedrock r e f l e c t i o n power. Table 3.1. D i e l e c t r i c Loss Computation Transmitted power + 66 dBm Received power -32 •dBm 98 dB Geometric l o s s e s a t 158m -81 dB System l o s s e s -14 dB Bedrock r e f l e c t i v i t y -20 dB Two-way antenna gain + 31 dB D i e l e c t r i c l o s s e s -14 dB- -98 dB The measured bedrock echo s t r e n g t h , determined from F i g . 3.4, i s -32 dBm. To compute the d i e l e c t r i c l o s s e s from one datum r e q u i r e s t h a t we assume a value f o r the bedrock r e f l e c t i v i t y . A commonly used value i s -20 dB (Davis, unpublished). The echo delay i s 1.85 us corresponding t o an i c e depth, with c a b l e l e n g t h c o r r e c t i o n s , of 158 m. These two f i g u r e s r e g u i r e t h a t the t o t a l d i e l e c t r i c l o s s e s be 14 dB, y i e l d i n g l o s s r a t e s of 4.5 dB/100m or ftanS = 0.26. 1 t a b l e 3.1 summarizes the d i e l e c t r i c l o s s c a l c u l a t i o n . *We must be aware t h a t the bedrock r e f l e c t i v i t y value of -20 dB r e p r e s e n t s a s i m p l i f i c a t i o n of the combined d i e l e c t r i c c o n t r a s t and s u r f a c e roughness e f f e c t s , and was s e l e c t e d to account f o r r a d i o echo sounder behaviour' at VH f r e q u e n c i e s . To use t h i s f i g u r e here we must assume t h a t t h i s simple d e s c r i p t i o n o f bedrock behaviour can be extended, unchanged, t o UH f r e q u e n c i e s . T h i s i s not n e c e s s a r i l y the case s i n c e f e a t u r e s such as water f i l m s may have s u b s t a n t i a l e f f e c t s a t the hiqher f r e q u e n c i e s . Nonetheless s i n c e we have no other estimate we s h a l l use t h i s f i g u r e . 40 The mean i c e temperature of Hazard G l a c i e r at the experiment s i t e i s known ( F i g . 3.8) to be about -5°C ( C l a r k e , p r i v a t e communication). The value of f tan 8 = 0.26 a t -5°C agrees very w e l l with measurements of Westphal (Evans, 1965). 3.2.3 SCATTERED POWER DENSITY VS. DEPTH Given from the pr e v i o u s s u b s e c t i o n t h a t the two-way d i e l e c t r i c l o s s e s are about 9 dB/100 m, we may now i n f e r from F i g . 3.4 t h a t a t Hazard G l a c i e r d r i l l s i t e #1 the s c a t t e r i n g c o e f f i c i e n t , C, as de f i n e d by Davis (unpublished, p. 64, eq"n 5(1)) i n c r e a s e s with depth. (3.1) where Pg i s the s c a t t e r e d power per u n i t volume and P i s the i n c i d e n t power d e n s i t y . A con s t a n t C and d i e l e c t r i c l o s s e s of 9 dB/100 m r e q u i r e s t h a t r e c e i v e d power s c a t t e r e d from a s h e l l of r a d i u s R, f a l l o f f with R as 1/R2 - 9 dB/100m (Davis, unpublished, p. 66, eq'n 5 ( 3 ) ) . Since the a c t u a l s c a t t e r e d power i s best f i t t e d by a 5dB/100m l o s s curve, ( F i q . 3.9) we conclude t h a t the s c a t t e r i n g c o e f f i c i e n t i n c r e a s e s with depth. The i m p l i c a t i o n of t h i s r e s u l t i s t h a t the s i z e and/or d e n s i t y of s c a t t e r e r s (presumably rock d e b r i s , water c a v i t i e s , conduits) i n c r e a s e s with depth. FIG. 3.8 THERMAL REGIME OF HAZARD GLACIER DRILL SITE 1 • 76T1 x76T2 o 76T8 ! • • I I i-Z 1 1 I 8 -6 -U -2 0 TEMPERATURE ( °C ) > Q \ CD O or L U o Q_ U J > L U or TX.O AVERAGE AFTER PRESCALING 5dB/100m FALLOFF 9dB/100m FALLOFF 0 0.5 1.0 1.5 DELAY TIME (psec) 2.0 FIG. 3.9 COMPARISON OF DIELECTRIC LOSS AND SCATTERED POWER 43 3.3 DETECTION OF LARGE CONDUIT SCATTERERS A f u r t h e r examination of F i g . 3.4 r e v e a l s t h a t at a time delay of 1.5 us the average re c o r d of TX.O e x h i b i t s a s t r o n g peak 5 dB above the l o c a l time average. T h i s peak i s not e v i d e n t i n the average re c o r d of TX.9. T h i s s e c t i o n examines the p o s s i b i l i t y o f u s i n g high r e s o l u t i o n UHF r a d i o echo sounding to i d e n t i f y l a r g e c o n d u i t or " l i n e a r " s c a t t e r e r s , and f u r t h e r , d i s c u s s e s the p o s s i b i l i t y t h a t data at time delay 1.5 us might repr e s e n t such a s c a t t e r e r . 3.3.1 THEORETICAL PATTERNS FOR CONDUIT SCATTERERS We have taken the approach t h a t l i n e a r s c a t t e r i n g o b j e c t s generate s i g n a t u r e p a t t e r n s , i . e . the p a t t e r n of data produced by a l i n e a r s c a t t e r e r , present i n the range of an antenna r o t a t i o n experiment, may somehow be i d e n t i f i e d with the s c a t t e r i n g o b j e c t . By modelling the s c a t t e r e r as a h o r i z o n t a l f l a t r i b b o n (Appendix 3) the r a t i o of power r e c e i v e d from the s c a t t e r e r , t o the t o t a l t r a n s m i t t e d power max be estimated by + ~7F I J (P/8) exp(-i^-P)| (3.2, c f . A3.59) 44 where (see F i g - A3. 1) W i s the width of the s c a t t e r e r , Xi i s the s c a t t e r e r depth, G i s the antenna g a i n f u n c t i o n , /3 i s the angle of n e a r e s t approach (angle of i n c i d e n c e ) , and J, d e f i n e d by eq'n A3.37, i s antenna p a t t e r n dependent. a T and a R are the r e s p e c t i v e azimuths of the tr a n s m i t and r e c e i v e antennae r e l a t i v e t o the s c a t t e r e r normal. The approximation i s v a l i d i f Wsin/3<<1. For the near v e r t i c a l angle of i n c i d e n c e r e q u i r e d by our h i g h - g a i n antennae, W may be s e v e r a l wavelengths. In our case, widths up to 1 m may be reasonably modelled. Equation 3.2 comprises two p a r t s . The f i r s t term i s the e v a l u a t i o n of the i n t e g r a l over a removable s i n g u l a r i t y , and i s dependent only on the gain o f the antennae toward the F i r s t and second o v e r l e a v e s : F i g u r e 3. 10. T h e o r e t i c a l antenna r o t a t i o n p a t t e r n s f o r the U.B.C. high-gain c o r n e r r e f l e c t o r antennae. The two r o s e t t e s model r e s p e c t i v e l y experiments TX.O and TX.9. In each r o s e t t e there are two curves. The outer dashed curve p l o t s the r e l a t i v e power c a l c u l a t e d using the numerical scheme d e f i n e d i n Appendix 3. These values have been normalized to the maximum value f o r the two model experiments. The i n n e r shaded curve, always two p e t a l s , i s the product of the value o f the f i r s t curve with e i t h e r c o s 2 # or s i n 2 ^ . The second curves show the expected p a t t e r n s i f the b a c k s c a t t e r e d r a d i a t i o n has the i d e n t i c a l p o l a r i z a t i o n t o the i n c i d e n t p o l a r i z a t i o n . Here we have assumed t h a t no d e p o l a r i z a t i o n or p o l a r i z a t i o n r o t a t i o n has occurred. Superimposed on each r o s e t t e i s a schematic r e p r e s e n t a t i o n of the s c a t t e r e r p o s i t i o n . The heavy l i n e r e p r e s e n t s the s c a t t e r e r , o r i e n t e d at angle a (see F i g . A3 . 1 ) , d i s p l a c e d by angle ,/3 o f f of the v e r t i c a l . F u l l s c a l e displacement r e p r e s e n t s 4 5 0 o f f v e r t i c a l . The l a r g e dynamic range a t P =20° i s due t o a st r o n g n u l l i n the antenna E-plane at about 2 0 ° . T h i r d and f o u r t h o v e r l e a v e s : F i g u r e 3 . 1 1 . T h e o r e t i c a l antenna r o t a t i o n p a t t e r n s f o r d i p o l e antennae. See d e s c r i p t i o n of F i g . 3. 10. 45 270 FIG. 3.10 SAMPLE THEORETICAL ANTENNA ROTATION PATTERNS FOR CORNER REFLECTOR ANTENNAE 46 270 270 180 a \ 0 TX.O 0 XI 2 7 0 r $ A X 0 90 L 180 = 45 olTX.9 270 FIG. 3.10 CONT. FIG. 3.11 SAMPLE THEORETICAL ANTENNA ROTATION PATTERNS FOR DIPOLE A N T E N N A E 48 FIG. 3.11 CONT. 49 s c a t t e r e r ' s nearest p o i n t G ( / 8 , c t ) . The second term e v a l u a t e s T,K the r e s i d u a l d i f f e r e n c e between the removable s i n g u l a r i t y and the g a i n dependent i n t e g r a l . Using the numerical scheme e s t a b l i s h e d i n Appendix 3 we have evaluated the continuous wave r e t u r n i n g power pa t t e r n from s e v e r a l s c a t t e r e r p o s i t i o n s , m o d e l l i n g both our hi g h - g a i n corner r e f l e c t o r antennae, and s i n g l e half-wave d i p o l e antennae ( F i g s . 3.10 and 3.11). In a l l cases we have found t h a t the pole c o n t r i b u t i o n t o the i n t e g r a l i s at l e a s t two orders of magnitude l a r g e r than the r e s i d u a l c o n t r i b u t i o n , even when the i n t e g r a t i o n extends 9 t o we l l beyond 45<>. We can then n e g l e c t the r e s i d u a l component, and c o n s i d e r the pole term alone t o rep r e s e n t the e n t i r e i n t e g r a l JL ± L-p^J = 8^X7* • 6 ( ^ , a T ) G . O , a H ) C 0 S ^ [ J ( 3 . 3 ) Since the only a. and (B dependence now occurs i n the f a c t o r G ( p, dj ) G ( yS , a R ) , the shape of the patte r n i s i n d i s t i n g u i s h a b l e from t h a t of a p o i n t s c a t t e r e r l o c a t e d at the L o r i g i n . , Hence, the shape o f the p a t t e r n alone cannot be used to i d e n t i f y l i n e s c a t t e r e r s . Eguation 3.3 may be r e w r i t t e n 50 i n d i c a t i n g t h a t b a c k s c a t t e r e d power f a l l o f f as B~ 3. A plane r e f l e c t o r b a c k s c a t t e r s power as E - 2 . A p o i n t s c a t t e r e r b a c k s c a t t e r s power as B~*. As determined above, a l a r g e l i n e a r s c a t t e r e r cannot be i d e n t i f i e d by data c o l l e c t e d from a s i n g l e l o c a t i o n . A p o s i t i v e i d e n t i f i c a t i o n would r e q u i r e the l o c a t i n g of the s c a t t e r e r from s e v e r a l radar s i t e s and f i t t i n g the b a c k s c a t t e r e d power t o the fi-3 curve. F i r s t and second o v e r l e a v e s : F i g u r e 3.12. TX.O antenna r o t a t i o n data s e l e c t e d a t v a r i o u s delay times. The f i r s t eleven p l o t s have been s e l e c t e d at 100 ns i n t e r v a l s , i n the range 0.7 us to 1.7 us. The l a s t nine p l o t s have been s e l e c t e d a t 20 ns i n t e r v a l s i n a range c o v e r i n g the l e a d i n g edge. of the bedrock echo at 1-8 us. Each r o s e t t e has been normalized to the maximum val u e of the data used i n the r o s e t t e and p l o t t e d on a l i n e a r s c a l e . To the r i g h t of each r o s e t t e a bar graph d i s p l a y s r e l e v a n t power data. The bar graph i s l o g a r i t h m i c with the f u l l s c a l e r e p r e s e n t i n g 80 dB. The top o f the dark band i n the l e f t column i n d i c a t e s the l e v e l of the 1/E 2 - 5dB/100m e s t i m a t o r d e s c r i b e d i n S e c t i o n 3.2. The top and bottom of the dark band i n the r i g h t column mark the maximum and minimum power p l o t t e d i n the corresponding r o s e t t e . As the delay time passes i n t o the bedrock echo the power l e v e l can c l e a r l y be seen to r i s e w e l l above the s c a t t e r e d power e s t i m a t o r . T h i r d and f o u r t h o v e r l e a v e s : F i g u r e 3.13. TX.9 antenna r o t a t i o n data. S i m i l a r t o F i g . 3.12. F i f t h and s i x t h o v e r l e a v e s : F i g u r e 3.14. TX.O antenna r o t a t i o n data a f t e r azimuthal smoothing. The r a t i o of the maximum to minimum power (the l e n g t h of the dark band i n the r i g h t column of the bar graphs) are g e n e r a l l y s m a l l e r than those of the unsmoothed data s u g g e s t i n g t h a t azimuthal smoothing has tended t o remove l a r g e - s c a l e , e x t e r n a l l y caused e f f e c t s . The s p i k e y appearance at the delay times 1.80 us to 1.84 us can r e s u l t from two causes - a s e v e r e l y d i f f e r e n t bedrock s c a t t e r i n g regime, o r , more l i k e l y , t i m i n g e r r o r s . Seventh and e i g h t h o v e r l e a v e s : F i g u r e 3.15. S e l e c t e d TX.9 antenna r o t a t i o n data a f t e r a z i m u t h a l smoothing. See F i g . 3.14. T=0.800 uSEC FIG. 3.12 S A M P L E D A N T E N N A ROTATION DATA FROM " T X . O " FIG. 3 12 CONT. 53 T=0.700 uSEC 270 0 T=0.900 jiSEC 270/ j 1 9 0 180 0 T= 1.200 uSEC 270/ ' C 1 90 180 0|T=1.500nSEC 0 T=0.800 M S E C 270/ \ ]90 180 0 T= 1.000 USEC 270/ ^^~~> 1 9 0 180 270/ 0 T= 1.300 uSEC I 1 90 3 ^ I 180 270/ 0 T= 1.600 uSEC 1 9 0 180 0 T=1.100 uSEC 270/ 190 180 0|T=1.400 uSEC FIG. 3.13 S A M P L E D A N T E N N A ROTATION DATA FROM " T X . 9 " T= 1.760 uSEC FIG. 3.13 CONT. T=0.800 uSEC FIG. 3 .U S A M P L E D A N T E N N A ROTATION DATA FROM " T X . O " , A F T E R AZ IMUTHAL SMOOTHING 56 180 FIG. 3 .U CONT. 57 0 T=0.700uSEC 270 / > 1 90 180 0 T=0.900uSEC 270/ ( I 90 180 0 T= 1-500 uSEC no I J 180 0 T=0.800 uSEC 270 / \ \ 1 90 180 270/ 0 T= 1.000 uSEC 90 1 — < - m . o J 180 0 T= 1.100 uSEC 270/ V / 1 9 0 180 0 T= 1.300 uSEC 270/ 5V 180 270 0 T= 1.400 uSEC C 1 90 180 r 270/ 0 T=1.600MSEC < ^ 1 9 0 180 0|T=1.700nSEC FIG. 3.15 S A M P L E D A N T E N N A ROTATION DATA FROM "TX .9 " , A F T E R AZIMUTHAL SMOOTHING FIG. 3.15 CONT. 59 3.3.2 COMPARISONS WITH THE FIELD EXPERIMENTS F i g s . 3.12 through 3.15 are s e l e c t i o n s of r o s e t t e p l o t s of the two antenna r o t a t i o n experiments, p l o t t i n g r e c e i v e d power vs. azimuth, with delay time as a parameter. These p l o t s p rovide l i t t l e evidence f o r the expected two-fold symmetry, even a f t e r azimuthal smoothing ( F i g s . 3.14 and 3.15). The r o s e t t e s p l o t t e d from the smoothed data ( F i g s . 3.14 and 3.15) a t delay time 1.50 us are the only p a t t e r n s of t h e s e l e c t e d data which resemble two-fold symmetrical p e t a l p a t t e r n s . However, they s t i l l do not compare w e l l with any t h e o r e t i c a l p a t t e r n s t h a t we have generated using an i d e a l i z e d c o r ner r e f l e c t o r model. To achieve even the l e a s t match a l s o r e q u i r e s t h at we invoke some mechanism which r o t a t e s the p o l a r i z a t i o n by about 90° s i n c e TX.O t h e o r e t i c a l l y r e c e i v e s i t s g r e a t e s t power at 0<> and TX.9 at 90°. When we c o n s i d e r the data r e g a r d i n g the very low p r o b a b i l i t y of observing any t w o - f o l d symmetry, the appearance of symmetry a t delay time 1.50 us i s most l i k e l y f o r t u i t o u s . 3.4 CONCLUDING REMARKS TO CHAPTER 3 These f i e l d t e s t s and d i s c u s s i o n s have demonstrated t h e d i f f i c u l t i e s a s s o c i a t e d with the use of UHF echo sounders f o r determining p h y s i c a l p r o p e r t i e s of g l a c i e r s . Measurements of a t t e n u a t i o n , b i r e f r i n g e n c e or other parameters r e q u i r e a c a p a b i l i t y f o r the a c c u r a t e r e c o r d i n g and r e p r o d u c t i o n of power vs. time data. Records c o l l e c t e d by photographing A-scope d i s p l a y s have f a i l e d to provide the accuracy r e q u i r e d f o r these 60 experiments. More important, random roughness a t the i c e / a i r s u r f a c e , perhaps d e n s i t y v a r i a t i o n s w i t h i n the n e a r - s u r f a c e i c e , appear t o cause l a r g e s c a l e v a r i a t i o n s i n the n e a r ~ f i e l d of the antenna. At 840 MHz the g l a c i e r s u r f a c e cannot be modelled as a plane s u r f a c e , thus any s u r f a c e based experiment must c o l l e c t data with s u f f i c i e n t redundancy t h a t a s t a t i s t i c a l approach may be used. Our a t t e n u a t i o n estimate of f t a n S = 0.26, based on the average o f 72 r e c o r d s , i s our only measurement made with s u f f i c i e n t redundancy t h a t i t may be c o n s i d e r e d r e l i a b l e , l i m i t e d mainly by our knowledge of the bedrock r e f l e c t i v i t y . The l a s t comments suggest another p o t e n t i a l l y s e r i o u s drawback of the photographic r e c o r d i n g technigue. A s t a t i s t i c a l approach t o parameter measurement may r e g u i r e t h a t l i t e r a l l y thousands of r e c o r d s be- c o l l e c t e d d u r i n g a f i e l d experiment. Since i t r e q u i r e s on the order of ten minutes of la b o u r to d i g i t i z e a s i n g l e record the amount of time r e q u i r e d t o process a l a r g e number of photographs would be p r o h i b i t i v e . G l a c i e r s u r f a c e experiments f o r i c e p r o p e r t i e s measurements r e q u i r e an a c c u r a t e , s e r v i c e a b l e r e c o r d i n g medium as do a i r b o r n e surveys. In a d d i t i o n to our scheduled m o d i f i c a t i o n s to our a i r b o r n e system we are c o n c u r r e n t l y developing a p o r t a b l e , d i g i t a l , c a s s e t t e l o g g i n g system. We expect i t to provide more accu r a t e records than do photographs, and i n an immediately computer compatible format. I t w i l l a l s o e l i m i n a t e a heavy, power-hungry o s c i l l o s c o p e and support hardware. 61 CHAPTER 4. CONCLDDING REMARKS AND RECOMMENDATIONS FOR FUTURE EXPERIMENTS The work repo r t e d here has taken a p a r t i c u l a r l y Canadian view towards r a d i o echo sounding. The Canadian A r c t i c i s dotted with many s m a l l i c e masses l i k e l y of l e s s than 700 m depth, i n c l u d i n g v a l l e y and a l p i n e g l a c i e r s , as well as s e v e r a l i c e caps i n the A r c t i c A r c h i p e l a g o . We have shown by developing and a i r b o r n e t e s t i n g an 840 MHz r a d i o echo sounder t h a t a l l of these i c e f i e l d s should be w i t h i n the range of an UHF sounder. The advantages to t h i s approach are s e v e r a l . UHF antennae are r e a d i l y d e p l o y a b l e from l i g h t a i r c r a f t . T h i s i m p l i e s t h a t a i r b o r n e surveys can operate i n s m a l l v a l l e y s where l i g h t a i r c r a f t are necessary and where high gain antennae minimize i n t e r f e r e n c e . A l s o , the - use of l i g h t a i r c r a f t would ease l o g i s t i c problems a s s o c i a t e d i n mapping the A r c h i p e l a g o i c e caps s i n c e an UHF radar survey c o u l d be operated from one of- the s m a l l a i r c r a f t which r o u t i n e l y s e r v i c e these a r e a s . Our r e s u l t s from s u r f a c e based experiments c a r r i e d out on the Hazard G l a c i e r c o n f i r m t h a t with f t a n 8 = 0.26 at -5°C, 840 MHz must be i n c l u d e d i n the u s e f u l r a d i o echo sounding band. However these t e s t s a l s o demonstrate the extreme s e n s i t i v i t y of our system t o s m a l l s c a l e changes i n antenna p o s i t i o n , i n d i c a t i n g t h a t at these f r e q u e n c i e s the i c e / a i r s u r f a c e may not n e c e s s a r i l y be modelled as a p e r f e c t plane. Any s u c c e s s f u l experiments performed to monitor such " e f f e c t s as s t r e s s induced a n i s o t r o p y , bedrock roughness or i n t e r n a l s t r u c t u r e w i l l r e q u i r e a l a r g e data redundancy simply t o overcome the random e f f e c t s i n t r o d u c e d at the i c e / a i r s u r f a c e . 62 A common thread running through a l l of t h i s work has been the f a i l u r e o f our photographic r e c o r d i n g procedures t o provide r e l i a b l e and r e c o v e r a b l e data. We can s t r o n g l y recommend t h a t f u t u r e experiments be performed with some a l t e r n a t i v e r e c o r d i n g medium, p r e f e r a b l y magnetic tape, with c a p a b i l i t i e s f o r both c o n t i n u o u s r e c o r d i n g f o r a i r b o r n e surveys (analogous t o Z- scope), and spot r e c o r d i n g f o r s u r f a c e experiments (analogous to A-scope). We a r e , i n f a c t , p r e s e n t l y developing both types of r e c o r d e r s as two separate systems. The f i r s t i s based on a 4 channel FM t r a n s p o r t and the second on a d i g i t a l c a s s e t t e t r a n s p o r t . 63 LITERATURE CITED B a i l e y , J . T., and o t h e r s . 1964. Radio-echo sounding of p o l a r i c e sheets, by J . T. B a i l e y , S. Evans and G- de Q. Robin. Nature, V o l . 204, No. 4957, p. 420-21. Beckmann, P., and S p i z z i c h i n o , A. 1963 . The s c a t t e r i n g of e l e c t r o m a g n e t i c waves from rough s u r f a c e s . . O x f o r d , Pergamon Pr e s s . Bentley, C. R. 1979. Ice s t u d i e s : V i s i t to the Radio P h y s i c s Lab o r a t o r y of the A r c t i c and A n t a r c t i c Research I n s t i t u t e i n L e n i n g r a d . EOS T r a n s a c t i o n s , American Geophysical Onion, V o l . 60, No. 10, p. 151. Berry, M. V. 1972. On deducing the form of s u r f a c e s from t h e i r d i f f r a c t e d echoes. J o u r n a l o f Physics A: General Phy_sics, V o l . 5, p. 272-91. Berry, M. V. 1 9 7 3 . The s t a t i s t i c a l p r o p e r t i e s o f echoes d i f f r a c t e d from rough s u r f a c e s . P h i l o s o p h i c a l T r a n s a c t i o n s of the Royal S o c i e t y o f London, A, V o l . 2 7 3 , No. 1 2 3 7 , p. ? 1 1 - 5 4 . Campbell, K. J . , and Orange, A. S. 1974 . The e l e c t r i c a l a n i s o t r o p y of sea i c e i n the h o r i z o n t a l plane. J o u r n a l of Ge o p h y s i c a l Research, V o l . 7 9 , No. 3 3 , p. 5 0 5 9 - 6 3 . C l a r k e , G. K. C , and Goodman, R. H. 1 9 7 5 . Radio echo soundings and ice-temperature measurements i n a surge-type g l a c i e r . J o u r n a l of G l a c i o l o q y , V o l . 1 4 , No. 7 0 , p. 7 1 - 7 8 . C l a r k e , G.K.C., and Narod, B.B. Unpublished, tit. Logan radar survey, or the o p e r a t i o n was a success but the p a t i e n t d i e d . ^ I n t e r n a l r e p o r t , Department of Geophysics and Astronomy, U n i v e r s i t y of B r i t i s h Columbia, Vancouver, Canada, September 1 9 7 6 . J Clough, J - W. 1977 . Radio-echo sounding: r e f l e c t i o n s from i n t e r n a l l a y e r s - i n i c e . s h e e t s . J o u r n a l of G l a c i o l o q y ; V o l . 1 8 , No. 7 8 , p. 3 - 1 4 . Davis, J . L. Unpublished., The problem of depth sounding temperate g l a c i e r s . l_M.Sc. t h e s i s , U n i v e r s i t y of Cambridge, 1973 i J 64 Davis, J . L., and o t h e r s . 1973. Badio echo sounding of a v a l l e y g l a c i e r i n East Greenland, ;by - J . L. Davis, J . S. H a l l i d a y and K. J . M i l l e r . J o u r n a l of G l a e i o l o q y , Vol.,12, No. 64, p. 87-91. Delco. 1971. 28 v o l t D a r l i n g t o n s w i t c h i n g r e g u l a t o r . Delco E l e c t r o n i c s a p p l i c a t i o n note #49, December 1971 Evans, S. 1965. D i e l e c t r i c p r o p e r t i e s of i c e and snow a review. J o u r n a l of G l a e i o l o q y , V o l . 5, No. 42, p. 773-92. Goodman, B. H. 1975. Badio echo sounding on temperate g l a c i e r s . J o u r n a l of G l a e i o l o q y , V o l . 14, No. 70, p. 57-70. Goodman, B. H. and o t h e r s . 1975. Badio soundings on T r a p r i d g e G l a c i e r , Yukon T e r r i t o r y , Canada, by B. H. Goodman, G. K. C. C l a r k e , G. T. J a r v i s , S. G. C o l l i n s and B. M e t c a l f e . J o u r n a l of G l a e i o l o q y , V o l . 14, No. 70, p. 79-84. Gradshteyn, I. S.; and Byzhik, I. M. 1965. T a b l e s - o f I n t e g r a l s , S e r i e s , and Products. New York* Academic Press. Gudmandsen, P, and o t h e r s . 1976. New eguipment f o r radio-echo sounding, by P. Gudmandsen, E. N i l s s o n , M. P a l l i s g a a r d , N. Skou, and F. Sondergaard. El e c t r o m a g n e t i c I n s t i t u t e , the T e c h n i c a l O n i v e r s i t y of Denmark, Lyngby, D 257, 5 p. [ r e p r i n t e d from the A n t a r c t i c J o u r n a l , X(5), 1975, p..234- H a r r i s o n , C. fl. 1973. Badio echo sounding of h o r i z o n t a l l a y e r s i n i c e . J o u r n a l of G l a e i o l o q y , Vol. 12, No. 66, p. 393-97. Huynen, J . B. 1978. Phenomenological theory of radar t a r g e t s . (Uslenghi, P. L. E. ed.) E l e c t r o m a g n e t i c S c a t t e r i n g . New York, Academic P r e s s , p.653-712. J a s i k , H. ed. 1961. Antenna e n g i n e e r i n g handbook. New York, McGraw - H i l l . J o h a r i , G. P., and Jones, S. J . 1975. E f f e c t s due t o double r e f r a c t i o n i n echo-sounding of i c e . Glacipiggy. D i v i s i o n , Dept. of the Environment, Beport No. 113-75G, 562 Booth St., Ottawa, Canada. 6. a 65 Longhurst, R. S. 1 9 5 7 . Geometrical and p h y s i c a l O p t i c s . London, Longmans. Myers, a. ed. 1975 . The r a d i o amateur's handbook, f i f t y - s e c o n d e d i t i o n . American fiadio Relay League, Newington, Conn. Napoleoni, J . G. P*, and C l a r k e , G.-K. C. 1978. Hot water d r i l l i n g i n a c o l d g l a c i e r . Canadian J o u r n a l of Earth S c i e n c e s . V o l . 1 5 , No. 2 , p. 3 1 6 - 2 1 . Narod, B. B. Unpublished. UHF r a d i o echo sounding of g l a c i e r s , l_M.Sc. t h e s i s . U n i v e r s i t y o f B r i t i s h Columbia, 1975 . J Nye, J . F., and o t h e r s . 1972. P r o p o s a l f o r measuring the movement of a^ l a r g e i c e sheet by observing r a d i o echoes, by J . F. Nye, R. G. Kyte and D. C. T h r e l f a l l . J o u r n a l of G l a c i o l o g y . V o l . 11, No. 63, p. 319-25. Oswald, G. K. A. Unpublished. Radio echo s t u d i e s of polar g l a c i e r beds. J.Ph.D. t h e s i s . U n i v e r s i t y of Cambridge, 1975.J Panofsky, W. K. H., and- P h i l l i p s , M. 1962. C l a s s i c a l e l e c t r i c i t y and magnetism. Reading, Mass., Addison-Wesley. Robin, G;' de Q. 1975. Radio-echo sounding: g l a c i o i o g i c a l i n t e r p r e t a t i o n s and a p p l i c a t i o n s . J o u r n a l of - G l a e i o l o q Y , V o l . 15, No. 73, p. 49-64. Sharp, R. P. 1960. G l a c i e r s . Eugene, Oregon, U n i v e r s i t y of Oregon P r e s s . Smith, B. M. E., and Evans, S. 1972. Radio echo sounding: a b s o r p t i o n and s c a t t e r i n g by water i n c l u s i o n s and i c e l e n s e s . J o u r n a l of G l a c i o l g g y , V o l . 11, No. 61, p. 133-46. Sondergaard, F., and Skou, N. 1976. R a d i o g l a c i o l o g y s i d e - l o o k i n g r adar imaging and depth soundings of i c e a t 300 MHz. E l e c t r o m a g n e t i c s I n s t i t u t e , the T e c h n i c a l : u n i v e r s i t y of Denmark, Lynqby, R 170, 51 p. S t r a t t o n , J . A. 1941. E l e c t r o m a g n e t i c Theory. New York, McGraw - H i l l . . 66 Swxthxnbank, C. 1968. Badio echo sounding of A n t a r c t i c g l a c i e r s from l i g h t a i r c r a f t . Onion Geodesigue et Geojohysigue I n t e r n a t i o n a l e . A s s o c i a t i o n I n t e r n a t i o n a l e d'Hydrologie S c i e n t i f i g u e . Assemble 'generale de Berne, 25 SeptT-7 Oct. JS67. ICommision de Neiges et G l a e e s . J Bapports et ~ d i s c u s s i o n s , p. 405-14. Waite, A.H. 1966. I n t e r n a t i o n a l experiments i n g l a c i e r sounding, 1963 and 1964. Canadian J o u r n a l of Earth S c i e n c e s , V o l . 3, No. 6, p. 887-92. 67 APPENDIX J : DETAILS OF THE RADIO ECHO SOONPES A1.1 GENERAL DESCRIPTION AND OPERATION Th i s appendix i s d i v i d e d i n t o f i v e s e c t i o n s . The f i r s t s e c t i o n i s an o p e r a t i o n s n o t i c e which d e t a i l s how to connect the v a r i o u s p i e c e s of the r a d i o echo sounder and how t o operate the complete system. In p r i n c i p l e t h i s i s the only s e c t i o n with which the new user need he concerned. The remaining f o u r s e c t i o n s d e a l i n d e t a i l i n t u r n with the t r a n s m i t t e r , the r e c e i v e r , the r e g u l a t i n g power supply and the antenna. They should be c o n s u l t e d when more than a b a s i c knowledge of the component i s r e q u i r e d . These s e c t i o n s i n c l u d e complete c i r c u i t diagrams of each p a r t as well as f u n c t i o n a l d e s c r i p t i o n s of a l l c i r c u i t r y . T h i s appendix i s intended to be an exact s p e c i f i c a t i o n and d e s c r i p t i o n of the r a d i o echo sounder as used d u r i n g the 1976 f i e l d p r o j e c t , however i t has been w r i t t e n so t h a t a user of the r a d i o echo sounder other than the author w i l l be a b l e to operate and s e r v i c e the sounder, the l a t t e r at l e a s t i n components where user s e r v i c i n g i s p o s s i b l e . 68 A1.1.1 SYSTEM ASSEMBLY POWEB SUPPLY AND DISTRIBUTION The power f o r the r a d i o echo sounder and any. a u x i l i a r y i n s t r u m e n t s i s d i s t r i b u t e d by the s w i t c h i n g r e g u l a t o r . .Power i s fed i n t o the r e g u l a t o r v i a one of the f i v e standard c i r c u l a r c onnectors on the r e g u l a t o r f r o n t p a n e l . The connector with the male i n s e r t r e c e i v e s the incoming power while the f o u r connectors with female i n s e r t s are used as power outputs. In each connector there are f i v e p i n s . Pin A of each connector i s connected t o the output of the s w i t c h i n g r e g u l a t o r . The p i n B's are a l l connected to the i n p u t power, while the p i n E*s are connected to the ground r e f e r e n c e . . In normal use the t r a n s m i t t e r always draws power from the output of the r e g u l a t o r on p i n A while the r e c e i v e r and the o s c i l l o s c o p e draw unregulated power from pin B. The a d d i t i o n a l connector i s a v a i l a b l e f o r a u x i l i a r y instruments. Pin C and D of each connector are r e s e r v e d f o r f u t u r e expansion. The assembled r a d i o echo sounder ( F i g . A1.1) w i l l run o f f any power source which can provide 10A at 22 V t o 28 V, f o r example two automotive b a t t e r i e s connected i n s e r i e s or a 10A, 28 V a u x i l i a r y c i r c u i t i n an a i r c r a f t . Since each power source u s u a l l y has i t s own system f o r co n n e c t i o n , care must be taken when con n e c t i n g i t to the s w i t c h i n g r e g u l a t o r . The p o l a r i t y of the power c o n n e c t i o n must not be r e v e r s e d . An i n c o r r e c t c o n n e c t i o n w i l l d e s t r o y the high-power s w i t c h i n g t r a n s i s t o r i n the r e g u l a t o r . When properly connected and f u n c t i o n i n g the REGULATOR TRANSMITTER N N\ CIRCULATOR N Trig 22-28vDC POWER IN Z DC POWER CM Ch2 trig T FIG.A1.1 RECEIVER OSCILLOSCOPE RADIO ECHO SOUNDER BLOCK DIAGRAM 70 r e g u l a t o r w i l l emit a h i g h - p i t c h e d whine caused by high frequency c o n t r a c t i o n s of the f l y b a c k i n d u c t o r . The i n p u t and output v o l t a g e s can be monitored by s e t t i n g the monitor s w i t c h i n e i t h e r p o s i t i o n B or A r e s p e c t i v e l y and observing the v o l t a g e on the panel meter. Should the r e g u l a t o r f a i l f o r any reason (other than s h o r t c i r c u i t s or power diode f a i l u r e ) i t would s t i l l be p o s s i b l e t o operate the r a d i o echo sounder provided the i n p u t v o l t a g e exceeds 27 V. When the system i s reconnected c o r r e c t l y the r e g u l a t o r output voltage which t r a c k s the i n p u t v o l t a g e w i l l then be over 26 V which i s s u f f i c i e n t to d r i v e the t r a n s m i t t e r . The panel meter i s diode p r o t e c t e d so that i t should always f u n c t i o n s a t i s f a c t o r i l y . Connection procedure should be as f o l l o w s : Arrange f o r connection to a s u i t a b l e power source. C a r e f u l l y check p o l a r i t y and connect the r e g u l a t o r to the source. L i s t e n f o r the high p i t c h e d whine and use the s e l e c t o r switch.and panel meter to check t h a t the i n p u t and output voltages are at s u i t a b l e l e v e l s . Osing provided c a b l e s connect . the t r a n s m i t t e r , r e c e i v e r , o s c i l l o s c o p e and a u x i l i a r y i n s t r u m e n t s . t o the r e g u l a t o r . Check b r i e f l y t h a t each instrument operates normally ( a l l instruments have panel lamp power i n d i c a t o r s ) . Make sure t h a t . the o s c i l l o s c o p e power s e l e c t o r switch i s s e t to 24 VDC. . I f any instrument f a i l s to f u n c t i o n check t h a t i t s f u s e s are s a t i s f a c t o r y . 71 B. F. CONNECTIONS U s u a l l y the r a d i o echo sounder i s operated with a s i n g l e antenna. In t h i s case both the t r a n s m i t t e r and r e c e i v e r must be connected to the antenna-via a c i r c u l a t o r . A c i r c u l a t o r i s a passive T/B s w i t c h i n g device with a t l e a s t t h r e e p o r t s . The c o n s t r u c t i o n i s such t h a t power f e d i n t o p o r t 1 e x i t s from p o r t 2, and power fed i n t o p o r t 2 e x i t s from p o r t 3. With the provided c i r c u l a t o r , power from the t r a n s m i t t e r i s fed i n t o port 1. The t r a n s m i t t e d pulse e x i t s from p o r t 2 which i s connected to the antenna. The t r a n s m i t t e d pulse i s r a d i a t e d from the antenna. The r e f l e c t e d power i s r e c e i v e d at the antenna and f e d back i n t o port 2. The r e c e i v e d power then e x i t s from port 3 which i s connected t o the r e c e i v e r . The system i s not p e r f e c t i n t h a t the port 1 to 3 i s o l a t i o n i s only about 25 dB so t h a t about 12 w from the t r a n s m i t t e r p l u s any power from r e f l e c t i o n s due to antenna impedance mismatch w i l l be fed d i r e c t l y i n t o the r e c e i v e r i n p u t . In the event of an antenna c a b l e f a i l u r e a 4 Kw s p i k e would be r e f l e c t e d i n t o the r e c e i v e r i n p u t . T h i s s i t u a t i o n has been a n t i c i p a t e d , and i n the r e c e i v e r design p r o t e c t i o n c i r c u i t r y capable of withstanding the high power shock has been i n s t a l l e d . The t r a n s m i t t e r i s a l s o f u l l y p r o t e c t e d by an i s o l a t o r a g a i n s t B.F. power being r e f l e c t e d back i n t o i t (an i s o l a t o r i s simply a c i r c u l a t o r with a dummy loa d on port 3). A l l o f the high-power B.F. connections i n t h e r a d i o echo sounder use type N connectors and EG-8U or EG-213U c a b l e s . When op e r a t i n g from a hookmount on a h e l i c o p t e r an a d d i t i o n a l GE 72 connector l i n k should be i n s t a l l e d near the antenna i n the antenna feed l i n e . The GE l i n k comprises a type N female to GB adapter and a GB to type N male adapter. The f r i c t i o n c o u p l i n g i n the GB c o n n e c t i o n e f f e c t s a "weak l i n k " . In the event t h a t the p i l o t of the h e l i c o p t e r i s f o r c e d to j e t t i s o n the antenna the GB connection w i l l open and break the c a b l e l i n k t o the antenna. The B.F. connections should be made as f o l l o w s : Using a type N male-male adapter and an o p t i o n a l type N r i g h t - a n g l e adapter connect the t r a n s m i t t e r B.F. output to p o r t 1 of the c i r c u l a t o r . Using a 1 meter type N cable connect the r e c e i v e r B.F. i n p u t t o p o r t 3 of the c i r c u l a t o r . Connect a 5 meter c a b l e to port 2 of the c i r c u l a t o r and run the c a b l e to the antenna. The c a b l e s w i t h i n the antenna i t s e l f should be taped to the antenna r e f l e c t o r t o r e l i e v e s t r a i n . The antenna c o n n e c t i o n i t s e l f - uses two type N "Tee" adapters and a tuning stub. The c o n n e c t i o n can be a r t i c u l a t e d t o allow f o r a convenient approach by the antenna feed l i n e . I f r e q u i r e d i n s t a l l the weak l i n k c o n n e c t i o n on the antenna and connect the f r e e end of the antenna feed l i n e . C a u t i o n : when o p e r a t i n g , the r a d i o echo sounder r a d i a t e s s u f f i c i e n t B.F. power t o be c o n s i d e r e d hazardous. Do not stand i n f r o n t o f the antenna while the r a d i o echo sounder i s o p e r a t i n g . BEMAINING BECEIVEB TO TEANSMITTEB CONNECTIONS In a d d i t i o n to the B.F. c o n n e c t i o n there are two other 73 connec t i o n s between the t r a n s m i t t e r and the r e c e i v e r . One i s the l o c a l o s c i l l a t o r power, the other i s the t r a n s m i s s i o n t r i g g e r p u l s e . The l o c a l o s c i l l a t o r (L.O.) power i s generated i n the t r a n s m i t t e r and i s frequency-?locked to a 120 MHz c r y s t a l o s c i l l a t o r a l s o i n the t r a n s m i t t e r . The l a t t e r p r o v i d e s a r e f e r e n c e f o r both the 720 MHz L.O. and the 840 MHz t r a n s m i t t e r c a r r i e r f r e g u e n c i e s . The con n e c t i o n , made by a t t a c h i n g an RG-58 SM4 c a b l e t o the sockets marked "L.O." on each of the t r a n s m i t t e r and the r e c e i v e r , p r o v i d e s 160mW of L.O. power to a mixer i n the r e c e i v e r which co n v e r t s the r e c e i v e d R.F. s i g n a l to the 120 MHz r e c e i v e r i n t e r m e d i a t e freguency ( I . F . ) . The t r a n s m i s s i o n t r i g g e r pulse i s generated i n the r e c e i v e r l o g i c c i r c u i t r y . I t has been p r e s e t t o 50ns pulse l e n g t h and i s capable o f d r i v i n g 5 V i n t o a 50Q. l o a d . T h i s pulse t r i g g e r s the medium power R.F. a m p l i f i e r as we l l as gating the high power R.F. a m p l i f i e r . In t h i s way the R.F. pulse l e n g t h i s e x t e r n a l l y a d j u s t a b l e while maintaining a high on/off r a t i o f o r d e t e c t i n g s i g n a l s a f t e r long d e l a y s . The co n n e c t i o n i s made by a t t a c h i n g a second RG-58 SMA ca b l e to sockets marked "PULSE IN" on the t r a n s m i t t e r and " T r i g " on the r e c e i v e r . OSCILLOSCOPE CONNECTIONS F i v e BNC connectors on the r e c e i v e r f r o n t panel provide a l l the s i g n a l s r e q u i r e d t o make photographic r e c o r d s from a Tektr o n i x 475 o s c i l l o s c o p e . They have been marked "T", "A", 74 "Z", "V", and "E". The f u n c t i o n s of each i s d e s c r i b e d i n the f o l l o w i n g paragraphs. The connector marked "T" i s a twin of the SMA connector marked " T r i g " . I t s e r v e s as a backup t r i g g e r source to the l a t t e r as w e l l as a t r i g g e r f o r the o s c i l l o s c o p e . I t s e l e c t r i c a l p r o p e r t i e s are i d e n t i c a l with " T r i g " . The "A" connector c a r r i e s the unmodified video output of the I-F. a m p l i f i e r - d e t e c t o r s t r i p i n the r e c e i v e r . The impedance i s 93 D. and the s i g n a l s t a y s between 0 and +3 V with 40 hHz bandwidth. The A s i g n a l i s used f o r a l l "A-scope" re c o r d s (X-Y photos of power vs. ti m e ) . The "Z" connector c a r r i e s the output of the video a m p l i f i e r . I t i s normally used only as a monitor of the video s i g n a l . The "V" connector c a r r i e s a s i g n a l c a l l e d "mixed v i d e o " . I t i s i d e n t i c a l i n nature to the Z s i g n a l except t h a t a frame code or grey s c a l e can be momentarily switched i n t o the data stream. Both the V and Z s i g n a l can be used to modulate the i n t e n s i t y of the phosphor b r i g h t n e s s . The "E" connector c a r r i e s a slowly v a r y i n g ramp which i s used t o scan an i n t e n s i t y modulated l i n e t r a c e v e r t i c a l l y a c r o s s the o s c i l l o s c o p e screen. T h i s s i g n a l i s used when continuous r e c o r d s are r e q u i r e d . Connecting the o s c i l l o s c o p e i n t o the r a d i o echo sounder system r e q u i r e s f o u r BNC c a b l e s which should be deployed as f o l l o w s . Connect the r e c e i v e r "T" output to the " e x t e r n a l t r i g " connector on the o s c i l l o s c o p e (lower r i g h t ) . Set the o s c i l l o s c o p e t r i g g e r source on "EXT", c o u p l i n g on "DC", s l o p e on 75 p o s i t i v e , mode on "AUTO" and h o r i z o n t a l mode on 11 A l o c k s knob". Connect the r e c e i v e r k output to the o s c i l l o s c o p e Ch1 i n p u t . Set the Ch1 a t t e n u a t o r a t 0.5 V/div with DC c o u p l i n g . Connect the E output to the o s c i l l o s c o p e Ch2 i n p u t . Set the Ch2 a t t e n u a t o r at 2 V/div with DC c o u p l i n g . Connect the V output to the o s c i l l o s c o p e Z-axis i n p u t (rear o f instrument) . A1.1.2 OPERATION OF THE BADIO ECHO SOUNDER INITIAL SETUP A f t e r assembly s e v e r a l s t e p s must be taken before any photographic r e c o r d s are to be taken. The procedure which f o l l o w s need be done only a t the beginning of o p e r a t i o n . Turn on the power f o r the t r a n s m i t t e r and the o s c i l l o s c o p e . The f l a s h i n g l i g h t on the t r a n s m i t t e r i n d i c a t e s t h a t i t i s i n i t s warmup c y c l e . During t h i s p e r i o d the high v o l t a g e supply i n the t r a n s m i t t e r i s d i s a b l e d . At the end of t h i s warmup. p e r i o d the lamp w i l l stay on c o n t i n u o u s l y . Turn on the power f o r the r e c e i v e r . On the o s c i l l o s c o p e s e l e c t Chi as the v e r t i c a l source. Adjust the t r i g g e r l e v e l so t h a t the echogram i s s t a b l e . Adjust the v e r t i c a l p o s i t i o n to midframe. Set the timebase on 1 u s / d i v or 500 n s / d i v depending on the expected i c e t h i c k n e s s . Set the bandwidth to 100 MHz or 20 MHz depending on s i g n a l to n o i s e and r e s o l u t i o n requirements (20 MHz g i v e s b e t t e r s i g n a l to n o i s e , 100 MHz g i v e s b e t t e r r e s o l u t i o n ) . Attach the P o l a r o i d camera t o the o s c i l l o s c o p e . The o s c i l l o s c o p e i s now s e t up f o r A-scope photographs. 76 Only one a d d i t i o n a l i n i t i a l adjustment i s r e q u i r e d f o r I-scope r e c o r d i n g . S e l e c t Ch2 as the v e r t i c a l source, uncouple the Ch2 s i g n a l (set switch to GND), a d j u s t the v e r t i c a l t r a c e p o s i t i o n to three g r a t i c u l e d i v i s i o n s below c e n t r e , recouple the Ch2 s i g n a l t o DC. A-SCOPE RECORDING To make an A-scope photograph use the f o l l o w i n g procedure. S e l e c t Ch1 as the v e r t i c a l source. Adjust the screen b r i g h t n e s s to medium b r i g h t n e s s . Close the camera onto the o s c i l l o s c o p e . Set the s h u t t e r speed a t 1/60 s. l e t the aperture at f:4 (approximate). Operate the camera i n the usual manner. G e t t i n g a w e l l exposed frame may r e q u i r e s e v e r a l attempts before the operator i s f a m i l i a r with the r e q u i r e d b r i g h t n e s s / a p e r t u r e combination. Z-SCOPE RECORDING In t h i s mode i t i s p o s s i b l e to use the P o l a r o i d camera t o make continuous r e c o r d s . S e l e c t Ch2 as the v e r t i c a l source. Adjust the screen b r i g h t n e s s to the minimum b r i g h t n e s s while m a i n t a i n i n g s i g n a l v i s i b i l i t y . The operator may choose t o use the grey s c a l e as a source f o r s e t t i n g the b r i g h t n e s s . Depressing the momentary "GREY SCALE" t o g g l e s w i t c h w i l l s w i tch the grey s c a l e i n t o the video s i g n a l . T h i s shows up as an e i g h t 77 step s t a i r c a s e s t a r t i n g with the b r i g h t e s t s t e p a t the l e f t of the screen. Set up the r e c e i v e r as f o l l o w s . S e l e c t a d u r a t i o n f o r each r e c o r d using the r o t a r y s w i t c h . One minute i s t y p i c a l . Using the "RESET" and "RUN" switches p r e s e t the frame code to one l e s s than the r e q u i r e d s t a r t i n g frame number. The frame code i s d i s p l a y e d i n o c t a l on the r e c e i v e r . The r e c e i v e r w i l l a u t o m a t i c a l l y increment the frame count a f t e r each de p r e s s i o n of the "START" swit c h . To expose a frame f i r s t c l o s e the camera onto the o s c i l l o s c o p e , s e t the s h u t t e r speed at "T" (time exposure) and the a p e r t u r e a t f:16. Press the s h u t t e r r e l e a s e and depress the "START" switch on the r e c e i v e r . T h i s a c t i o n w i l l cause the frame code t o increment by one and the "READY" lamp to e x t i n g u i s h . When the "READY" lamp has r e l i t p ress the s h u t t e r r e l e a s e a g a i n . T h i s a c t i o n c l o s e s the camera s h u t t e r . A f t e r removing the f i l m frame the c y c l e i s ready to be repeated. With p r a c t i c e the e n t i r e procedure can be accomplished i n l e s s than ten seconds. Examination o f an I-scope photograph w i l l r e v e a l the f o l l o w i n g . Each record s t a r t s a t the bottom of the screen by exposing f i r s t the grey s c a l e , then the frame code i n t o the p i c t u r e . T h i s process uses 1/16th of the t o t a l r e c o r d time. 78 A1.2 THE TRANSMITTER In p r i n c i p l e the r a d i o echo sounder t r a n s m i t t e r ( F i g . A1.2) i s simply a gated R.F. o s c i l l a t o r . I t s s o p h i s t i c a t i o n r e s u l t s from i t s h i g h output power l e v e l , f a s t s w i t c h i n g times, s t a b l e freguency and f o o l p r o o f , o v e r l o a d - s e n s i t i v e power supply. The c i r c u i t design and the instrument were provided f o r the U n i v e r s i t y of B r i t i s h Columbia by Microwave C o n t r o l Co., New Jer s e y . The f o l l o w i n g i n f o r m a t i o n has been i n c l u d e d here s o l e l y f o r user i n t e r e s t and to a i d p o s s i b l e f i e l d s e r v i c e a b i l i t y . No r i g h t s to the design are i m p l i e d . A1.2. 1 -POWER SUPPLY REGULATORS The i n p u t power r e g u l a t o r s provide +26 V and +5 V f o r the t r a n s m i t t e r . The +26 V r e g u l a t o r output ( F i g . A1.3) i s r e f e r e n c e d t o Zener diode D1. I f the output voltage r i s e s t r a n s i s t o r Q1 i s bia s e d on which i n c r e a s e s the s i n k c u r r e n t i n t r a n s i s t o r Q2 thereby p u l l i n g down the output v o l t a g e . The +5 V r e g u l a t o r ( F i g . A 1.4) i s a simple shunt r e g u l a t o r with t r a n s i s t o r Q24 being used as a v a r i a b l e c u r r e n t s i n k r e f e r e n c e d to Zener diode D29. FIG. A1.2 TRANSMITTER: PICTORIAL ID VSAA- R6 VSAA- if k ri - L C1 R7 R10 02 D3 R11 FIG. A1.3 REGULATOR CIRCUIT DIAGRAM 81 R51 O \AA/—* •i D10 •5VO 3 1 4 8 7 SE555V RESET *26V R58 D11 W V Q18 R59 4=C66 D12 i| Df R60 A/v\— 1 E N A B L E +5V O +5V ^ R5|3 1/3 SN5410 Q R55 1/3 SN 5410 14 12 ! SN7493A g 8 11 5 2 10 1/3 SN5410 •O +5V I- R56 +5V O 'I TIMING LIGHT , O 017 R57 1 / 12 I H 1 SN7493A 5 10 11 2 POWER SUPPLY TIMING CIRCUIT SCHEMATIC DIAGRAM FIG. A1.4 82 WABM-UP TIMING CIRCUIT When power i s f i r s t a p p l i e d to the t r a n s m i t t e r the hig h v o l t a g e power supply i s d i s a b l e d t o allow time f o r the t r i o d e f i l a m e n t s to warm up. A d i g i t a l c i r c u i t ( Fig- A1.4) de l a y s the high v o l t a g e enable f o r approximately two minutes. At power-up c a p a c i t o r C66 i s discharged f o r c i n g t r a n s i s t o r Q18 to be switched o f f . As a r e s u l t p u l l - u p r e s i s t o r B60 and Zener diode D12 ensure a TTL high l o g i c l e v e l on r e s e t p i n 2 of each SN7493 hex counter. Thus as power-up both counters are r e s e t . Reset c i r c u i t r e l a x a t i o n then t u r n s on t r a n s i s t o r Q18 and the r e s e t l i n e s are brought t o a low l e v e l . An SE555V timer provides a s t a r t - u p c y c l e c l o c k . At power- up the count enable l i n e i s low and the SE555V i s i n a s t a b l e v i b r a t i o n . The open c o l l e c t o r output on p i n 3 d r i v e s a NAND gate used as an i n v e r t e r . The output on the NAND gate d r i v e s the base of t r a n s i s t o r Q17 through r e s i s t o r R56. T r a n s i s t o r Q17 d r i v e s t he f r o n t panel t i m i n g l i g h t causing i t t o f l a s h on and o f f a t the count frequency.. The c l o c k pulse i s i n v e r t e d again i n a NAND gate and d r i v e s the cl o c k i n p u t (pin 14) of an SN7493A counter. The Q4 output provides a c l o c k pulse f o r the second SN7493A c o u n t e r . The Q2, Q3 and Q4 outputs o f the second counter are "NAND"ed to determine the ENABLE l e v e l . When the count reaches hex'EO' the ENABLE l e v e l goes low r e s e t t i n g the SE555V m u l t i v i b r a t o r and f o r c i n g a high c l o c k i n p u t on the f i r s t SN7493A counter. A low l e v e l from the m u l t i v i b r a t o r i s i n v e r t e d and t u r n s on t r a n s i s t o r -Q17 c o n t i n u o u s l y . At t h i s time the panel lamp remains on c o n t i n u o u s l y i n d i c a t i n g the end of the 83 warm-up p e r i o d . POWEB SUPPLY DBIVEE A l l power s u p p l i e s are c o n s t r u c t e d using s t e p - u p / i s o l a t i o n t r a n s f o r m e r s . C u r r e n t s i n the primary windings are switched by t r a n s i s t o r s Q19, Q20, Q21 and Q22 ( F i g . A1.5). P u l s e s to d r i v e these t r a n s i s t o r s are d e r i v e d i n the power supply d r i v e r . The b a s i c transformer freguency i s determined by an MC4324 a s t a b l e m u l t i v i b r a t o r and a J-K f l i p - f l o p (1/2 SN5473) ( F i g . A1.6). The Q and Q outputs of the f l i p - f l o p a l t e r n a t e l y enable p u l s e s onto the bases cf t r a n s i s t o r s Q26 and Q28 i n the high v o l t a g e d r i v e , and t r a n s i s t o r s Q30 and Q32 i n the low v o l t a g e d r i v e . Duty c y c l e s f o r the high, and low v o l t a g e d r i v e s are independently determined by two monostable v i b r a t o r s i n a SN54123. The two monostable v i b r a t o r s a re t r i g g e r e d s i m u l t a n e o u s l y with s t a t e changes i n the J-K f l i p - f l o p . The pu l s e l e n g t h f o r the low v o l t a g e supply d r i v e s i s pr e s e t by r e s i s t o r s B82 and E84 and c a p a c i t o r C78. The output of t h i s v i b r a t o r (pin 4) i s normally high and goes low when the v i b r a t o r i s - t r i g g e r e d . When low both t r a n s i s t o r s Q30 and Q32 are switched on p u l l i n g down e m i t t e r - f o l l o w e r t r a n s i s t o r s Q29 and Q31. At t h i s time both t r a n s i s t o r s Q19 and Q20 are switched o f f and no c u r r e n t f l o w s i n the primary winding of the low v o l t a g e power t r a n s f o r m e r . At the end of the monostable c y c l e the output of one of the POWER SUPPLY DRIVER 26V + 5V ENABLE K—j COLLECTOR BIAS TIMER TIMING LIGHT RESET POWER SUPPLY WIRING DIAGRAM D13 Dtt 2 T 2T C67 R61 26V D15 A 66T FIL.1 £ 7 [ 6T FIL.2 D16 4D17 i 0 1 - w v R62 8 C69 D.19 C70 D20 D 21 4000 V AMP. 2 2000 V O AMP. 1 AAAv— D26 R76 to MON.PIN-H R63 A A A H O CATHODE BIAS .••91 V to MON. PIN - F R77 -AAA/— R 78 • 5V O R79 LXQ23 1r80 R81 H.V. ADJUST to MON.PjN-G. — — • FIG. A1.5 PRIMARY • 5V R72 D27 R73 D28 D29 Q24 ^-*5V 13MC4324 12- H 11 tcl 9 7 8 H.V AD J O - C77 R74 -LC76 • 5V 1 9 SN5A123 6 7 13 1 3 U SN5473 12! 11 1 3 C78 •5V —O •5 V O- SN5410 ENABLE SN5410 85 • 5V •R86 C79 •—I—• R85 Q25 A -O Q26 D30 >R87 • 5V R88 C80 — i f — Q27 POWER SUPPLY DRIVER SCHEMATIC DIAGRAM Q28 D31 R89 ?R90 •5V R91 C 81 Q29 R92 Q30 A • 5 V D32 <R93 R94 €82 —Ih— Q 32 R95 0 31 <R96 D33 -O B C -O COLLECTOR BIAS — O FIG A1.6 86 NAND gates d r i v e n by the monostable v i b r a t o r goes low, s w i t c h i n g o f f one of the t r a n s i s t o r s Q30 or Q32 and through t r a n s i s t o r Q29 or Q31 s w i t c h i n g on one of t r a n s i s t o r s Q19 or Q20. A d j u s t i n g v a r i a b l e r e s i s t o r R82 v a r i e s the standby time of the m u l t i v i b r a t o r , which v a r i e s the RMS output v o l t a g e o f the transformer without v a r y i n g the peak output v o l t a g e . Source v o l t a g e f o r the c o l l e c t o r s of t r a n s i s t o r s Q25, Q27, Q29 and Q31, a f t e r s t a r t - u p from r e s i s t o r R61, comes from diodes D13 and D14 and c a p a c i t o r C67. The high v o l t a g e supply i s turned on when the ENABLE l i n e , d e r i v e d i n the timer, goes low. In the same manner as i n the low v o l t a g e supply, the high v o l t a g e supply duty c y c l e i s c o n t r o l l e d by a monostable v i b r a t o r . The high v o l t a g e supply, however, i s feedback r e g u l a t e d . I f the + 4 KV supply t r i e s t o go too high the voltage on the tap of v a r i a b l e r e s i s t o r ( F i g . A1.7) R78 approaches +5 V and t r a n s i s t o r Q23 sw i t c h e s o f f . T h i s e f f e c t i v e l y i n c r e a s e s the s e r i e s r e s i s t a n c e to m u l t i v i b r a t o r p i n 6 (R81 and R75 are one r e s i s t o r , shown twice i n the two separate drawings), i n c r e a s i n g the monostable c y c l e time and re d u c i n g the standby time. T h i s reduces the power a v a i l a b l e to the high voltage power tra n s f o r m e r primary winding f o r c i n g the high v o l t a g e output t o drop. LOW VOLTAGE SUPPLY The low v o l t a g e supply ( F i g . A1.5) pr o v i d e s two f i l a m e n t s u p p l i e s and a +91 V cathode b i a s supply. The f i l a m e n t s u p p l i e s 87 0 H.V. ADJUST OVERLOAD ADJ. POWER SUPPLY BOARD H.V. CAPS POWER IN RIGHT SIDE INPUT-© CATHODE MODULATOR OUTPUT LEFT SIDE TRANSMITTER: INTERNAL (NOT TO SCALE) FIG. A1.7 LAYOUT 88 are unregulated a f t e r the + 26 V r e g u l a t o r . Filament c u r r e n t s to the two t r i o d e s are c o n t r o l l e d by v a r i a b l e r e s i s t o r s R2 and R3. The cathode b i a s supply i n c l u d e s a f u l l wave r e c t i f i e r u sing diodes D15, D16, D17 and D18 and storage c a p a c i t o r C69. The supply i s shunt r e g u l a t e d by Zener diode D19 and r e s i s t o r R62. E x c e s s i v e power wastage i s avoided i n a manner d e s c r i b e d p r e v i o u s l y . HIGH VOLTAGE SUPPLY The high v o l t a g e supply ( F i g . A 1.5} p r o v i d e s a +2 KV supply f o r the f i r s t t r i o d e a m p l i f i e r and a +4 KV supply f o r the f i n a l t r i o d e a m p l i f i e r . The +2 KV supply uses f o u r diodes D22, D23, D24 and D25 i n a f u l l wave r e c t i f i e r and storage c a p a c i t o r C74. The +4 KV supply adds v o l t a g e doubler d i o d e s D20 and D21 and storage c a p a c i t o r C71. The high v o l t a g e supply r e g u l a t i o n was p r e v i o u s l y d e s c r i b e d . The supply i s o v e r - l o a d p r o t e c t e d . I f the l o a d d i s s i p a t i o n i n c r e a s e s f o r any reason the (negative) voltage a c r o s s c u r r e n t sense r e s i s t o r R70 a l s o i n c r e a s e s . The drop p u l l s down (through Zener diode D26 and r e s i s t o r R76) the RESET v o l t a g e . I f the RESET l i n e drops too low t r a n s i s t o r Q18 switches o f f r e i n i t i a t i n g the s t a r t - u p sequence with ENABLE l i n e h i g h . The overload l e v e l i s p r e s e t by v a r i a b l e r e s i s t o r R71. i 89 A1.2.2 MODULATOR" The modulator c o n t r o l s s e p a r a t e l y the gain of two stages of R.F. a m p l i f i c a t i o n . The pulse a m p l i f i e r gates the 20 H s o l i d s t a t e R.F. a m p l i f i e r , and the cathode modulator gates the f i r s t t r i o d e a m p l i f i e r . Both modulators take t h e i r i n p u t s i g n a l s from the 50 TTL l e v e l "PULSE IN" s i g n a l . PULSE AMPLIFIER The incoming pulse i s b u f f e r e d by a DM8830 l i n e d r i v e r , ( F i g . A1.8) then a m p l i f i e d / i n v e r t e d i n a p u s h - p u l l a m p l i f i e r c o n s t r u c t e d from t r a n s i s t o r s Q8 and Q10. R e s i s t o r R71 i s adj u s t e d so t h a t the pulse l e n g t h cannot exceed 200ns. The pulse i s again a m p l i f i e d / i n v e r t e d by t r a n s i s t o r Q_9 which a c t s as a power switch f o r the s o l i d s t a t e R.F. a m p l i f i e r . The output v o l t a g e swings between 0 and +25 V. CATHODE MODULATOR The cathode modulator ( F i g . A 1.9) i s very s i m i l a r to the pulse a m p l i f i e r . The incoming pulse i s a m p l i f i e d / i n v e r t e d by t r a n s i s t o r Q6. R e s i s t o r R16 i s s e t to l i m i t the maximum p u l s e l e n g t h t o 200 ns. The pulse i s a m p l i f i e d / i n v e r t e d by a push- p u l l a m p l i f i e r c o n s t r u c t e d from t r a n s i s t o r s Q3, Q4 and Q7. The a d d i t i o n a l e m i t t e r - f o l l o w e r t r a n s i s t o r Q4 has been added t o the pu s h - p u l l a m p l i f i e r t o boost the source c u r r e n t d r i v e c a p a b i l i t y 90 WALL 26 V FROM R.F. AMP. R22 'R23 < R24 PULSE IN J8 J9 D5 TO CATHODE MODULATOR 1 U 2 3 U DM 5 8830 6 7 8 C13 C16 If R27 R30 H A A » C17 R25 C18 R32 D7 R33 R26 C10 C11 C12 Ml—I1' 09 R31 D6 TO R.F. AMP. ' J7 PULSE AMPLIFIER CIRCUIT DIAGRAM FIG. A1.8 X I C3 1 C 6 R12 : L C4 S R 1 3 C 5 T fRU J10 C8 + 5V CATHODE PULSE 04 >K • R15 D4 H>l— R17 C9 05 R19 - f R20 1 . 0 7 CATHODE MODULATOR CIRCUIT DIAGRAM FIG. A1.9 92 to t r a n s i s t o r Q5. T r a n s i s t o r Q5 i s the f i n a l stage of pu l s e a m p l i f i c a t i o n . Q5 i s a h i g h - g a i n , high-power t r a n s i s t o r with c o l l e c t o r l o a d i n c l u d i n g r e s i s t o r R1 and the f i r s t t r i o d e cathode. A1.2.3 THE £.3?. CHAIN The H.F. chain d e r i v e s the c a r r i e r and l o c a l o s c i l l a t o r f r e q u e n c i e s by m u l t i p l y i n g the frequency of a 120 MHz c r y s t a l o s c i l l a t o r . The c h a i n can develop 4 KW output power i n t o 50 at 840 MHz. THE 120MHZ OSCILLATOR-AMPLIFIES The b a s i c 120 MHz r e f e r e n c e frequency i s generated by a TTL compatible 120 MHz modular c r y s t a l o s c i l l a t o r ( F i g . A1.10). The f i r s t stage o f R.F. a m p l i f i c a t i o n uses t r a n s i s t o r Q13 as a tuned a m p l i f i e r , o p e r a t i n g c l a s s AB. T h i s i s f o l l o w e d by three stages -of tuned R.F. a m p l i f i c a t i o n u s i n g t r a n s i s t o r s Q16, Q15 and Q14. A l l three a m p l i f i e r s operate c l a s s C. The f i r s t c l a s s C a m p l i f i e r uses s t r i p l i n e components i n i t s tuned c i r c u i t . X6, X7 MULTIPLIERS The 120 MHz output power d r i v e s the n o n l i n e a r v a r a c t o r diode D9- ( F i g . A1.11). The s i x t h and seventh harmonics are i s o l a t e d by s t r i p l i n e tuned c i r c u i t s . The s i x t h harmonic i s AAA/ f D8 R40 AAAr R44 C41 L U C 3 9 R41 S L 8 R42 -QT3 C 4 2 ^ I^MT1" R 4 8 ^ C 4 6 7 | C 4 7 K L 1 8 C48. R48 26 V C37 C55 zz/ X R43 >L9 L10 C40 L U C50 Q16 _ I_C49 C53 R45 AAAr L16 J - C 4 3 R46 LEAD ' LEAD I Q15 C51- ) R39 R.F. OUT R 49 1 2 0 M H z OSCILLATOR - AMPLIFIER CIRCUIT DIAGRAM FIG.A1.10 V C56 L20 L21 L23 J ^ C 5 9 X C 6 ° D9 R50 C57 x7 MULTIPLIER - C61 C58 R.F. OUT J4 — C62 C63 *6 MULTIPLIER 1 C64 720 MHz J3 BP. FILTER - TO L.O. x6. *7 MULTIPLIER CIRCUIT DIAGRAM FIG. A1.11 95 f u r t h e r f i l t e r e d by a 720 MHz bandpass f i l t e r . At t h i s p o i n t the 720 MHz power l e v e l i s 160 mW. This p r o v i d e s the l o c a l o s c i l l a t o r power to the r e c e i v e r . 840MHZ R.F AMPLIFIER The 840 MHz seventh harmonic from the m u l t i p l i e r i s f u r t h e r a m p l i f i e d through two stages of tuned common-base a m p l i f i c a t i o n using t r a n s i s t o r s Q11 and Q12 ( F i g . A1.12). The pulse a m p l i f i e r gates the f i r s t stage by s w i t c h i n g the c o l l e c t o r c u r r e n t on and o f f . The output power of the s o l i d s t a t e R.F. a m p l i f i e r s e c t i o n i s 20 W. I t i s i s o l a t e d from the t r i o d e a m p l i f i e r s e c t i o n by a f e r r i t e i s o l a t o r . The high-power R.F. a m p l i f i e r ( F i g . A1.13) uses two microwave c a v i t y t r i o d e a m p l i f i e r s . The cathode modulator gates the f i r s t t r i o d e a m p l i f i e r by s w i t c h i n g the DC l e v e l on the cathode. T h i s switches the t r i o d e out of and back i n t o c u t o f f . The c e n t r e f r e q u e n c i e s and Q» s of the t r i o d e a m p l i f i e r s are s e t by a d j u s t i n g t h e i r c a v i t y c o n f i g u r a t i o n s . The outpu>t pawer of the R.F. c h a i n i s 4 KW. I t i s again i s o l a t e d by a f e r r i t e i s o l a t o r and attached t o the R.F. output connector. J7 Y + 26 V IN 'HP R35 WALL TO PULSE AMR R34 1 " T C 2 ' C19 C20 ' I +1 C22 L1 C2U ) C23 H i - R.F. IN (from x7) r _ . L3 011 v r ~ C29 «<L4 C27 if C 2 V V L2 C31 / F C 3 2 Q12 N / / G 3 3 \ / i L5 _ L C28 R.F. OUT TO ISOLATOR . J L C34 71- 7TC35 J6 840 MHz R.F. AMPLIFIER CIRCUIT DIAGRAM FIG. A1.12 97 L.O. J3 R.F OUTPUT 1 L • 30 VDC 5 A REGULATOR 26V MAIN POWEI TIMING LIGHT H L U TRIODE AMP. 8757 or 8874 A Y641 1.5A ' 91 V R2 W v r ~ 30W | PEAK 2000 V « 1 LU J6 DM20-28 4 W 1. 3 A 84 0 MHz AMPLIFIER LU CATHODE MOD. > I to < GO < o CN P O W E R SUPPLY TIMING LIGHT R 3 • 5V l _ _ J4 1 840 MHz x 7 B P . FILTER 720MHz M U L T I P L I E R x 6 MULT I J 2 A OSM "1 J 1 B12-28 P U L S E 120 MHz N S O U R C E B3-28 TRANSMITTER BLOCK DIAGRAM OSCILLATOR 2N3866 2N3866 FIG: A1.13 j 98 Table A l : Power Connector Pin D e s i g n a t i o n s DC POWEB INPUT I +30 V o l t s J - Return MONITOR TEST POINTS A Spare B, C Filament #1 D, E Filament #2 F HV Monitor G Reset L i n e H B i a s Voltage 99 Table A2: T r a n s m i t t e r : Required Major Components Y518 C a v i t y T r i o d e Y641 C a v i t y T r i o d e 840 MHz I s o l a t o r , 5 KW Peak 840 MHz I s o l a t o r , 30w Peak 120 MHz O s c i l l a t o r I n t e g r a t e d C i r c u i t s : SN5410 TTL T r i p l e 3-NAND (x3) SN5473 TTL Dual J-K F l i p - f l o p SN7493A TIL 4 - b i t Binary Counter (x2) SN54123 TTL Dual Monostable V i b r a t o r MC4324 TTL Dual Voltage C o n t r o l l e d M u l t i v i b r a t o r SE555V MOS L i n e a r Timer 100 Table A3: T r a n s m i t t e r : D i s c r e t e Components P a r t s L i s t Q1 MPS-U06 Q23 2N2907 Q2 2N5883 Q24 MPS-U57 Q3 MPS-U57 Q25 MPS-U07 Q4 2N3009 Q26 2N4264 Q5 2N5430 Q27 MPS-007 Q6 2N4264 Q28 2N4264 Q7 2N3009 Q29 MPS-007 Q8 MPS-3640 Q30 2N4264 Q9 2N3720 Q31 MPS-007 Q10 2N300 9 Q32 2N4264 Q11 D5-28B D1 1N5251 Q12 DM20-28B D2 1N4007 Q13 2N3866 D3 1N4007 Q14 B12-28 D4 1N914 Q15 B3-28 D5 1N5231 Q16 2N3866 D6 1N5253 Q17 2N2222 D7 1N4732 Q18 2N2222 D8 1N5240 Q19 2N3055 D9 VAB-810 Q20 2N3055 D10 1N4007 Q21 2N3055 D11 1N5246 Q22 2N3055 D12 1N5230 D13 1N4007 D14 1N4007 D15 1N4007 D16 1N4007 D17 1N4007 D18 1N4007 D19 1N-5377 D20 USE-60 D21 USE-60 D22 100S8F D23 100S8F D24 100S8F D25 100S8F D26 1N4754 D27 1N4007 D28 1N5234 D29 1N5230 D30 1N914 D31 1N914 D32 1N914 D33 1N914 C1 27 u f d , 35 V C2 100 u f d , 5 V C3 10 u f d , 8 V C4 0.1 ufd TABLE A3 CONT. C5 lOOpfd C6 4.7pfd C7 0.05 ufd C8 0.1 ufd C9 0.0033 ufd C10 0.1 ufd C11 0.001 u f d , feedthrough C12 27 ufd, 35 V C13 180pfd C14 0.0033 ufd C15 0.1 ufd C16 0.1 ufd Ci17 0.0022 ufd C18 0.01 ufd C19 0.001 u f d , feedthrough C20 50 ufd, 50 V C21 50 ufd, 50 V C22 22pfd, feedthrough C23 0.1 ufd C24 0.001 u f d , feedthrough C25 7.5pfd C26 1-10pfd, v a r i a b l e C27 1-10pfd, v a r i a b l e C28 390pfd C29 1-10pfd, v a r i a b l e TABLE A3 CONT. C30 1-10pfd, v a r i a b l e C55 200pfd C31 1-10pfd, v a r i a b l e C56 75pfd C32 1-10pfd, v a r i a b l e C57 0.1-3pfd, v a r i a b l e C33 7.5pfd C58 1-10pfd, v a r i a b l e C34 1-10pfd, v a r i a b l e C59 95pfd C35 1-10pfd, v a r i a b l e C60 300pfd C36 0.001 ufd, feedthrough C61 1-10pfd, v a r i a b l e C37 0.001 ufd, feedthrough C62 1-10pfd, v a r i a b l e C38 50 ufd, 50 V C63 0.1-3pfd, v a r i a b l e C39 0.001 ufd, feedthrough C64 1-10pfd, v a r i a b l e C40 27pfd C65 22 ufd, 20 V C41 24pfd, s e l e c t e d C66 15 ufd, 35 V C42 S e l e c t e d C67 50 ufd, 50 V C43 60pfd C68 22 ufd, 35 V C44 65pfd C69 18 ufd, 150 V C45 450pfd C70 18 ufd, 150 V C46 20pfd C71 0. 1 ufd, 5 KV C47 0.001 ufd, feedthrough C72 22 ufd, 35 V C48 20pfd C73 22 ufd, 35 V C49 1-10pfd, v a r i a b l e C74 0.1 ufd, 3 KV C50 51pfd C75 3.9 ufd,10 V C51 1-10pfd, v a r i a b l e C76 0.015 u f d , 100 V C52 270pfd C77 910pfd, 20 V C53 0.001 ufd, feedthrough C78 91pfd, 20 V C54 26pfd C79 3.9 ufd, 10 V C80 3.9 u f d , 10 V C81 3.9 u f d , 10 V C82 3.9 u f d , 10 V L1 RF choke L2 3 Turns L3 2 Turns L4 3.5 Turns L5 1 Turn L6 BF choke L7 8 Turns L8 6 Turns L9 8 Turns L10 3 Turns (leads) L11 3 Turns (leads) L12 2 Turns L13 3/4 Turns L14 5 3/4 Turns L15 3 Turns L16 0.02 uh L17 6 Turns L18 8 Turns L19 S e l e c t e d L20 0.02 uh L21 0.0058 uh L22 0.022 uh 103 TABLE A3 CONT. L23 RF choke R1 150 0.5w, 10% R2 0103 Ohmite 3 12w R3 0103 Ohmite 3 12w R4 2.25 , 12w R5 2. 25 , 12w R6 2. 25 , 12w R7 200 v a r i a b l e R8 4.7, 12w R9 4.7, 12w R10 200 0.5w, 10% R11 62 0.5w, 10% B12 56 0.5w, 10% B13 150 0.5w, 10% B14 Se l e c t e d B15 500 v a r i a b l e B16 2K v a r i a b l e R17 470 0.5w, 10% R18 470 0.5w, 10% R19 270 0.5w, 10% R20 10 0.5w, 10% R21 330 0.5w, 10% R22 56 0.5w, 10% R23 1800 0.5w, 10% R24 1800 0.5w, 10% TABLE E25 270 0.5w, 10% E26 1 0.5w, 10% E27 470 0.5w, 10% E28 2K v a r i a b l e B29 500 v a r i a b l e E30 100 0.5«, 10% E31 1K 0.5w, 10% E32 330 0.5w, 10% E33 510, 5%, 2w E34 0.39, wirewound E35 33 0.5w, 10% B36 22K 0.5w, 10% E37 22K 0.5w, 10% B38 22K 0.5w, 10% E39 22K 0.5w, 10% E40 12K 0.5w, 10% B41 390 0.5w, 10% R42 68 0.5w, 10% B43 68 0.5w, 10% B44 5.6K 0.5w, 10% B45 6.8 0.5w, 10% B46 10 0.5w, 10% B47 10 0.5w, 10% E48 270 0.5w, 10% B49 220 0.5w, 10% A3 CONT. B50 Sele c t e d B51 1K 0.5w, 10% E52 68K 0.5w, 10% B53 1K 0.5w, 10% B54 68K 0.5w, 10% B55 1K 0.5w, 10% E56 680 0.5w, 10% B57 1.2K 0.5w, 10% E58 22K 0.5w, 10% B59 47K 0.5W, 10% B60 4.7K 0.5w, 10% B61 270-430 BH8-5W E62 27K, 2w E63 470 0.5w, 10% B64 4.5M 0.5w, 10% B65 4.5M 0.5w, 10% B66 2M 0.5h, 10% B67 2M 0.5w, 10% B68 2M 0.5w, 10% B69 2fi 0.5w, 10% B70 1200 5w B71 89PE 5K r v a r i a b l e B72 2.7K 0.5w, 10% B73 42 r 25w B74 91T 20K, v a r i a b l e TABLE A3 CONT. R75 91T 20K, v a r i a b l e R86 100 0.5w, 10% R76 1K.0.5W, 10% R87 1K 0.5w, 10% R77 4.5M 3w R88 100 0.5w, 10% R78 89PR-25K, v a r i a b l e . . R89 1K 0.5w, 10% R79 1K 0.5w, 10% R90 10 0.5w, 10% R80 47K 0.5w, 10% R91 100 0.5w, 10% R81.31T-20K, v a r i a b l e R92 10.0.5w, 10% R82 91T-20K, v a r i a b l e R93 1K 0.5w, 10% R83 10K 0.5wf 10% R94 100 0.5w, 10% R84 5.6K 0.5v, 10% R95 1K 0.5w, 10% R85 10 0.5w, 10% R96 10 0.5w, 10% Other Components: 2 T o r o i d a l Transformers 1 720 MHz Bandpass F i l t e r 1 30 V, 5A C i r c u i t Breaker 1 28 V, Tungsten Panel Lamp 106 A1.3 THE RECEIVER The r e c e i v e r f o r the r a d i o echo sounder ( F i g . A1.14) i n c l u d e s a l l the c i r c u i t r y r e q u i r e d to perform two b a s i c a l l y independent f u n c t i o n s . One p a r t of the r e c e i v e r i s the a c t u a l r a d i o frequency r e c e i v e r - a heterodyne r e c e i v e r , d e t e c t o r and video a m p l i f i e r . The second part i n c l u d e s a l l the d i g i t a l c i r c u i t r y r e q u i r e d t o t r i g g e r the t r a n s m i t t e r and to c o n t r o l an o s c i l l o s c o p e , the l a t t e r p r o v i d i n g both a d i s p l a y and photographic r e c o r d i n g c a p a b i l i t y . Since these two f u n c t i o n s are independent (and s i n c e f u t u r e v e r s i o n s of the r a d i o echo sounder w i l l c e r t a i n l y s p l i t these f u n c t i o n s i n t o two u n i t s ) t h e i r d e s c r i p t i o n s have been separated. A1.3.1 THE R.F. CHAIN AND VIDEO AMPLIFIER A1.3.1.1 PHYSICAL DECRIPTION The RF c o n v e r t i n g and a m p l i f y i n g c h a i n i n c l u d e s s i x modular components; a diode l i m i t e r , mixer, I.F. f i l t e r , l o g a r i t h m i c I.F. a m p l i f i e r - d e t e c t o r and two 6 dB.passive a t t e n u a t i n g d e v i c e s (PAD'S). A l l of the components are contained i n a l a r g e r module (the RF module, s e e . F i g . A1.14) which can be removed from the r e c e i v e r by removing t h e . f o u r r e t a i n i n g screws around the RF i n p u t s . The video a m p l i f i e r i s the o n l y component o f the RF-video chain which i s not modular s i n c e i t i s used with d i s c r e t e components as b i a s and gain c o n t r o l s . The video a m p l i f i e r FIG. A L U RECEIVER PICTORIAL DIAGRAM o 108 shares space on a p r i n t e d c i r c u i t board with two DC-DC co n v e r t e r s and th r e e v o l t a g e r e g u l a t o r s . One c o n v e r t e r p r o v i d e s ±15 VDC f o r the video a m p l i f i e r and +15 V f o r the CMOS l o g i c c i r c u i t r y . Two vol t a g e r e g u l a t o r s reduce these t o ±12 VDC r e q u i r e d f o r the l o g . IF a m p l i f i e r - d e t e c t o r . The second c o n v e r t e r and t h i r d r e g u l a t o r provide +5 VDC r e q u i r e d by the high speed TTL l o g i c c i r c u i t r y used t o d r i v e the t r a n s m i t t e r t r i g g e r and by the f r o n t panel d i s p l a y s . A1.3.1.2 CIRCUIT DESCRIPTION R.F. CIRCUITRY Th i s d e s c r i p t i o n t r a c e s the s i g n a l s t a r t i n g from the RF i n p u t . Refer t o f i g u r e A1.15. The RF i n p u t i s p r o t e c t e d a g a i n s t o v e r l o a d by a s o l i d s t a t e diode l i m i t e r (DL1). The l i m i t e r a l l o w s any s i g n a l up to 50 mW t o pass through i t e f f e c t i v e l y unattenuated. Any power a p p l i e d to the l i m i t e r i n excess o f 50 mW i s absorbed by the l i m i t e r . S a t u r a t i o n of the l i m i t e r normally occurs each time as RF t r a n s m i s s i o n occurs e i t h e r because o f a d i r e c t wave between two antennae o r because of power r e f l e c t e d i n the antenna feed back through the c i r c u l a t o r . The diode l i m i t e r i s capable of withstanding overloads i n excess of 4 KW i n the event of a c i r c u l a t o r f a i l u r e or a c a b l e f a i l u r e while o p e r a t i n g with a s i n g l e antenna. Less than 0.1 erg of high l e v e l energy w i l l pass through the l i m i t e r b e f o r e i t ach i e v e s a s a t u r a t e d s t a t e . The diode l i m i t e r RF IN > DIODE LIMITER DL 1 RF N ^ S M A MIC MIXER M 1 IF LO IN > S M A 6 dB PAD 6 dB PAD 4> t BANDPASS FILTER BP 1 LO S M A 1 IF VIDEO OUT > — e - S M A LOG IF AMPIFIER A 1 •G- S M A + 12v -12v RF M O D U L E ; CONNECTION DIAGRAM FIG. A1.15 110 r e q u i r e s 100ns to recover from s a t u r a t i o n . From the diode l i m i t e r the BF s i g n a l passes to a double- balanced miniature i n t e g r a t e d c i r c u i t mixer (M1) which c o n v e r t s the s i g n a l to the 120 MHz i n t e r m e d i a t e frequency ( I . F . ) . . Power for the c o n v e r s i o n i s provided by the t r a n s m i t t e r v i a the f r o n t panel l o c a l o s c i l l a t o r (L.0.) connector. The L.0. i n p u t power l e v e l from the t r a n s m i t t e r i s 160 mW (+22 dBm) . 12 dB of a t t e n u a t i o n reduces the l e v e l t o 10 mW (+10 dBm), the l e v e l r e q u i r e d at the mixer L.O. i n p u t . The c o n v e r s i o n l o s s i n the mixer i s approximately 9.3 dB at low BF l e v e l s . The 1 dB compression l e v e l i s approximately +8 dBm of EF i n p u t power. Since 50 mW (+17 dBm) i s the maximum output power of the diode l i m i t e r the maximum I.F. power l e v e l a t t a i n a b l e i s l i m i t e d by both the L.O. power l e v e l and the diode l i m i t e r t o about 4 mW (+6 dBm). At t h i s l e v e l the d i s t o r t i o n product power l e v e l i s a s i g n i f i c a n t f r a c t i o n of the fundamental I.F. power l e v e l . The I.F. s i g n a l passes through a passive f i l t e r to the I.F. a m p l i f i e r . The f i l t e r e l i m i n a t e s any video feedthrough from the diode l i m i t e r as we l l as removing c o n v e r s i o n products and overtones coming from the mixer. The 3 dB pass band o f the f i l t e r i s 99 MHz to 141 MHz. The f u l l f i l t e r c h a r a c t e r i s t i c i s reproduced i n F i g u r e A1.16. The I.F. a m p l i f i e r i s the c e n t r a l component of the r e c e i v e r . S p e c i f i c a l l y designed by BHG E l e c t r o n i c s Lab. Inc. f o r a i r b o r n e radar systems i t was f a b r i c a t e d u s i n g t h i n f i l m s o l i d s t a t e h y b r i d technology. I t s key f e a t u r e i s i t s l o g a r i t h m i c compression c h a r a c t e r i s t i c with a u s e f u l dynamic range from -70 dBm to +10 dBm ( F i g . &1.17). The a m p l i f i e r 111 i 1——i 1 1 1—~~i r FREQUENCY (MHz) FIG.A1.16 I.F FILTER BANDPASS CHARACTER oO°° oooooooooooo I I I I 1 1 1 1 1 J -80 -70 -60 -50 -40 -30 -20 -10 0 10 20 I.F INPUT POWER (dBm) FIG. A1.17 CONTINUOUS WAVE CHARACTERISTIC OF LOG. I.F. AMPLIFIER AT 120 MHz 113 p r o v i d e s a detected output s i g n a l . T h i s s i g n a l , the b a s i c video s i g n a l , v a r i e s from 0.56 V at an I.F. l e v e l of -70 dBm (100 pW) to 2.84 V a t +10 dBm. The l o g a r i t h m i c accuracy i s w i t h i n ±1 dB over more than 70 dB of dynamic range. The a m p l i f i e r 3 dB bandwidth i s 40.1 MHz at a c e n t r e freguency of 120 MHz. The a m p l i f i e r output r i s e t i m e i s l e s s than 20 ns. The I.F. a m p l i f i e r i s the only component i n the BF module r e q u i r i n g DC power. I t uses +12 VDC at 60 mA and -12 VDC a t 130 mA. Both voltages' are generated on the power supply - v i d e o a m p l i f i e r board and are provided t o the I.F. a m p l i f i e r v i a jumpers to the EF module. The b a s i c video s i g n a l i s l e d by c o a x i a l jumpers t o both a f r o n t panel connector (V) and to the video a m p l i f i e r i n p u t . The video a m p l i f i e r ( F i g . A1.18) i s needed t o c o n d i t i o n the video s i g n a l f o r modulation of an o s c i l l o s c o p e phosphor i n t e n s i t y , making the image s u i t a b l e f o r continuous photographic r e c o r d i n g . The prime requirement of the a m p l i f i e r i s a l a r g e bandwidth. The o p e r a t i o n a l a m p l i f i e r used here (Burr Brown 3400A), a m o n o l i t h i c h y b r i d a m p l i f i e r , e x c e l s a t t h i s task having a f u l l power bandwidth of 30 MHz and an output slew r a t e of 1000 V u s - 1 . The a m p l i f i e r i s c o n f i g u r e d as an i n v e r t i n g a m p l i f i e r ( r e q u i r e d by the T e k t r o n i x 475 Z input) . E48 i s the b i a s adjustment (Figure C5) and E49 i s the gain adjustment of the a m p l i f i e r . Power f o r the a m p l i f i e r i s drawn from the 24 VDC to ±15 VDC c o n v e r t e r which i s on the same board as the a m p l i f i e r . V I D E O OUT 115 POWEB SUPPLY The r e c e i v e r power supply provides f i v e DC v o l t a g e s , ±15 V, ±12 V and +5 V. A Burr-Brown model 528 DC-DC c o n v e r t e r p r o v i d e s the ±15VDC from the 24 V to 28 V i n p u t , with 200mA maximum output before c u r r e n t l i m i t i n g goes i n t o e f f e c t . The ±12 V s u p p l i e s are d e r i v e d from the ±15 V s u p p l i e s by two three p i n r e g u l a t o r s , a 78M12 f o r the +12 V supply and a 79M12 f o r the - 12 V supply. The +5 V supply uses a separate discrete-component DC-DC c o n v e r t e r , with a maximum output of 1 A. An a s t a b l e o s c i l l a t o r c o n s t r u c t e d from two NOB gates, two c a p a c i t o r s (C11 and C12) and two r e s i s t o r s (B45 and B46) pr o v i d e s a 400 Hz biphase c l o c k to a l t e r n a t e l y s w i t c h on and* o f f t r a n s i s t o r s Q3 and Q4. This s w i t c h i n g r e s u l t s i n a pure AC square wave on the primary of transformer L1. The output square wave i s r e c t i f i e d i n a f u l l wave b r i d g e and f i l t e r e d by c a p a c i t o r C10. At t h i s p o i n t the DC voltage may vary from +7 V to +9 V dependng on the i n p u t power l e v e l . A th r e e p i n r e g u l a t o r (7805, TO-220) drops the supply l e v e l to +5 V. Cu r r e n t l i m i t i n g goes i n t o e f f e c t a t 1 A. A1.3.2 BECEIVEB DIGITAL CIBCUITBY The f u n c t i o n of the d i g i t a l l o g i c c i r c u i t r y i s t o provide the c o n t r o l s i g n a l s necessary f o r the setup, d i s p l a y and r e c o r d i n g of the r a d i o echo sounder s i g n a l on an i n t e n s i t y modulated o s c i l l o s c o p e phosphor. The task can be d i v i d e d i n t o two areas: the ge n e r a t i o n and s y n c h r o n i z a t i o n of a setup 116 s t a i r c a s e (grey s c a l e ) and b i n a r y time s i g n a l (frame code) with the video s i g n a l ; the slow scanning of the o s c i l l o s c o p e t r a c e v e r t i c a l l y a c r o s s the screen and the s e l e c t i o n of the grey s c a l e , frame code or video s i g n a l . The c i r c u i t r y f o r each area has been implemented on i n d i v i d u a l p r i n t e d c i r c u i t boards. The former, c a l l e d high speed l o g i c , operates with a 1 MHz c l o c k freguency, the l a t t e r , c a l l e d low speed l o g i c , operates with a c l o c k freguency which i s a sub m u l t i p l e of 68 Hz. The two boards operate asynchronously and communicate v i a c o n n e c t i o n s to a f o u r t y conductor f l a t c a b l e buss. HIGH SPEED LOGIC The b a s i c 1 MHz c l o c k frequency i s d e r i v e d u s i n g two CMOS i n v e r t e r s and RC r e l a x a t i o n o s c i l l a t o r c i r c u i t r y (R32, R33, R73, C7, C8) ( F i g . A1.19), ( F i g . A1.20). The frequency i s a d j u s t e d by R33 (pulse r e p e t i t i o n r a t e a d j u s t ) . The o s c i l l a t o r i s not temperature compensated so th a t the 1 MHz frequency should not be used as a t i m i n g r e f e r e n c e . The c l o c k freguency i s d i v i d e d by 128 through seven stages of a b i n a r y r i p p l e counter (4040) ( F i g . A1.21). The grey s c a l e and frame code are d e r i v e d u s i n g output b i t s 1 through 4. Output b i t 7 d e f i n e s the t r a n s m i t t e r pulse r e p e t i t i o n r a t e . When b i t 4 i s high both the grey s c a l e and the frame code are d i s a b l e d . When b i t 4 i s low b i t s 1, 2 and 3 each t r a n s l a t e through a NOR gate and an i n v e r t e r t o d r i v e a three b i t r e s i s t o r - l a d d e r d i g i t a l t o analogue c o n v e r t e r (R34, R35, R36, 7 BIT COUNTER 1 4 0 4 0 enable 0 0 9 3 bit D/A resistor ladder PULSE GENERATOR DUAL LINE DRIVER 54121 54S140 4051 8 CHANNEL MULTIPLEXER ^ 7K Frame Code parallel Grey Scale 4066 J , Frame Code serial Trig Trig 9 - 16 VIDEO MIXER I VIDEO IN MIXED VIDEO OUT grey scale enable 31 frame code enable 32 video enable 37 H I G H SPEED L O G I C ; L O G I C D I A G R A M FIG. A1.19 118 R31 D7 14 4 0 6 9 R35 S R 3 6 R37 •vAAA—W\AA- R38 P39 54 S 140 5v TRIG 14 541 21 R41 R40 C9 4>n TRIG DISABLE M I X E D V IDEO VIDEO 14 4 0 0 1 L I 1 4 4 0 6 6 R42 4 0 4 0 1 6 4 0 5 1 HIGH SPEED L O G I C ; C I R C U I T D I A G R A M N r - (N n n n FIG. A1.20 71 °"' " t 1 5 v M A R K S imhz iiiriJinjiJWLjmjLn̂ FRAME CODE FIG. A1.21 HIGH SPEED LOGIC TIMING DIAGRAM 1 120 R37, R38 and R39). The output i s b u f f e r e d by high speed s w i t c h i n g t r a n s i s t o r Q2 and r e s i s t o r R40. The b u f f e r e d grey s c a l e i s switched as r e q u i r e d onto the mixed video l i n e by a b i l a t e r a l analoque CMOS switch (4066). When b i t 4 i s hiqh a l l t h r e e s i g n a l s d r i v i n g the D/A c o n v e r t e r a l s o go high r e s u l t i n g i n the grey s c a l e output being at i t s h i g h e s t value. T h i s high l e v e l s i g n a l would blank the o s c i l l o s c o p e phosphor. The same th r e e s i g n a l s t h a t d r i v e the D/A co n v e r t e r , except f o r o p p o s i t e p o l a r i t y , a l s o d r i v e the channel s e l e c t l i n e s on an ei g h t channel m u l t i p l e x e r (4051). T h i s analogue m u l t i p l e x e r has been used to t u r n incoming i n f o r m a t i o n on e i g h t f l a t c a b l e l i n e s (9-16) i n t o the frame code. Each s i g n a l i s s e l e c t e d i n tu r n f o r one usecond by the sequence of b i n a r y numbers determined by the counter b i t s 1, 2 and 3. When b i t 4 i s high the m u l t i p l e x e r output i s f o r c e d t o a low v o l t a g e , which a f t e r being i n v e r t e d w i l l blank the o s c i l l o s c o p e phosphor. As with the grey s c a l e , the m u l t i p l e x e d frame code i s switched as re q u i r e d onto the mixed video l i n e by a b i l a t e r a l analoque CMOS swi t c h (4066). The video s i g n a l which comes from the video a m p l i f i e r onto the card v i a the edge connector i s a l s o switched onto the mixed video l i n e by an analogue CMOS switch. When l i n e . 3 7 on the f l a t c a b l e buss i s high the video s i g n a l passes onto the mixed video l i n e . When l i n e s 31 or 32 go high the grey s c a l e or frame code r e s p e c t i v e l y pass onto the mixed video l i n e . No two of the en a b l i n g l i n e s can go high s i m u l t a n e o u s l y . The l e a d i n g edges of the grey s c a l e and frame code, which both s t a r t on the down t r a n s i t i o n of the counter b i t 4, are synchronized with the t r a n s m i t t e r t r i g g e r pulse which i s s t a r t e d 121 by an up t r a n s i t i o n on counter b i t 7 ( F i g . A K 2 2 ) . In t h i s way the t r a n s m i t t e r r e p e t i t i o n p e r i o d i s 128 useconds, w i t h i n i t s duty c y c l e s p e c i f i c a t i o n . The t r a n s m i s s i o n pulse l e n g t h i s determined by the c y c l e time o f a monostable m u l t i v i b r a t o r . The 15 V b i t 7 t r a n s i t i o n i s reduced t o a 0-5 V t r a n s i t i o n by r e s i s t o r E31 and Zener diode D7. The r i s i n g edge t r i g g e r s a TTL monostable v i b r a t o r (54121) with r e s i s t o r R41 and s i l v e r mica c a p a c i t o r C9 determining the pulse l e n g t h . The i n v e r t e d output of the m u l t i v i b r a t o r d r i v e s the i n p u t s of a dual i n v e r t i n g l i n e d r i v e r (54S140). The output pulse from the l i n e d r i v e r s are a d j u s t a b l e from 50 ns to 200 ns. They are each capable of d r i v i n g a 5 0 i l l i n e at TTL l e v e l s . One output i s dedi c a t e d as the t r a n s m i t t e r t r i g g e r . The other i s a v a i l a b l e as a t r i g g e r f o r any other instrument. LOW SPEED LOGIC The h e a r t of the low speed l o g i c ( F i g . A1.23) i s a ramp generator comprising a v a r i a b l e c l o c k , t e n - b i t counter and a n i n e - b i t D/A c o n v e r t e r . The ramp output v a r i e s at a co n s t a n t r a t e from 0 V through 15 V over one o f e i g h t b i n a r y m u l t i p l e s of 15 seconds. The ramp provides a means of scanning an i n t e n s i t y modulated o s c i l l o s c o p e t r a c e v e r t i c a l l y a c r o s s the sc r e e n , c o n t i n u o u s l y exposing a frame o f f i l m . At the end o f each v e r t i c a l scan the ramp r e s e t s to 0 V and waits f o r an op e r a t o r - s u p p l i e d r e s t a r t s i g n a l . The b a s i c c l o c k r a t e i s determined by r e s i s t o r s B26, R28, f *| 16JJS Q( i n n Q5 ~L Q6 Q7 1 GREY SCALE FRAME CODE Tx TRIG. wYinnnnnnnnnr VIDEO I" 50 nS 128 pS k k FIG. A1.22 HIGH SPEED LOGIC TIMING DIAGRAM 2 rO 123 1 - 8 15 v to 5 v BUFFER 2 x 4010A Ramp Grey scale En 8 bit frame counter clock 9 bit D/A res istor ladder bit 5 r / v W - i 15 h / v W n bits 1- 9 XR 2240 6 8 Hz clock & 8 bi t counter Rs bit 10 10 bit counter 4 0 4 0 RESET < 17 RUN clock -< 3 6 clock 18 START < 1 9 2 1 - 2 8 STOP READY • ^ 3 0 < 2 9 - < 2 0 L O W SPEED L O G I C ; L O G I C D I A G R A M FIG. A1.23 124 c a p a c i t o r C6 and l i n e a r c i r c u i t r y i n the 2240 t r i g g e r a b l e i n t e g r a t e d t i m e r c i r c u i t ( F ig. A1.24). The 2240 timer i n c l u d e s an e i g h t - b i t b inary counter with open c o l l e c t o r outputs. V i a f l a t c a b l e buss l i n e s 21 to 28, the f r o n t panel switch S1 s e l e c t s one of these outputs to c l o c k the ten b i t counter (4040)- The c l o c k input to the counter i s on the r e t u r n l i n e from S1 ( f l a t cable l i n e 20) along with p u l l - u p r e s i s t o r R23. The f a s t e s t c l o c k freguency generated by the 2240 timer i s approximately 68Hz. T h i s corresponds t o a t o t a l v e r t i c a l scan time of about 15 seconds. Each s u c c e s s i v e output i s at e x a c t l y h a l f the p r e v i o u s frequency r e q u i r i n q twice the t o t a l v e r t i c a l scan time. The e i g h t scan times a v a i l a b l e are 15s, 30s, 1m, 2m, 4m, 8m, 16m and 32m. The scan c y c l e i s as f o l l o w s . k r i s i n g edge on the " s t a r t " l i n e ( f l a t c a b l e l i n e 19) passes through diode D2 and c a p a c i t o r C2 t o s e t a monostable v i b r a t o r comprising two NOB g a t e s , c a p a c i t o r C1 and r e s i s t o r B1 ( F i g . A1.25). . In a d d i t i o n the " s t a r t " pulse t r i g g e r s through r e s i s t o r B27 the 2240 timer i n t o c o u n t i n g mode, s e t s o r r e s e t s two other b i s t a b l e f l i p - f l o p s and r e s e t s the scan counter (4040). The two f l i p - f l o p s are each formed from two NOR gates. The f l i p - f l o p which i s s e t has i t s output connected to the "grey s c a l e enable" l i n e ( f l a t c a b l e l i n e 31). The f l i p - f l o p which i s r e s e t has i t s output connected to the "video enable" l i n e ( f l a t c a b l e l i n e 33). The output of the monostable v i b r a t o r i s connected to the c l o c k of an e i g h t - b i t counter which s u p p l i e s the frame code i n f o r m a t i o n t o the high speed l o g i c m u l t i p l e x e r . J u s t a f t e r the s t a r t p u l s e , then, the frame'counter i s 125 .<0 K 00<O •- — — n START (19) Q10 READY (29) CLOCK (20) Q1 Q2 Q3 Q4 inniiririjijijî m ~ L j i _ r i _ r i J i J i j a j ~ L ^ GREY SCALE f ENABLE (31) J FRAME CODE ENABLE (32) - VIDEO 1 ENABLE (33) L FIG. A1.25 LOW SPEED LOGIC TIMING DIAGRAM 1 CO 127 incremented by one count, the grey s c a l e i s enabled and the video and frame code are d i s a b l e d . The 10- b i t scan counter proceeds t o count up from hex'OOO'. The output of b i t 10 i s low which t u r n s o f f t r a n s i s t o r Q1 and depowers "ready" i n d i c a t o r lamp B2. When the scan count reaches hex*010' the high l e v e l on b i t f i v e r e s e t s the f i r s t f l i p - f l o p ( F i g . A1.26). T h i s change d i s a b l e s the grey s c a l e and enables the frame code. When the scan count reaches hex'020 1 the high l e v e l on b i t s i x s e t s the second f l i p - f l o p which enables the video and d i s a b l e s the frame code. When the scan count reaches hex'200' the high l e v e l on b i t ten causes the 2240 timer to stop counting ( v i a diode D5 and r e s i s t o r K29), t r a n s i s t o r Q1 t o s w i t c h on and "ready" lamp B2 to glow ( F i g . A1.27). The D/A r e s i s t o r l a d d e r , which uses only the low order 9 b i t s has retu r n e d t o a 0 V output l e v e l . The frame counter may a l s o be incremented by the f r o n t panel switch S4 which connects f l a t c a b l e l i n e s 18 and 36. In t h i s way a "run" o s c i l l a t o r can increment the counter through diode D1 independent o f the r e s t of the low speed c i r c u i t r y . The counter outputs connect d i r e c t l y t o the high speed frame code m u l t i p l e x e r v i a f l a t c a b l e l i n e s 9 t o 16. In a d d i t i o n , through two 4010A b u f f e r c i r c u i t s the frame count i s provided at TTL l e v e l s on f l a t c a b l e l i n e s 1 to 8. ( I t i s important t o note here t h a t the TTL l e v e l s are r e g u i r e d f o r the f r o n t panel LED d r i v e r c i r c u i t s . At the time t h a t t h i s c i r c u i t was designed no CMOS compatible BCD to seven-segment decoders were a v a i l a b l e . I t i s a l s o important t o note here t h a t the presence of the 401 OA c i r c u i t s as used here f o r c e s the obsolescence of the presented design. The 4010A with separate VDD and VCC are no lon g e r being START J | Q 10 ~~|_ READY J " GREY r SCALE ENABL FRAME CODE E N A B L E ' VIDEO -| E N A B L E J FIG. A1.26 LOW SPEED LOGIC TIMING DIAGRAM —I HI- n n START Q10 READY Q6 Q7 Q8 Q9 CLOCK GREY SCALE ENABLE FRAME CODE ENABLE J l JT VIDEO ENABLE FIG. A1.27 LOW SPEED LOGIC TIMING DIAGRAM 3 130 made s i n c e manufacturers found t h a t there was a tendency f o r the 4010A to l a t c h when powered up i n s p e c i f i c manners. No a l t e r n a t e s are a v a i l a b l e . ) The TTL l e v e l frame count i s decoded at the. f r o n t panel i n t o seven-segment o c t a l by three 9317B c i r c u i t s . The 9317B's d r i v e t h r e e seven-segment LED d i s p l a y s ( F i g . A 1.28) a l l o w i n g the o p e r a t o r to pr e s e t and monitor the frame count. The oper a t o r may a l s o r e s e t the frame count with S4 which connects a high l e v e l s i g n a l onto f l a t c a b l e l i n e 17. FIG. A1.28 • 1 s i in d isable POWER R T T M V F R O N T P A N E L RECEIVER ; C O N N E C T I O N D I A G R A M FIG. A1.29 133 Table A4: Receiver R.F. Module Components DL1 Diode L i m i t e r MD-30T30 #001 Micro-^Dynamics i n c . F l a t leakage 50 mW max. Spike leakage 0.1 erg max. Recovery time 100 ns max. I n s e r t i o n l o s s 0.5 dB max. M1 Double Balanced Mixer MA-1 M i n i - C i r c u i t s Laboratory I n s e r t i o n l o s s 9.0 - 10.0 dB LO l e v e l +10 dB BP1 Bandpass F i l t e r 3B120-120/40-op/o #5267-1 K & L Microwave Inc. Pass band 99 MHz to 141 MHz I n s e r t i o n l o s s 0.4 dB A1 Lo g a r i t h m i c IF A m p l i f i e r ICLT12040 #7-511-1 RflG E l e c t r o n i c s Laboratory Inc. Dynamic range -70 dBm to +10 dBm Pass band 99 MHz to 140 MHz Rise time 20ns max. Log. l i n e a r i t y ±1 dB over 70 dB Output range +0.4 V t o +2.8 V Power r e q u i r e d ±12 V S 130 mA max. 134 Table A5: Receive r Components: Required I n t e g r a t e d C i r c u i t s 7805 +5 VDC Voltage r e g u l a t o r 78M12 +12 VDC Voltage r e g u l a t o r 79M12 -12 VDC Voltage r e g u l a t o r 3400A O p e r a t i o n a l a m p l i f i e r , Burr Brown 4001 CMOS quad NOR gate (x5) 4040 CMOS 12 b i t counter (x3) 4010A l e v e l s h i f t i n g hex b u f f e r (obsolete) (x2) 4051 CMOS analogue m u l t i p l e x e r 4066 CMOS quad b i l a t e r a l analoque s w i t c h 4069 CMOS hex i n v e r t e r 2240 NMOS timer-counter 54121 TTL monostable v i b r a t o r 54S140 TTL d u a l 5-input NAND l i n e d r i v e r 9317B TTL seven segment from BCD d e c o d e r - d r i v e r (x3) MAN3610 LED seven segment d i s p l a y , 0.300", Monsanto (x3) Required Power Module Model 528, 28 V t o ±15 V DC-DC c o n v e r t e r , Burr Brown. 135 Table A6: Beeeiver D i s c r e t e Components P a r t s L i s t Q1 2N4238 D1 1N914 Q2 2N3014 D2 1N914 Q3 2N4238 D3 1N914 Q4 2N4238 D4 1N914 C1 17 u f d , 16 V D5 1N914 C2 17 u f d , 16 V D6 1N914 C3 3.3 u f d D7 5 V Zener, 1w, DO-7 C4 1000 p f d D8 1A s i l i c o n r e c t i f i e r C5 3.3 ufd D9 1A s i l i c o n r e c t i f i e r C6 3.3 u f d D10 1A s i l i c o n r e c t i f i e r C7 470 pfd Odd 1A s i l i c o n r e c t i f i e r C8 470 pfd B1 27K 0.25w, 5% C9 90 pf s i l v e r mica B2 27K 0.25w, 5% C10 47 u f d , 16 V B3 33K 0.25w, 5% C11 1000 pfd E4 100K 0.25m, 5% C12 1000 pfd B5 100K 0.25w, 0.4% C13 22 ufd, 35 V B6 50K 0.25w, 0.4% C14 22 ufd B7 100K 0.25w, 0.8% C15 41 u f d , 16 V E8 50K 0.25w, 0. 8% C16 15 ufd, 35 V B9 100K 0.25w, 1% C17 1 u f d , 250 V B10 I 50K 0.25w, 1% C18 22 ufd, 16 V E11 100K 0.25w, 1% TABLE &6, CONT. B12 50K 0.25w, 1% B36 10K 0.25w, 5% B13 100K 0.25w, 5% B37 10K 0.25w, 5% B14 50K 0.25w, 5% B38 4700 0.25w, 5% B15 100K 0.25w, 5% B39 4700 0.25wr 5% E16 50K 0.25w, 5% B40 470 0.25w, 5% B17 100K 0.25w, 5% B41 2K ten t u r n B18 100K 0.25w, 5% B42 4700 0.25w, 5% B19 50K 0.25w, 0.2% B43 5600 0.25w, 20% B20 100K 0.25w, 0.2% B44 5600 0.25w, 20% B21 100K 0.25w, 0.1% B45 220K 0.25w, 5% B22 50K 0.25w, 0.1% B46 220k 0.25w, 5% B23 10K 0.25w, 5% B47 0.25w, 5% B24 1K 0.25w, 5% B48 10K ten t u r n B25 18K 0.25w, 5% B49 10K ten t u r n B26 10K ten t u r n R50 12K 0.25w, 5% B27 47K 0.25w, 5% B51 1K 0.25w# 5% B28 3900 0.25w, 5% B52 180 0.25w, 5% B29 47K 0.25w# 5% B53 180 0.25w, 5% B30 1M 0.25w# 5% R54 180 0.25w, 5% B31 270 0.25w, 5% B55 180 0.25w, 5% B32 1800 0.25w, 5% (x2) B56 180 0.25w, 5% B33 1K t e n t u r n B57 180 0.25w, 5% B34 10K 0.2 5w, 5% B58 180 0.25w, 5% B35 10K 0.25w, 5% B59 180 0.25w, 5% 137 TABLE A6, CONT. B60 180 0.25w, 5% E71 180 0.25w, 5% E61 180 0.25v, 5% E72 180 0.25w, 5% E62 180 0.25w, 5% L1 106S, Hammond E63 180 0.25w, 5% S1 8 p o s i t i o n r o t a r y , G r a y h i l l R64 180 0.25w, 5% S2 MTA-206SA, Alco E65 180 0.25w, 5% S3 MTA-206S, Alco E66 180 0.25w, 5% S4 MTA-206S, Al c o E67 180 0.25w, 5% S5 push-on, push-off, SPST, E68 180 0.25w, 5% G r a y h i l l E69 180 0.25w, 5% S6 MTA-206TA, A l c o E70 180 0.25w, 5% B1 28 V tungsten panel lamp B2 ; 28 V tungsten panel lamp 138 A 1.4 THE SWITCHING REGULATOR POWER SUPPLY The f o l l o w i n g d e s c r i p t i o n s are excerpted i n p a r t from the ARRL Radio Amateur's Handbook (1975), and from Delco E l e c t r o n i c s A p p l i c a t i o n Note #4 9, (1971). Switching r e g u l a t o r s a r e used when i t i s necessary or d e s i r e d t o minimize power l o s s e s which would otherwise occur i n the s e r i e s pass t r a n s i s t o r with l a r g e v a r i a t i o n s i n i n p u t or output v o l t a g e s . The ba s i c o p e r a t i o n of the s w i t c h i n g r e g u l a t o r , known as the f l y b a c k type, may be understood by r e f e r r i n g t o F i g u r e A1.30a. Assume t h a t the switch i s c l o s e d and that the c i r c u i t has been i n o p e r a t i o n long enough to s t a b i l i z e . The v o l t a g e across the load RL, i s zero, and the c u r r e n t through L i s l i m i t e d o n l y by RI, the i n t e r n a l r e s i s t a n c e of the i n d u c t o r . At the i n s t a n t t h a t the switch i s opened, the volta g e a c r o s s the l o a d goes t o a value higher than the source v o l t a g e , E, because of a s e r i e s - a i d i n g or " f l y b a c k " e f f e c t o f the i n d u c t o r . When the magnetic l i n e s of f l u x about the i n d u c t o r c o l l a p s e completely, the voltage a c r o s s RL w i l l be equal t o t h a t of the source (minus the s m a l l v o l t a g e drop a c r o s s R I ) . Each time the switch i s c l o s e d and then opened, the process i s repeat e d . By opening and c l o s i n g the switch r a p i d l y , v o l t a g e p u l s e s may be a p p l i e d a c r o s s RL which are hi g h e r than the DC i n p u t v o l t a g e . A c a p a c i t o r may be connected ac r o s s RL t o produce a DC output v o l t a g e . To keep the c a p a c i t o r from d i s c h a r g i n g when the switch i s c l o s e d , a diode can be connected i n s e r i e s with the loa d and i t s p a r a l l e l - c o n n e c t e d c a p a c i t o r . In a p r a c t i c a l s w i t c h i n g - r e g u l a t o r c i r c u i t the s w i t c h i n g i s 139 L RI A A / S r IDEAL VOLTAGE SOURCE SWITCH (A) RL + o DC INPUT DRIVER MULTI- VIBRATOR (B) FIG.A1.30 SWITCHING REGULATOR BLOCK DIAGRAM 140 performed by a t r a n s i s t o r , as shown i n Figure A 1.30b. The t r a n s i s t o r may be d r i v e n by any number of c i r c u i t s . In the c i r c u i t used ( F i g . A1.31) f o u r s e c t i o n s make up the d r i v i n g c i r c u i t , as shown i n the b l o c k diagram form i n f i g u r e Al.30b. The o s c i l l a t o r t r i g g e r s the monostable m u l t i v i b r a t o r and determines the freguency of o p e r a t i o n . The sensor measures the output v o l t a g e and c o n t r o l s the pulse width of the m u l t i v i b r a t o r a c c o r d i n g l y . The monostable m u l t i v i b r a t o r combines the s i g n a l s from the o s c i l l a t o r and sensor to produce the c o r r e c t pulse width. The d r i v e r r e c e i v e s the m u l t i v i b r a t o r output and d r i v e s the power t r a n s i s t o r Q1. A1.4.1 PRACTICAL CONSIDERATIONS The v o l t a g e step-up c a p a b i l i t y of the i n d u c t o r has been d i s c u s s e d b r i e f l y . However, i n choosing the value of the i n d u c t o r , energy i s an important c o n s i d e r a t i o n . During the time the t r a n s i s t o r i s turned on, the i n d u c t o r s t o r e s energy. T h i s energy i s added to the supply and d e l i v e r e d t o the l o a d when the t r a n s i s t o r i s , turned o f f . The t o t a l energy must be enough ' to supply the l o a d and maintain output v o l t a g e . As the l o a d i s i n c r e a s e d , the t r a n s i s t o r must remain on longer i n order to s t o r e more energy i n the i n d u c t o r . The r e q u i r e d value of i n d u c t a n c e depends on frequency of o p e r a t i o n , duty c y c l e , and l o a d . A l i n e a r change i n c u r r e n t through the i n d u c t o r i s a d e s i r a b l e c o n d i t i o n and i n d i c a t e s o p e r a t i o n i s over a s m a l l segment of the i n d u c t o r ' s c h a r g i n g and d i s c h a r g i n g curve. The powdered i r o n core used f o r the i n d u c t o r has a low mu, and t h e r e f o r e a l a r g e inductance change i s FIG. A1.31 SWITCHING REGULATOR CIRCUIT DIAGRAM 142 u n l i k e l y with i n c r e a s e d c u r r e n t . E f f i c i e n c y of the c i r c u i t depends mainly upon the s w i t c h i n g and s a t u r a t i o n l o s s e s of the power t r a n s i s t o r . The peak c u r r e n t through the t r a n s i s t o r i s c o n s i d e r a b l y g r e a t e r than the i n p u t c u r r e n t . The f l y b a c k diode (D1) must have a f a s t r e v e r s e recovery time and low forward drop. There w i l l be a l a r g e c u r r e n t s p i k e through the t r a n s i s t o r i f the diode i s slow. The diode used i n the c i r c u i t has a forward drop of 1.4 V max., but i s used because of i t s t r r of 0.1 us. Output v o l t a g e v a r i a t i o n s r e s u l t i n g from changes i n ambient temperature are caused by two major f a c t o r s : p o s i t i v e temperature c o e f f i c i e n t of the Zener diodes, and the n e g a t i v e temperature c o e f f i c i e n t of the e m i t t e r diodes of the t r a n s i s t o r s . The e f f i c i e n c y of the c i r c u i t drops o f f a t low power l e v e l s . T h i s i s due to the f a c t t h a t the l o s s e s of the c i r c u i t are not p r o p o r t i o n a l to the output power. Maximum e f f i c i e n c y occurs at about 80% of f u l l power. R e g u l a t i o n over the power output range i s l e s s than 0.6%. Whenever the i n p u t v o l t a g e i n c r e a s e s above 28 v o l t s , the output v o l t a g e t r a c k s the i n p u t . The d i f f e r e n c e between the two v o l t a g e s i s the drop i n the f l y b a c k diode. A1.4.2 CIRCUIT DETAILS The p r i n c i p a l components, L1, Q1, D1 and C1 are p h y s i c a l l y l a r g e and occupy most of the space i n the r e g u l a t o r . Q1 i s a 10A- D a r l i n g t o n t r a n s i s t o r i n a TO-3 case. C1 i n c l u d e s two c a p a c i t o r s each one capable of s u s t a i n i n g f u l l l o a d , so t h a t the 143 r e g u l a t o r can remain s e r v i c e a b l e should one of the c a p a c i t o r s f a i l . A l l the t r a n s i s t o r d r i v i n g c i r c u i t r y has been placed on the p r i n t e d c i r c u i t board. The o s c i l l a t o r , which i n c l u d e s R13, R14, R15, C6 and Q6, i s a normal u n i j u n c t i o n t r a n s i s t o r o s c i l l a t o r o p e r a t i n g at about 9 KHz. I t i s coupled t o the monostable m u l t i v i b r a t o r through C5. Q2, and Q5 are the two t r a n s i s t o r s , along with b i a s i n g and timing components R4, R6, R8, R11, R12 and C4, which form the monostable v i b r a t o r . Pulse width modulation i s achieved by i n j e c t i n g c u r r e n t i n t o the base of Q2. R1, R2, R7, P1, C2, Q3 and Q4 form the output v o l t a g e s e n s i n g c i r c u i t r y . R9, D2 and C3 form a r e f e r e n c e v o l t a g e . In the qui e s c e n t s t a t e Q2 i s conducting and Q5 i s non- conducting. When Q5 i s t r i g g e r e d on by a pulse from Q6, through C5 Q2 i s turned o f f by a ne g a t i v e pulse through C4. The r e l a x a t i o n time of R8 and C4 determine the maximum duty c y c l e of Q2. I f the output v o l t a g e i s s u f f i c i e n t l y high the v o l t a g e on the tap o f P1 approaches the r e f e r e n c e l e v e l of D2. Q3 tu r n s o f f and Q4 t u r n s on, d r i v i n g the base of Q2 from the c o l l e c t o r of Q4 and reducing the " o f f " duty c y c l e of Q2. T h i s reduces the "on" duty c y c l e o f Q1 which completes the feedback loop. 144 Table A7: Switching Regulator P a r t s L i s t Q1 DTS 1020, Delco R3 220 0.5w, 5% Q2 2N930 R4 1500 0.5w, 5% Q3 2N3251 R5 6800 0.5w, 5% 03 2N3251 26 1500 0. 5w, 5% Q5 2N930 R7 1800 0.5w, 5% Q6 2N1671B R8 150K 0.5w, 5% C1 22,000 u f d , 35 V (x2) R9 680 0.5w, 5% C2 50 u f d , 15 V, 10% R10 62K 0.5w, 5% C3 220 ufd, 25 V, 1016 R11 1800 0.5w, 5% C4 680pfd, 10% R12 1500 0.5w, 5% C5 0.0033 ufd, 10% R13 680 0.5w, 5% C6 0.033 ufd, 10% R14 120 0.5w, 5% D1 1N3889 R15 47K 0.5w, 5% D2 18 V, 1 watt Zener P1 500 Ohm, 10 Turn R1 1200 0.5w, 5% L1 1.1 mH, 16AWG on R2 1800 0.5w, 5% Armaco FBC core M i s c e l l a n e o u s : 1 - Wafer s w i t c h , 4 p o s i t i o n , s i n g l e pole 1 - Tungsten panel lamp, 28 V 1 - Panel meter, 50 VDC, KM-48, H i o k i , with diode 1 - HKP Buss fuse h o l d e r , with 7.5 amp f u s e 145 A1.5 THE COENEB EEFLECTOB ANTENNA The U n i v e r s i t y o f B r i t i s h Columbia r a d i o echo sounder uses a two element, 90° c o r n e r r e f l e c t o r antenna. At 840 MHz, r e f l e c t o r type a p e r t u r e antennae are convenient both i n c o n s t r u c t i o n and a p p l i c a t i o n , and provide a high gain performance with r e l a t i v e l y l i t t l e s o p h i s t i c a t i o n . The 90° corner r e f l e c t o r compares': f a v o u r a b l y i n forward gain with the " i d e a l " p a r a b o l i c r e f l e c t o r , and a l s o reduces the 90° s i d e l o b e l e v e l , important i n c o n s i d e r a t i o n of a i r path r e f l e c t i o n s from v a l l e y w a l l s . Forward gain o f the U n i v e r s i t y of B. C. antenna i s 15 dB over i s o t r o p i c , 10 dB provided by the c o r n e r r e f l e c t o r ( F i g . A1.32), 3 dB from the double d r i v e n element and 2 dB by the d i p o l e r a d i a t o r s . A1.5.1 DESIGN DETAILS The two d r i v e n elements, e l e c t r i c half-wave d i p o l e r a d i a t o r s , are l o c a t e d approximately 0.4X (150 mm) from the apex of the co r n e r . T h e i r c e n t r e - t o - c e n t r e s p a c i n g i s 1.5 X (536 mm) . At these p o i n t s the nominal r a d i a t i o n r e s i s t a n c e f o r each d i p o l e i s 100i2 (see f i g u r e A1.33). Each d i p o l e i s f e d s e p a r a t e l y by a 100& c o a x i a l c a b l e . The 100 D. c o a x i a l c a b l e s form a "T" j u n c t i o n with a 50 £l c o a x i a l c a b l e a t a po i n t which i s an exact m u l t i p l e of a h a l f wavelength from the d i p o l e feed c e n t r e s . The 50Q. c o a x i a l c a b l e i s the power feed c o n n e c t i o n from(to) the radar t r a n s c e i v e r . In t h i s manner the d i p o l e s are d r i v e n i n phase with corresponding g a i n i n the forward d i r e c t i o n , and with an enhanced n u l l i n the E - plane 90° s i d e U 6 GO < O Q CC < or o LL "0 1 2 3 CORNER REFLECTOR-DIP0LE SPACING (WAVELENGTHS) A F T E R J A S I K . 1961 FIG.A1.32 CORNER REFLECTOR GAIN vs SPACING 0 1.0 2.0 3.0 CORNER REFLECTOR-DIPOLE SPACING (WAVELENGTHS) A F T E R J A S I K . 1961 FIG.A1.33 CORNER REFLECTOR IMPEDANCE vs SPACING 147 lobe d i r e c t i o n . The d i p o l e elements were designed and c o n s t r u c t e d f o r the U n i v e r s i t y of B r i t i s h Columbia r a d i o echo sounder by S i n c l a i r Badio L a b o r a t o r i e s L t d . , Burnaby, Canada. Each d i p o l e comprises a broadband d i p o l e element, balun and a PVC radome. C o n s t r u c t i o n d e t a i l s are p r o p r i e t a r y . The r e f l e c t o r i s f a b r i c a t e d of T6 aluminium t u b i n g and chan n e l i n g ( F i g . A 1.34). Each s i d e o f the r e f l e c t o r comprises e i g h t 0.375" (9.5 mm) tubes suspended at 1.75" (44 mm) c e n t r e s i n 0.75" x 1.50" (19 mm x 38 mm) channels and held i n place by r i v e t s . The r e f l e c t o r s and d i p o l e c e n t r e supports are b o l t e d to two g a l v a n i z e d s t e e l b r a c k e t s , which determine the angle of the r e f l e c t o r s . A l l hardware i s type AN. In a d d i t i o n to the two d r i v e n elements a t h i r d p a r a s i t i c element has been placed p r e c i s e l y h a l f way between the two dr i v e n elements, and i s hel d i n place by a f i b r e g l a s s e x t e n s i o n of the radomes. The p r i n c i p a l f u n c t i o n of the e x t r a element i s to improve the VSWB of the antenna by i s o l a t i n g the two d r i v e n d i p o l e s . The p a r a s i t i c element c o n s i s t s of an aluminium tube approximately 20 mm diameter and 10% lo n g e r than 0.5X . The e f f e c t of the p a r a s i t i c element i s as f o l l o w s . In the absence of a p a r a s i t e , s t a t i c BF f i e l d s around each d r i v e n element induce c u r r e n t s with 1.5 c y c l e s delay i n the other d r i v e n element r e s u l t i n g i n power r e t u r n i n g i n t o the antenna fe e d and a poorer VSWB. The p a r a s i t e i n t e r f e r e s with the s t a t i c f i e l d r e d u c i n g the c r o s s - o v e r c u r r e n t s c o n s i d e r a b l y . The e f f e c t of the p a r a s i t e on the, antenna p a t t e r n i s minimal. BF f i e l d s a t the p a r a s i t e are 0.75 c y c l e s behind i n U 8 FI6A1.34 THE CORNER REFLECTOR ANTENNA U 61cm *\ A ' n r V i - H 1 f n r ) = l l = = c h ) 53.6cm • 1 122 cm A SECTION A-A 149 phase those being r a d i a t e d at the d r i v e n d i p o l e c e n t r e s . The p a r a s i t e must then r e r a d i a t e power 0.75 c y c l e s ahead of t h a t being r a d i a t e d from the d r i v e n d i p o l e s . The s l i g h t e l o n g a t i o n ( r e l a t i v e t o 0.5X ) of the p a r a s i t i c element r e g u i r e s t h a t the phase of the r e r a d i a t i o n be advanced s t i l l f u r t h e r ( c f . J a s i k , H., 1961, r e f l e c t o r elements i n Yagi antennae, p. 5-6).. The net e f f e c t i s t h a t power r e r a d i a t e d from the p a r a s i t i c element i n t e r f e r e s c o n s t r u c t i v e l y i n the forward d i r e c t i o n , with power being r a d i a t e d by the driven. d i p o l e s . Assuming any reasonable p a r a s i t i c element parameters however, r e s u l t s i n a d d i t i o n a l forward gain being c o n s i d e r a b l y l e s s than 1 dB. F i g u r e A1.35 shows a s e r i e s of t h e o r e t i c a l antennae p a t t e r n s based on t h i s model. G and H are E t plane and H - plane p a t t e r n s r e s p e c t i v e l y , f o r an antenna with a p a r a s i t i c element r e r a d i a t i n g power with 0.15 c y c l e s phase l a g delay and 10% power r e l a t i v e t o power r a d i a t i n g from the d r i v e n elements. These p a t t e r n s are probably c l o s e s t to the r e a l antenna p a t t e r n . A i s the p a t t e r n c a l c u l a t e d f o r the same antenna with no p a r a s i t i c element. O v e r l e a f : F i g u r e A1.35. T h e o r e t i c a l p a t t e r n s f o r v a r i o u s c o r n e r r e f l e c t o r antennae. Each p a t t e r n has assumed the presence of an i d e a l 90° corner at 0.4 X s p a c i n g , with two d r i v e n d i p o l e s . Only the p a r a s i t i c d i p o l e parameters have been v a r i e d . P a t t e r n A shows the estimated p a t t e r n with no p a r a s i t e present. The number above each o f the other p a t t e r n s r e p r e s e n t f i r s t the assumed r a d i a t e d power of the p a r a s i t e r e l a t i v e t o the d r i v e n d i p o l e s , second the phase l a g of the p a r a s i t e r a d i a t i o n r e l a t i v e t o the d r i v e n d i p o l e r a d i a t i o n . The p a t t e r n s p l o t r e l a t i v e power versus angle. 150 FIGURE A1.35 151 A1.5.2 CALIBRATION: VSWR AND FORWARD GAIN Voltage s t a n d i n g wave r a t i o s have been provided by S i n c l a i r Radio L a b o r a t o r i e s L t d . VSWR i s 1.14 at the c e n t r e frequency (840 MHz) and approximately 1.4 at the band edqes (±20 MHz). The forward gain o f the antenna has been measured a t v e r t i c a l i n c i d e n c e over a lake by using the r e l a t i o n % _ y ^ e - J 0 M L where P R and P T are r e c e i v e d and t r a n s m i t t e d power, r i s the antenna a l t i t u d e and L i s the system l o s s e s i n dB. The water s u r f a c e has been assumed to be a p e r f e c t r e f l e c t o r . F i g u r e A1.36 i s an echogram recorded over Kluane Lake. I t was flown a t 165 m above the s u r f a c e (1.1 us delay) and shows a c l e a r s p e c u l a r r e f l e c t i o n with r e c e i v e d power of +2 dBm ±2 dB. P e r t i n e n t data a r e . i n Table A8. I t f o l l o w s t h a t 2G - (14 + 81) = -64 dB ± 2 dB or G = 15.5 dB ± 1 dB. 152 F i g u r e A1.36. An A-scope echogram over Kluane l a k e The f i r s t pulse i s the t r a n s m i t t e d p u l s e . The second p u l s e i s a +2 dBm r e f l e c t i o n from the l a k e s u r f a c e . The t h i r d p ulse i s a m u l t i p l e r e f l e c t i o n o f f the a i r c r a f t . The echo d e l a y i s 1.1 us i n d i c a t i n g an a i r c r a f t c l e a r a n c e of 165 m. 153 Table ft8: Forward Gain Measurement Data Transmitted power (4 KW) 66 dBm Beceived Power 2 dBm ±2 dB System Losses: C i r c u l a t o r I n s e r t i o n Loss 0.50 dB I.F. F i l t e r I n s e r t i o n Loss 0.4 dB Diode L i m i t e r I n s e r t i o n Loss 0.1 dB Mixer Conversion Loss 10 dB Cable Losses 2.7 dB VSWB Losses <1 dB T o t a l Losses: 14 dB Geometric l o s s f a c t o r -81 dB 154 APPENDIX 2: TRAPRIDGE GLACIER AND HAZARD GLACIER FLIGHT LINE MAPS Fi g u r e A2.1 shows the p o s i t i o n s of a l l c o n t r o l l e d f l i g h t l i n e s on the T r a p r i d g e G l a c i e r . The map i s a composite of t h r e e f l i g h t s made on August 28 and 29, 1976. Ice depth data was s u c c e s s f u l l y recorded along approximately 80% of these l i n e s . F i g u r e A2.2 shows the p o s i t i o n s of a l l c o n t r o l l e d f l i g h t l i n e s on the Hazard G l a c i e r . Depth data were s u c c e s s f u l l y taken along approximately 90% of these l i n e s . The h i g h e r d e n s i t y was achieved by a r r a n g i n g f o r r e c o r d e r dead time t o occur a t the g l a c i e r boundaries. The three t r i a n g l e s on F i g u r e A2.2 r e p r e s e n t the th r e e d r i l l s i t e s occupied during the s u r f a c e d based p a r t of the f i e l d work (Napoleoni and C l a r k e , 1978). The a s t e r i s k r e p r e s e n t s the l o c a t i o n o f the f r o n t i s p i e c e photograph.   157 APPENDIX - 3: DIFFRACTION FROM A LINEAR RIBBON SCATTERER To decide i f i t i s p o s s i b l e to d e t e c t a l i n e a r s c a t t e r e r of s p h e r i c a l waves i t becomes necessary to model the d i f f r a c t e d f i e l d f o r predetermined t r a n s m i t t e r and r e c e i v e r antennae. Three assumptions are convenient: t h a t p o l a r i z a t i o n e f f e c t s are n e g l i g i b l e , i . e . , we need only t o s o l v e f o r the s c a l a r wave s o l u t i o n (Berry, 1973), t h a t the t r a n s m i t t e r and r e c e i v e r antennae are a t the same l o c a t i o n , and t h a t the s c a t t e r i n g o b j e c t i s h o r i z o n t a l . The model used here assumes t h a t the l i n e a r s c a t t e r e r may be modelled as a f l a t , narrow r i b b o n with u n i t r e f l e c t i v i t y . The width of the r i b b o n must be s m a l l i n comparison to the dimension' of a F r e s n e l zone, but s u f f i c i e n t l y l a r g e t h a t neglected "edge" d i f f r a c t i o n terms are s m a l l r e l a t i v e to the t o t a l d i f f r a c t e d term. (A very t h i n l i n e s c a t t e r e r (small diameter r e l a t i v e t o X ) s c a t t e r s r a d i a t i o n always p o l a r i z e d p a r a l l e l t o the l i n e (Huynen, 1978). With our 20 cm wavelength such s m a l l l i n e s c a t t e r e r s l i k e l y w i l l not e x i s t i n g l a c i e r s . T h i s does not imply t h a t s c a t t e r i n g o b j e c t s which do p r e f e r e n t i a l l y p o l a r i z e b a c k s c a t t e r e d r a d i a t i o n won't e x i s t . Objects shaped l i k e s m a l l d i p o l e s w i l l a l s o have t h i s property.) A3. 1 COORDINATE SYSTEMS Three systems are u s e f u l f o r the f o l l o w i n g a n a l y s i s . A r e c t i l i n e a r system, referenced to the antennae l o c a t e s a p o i n t ( X ' » Xa#X j ) on the o b j e c t "(Figi A3.'!)'."• Xi' i s * the depth of the o b j e c t below the antennae, Xz i s the d i s t a n c e to the p o i n t w . A3.1 SCHEMATIC OF RIBBON SCATTERER MODEL 159 p a r a l l e l t o the E - a x i s of an antenna, i s the d i s t a n c e to the po i n t normal t o the E-a x i s of the antenna. Assume t h a t a l l d i s t a n c e s are measured i n wavelengths. Define a p o l a r system r e l a t i v e t o the antenna with 8 the o f f - v e r t i c a l angle, <**<j> (see below) the azimuth r e l a t i v e to the antenna E - a x i s , and R the r a d i a l d i s t a n c e . A t h i r d system w i l l a l s o l o c a t e a point on the s c a t t e r i n g o b j e c t . L e t /3 be the minimum o f f ^ v e r t i c a l angle t o p o i n t s on the o b j e c t . T h i s d e f i n e s a h o r i z o n t a l vector D normal t o the o b j e c t . L e t «. be the azimuth of the vecto r D r e l a t i v e to the antenna E - a x i s . L et the endpoint of IT d e f i n e the o r i g i n of an L- a x i s a l o n g the o b j e c t , with L i n c r e a s i n g as i n c r e a s e s through zero . I t f o l l o w s t h a t D = JTDI = X . tan/3 X2 = -Lsinc* + Dcosoc A3= Lcosc* + Dsinoc . (A3..1) I t f o l l o w s t h a t = (--J=- sin a + cos a } tan £ X. 1 D J = { -L- cos a + sin a } tan /9 (A3.2) and 160 t a n 2 0 s * * + x » = / JL_ + l} tan*/3 X? D2 L + tan2/3 X,2 and t h a t tan + = = ~T7~ c o t # D X By i n t r o d u c i n g a parameter = L/Xi these reduce t o 0= 0 (£ ,£) = arctanU2 + ton2/3) l/2 4> = ,/S) = aretan(£Cot/3) (A3.3) (A3.4) (A3.5) A3.2 THE KIBCHHOFF INTEGRAL The f o l l o w i n g a n a l y s i s i s modelled a f t e r Berry (1972). The r e c e i v e d e l e c t r o m o t i v e f o r c e (EWF) from a l i n e a r r i b b o n s c a t t e r e r may be estimated with K i r c h h o f f ' s formula (see eg. Longhurst, 1957, p. 192, eq^n 10-15) . Assuming Xi » \ , which i s reasonable during echo sounding. 161 d y = 6 1 F'(t-2R/c)cosg ( A 3 * 6 ) 2*cR 2 where d £ i s the r e c e i v e d c o n t r i b u t i o n from area element d £ , and I i s a g u a s i s i n o s o i d a l wavefunction of f i n i t e d u r a t i o n . (See eg. Longhurst, 1957, p. 193, eg'n 10-16; Berry, 1972, eg'n A-1). I n t e g r a t i n g over the h o r i z o n t a l plane, CTT C F'(t - 2 R / c ) R3 F'(t -2R/c) RX. F'(t - 2R/c) 2 t C • « R2 2 « J J 1 ,13.7) where S= ( X 2 2 + X^z) l / 2 i s the l e n g t h of the h o r i z o n t a l v e c t o r S=(Xz,X-i) from the suiantenna p o i n t to a s p e c i f i e d p o i n t i n the h o r i z o n t a l plane. Since S 2 = S-5 = 5-VsR (A3.8) i t f o l l o w s that 162 (A3. 9) By v e c t o r i d e n t i t y (see, e.g. Panofsky and P h i l l i p s , 1962, p. 471, eg'n 7) V*-(«// A) = AvV^ + ^ V A ^ F ( t - 2 R / c J ? = S-7 f iF(t -2R/c ) f R 2 Xi R z Xi + F(t-2R/c)Vs[^.J (A3.10) By the divergence theorem the i n t e g r a l over the l e f t s i d e of A3.10 vanishes (see, e.g. S t r a t t o n , 1941, p. 429, eg'n 34). Thus / / F ( t - 2 R / c ) V s y y dT - _ ff S VsF(t-2R/c) d Z JJ R 2 Xi 2 ff F'(t -ZR/C) f n n -S-VsRdS (A3.11) . ' C R2 X. Thus with A3.9 163 + j _ ; / F ( t . 2 R / c , ^ . i ^ d r (A3.12) E v a l u a t i n g the divergence term i n the second i n t e g r a l ax 3 lx,(x.2+x2 2+x3 2)J 2X,(X,2+X22+X,2) - 2X.X g - 2X.X3 X,2(X,2 +X22+X32 )2 2X.3 X.2 (X.2 +X22+X32 )2 ax 2 Lx,(x,z+x| +x|) d _ r X 2 (X/ 2 + X2 2+X3 2)2 2X, R4 (A3.13) Thus with A3. 12 F'(t-2R/c) RX, ^ / / F O - a R / o ^ j d j ; (A3. 14) Since F i s g u a s i - s i n o s o i d a l with predominant frequency, say to 0 , 164 F' = «o0 F As assumed A << X i } R hence I (A3. 15) R < K C (A3.16) Thus the second term i n the i n t e g r a l can be n e g l e c t e d , and The e f f e c t s of antenna p a t t e r n s weight the i n t e g r a n d . For t r a n s m i t t e r p a t t e r n G-j.(@><H then -I r r F ' ( t -2R / c ) „ I f the l i n e a r s c a t t e r e r i s modelled as a narrow r i b b o n of constant width with u n i t r e f l e c t i v i t y on the r i b b o n and zero r e f l e c t i v i t y o f f the ribbon then dZ. can be r e p l a c e d by dL or by XiH§ and the i n t e g r a l becomes a l i n e i n t e g r a l -I F z ( F'(t - 2R/C ) (A3.19) *(?)as — - f / P t ' G_ dL dw where dw runs across the width, W, of the ribb o n . Two assumptions are r e q u i r e d f o r t h i s e x p r e s s i o n ; t h a t the ribbon i s s u f f i c i e n t l y narrow t h a t a c r o s s i t s width the i n t e q r a n d i s 165 e f f e c t i v e l y c o n s t a n t , t h a t e f f e c t s caused by the d i s c o n t i n u i t y at the r i b b o n edge can be ignored. The f i r s t assumption r e g u i r e s t h a t the width of the ribbon be, a t any p o i n t , w e l l w i t h i n one F r e s n e l zone. The phase d i f f e r e n c e a c r o s s the ribbon, P w _ { X i . + [ x , _ + [ X j - ^ i i ± ^ > f f = {x 2+X 2 2+X 3 2+^+[x 2wcos(* + a) + X5wsin(4>+a)]} 2 1 \ U Z - {X.2 + Xj+X32+^- - [X 2 wcos(<£ + a) + X3wsin(* + a)J) (A3.20) The maximum f o r P w occurs a t <j> =0 s i n c e -j- (X2wcos(4>+a) + X3wsin($*a)) * (A3.21) = -wX2sin(tf>+a) + wX 3 cos(£ + a) s 0 i f and only i f 4> =0. At t h i s p o i n t (the L o r i g i n ) 166 J/2 , J '2 Pwmax = -{x.'+.tp + f ) 2 } - { X , 2 + I D - £ - ) ' } 2 1/2 2 ^ {X i ' +D 8 * ^ - +Dw} -{•X. , + D 8 + ^ -Dw} 1/2 1/2 S |R O 2 + ROW sin/9} - |R 0 2 - RoWSin/3 } (A3. 22) where E 2 = Xi 2 + D 2 and we assume W « D , X , • I t f o l l o w s t h a t PWmox = (Ro + " ( R o - (A3.23) Thus the assumption i s s a t i s f i e d i f Wsin^ « 1 . Because of i t s g u a s i - p e r i o d i c i t y we s h a l l take F ( t ) . Ae ' " 0 ' Thus the r e t a r d e d time d e r i v a t i v e -i47rP(e ,<£,Xi) F'(t) « A e (A3.24) where A i s an a r b i t r a r y amplitude, P i s a phase delay f u n c t i o n expressed i n c y c l e s which determines the r e t a r d e d p o t e n t i a l r e l a t i v e to the L o r i g i n (see below), and the time dependence has been f a c t o r e d out. The i i n d i c a t e s a "nc/2 phase s h i f t and can be n e g l e c t e d i n t h i s c a l c u l a t i o n . The e f f e c t i v e f i e l d s t r e n g t h as measured by the r e c e i v e r 167 antenna a l s o weights the c o n t r i b u t i o n from the s c a t t e r e r by a gain f a c t o r G^(^,4j' Thus y . = d/o AW r GTGR e - i 4 i r P ( 0 , <*>,X,)_ (A3.25) 2 ir c R where the dependence o f # and c/> on J are as s t a t e d i n A3.5. F i n a l l y , i f the t r a n s m i t t e r and r e c e i v e r antennae are r o t a t e d by <*T and a R with r e s p e c t to the l i n e a r s c a t t e r e r then y K /RGT(e,aT+4>) GR(0,aR+4>) c - i4*P (g , <fr,X,) ^ J R (A3.26) with K = cj0Aw/2-nc. For the $ , coo r d i n a t e system s i n c e and then E z = L2 + D2 + X,z (A3.27) (E - CP) 2 = D2 + X.2 (A3.28) CP = ( L 2 +D 2 + X.2 )"2- ( D 2+X, 2)" 2 { I 2 D 2 1/2 D 2 1/2 "V = X.{(£2+tan2/3 + l)"2- (tan2/3+l)"2} = X,{u2+sec2/3)"2-secyS } (A3.29) The K i r c h h o f f i n t e g r a l may be r e w r i t t e n 168 * = X / ' G ( e ' l a T + ^ G ( a l a R + * ) c o . « e ' i 4 , r P l 0 , * , X , ) d € Xi ^ 1 (A3.30) where the antennae g a i n f u n c t i o n s have been assumed to be i d e n t i c a l . A3.3 NUMERICAL RATIONALIZATION The i n t e g r a l i s not y e t n u m e r i c a l l y t r a c t a b l e because _•. 4 t tP t e i s a r a p i d l y varying f u n c t i o n of j . We wish to l e t dP become the i n t e g r a t i n g v a r i a b l e which r e g u i r e s having the i n v e r s e f u n c t i o n of P. For a given Xi , ft we have (A3.31) X,{u2 + s e c 2 £ ) " 2 - s e c / j } - = P Then t; = ±{( Yt + s e c £ , e and - sec 2/3 } 1/2 (A3.32) 169 dA = ± 1 - - 2(|-+sec/8)-7- 2 {^+sec0 ) 2 - sec2)9} I + Xi secff = + — (A3.33) The K i r c h h o f f i n t e g r a l then becomes oo K ' o -i4irP _P R cos 8 e •• . — j 7 2 dP (A3.34) where the i n t e g r a l has been r e w r i t t e n to account f o r the d u p l i c i t y of J" as a f u n c t i o n of P. The i n t e g r a l has been w r i t t e n t o run from 0 to oo . The i n t e g r a l from - «? to 0 has been f o l d e d onto the p o s i t i v e limb by adding G(6 }"V- j>)G(fy °^- <£) to the p o s i t i v e cf> arguments a t the same P val u e . Again note t h a t Q and <j> are f u n c t i o n s of £ , and thus are f u n c t i o n s o f P. The i n t e g r a l i s now i n a n u m e r i c a l l y t r a c t a b l e form. The pole at the o r i g i n i s removable by s u b t r a c t i n g 170 G ( ^ , a T ) G C ^ , a R ) c o s i 8 e " i 4 , r P < v / ^ " 0 (A3.35) from the i n t e g r a n d s i n c e as P tends t o 0 Ro P f Ro FVl 1 7* I P' p Note that a f a c t o r of two has been absorbed i n t o the r a d i c a l from the d u p l i c i t y a t 4> =0. The value of the pole i s G ( ^ , « T ) G ( A « R ) c o 8 i 3 j ^ p i e , 4 , r P d P • (2X,sec/5)"a = [~^] G^ v « T )G ( / ? , a R ) c o s^ (2X i s e c^ ) " 2 (Gradshteyn and Ryzhik, 1965, p.420, eg'ns 3.757.1 & 3.757.2) Set J(P) = {G(e,aT+^)G(0,aR+</>) + G(d,a T-«/>)G(e,a-<^) } Ro <A 3 ' 3 7> ~D~ f2Ro"l l / z • cos8 • ^ - T n , - -G (0, a T ) Gl0, « R ) cos/3 [-̂ -J with *— ^ (A3.38) sec 0 = sec P ( I + ——) and 171 1/2 tan </> esc P (A3.39) Ro P A3.38 and A3.39.follow from A3.5 and A3.32. From A3.5 tan20 = £ 2 + tan 2/3 — sec20 = £ 2 + sec2/3 I — X.(sec0 - sec/3) = P X.secfl= P + X.sec/3 = P + Ro rPjhRoi = sec/3 P + Ro Ro = sec A l s o from A3. 5 172 tan<£ = £ cot £ -~ tan2* = £ 2cot2/3 + sec/3)2 - sec2̂ } cot2/3 = f _L l + — sec/3} cot2/3 = { 2 + —] cot2^sec2£ A x , 2 X. P j P lX, 2sec 2/3 X.secfl' I + <.Xisec/3V I + csc2/9 Xi 2 sec2/3 ZR< Ro2 { I + — tan <f> 2R< R< csc/S csc2/3 A3.4 NUMERICAL ANALYSIS Consider a f u l l c y c l e of P, i . e . e'^ 7 7^ where P goes from N t o N+ j . I f we break up the i n t e r v a l i n t o f o u r equal i n t e r v a l s (N^N + 1/8) , (N+1/8,N+1/4), (N+1/4, N+3/8) , (N+3/8,N+1/2) we can e v a l u a t e the i n t e q r a l piecewise . f o r the r e a l ' and imaginary terms. C a l l J ( N ) = J O , J(N + 1/8)=J*, J(N+1/4)=J2, J(N+3/8)=J3, J (N+1/2) = J * and assume t h a t the f u n c t i o n J i s piecewise l i n e a r on the s u b i n t e r v a l s . Then the i n t e g r a l may be evaluated as f o l l o w s (see F i g . A3. 2) : J ( N ) J ( N + | ) J ( N * ^ ) J ( N * f ) . mm • •F(N*J) FIG. A3.2 KIRCHHOFF DIFFRACTION PICTORIAL OF NUMERICAL MODEL 174 Beal component = IN.N++) (N-hJ-.N+i) (N-+-J.N + i ) (N + f,N + i) J ( J °+8PA J ° ) cos4 i rPdP o - /(J' +8PAJ- )sin 4irP dP o J -/ (J2 + 8PAJ2)cos4 7rP dP -1/8 +J (J3+8PAJ3 )sin 4irP dP (A3. 40. 1) Imaginary component = - / ( J ° + 8PAJ°)sin 4irP dP o i/e - J (J1 +8PAJ')cos4irP dP o f 1/8 + / ( J 2 +8PAJ2)sin 4 T T P dP • 1/8 +J (J3 + 8 P A J 3 ) c o s 4 » P dP (A3.40.2) where A J * = J*» + i - J " . By changing to v a r i a b l e x=8P, the e i g h t components become 175 Beal components: i A j ° + x A J ° ) C O S f x dx / (J1'+ x A J ' )sin -fx dx - i I (J2+ xAJ 2 )cos f x dx + i j (J8 + xAJ 3 ) sin f x dx i T Imaginary components: i - if ( J ° + x A J ° ) s i n f x dx o - i J (J1 + x A J ' )cos - f x dx + i / ' ( J 2 + x A J 2 ) s i n f x d x o + T J ( J 3 + X A J 3 ) C 0 S X dx (A3.41) Noting t h a t 176 / c o s - ^ x d x = /sin - ^ x d x > o I */2 / x c o s - f x d x = / T y c o s y d y ^ xs in -f xdx w;/2 •J * / - j - s i n y d y = v O IT = \ [cosy + ys iny j^ y s i n ydy = [sin y - y c o s y ] 7T/2 4 (A3. 42) the e i g h t terms reduce to Real components: Imaginary components: s V ( J ° + AAJ0} - ^(J ' .+ BAJ') - «V (J Z+AAJ Z ) + ^ (J 3+BAJ 3 ) - .•^ F(J° + B A J ° ) rV (J1 +AAJ 1) + (J' + BAJ 2) .+ t ± F ( J 3 +AAJ 3 ) (A3.43) where A=(1-§.) and B=(|0- Reformulating i n terms of the J w , s • -ir 177 S e a l components: Imaginary components: { J ° ( l - A)+ J 1 A - J 1 (I - B ) - J 2 B - J 2 ( I - A ) - J 5 A + J 3 ( l - B ) + J 4 B } •rir{ J ° ( I - B ) + J ' B - J ' ( I - A ) - J 2 A + J 2 ( I - B ) + J 8 B + J 3 (I - A ) + J 4 A } (A3. 44) These reduce t o Ee a l components: I { . J ° ( l - A ) + J'(A+B-I) + J 2 (A- B-l) + J 3 ( l - B - A ) J 4 (B ) } Imaginary components: J ° ( l - B ) + J'(A-B-l) + J 2 ( ! - A - B ) + J 3 ( l+B-A) J 4 (A ) } (A3.45) But A + B — I = I - A - B = 0 A - B- l = - -V" j o and J * ove r l a p on co n s e c u t i v e c y c l e s . Thus f o r r e a l components odd n c o n t r i b u t i o n s vanish and f o r imaginary components even n c o n t r i b u t i o n s v a n i s h . A l l s u s t a i n e d terms have c o e f f i c i e n t l / - ^ 2 . Thus a numerical f o r m u l a t i o n o f the i n t e g r a l which a s s i g n s a s i n g l e summation term to each piecewise FIG. A3.3 FUNCTION "J" FOR CORNER REFLECTOR ANTENNA X, = 750, a =15°, 6= 10° TX.9 50 100 150 200 PHASE (P. in cycles) 250 oo 179 l i n e a r l y weighted q u a r t e r c y c l e of the i n t e g r a n d i s * " >^ { [ ^ ] G ( 0 . V G ( ^ V c o s 0 l 2 * ' S e c / 3 ) l ' 2 P=l (A3.46) A3.5 PHYSICAL REALIZATION Equation A3.18 i s an exact s o l u t i o n f o r the i s o t r o p i c r a d i a t o r s i n c e -I ff F ' ( t- 2R /c )_ d 2 2 i r C ^ X, R -I f , z f 0 0 F ' ( t - 2 R / c ) 2^1 i xTS " s d S d * - ^ f F ' ( t - 2 R / c ) S d S X,c 0-> R = — f ° V ( t - 2R /c ) dR Xic Xi ^ C F ( t - 2 X , / c ) = F ( t " 2 X ' / c ) X,c 2 X 2X, (A3.47) We can show t h a t A3.18 i s a l s o a reasonable e x p r e s s i o n f o r a l a r g e c l a s s of a n i s o t r o p i c r a d i a t o r s . Assume t h a t a r a d i a t o r 180 has a cos 6 d i s t r i b u t i o n . Then n\ -I r r F'(t-2R /c) zQ A~ I OO = f F ' ( t-2R /cUos 2 0 dR (A3.48) I n t e g r a t e by p a r t s ¥ ( t ) « x 4 { | - F(t - 2X,/c) + | / ^ F ( t - 2 R / c ) d R } { / F 1 t - 2 R / c ) d R + c / ^ - F ( t - 2 R / c ) d R } (A3.49) But |F«| = <*MF|, and ~ <:< — ° , hence the second term can be n e g l e c t e d . Thus #*i rr F ' (t -2R/ C ) F ' ( t - 2 R / c ) . „ F ( t - 2 X , / c ) (A3.50) 2 T T C ^ X,R • 2X, By an i d e n t i c a l procedure we can show t h a t f o r r a d i a t o r s with s i n B , sinc5sin 4» or s i n £ c o s < £ d i s t r i b u t i o n s P̂(t)=0 w i t h i n the same accuracy as the cos 6 d i s t r i b u t i o n . Sin 6 i s the d i s t r i b u t i o n of a v e r t i c a l d i p o l e . S i n 9 s i n and sin0cos<£> are the complementary d i s t r i b u t i o n s f o r two p e r p e n d i c u l a r h o r i z o n t a l d i p o l e s . These l a s t three s o l u t i o n s 181 comprise a b a s i s s e t f o r c o n s t r u c t i n g a r b i t r a r y d i p o l e s o l u t i o n s . By l i n e a r combinations of a r b i t r a r y d i p o l e s , each with i t s own X, , we can c o n s t r u c t a l a r g e c l a s s of s o l u t i o n s . T h i s i s an important r e s u l t s i n c e i t means that V l t ) = G ( 0 , - ) G ( 0 , - ) F t t " 2 X ' / c ) V w , ,~ RX~, , 2 ) < ( / / G T ( g , 0 ) G R ( g ^ ) F ' ( t  Z R / C ) 61 (A3.51) 2TTC 1 R - » ^ ' X ( R i s a reasonable approximation f o r any antenna p h y s i c a l l y r e a l i z a b l e from o s c i l l a t i n g d i p o l e s . I f P T i s the peak r a d i a t e d power, then f o r the i s o t r o p i c r a d i a t o r over a p e r f e c t r e f l e c t o r (A3.52) Then 2*c J J V 4 r X,R XlC • / V 4 7T Xi PT Zo - i « ( t - 2-X./.C) (A3.53) 2X^ 4 * 6 and 182 * ( t ) = V - ^ ^ (A3.54) Y peak 2X« 4 * and = p. x 2 (A3.55) T 6 4 T T 2 X , 2 where A /4-TT i s the r e c e i v i n g antenna's e f f e c t i v e area ( J a s i k , 1961) . For the a n i s o t r o p i c r a d i a t o r over a p e r f e c t r e f l e c t o r 2 (A3.56) P R = G r ( 0 , - ) G R ( 0 , - ) - P T £ Z ; ^ 64ir zX. z and P T 4 * Z o ' " ' p e o k ' x z 2 -i« (t -2R/c) = IsTxT- [ z ^ J [ J 7 G T < 3R 6 R i z ] . For the r i b b o n s c a t t e r e r , combining A3.57 with A3.34 183 r P R f 2 W\ /°° n -i4irp I + Ro/P . D 47X? 2^7 K- TG R +G TG R)cos*e ^ — — ^ dP (A3.58) Noting t h a t i n the nondimensionaiized system cja /2-trc=1. Then by in v o k i n g A3.46 - " ' ' • • • • 1/2 P R V!! v/X i c i - i . ^ o - o - , Qr2X> sec ft j + J C P / 8 ) e ' f P}| (A3. 59) where the i m p l i c i t d i m e n s i o n l e s s u n i t s have been i n c l u d e d .

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