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Rain attenuation at 74 Ghz 1977

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RAIN ATTENUATION AT 74 GHz by JOHN DUNCAN McNICOL B.Eng . , Carleton Unive r s i ty , 1975 A THESIS SUBMITTED IN PARTIAL FULFIMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE i n the Department of E l e c t r i c a l Engineering We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA March 1977 (c) John Duncan McNicol , 1977 In p r e s e n t i n g t h i s t h e s i s in p a r t i a l f u l f i l m e n t o f the requirements fo r an advanced degree at the U n i v e r s i t y of B r i t i s h Columbia, I agree that the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e fo r reference and study. I f u r t h e r agree t h a t permiss ion fo r e x t e n s i v e copying of t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the Head of my Department or by h i s r e p r e s e n t a t i v e s . It i s understood that copying or p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l ga in s h a l l not be al lowed without my w r i t t e n p e r m i s s i o n . Department of b (•€. c V tc*-f E ' ^ i n ' g e Y i v ^ The U n i v e r s i t y of B r i t i s h Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1W5 Date H c A Vt\ , 1 3 1 7 ABSTRACT A mil l imetric wave transmission l ink of the radar type has been established at the University of Br i t i sh Columbia campus. It operates at 74 GHz and has a 1.8 km total transmission length. The RF source i s an unmodulated klystron and a phase-locked receiver i s used to detect the received s ignal . The main objective i s to measure the excess path attenuation due to prec ipi tat ion. For this purpose a weather station has been con- structed. It consists of 5 tipping-bucket rain gauges distributed along the path and apparatus for the measurement of temperature and wind v e l - oci ty . The leve l of the microwave signal and the outputs of the weather sensors are transmitted to a central stat ion. There, i n i t i a l processing and data recording on magnetic tape are performed on a continuous basis by a Nova 840 minicomputer. Subsequently, data i s further processed on an IBM 370. Of the 1400 hours of data recorded during a four month period, approximately 25 hours included simultaneous rain and microwave data and were suff ic ient ly "reliable" to analyse. The processed experimental data are compared with the theory of Ryde and Ryde over the range of ra in rates observed (0 to 10 mm/hour). (i) TABLE OF CONTENTS ABSTRACT '. . . . . . . . . . 1 TABLE OF CONTENTS i i . LIST OF ILLUSTRATIONS . v LIST OF TABLES v i i i ACKNOWLEDGEMENT • x I . INTRODUCTION . . 1 1.1 An. Overview of the Atmospheric Propagation of Microwaves . 1 1.2 Atmospheric Effects 4 1.2.1 Attenuation . ^ 1.2.2 Cross Polarization 12 1.3 Considerations in an Experimental Transmission Link at 75 GHz 12 1.3.1 Background 12 1.3.2 Expected Rain Rates in Vancouver . . 14 1.3.3 Estimated R e l i a b i l i t y of Two Paths in Vancouver . 14 1.3.4 Considerations i n Path Selection 17 1.4 Scope of the Thesis i 8 1.4.1 Thesis Objective 18 1.4.2 Thesis Outline 19 II . MILLIMETRIC WAVE LINK AND MEASUREMENT SYSTEMS . . . . . . . 2 1 2 . 1 Introduction 21 2.2 System Description 21 2.3 Sub-Systems 22 2.3.1 Antennas 22 2 . 3 .2 Reflector . . . . 28 ( i i ) 2 . 3 . 3 Wavegu ide 30 2 . 3 . 4 R e c e i v e r and A s s o c i a t e d Measurement U n i t s . . . . 32 2 . 3 . 5 M i x e r s 3 4 2 .3 .6 M i l l i m e t r i c Wave Sou r ce 36 2.4 D i s c u s s i o n 37 2.5 Summary . . . 38 I I I . METEOROLOGICAL MEASUREMENT SYSTEM 39 3.1 Measurement o f R a i n R a t e 39 3 .1 .1 D e s c r i p t i o n o f R a i n Gauges . 39 3 . 1 . 2 R a i n Gauge Ne two rk . . . . . . . . . . . . . . . 39 3.2 O t h e r Measurement U n i t s 41 3.3 D i s c u s s i o n . 41 IV . DATA ACQUISITION AND DATA BASE FORMATION 43 4 .1 I n t r o d u c t i o n . 43 4 . 1 . 1 P o s s i b l e R e c o r d i n g S t r a t e g i e s . . . . . . . . . . 45 4 . 1 . 2 S t o r a g e M e d i a . . 46 4 .2 M i n i c o m p u t e r I n t e r f a c e 48 4 .3 R e a l Time D a t a A c q u i s i t i o n and R e c o r d i n g . 50 4 . 3 . 1 The Comput i ng F a c i l i t y . . . . . . 5 0 4 . 3 . 2 M u l t i t a s k P rog ramming 51 4 . 3 . 3 P r o g r a m O p e r a t i o n . . . . . . . 52 4 . 3 . 4 R a i n Gauge P r o c e s s i n g 54 4 . 3 . 5 • Summary 56 4 .4 C r e a t i o n o f a D a t a Ba se 56 4 . 4 . 1 D a t a Base 56 4 . 4 . 2 D a t a Base F o r m a t i o n . . . 57 4 . 4 . 3 P r o c e s s i n g C o s t s 59 ( i i i ) V. PRELIMINARY RESULTS 6 0 5.1 Post Processing . . . . . . ^ 5.2 S t a t i s t i c a l Treatment of the Data Base 7 0 5.3 Comparison with Theory . . . . . . . 7 ^ V I . CONCLUSIONS AND DISCUSSION 7 7 6.1 Conclusions . 7 7 o.2 discuss ion • . . . 6.2.1 Suggestions for Improvements to the Present ay t> L.es 6.2.2. Related Work 7 9 79 6.2.3 Other Direct ions for Research . . . . . . . . . . ? APPENDIX A Mixer Evaluation . 8 1 APPENDIX B Rain Gauge Monitor . 8 2 APPENDIX C Anemometer 8 4 APPENDIX D Interface 8 5 APPENDIX E Data Acqu i s i t i on Software . . . . . . . 9 7 APPENDIX F Post Processing and Analysis Programs . . . . . . . REFERENCES . 1 0 5 ( iv) L I ST OF ILLUSTRATIONS FIGURE 1.1 A t m o s p h e r i c a t t e n u a t i o n i n t h e 10-400 GHz r ange . . . . 3 1.2 R a t i o o f e f f e c t i v e s c a t t e r i n g and a b s o r p t i o n c r o s s s e c t i o n t o p h y s i c a l c r o s s s e c t i o n f o r a s p h e r e o f w a t e r 7 1.3 T e r m i n a l v e l o c i t y o f r a i n d r o p s v s . d r o p d i a m e t e r . . . 7 1.4 S p e c i f i c a t t e n u a t i o n as a f u n c t i o n o f f r e q u e n c y f o r c o h e r e n t wave p r o p a g a t i o n t h r o u g h u n i f o r m r a i n 10 2.1 T r a n s m i s s i o n p a t h (a) A e r i a l v i e w (b) S i d e v i e w . . . . 23 2.2 M i c r o w a v e s y s t e m : b l o c k d i a g r a m . . . 24 2 .3 The r e f l e c t o r a t Gage Tower ' C ' . P a s t i t and t o t h e r i g h t i s t h e MacLeod B u i l d i n g where t he an tenna s a r e i n s t a l l e d 25 2.4 The t r a n s m i t t i n g a n t e n n a , t h e anemometer , a S t e v e n s o n ' s s c r e e n and a p r o t o t y p e c a p a c i t a t i v e r a i n gauge 25 2.5 The 74 GHz k l y s t r o n and a s s o c i a t e d wavegu i de components 26 2.6 B l o c k d i a g r a m o f t r a n s m i t t e r a p p a r a t u s . 26 3.1 A t i p p i n g b u c k e t r a i n gauge w i t h t h e s i d e p a n e l s removed . 40 3.2 A t i p p i n g b u c k e t r a i n gauge as i n s t a l l e d on a r o o f . . . 40 4.1 D a t a a c q u i s i t i o n s y s t e m b l o c k d i a g r a m . . . 44 4 .2 B l o c k d i a g r a m o f t h e m i n i c o m p u t e r i n t e r f a c e 49 4 . 3 The c i r c u l a r queue and a s s o c i a t e d p o i n t e r s 53 4 .4 A b l o c k d i a g r a m o f t he d a t a a c q u i s i t i o n s o f t w a r e s how ing t he messages w h i c h c o n n e c t v a r i o u s t a s k s . . . . 55 (v ) FIGURE 5.1 A t y p i c a l summary sheet for a data f i l e generated i n the f i r s t processing step 61 5.2 A compact summary of the data i n each f i l e stored on a p a r t i c u l a r magnetic tape . . . . . . . . . . . . . . . 62 5.3 (a) A p lo t of received s igna l l e v e l and path-averaging r a in rate for the period 0813 to 1113 Feb 12,.1977 . . . .63 (b) Path-average r a i n rate and 4 point r a i n rates for 0813-1113, Feb 12, 1977 . . . . . . . . . . . 6 4 . (c) Local o s c i l l a t o r frequency, c r y s t a l current and s i g - n a l l e v e l for 0813 to 1113, Feb 12, 1977 . . . . . . . . 65 5 . 4 (a) Received s igna l l e v e l and path-average r a i n rate for the period 0013 to 0513, Feb 12, 1977 . .. 66 (b) Path average r a i n rates and 4 point r a in rates for the period 0013 to 0513, Feb 12, 1977 . . . . . . . . . 67 (c) Received s i gna l l e v e l and path-average r a in rate for the period 2128, March 7, 1977 to 0116, March 8, 1977 . ' 68 (d) Path-average r a in rate and 4 point r a in rates for the period 2128, March 7, 1977 to 0116, March 8, 1977 . . 6 9 5.5 The s t a t i s t i c s of attenuation and r a in rate for data f i l e 'RAIN102299' using 10 second averages . . . . ' 7 1 5.6 A p lo t of s p e c i f i c attenuation^vs. path-average r a in rate for the period 0042 February 12, 1977 to 0512, February 12, 1977 . 72 ( v i ) FIGURE 5.7 Mean s p e c i f i c a t t e n u a t i o n v s . p a t h - a v e r a g e r a i n r a t e f o r t h e t o t a l i t y o f s e l e c t e d d a t a . 74 5.8 Mean s p e c i f i c a t t e n u a t i o n v s . p a t h - a v e r a g e r a i n r a t e f o r - t h e p e r i o d 0846 t o 1046 , F e b r u a r y 12 , 1977 . . . . . 75 A - l The s e n s i t i v i t y o f two m i x e r s as a f u n c t i o n o f l o c a l o s c i l l a t o r power . . . . . . . 81 B - l E i g h t c h a n n e l r a i n gauge m o n i t o r 83 C - l B l o c k d i a g r a m o f t h e w i n d d i r e c t i o n s e n s i n g a p p a r a t u s . . 84 D - l P h y s i c a l c o n f i g u r a t i o n o f t h e m i n i c o m p u t e r i n t e r f a c e . . 87 D-2 D i g i t a l c l o c k c a r d : s h e e t 1 88 D -3 D i g i t a l c l o c k c a r d : s h e e t 2 89 D-4 D i g i t a l m u l t i p l e x e r : s h e e t 1 . . . . . . . . . . . . . . 90 D-5 D i g i t a l m u l t i p l e x e r : s h e e t 2 91 D -6 B u f f e r . . . . . . . . . . 92 D-7 A/D c o n t r o l u n i t : s h e e t 1 • 93 D-8 A/D c o n t r o l u n i t : s h e e t 2 94 D-9 D i s p l a y p a n e l 95 D-10 2 - d e v i c e i n t e r r u p t i n t e r f a c e . . 96 E - l I n s t r u c t i o n s h e e t f o r t h e d a t a a c q u i s i t i o n s y s t e m . . . 100 E-2 D i a l o g u e w h i l e c h a n g i n g t a p e s . . . . 101 E-3 A t y p i c a l ' L 0 G F I L E ' e n t r y . I t i n d i c a t e s t h a t d a t a was w r i t t e n on f i l e s 24 t o 29 be tween 2312 Ma r ch 15 , 1977 and 1005 M a r c h ' 1 6 , 1977 ' 101 ( v i i ) LIST OF TABLES TABLE 1.1 Refractive and absorptive indicies of water at 20°C . . 6 1.2 Normalized specif ic attenuation [(dB/km)/(mm/hr)] by monodisperse rain . . . . . . . 6 1.3 Drop size dis tr ibut ion for various ra in rates (Laws and Parsons) . , 9 1.4 Specific attenuation for various rain rates assuming . the Laws and Parsons drop size distribution . . . . . . 9 1.5 A comparison of path lengths used in various propagation studies. ' . 13 1.6 Propagation studies classed by.normalized path length. . 15 1.7 Probabil ity of selected point rain rates i n various locations . . 15 2.1 Measured 3-dB beamwidths of the transmitting and receiving antennas . . . . . 29 2.2 Theoretical and measured attenuation at 75 GHz of 3 sizes of rectangular waveguide 29 2.3 Measured ref lect ion coefficients of waveguide tapers .. . 31 2.4 Calculation of system waveguiding losses 31 4.1 A comparison of various intermediate bulk storage media. 46 4.2 The 32 word record structure used in the real time data acqu i s i t i on system 53 3—1 Access commands and output formats associated with the minicomputer interface 86 )-2 Set t ing the interrupt rate of the real time clock . . . 87 ( v i i i ) TABLE E - l C e r t a i n d a t a a c q u i s i t i o n p r og r am p a r a m e t e r s 99 F - l Fo rmat o f d a t a b a s e f i l e s 103 F-2 Fo rmat o f d i s k - r e s i d e n t s t a t i s t i c a l summar ies 104 ( i x ) ACKNOWLEDGEMENT I would l i k e to express my appreciat ion to Dr. M.M.Z. Kharadly for h i s invaluable supervision and keen in te res t throughout the course of th i s research. Grateful acknowledgement i s made to the Communications Research Centre for t he i r support of th i s work under contract numbers 0SU5-OO3O and OSU76-00097. I wish to express my appreciat ion to the fo l lowing people at the Department of E l e c t r i c a l Engineering for the i r cont r ibu t ions : Mr. D. Holmes for the design of much of the meteorological equipment and his assistance i n constructing the computer in te r face ; Mr. J . Stuber for the design and i n s t a l l a t i o n of the r e f l e c t o r , antenna mounts and t ipp ing bucket r a i n gauges and h is help i n path alignment, and Mr. G. Aus t i n for h is advice and assistance on minicomputer matters. Thanks are also due to Ms. M.E. Flanagan for typing the manu- s c r i p t , Mr. T .K. Chu for the photography and Mr. T. Enegren for proof- reading. I would also l i k e to thank a l l my friends and colleagues, par- t i c u l a r l y Mr. Roger Wood and Mr. Bruce Hanson, for creat ing an enjoyable and s t imula t ing working environment. F i n a l l y , the f i n a n c i a l support received from the Nat iona l Research Council i n the form of a 1967 Science Scholarship i s grate- f u l l y acknowledged. (x) CHAPTER I INTRODUCTION 1.1 An O v e r v i e w o f the A t m o s p h e r i c P r o p a g a t i o n o f M i c r o w a v e s M i c r o w a v e r a d i o c u r r e n t l y p r o v i d e s t h e backbone o f l o n g - h a u l c o m m u n i c a t i o n s b o t h i n Canada and g l o b a l l y [ 1 ] , I n s p i t e o f r e c e n t a d v a n - ce s i n c o a x i a l , w a v e g u i d e and o p t i c f i b r e t r a n s m i s s i o n s y s t e m s [ 2 , 3 , 4 ] , r a d i o i s e x p e c t e d t o e n j o y c o n t i n u e d i m p o r t a n c e . I t has s p e c i a l a d v a n - t a g e s o v e r l o n g r o u t e s and i s p a r t i c u l a r l y a p p l i c a b l e o v e r d i f f i c u l t t e r - r a i n whe re i t w o u l d be i m p r a c t i c a l t o i n s t a l l g u i d e d s y s t e m s [ 1 ] . M i c r o w a v e t r a n s m i s s i o n s y s t ems f i n d a p p l i c a t i o n i n s e v e r a l a r e a s 1. Common c a r r i e r ( t e r r e s t r i a l ) (a ) t e l e p h o n e , b r o a d c a s t TV n e t w o r k s (b ) CATV n e t w o r k i n g 2 . S a t e l l i t e A t p r e s e n t , common c a r r i e r s y s t ems o p e r a t e m o s t l y i n t h e 4 GHz and 6 GHz bands w i t h s u b s t a n t i a l u se o f 8 GHz and 11 GHz i m m i n e n t [ 5 , 6 ] , These s y s t ems a r e c h a r a c t e r i z e d b y 40 t o 50 km hop l e n g t h s and 40 dB f a d e m a r g i n s [ 7 ] . F a d i n g i n s u c h l i n k s i s p r i m a r i l y due t o m u l t i p a t h p r o p a - g a t i o n ( s e l e c t i v e ) and e x c e s s i v e r e f r a c t i o n e f f e c t s ( n o n - s e l e c t i v e ) . By t h e u se o f f r e q u e n c y d i v e r s i t y and s p a c e d i v e r s i t y i n tandem s y s t e m s , p r o p a g a t i o n o u t a g e s a r e t y p i c a l l y r e d u c e d t o t h e 10 ^ l e v e l (5 m i n u t e s / year) . The CATV a p p l i c a t i o n i s less demanding: routes are shorter and o u t a g e s o f up t o 500 m i n u t e s / y e a r a r e o f t e n a c c e p t a b l e [ 1 ] . A f u r t h e r i n c r e a s e i n the u t i l i z a t i o n o f t h e s p e c t r u m i s o b t a i n e d by t h e u se o f o r t h o g o n a l p o l a r i z a t i o n s i n t he above s y s t e m s . The s i t u a t i o n f o r s a t e l l i t e a p p l i c a t i o n s i s somewhat d i f f e r e n t . Mos t c o m m u n i c a t i o n s a t e l l i t e s a r e p l a c e d i n g e o s t a t i o n a r y o r b i t s . Because o f t he r e l a t i v e l y l a r g e d i s t a n c e s i n v o l v e d and l i m i t e d - power o u t p u t o f s a t e l l i t e t r a n s m i t t e r s , f a d e m a r g i n s i n t h e s e s y s tems a r e t y p i c a l l y much l o w e r t h a n on t e r r e s t r i a l ' l i n k s . A t e l e v a t i o n a n g l e s above 5 ° , m u l t i p a t h and r e f r a c t i v e e f f e c t s a r e n o t l a r g e ; t h e p r i n c i p a l c a u s e o f b o t h a t t e n u - a t i o n and i n t e r f e r e n c e i s s c a t t e r i n g by h y d r o m e t e o r s [ 8 , 9 ] . W i t h an e v e r - i n c r e a s i n g demand f o r c h a n n e l c a p a c i t y t h e u se o f h i g h e r and h i g h e r f r e q u e n c i e s becomes i n e v i t a b l e [ 7 , 9 ] . F o r e xamp le , i n t h e U.S. t h e r e . ; a r e o v e r 4000 r e l a y s i n t h e 4 GHz b a n d ; f u r t h e r e x p a n s i o n i s b e i n g l i m i t e d by i n t e r f e r e n c e a t n e t w o r k j u n c t i o n s [ 6 , 7 , 1 0 ] and t h e number o f a v a i l a b l e s a t e l l i t e bands b e l o w 10 GHz i s s m a l l . I t i s c o n t e m - p l a t e d t h a t f r e q u e n c i e s above 10 GHz w i l l s oon be i n w i d e s p r e a d u s e . [ 1 0 - 1 3 ] . The a v a i l a b i l i t y o f medium power m i c r o w a v e s o u r c e s a t t h e h i g h e r f r e q u e n - c i e s , e f f i c i e n t d o w n c o n v e r t e r s [ 14 ,15 ] and m i c r owave i n t e g r a t e d c i r c u i t s [16] make t h e 10 t o 150 GHz r a n g e l o o k i n c r e a s i n g l y a t t r a c t i v e . F i e l d t r i a l s h a ve shown t h a t , a t l e a s t f r o m t h e t e c h n o l o g i c a l (as opposed t o p r o p a g a t i o n ) a s p e c t , mm-wave r a d i o s y s t e m s a r e p r a c t i c a l [ 1 2 , 1 7 ] . C h a r a c t e r i s t i c s o f P r o p a g a t i o n above 10 GHz: F i g . 1.1 shows t h e a t t e n u a t i o n by a " s t a n d a r d a t m o s p h e r e " [ 1 8 ] . I n t h e 10 t o 150 GHz r a n g e , s e v e r a l f e a t u r e s a r e o f i n t e r e s t : t h e ^ 0 r e s o n a n c e a t 22 .2 GHz and t h e 0^ r e s o n a n c e s a t 60 GHz and 118 GHz. She i n c r e a s e i n a t t e n u a t i o n i n t h e ^ 0 r e s o n a n c e band i s s m a l l enough t h a t u se o f t h i s band w o u l d n o t be a f f e c t e d . I n t h e 0^ r e s o n a n c e b a n d , howeve r , a t t e n u a t i o n i s so l a r g e t h a t o p e r a t i o n i n t h i s band w o u l d n o t be c o n t e m - p l a t e d f o r l o n g - h a u l t r a n s m i s s i o n . The band may however f i n d use i n a p p l i c a t i o n s where l i m i t e d r ange i s r e q u i r e d o r d e s i r a b l e . I n s h o r t , f o r most a s e s , two r ange s a r e c o n s i d e r e d : 10 -50 GHz and 70 -110 GHz. Above 10 GHz, f a d i n g by r a i n i s t he dominan t c a u s e o f p r o p a g a t i o n F i g . 1.1 Atmospheric attenuation i n the 10 - 400 GHz range (from [18]). o u t a g e s [ 1 0 , 1 2 ] . The t y p i c a l v a r i a t i o n o f s p e c i f i c a t t e n u a t i o n w i t h f r e - quency and r a i n r a t e i s g i v e n b y F i g . 1.4 f o r t h e 1-1000 GHz r ange [ 1 9 ] . F a d i n g due t o r a i n i s n o n - s e l e c t i v e , t hu s f r e q u e n c y o r s p a c e d i v e r s i t y c a n n o t be u s e d t o m a i n t a i n a v a i l a b i l i t y as i s t h e ca se b e l o w 10 GHz. A t t h e s e f r e q u e n c i e s , s h o r t e r hops and p o s s i b l y p a t h d i v e r s i t y must be u sed i n s t e a d [ 2 0 ] . The a l l o w a b l e r e p e a t e r s p a c i n g w o u l d g r e a t l y depend on t h e l o c a t i o n and w o u l d " a p p e a r t o be p r o h i b i t i v e l y s h o r t i n some a r e a s " [7] b u t a c c e p t a b l e i n o t h e r a r e a s . I n t h e s h o r t mm-wave r e g i o n , an tenna s o f r e a s o n a b l e s i z e (<1 m d i a m e t e r ) may be c o n s t r u c t e d w i t h s h a r p beams and l ow s i d e l o b e r a d i a t i o n [21 ] m a k i n g i n t r a - c i t y m i c r o w a v e l i n k s a p p e a r a t t r a c t i v e . O t h e r p o s s i b i l i - t i e s f o r h i g h c a p a c i t y d i s t r i b u t i o n i n c i t i e s i n v o l v e t h e u s e o f G a u s s i a n beams on s o - c a l l e d " H e r t z i a n c a b l e s " [ 2 2 ] . 1.2 A t m o s p h e r i c E f f e c t s 1.2.1 A t t e n u a t i o n - Ryde [23] p r e d i c t e d t h e a t t e n u a t i o n o f c e n t i m e t r e waves due t o r a i n . T h i s was b a s e d on s i n g l e s c a t t e r i n g by a d i e l e c t r i c s p h e r e as g i v e n by M i e and l a t e r , b y S t r a t t o n . M e d h u r s t [24] e x t e n d e d t h e c a l c u - l a t i o n s t o t h e m i l l i m e t r i c wave r e g i o n and c o r r e c t e d some o f R y d e ' s n u m e r i c a l r e s u l t s . More r e c e n t l y t h e e f f e c t s o f m u l t i p l e s c a t t e r i n g and o f c o n s i d e r i n g a beam as opposed t o a p l a n e wave we re s t u d i e d by L i n and I s h i m a r u [25]. They showed, i n g e n e r a l , t h a t a beam wave s u f f e r s some- wha t h i g h e r a t t e n u a t i o n t h a n a p l a n e wave and t h a t a t 3 and 5 mm w a v e l e n g t h s m u l t i p l e s c a t t e r i n g r e s u l t s i n a t t e n u a t i o n s 10% t o 30% b e l o w M e d h u r s t ' s r e s u l t s . C u r r e n t work by Roge r s and O l s e n (1976) [19] s u g g e s t s , howeve r , t h a t t he s o - c a l l e d " s i n g l e s c a t t e r i n g " t r e a t m e n t a c t u a l l y i n c l u d e s a l l f o r w a r d m u l t i p l e s c a t t e r i n g p r o c e s s e s and t h a t t h e e f f e c t o f " b a c k w a r d m u l t i p l e s c a t t e r i n g " i s n e g l i g i b l e . U s i n g T w e r s k y ' s m u l t i p l e s c a t t e r i n g f o r m u l a t i o n t h e y o b t a i n e d r e s u l t s v i r t u a l l y i d e n t i c a l t o t h o s e g i v e n by R y d e ' s method . I n t he f o l l o w i n g s i m p l i f i e d r e v i e w o n l y s i n g l e s c a t t e r i n g w i l l be c o n s i d e r e d . " S i n g l e S c a t t e r i n g " by S p h e r i c a l D rops The a t t e n u a t i o n o f a p l a n e wave i n a u n i f o r m d i s t r i b u t i o n o f s p h e r i c a l d r o p s . ( a l l t h e same s i z e ) i s g i v e n b y [23] 7TD2 T) ci = 0 . 4343 • N • ~ - f , m) dB/km " (1) - 3 whe re N i s t h e d e n s i t y o f d r o p s (m ) D i s t he d r op d i a m e t e r (cm) m = n - j n x i s t n e comp lex r e f r a c t i v e i n d e x o f w a t e r f i s t h e r a t i o o f e n e r g y a b s o r b e d and s c a t t e r e d t o t h a t i n c i d e n t a upon t h e p r o j e c t e d a r e a o f a d r o p . T a b l e 1.1 [24] g i v e s t h e comp lex r e f r a c t i v e i n d e x o f w a t e r , m, as a f u n c t i o n o f w a v e l e n g t h and t e m p e r a t u r e . Know ing m, t h e p a r a m e t e r f may be c a l c u l a t e d f o r a p a r t i c u l a r A. A t y p i c a l g r a p h o f f v s . D/A [23] c l i s i n c l u d e d h e r e as F i g . 1 .2 . I t shows t h a t a t t e n u a t i o n b y r a i n i s mo s t p r o n o u n c e d i n t h e mm-x^ave r a n g e . To r e l a t e t he a t t e n u a t i o n i n (1) t o r a i n r a t e , R, a r e l a t i o n s h i p b e t w e e n N and R i s r e q u i r e d . T h i s i s g i v e n , i n t e r m s ' o f t h e t e r m i n a l v e l o c i t y o f a f a l l i n g d r o p , by R = 1.885 • v • N • D 3 (mm/hr) (2 ) The t e r m i n a l v e l o c i t y i n (2) i s dependen t on d r op d i a m e t e r . The d e p e n - d e n c e , as measured by Gunn and K i n z e r [ 2 4 ] , i s shown i n F i g . 1 . 3 . The c o e f f i c i e n t o f a t t e n u a t i o n f o r u n i f o r m r a i n o f a s i n g l e d r o p s i z e may now be c a l c u l a t e d f o r a r ange o f d r op s i z e s and w a v e l e n g t h s . These r e - s u l t s [24] a r e g i v e n i n T a b l e 1.2. I t i s o b s e r v e d t h a t a t X = 4 mm a r a i n f a l l o f r e l a t i v e l y s m a l l d r op s can cau se t e n t i m e s t h e a t t e n u a t i o n o f a r a i n f a l l o f l a r g e d r op s a t t h e same r a i n r a t e . T h i s happens b e c a u s e X[mm] n nx • 3 3.51 2.01 4 3.94 2,27 5 4.37 2.52 10 8.25 1.83 Table 1.1 Refractive and absorptive Indices of water at 20°C (from [24]). Wavelength Drop Diameter [mm] [mm] 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 3 1.85 1.49 0.66 0.41 0.28 0,21 0.17 0.14 0.12 0.10 0.092 0.083 0.076 4 1.15 1.15 0.67 0.41 0.28 0.21 0.17 0.14 0.12 0.11 0.094 0.085 0.077 5 0.46 0.74 0.68 0.42 0.28 0.21 0.17 0.14 0.12 0.11 0.096 0,087 0.079 10 0.097 0.14 0.20 0.22 0.22 0.21 0.18 0.15 0.12 0.11 0.099 0.091 0.083 Table 1.2 Normalized specif ic attenuation [(dB/km)/(mm/hr)] by mono- disperse rain (from [24]). RANGh OF DROP SIZES FOR X = 4 m m ——(>j 6 0.1 O.OI 1 QOI Ql 0.3 1.0 10 D/X F i g . 1.2 Ratio of effective scattering and absorption cross section to physical cross section for a sphere of water (calculated using the refractive .index of water for A = 1 cm)(from [23]). TERMINAL VELOCITY [m/sec] 0 I 2 3 4 5 6 7 DROP DIAMETER [mm/] Fig . 1.3 Terminal velocity of rain drops vs. drop diameter (from [24]). 8. at short wavelengths, f i s s imilar for a l l drop sizes so that by d i s t r i - buting rain into smaller drops, which increases the projected area of the ra in , the attenuation increases. (At longer wavelengths f decreases more cL TTD 2 rapidly than — — : N with decreasing D so here, the larger drops cause - highest attenuations.) Actual rain is composed of drops with a continuous range of d ia - meters from 0.5 mm to 7mm. The drop size distr ibution varies with ra in rate; an average relat ion i s given by Table 1.3 (Laws and Parsons [56]). Combining this with attenuation by rain of a single drop s ize , attenuation by actual rain vs. rain rate, as shown in Table 1.4 has been calculated [24], A graph of specif ic attenuation vs. frequency at various rain rates [19] i s given by F ig . 1.4. The above prediction of attenuation i s based on a one-to-one cor- respondence of drop size distr ibut ion and rain rate. Zavody and Harden [26] have shown that substantial deviations from the Laws and Parsons d i s - tribution do, however, occur. This may account for some of the observed scatter [8,24,27] i n experimental attenuation vs. ra in rate data. Attenuation in Non-Uniform Rain: It is known that rain generally occurs i n ce l l s of l imited ex- tent [28,29]. In practice the f u l l spat ia l variat ion of ra in rate i s not measured but, rather, point rain rates are sampled at various locations along the path. That i s , the path is broken into segments each with a rain gauge and for each segment the attenuation is calculated. The tota l excess path attenuation is thus the sum of a l l p a r t i a l attenutaions. n n A = I A A = I. a ^ ) • 1 ± (3) i=l i=l where B. is the rain rate as measured by the i*"*1 rain gauge Precipitation Percent of tota l volume rate (mm/hour) Drop size (cm) 0.25 1.25 2.5 5 12.5 25 50 100 150 (mean in interval) 0.05 28.0 10.9 7.3 4.7 2.6 1.7 1.2 1.0 .1.0 . 0 . 1 50.1 37.1 27.8 20.3 11.5 7.6 5.4 4.6 4.1 0.15 18.2 31.3 32.8 3.1.0 24.5 18.4 12.5 8.8 7.6 0.2 3.0 13.5 19.0 22.2 25.4 23.9 19.9 13.9 11.7 0.25 0.7 4.9 7.9 11.8 17.3 19.9 20.9 17.1 13.9 0.3 1.5 3.3 5.7 10.1 12.8 15.6 18.4 17.7 0.35 0.6 1.1 2.5 4.3 8.2 10.9 15.0 16.1 0.4 0.2 0.6 1.0 2.3 3.5 6.7 9.0 11.9 0.45 0.2 0.5 1.2 2.1 3.3 5.8 7.7 0.5 0.3 0.6 1.1 1.8 3.0 3.6 0.55 0.2 0.5 1.1 1.7 2.2 0.6 0.3 0.5 1.0 1.2 0.65 0.2 0.7 1.0 0.7 0.3 Table' 1.3 ] Drop size distribution for various rain rates (Laws and Parsons)(from [24]). .X ° Rain Rate : [mm/hr] [mm] 0.25 1.25 2.5 5 12.5 25 50 100 150 3 .250 1-29 2.19 3.68 - 7.08 11.7 19.6 33. 7 46.8 4 .204 1.03 1 1.81 3.15 6.27 10.8 18.3 31. 5 43.8 5 .159 .764 1.43 2.63 5.46 9.86 17.0 29. 4 40.9 10 .035 .210 .447 .933 2.43 4.87 9.59 18. 4 26.5 Table .1.4 Specific attenuation for various rain rates assuming the Laws and Parsons drop size distr ibution (from [24]). 10 . FREQUENCY (GHz) F i g . 1.4 Spec i f i c attenuation as a function of frequency for.coherent wave propagation through uniform r a i n . The curves are based on Laws and Parsons dropsize d i s t r i b u t i o n and the terminal v e l o c i t i e s of Gunn and Kinzer . Rain temperature of 20°C. Rain temperature of. 0°C. (from [19]) 1 1 . t h v l i i s t he l e n g t h o f t h e i segment (2, 1 . = L , p a t h l e n g t h ) i a i ^ i ^ '* ' s a t t e n u a t i ° n x n dB/km a t r a i n r a t e , I f t h e r a i n r a t e s a t each gauge a r e s i m i l a r o r i f s p e c i f i c a t t e n u a t i o n and r a i n r a t e a r e l i n e a r l y r e l a t e d : n R. 1. A - a x ( I ) • L (4) i = l n R. 1. r i i where l — - — i s t h e s o - c a l l e d p a t h - a v e r a g e r a i n r a t e . i = l L Mos t p u b l i s h e d e x p e r i m e n t a l wo rk compares e x c e s s p a t h a t t e n u a t i o n d i r - e c t l y w i t h p a t h - a v e r a g e r a i n r a t e a l t h o u g h t h i s i s n o t s t r i c t l y c o r r e c t . D i f f e r e n t i a l A t t e n u a t i o n I t h a s been shown t h a t l a r g e r a i n d r o p s t e n d t o be f l a t t e n e d a t t h e b o t t o m [ 3 0 ] . T h i s w o u l d s u g g e s t t h a t a t t e n u a t i o n b y r a i n i s p o l a r i z - a t i o n d e p e n d e n t . Measurements have shown t h a t a t t e n u a t i o n i s l a r g e r f o r h o r i z o n t a l p o l a r i z a t i o n t h a n v e r t i c a l p o l a r i z a t i o n [ 3 1 ] . The d i f f e r e n - t i a l a t t e n u a t i o n , h o w e v e r , i s l e s s t h a n 15% o f t h e a v e r a g e a t t e n u a t i o n . E f f e c t s o f U p d r a f t s V e r t i c a l w i n d m o d i f i e s t h e t e r m i n a l v e l o c i t y o f r a i n d r o p s s u ch t h a t t h e d r o p d e n s i t y i n a i r w o u l d be d i f f e r e n t t h a n i n d i c a t e d b y t h e s u r f a c e r a i n r a t e . S m a l l d r o p s a r e p a r t i c u l a r l y a f f e c t e d b e c a u s e o f t h e i r l o w t e r m i n a l v e l o c i t y . As t h e s e c au se a l a r g e p o r t i o n o f t he a t t e n u a t i o n a t 4 ism w a v e l e n g t h s , t h e e f f e c t o f u p d r a f t s ( o r d o w n d r a f t s ) c o u l d be subs tan t i a l . Effect of T e m p e r a t u r e - T e m p e r a t u r e a f f e c t s a t t e n u a t i o n by r a i n i n s omuch as t he complex re f rac t ive i n d e x o f w a t e r i s t e m p e r a t u r e d e p e n d e n t . W h i l e M e d h u r s t [24] reports that, at X = 5 mm, t h e change i n a t t e n u a t i o n f o r t e m p e r a t u r e s between Q° and 40°C i s as l a r g e as 17%, more r e c e n t c a l c u l a t i o n s by 12 . Roge r s and O l s e n [19] have shown t h a t t h e change i s o n l y 4%. A t t e n u a t i o n by W a t e r V a p o u r , Oxygen and Fog w a t e r v a p o u r i t s e l f , as measured by h u m i d i t y , c a u s e s a t t e n u a t i o n . A t 100% r e l a t i v e h u m i d i t y , a t 1 0°C , a t t e n u a t i o n o f 4 mm waves i s abou t 0 .5 d3/km ( e x t r a p o l a t e d f r o m Bu s sey [ 3 2 ] ) . Of t h e o t h e r ga se s i n t he a t m o s - p h e r e o n l y o x ygen c a u s e s s i g n i f i c a n t l o s s e s , 0 . 3 dB/km a t s e a l e v e l [ 1 8 ] . Fog a t t e n u a t e s m i c r o w a v e r a d i a t i o n by t h e same mechan i sm as r a i n . The p a r a m e t e r f i s s m a l l e ven f o r s h o r t mm-waves so t h a t a t t e n u a t i o n i s n o t a l a r g e ; mea su red a t t e n u a t i o n s o f 1 dB/km a t 90 GHz have b e e n r e p o r t e d b y W e i b e l and D r e s s e l [ 3 3 ] . 1 .2 .2 C r o s s P o l a r i z a t i o n The shape o f a f a l l i n g d r op may be a p p r o x i m a t e d by an o b l a t e s p h e r o i d , t h e m i n o r a x i s o f w h i c h i s g e n e r a l l y a l i g n e d i n t h e d i r e c t i o n o f f a l l . M e a s u r e m e n t s , h o w e v e r , have shown t h a t an a v e r a g e c a n t i n g o f a xe s away f r o m t h e v e r t i c a l does o c c u r [30.]. ( T h i s c o u l d p o s s i b l y , be due t o g r a d i e n t s i n w i n d v e l o c i t y o r a t m o s p h e r i c t u r b u l e n c e . ) The d r o p s w h i c h a r e s u b j e c t t o c a n t i n g c o u p l e power be tween v e r t i c a l and h o r i z o n t a l p o l a r i z a t i o n s as shown t h e o r e t i c a l l y by O g o u c h i and Hogg [ 3 4 , 3 5 , 3 6 ] . Such c r o s s p o l a r i z a t i o n may s e r i o u s l y l i m i t t h e s i m u l t a n e o u s u s e o f o r t h o g o n a l p o l a r i z a t i o n s . Above 60 GHz, h o w e v e r , d e p o l a r i z a t i o n may be l o w e r b e - cau se a t t e n u a t i o n by t h e s m a l l e r ( a l m o s t s p h e r i c a l ) d r o p s p r e d o m i n a t e s [ 3 1 ] . 1.3 Considerations i n an E x p e r i m e n t a l Transmission Link at 75 GHz 1.3.1 B a c k g r o u n d An e x a m i n a t i o n o f p r o p a g a t i o n s t u d i e s i n t e n t on o b s e r v i n g f a d i n g due to r a in shows f r e q u e n c i e s r a n g i n g f r o m 8 GHz t o 110 GHz and t o t a l transmission l e n g t h s o f 100 m t o 45 km. R e f e r t o T a b l e 1.5 f o r a p a r t i a l b u t r e p r e s e n t a t i v e l i s t o f e x p e r i m e n t s . I n an a t t e m p t t o compare s t u d i e s 1 3 . R e f . No. A u t h o r s I f r a d a r F r e q . P a t h L e n g t h " 7 5 GH l i n k [GH ] [m] T r a n s m i s : 37 B l e v i s , Dohoo, McCo rm ick / L e n g t h 1 8.0 15 ,800 650 38 R o b e r t s o n , K i n g 9.4 274 20 39 S k e r j a n e c , Samson 10 .0 4 ,700 370 24 Ha thaway , Evans 11 .4 45 ,000 4 , 800 40 V o r s t , G a n d i s s a r t 11 .7 1,000 230 39 S k e r j a n e c , Samson 14.4 4 ,700 790 37 B l e v i s , Dohoo, McCo rm ick 15 .0 15 ,800 2 , 800 41 S t r a i t o n 15 .3 20,000. 3 ,700 42 , -43 Semp lak , T u r r i n 18 .5 6 ,400 1,600 44 A n d e r s o n e t a l . 24 .0 1,950 740 24 Rado • 24 .0 3,970 1,500 38 R o b e r t s o n , K i n g 27 .5 383 180 43 Semp lak 30.9 1,900 1,020 24 Adam e t a l . 31 .3 2 ,000 1,080 45 H a r r o l d 34 . 8 6 ,900 8 ,100 24 Okamura e t a l . • 34.9 400 480 24 Okamura e t a l . / 34.9 3,550 4 , 200 24 Funakawa, K a t o 34.9 24 ,000 14 ,000 40 V o r s t , G a u d i s s a r t / 35.0 1,000 1,200 46 Roche e t a l . 35 .0 8,000 4 , 7 0 0 46 Roche e t a l . 35 .0 32 ,000 19 , 000 47 N o r b u r y , W h i t e / 35.8 224 270 26 Za vody , Ha rden 36 .0 220 130 24 U s i k o v e t a l . / 36.8 50 60 24 U s i k o v e t a l . / 44 .1 50 70 48 M u e l l e r 48 .4 365 280 24 U s i k o v e t a l . / 69 .7 50 96 33 W e i b e l 90 .5 2,000 2 ,200 49 Ho f fman e t a l . 94 .0 19 ,000 20 ,000 50 L a n e , G o r d o n - S m i t h , e t a l . / 101 .0 150 320 26 ,Zavody & Ha rden 110 .0 220 240 5 1 . 52 L l e w e l l y n - J o n e s , Zavody 110 .0 2 ,650 2 ,900 "rable 1.5 A c o m p a r i s o n o f p a t h l e n g t h s u s e d i n v a r i o u s p r o p a g a t i o n s t u d i e s . 14.. done a t d i f f e r e n t f r e q u e n c i e s , p a t h l e n g t h s were n o r m a l i z e d t o ones t h a t w o u l d g i v e t h e same a t t e n u a t i o n a t 75 GHz u s i n g t h e r e l a t i v e c o e f f i c i e n t s o f a t t e n u a t i o n f o r r a i n a t 50 mm/hr. F i g u r e 1.4 g i v e s a p l o t o f t h e s e c o e f f i c i e n t s v e r s u s f r e q u e n c y . T a b l e 1.6 shows t h e number o f t h e s e s t u d - i e s i n v a r i o u s c l a s s e s o f n o r m a l i z e d p a t h l e n g t h ; t h e s p r e a d i n p a t h l e n g t h s i s a l m o s t t h r e e o r d e r s o f m a g n i t u d e . 1.3.2 E x p e c t e d R a i n R a t e s i n V a n c o u v e r The c l i m a t e i n V a n c o u v e r i s m o d e r a t e l y w e t (1070 mm/year) and s u b j e c t t o l i t t l e t h u n d e r s h o w e r a c t i v i t y . R a i n r a t e d i s t r i b u t i o n s a r e n o t y e t a v a i l a b l e f o r V a n c o u v e r b u t e s t i m a t e s may b e o b t a i n e d b y e x a m i n - i n g p u b l i s h e d v a l u e s [ 2 9 , 3 2 , 5 3 , 5 4 ] f o r o t h e r l o c a t i o n s ; r e f e r t o T a b l e 1 .7 . I t i s f e l t t h a t o f the i n f o r m a t i o n a v a i l a b l e , p e r h a p s P o r t l a n d , Oregon i s most r e p r e s e n t a t i v e o f c o n d i t i o n s i n V a n c o u v e r . T h i s w o u l d i n - d i c a t e r a i n r a t e s e x c e e d i n g 50 mm/hr ( s u b j e c t t o a 1 m i n u t e a v e r a g i n g t i m e ) m i g h t o c c u r 10 m i n u t e s / y e a r . R a i n r a t e s e x c e e d i n g 100 mm/hr w o u l d o c c u r l e s s t h a n 1 m i n u t e / y e a r . The r e s u l t s o f B u s s e y [32] a r e n o t u s e d h e r e b e c a u s e t h e y i n c l u d e o n l y t he o c c u r e n c e o f l o n g b u r s t s o f i n t e n s e r a i n . I t i s n o t e d t h a t s u ch e s t i m a t e s (a s above ) a r e v e r y s e n s i t i v e t o l o c a l c o n d i t i o n s ; a v a r i a b i l i t y o f two o r d e r s o f m a g n i t u d e i n r a i n r a t e d i s t r i b u t i o n s e x i s t s w i t h i n t h e c o n t i n e n t a l U .S . a l o n e [ 5 3 ] . I t i s a p p a r e n t , then, t h a t an a c c u r a t e - m e a s u r e m e n t o f t h e l o c a l r a i n r a t e d i s - t r i b u t i o n , per s e , i s i m p o r t a n t . I n d e e d , i n c a l c u l a t i n g t h e r e l i a b i l i t y of a given path, more u n c e r t a i n t y a p p e a r s t o e x i s t i n t h e r a i n r a t e d i s - t r i b u t i o n than i n t he r e l a t i o n be tween a t t e n u a t i o n and r a i n r a t e . 1.3.3 E s t i m a t e d R e l i a b i l i t y o f Two P a t h s i n V a n c o u v e r Because past work p r o v i d e s l i t t l e g u i d a n c e f o r c h o o s i n g t h e 1 5 . N o r m a l i z e d P a t h L e n g t h s [m] Number < 100 4 100 t o 1,000 12 1,000 t o 10 ,000 13 > 10 ,000 3 T a b l e 1.6 P r o p a g a t i o n s t u d i e s c l a s s e d by n o r m a l i z e d p a t h l e n g t h . A v e r a g i n g L o c a t i o n Time [min] S a l t L a k e C i t y , U t a h 1 P o r t l a n d , O r e . 1 M i a m i , F l a . 1 B e d f o r d s h i r e , E n g l a n d 2 C r a w f o r d H i l l , N . J . 0 .15 C o r v a l l i s , O r e . V a n c o u v e r , B .C. 5 Time i n m i n / y e a r R a i n R a t e E x c e e d e d R e f e r e n c e No. 50 mm/hr 100 mm/hr 5 < h [53] 9 h [53] 400 80 [53] 6 < 1 [29] 80 20 [54] < h < h [54] 2.5 ~ [32] T a b l e 1.7 P r o b a b i l i t y o f s e l e c t e d p o i n t r a i n r a t e s i n v a r i o u s l o c a t i o n s . 16. proper path length of a propagation study i t is instructive to.examine the r e l i a b i l i t y (with respect to propagation) of part icular microwave l inks . Two links w i l l be analyzed here, one of length 2 km and the other of 10 km. It w i l l be assumed that each has the same fade margin (in free space) of 40 dB. Outages could result from both precipitat ion and mult i - path effects and for this analysis, both events w i l l be regarded as d i s - jo int so that the total outage w i l l be the sum of the respective outages, a) Length = 2 km At 75 GHz no multipath fading would be expected to occur for path lengths below 3.5 km [55]. Gaseous absorption of 0.7 dB/km [32] w i l l reduce the fade margin to 38.6 dB. An attenuation of greater than 19.3 dB/km would then cause an outage. Referring to F i g . 1.4, this would result from a path-average rain rate of 55 mm/hr. It has been shown that the s ta t i s t i c s of path-average rain rate are similar to those of point rain rate subject to a unique averaging time related to the path length [53]. The appropriate averaging time for this path i s 16 seconds. How- ever, for rates below 60 mm/hr the point rain rate d is tr ibut ion is inde- pendent of averaging times between 1.5 sec and 120 sec.[53] so that the 1 minute averages of Section 1 .3 .2 .wi l l suffice to describe path-average rain rate. This gives an outage time of 8 minutes/year, b) Length = 10 km On this l i n k , multipath fading would be expected to occur [55] but experimental values of this fading are not available for the 4 mm band. One may estimate the outage time, however. I t has been shown [55] that the attenuation distr ibut ion is independent of path length, L , and 3 wave-length, A , as long as the rat io L /A remains constant. Thus the attenuation distr ibution of this path should be the same as, for example, 17 . p a t h s o f : f = 15 GHz L = 16.9 km f = 8 GHz L = 20.9 km P u b l i s h e d r e s u l t s [1] i n d i c a t e an ou tage t i m e o f 50 m i n u t e s / y e a r f o r t h o s f r e q u e n c i e s and l e n g t h s . A c c o u n t i n g f o r oxygen and w a t e r v a p o u r a b s o r p t i o n t h e f a d e m a r - g i n o f t h i s p a t h i s r e d u c e d t o 33 dB [ 3 2 ] . R e f e r r i n g t o F i g . 1.4 an o u t a g e w o u l d o c c u r f o r a p a t h - a v e r a g e r a i n r a t e o f 6 mm/hr. The s t a t i s - t i c s o f r a i n r a t e on t h i s 10 km p a t h s h o u l d be t h e same as t h o s e o f p o i n t r a i n r a t e s u b j e c t t o a 39 s e cond a v e r a g i n g t i m e [ 5 3 ] . By n o r m a l i z i n g a t y p i c a l r a i n r a t e d i s t r i b u t i o n t o t h e f i g u r e o f 10 m i n / y e a r a t 50 mm/hr, a r a i n r a t e o f 6 mm/hr w o u l d b e . e x c e e d e d 300 m i n u t e s / y e a r . The t o t a l o u t a g e t i m e o f t h i s 10 km l i n k i s e x p e c t e d t o be 350 m i n u t e s / y e a r . The a v a i l a b i l i t i e s o f t h e two l i n k s i n d i c a t e t h a t , i n V a n c o u v e r a 2 km l i n k w o u l d be o f a r e l i a b i l i t y s u i t a b l e f o r t e l e p h o n y and t h a t a 10 km l i n k w o u l d be b e t t e r s u i t e d t o CATV a p p l i c a t i o n s [ 1 ] . 1 .3 .4 C o n s i d e r a t i o n s i n P a t h S e l e c t i o n A l o n g p a t h has e a s i l y - m e a s u r e d v a l u e s o f a t t e n u a t i o n b u t i s f a d e d o u t q u i t e o f t e n so t h a t no k n o w l e d g e o f e v e n t s b e l o w a g i v e n p r o b a - b i l i t y i s o b t a i n e d . I t i s a l s o d i f f i c u l t t o a d e q u a t e l y measu re the r a i n r a t e p r o f i l e on s u ch a p a t h . A s h o r t l i n k , on t h e o t h e r h a n d , g e n e r a l l y has s m a l l v a l u e s o f e x c e s s p a t h a t t e n u a t i o n w h i c h may be d i f f i c u l t t o measure b u t i s r a r e l y f a d e d ou t so t h a t e v e n t s o f v e r y l ow p r o b a b i l i t y w i l l be m e a s u r e d . The r a i n r a t e measurement on t he s h o r t p a t h i s a l s o more t r a c t a b l e . A c o m p r e h e n s i v e s t u d y w o u l d r e q u i r e t h a t a l l b u t t h e r a r e s t o f r a i n i n d u c e d f a d e s be o b s e r v e d and t hu s a s h o r t p a t h w o u l d b e d e s i r a b l e i n an i n i t i a l s t u d y . From the r e s u l t s on a s h o r t p a t h and b y a s c e r t a i n i n g 18. the s p a t i a l v a r i a t i o n of r a in over the long path, i t should be. possible to predic t the performance of the l a t t e r . A subsequent study of the long path with i t s more complex charac te r i s t i c s would then become appropriate. 1.4 Scope of the Thesis 1.4 .1 Thesis Objective The ult imate objectives of this research program could be stated as fo l lows : 1) To es tab l i sh a mi .1 lime t r i e wave l i n k with appropriate weather moni- tor ing apparatus and a sui table data gathering system. To operate the system for a s u f f i c i e n t l y long period of time i n order to acquire a large data base of atmospheric propagation-related events. 2) To es tab l i sh the r e l a t i on between mm-wave propagation charac te r i s t i c s i n the atmosphere and the various phys ica l phenomena that affect these cha rac t e r i s t i c s . 3) To be able to predic t the propagation s t a t i s t i c s of a path i n this l o c a t i o n . I t i s desirable to predict th i s from the knowledge of (2) and the s t a t i s i t c s of the "causes". The work described i n th i s thesis provides the bas ic features of an experimental system designed to achieve the above ul t imate objec- t i ve s . S p e c i f i c a l l y , the points covered are: ,1) I d e n t i f i c a t i o n of the parameters af fect ing mm-wave propagation i n the atmosphere and of problems associated with propagation s tudies . 2) Establishment of a m i l l i m e t r i c wave l i n k capable of automatically measuring excess path attenuation. 3) I n s t a l l a t i o n of weather monitoring apparatus for the automatic measurement of parameters related to excess path at tenuat ion. 19 . 4) I m p l e m e n t a t i o n o f a s y s t e m t o r e c o r d , i n a f o r m s u i t a b l e f o r l a t e r a n a l y s i s , d a t a f r o m t h e m i c r o w a v e l i n k and t h e w e a t h e r s e n s o r s . 5) Deve l opment o f t e c h n i q u e s f o r e d i t i n g d a t a so as t o a l l o w a c c u m u l a - t i o n o f a d a t a b a s e o f p r o p a g a t i o n - r e l a t e d e v e n t s . T h i s t h e s i s i s b a s i c a l l y c o n c e r n e d w i t h t he d e s i g n and i m p l e - m e n t a t i o n o f a s y s t e m . The work done i n v o l v e s t h e i n s t a l l a t i o n o f e q u i p - ment t o measu re a d i v e r s e r ange o f phenomena and t h e c h a n e l l i n g o f l a r g e vo l umes o f d a t a t h r o u g h s e v e r a l s t a g e s o f p r o c e s s i n g . T h i s was accomp- l i s h e d b y m a k i n g e f f e c t i v e use o f a v a i l a b l e r e s o u r c e s and w i t h i n c e r t a i n b u d g e t a r y c o n s t r a i n t s . The t h e s i s c o v e r s a d i v e r s e r a n g e o f t o p i c s . O f n e c e s s i t y , more d e t a i l i s i n c l u d e d i n e ach s e c t i o n t h a n e x p e r t s i n a p a r t i c u l a r f i e l d m i g h t deem w a r r a n t e d . 1 .4 .2 T h e s i s O u t l i n e A m i l l i m e t r i c wave l i n k w h i c h a l l o w s c o n t i n u o u s measurement o f e x c e s s p a t h a t t e n u a t i o n a t 74 GHz (and o p t i o n a l l y 35 GHz) i s t he s u b j e c t o f C h a p t e r I I . I n c l u d e d a r e d e s c r i p t i o n s o f t he v a r i o u s s u b - s y s t e m s i n t h e l i n k as w e l l as t h e c a l c u l a t e d and measu red s y s t e m p e r f o r m a n c e . C h a p t e r I I I d e a l s w i t h t h e m e t e o r o l o g i c a l s e n s o r s b y w h i c h p a r - a m e t e r s a f f e c t i n g e x c e s s p a t h - a t t e n u a t i o n a r e mea su red . The s e n s o r s i m - p l e m e n t e d a r e a n e t w o r k o f t i p p i n g b u c k e t r a i n gauges and u n i t s t o mea - s u r e t e m p e r a t u r e and w i n d v e l o c i t y . C h a p t e r IV i s c o n c e r n e d w i t h t he r e c o r d i n g o f d a t a f r o m the m i c r o w a v e and w e a t h e r s e n s o r s and t h e i r e v e n t u a l t r a n s f e r i n t o a p e r m - a n e n t d a t a b a s e . The t o p i c s c o v e r e d a r e a m i n i c o m p u t e r i n t e r f a c e , r e a l t i m e d a t a l o g g i n g w i t h a m i n i c o m p u t e r and p o s t p r o c e s s i n g o f d a t a on an IBM 370 c o m p u t e r . 2 0 . R e s u l t s o f o p e r a t i o n a t 74 GHz w i t h t h e r e a l t i m e d a t a a c q u i s i - t i o n s y s t e m f r o m November, 1976 t o M a r c h , 1977 a r e g i v e n i n C h a p t e r V . They r e p r e s e n t a l i m i t e d s e t o f d a t a and a r e i n c l u d e d t o c o n v e y t h e c h a r - a c t e r t h e d a t a measu red and t he v i a b i l i t y o f t h e t e c h n i q u e s u s ed i n t h i s t h e s i s . S u g g e s t i o n s f o r f u r t h e r d e v e l o p m e n t s on t h e s y s t ems d e s c r i b e d i n t h i s t h e s i s and t h e c o n c l u s i o n s a r e c o n t a i n e d i n C h a p t e r V I . 2 1 . CHAPTER I I MILL IMETRIC WAVE L INK AND MEASUREMENT SYSTEMS 2.1 I n t r o d u c t i o n T h i s c h a p t e r d e s c r i b e s t he d e s i g n o f a m i l l i m e t r i c wave p r o p a - g a t i o n l i n k u sed i n t h e measurement o f . e x c e s s p a t h a t t e n u a t i o n ( m a i n l y ) due t o p r e c i p i t a t i o n . I t i s a r a d a r - t y p e p a t h o f t o t a l t r a n s m i s s i o n l e n g t h 1.8 km o p e r a t i n g a t a f r e q u e n c y o f abou t 74 GHz w i t h a 40 dB f a d e m a r g i n . The l i n k c an a l s o be o p e r a t e d a t 35 GHz w i t h few m o d i f i c a t i o n s . Much o f t h e d e s i g n i s p r e d i c a t e d upon t h e f a c i l i t i e s a v a i l a b l e w i t h l i t t l e c h o i c e i n t h e f o l l o w i n g a r e a s : 1.. A n t e n n a s 2. R e c e i v e r 3. T r a n s m i s s i o n p a t h The s c o p e o f d i s c u s s i o n s i n t h i s s e c t i o n i s n e c e s s a r i l y r e s t r i c t e d b y t h e s e c o n s i d e r a t i o n s . A g e n e r a l d e s c r i p t i o n o f t h e p r o p a g a t i o n l i n k i s g i v e n i n S e c - t i o n 2.2 t o g e t h e r w i t h a p r e d i c t i o n o f i t s f a d e m a r g i n . T h i s c a l c u l a t i o n i s l a r g e l y b a s e d on measurements a nd/o r a n a l y s i s o f t h e l i n k ' s c o n s t i t u - e n t s u b - s y s t e m s as d e t a i l e d i n S e c t i o n 2 . 3 . The measu red f a d e m a r g i n o f t h e s y s t e m and a c o m p a r i s o n w i t h t h e p r e d i c t e d v a l u e i s g i v e n i n S e c t i o n 2 . 4 . F i n a l l y , a summary o f t he m i l l i m e t r i c wave l i n k c h a r a c t e r i s t i c s i s p r e s e n t e d i n S e c t i o n 2 . 5 . 2 . 2 . S y s tem D e s c r i p t i o n A m i l l i m e t r i c - w a v e l i n k o f t h e r a d a r t y p e i s u s e d h e r e , t h a t i s , t h e s i g n a l t r a v e r s e s t he p a t h t w i c e v i a a p a s s i v e r e f l e c t o r . S e p a r a t e t r a n s m i t t i n g and r e c e i v i n g a n t e n n a s , e a ch 1 m e t e r d i a m e t e r p a r a b a l o i d d i s h e s a r e u s e d . These a r e p o s i t i o n e d 20 m e t r e s a p a r t on t h e r o o f o f t h e MacLeod B u i l d i n g . The d i r e c t c o u p l i n g be tween t h e a n t e n n a s i s b e l o w t h e r e c e i v e r 22 . n o i s e l e v e l . The a n t e n n a s a r e mounted a t an e l e v a t i o n o f 148 m e t r e s above 2 s e a l e v e l . A p l a n e r e f l e c t o r , 1 m , i s l o c a t e d abou t 900 m away a t an e l e v a t i o n o f 178 m, g i v i n g a t o t a l t r a n s m i s s i o n l e n g t h o f 1.8 km. The p a t h i s o v e r f l a t g r ound and s e v e r a l b u i l d i n g s w i t h a minimum c l e a r a n c e o f 4 m. D e t a i l s o f t h e p a t h a r e g i v e n by F i g . 2 . 1 . A 74 GHz s o u r c e ( l o c a t e d one f l o o r b e n e a t h t h e a n t e n n a s ) s u p p l i e s a c o n t i n u o u s wave s i g n a l t o t he t r a n s m i t t i n g a n t e n n a v i a a w a v e g u i d e s y s - tem. A m i s e r , l o c a t e d a t t h e r e c e i v i n g a n t e n n a , d o w n - c o n v e r t s t h e s i g n a l r e c e i v e d t o a n i n t e r m e d i a t e f r e q u e n c y w h i c h i s t r a n s m i t t e d t h r o u g h c o - a x i a l c a b l e t o a r e c e i v e r l o c a t e d n e a r the s o u r c e . R e f e r t o F i g . 2 .2 f o r a b l o c k d i a g r a m o f t h i s s y s t e m . P h o t o g r a p h s o f v a r i o u s component s . ;a re g i v e n i n F i g s . 2 . 3 , 2.4 and 2 . 5 . C a l c u l a t e d Fade M a r g i n : U s i n g t h e r e s u l t s d e v e l o p e d i n S e c t i o n 2 . 3 , t h e f a d e m a r g i n o f t h i s s y s t e m may be c a l c u l a t e d . L f F r e e - s p a c e l o s s (20 L o g 1 Q C ^ ) ) : 128 .5 dB L Gaseous A b s o r p t i o n ( 0 . 7 dB/km) 1.2 dB L R e f l e c t o r " L o s s " 5.2 dB r L , Wavegu ide L o s s e s ( t o t a l ) 8.6 dB w/g G^, G^: A n t e n n a G a i n s 49 .5 and 48 dB r e s p e c t i v e l y T R P ; K l y s t r o n Power O u t p u t , P +27. dBm o J o P = p - L £ - L - L - L , •+ G + G_. = - 19 dBm r e c v r o f g r w/g r R W i t h t he c u r r e n t m i x e r s e n s i t i v i t y o f - 81 dBm, t h i s i s a f a d e m a r g i n o f 62 dB. . 2 .3 Sub - Sy s tems 2 .3 .1 An tenna s The a n t e n n a s u sed i n t h i s e x p e r i m e n t a r e b o t h c e n t e r - f e d p a r a - A N T E N N A S Fig. 2.1 Transmission path (a) Aer ia l view (b) Side view. Circles mark the 5 rain gauges. 24. PARABOLOID REFLECTOR ANTENNAS j RECEIVING ANTENNA 8 8 0 m PASSIVE REFLECTOR ( Im? ) TRANSM ITT ING A N T E N N A R O O F _ _ " L A B O R A T O R Y " 2 1. 7 4 GHz S O U R C E 2 . R E F E R E N C E - S I G N A L M I X E R 3. R E C E I V E D - S I G N A L M I X E R 4- PHASE - L O C K E D R E C E I V E R Microwave system: block diagram F i g . 2.3 The r e f l ec to r at Gage Tower ' C ' . Past i t and to the r i gh t i s the MacLeod Bui ld ing where the antennas are i n s t a l l e d . F i g . 2.4 The transmit t ing antenna, the anemometer, a Stevenson's screen and a prototype capaci tat ive r a in gauge. 26. 74 GHz K L Y S T R O N I S O L A T O R D IRECT IONAL COUPLER ( 6 d B ) C A L I B R A T E D A T T E N U A T O R D I R E C T I O N A L C O U P L E R (20 dB) 6 4 m m W/G T 0 8 r n m W / G T A P E R 7 A T T E N U A T O R 8 F R E Q U E N C Y M E T E R 9 R E F E R E N C E M I X E R F i g . 2.6 Block diagram of transmitter apparatus. b o l c i d s , one o f a l um inum, t he o t h e r o f f i b e r g l a s s w i t h a c o n d u c t i v e c o a t - i n g . O r i g i n a l l y m a n u f a c t u r e d f o r o p e r a t i o n a t 35 GHz, m o d i f i c a t i o n s t o t h e f e e d we re made t o a l l o w use a t t w i c e t h i s f r e q u e n c y . The o r i g i n a l w a v e - g u i d e (7 .11 x 3.56 mm) was l e f t i n t a c t e x c e p t f o r t h e l a s t 2 cm. w h i c h was r e p l a c e d by a t a p e r t o 3.8 mm x 1.9 mm w a v e g u i d e t h u s p e r m i t t i n g o n l y t h e TE^g mode t o e x c i t e t h e a p e r t u r e . P o l a r i z a t i o n was h o r i z o n t a l . I t was d e s i r a b l e t o o p e r a t e t h e a n t e n n a s a t b o t h 35 GHz a n d 75 GHz. T h i s w o u l d a l l o w a n t e n n a a l i g n m e n t a t 35 GHz whe re h i g h e r s e n s i t i v - i t y i s a v a i l a b l e as w e l l as s y s t e m o p e r a t i o n d u r i n g r a i n a t '35 GHz. F o r t h i s p u r p o s e , t a p e r e d t e f l o n p l u g s , mach i ned t o f i t t h e a p e r t u r e and a b o u t 2 cm l o n g , w e r e i n s e r t e d i n t h e f e e d t o expand i t s e l e c t r i c a l s i z e a n d . a l l o w r a d i a t i o n . These i n s e r t s w e r e b r oadband and w e l l m a t c h e d t o t h e w a v e g u i d e . I t was a l s o o b s e r v e d t h a t o p e r a t i o n a t 75 GHz was n o t i m p a i r e d by t h e p l u g s ( t hough i t was u s u a l t o o p e r a t e w i t h o u t t h e m ) . Measu rement s on t h e A n t e n n a s : (a) M e c h a n i c a l : Measu rement s w e r e c a r r i e d o u t on t h e s u r f a c e o f t h e a l um inum d i s h . Cu r ve f i t t i n g o f t h e p o i n t s o b t a i n e d t o a p a r a b o l a showed t h e f o c a l l e n g t h t o be 305 mm. The d i a m e t e r was 1.05 m g i v i n g i t a r a t i o o f f o c a l l e n g t h t o d i a m e t e r , f / D , o f 0.29 and a s u b t e n d e d a n g l e o f 1 6 0 ° . (b) A p e r t u r e I l l u m i n a t i o n : W i t h a t a p e r e d a p e r t u r e i l l u m i n a t i o n , t h e maximum v a l u e o f g a i n i s u s u a l l y a c h i e v e d w i t h an edge i l l u m i n a t i o n o f - 1 2 dB r e l a t i v e t o t h e c e n t e r [ 5 8 ] , The p r i m a r y s o u r c e was an open ended w a v e g u i d e ( 3 . 8 x 1.9 mm). I t s r a d i a t i o n p a t t e r n was i n v e s t i g a t e d t o d e t e r m i n e t h e a c t u a l i l l - u m i n a t i o n . A t a f r e q u e n c y o f 73 GHz (2a = 1.83 X ) , b o t h t h e o r y and e x - p e r i m e n t i n d i c a t e d t h e 3 dB beamwidth t o be 74° i n t h e E - p l a n e and 5 9 ° i n 2 8 . t he H - p l a n e . A c c o u n t i n g f o r s p a c e a t t e n u a t i o n , t h e i l l u m i n a t e d a r e a ( i . e . w i t h i l l u m i n a t i o n > - 12 dB) was c a l c u l a t e d t o be about 50% o f t h e a c t u a l a r e a [ 5 8 ] . ( c ) R a d i a t i o n P a t t e r n : Nea r f i e l d measurements on t h e a n t e n n a s r e v e a l e d some a s s y m e t r y o f t h e a p e r t u r e f i e l d s . I t was n o t c o n v e n i e n t ( becau se o f " t h e l a r g e e x - t e n t o f t h e F r e s n e l zone) t o measure t h e f a r f i e l d p a t t e r n on a c o n v e n - • t i o n a l a n t e n n a p a t t e r n r a n g e . I n s t e a d , t h e an tenna s were i n s t a l l e d on t h e p a t h w i t h t h e r e f l e c t o r and w e r e a l i g n e d f o r opt imum r e c e p t i o n . Then one a n t e n n a was r o t a t e d p a s t t h e r e f l e c t o r w h i l e t he o t h e r r e m a i n e d f i x e d . The r e s u l t s o f t h e s e measurements a t 74 GHz a r e g i v e n i n T a b l e 2 . 1 . They i n d i c a t e [58] t h a t t h e g a i n s o f t h e t r a n s m i t t i n g and r e c e i v i n g a n t e n n a s a r e , r e s p e c t i v e l y , 49 .5 and 48 dB. C a l c u l a t e d G a i n : The b e s t p o s s i b l e g a i n t h a t c o u l d be o b t a i n e d f r o m s uch an a n t e n n a i s G = 10 l o g {0 .65 ^ y } = 53 dB 2 w h e r e : A = i l l u m i n a t e d a r e a (> - 12 dB) = 0 .38 m A = 4 .1 mm 2 . 3 . 2 R e f l e c t o r The p a s s i v e r e f l e c t o r u s e d i n t h i s m i c r owave l i n k i s made o f a 1 m x 1 m s h e e t o f 3/8 " ( 0 . 95 cm) t h i c k p l a t e g l a s s c o v e r e d w i t h " S c o t c h T i n t " , an a d h e s i v e p l a s t i c s h e e t l o a d e d w i t h f i n e c o n d u c t i n g p a r t i c l e s . The r e f l e c t i o n c o e f f i c i e n t o f a s u r f a c e t hu s c o n s t r u c t e d was f o u n d i n - d i s t i n g u i s h a b l e f r o m t h a t o f a s o l i d m e t a l l i c s t r u c t u r e a t 35 and 75 GHz. T h i s a r r a n g e m e n t p r o v i d e s a l a r g e , smooth and r e l a t i v e l y f l a t r e f l e c t i n g s u r f a c e a t r e a s o n a b l e c o s t . The r e f l e c t o r i s s u p p o r t e d by a s t r u c t u r e A n t e n n a 3-dB beamwidth [ d e g r e e s ] E - p l a n e H - p l a n e T r a n s m i t t i n g 0.55 0 .55 R e c e i v i n g 0.67 0 .62 T a b l e 2.1 Mea su red 3-dB beamwidths o f t r a n s m i t t i n g and r e c e i v i n g a n t e n n a s . Wavegu ide Type N o m i n a l I n n e r D i m e n s i o n s [mm] A t t e n u a t i o n [dB/m] t h e o r e t i c a l . mea su red X - b a n d 8 mm 4 mm 22.86 10 .16 7.11 3.56 3.76 1.88 0 .162 0 .546 1.34 0 . 4 1.0 1.8 T a b l e 2.2 T h e o r e t i c a l and measu red a t t e n u a t i o n a t 75 GHz o f 3 s i z e s o f r e c t a n g u l a r w a v e g u i d e . 30 . d e s i g n e d t o s t a n d w i n d s o f 100 km/hr w i t h o n l y s m a l l a n g u l a r d e f l e c t i o n s . R e f l e c t o r L o s s : The component o f p a t h l o s s due t o t h e r e f l e c t o r i s g i v e n by [ 5 8 ] : L o s s D = 20 l o g | r = 5.2 dB w h e r e : d = 880 m s e p a r a t i o n be tween an tenna s and r e f l e c t o r . A = 4 .1 mm s i g n a l w a v e l e n g t h 2 A = 1 m r e f l e c t o r a r e a r • - ' • • s u b j e c t t o t h e f o l l o w i n g c o n d i t i o n s (a) r e f l e c t o r and a n t e n n a s a r e i n each o t h e r ' s F r a u h h o f e r r e g i o n ? 2 d > - - f - = 490 m A (b) s u r f a c e must be f l a t w i t h i n ±A/16 (+0.25 mm). A l t h o u g h s t e p s were t a k e n t o e n s u r e f l a t n e s s , some d i s t o r t i o n o u t s i d e t h e s e l i m i t s may have o c c u r r e d due t o m o u n t i n g s t r e s s e s and t h e r - m a l e x p a n s i o n . The e x t e n t o f s u ch d i s t o r t i o n and i t s e f f e c t a r e n o t e a s i l y m e a s u r e d . 2 . 3 . 3 Wavegu ide B e c a u s e o f t h e r e l a t i v e l y h i g h a t t e n u a t i o n o f t h e s i n g l e moded r e c t a n g u l a r w a v e g u i d e i n t h e 70 t o 75 GHz r a n g e , t h e u s e o f l a r g e r , o v e r - , moded g u i d e s was i n v e s t i g a t e d . Two s i z e s , 8 mm and 3 cm (X -band ) w a v e - g u i d e s e c t i o n s , we re c o n s i d e r e d . Power i s c o u p l e d t o and f r o m t h e s e s e c - t i o n s w i t h g r a d u a l t a p e r s t o e n s u r e t h e t r a n s m i s s i o n i s m a i n l y b y T E ^ mode w i t h l i t t l e c o n v e r s i o n t o h i g h e r o r d e r modes. C h a r a c t e r i s t i c s o f the v a r i o u s w a v e g u i d e s and t he t a p e r s a r e g i v e n i n T a b l e s 2 .2 and 2 . 3 . The a t t e n u a t i o n s o f t h e above w a v e g u i d e s s u g g e s t e d t h a t t he X-band type s h o u l d be u sed where s i g n i f i c a n t l e n g t h s . o f g u i d e a r e r e - quired. However , measurements on X -band w a v e g u i d e s y s t e m s i n d i c a t e d that they had a h i g h l y o s c i l l a t o r y f r e q u e n c y r e s p o n s e . T y p i c a l v a r i a - 31. Taper Designation ' Ref lec t ion Coeff icient 4 mm to 8 mm - 25 dB 8 mm to X-band - 25 dB Table 2.3 .Measured r e f l e c t i o n coeff ic ients of waveguide tapers. Location of Waveguide Section Klys t ron to 4 - 8 mm taper to t ransmit t ing antenna i n t ransmit t ing antenna i n receiving antenna Length' Loss Type [m] [dB] 4 mm 0.4 0.7 8 mm 6.5 6.5 8 mm 0.7 0.7 8 mm 0.7 0.7 Waveguide Loss 8.6 Table 2.4 Calcu la t ion of system waveguiding losses • 32 . t i o n s i n t r a n s m i s s i o n c o e f f i c i e n t we re 6 dB f o r a change i n f r e q u e n c y o f 1 i n 10"*. As t h e f r e q u e n c y d r i f t s e n c o u n t e r e d i n l o n g p e r i o d s were much more t h a n t h a t , s u ch a s y s t e m was u n a c c e p t a b l e . F u r t h e r measurements i n - d i c a t e d t h a t bends w e r e m a i n l y r e s p o n s i b l e f o r t h i s p e r f o r m a n c e . A s i m i l a r - i n v e s t i g a t i o n u s i n g . 8 mm w a v e g u i d e r e v e a l e d much more a c c e p t a b l e c h a r a c t e r i s t i c s : f r e q u e n c y r e s p o n s e f l a t t o w i t h i n m e a s u r e - ment u n c e r t a i n t i e s ( ± 0 . 4 dB) o v e r a w i d e r ange o f f r e q u e n c i e s . Based on t h i s overmoded 8 mm w a v e g u i d e was e x t e n s i v e l y u s e d . The w a v e g u i d e l o s s e s o f t h e v a r i o u s s e c t i o n s i n t h i s s y s t e m a r e g i v e n i n T a b l e 2 . 4 . . A l l w a v e g u i d e s we re p r e s s u r i z e d t o c o n t i n u a l l y remove m o i s t u r e w h i c h m i g h t l e a k i n t h r o u g h j o i n t s o r f o r m b y c o n d e n s a t i o n . The c o n t i n u o u s f l o w o f a i r a l s o e n s u r e d t h a t , d u r i n g r a i n , d r o p s o f w a t e r w o u l d n o t a c - c u m u l a t e on t h e a n t e n n a f e e d s . 2 . 3 . 4 R e c e i v e r and A s s o c i a t e d Measurement U n i t s The r e c e i v e r u s e d i n t h i s p r o p a g a t i o n e x p e r i m e n t i s a p h a s e - l o c k e d , s u p e r h e t e r o d y n e S c i e n t i f i c A t l a n t a M o d e l 1 7 5 1 . T h i s d e s i g n i s i n t e n d e d p r i m a r i l y f o r a n t e n n a wo rk b u t f u n c t i o n s w e l l i n a d i v e r s e r a n g e o f a p p l i c a t i o n s . I n t h i s work two o f i t s t h r e e c h a n n e l s a r e u s e d : - 1. r e f e r e n c e c h a n n e l - p h a s e - l o c k e d t o t h e s o u r c e o s c i l l a t o r 2 . s i g n a l . c h a n n e l - m o n i t o r s t h e r e c e i v e d s i g n a l A s s o c i a t e d w i t h each c h a n n e l i s an e x t e r n a l h a r m o n i c m i x e r pumped by a common S -band (2 t o 4 GHz) l o c a l o s c i l l a t o r (LO) i n t he r e - c e i v e r . The same c a b l e t h a t c a r r i e s t h e l o c a l o s c i l l a t o r t o e a c h m i x e r s e r v e s t o r e t u r n t h e i n t e r m e d i a t e f r e q u e n c y ( I F ) t o r e c e i v e r . W i t h t h e r e f e r e n c e c h a n n e l p h a s e - l o c k e d t o t he t r a n s m i t t e d f r e q u e n c y ( R F ) , t he LO f r e q u e n c y a u t o m a t i c a l l y a d j u s t s t o m a i n t a i n t h e I F a t 45 MHz. I n s i d e the r e c e i v e r t h i s 45 MHz I F i s d o n w c o n v e r t e d a g a i n t o g i v e a s t a n d a r d . 33 . 1 KHz o u t p u t whose a m p l i t u d e and pha se r e l a t i v e t o t h e r e f e r e n c e c h a n n e l may be e a s i l y m e a s u r e d . The r e c e i v e r has a dynamic r ange o f 60 dB and ± 0 . 2 5 dB l i n e a r i - t y . The s e n s i t i v i t y t o I F i s - 1 25 dBm o r b e t t e r ( t h e s e n s i t i v i t y t o RF i s c o n s i d e r a b l y l e s s , d e p e n d i n g on t h e c o n v e r s i o n l o s s i n t h e m i x e r u s e d ) . A v a i l a b l e l o c a l o s c i l l a t o r d r i v e i s r a t e d a t +24 dBm p e r c h a n n e l ( b u t i s a c t u a l l y o n l y +17 dBm). T h r e e a d d i t i o n a l u n i t s we re u sed t o c o n v e r t r e c e i v e d a m p l i t u d e , phase and f r e q u e n c y t o a m a c h i n e - r e a d a b l e f o r m . The se u n i t s a r e l i s t e d b e l o w : A m p l i t u d e : The a m p l i t u d e o f t h e r e c e i v e d s i g n a l , i n t h e 1 KHz I F f o r m , was measu red b y a S c i e n t i f i c A t l a n t a M o d e l 1832 . An a v e r a g i n g t i m e o f 1 s e c - ond and a r e s o l u t i o n o f 0 .1 dB w e r e s e l e c t e d f o r t h i s s y s t e m . A c c u r a c y i s b e t t e r t h a n 0 .2 dB o v e r a 60 dB r a n g e . Use o v e r e x t e n d e d p e r i o d s i n - d i c a t e d t h a t t h i s measurement u n i t had e x c e l l e n t s t a b i l i t y . P h a s e : I t i s a n t i c i p a t e d t h a t f u t u r e work w i l l be c o n c e r n e d w i t h m e a s u r i n g t h e r e l a t i v e phase a n g l e o f t h e r e c e i v e d and t r a n s m i t t e d s i g - n a l s . When o p e r a t i n g w i t h t h e S/A 1751 R e c e i v e r t h i s w o u l d u s u a l l y be measu red by a S/A m o d a l 1822 D i g i t a l Pha se D i s p l a y . I t a c c e p t s a d i g i t a l a n a l o g o f pha se f r o m t h e r e c e i v e r and d i s p l a y s a r e s u l t a v e r a g e d o v e r a s e l e c t e d number o f c y c l e s . F o r l a b o r a t o r y t e s t s t h i s w o r k s w e l l b u t t h e path l e n g t h and r e s i d u a l FM i n h i b i t t h e i n s t r u m e n t ' s o p e r a t i o n . I t s h o u l d , h o w e v e r , be a s i m p l e t a s k t o b u i l d an a d e q u a t e pha se measurement u n i t with lower r e s o l u t i o n . 3 4 ; F r e q u e n c y : The f r e q u e n c y o f t he t r a n s m i t t e d s i g n a l i s mea su r ed i n d i r e c t l y by m o n i t o r i n g the l o c a l o s c i l l a t o r f r e q u e n c y . S i n c e t h e h a r m o n i c numbe r , t h e I F f r e q u e n c y and w h e t h e r m i x i n g i s u p p e r o r l o w e r s i n g l e - s i d e b a n d are known, t h e RF s i g n a l f r e q u e n c y may be c a l c u l a t e d . Measu rement i s made w i t h a 0 t o 18 GHz E I P A u t o h e t C o u n t e r M o d e l 351C w i t h a s e l e c t e d r e s o l - u t i o n o f 1 KHz . . 2 . 3 . 5 M i x e r s H a r m o n i c m i x e r s pumped by a 2 t o 4 GHz l o c a l o s c i l l a t o r d o w n - c o n v e r t t h e 74 GHz s i g n a l s t o 45 MHz I F s i g n a l s . I n t h i s a p p l i c a t i o n two m i x e r s a r e r e q u i r e d , one a t t h e r e c e i v i n g a n t e n n a and t h e o t h e r a t t h e s o u r c e . M i x e r s must o p e r a t e u n d e r t h e c o n s t r a i n t o f a v a i l a b l e l o c a l o s c i l l a t o r p o w e r , t h e b e s t m i x e r b e i n g t h e one w i t h t h e l o w e s t c o n v e r s i o n l o s s ( f r o m RF t o I F ) . T h r e e m i x e r s , c o m p a t i b l e w i t h t h e c u r r e n t s y s t e m , w e r e e v a l u a t e d ; t h e y w e r e : 1) S t a n d a r d L a b o r a t o r y D e t e c t o r (uLAB M206C o r e q u i v a l e n t ) : A s i n g l e 1N53 c r y s t a l i n a p r e s s u r e m o u n t i n g on t h e w a v e g u i d e w i t h a BNC c o n n e c t o r t h r o u g h w h i c h LO and I F a r e c o u p l e d . 2) S/A M o d e l 13A/50: R i g i d c r y s t a l mount o f 1N53C d i o d e . I F and LO a r e c o u p l e d t h r o u g h a t y p e - N c o n n e c t o r w i t h m a t c h i n g o f IF t o t h e c a b l e p r o v i d e d by a S/A M o d e l 1 7 6 7 - 4 5 . 3) S/A M o d e l 1 7 - 5 0 - 4 5 : C r o s s - w a v e g u i d e m i x e r w i t h a r i g i d mount f o r a IN53C d i o d e . I t i s u s ed w i t h t h e S/A M o d e l 1772 L o c a l - O s c i l l a t o r F r e q u e n c y M u l t i p l i e r w h i c h t r i p l e s t h e l o c a l o s c i l l a t o r . T h i s X - b a n d s i g n a l i s u s ed t o pump, t h e c r o s s - w a v e g u i d e m i x e r . A l l o f the m i x e r s a r e p r o v i d e d w i t h s t u b t u n e r s f o r m a t c h i n g . The f i r s t m i x e r t y p e was f o u n d u n s u i t a b l e f o r u se a t t h e r e - 3 5 . c e i v i n g a n t e n n a due t o i t s p o o r s e n s i t i v i t y and m e c h a n i c a l i n s t a b i l i t y . I t i s a d e q u a t e , howeve r , t o m o n i t o r t h e s o u r c e becau se h i g h l e v e l s o f o s c i l l a t o r and RF power a r e a v a i l a b l e . The s e cond t y p e o f m i x e r i s u sed w i t h a 1N53C d i o d e w h i c h p r o - v i d e s i m p r o v e d s e n s i t i v i t y o v e r 1N53 d i o d e s . By d i o d e s e l e c t i o n , c a r e f u l t u n i n g and opt imum l o c a l o s c i l l a t o r d r i v e a s e n s i t i v i t y o f - - 8 1 dBm o r b e t t e r ha s been, o b t a i n e d r e p e a t e d l y . T h i s c o r r e s p o n d s t o a c o n v e r s i o n l o s s o f 45 d3 a n d may be p a r t l y a c c o u n t e d f o r the h i g h h a r m o n i c numbers emp loyed i n t h e down-conver s ion [21 o r 2 2 ] . ( C u r r e n t a t t h e n t h h a r m o n i c 2 f l o w i n g i n a d i o d e d e c r e a s e s as 1/n i f p a r a s i t i c s a r e n e g l e c t e d [ 5 7 ] ) . By r e d u c t i o n o f t h e h a r m o n i c m i x i n g number s u b s t a n t i a l i m p r o v e - ment may be a c h i e v e d . The t h i r d m i x e r t y p e does j u s t t h i s . I t t r i p l e s t h e l o c a l o s c i l l a t o r i n a b a l a n c e d f r e q u e n c y m u l t i p l i e r and m i x e s t h i s X - b a n d s i g n a l w i t h t h e RF ( a h a r m o n i c number o f 7 ) . W i t h a 50 mwatt (+17 dBm) l o c a l o s c i l l a t o r d r i v e , i t g i v e s a s e n s i t i v i t y o f - 9 8 dB, 17 dB improvement o v e r t h e M o d e l 13 m i x e r . I n t h i s a p p l i c a t i o n , t h e r e a r e 42 m o f RG - 8 c o a x i a l c a b l e ( s p i r a l d i e l e c t r i c , s e m i - r i g i d ) w i t h an a t t e n u a t i o n o f 11 .8 dB a t 4 .0 GHz c o n n e c t i n g t he r e c e i v e r t o t h e r e c e i v i n g a n t e n n a m i x e r . Under t h i s c o n d i t i o n o f l i m i t e d l o c a l o s c i l l a t o r power , t h e second m i x e r t y p e i s s u p e r i o r t o t h e t h i r d . D e t a i l e d measurements s how ing t h i s a r e g i v e n i n A p p e n d i x A. A t - p r e s e n t , t h e n , the S/A M o d e l 13A-50 m i x e r i s u sed a t t h e r e ce i v i n g a n t e n n a . (The t h i r d m i x e r c o u l d be u sed i f t he l o c a l o s c i l l a t o r power a t t h e r e c e i v i n g a n t e n n a we re b o o s t e d . T h i s may be done w i t h commer- c i a l l y a v a i l a b l e 2-4 GHz power a m p l i f i e r w i t h a g a i n o f 18 dB and a s a t - u r a t e d power o u t p u t o f +25 dBm,) . 36 . 2 .3 .6 M i l l i m e t r i c Wave S o u r c e A r e f l e x k l y s t r o n (VRE-2101B5 V a r i a n A s s o c i a t e s o f Canada) i s u sed as t h e mm - wave s o u r c e . I t has a power o u t p u t o f 500 mwat t s and a 1.5 % t u n i n g r ange abou t i t s c e n t e r f r e q u e n c y o f 73 .5 GHz. FM n o i s e l e v e l s a r e l ow s o , c o n s e q u e n t l y , r e c e i v e r p h a s e - l o c k i s u s u a l l y s t a b l e . Th d i s a d v a n t a g e s o f t h i s s o u r c e a r e t h e h i g h o p e r a t i n g v o l t a g e s r e q u i r e d (2500 v o l t s DC) and t he r e l a t i v e l y s h o r t t u b e l i f e t i m e ( g u a r a n t e e d o p e r - a t i o n i s 500 h o u r s ) . To overcome some o f t h e s e p r o b l e m s an a t t e m p t was made t o u s e a s o l i d s t a t e mm-wave s o u r c e . A Hughes M o d e l 44051 H IMPATT d i o d e o s c i l l a - t o r was a v a i l a b l e w i t h a r a t e d power o u t p u t o f 50 mwat t s a t 70 .25 GHz. I t s l ow power r e q u i r e m e n t makes i t f e a s i b l e t o mount t h e s o u r c e d i r e c t l y t o t h e t r a n s m i t t i n g a n t e n n a w i t h c o n s i d e r a b l e s a v i n g s i n w a v e g u i d e l o s s e s Howeve r , t h e FM n o i s e l e v e l s i n t h e mm-wave o u t p u t w e r e h i g h enough t h a t r e c e i v e r l o c k was u n a t t a i n a b l e m a k i n g t h i s s o u r c e u s e l e s s i n t h e p r e s e n t s y s t e m . 37 . 2.4 D i s c u s s i o n The r e c e i v e d s i g n a l i n t he mm-wave l i n k was measured t o be - 41 dBm, 40 dB above t h e r e c e i v e r n o i s e l e v e l . T h i s i s 22 dB b e l o w the c a l - c u l a t e d r e c e i v e d s i g n a l l e v e l . The d i f f e r e n c e be tween t h e c a l c u l a t e d and measu red s y s t e m p e r f o r m a n c e ha s been o n l y p a r t i a l l y a c c o u n t e d f o r : 1) P h a s e M o d u l a t i o n : B e c a u s e t he r e c e i v e r i s pha se l o c k e d t o the RF s o u r c e , f r e q u e n c y changes o f the s o u r c e appea r as pha se changes i n t he r e c e i v i n g c h a n n e l I F s i g n a l . The magn i t ude o f t h e s e pha se changes i s p r o p o r t i o n a l t o t h e f r e - quency change and t h e p a t h l e n g t h . Measurements have shown t h a t t he phase m o d u l a t i o n r e s u l t s m o s t l y f r o m 60 Hz FM m o d u l a t i o n o f t he k l y s t r o n ( c a u s e d by power s u p p l y r i p p l e and by i n t e r f e r e n c e ) . Becau se o f t h e n a r - row b a n d f i l t e r s u s ed i n t he a m p l i t u d e measurement , phase m o d u l a t i o n r e - duce s t h e a p p a r e n t r e c e i v e d s i g n a l l e v e l . T h i s i s t h o u g h t t o be a b o u t 3 dB w i t h t h e p r e s e n t e q u i p m e n t . 2) R e f l e c t o r : The r e f l e c t o r " l o s s " o f 5.2 dB was c a l c u l a t e d a s s um ing a p e r - f e c t l y f l a t r e f l e c t i n g s u r f a c e . I f i t was d i s t o r t e d , t h e l o s s w o u l d , i n g e n e r a l , be h i g h e r . F o r e x a m p l e , c o n s i d e r t h e s u r f a c e d i s t o r t e d s p h e r i c a l l y s u c h t h a t t h e c e n t e r o f t h e r e f l e c t o r p r o t r u d e s 2 mm f r o m 2 i t s f o r m e r p o s i t i o n . T h i s w o u l d r e d u c e i t s e q u i v a l e n t a r e a t o 0.125 m [58] and i n c r e a s e r e f l e c t o r l o s s .by 18 dB. The a c t u a l e x t e n t o f r e f l e c - t o r d i s t o r t i o n i s unknown b u t i t i s a p p a r e n t t h a t l o s s e s due t o d i s t o r - t i o n c o u l d be h i g h . 3 8 . 2.5 Summary A s h o r t r a d a r - t y p e mm-wave l i n k has been e s t a b l i s h e d . I t i s s ummar i zed b e l o w : F r e q u e n c y (GHz) 74. P a t h l e n g t h (km) 1. 8 F r e e s p a c e l o s s (dB) 128 . 5 Gaseous A b s o r p t i o n (dB) 1. 2 R e f l e c t o r l o s s (dB) 5. 2 Wavegu ide l o s s e s (dB) 8. 6 A n t e n n a g a i n s ( d B ) : t r a n s m i t t i n g 4 9 . 5 r e c e i v i n g 48 . O t h e r l o s s e s ( d B ) * 2 2 . S o u r c e power o u t p u t (dBm) +27. R e c e i v e r s e n s i t i v i t y (dBm) - 8 1 . Fade M a r g i n (dB) 4 0 . * See S e c t i o n 2.4 39. CHAPTER I I I METEOROLOGICAL MEASUREMENT SYSTEM 3.1 Measurement o f R a i n R a t e 3 .1 .1 D e s c r i p t i o n o f R a i n Gauges The r a i n gauges u s e d i n t h i s t h e s i s a r e i n t e n d e d t o measure p o i n t r a i n r a t e s up t o 100 mm/hr. A c c u r a t e o p e r a t i o n above t h i s r a t e i s n o t c o n - s i d e r e d i m p o r t a n t b e c a u s e o f t h e l o w p r o b a b i l i t y o f s u ch e v e n t s i n t h i s a r e a . R a i n gauges o f t h e t i p p i n g b u c k e t v a r i e t y were s p e c i a l l y d e s i g n e d f o r t h i s p u r p o s e . 2 i n e s e . r a m gauges have a c o l l e c t i n g a r e a o f 920 cm and a n o m i n - a l t i p s i z e o f 4 .6 grams so t h a t a t i p o c c u r s a f t e r each 1/20 mm o f r a i n . To a l l o w e l e c t r i c a l s e n s i n g o f w h i c h way t he b u c k e t i s t i p p e d , a pe rmanen t magnet i s f a s t e n e d t o t he b u c k e t i n c l o s e p r o x i m i t y t o a g l a s s - e n c a p s u l a - t e d d r y r e e d s w i t c h w h i c h i s mounted on t h e r a i n gauge c h a s s i s . I n t h e c o n s t r u c t i o n o f t h e s e r a i n g auge s , c o r r o s i o n r e s i s t a n t m a t e r i a l s we re u sed as n e c e s s a r y t o a c h i e v e l ow m a i n t e n a n c e r e q u i r e m e n t s and s t a b l e l o n g - t e r m o p e r a t i o n . F u r t h e r d e t a i l s a r e shown i n F i g s . 3 . 1 , and 3 . 2 . 3 .1 .2 R a i n Gauge Ne two r k F i v e r a i n gauges o f t h e t y p e d e s c r i b e d i n S e c t i o n 3.2.1 we re i n s t a l l e d on r o o f t o p s a l o n g t he p a t h a t r o u g h l y e q u a l s p a c i n g s o f 220 m. The d e t a i l e d p o s i t i o n s a r e g i v e n i n F i g s . 2.1 and 2 .2 . I t i s n o t e d t h a t t he r a i n gauges a r e l o c a t e d a t v a r i o u s h e i g h t s be tween 1 and 35 m e t e r s b e l o w t h e m i c r o w a v e beam. C o n n e c t i o n o f each r a i n gauge i s made t o the c e n t r a l measurement s t a t i o n ( a t t he t r a n s m i t t e r ) by d e d i c a t e d h a l f - d u p l e x t e l e p h o n e l i n e s , one l i n e p e r r a i n gauge. T h e r e , cu s tom ha rdwa re b i a s e s each t e l e p h o n e l i n e , d e t e c t s the p r e s e n c e o r ab s ence o f l o o p c u r r e n t , d i s p l a y s t h e s t a t e o f t h e Fig . 3.1 A tipping bucket rain gauge with the side panels removed. F i g . 3.2 A tipping bucket rain gauge as insta l led on a roof. 41. rain gauges and provides a machine-readable output. Details of this unit are given in Appendix B. 3.2 Other Measurement Units . 1 Although the excess path attenuation on a short, mi l l imetr ic- wave l ink i s thought to be pr inc ipal ly due to instantaneous rain rate along the path, other meteorological variables such as wind, temperature, 'humidity, drop-size distr ibut ion and gradient of refractive index may have some effect. Instrumentation has been instal led to allow measure- ment of temperature and wind veloci ty . (a) Temperature: Two temperature transducers, placed out-of-doors i n a Stenvenson's screen near the antennas, serve to measure ambient temperature. Their design i s based on the National Semiconductor LX500 integrated c ircui t which gives an analog output of 0.1 v o l t / ° C . (b) Wind Velocity: A propeller-type anemometer has been assembled. The transdu- cers used are dc generators with l inear voltage-speed characteristics. . Two transducers are mounted on a platform free to face into the wind, one horizontally and the other at 45° from the v e r t i c a l . A synchronous motor with i t s rotor geared to the platform is used to sense wind direct ion. Further details are given i n Appendix C. The anemometer developed here allowed measurement of horizontal and ver t i ca l wind speeds and wind d i - rection. At present, however, the unit is positioned too close to .the roof and outside wall of the building for the measurements to be con- sidered accurate. 3.3 Discussion Point ra in rate, as measured by a tipping-bucket ra in gauge, i s 4 2 . s u b j e c t t o a v a r i a b l e i n t e g r a t i o n t i m e d i r e c t l y p r o p o r t i o n a l t o t i p s i z e and i n v e r s e l y p r o p o r t i o n a l t o r a i n r a t e . The o f t e n - u s e d 0 .25 mm/t i p r a i n gauge [ 37 ,39 ] has an i n t e g r a t i o n t i m e o f 18 s e c . a t 50 mm/hr. T h i s i s t h o u g h t t o be r a t h e r l o n g , m o t i v a t i n g t he s e l e c t i o n o f a 0 .05 mm t i p s i z e i n t he r a i n gauge d e s c r i b e d i n S e c t i o n 3 . 2 . 1 , w h i c h ha s an i n t e g r a t i o n t i m e o f 3.6 s e c . a t 50 mm/hr. '' I t i s n o t e d t h a t v i r t u a l l y a l l s t u d i e s i n t h e l a s t t e n y e a r s u s ed c a p a c i t a t i v e r a t h e r t h a n t i p p i n g - b u c k e t r a i n g a u g e s . C a p a c i t a t i v e r a i n gauges p o t e n t i a l l y o f f e r an a v e r a g i n g t i m e i n d e p e n d e n t o f r a i n r a t e and as s m a l l as 1 s e c o n d . I n p r a c t i c e , h o w e v e r , t h e y s u f f e r f r o m c a l i - b r a t i o n d r i f . t s and g i v e e r r a t i c r e s u l t s a t l ow r a i n r a t e s [ 2 8 ] . Two c a p - a c i t a t i v e gauges w e r e d e v e l o p e d h e r e and l a t e r abandoned b e c a u s e o f t h e i r p o o r p e r f o r m a n c e a t l ow r a t e s . T h i s b e h a v i o r was p a r t i c u l a r l y u n s u i t a b l e f o r t h e p r e s e n t wo r k s i n c e most r a i n f a l l i s l i g h t , mean i ng t h a t a c c u r a t e r e s u l t s w o u l d be a v a i l a b l e o n l y a s m a l l p a r t o f t h e t i m e i t was r a i n i n g . I n c o n t r a s t , t h e t i p p i n g b u c k e t r a i n gauge u sed i n t h i s w o r k i s r e l i a b l e and a c c u r a t e ( w i t h i n 5%) f o r a l l r a i n r a t e s be tween 0 and 100 mm/hr. The s p a c i n g o f 220 m e t e r s be tween r a i n gauges may b e compared w i t h s p a c i n g s i n p r e v i o u s s t u d i e s : 3300 m [ 3 7 , 4 6 ] , 1300 m [ 2 8 ] , 240 m [39] and a b o u t 40 m [ 4 7 , 2 6 ] , C e r t a i n l y , h i g h r a i n gauge d e n s i t i e s aire d e s i r a b l e s i n c e t h i s a l l o w s f o r a c c u r a t e measurement o f t h e s p a t i a l v a r i - a t i o n o f r a i n r a t e . I t i s t h o u g h t t h a t t h e s p a c i n g u s e d i n t h i s w o r k p r o v i d e s a r e a s o n a b l e compromise be tween a c c u r a c y and e f f i c i e n c y . The d r op s i z e d i s t r i b u t i o n o f r a i n f a l l c o u l d a l s o be an i m p o r t - a n t p a r a m e t e r . I t i s u s u a l l y r e p o r t e d as a h i s t o g r a m o f d i s t r i b u t i o n by vo lume o f r a i n i n t o v a r i o u s d r op s i z e c l a s s e s . The measurement o f d r o p size s p e c t r u m has n o t so f a r been i m p l e m e n t e d i n t h e s y s t e m , h o w e v e r . 43. CHAPTER TV DATA ACQUISITION AND DATA BASE FORMATION 4.1 Introduction To be able to carry out comprehensive s t a t i s t i c a l analyses of accumulated weather and propagation data, i t i s desirable to have the data in a form compatible with a general purpose computer. This chapter is concerned with the col lect ion and transfer of observations from the sensors of Chapters 2 and 3 into a machine readable data base. The techniques required to do the above must, at some stage, record the data and d ig i t i ze i t . The sequence of these two operations is different. for different systems. Four data-logging systems in common usage were considered: 1) Recording on s tr ip chart followed by manual d ig i t i za t ion 2) Analog recording on magnetic tape and later d ig i t i za t ion under software control 3) Recording on paper tape by a hardwired control ler 4) Real time d ig i t i zat ion and recording on an intermediate medium under software control . For this work, the last method was selected. It i s an at tract tive technique in view of the present ava i lab i l i t y of powerful integrated c ircui t s and minicomputers with adequate support. The v i a b i l i t y of this method can be readily seen in this thesis. A block diagram of the sys- tem as implemented is shown in F i g . 4.1. Three components of the data logging system which may be immed- iately identi f ied are: 1) a minicomputer 2) an interface between a multitude of sensors and the mini - computer. MICROWAVE 1 1 WEATHER MEASUREMENT | MEASUREMENT SUB —SYSTEM | SU B. - SYSTE M 1 1 HARDWARE INTERFACE DEDICATED MINICOMPUTER AND SOFTWARE _ > U L _ _ _ TEMPORARY STORAGE MEDIUM: A POOL OF MAGNETIC TAPES A GENERAL PURPOSE COMPUTING FACILITY 1 I r PERMANENT DATA BASE: MAGNETIC TAPE (APPEND 8> READ ONLY) 4.1 D a t a a c q u i s i t i o n s y s t e m b l o c k diagram. 4 5 . 3) a s t o r a g e medium on w h i c h t o r e c o r d d a t a . The i n t e r f a c e must be c o m p a t i b l e w i t h t h e m i n i c o m p u t e r f a m i l y s e l e c t e d and must be a b l e t o h a n d l e t he r e q u i r e d d a t a r a t e s . O t h e r t h a n t h i s , i t may be d e s i g n e d w i t h l i t t l e k n o w l e d g e o f t he r e s t o f t h e s y s t e m (a s o u t l i n e d i n S e c t i o n 4 . 2 ) . On t h e o t h e r h a n d , s e l e c t i o n o f an i n t e r - m e d i a t e s t o r a g e medium on w h i c h d a t a a r e h e l d b e f o r e t r a n s f e r • t o t h e a n a l y s i s compute r r e q u i r e s s u b s t a n t i a l k now ledge o f t h e d a t a l o g g i n g p r o b - l e m and depends on t he s t r a t e g y by w h i c h d a t a i s r e c o r d e d . 4 . 1 . 1 P o s s i b l e R e c o r d i n g S t r a t e g i e s By t he u se o f r e c o r d i n g s t r a t e g i e s o f v a r y i n g l e v e l s o f s o p h i s - t i c a t i o n , t h e same i n f o r m a t i o n may be s t o r e d a t d i f f e r i n g d e g r e e s o f c om- p a c t n e s s . The f o u r s t r a t e g i e s c o n s i d e r e d h e r e a r e g i v e n b e l o w , i n o r d e r o f i n c r e a s i n g e f f i c i e n c y : 1) To r e c o r d v a l u e s f o r a l l v a r i a b l e s a t a s i n g l e f i x e d r a t e 2) To r e c o r d v a l u e s f o r a l l v a r i a b l e s a t a s p e c i a l r a t e f o r e a ch v a r i a b l e 3) To r e c o r d by s t r a t e g y (1) o r (2) b u t o n l y when t h e o u t p u t meets some p r e d e t e r m i n e d c r i t e r i a o f b e i n g " i n t e r e s t i n g " 4) To r e c o r d t he o u t p u t o f a s e n s o r o n l y when i t ha s c h a n g e d a p r e d e t e r m i n e d amount f o r m t h e p r e v i o u s r e c o r d e d v a l u e . Method (4) r e c o g n i z e s t h e f a c t t h a t many o f t h e s a m p l e d s i g n a l s a r e u s u a l l y s l o w l y v a r y i n g w h i l e p r o v i d i n g a d e q u a t e s a m p l i n g when t h e y do v a r y q u i c k l y . I t i s p o t e n t i a l l y t h e mc s t e f f i c i e n t o f t h e f o u r s t r a t e g i e s b u r o f f e r s no s p e c i a l a d v a n t a g e f o r c o n t i n u a l l y f l u c t u a t i n g s i g n a l s ( s u c h as wind s p e e d ) . Method (1) i s i n e f f i c i e n t i n i t s u t i l i z a t i o n o f s t o r a g e s p a c e s i n c e the o u t p u t o f e a ch s e n s o r i s r e c o r d e d a t t h e " r a t e a p p r o p r i a t e t c t he f a s t e s t - v a r y i n g one . Howeve r , i t has t h e a d v a n t a g e o f s i m p l i c i t y , 46 . c o m p l e t e n e s s and o f r e q u i r i n g l i t t l e advance know ledge o f s i g n a l c h a r a c - t e r i s t i c s . Methods (2) and (3) a r e v a r i a t i o n s o f (1) a n d , . w h i l e more e f f i c i e n t , t h e y a r e a l s o more c o m p l e x . Method (3) c o u l d l e a d t o l o s s o f i m p o r t a n t i n f o r m a t i o n due t o u n i n f o r m e d d e f i n i t i o n o f what i s " i n t e r e s t i n g " , 4 , 1 . 2 S t o r a g e M e d i a The s t o r a g e m e d i a u s u a l l y a s s o c i a t e d w i t h m i n i c o m p u t e r s a r e : 1) p a p e r t a p e 2) m a g n e t i c t a p e 3) d i s k The d e c i s i o n as t o w h i c h t o u se depends upon t h e i n s t a n t a n e o u s r a t e a t w h i c h d a t a i s w r i t t e n , t h e med ium ' s c a p a c i t y and i t s r e l i a b i l i t y . T a b l e 4 .1 g i v e s a c o m p a r i s o n o f t h e above m e d i a on t h e s e p o i n t s . S t o r a g e Maximum C a p a c i t y R e l a t i v e Medium O u t p u t R a t e ^ R e l i a b i l i t y [ B y t e s / s e c ] [10 b y t e s ] P a p e r t a p e : ASR 33 10 0.13 V e r y Low P a p e r t a p e : h i g h speed punch 63.5 0.13 Low M a g n e t i c t a p e (800 BP I ) > 10 ,000 19 . H i g h D i s k ( s i n g l e p l a t t e r ) > 100,000 2.4 H i g h T a b l e 4 .1 A c o m p a r i s o n o f v a r i o u s i n t e r m e d i a t e b u l k s t o r a g e m e d i a . P a p e r t a p e i s i m m e d i a t e l y r u l e d o u t by i t s r e l a t i v e l y poo r r e l i - a b i l i t y and s m a l l c a p a c i t y ; f o r t h i s a p p l i c a t i o n , t he c a p a c i t y o f a s u i t - a b l e medium s h o u l d a t l e a s t a l l o w u n a t t e n d e d o p e r a t i o n o v e r n i g h t and p r e f e r a b l y o v e r a weekend . M a g n e t i c t a p e i s w e l l - s u i t e d on a l l c o u n t s . (One 2 4 0 0 ' m a g n e t i c t a p e w i l l h o l d 80 h o u r s r e c o r d i n g a t 64 b y t e s / s e c o n d . ) I t i s a l s o a s t a n d a r d medium f o r i n t e r c o m p u t e r i n f o r m a t i o n e xchange . 47 . The a p p l i c a t i o n o f d i s k s t o r a g e i s somewhat d i f f e r e n t . F o r a v a r i e t y o f r e a s o n s d i s k s t o r a g e c a n n o t be p h y s i c a l l y t r a n s p o r t e d b e t w e e n c o m p u t e r s . The u s u a l mode o f o p e r a t i o n on d i s k w o u l d t h e n be t o s t o r e d a t a on d i s k and p e r i o d i c a l l y dump them t o t h e a n a l y s i s computer v i a a d a t a l i n k . S c h e d u l e d downt ime on t h e IBM 370 i s l o n g enough t h a t o n l y d a i l y t r a n s m i s s i o n s a r e f e a s i b l e ( t h i s l i m i t s t h e a v e r a g e r e c o r d i n g r a t e t o I I b y t e s / s e c o n d ) . W i t h a s u i t a b l e r e c o r d i n g s t r a t e g y t h i s i s c e r t a i n l y f e a s i b l e and w o u l d o f f e r , i n t h e o r y , c o m p l e t e l y u n a t t e n d e d o p e r a t i o n . D i s k s t o r a g e i s , h o w e v e r , n o t u sed i n t h i s s y s t e m becau se t h e c a p a c i t y o f t he a v a i l a b l e d i s k i s r a t h e r s m a l l and b e c a u s e i t w o u l d r e q u i r e , s i m u l - t a n e o u s l y , t h e c o r r e c t o p e r a t i o n o f two c o m p u t e r s . The i n c r e a s e d comp lex - 1 i t y o f s u ch a s y s t e m was t h o u g h t t o be u n d e s i r a b l e a t t h i s t i m e . M a g n e t i c t a p e a p p e a r e d t o be t h e s t o r a g e medium most s u i t e d t o t h i s d a t a l o g g i n g a p p l i c a t i o n . The h i g h c a p a c i t y o f m a g n e t i c t a p e a l l o w - ed t he u s e o f r e c o r d i n g s t r a t e g y ( 1 ) , one samp le o f each o f 32 v a r i a b l e s e v e r y s e c o n d . Such a s t r a t e g y was e x p e d i e n t i n t h e d e v e l o p m e n t s t a g e s o f t h i s s y s t e m as i t r e q u i r e d l i t t l e advance know ledge o f s i g n a l c h a r a c - t e r i s t i c s and a f f o r d e d a maximum o f f l e x i b i l i t y . The p u r p o s e o f t h e d a t a a c q u i s i t i o n s y s t e m i s t o l o g d a t a on a r e a l time and c o n t i n u o u s b a s i s and t o e n t e r t h i s d a t a , s u i t a b l y e d i t e d and f o r m a t t e d , i n t o a pe rmanent d a t a b a s e a t a more p o w e r f u l c o m p u t i n g f a c i l i t y f o r l a t e r a n a l y s i s . I t . i s i n t e n d e d t h a t d a t a b a s e f o r m a t i o n be routine and r e l a t i v e l y a u t o m a t i c . I n t h e f o l l o w i n g s e c t i o n s , d e t a i l s o f t h e f l o w o f d a t a i n t o , a permanent data b a s e a r e g i v e n . S p e c i f i c a l l y t h e i n t e r f a c e a l l o w i n g m i n i - computer access t o t he m i c r o w a v e and w e a t h e r s e n s o r s , t h e m i n i c o m p u t e r - based data logging scheme and t h e p o s t p r o c e s s i n g o f d a t a on an IBM 370 are described. 4 8 . 4 .2 M i n i c o m p u t e r I n t e r f a c e The l o c a l a v a i l a b i l i t y o f m i n i c o m p u t i n g f a c i l i t i e s i n d i c a t e d t h a t an i n t e r f a c e s h o u l d be c o m p a t i b l e w i t h t h e Nova l i n e o f c o m p u t e r s . I n t e r f a c i n g t e c h n i q u e s a r e w e l l known [ 5 9 ] , a n d c o n s i d e r a b l e e x p e r i e n c e w i t h them e x i s t s w i t h i n t h e d e p a r t m e n t . T h i s i n t e r f a c e a l l o w s compute r i n t e r r o g a t i o n o f 5 measurement u n i t s : 2 d i g i t a l a m p l i t u d e d i s p l a y s , a phase d i s p l a y , a f r e q u e n c y m e t e r and a r a i n gauge m o n i t o r i n g u n i t . I t a l s o p e r m i t s r e a d i n g o f t h e t i m e o f day and t h e v o l t a g e l e v e l s on 16 a n a l o g i n p u t s ( m e t e o r o l o g i c a l s e n s o r s and r e c e i v e r p a r a m e t e r s ) . I n t e r n a l t o t h e i n t e r f a c e c i r c u i t r y , t h r e e s u b s y s t e m s can b e i d e n t i f i e d , e a ch w i t h i t s own d e v i c e number. These a r e : a 16 c h a n n e l A/D c o n v e r t e r , an 8 c h a n n e l x 16 l i n e d a t a s e l e c t o r and a r e a l t i m e c l o c k . The r e m a i n i n g u n i t s : t h e d i s p l a y p a n e l , 24 h o u r c l o c k and I/O bus t e r m - i n a t o r a r e a s s o c i a t e d w i t h t h e i n t e r f a c e as a w h o l e . A b l o c k d i a g r a m o f t h e s e u n i t s and a s s o c i a t e d i n t e r c o n n e c t i o n s i s g i v e n b y F i g . 4 . 2 . The A/D c o n v e r t e r s u b s y s t e m i s b u i l t a r o u n d an A n a l o g i c MP6912 1 6 - c h a n n e l 12 b i t D a t a A q u i s i t i o n modu l e . O v e r - v o l t a g e p r o t e c t i o n and s e l e c t a b l e f i l t e r i n g o f t h e 16 a n a l o g i n p u t s a r e p r o v i d e d by. a custom c i r c u i t b o a r d . Two o t h e r b o a r d s , t h e D e v i c e 56 i n t e r r u p t c a r d and t h e A/D c o n t r o l u n i t , a l l o w m i n i c o m p u t e r c o n t r o l o f c h a n n e l s e l e c t i o n and t h e s t a r t o f c o n v e r s i o n p roce s se s . . I n t e r r u p t s on D e v i c e 56 h a v e been d i s a b l e d f o r s o f t w a r e r e a s o n s ; h e n c e t h e e n d - o f - c o n v e r s i o n c o n d i t i o n must be s e n s e d by c h e c k i n g bu s y and done f l a g s . The c y c l e t i m e o f t h i s ' s u b s y s t e m i s a bou t 15 usee p e r c h a n n e l . The 5 measurements u n i t s l i s t e d above and t h e 24 h o u r c l o c k a r e a c c e s s e d by t he m i n i c o m p u t e r t h r o u g h a d i g i t a l m u l t i p l e x e r c o n t r o l l e d 49 . 4=> A / D CONTROL U N I T D E V . 5 6 IN T E R R UP] C A R D 16 CHANNEL A / D C O N V E R T E R ^ A / D P R O T E C T I O N A N D F I L T E R S i r i t - r D I S P L A Y P A N E L I 16 A N A L O G INPUTS D E V I C E 4 4 - 4 5 I N T E R R U F T C A R D ^—y R E A L T I M E C L O C K 2 4 HOUR C L O C K D I G I T A L M U L T I P L E X E R «£3- 16 B U F F E R C A R D DIGITAL MEASUREMENT UNITS — A 50 I/O B U S TERMINATOR C O M P U T E R F i g . 4.2 Block diagram of the minicomputer in te r face . 50 . by t he d e v i c e 45 i n t e r r u p t c a r d . The d i g i t a l m u l t i p l e x e r s e l e c t s one g roup o f 16 l i n e s . o u t o f 8 g roup s and p l a c e s i t on t h e d a t a bu s when s t r o b e d . Each o f t he measurement u n i t s and t h e c l o c k a r e a s s i g n e d one o r two m u l t i p l e x e r c h a n n e l s as r e q u i r e d ; t h e h a r d w a r e c o n n e c t i o n s f o r t h i s b e i n g made on t h e D i g i t a l B u f f e r c a r d . By s a m p l i n g a c h a n n e l , a d e l a y e d p u l s e i s g e n e r a t e d w h i c h i s u s ed by most measurement u n i t s t o r e s t a r t c o n v e r s i o n p r o c e s s e s . These p u l s e s keep measurements s y n c h r o n o u s w i t h t h e c o m p u t e r . D e v i c e 44 c o n t r o l s t he r e a l t i m e c l o c k w h i c h , when s t a r t e d , i n - t e r r u p t s t h e m i n i c o m p u t e r on a r e g u l a r b a s i s . The i n t e r r u p t r a t e i s s e t by t h e m i n i c o m p u t e r and may r ange f r o m 0 .0015 Hz t o 200 KHz. I n p a r t i c - u l a r , e x a c t v a l u e s o f 100 H z , 10 H z , 1 H z , 0 .1 Hz and 0.01 Hz a r e a v a i l - a b l e . These v a l u e s a r e " e x a c t " w i t h r e s p e c t t o t he 24 h o u r c l o c k as b o t h t h e 24 h o u r c l o c k and t he r e a l t i m e c l o c k a r e d e r i v e d f r o m t h e same s o u r c e , a 2 .4576 MHz c r y s t a l o s c i l l a t o r . The r e a l t i m e c l o c k i n i t i a t e s s a m p l i n g o f v a r i o u s i n t e r f a c e c h a n n e l s b y t h e m i n i c o m p u t e r s o f t w a r e . The p a r t i c u l a r i n s t r u c t i o n s equence s f o r i n t e r f a c e o p e r a t i o n .'j a r e g i v e n i n . A p p e n d i x D. D e t a i l e d c i r c u i t d i a g r a m s a r e a l s o c o n t a i n e d t h e r e . To s u m m a r i z e , t h e i n t e r f a c e d e s c r i b e d above a l l o w s r e a d i n g o f t h e m i c r o w a v e and w e a t h e r s e n s o r s d e s c r i b e d i n C h a p t e r s 2 and 3 b y t he m i n i c o m p u t e r , v i a an 8 c h a n n e l d a t a s e l e c t o r and a 16 c h a n n e l A/D c o n - v e r t e r . 4 .3 R e a l Time D a t a A c q u i s i t i o n and R e c o r d i n g 4 . 3 . 1 The C o m p u t i n g - F a c i l i t y The r e a l t i m e d a t a a c q u i s i t i o n s y s t e m i s d e s i g n e d t o o p e r a t e w i t h the Nova l i n e o f m i n i c o m p u t e r s . The minimum h a r d w a r e c o n f i g u r a t i o n under 5 1 . w h i c h t h e s o f t w a r e d e v e l o p e d h e r e w i l l o p e r a t e i n c l u d e s : 1) a Nova CPU w i t h 16 K words o f memory 2) a 9 t r a c k IBM c o m p a t i b l e m a g n e t i c t a p e u n i t and c o n t r o l l e r 3) a t e l e t y p e ( i n a d d i t i o n , h a r d w a r e m u l t i p l y / d i v i d e i s u sed a l t h o u g h t h e s o f t w a r e v e r - s i o n i s f a s t enough f o r t h i s a p p l i c a t i o n ) . T h i s f a c i l i t y w o u l d be r u n unde r a c o r e r e s i d e n t o p e r a t i n g s y s - tem; i n t h i s c a s e w i t h t h e R e a l T ime O p e r a t i n g S y s tem (RTOS) , a s o f t w a r e p a c k a g e a v a i l a b l e f r o m D a t a G e n e r a l Canada C o r p . A t p r e s e n t , h o w e v e r , d a t a a c q u i s i t i o n i s c a r r i e d o u t a t a more p o w e r f u l Nova 840 m i n i c o m p u t e r f a c i l i t y (32 K o f c o r e memory ) , w i t h a d i s k o p e r a t i n g s y s t e m (RDOS - Rev. 5 ) . W h i l e t h e s o f t w a r e w r i t t e n f o r RTOS o p e r a t i o n i s f u l l y c o m p a t i b l e w i t h t he d i s k o p e r a t i n g s y s t e m , a v e r s i o n was w r i t t e n e s p e c i a l l y f o r RDOS Rev . 5. I t makes p r o g r a m i n t e r - r u p t i o n s i m p l e and r e l a t i v e l y f o o l p r o o f ; t h i s i s a n e c e s s a r y f e a t u r e as the Nova 840 i s s h a r e d b y many u s e r s . 4 . 3 . 2 M u l t i t a s k P rog ramming The s o f t w a r e d e v e l o p e d h e r e u se s a m u l t i t a s k p r o g r a m e n v i r o n m e n t r a t h e r t h a n t h e more c o n v e n t i o n a l s i n g l e t a s k e n v i r o n m e n t . A m u l t i t a s k e n v i r o n m e n t i s one i n w h i c h more t h a n one t a s k compete s f o r CPU c o n t r o l . Ta s k s o p e r a t e a s y n c h r o n o u s l y , and i n r e a l t i m e , w i t h c o n t r o l b e i n g a l l o - c a t e d t o t he r e a d y t a s k o f h i g h e s t p r i o r i t y b y a s u p e r v i s o r y p r o g r a m , t h e Ta sk S c h e d u l e r . S y n c h r o n i z a t i o n be tween t a s k s i s m a i n t a i n e d by t r a n s - m i s s i o n and r e c e p t i o n o f messages by t a s k s . T h i s a l l o w s any t a s k t o go i n t o s u s p e n s i o n p e n d i n g t h e a r r i v a l o f f r e s h d a t a . A g e n e r a l t a s k s t r u c t u r e was a d o p t e d h e r e . The t a s k i s d i v i d e d into three p a r t s : i n i t i a t i o n , p r o c e s s l o o p and t e r m i n a t i o n . The i n i t i - 5 2 . a t i o n s e t s p o i n t e r s and c o u n t e r s t o i n i t i a l v a l u e s , a l l o c a t e s r e q u i r e d s y s t e m r e s o u r c e s and t h e n p a s s e s c o n t r o l t o t h e p r o c e s s l o o p . One p a s s t h r o u g h t h e " p r o c e s s loop 1 ' o c c u r s e a ch t i m e an u n p r o c e s s e d d a t a r e c o r d becomes a v a i l a b l e ; any t i m e no d a t a a r e a v a i l a b l e , t h e t a s k i s i n s u s - p e n s i o n . Upon o c c u r e n c e o f an end c o n d i t i o n , t h e t e r m i n a t i o n r o u t i n e i s e n t e r e d . T h i s r e l e a s e s p r e v i o u s l y a l l o c a t e d s y s t e m r e s o u r c e s a n d t h e n removes t h e t a s k f r o m t h e p r o g r am e n v i r o n m e n t . The above t a s k s t r u c t u r e r e d u c e s c o n n e c t i o n be tween t a s k s t o d a t a b u f f e r s and s i n g l e wo rd me s s a ge s . Such m o d u l a r i z a t i o n e a s e s s o f t w a r e m o d i f i c a t i o n and c l a r i f i e s o p e r a t i o n . 4 . 3 . 3 P r o g r a m O p e r a t i o n The d a t a a c q u i s i t i o n s o f t w a r e o p e r a t e s w i t h s i x c o r e r e s i d e n t t a s k s i n c o m p e t i t i o n f o r CPU c o n t r o l . Ta s k s communicate w i t h e a c h o t h e r t h r o u g h f i v e message a d d r e s s e s and o p e r a t e on d a t a h e l d i n two d a t a s t r u c t u r e s , a c i r c u l a r queue and an o u t p u t b u f f e r . B o t h d a t a s t r u c t u r e s a r e t w o - d i m e n s i o n a l a r r a y s i n d e x e d b y r e l a - t i v e t i m e ( o f d a t a s a m p l i n g ) and by a v a r i a b l e number. Thus e a c h d a t a s t r u c t u r e i s composed o f an i n t e g r a l number o f r e c o r d s . A r e c o r d , i f i t h o l d s a c t i v e d a t a , c o n t a i n s a l l d a t a a c q u i r e d i n an i n t e r v a l o f t i m e (one s e c o n d ) . The a s s i g n m e n t o f v a r i a b l e s t o r e c o r d e l e m e n t s i s d e t a i l e d i n T a b l e 4 . 2 . The c i r c u l a r queue [60] i s u s e d t o h o l d d a t a r e c o r d s d u r - i n g v a r i o u s s t a g e s o f p r o c e s s i n g . The d e f i n i t i o n o f t h e p o i n t e r s a s s o c i - a t e d w i t h t h e queue i s g i v e n i n F i g . 4 . 3 . The o u t p u t b u f f e r i s a l i n e a r a r r a y i n t o w h i c h p r o c e s s e d d a t a r e c o r d s a r e a s s e m b l e d b e f o r e b e i n g w r i t t e n o n t o m a g n e t i c t a p e . T h r e e t a s k s : INPUT, PROCESS, and OUTPUT a r e c e n t r a l t o t h e d a t a a c q u i s i t i o n and r e c o r d i n g , f u l f i l l i n g f u n c t i o n s a n a l o g o u s t o t h e i r names . INPUT samp le s v a r i o u s c h a n n e l s unde r s y n c h r o n i z a t i o n f r o m t h e i n t e r f a c e , 5 3 . WORD (Octal) .. 0 1 2 3 10 to 27 30 to 37 DESIGNATION Amplitude 1 [10~2 dB] Amplitude 2 [10~2 dB] Phase [10 degrees] Frequency, upper four d i g i t s [10^ Hz] 3 Frequency, lower four d i g i t s [10 Hz] Rain gauge monitor output 24 hour clock, "hours 24 hour c lock , minutes and seconds A/D channels 1 to 16 [5mv/bit] Rain rates on gauges 1 to 8, [mm/hr] x 182.2 Table 4.2 xhe 32 word record structure used i n the r e a l time data acqu i s i t i on system. PTA I L T A I L D A T A INPUT ^ — H E A A S INGLE RECORD P H E A D DATA O U T P U T D ' ' ' ig . 4.3 The c i r c u l a r queue and associated pointers, 54 . c o n v e r t s a l l i n p u t s t o 16 b i t 2 ' s complement f o r m a t and p l a c e s t h e r e s u l t i n t h e queue. PROCESS examines new r e c o r d s , computes r a i n r a t e s , i n s e r t s r e s u l t s i n t he queue and r e l e a s e s r e c o r d s f o r o u t p u t . OUTPUT a s s e m b l e s b l o c k s o f r e c o r d s i n t h e o u t p u t b u f f e r and w r i t e s them on t a p e as r e q u i r - e d . I t a l s o d i v i d e s t he o u t p u t i n t o f i l e s and p e r f o r m s a s s o c i a t e d b o o k - k e e p i n g a c t i v i t i e s . The r e m a i n i n g t h r e e t a s k s f i l l s e c o n d a r y r o l e s . START i n i t i a t e s p r og r am o p e r a t i o n i n an o r d e r e d manner and t e r m i n a t e s i t i n s i m i l a r f a s h - i o n when CONSOLE d e t e c t s t h e end c o n d i t i o n . MONITOR a l l o w s t h e o p e r a t o r t o c h e c k t h e o u t p u t b u f f e r t o a s c e r t a i n p r og r am and h a r d w a r e p e r f o r m a n c e . The above d e s c r i p t i o n o f e a ch t a s k t o g e t h e r w i t h F i g . 4.4.prov ide some i n s i g h t i n t o how t h e s o f t w a r e o p e r a t e s . The a c t u a l f l o w o f CPU c o n - t r o l i s i n d e t e r m i n a t e and d a t a d e p e n d e n t ; i n g e n e r a l , i t does n o t f o l l o w d i r e c t l y t h e same p a t h as message t r a n s m i s s i o n s . A l l t a s k s were d e s i g n e d so t h e y c o u l d o p e r a t e c o n s i d e r a b l y d e l a y e d w i t h r e s p e c t t o t a s k s i n f r o n t o f them i n t he p r o c e s s c h a i n . B e i n g a r e a l t i m e s y s t e m w i t h f i n i t e b u f f e r s i z e s , p r o g r am f a i l u r e w i l l o c c u r i f d e l a y s become l a r g e enough. The s o f t w a r e , h o w e v e r , c o n t a i n s enough f l e x i b i l i t y t h a t f a i l u r e by t h i s m e c h - a n i s m i s r a r e . No s u c h e v e n t s have o c c u r r e d a t t h e o u t p u t r a t e o f 1 r e c o r d / s e c o n d . A more d e t a i l e d e x p l a n a t i o n o f p r og r am o p e r a t i o n t o g e t h e r w i t h s o f t w a r e l i s t i n g s i s g i v e n i n A p p e n d i x E. A p p e n d i x E a l s o d e a l s w i t h o p e r a t i o n and backup o f the s o f t w a r e . 4 . 3 . 4 R a i n Gauge P r o c e s s i n g A d a t a word r e a d f r o m the r a i n gauge m o n i t o r i n g u n i t shows w h i c h r a i n g a u g e s , i f a n y , have t i p p e d i n t h e l a s t c l o c k c y c l e ; i t does n o t p e r se y i e l d t h e p o i n t r a i n r a t e a t each gauge. However , k now ing t h e 55. OPERAT ING SY STEM T A S K S C H E D U L E R E N T E R E X I T «s@g S T A R T PRIORITY = 0 - * H •• INITIATE EACH TASK. GO INTO SUSPENSION UNTIL. AN E N D MESSAGE IS R E C E I V E D K I L L E A C H T A S K . C O N S O L E P R I O R I T Y = 2 0 0 T R A N S M I T A M E S S A G E W H E N E N D CONDIT ION IS D E T E C T E D H A R D W A R E INTERPUT R.T..C. I N T E R U P T SERVICE ROUTINE 1) SEND MESSAGE 'TO I N P U T ' 2) DISMISS INTERRUPP / / I \ / I \ / i I N P U T PRIORITY = l S A M P L E VARIOUS S E N S O R S . F O R M A T T H E S E I N P U T S . P L A C E RESULTS IN THE QUEUE P R O C E S S PRI0RITY = 2 COMPUTE RAIN R A T E S L E A V E R E S U L T S IN THE QUEUE O U T P U T P R I 0 R I T Y = 3 T R A N S F E R RECORDS TO T H E O U T P U T B U F F E R : W R I T E ONTO M A G N E T I C T A P E . M O N I T O R PR IOR ITY = 4 A L L O W INSPECT ION OF D A T A IN OUTPUT B U F F E R . A block diagram of the data acqu i s i t i on software, showing the messages which connect various tasks (Dashed l i n e s represent message t ransfers) . 56. i n t e r v a l be tween s u c c e s s i v e t i p s on a gauge t he a v e r a g e r a i n r a t e i n t h a t i n t e r v a l may be compu ted ; i t i s i n v e r s e l y p r o p o r t i o n a l t o t h e i n t e r v a l l e n g t h . A t h i g h r a i n r a t e s (50 mm/hr) t i m e be tween t i p s , i s s h o r t ( 3 . 6 s e c f o r 1/20 mm t i p s i z e ) r e q u i r i n g t h a t gauges be s a m p l e d s u f f i c i e n t l y o f t e n t o a c c u r a t e l y q u a n t i z e t h e i n t e r v a l b e tween t i p s . A r a t e o f 16 Hz was u s ed g i v i n g 6 b i t s r e s o l u t i o n a t t h i s r a i n r a t e . A t s u f f i c i e n t l y l ow r a i n r a t e s , t i p i n t e r v a l w i l l e x c e e d t h e queue l e n g t h ( 6 . 5 m i n u t e s ) and i n e v i t a b l y d i s t o r t i o n w i l l o c c u r b e c a u s e d a t a must be w r i t t e n o n t o t a p e b e f o r e s u f f i c i e n t i n f o r m a t i o n i s a v a i l a b l e t o c o m p l e t e t h e c a l c u l a t i o n . W i t h . t h e 1/20 mm t i p s i z e d i s t o r t i o n o n l y o c c u r s f o r r a t e s b e l o w 1/2 mm/hr, a r a i n r a t e o f l i t t l e i n t e r e s t i n t h i s p r o p a g a - t i o n s t u d y . 4 . 3 . 5 Summary A r e a l t i m e d a t a l o g g i n g s y s t e m i m p l e m e n t e d on a Nova 840 m i n i - c ompu te r was d e s c r i b e d i n t h i s s e c t i o n . I t a l l o w s u n a t t e n d e d r e c o r d i n g o f m i c r o w a v e and w e a t h e r s e n s o r o u t p u t s on m a g n e t i c t a p e f o r 80 h o u r p e r i o d s . A l l d a t a a r e p r o c e s s e d so t h a t t h e y a p p e a r a s q u a n t i z e d d i s - c r e t e random v a r i a b l e s . 4 . 4 C r e a t i o n o f a D a t a Ba se 4 . 4 . 1 D a t a Ba se The d a t a b a s e t o be c r e a t e d i n t h e p r o p a g a t i o n s t u d y w i l l be a c o l l e c t i o n o f " i n t e r e s t i n g " p r o p a g a t i o n - r e l a t e d phenomena. Such phenom- ena w o u l d i n c l u d e s i g n a l l e v e l f l u c t u a t i o n s b y any a t m o s p h e r i c m e c h a n i s m and r a i n i t s e l f e ven i f no m i c r o w a v e s i g n a l were a v a i l a b l e . S h o r t p e r i o d s of the c l e a r a i r p r o p a g a t i o n p r e c e d i n g and f o l l o w i n g s t o r m a c t i v i t y w o u l d be included to a v o i d " o u t o f c o n t e x t " e v e n t s . The data base i s r e s i d e n t on l a b e l l e d m a g n e t i c t a p e . I t i s c o m - 5 7 . po sed o f u n i t l e n g t h f i l e s (1/2 h o u r o f o r i g i n a l r e c o r d i n g ) e a c h o f w h i c h has a h e a d e r d e s c r i b i n g i t s c o n t e n t s and a u n i q u e f i l e name. By t h e u s e o f l a b e l l e d t a p e f o r m a t s and h e a d e r s , d a t a f i l e s may be r e f e r e n c e d w i t h m i n i m a l k now ledge o f t h e i r p h y s i c a l c h a r a c t e r i s t i c s . R o u g h l y -250 f i l e s may be h e l d on e a c h t a p e . An e s t i m a t e o f t h e s i z e o f above d a t a b a s e i s o f i n t e r e s t . A n u p p e r bound on i t s a n n u a l g r owth may be o b t a i n e d f r o m t h e y e a r l y a c c u m u - l a t e d r a i n f a l l ; 1070 mm i n V a n c o u v e r [ 6 1 ] . I f d a t a i s s a v e d d u r i n g r a i n r a t e s e x c e e d i n g 2 mm/hr, i t i s a p p a r e n t t h a t s u c h e v e n t s c a n n o t o c c u r more t h a n 540 h o u r s p e r annum; an a n n u a l g r owth o f f i v e t a p e s o r l e s s . T h i s d a t a b a s e f o r a 5 y e a r s t u d y w o u l d be 25 m a g n e t i c t a p e s , a r e a s o n a b l e s i z e . ' 4 . 4 . 2 D a t a Base F o r m a t i o n A f t e r r e c o r d i n g on t h e Nova 840 , t h e d a t a t a p e s a r e t a k e n t o t h e IBM 370 f a c i l i t y . T h e r e , d a t a a r e r e a d f r o m t h e s e t a p e s , f o r m a t t e d t 6 t h e p r o p e r l a b e l l e d t a p e f i l e s t r u c t u r e ( t h i s i n c l u d e s s c a l i n g o f d a t a ) , e d i t e d t o e l i m i n a t e u n i n t e r e s t i n g d a t a and t h e b a l a n c e appended t o t h e pe rmanent d a t a b a s e . T h i s a c t i o n i s i n i t i a t e d t h r o u g h t h e s u b m i s s i o n o f v a r i o u s b a t c h - p r o c e s s i n g j o b s . A l t h o u g h i t i s p o s s i b l e t o do t h e a b o v e - i n a s i n g l e s t e p , t h i s i s n o t cone a t p r e s e n t b e c a u s e u n f a m i l i a r i t y w i t h t h e d a t a ha s i n h i b i t e d d e f i n i t i o n o f f o r m a l c r i t e r i a f o r d a t a s e l e c t i o n . C u r r e n t l y , a m u l t i - s t e p p r o c e s s i s u s e d , w i t h d e c i s i o n s b e i n g made by a human o b s e r v e r . The s o f t w a r e emp loyed p r o v i d e s v a r i o u s p r i n t e d and p l o t t e d summar ie s t o a i d i n the d e c i s i o n p r o c e s s . The s o f t w a r e i s w r i t t e n i n FORTRAN IV and u s e s M i c h i g a n T e r m i n a l Sy s tems (MTS) i n p u t / o u t p u t and p l o t t i n g r o u t i n e s . P r o g r ams a r e o f two t y p e s : t h o s e w h i c h t r a n s f e r t h e d a t a f r o m one t o a n o t h e r and t h o s e w h i c h p r o v i d e t he u s e r summar ies o f t h e d a t a . S p e c i f i c a l l y t h e y a r e : T r a n s f e r 1. S c a l i n g / C o n v e r s i o n : I n p u t d a t a a r e f r o m an u n l a b e l l e d t a p e w r i t t e n on t h e Nova s y s t e m a t a d e n s i t y o f 800 BP I ( b i t s p e r i n c h ) i n h a l f - wo rd i n t e g e r f o r m a t . I n p u t s a r e s c a l e d t o p r o p e r u n i t s and s e l e c t e d v a r i a b l e s a r e w r i t t e n t o t h e o u t p u t t a p e ( l a b e l l e d ) a t 1600 B P I , i n f l o a t i n g p o i n t , and i n f i l e s n o t l o n g e r t h a n 1/2 h o u r (< 64,000 v a l u e s ) . A s t a t i s t i c a l summary o f t h e v a r i a b l e s i n e ach f i l e i s p r i n t e d . A f t e r t h i s s t e p , i n p u t t a p e s may be r e t u r n e d t o t h e Nova s y s t e m t o be w r i t t e n w i t h new d a t a . 2 . T r a n s f e r t o D a t a B a s e : S e l e c t e d f i l e s f r o m the t a p e s w r i t t e n by p r o g r a m 1 a r e appended t o t h e permanent d a t a b a s e t a p e s . A f t e r t h i s s t e p j i n p u t t a p e s may b e e m p t i e d and r e u s e d i n p r o g r a m 1. Summary I n f o r m a t i o n 3. Ca lcomp P l o t t i n g : A c o l l e c t i o n o f p rog rams w r i t t e n u s i n g t h e Ca lcomp p l o t t e r a l l o w s p l o t t i n g o f s e v e r a l v a r i a b l e s t o g e t h e r as a f u n c t i o n o f t i m e . C o m b i n a t i o n s i n c l u d e a t t e n u a t i o n w i t h p a t h - a v e r a g e r a i n r a t e and i n d i v i d u a l p o i n t r a i n r a t e s w i t h p a t h - a v e r a g e r a i n r a t e . 4 . Tape L i s t i n g : T h i s p r og r am g i v e s a h i g h l y c onden sed summary o f c o n t e n t s o f e a c h f i l e s t o r e d on a p a r t i c u l a r t a p e . I t i s u s e f u l i n d a t a e d i t i n g . • The d a t a a c q u i s i t i o n s y s t e m i n v o l v e s t h e u se o f t h r e e m a g n e t i c t a p e p o o l s : 1. I n t e r m e d i a t e s t o r a g e be tween Nova 840 and IBM 370. 2. Tempora ry s t o r a g e o f P r o g r am 1 r e s u l t s p e n d i n g t r a n s f e r t o t he permanent d a t a b a s e 59. 3. Permanent data base. Tapes i n pools 1 and 2 are cycled continually while those i n pool 3 are read - only. 4.4.3 Processing Costs Because of the high volume of data to be processed, care was ex- ercised during program development to keep computing costs to reasonable levels . The approximate cost i n "computing center dol lars" per 1000 hours of or ig ina l recording with jobs run on low pr ior i ty i s : 1. Scaling/Conversion 350. 2. Plott ing ( a l l types at 1/2 hour/inch) 1000. 3. Transfer to Data Base 200. 4. Tape Lis t ing 240. Only programs 1 and 4 are run on a l l recordings made. Plott ing i s usually carried out on 20% of recordings and less than 10% are entered in the f i n a l data base. Based on continuous-recording by the data-logging system, the cost of processing data to create the data base would not ex- ceed 7100 "computing center dollars" per year. The real dol lar cost to the user would be a fraction of this amount. 60. CHAPTER V PRELIMINARY RESULTS 5.1 P o s t P r o c e s s i n g As o u t l i n e d i n S e c t i o n 4 . 4 , d a t a r e c o r d e d on m a g n e t i c t a p e by t h e d a t a a c q u i s i t i o n s y s t e m i s p a s s e d t h r o u g h s e v e r a l s t a g e s o f p r o c e s s - i n g and i s e n t e r e d i n t o t h e permanent d a t a b a s e . Samples o f t h e d a t a a t t he v a r i o u s s t a g e s a r e i n c l u d e d b e l o w . F i g . -5.1 i s a summary s h e e t o f d a t a f i l e 1 R A I N 1 0 2 8 8 4 ' s h o w i n g t he mean, s t a n d a r d d e v i a t i o n , minimum and maximum o f e a c h o f 23 v a r i a b l e s w h i c h we re r e t a i n e d o u t o f t h o s e r e c o r d e d on t h e Nova 840 . The l e n g t h o f t h e f i l e , d a t e o f r e c o r d i n g , and c e r t a i n comments a r e a l s o i n c l u d e d . The o v e r a l l c o n t e n t s o f a t a p e may more e a s i l y be a s s e s s e d w i t h a summary o f t h e t y p e g i v e n i n F i g . 5 . 2 . A s amp le o f r a i n a c t i v i t y i n p l o t t e d f o r m i s i n c l u d e d i n F i g . 5.3 ( a , b , c ) . The s a l i e n t p o i n t s a r e : t h e d u r a t i o n o f t h e r a i n i s 9 :00 a.m. t o 10 :30 a.m. t h e r a i n o c c u r s i n i d e n t i f i a b l e b u r s t s . b o t h a t t e n u a t i o n and r a i n r a t e can v a r y by a f a c t o r o f two i n l e s s t h a n one m i n u t e . However , a t t e n u a t i o n can s t i l l be c o n s i d e r e d s m o o t h - l y v a r y i n g . t he r e c e i v e r was o u t o f l o c k f o r 15 m i n u t e s a t 1 0 : 30 a .m. The s i g n a l d u r i n g t h a t p e r i o d i s t he s y s t e m n o i s e l e v e l . b o t h c r y s t a l c u r r e n t and f r e q u e n c y were s t a b l e ; hence b a s e l i n i n g t h e s i g n a l l e v e l s h o u l d be r e l i a b l e . r a i n gauges 1, 2 , and 3 f u n c t i o n e d n o r m a l l y . Number 4 was n o t i n - s t a l l e d and number 5 was m a l f u n c t i o n i n g . O t h e r s amp le s o f d a t a a r e i n c l u d e d i n F i g s . .5.4 ( a , b , c , d ) . 6 1 . * - * r H I S F I L E I S C O N T I N U O U S I N T T V S F P C - M T H E P R E V I O U S F I L E QS. \ '=R A l N 1 0 2 8 3 4 L E ' ) G T H = 1 8 0 O S = C O N 0 S S T O R E D O N A A A A A A A A D A T A A O U I S I T I G N : 3 : 4 : 7 7 O N " T O : Z 8 A A A A G L O B A L C O M M E N T : R A I N G A U G E S : 1 = F . F . , 2 =C H E M . 5 N G . r 3 =W F S BR OO.K , 5 = G A G E T O W E R S A N O i = K O ° . ! Z . W I N D , A N 0 2 = S L A N T W I N D , A N 0 3 = W I N D D I R ' M . i h ' 0 ? , A ' ! 0 6 A R E T E M P E R A T U R E S . S N 0 3 : C A P A C I T A T T ^ g S A I N G A U G E S . A M 0 4 = X T A L C U R R E N T I M .MA. P A R T I C U L A R C Q « M E N T : A A A A S i i i A i A A A ' ; A A S A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A 4 A A A A A A A A A A A A A A A A A A A A A A A A .A A A A A A A A A A A A A A A A A A A A A A A A A A A. A A A A A A A A A A A A A A A A A A. A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A . A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A ;\ A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A M E « N S T D D E V M I N I M U M M A X : A M P U D 8 ) - 8 . 2 4 0 . 9 6 - 1 1 . 1 0 - 6 . 6 0 A M P 2 ( O B ) - 3 2 7 . 6 3 C . 0 0 - 3 2 7 . 6 8 - 3 2 7 . 6 9 R . H A S ( D E C ) 1 6 3 8 . 3 0 0 . 0 0 1 6 3 8 . 3 0 1 6 3 8 . 3 0 F R E Q t K H Z ) 3 6 2 4 6 5 1 . 8 1 2 . 5 2 3 6 2 4 6 4 5 . 0 0 3 6 2 4 6 6 1 . 0 0 T ! M E ( H : M : S ) 1 5 0 4 8 7 . 8 3 2 0 3 9 . 1 3 . 1 4 5 5 4 5 . C O 1 5 2 5 4 4 . 0 0 A N O 1 { V O L T S ) - 0 . 3 6 C . 1 9 - 1 . 1 1 0 . 1 7 A N 0 2 C V O L T S ) - 0 . 1 3 0 . 1 3 - 0 . 6 3 0 . 1 5 A M 0 3 ( V O L T S J 1 . 0 1 C . 3 4 - 0 . C 3 3 . 5 3 A N 0 4 1 V O L T S ) - 2 . 0 7 0 . 0 1 - 2 . 0 8 - 2 . 0 5 A N O 5 ( V O L T S ) 0 . 4 6 0 . 0 1 0 . 4 3 0 . 4 9 A N 0 6 { V O L T S ) 6 . 4 4 0 . 0 1 0 . 4 1 0 . 4 7 A N 0 7 1 V O L T S ) - 0 . 0 1 0 . 0 0 - 0 . 0 1 0 . 0 I A K J 0 8 ( V O L T S ) - 0 . 0 1 0 . 0 0 - 0 . 0 1 0 . 0 1 A M 0 9 1 V O L T S ) - 0 . 0 4 0 . 0 0 - 0 . 0 5 - 0 . 0 3 A ' U 0 1 V O L T S ) - 0 . 0 1 0 . 0 0 - 0 . 0 2 0 . 0 0 R G \ ' 1 1 M M / H R ) 2 . 7 2 1 . 7 0 1 . 0 3 1 2 . 8 6 R G N 2 < M M / H R ) 2 . 2 4 1 . 6 7 1 . 3 0 9 . 7 2 R G N 3 ( M M / H R ) 2 . 5 9 1 . 5 3 1 . 1 9 1 4 . 3 1 R C ' I 4 ( M M / H R ) 2 . 4 2 1 . 7 0 1 . 0 9 1 5 . 1 4 R G N 5 1 M M / H R ) 1 . 6 4 C . 9 2 0 . 8 7 7 . 0 9 R G M 6 t MM / H R ) 0 . 0 C O 0 . 0 0 . 0 R C - \ ! 7 ( M M / H R ) 0 . 0 0 . 0 0 . 0 0 . 0 R O N 8 t M M / H R ) 7 1 . 6 1 2 . 1 1 6 9 . 3 3 7 3 . 7 8 O S N = R A I N 1 0 2 8 8 5 1 4 F i g . 5.1 A t y p i c a l summary sheet for a data f i l e generated i n the f i r s t processing step. o ^ ^ 4- 4> t> -4- J> i- OJ >JJ OJ OJ OJ ui t ** 1 J r o : o i o .-o ^ o o c 3 ^ t > \ f l ^ w i \ j i - , 0 £ 0 ) - j i > u i ^ w [ v j , - j ' 0 0 a - j ? o /3 o n yo o o u ^ ,« A) o u . o » o D x i , o o o o j o JO o : • ; > r> > ^ j> i> j> ; > ; > : > • r» .">;>;> i» :> i» r> T> j> OOOOOOoGOOOOOOOOGOOOOOOOoO f\J ro IO .Nl ro fO ; J FO .Nj !J fO IO :0 N> (O 1-J fO tO .'O 'O Iv) \| J PJ fs) ro OJ I'O co ao -o o rr» OJ vo IJ : J w w w -D ca -u cu .o ui j i - i - ^ U - J - O ^ ^ U ) fv» M Q J 3 - J C l O - J O ^ J M H O ^ r\j i o - j i s i i g r j , - • i •• M i - c » - t J i * 'JJ rj i J O O s j o> JI w U O O O - J O n ^ , v - OtJ o « .*J « Tj JO .rt O :« .<0 .V >3 O -C « 33 « *3 J3 >r» « 'O -̂ J r> ;> i » v » '-• z> J » I> J * •> •'-» t> X* .-• * ' • !> > i > .> ^ * i » > ... - . - . . „ . . « ._ ... . - „. , — A „ ^ - i 'z .z .-r -J: ^ ^ -z -- ~ .2 — ^ 2 J> > 0 0 0 0 0 O 0 0 0 0 . 0 0 0 0 0 0 0 0 0 0 o c o c o - r o 10 r o : o : o 10 w 1 j M r o i v : j 1̂  r o <-* i o ' o r o <v ; o rv.- i o >-J t o TI p . _jv ; . j fsj »— *-* t— —' »— f— • - * O I J » » OJ ; 0 f o -'o i M '-J fO c o t o a 3 ) c o a ^ m » :D o c o co co w s o i » 3 ^ a a c o c o a x o i c n c a » a ) c o « o ' s a co m ^ c — — ; ~ 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 o 0 0 o - t - o 0 0 0 0 0 0 C i o o o a o o o o o o o o 0 0 0 o f i ; z OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO-TIO UJ OJ U W 10 W U U >) ' J I J - J — J - g O ^ O ^ k j i v n v j i J l - o - J ~ J - O - O . - J . - O - J - J - - J - j - g - 4 -4 - j . - 4 - J - 4 - J - 0 . - 4 U l U l •vJ U DJ U W ^ -s. ^ JO 4- 4- -t- r o r\; ! \ j r o \> r o r o r o 1 M r o r o ^ M r o r o r\) ."u r o u i y i ^ 10 r o • H O M ' OJ o vo OJ .0 .a i CO CO - J o I I I t 1. I l I l I I l I I I 1 I I r o r o I r J I I I I I I 1 t I I I I l 1 I I I I l I I t i l i t 4^ 1. 1 1 1 UJ 1 1 U l 1 OJ 1 - J 1 J> 1 —J 1 4>  O I 4> 1 U l r o r o I a* 1 1 0 1 U l 1 1 -J 1 - 0 1 U l 1 U l 1 U l 1 U l 1 1 U l U l •> 1 1 0 t > 1 0 * 1 U l l •f 1 4^ U l 1 4^ 1 U l 1 U l 1 U l Ui J> t.-i —J CO ^ 10 0 U l Ul CO r o O CO U l r o 4> r o —j - j 0 O -T- tr-ee r o •J> 0 —J CO 4> CO U l U l vO - i - CO vO 0 U l UJ 0 -U l UJ OJ r o ' j i UJ 0 CO 0 r o 10 U l Ul - i 0 : . 0 4- UJ U l U l 0 O O t o UJ 1—• •43 O J—< 0 O 0 0 O 0 ^ 0 0 O 0 0 0 0 CO CO O 0 0 0 0 O 0 0 0 0 0 0 0 0 O O O O 0 O O t— O 0 0 O V_/ U l J> CO •n OJ 0 J> OJ r o U l 0 CC U l J" r o O U l u t 4> U l - J U) CO 0 - J 0 0 ~ J U i 0 r o 0 U l U l U l U» CO 1 O 0 0 0 CO r o 0 - J u i 4> - j ut r j O O J} 0 i ' j O U l 4-UJ CO ~4 O » -U l U l »-* r o r o r o - 0 r o O r n 1 U l 1 0 1 1 U l 0 1 J> 1 l 1 4> 1 ^ Ul 1 -r> U l 1 O- 1 CO t U l 1 U l ' . t JN 'Ul 1 J> 4- 1 i- - j 1 U l 1 CO 1 t 0 1 v£> 1 0 1 U l 1 1 Ul 1 I 1 —i ~~4 1 1 l 0 0 1 u> 1 ~4 1 CO 1 4> 1 U l 1 Ul l 0- 1 U l t u t < c n O 0 r o O O 03 O CO 0 r o 0 r o O CO 0 0 0 0 r o 0 0 0 u> 0 w 0 J> O •O O 0 O 0 0 0 4> 0 -J 0 0 0 O 0 0 J> 0 -T- O 0 0 —J 0 u i 4- O O 4> O fJ CO 0 0 0 0 O O 0 U l 0 0 0 0 J> O U i 0 -4 O U i 0 z U J 1 01 1 1 UJ UJ 1 IjJ 1 U l 1 J> 1 OJ 1 r- 1 OJ 1 UJ I UJ 1 U l 1 UJ 1 U l 1 J> 1 1 0 I 1 1 U l 1 0*1 1 I U l 1 U l 1 1 -r* 1 4> 1 1 f U l U l 1 Ul 1 1 0 U l 1 U l 1 U l 1 -f 1 J - 1 4> t i Ul i i - 0 0 u> 0 ^ -4 O G • j j O 0 * o ~J 0 0 0 0 CO 0 <o 0 • n . O 0 t o 0 0 0 O O - J o T O 0 O ' J l 0 —J 0 0 0 0 0 0 vO 0 0 c CO O • 0 0 4- <o O O J> 0 4> 4" O O J J 0 U", 0 0 OJ 0 r o O r o O r j O r o O O - J 0 X * 0 0 0 0 0 0 O O 0 0 0 O r-* 0 0 O 0 10 H 0 0 0 0 h * 10 0 0 O 0 O O 0 1 - O 0 0 0 0 0 O O O O 0 UJ 0 OJ 0 U l U l O ~1 0 O O r o 0 0 0 O O -J> 4> 0 oD r o —J J> J> CO - J r o O CO 0 ~4 CO 0 0 U l UJ 0 U l 0 0 O OJ r o 4^ vQ 0 0 - 0 -4 f o » -4 - J IO %D 0 0 O : o O O 0 0 O 0 0 0 0 0 0 0 0 0 0 0 0 O 0 O O 0 r u 0 0 0 0 0 0 0 O 0 0 0 O * - * O 0 0 0 0 O O O O O 0 IO 0 J> 0 0 0 O - J ~J - g J --0 0 1— O 0 0 0 O r o OJ LD U l 0 - J O r o - J 0 0 J> r o 0 <>J OJ OJ CD O 0 0 O - J U l Ul -4 r o Ul 0 0 0 0 O O O OJ U l O 0 r o 0 0 0 0 O 0 0 O O 0 0 O r - O 0 O O r o 0 0 O C 0 0 O 0 0 0 O r - O 0 0 0 0 O O O O O 0 r o O W 0 r o u i O 0 O O r o 0 0 0 U J U l OJ a> a- —J -T- - J U i fO UJ 0 U l 10 O U l 0 0 O c 10 r o O <*• o J r o - J Ul 0 4- r o O 0 O - J O O J> J> O O U J O 0 O O O O O O 0 0 0 O r o O 0 O O r o 1 - 0 0 O O ^ 0 0 O 0 O O O y O 0 O O 0 O O O O O 0 O O r o —J CO •»* O CO O U l O 0 0 0 *— -J- f— UJ u> f o u i • 09 -vl U l r o 0 0 0 - J •r- 0 O 4> r o t o ' —J 0 0 O - J i - * r o OJ r o OJ r o 0 U i UJ 0 * O r o 0 • 0 0 O O O O * 0 O O 0 O O 0 c 0 O 0 O 0 0 0 O *- 0 0 0 O t J 0 0 0 0 O >- 0 0 O 0 O O 0 f - O 0 O O 0 O O O O O 0 O UJ 0 H W M O O O O 0 O - j 0 CO 0 U l 0 r-* O r o UJ U l r o CD U l W r o 0 0* -i- 0 U l 0 r o CO O —j OT r o 0 a O 0 O Co «JD U l i> 1— r o o> J> 0 U l 0 O 0 O on O G CO 0 4> O 0 u » 3: Fig. 5.3 (a) A plot of received, signal level and path-average rain rate, for the period 0813 to 1113, February 12, 1977. Fig . 5.3 (b) . Path-average rain rate and 4 point rain rates for 0813 to 1113, February 12, 1977. U J y m i 1 1 1 -i r 8.0 8.5 9.0 9.5 10.0 10. TIMEtHQURS} . —r n. n.o 12.0 5.3 (c) Local .osc i l la tor frequency, crystal current and signal level for the period 0813 to 1113, February 12; 1977. i 9-1 r;i Fig. 5.4 (a) Received signal level and path-average rain rate for the .period 0013 to 0513,.February 12, 1977. • CO CM 1# .1/ 4.0 4.5 TIME(HQUR5) (b) Path-average rain rate and 4 point rain rates for the period 0013. to 0442, February 12, 1977. 5.0 OS   70 . I t i s e v i d e n t f r o m t h e above examp le s t h a t d a t a mus t be m a n u a l l y s c r u t i n i z e d t o some e x t e n t t o e l i m i n a t e s p u r i o u s r e s u l t s c a u s e d by e q u i p - ment f a i l u r e s . 5.2 S t a t i s t i c a l T r e a t m e n t o f t h e D a t a Base A c o l l e c t i o n o f p r o g r a m s , d e s c r i b e d i n A p p e n d i x F , a l l o w s a n a b b r e v i a t e d v e r s i o n o f s e l e c t e d d a t a f i l e s t o be p l a c e d i n d i s k s t o r a g e f o r a n a l y s i s . The d a t a u sed a r e 10 s e c o n d a v e r a g e s o f p a t h - a v e r a g e r a i n r a t e and s i g n a l l e v e l . I t i s f e l t t h a t no s u b s t a n t i a l d i s t o r t i o n was c a u s e d by t h e use o f 10 s e c o n d a v e r a g e s i n v i e w o f t h e l o w r a i n r a t e s i n v o l v e d . A s t a t i s t i c a l summary o f t h e f o r m shown i n F i g . 5,5 i s a p p e n d - ed t o each f i l e . T h i s g i v e s t he a m p l i t u d e s t a t i s t i c s o f d a t a w i t h i n 0 . 5 m m / h r - r a i n r a t e . c l a s s e s . To o b t a i n s p e c i f i c a t t e n u a t i o n (dB/km) v s r a i n r a t e , t h e b a s e - l i n e c l e a r a i r p r o p a g a t i o n s i g n a l l e v e l must be d e f i n e d . T h i s b a s e l i n e i s d e t e r m i n e d s u b j e c t i v e l y f o r e a ch f i l e b y i n s p e c t i o n o f s i g n a l l e v e l s d u r i n g z e r o o r l i g h t r a i n n e a r t h a t f i l e i n t i m e . I n c a s e s whe re i t was s u s p e c t e d t h a t s u b s t a n t i a l d r i f t s o c c u r r e d w i t h i n a f i l e , t h e d a t a was n o t u s ed f o r a n a l y s i s . I t i s f e l t t h a t b a s e l i n i n g d a t a b y t h i s method was a c c u r a t e t o ± 0 . 3 dB/km. P l o t s and t a b l e s o f a t t e n u a t i o n v s . r a i n r a t e may be p r o d u c e d f o r i n d i v i d u a l f i l e s o r g r oup s o f f i l e s . A s amp le i s g i v e n i n F i g . 5 . 6 . 5.3 C o m p a r i s o n w i t h T h e o r y Out o f t h e d a t a b a s e a v a i l a b l e a t t h e p r e s e n t t i m e , f i l e s w e r e s e l e c t e d f o r s t a t i s t i c a l a n a l y s i s i f t h e y met t h e f o l l o w i n g c r i t e r i a : 1. b o t h a m p l i t u d e and r a i n r a t e were a v a i l a b l e 2 . the s i g n a l b a s e l i n e was c e r t a i n 3. t h e y c o n t a i n e d p e r i o d s o f r a i n > 1 mm/hr. FILENAME: RAIN102299 DATA ACOUISITICN 2/12/77 3:12:42 NO. 01- SAMPLES RAIN RATE AMPLITUDE (DB) CON OS) (MM/HR) MEAN STD CEV MIN MAX 170 1.27 -8.06 0.44 -8. 73 -7.54 170 1.81 -8.50 0.31 -9.12 -7.93 110 2.24 -10.26 0.63 -11.30 -9.19 1 70 2.68 -9. 58 0. 58 -11.11 -8. 86 140 3.13 -9.72 0.54 -10.8 2 -C.85 80 3. 79 -10.49 0.55 -11.20 -9.76 1 50 4.24 • -10.82 0.30 -1 1.42 -10.34 120 4. 74 -10.97 0.33 -11.65 -10.63 120 5.19 -11.65 0.68 -12.78 -10.57 120 . 5. S2 -11.96 0.66 -12.80 -10.39 n o • 6.27 - 11.92 0.66 -12.93 -10.84 60 6.80 -12.59 0.92 -13.81 -11.14 60 7.27 -12.45 0.96 -13.96 - 1.0 . 9 6 70 7.69 -13.10 0.50 -13.78 -12.15 50 8.32 -14.54 0.77 -15.31 -13.27 40 8. S3 -14.96 0.73 -15.62 -14.03 20 9.31 -14.71 0.26 -14.90 -14.53 10 9.93 -15.36 <> 0.0 -15.36 -15.36 20 10. 14 -14.64 0.40 -14.92 -.14.36 10 10 .79 -14.86 0.0 -14.86 -14.86 ENO OF DATA DECK HIT: NORMAL FXIT EXECUTION TERMINATED CONTAINS 180 RECORDS'OF LENGTH 10 SECONDS Fig. 5.5 The s tat is t ics of attenuation-and rain rate for data f i l e 'RAIN102299' using 10 second averages. 72. ro N O . O F S A M P L F S F ( . ! M " .ATS A T T F M U 4 T I O N (Ot3/K,M) 1 R A I N 1 0 2 2 9 3 - 0 5 . 3 ( S ;CO>;DSJ ( »•!••'./HR) AN S T O OH V >•',! N f A X . 2 R A I N 1 0 2 2 9 4 - 0 5 . 3 4 9 6 0 0 . 0 6 0 . 0 0 0 . 0 9 - 0 . 2 5 0 . 6 8 3 R A I N 1 0 2 2 9 5 - 5 . 3 1 7 3 0 0 . 7 2 0 . 6 2 0 . 3 3 - 0 . 1 7 1 . 7 8 4 R A I N 1 0 2 2 9 7 - 5 . 3 1.5 9 0 1 . 2 8 1 . 2 6 0 . 2 5 0 . 53 2 . 2 6 5 R M M 1 C 2 2 9 8 - 5 . 3 1 3 5 0 1 . 7 0 ! . 5 5 0 . ? C 0 . 72 2 . 5 6 6 P. ATM 1 0 2 2 9 9 - 5 . 3 12 4 0 2 . 2 6 1 . 9 5 0 . 3 5 0 . 9 3 3 . 4 1 7 R A I N 1 0 2 3 0 0 - 5 . 3 i I 5C 2 . 7 3 2 . 0 1 0 . 2 9 . 1 . 1 5 3 . 3 0 8 R A T N 1 0 2 3 0 2 - 5 . 3 1 0 1 0 . 3 . 2 0 2 . 1 7 0 . 3 2 1 . 3 1 3 . 1 4 9 R A I N 1 0 2 3 0 3 - 5 . 2 5 1 0 5 . 76 2 . 4 2 0 . 3 6 1. 5 9 3 . 3 5 5 2 0 4 . 2 3 2 . 6 5 0 . 3 3 1. 62 3 . 4 3 3 a o . 4 . 7 2 2 . 9 3 0 . 4 0 2 . 0 1 3 . 6 4 3 10 5 . 19 3 . 2 9 0 . 3 4 2 . 16 4 . 2 5 3 1 0 5 . 7 5 3 . 3 2 0 . 4 1 2 . 0 3 4 . 2 6 1 3 0 6 . 2 4 3 . 4 5 0 . 3 0 . 1 .99 4 . 3 4 9 0 6 . S I 3 . 8 3 0 . 4 3 3 . 1 0 4 . 8 4 8 0 7 . 2 2 3 . 33 0 . 4 7 3 . 0 6 4 . 9 2 5 0 7 . 6 8 4 . 3 0 0 . 2 6 3 . 33 4 . 3 2 5 0 a . 3 2 5 . 2 5 0 . 4 4 4 . 53 5 . 6 9 4 0 8 . 83 5 . 4 9 0 . 4 1 4 . 9 6 5 . 8 6 2 0 9 . 3 1 5 . 3 5 0 . 1 5 5. 2 4 5 . 4 5 1 0 9 . 9 3 5 . 7 2 0 . 0 5 . 7 2 5 . 7 2 2 0 1 0 . 1 4 5 . 3 1 0 . 2 2 5. 1 5 5 . 4 7 . 1 0 1 0 . 7 9 5 . 4 3 0 . 0 5. 4 3 5 . 4 3 o I—t r— cn :_> 6.0 I R A I N RATE (MM/HR) a.o 1 0 . 0 i i 12.0 J 14.0 _ J 18.0 F i g . 5.6 Mean spec i f i c attenuation vs . path-average r a in rate for the period 0042, February 12, 1977 to 0512, February 12, 1977. Large *'s mark the means; small * f s one standard deviat ion about the mean. 73. The s e l e c t e d f i l e s composed some 80 ,000 d a t a r e c o r d s ( o r 25 h o u r s o f d a t a ) . A p l o t o f t h e mean a t t e n u a t i o n and one s t a n d a r d d e v i a t i o n on e i t h e r s i d e v s . r a i n r a t e t o g e t h e r w i t h t h e t h e o r e t i c a l r e l a t i o n (Ryde) i s g i v e n i n F i g . 5.7 f o r t h e t o t a l i t y o f s e l e c t e d d a t a . I t i s o b - s e r v e d t h a t t h e number o f d a t a p o i n t s above 7 mm/hr i s s m a l l and c a u t i o n s h o u l d be e x e r c i s e d i n i n t e r p r e t i n g t h e s e p o i n t s . The p l o t and t a b l e o f F i g . 5 .7 i n d i c a t e t h a t a t a p a r t i c u l a r r a i n r a t e : 1. The mean a t t e n u a t i o n c o r r e s p o n d s c l o s e l y t o t h e Ryde r e s u l t . 2 . The-ntLnimum a t t e n u a t i o n i s r a r e l y more t h a n 1.5 dB/km b e l o w t h e mean. 3. The maximum a t t e n u a t i o n i s up t o 4 dB/km a b o v e t h e mean. The d a t a i n d i c a t e t h a t d e v i a t i o n s o f a t t e n u a t i o n f r o m t h e t h e o r e t i c a l v a l u e do o c c u r and t h a t t h e y a r e n o t d i s t r i b u t e d r a n d o m l y , b u t r a t h e r , o c c u r i n b u r s t s . F o r e x a m p l e , examine F i g s . 5.4 ( a , b) and 5.6 w h i c h i n c l u d e r a i n f r o m F e b r u a r y 12 , 1977, 0030 t o 0 4 1 0 , and F i g . 5.3 ( a , b ) and F i g . 5 .8 w h i c h i n c l u d e r a i n o f l a t e r t h e same m o r n i n g . The d a t a o f 0030 t o 0410 c o n f o r m c l o s e l y t o t he t h e o r e t i c a l r e s u l t s and have s t a n d a r d d e v i a t i o n s l e s s . t h a n 0 .5 dB/km. I n c o n t r a s t , t h e d a t a o f 0900 t o 1030 h a v e s t a n d a r d d e v i a t i o n s up t o 1.5 dB/km and mean v a l u e s o f a t t e n u a t i o n s u b s t a n t i a l l y above t h e t h e o r e t i c a l . E x a m i n a t i o n o f F i g . 3a shows t h a t r a i n b u r s t s a t 0935 and 1005 c a u s e " n o r m a l " a t t e n u a t i o n s w h i l e t h a t a t 0945 c o r r e s p o n d s to an a t t e n u a t i o n s u b s t a n t i a l l y above t he t h e o r - e t i c a l v a l u e . T h i s e f f e c t i s r e s p o n s i b l e f o r t h e r e s u l t s i n F i g . 8. T h i s c o u l d p o s s i b l y be due t o v a r i a t i o n s i n t h e d r op s i z e d i s t r i b u t i o n w i t h t i m e . I n summary, mean a t t e n u a t i o n has b e e n f ound t o a g r e e c l o s e l y d i - i N O . O P S A M P L E S P. 4 ) M ' R A T E A T T E N T A T I O N ( D B / K M ) 1 ( S E C O N D S ) ( . M M / H R ) MEAN S T Q 0 E V H IN MAX j 3 3 7 4 0 0 . 0 8 0 . 0 9 0 . 2 0 - 0 . 4 0 1 . 7 7 X 3 5 5 G • 0 . 7 8 0 . 8 4 0 . 2 7 - C . 4 2 2 . 50 1 2 2 3 0 1 . 2 5 1 . 3 5 0 . 3 0 . 0 . 1 5 2 . 5 9 39 70 1. 72 1 . 6 0 0 . 3 6 0 . 4 4 3 . 3 6 t d _ 6 0 0 0 2 . 2 5 . 1 . 9 6 0 . 3 C 0 . 9 1 3 . 9 1 5 4 0 0 2 . 76 2 . 2 4 0 . 2 3 0 . 6 6 3 . 3 2 41 50 3 . 2 2 2 . 3 2 0 . 3 2 1 . 3 1 3 . 6 5 24 2 0 3 . 70 2 . 5 4 0 . 4 1 1 . 3 9 3 . 8 1 14 to 4 . 2 2 2 . 7 9 0 . 3 5 1 . 6 2 3 . 8 1 Q 11 6 0 4 . 7 0 3 . 0 4 0 . 3 3 1 . 8 1 5 . 8 6 8 9 0 5 . 2 0 3 . 3 4 0 . 5 5 1 . 9 7 8 . 7 9 6 6 0 • 5 . 7 9 3 . 5 7 0 . 4 4 2 . 0 8 3 . 4 4 4 0 0 6 . 2 5 3 . 6 0 0 . 3 1 1 . 9 9 9 . 2 4 2 r, Q 6 . 7 8 3 . 4 3 0 . 4 1 2 . 70 4 . 34 1 3 0 7 . 2 0 4 . 1 5 . 0 . 4 0 3 . 0 6 9 . 0 9 o 1 4 0 7 . 6 9 4 . 2 3 0 . 2 0 2 . 4 1 7 . 5 2 70 8 . 31 6 . 3 7 0 . 4 1 4 . 53 9 . 4 1 1 50 S . 82 6 . 2 S 0 . 3 7 4 . 96 9 . 4 3 Tr- 2 0 9 . 3 1 5 . 3 5 0 . 1 5 5 . 2 4 5 . 4 5 ie: 20 9 . 81 6 . 3 7 0 . 0 5 . 72 7 . 0 3 \ DO 20 1 0 . 1 4 5 . 3 1 0 . 2 2 5 . 1 5 5 . 4 7 Oa 1 0 1 0 . 7 9 5 . 4 3 0 . 0 5 . 4 3 5 . 4 3 § ' — i tx Z D F i g . 5.7 Mean spec i f i c attenuation vs . path-average r a in rate for the t o t a l i t y of selected data. 7 5 . o Oil ca N O . J F S A M P L E S R A I N P A T , " A T T F N U A T I O N ( D B / K M ) ( - S E C O N D S ) ( M M / H R ) M F A N S T D D F V ^ I N . N . A X . 2 1 3 0 0 . 1 6 0 . 2 4 0 . 2 7 - 0 . 1 3 1 . 2 6 1 0 6 0 . 0 . 7 2 1 . 1 4 0 . 6 0 0 . 3 0 2 . 7 3 5 0 0 1 . 2 4 1 . 8 2 0 . 4 5 C . 8 9 2 . 6 4 4 4 0 • 1 . 7 2 2 . 0 3 0 . 4 0 0 . 9 7 3 . 2 6 2 5 0 2 . 3 0 2 . 2 0 0 . 6 6 1 . 2 2 3 . 8 0 3 6 0 2 . 7 4 2 . 7 1 0 . 7 2 1 . 4 0 4 . 6 6 2 6 0 3 . 2 6 3 . 4 3 0 . 7 8 2 . 4 1 5 . 2 8 5 1 0 3 . 7 4 3 . 9 4 1 . 0 5 1 . 6 8 5 . 7 1 2 0 0 4 . 1 7 4 . 2 0 0 . 9 4 2 . 4 0 6 . 1 6 1 4 0 4 . 7 1 4 . 3 7 1 . 3 7 2 . 9 0 7 . 0 3 1 5 0 5 . 2 5 4 . 6 0 1 . 3 4 3 . 1 5 7 . 1 2 9 0 5 . 7 6 5 . 5 7 1 . 7 5 3 . 6 1 7 . 3 5 1 6 0 6 . 1 8 5 . 3 2 1 . 5 4 3 . 6 3 7 . 4 2 2 0 6 . 7 9 3 . 9 1 0 . 0 3 . 7 7 4 . 0 6 4 0 7 . 1 7 4 . 1 1 0 . 9 0 3 . 3 9 5 . 3 5 2 0 7 . 7 0 4 . 7 5 0 . 5 5 4 . 3 7 5 . 1 5 1 0 8 . 0 0 4 . 6 9 0 . 0 4 . 6 9 4 . 6 9 2 0 8 . 6 5 5 . 2 8 0 . 4 9 4 . 9 4 5 . 6 2 2 0 9 . 6 1 5 . 5 0 0 . 0 2 5 . 4 8 5 . 5 2 1 0 1 0 . 2 4 5 . 6 8 0 . 0 5 . 6 8 5 . 6 8 1 R A 1 N 1 0 2 3 1 1 - 5 . 6 2 R A T M 0 2 3 1 3 - 5 . 9 3 R A I N 1 0 2 3 1 4 - 6 . 0 4 R A I N 1 0 2 3 1 5 - 5 . 9 6 . J I RHIN RRTE (MM/HR) 8.3 10.3 I 1 2 . J J 1E.3 _J 18.3 I r i g . 5.8 Mean s p e c i f i c a t t e n u a t i o n v s . p a t h - a v e r a g e r a i n r a t e f o r t he p e r i o d 0846 t o 1046, F e b r u a r y 1 2 , 1977 . with Ryde theory for the limited range of rain rates available (0 to 10 mm/hr). Values of attenuation substantially above the mean have been shown to occur. The above results , however, are based on a very small data set and must be treated as such. 77. CHAPTER V I CONCLUSIONS AND DISCUSSION 6.1 C o n c l u s i o n s The o b j e c t i v e s o f t h i s t h e s i s h ave been m e t ; i n p a r t i c u l a r : 1. A mm-wave l i n k has been i n s t a l l e d w h i c h a l l o w s t h e a u t o m a t i c measurement o f e x c e s s p a t h a t t e n u a t i o n . 2 . A n e t w o r k o f r a i n gauges has been p o s i t i o n e d a l o n g t h e p a t h . I t p e r m i t s t he a c c u r a t e measurement o f p a t h - a v e r a g e r a i n r a t e . O t h e r m e t e o r o l o g i c a l equ i pmen t ha s a l s o been i n s t a l l e d . 3. A r e a l t i m e d a t a a c q u i s i t i o n s y s t e m ha s b e e n . i m p l e m e n t e d . I t a l l o w s t h e a u t o m a t i c r e c o r d i n g , i n a f o r m s u i t a b l e f o r l a t e r a n a l y s i s , o f d a t a f r o m t h e m i c r o w a v e and w e a t h e r s e n s o r s . 4 . S o f t w a r e t o e d i t d a t a and e n t e r i t i n t o a d a t a b a s e ha s b e e n d e v e l o p e d . I n a d d i t i o n , some 1400 h o u r s o f d a t a have been r e c o r d e d and p a s s e d t h r o u g h t h e v a r i o u s p o s t - p r o c e s s i n g s t e p s . Due t o u n u s u a l l y d r y w e a t h e r and o c c a s i o n a l equ i pmen t m a l f u n c t i o n s o n l y 25 h o u r s o f d a t a w e r e s u f f i c - i e n t l y c o m p l e t e and i n t e r e s t i n g t o w a r r a n t a n a l y s i s . P r e l i m i n a r y a n a l y - s i s o f t h e l a t t e r d a t a i n d i c a t e s t h a t t h e mean s p e c i f i c a t t e n u a t i o n a t a g i v e n r a i n r a t e a g r e e s c l o s e l y w i t h t h a t p r e d i c t e d by t h e Ryde and Ryde t h e o r y . I t ha s a l s o been shown t h a t s u b s t a n t i a l d e v i a t i o n s f r o m t h e mean o c c u r a t c e r t a i n t i m e s . 6.2 D i s c u s s i o n 6 . 2 , 1 S u g g e s t i o n s f o r Improvements t o t h e P r e s e n t S y s t em W h i l e t h e s y s t e m d e v e l o p e d i n t h i s w o r k f u n c t i o n s w e l l , i t c a n be improved by m o d i f y i n g s u b - s y s t e m s i n t he f o l l o w i n g w a y s : 78. M i c r o w a v e s y s t e m : (a ) The r e c e i v e r i s n o t a t t e n d e d 24 h o u r s a day and v a l u a b l e d a t a has been l o s t due t o t h e l o s s o f pha se l o c k . The i m p l e m e n t a t i o n o f a more r e l i a b l e r e c e i v e r w o u l d be a d v a n t a g e o u s . (b) The p r e s e n t m i x e r c o u l d a d v a n t a g e o u s l y be r e p l a c e d w i t h a more e f f i c i e n t d o w n c o n v e r t e r . ( c ) S i m i l a r l y , t h e k l y s t r o n and w a v e g u i d i n g c o u l d b e r e p l a c e d w i t h an a n t e n n a - m o u n t e d s o l i d s t a t e s o u r c e . T h i s w o u l d , r e d u c e o p e r a t i n g c o s t s a n d p o t e n t i a l l y i m p r o v e l o n g t e r m s t a b i l i t y . M e t e o r o l o g i c a l s y s t e m : (a ) The a t t e n u a t i o n c o r r e s p o n d i n g t o a g i v e n r a i n r a t e i s dependent upon t h e d r o p s i z e d i s t r i b u t i o n . An a p p r o p r i a t e measurement s y s t e m f o r d r o p s i z e d i s t r i b u t i o n i s n e c e s s a r y t o a l l o w a c c u r a t e c o m p a r i s o n o f t h e o r y and e x p e r i m e n t . (b) A t p r e s e n t , t h e anemometer i s mounted t o o c l o s e t o t h e o u t s i d e w a l l o f a b u i l d i n g t o p e r m i t r e l i a b l e measu rement s . I t s h o u l d b e moved t o a more s u i t a b l e l o c a t i o n . I n t e r f a c e : To r e d u c e down t i m e due t o component f a i l u r e s , w i r e - w r a p p e d c i r c u i t c a r d s s h o u l d be r e p l a c e d w i t h p r i n t e d c i r c u i t b o a r d s . D a t a A c q u i s i t i o n s y s t e m : T h e r e h a v e been some r e l i a b i l i t y p r o b l e m s a s s o c i a t e d w i t h t h e d a t a a c q u i s i t i o n s y s t e m when r u n unde r t he d i s k o p e r a t i n g s y s t e m (RDOS Rev . 5). As d i s k s t o r a g e i s n o t n e c e s s a r y i n t h i s a p p l i c a t i o n , i t may i m p r o v e r e l i a b i l i t y t o u se t h e c o r e - r e s i d e n t o p e r a t i n g s y s t e m (RTOS) . 79. 6 . 2 . 2 R e l a t e d Work To d raw c o n c l u s i o n s f r o m t h i s work t h e d a t a b a s e s h o u l d be e x - panded c o n s i d e r a b l y . The c o l l e c t i o n o f d a t a o v e r s e v e r a l y e a r s w o u l d seem a p p r o p r i a t e b e c a u s e o f t h e s h o r t - t e r m d e v i a t i o n s o f w e a t h e r p a t t e r n s f r o m what m i g h t be c o n s i d e r e d n o r m a l . I t i s hoped t h a t f r o m t h i s expanded d a t a b a s e , one w o u l d be a b l e t o : 1) D e t e r m i n e t h e v a l i d i t y o f c u r r e n t t h e o r e t i c a l r e l a t i o n s o f a t t e n u a t i o n t o r a i n - r a t e . - 2) D e t e r m i n e t h e s t a t i s t i c s o f d e v i a t i o n s i n a t t e n u a t i o n f r o m t h e mean t a t t e n u a t i o n a t a g i v e n r a i n r a t e . D e m o n s t r a t e t h e e x t e n t t o w h i c h s u c h d e v i a t i o n s i n c r e a s e o u t a g e t i m e s above t h o s e c a l c u l a t e d f r o m t h e mean a t t e n u a t i o n v s . r a i n r a t e r e l a t i o n . 3) G e n e r a t e a r a i n r a t e d i s t r i b u t i o n f o r t h i s a r e a . 4) D e t e r m i n e t h e a v e r a g e d r op s i z e d i s t r i b u t i o n r e l a t i o n f o r t h i s a r e a and a l s o show t h e e x t e n t o f d e v i a t i o n s f r o m t h i s a v e r a g e r e l a t i o n . 5) I f p o s s i b l e , compute t h e j o i n t p r o b a b i l i t i e s o f p o i n t r a i n r a t e s a t s e p a r a t e d l o c a t i o n s . 6) D e t e r m i n e t he r e l i a b i l i t y o f mm-wave l i n k s i n t h i s a r e a . 6 . 2 . 3 O t h e r D i r e c t i o n s f o r R e s e a r c h I n t h e l o n g e r t e r m , s e v e r a l a s p e c t s o f p r a c t i c a l i m p o r t a n c e t o mm-wave t r a n s m i s s i o n s y s t e m d e s i g n s h o u l d be i n v e s t i g a t e d . These a r e : 1) C r o s s P o l a r i z a t i o n : I n m i c r o w a v e r e l a y s , s i g n a l s may be t r a n s m i t t e d u s i n g o r t h o g o n a l p o l a r i z a t i o n s . The e x t e n t t o w h i c h power i s c o u p l e d be tween o r t h - o g o n a l p o l a r i z a t i o n s by r a i n i s o f i n t e r e s t i n . p r a c t i c a l t r a n s m i s s i o n s y s t e m s . 80 2) Long Paths: Radio transmission systems with outage times of 500 minutes/year or more are adequate for some applications. A long mm-wave l ink (5 to 10 km) should be established to measure the properties of such transmission systems. 81. APPENDIX A Mixer Evaluation As mentioned in Section 2.3.5, mixers were tested to determine which of the variet ies available was most sensitive. The sens i t iv i ty vs loca l osc i l la tor power relation for two mixers, the Sc ient i f i c Atlanta Model 13A-50 and the S/A Model 17-50, was measured and i s given in F ig . A - l . Since the available loca l osc i l la tor drive at the receiving antenna is only + 8 dBm, the S/A Model 13A-50 mixer i s clearly superior. SENSITIVITY [dBm] -80 r S/A MODEL I3A/50 5/A MODEL 17/50 + 4 + 6 +8 +10 +12 + 1 4 LOCAL OSCILLATOR POWER rdBm~} + 16 A.-l The sensi t iv i ty of two mixers as a function of loca l osc i l la tor power. 82 . APPENDIX B R a i n Gauge M o n i t o r The r a i n gauge m o n i t o r i s a s e l f c o n t a i n e d u n i t w h i c h d e t e c t s t he s t a t e o f t i p p i n g - b u c k e t r a i n guages and g e n e r a t e s a m a c h i n e - r e a d a b l e o u t p u t i n d i c a t i n g w h i c h gauges have t i p p e d d u r i n g t h e l a s t c l o c k c y c l e . The u n i t has e i g h t c h a n n e l s ; t o e a c h , a r a i n gauge may be c o n n e c t e d b y a t w i s t e d p a i r ( i n t h i s c a s e , a d e d i c a t e d t e l e p h o n e l i n e ) . The c i r c u i t d i a g r a m i s g i v e n i n F i g . B - l . A f l o a t i n g 78 v o l t b i a s i s a p p l i e d t o each l i n e t h r o u g h o p t i c a l c o u p l e r s IC 1 t o 8. T h i s p r o v i d e s 1500 v o l t i s o l a t i o n a g a i n s t l i g h t n i n g s u r g e s . S c h m i t t t r i g g e r s , IC 13 t o 16 , d e t e c t t h e l o o p c u r r e n t g i v i n g a " h i g h " o u t p u t i f t h e l o o p r e s i s t a n c e s e n s e d i s l e s s t h a n 100 K fi. I C ' s 9 t o 12 a r e w i r e d as 2 b i t s h i f t r e g i s t e r s and a r e s t r o b e d e a c h t i m e t h e o u t p u t o f t h i s u n i t i s r e a d . The o u t p u t o f e a ch c h a n n e l i s t h e e x c l u s i v e OR o f t h e two b i t s i n t h e s h i f t r e g i s t e r , t h a t i s , t h e p r e v i o u s two s t a t e s o f t h e r a i n gauge. The o u t p u t t h e n i s a " h i g h " i f t h e b u c k e t had t i p p e d i n t h e p r e v i o u s c l o c k c y c l e . The s t a t e o f e a ch r a i n gauge i s d i s p l a y e d on LD 1 t o 8, t h e o u t p u t s on LD 9 t o 16 , and an i n d i c a t i o n o f c l o c k a c - t i v i t y on LD 17 . B e c a u s e d i g i t a l c i r c u i t r y i s u s ed t h r o u g h o u t t h i s u n i t , i t may be c l o c k e d a t any r e a s o n a b l e r a t e w i t h o u t h a r d w a r e c h a n g e s . + 5 V vt-o- 3 3 Ul 6:8k.0_ RAIN GANGE ^ ^^T" 3 3k. 6.8.0. RAIN GANGE 6 8 i l N0.2 ^_^VW- 3 .3A . . 6.8A RAIN GANGE 6 8J1 H O . 3 >̂ WV— V t O 3.3-0- . 6 a a > V A - RAIN GANGE 68-Q NO. 4 X , V + O T 33J1 6 8-0. RAiN GANGE ^ 6 8 i l ~ MO.5 ^ > _ J ^ _ V» O - 3 3.0. 6EA RAIN GANSE^ eesT~ N 0 6 WV— V * o- 3 311 6an. RAIN GANGE 6 8 i l N 0 7 >̂ WV— VtO- 3 3a 6.8.0. > A V r RAIN-GANGE e.aa NO 8 >̂__/VVV— 1 5 ICI 2 4 . I l l t f l ? •AAA- - o V - 390J1 • 5V 1 '5 IC2 2 4 - o v- + 5V I 5 IC 3 Z 4 390 -WV—^ 10 12 iiai B -AAA 1 " 390.0. - A / W — ^ - O V - • SV 1 s IC4 2 4 O lk_0- 12 •AAA r^T^NB \ = ICI4 B)P 390XL -WV— - o v - 1 5 IC 5 2 4 2 inn 2 -AAA 4 ' E l C B A^» 3 9 0 A - o v - -AW— + 5V - o v - 1 5 IC6 2 4 I U 1 2 390J1 f 5V IC 7 i 4 -WV— K> l»A • 12 -WV 1 390J1 -AAA— - o v - • 5 V 1 5 ice 2 4 10 IW1 |2 AAA—T=f77̂ \6 ICI6B ] 390.0. -ov- Kr lOOH AAA f LD3 100-0. LD4 C 0 J 1 -WV • L O S icon. "^S <j- Wv f L O G . 0 100-0. "|^£> <}-—ATVv f L D 7 - , K X U I -WV f L D 8 loon. l|2J>o Kj Wv——t 6 • 5 V 4 5 4 3 -<^JI- 41 - ^ J I - 3 9 - -<^JI-20 -<JI - I4 CLOCK < J I - 4 9 100 il L0I7 2 N 4124 -5V GROUf.'D "2? X I0>JF -<^JI-50 120V AC DEV NO D £ V T Y P E IC 1-8 TIL 113 0 1 'TO ISOLATOR IC 9 - 1 2 SN 74174 H E X 0 FL IP -FLOP IC 13-16 SN 7413 GOAL 4- INPUT SClWITT TRIGEft i — IC 17-20 iSN 7 4 8 6 - C U A D 2-INPUT. EXCLUSIVE OR IC 21 SN 74175 QUAD 0 F L I P - F L O P IC 22-24 ! SN 74I& H E X O P E N COLLECTOR INVERTER L D 1-17 L IGHT E M I T T I N G D IODE T 1 C E N T E R T A P P E D 1 TO 1 T R A N S F O R M E R J l A M P H E N O L 5 7 - 4 0 5 0 0 50 PIN CONNECTOR - ^ 2 > 8 LD 9 LDO LD 11 -Kr- L 0 I 2 - o - LDI3 100 SI -WV— i c o n -Wv— 100 Si -Wv— IOOJQ. -Wv- 100.0. -WV— LDI4 - o - LDI5 LDI6 I00A -Wv- 100 i l -WV— I OOil -WV— 6 * i v DES IGNED j D Mc N : C 0 U > A f T £ D R !>.OI"if DAT E.I- E h 2 0 - T! CKD O X S i i T t OF I ATMOSPHERIC PROPAGATION OF MILLIMETRE WAVES EIGHT CHANNEL RAIN GANGE MONITOR 82 84. APPENDIX C Anemometer The anemometer d e s i g n e d f o r t h i s wo r k a l l o w s t he measurement o f h o r i z o n t a l and v e r t i c a l w i n d s peed and w i n d d i r e c t i o n . A p h o t o g r a p h were c a l i b r a t e d i n a w i n d t u n n e l t o o v e r 30 m e t e r s / s e c o n d and found t o g i v e a l i n e a r o u t p u t o f 0 .26 v o l t / m s e c ^. The p l a t f o r m t o w h i c h t h e t r a n s d u c e r s a r e mounted i s f r e e t o f a c e i n t o t h e w i n d , a l l o w i n g t h e d i r e c t i o n t o be s e n s e d w i t h a s y n c h r o g e a r e d t o t h e p l a t f o r m . A b l o c k d i a g r a m o f t h e d i r e c t i o n s e n s i n g a p p a r - a t u s i s g i v e n i n F i g . C - l . o f i t may be s e e n i n F i g . 2 . 4 . The s peed t r a n s d u c e r s a r e p r o p e l l o r d r i v e n dc g e n e r a t o r s . They ROTOR GEARED TO WIND VANE 0-2n WIDTH HOD. OUTPUT SYNCHRO. PULSE WIDTH - MODULATING SWITCHING LOGIC. B o- N GAIN ADJ.& LEVEL SHIFT. 3B&NEUT. LOW VOLT SUPPLY. INTEGRATOR. OUTPUT 0-3.6V. =r 0-360° ROTATION. o Block d i a g r a m o f w i n d d i r e c t i o n s e n s i n g a p p a r a t u s . 85. APPENDIX D I n t e r f a c e D - l P h y s i c a l C o n s t r u c t i o n The i n t e r f a c e c o m p r i s e s t h r e e a s s e m b l i e s : a 16 p o s i t i o n w i r e - wrapped b a c k p l a n e w i t h 8 c i r c u i t c a r d s , a d i s p l a y p a n e l and a . c o n n e c t o r p a n e l . The p a n e l s a r e c o n n e c t e d i n t o t h e b a c k p l a n e t h r o u g h an a d d i t i o n a l 4 c i r c u i t c a r d s . F o r r e p a i r p u r p o s e s a l l t h r e e a s s e m b l i e s a r e e a s i l y s e p a r a t e d and i n d i v i d u a l c i r c u i t c a r d s c an be p u l l e d f r o m t h e b a c k p l a n e . C a b l i n g t o t h e d i g i t a l measurement u n i t s i s v i a 50 p i n Ampheno l c o n n e c t o r s , t o a n a l o g i n p u t s on c o a x i a l c a b l e and t o t h e m i n i c o m p u t e r on a 50 p a i r c a b l e . A d i a g r a m o f t h e s e i n p u t s and t h e m a j o r components o f t h e i n t e r f a c e i s g i v e n i n F i g . D - l . Mos t o f t h e c i r c u i t c a r d s i n t h e i n t e r f a c e a r e p r e s e n t l y o f w i r e - w r a p p e d c o n s t r u c t i o n . T h i s was done t o s a v e on c o n s t r u c t i o n t i m e and t o a c h i e v e h i g h p a c k i n g d e n s i t i e s . The re have n o t , h o w e v e r , been any r e l i a b i l i t y p r o b l e m s as a ' r e s u l t o f t h i s c o n s t r u c t i o n t e c h n i q u e . D-2 O p e r a t i o n The i n s t r u c t i o n s by w h i c h d a t a a r e r e a d v i a t h e d i g i t a l m u l t i - p l e x e r and A/D c o n v e r t e r a r e g i v e n i n T a b l e D - l . The d a t a f o r m a t s a r e a l s o g i v e n t h e r e . The i n s t r u c t i o n s f o r s e t t i n g t h e i n t e r r u p t r a t e on t h e r e a l t i m e c l o c k a r e c o n t a i n e d i n T a b l e D-2. D-3 C i r c u i t D i ag rams . The c i r c u i t d i a g r ams f o r a l a r g e p a r t o f t h e i n t e r f a c e a r e i n - c l u d e d i n F i g s . D-2 - D-10. The r e m a i n i n g i n f o r m a t i o n , w h i c h i s n o t i n - c l u d e d h e r e , p e r t a i n s t o t h e A/D f i l t e r b o a r d , t h e I/O bus t e r m i n a t o r and t he b a c k p l a n e w i r i n g d i a g r a m . 86. O u t p u t Number 1 2 6 7 8 -23 Name A m p l i t u d e #1 A m p l i t u d e #2. Pha se F r e q u e n c y ( l Q ' s o f MHz) F r e q u e n c y (KHz) R a i n gauges (8 i n t o t a l ) Hou r s M i n u t e s & Seconds A/D #1 t o A/D #16 Code Fo rmat B i t <j>: 1 = 1 0 " 1 m u l t i p l i e r - 2 ij) = 10 m u l t i p l i e r B i t 1: 1 = o v e r r a nge B i t 2 : 1 = p o s i t i v e s i g n B i t s 3 t o 1 5 : 3% d i g i t s BCD as above B i t <j>: D a t a Lamp B i t 1: 1 = + s i g n B i t s 2 t o 1 5 : 3% d i g i t s BCD B i t s cj> t o 1 5 : 4 d i g i t s BCD B i t s (f> t o 1 5 : 4 d i g i t s BCD B i t <j>: R a i n gauge 1 t o B i t 7: R a i n gauge 8 B i t s <}> t o 7: 2 d i g i t s BCD B i t s if t o 7: 2 d i g i t s BCD B i t s 8 t o 1 5 : 2 d i g i t s BCD B i t s (j> t o 3: e x t e n d e d s i g n B i t s 4 t o 1 5 : 2 ' s complement A c c e s s I n s t r u c t i o n s DOA x ,45 f o l l o w e d by DIA y ,45 . R e s u l t i n ACy . DOA x , 4 5 + DIB y , 4 5 DOA x , 4 5 + DIC y , 4 5 R e s u l t i n ACy DOB x , 4 5 + DIA y , 4 5 R e s u l t i n ACy DOB x , 4 5 + DIB y , 4 5 R e s u l t i n ACy DOB x , 4 5 + DIC y , 4 5 R e s u l t i n ACy DOC x , 4 5 + DIA y , 45 DOC x , 4 5 + DIB y , 4 5 R e s u l t i n ACy NIOC 56 : c l e a r mux a d d r e s s NIOP 56 : i n c r e m e n t a d d r e s s NIOS 56 : s t a r t c o n v e r s i o n DIA y , 5 6 : r e s u l t i n ACy T a b l e D - l A c c e s s commands and ou tpu t , f o r m a t s a s s o c i a t e d w i t h t h e m i n i c o m p u t e r i n t e r f a c e . 87 . B i t P o s i t i o n 1 t o 3 F u n c t i o n n e t u s ed 0 Hz 100 Hz 10 Hz 1 Hz 0-1 Hz 0 .62 Hz ,00244 Hz G Ri I n t e r r u p t r a t e s w i t h d i v i s o r b i t s 4 -15 = 2048 and b i t s 1 t o 3 as 4 t o 15 shown. d i v i s o r i n b i n a r y (1 t o 4095) O p e r a t i o n a l I n s t r u c t i o n s D i v i s o r i n AG x . DOA x , 4 4 : s e t r a t e NIOS 4 4 : s t a r t c l o c k NIOC 4 4 : c l e a r c l o c k T a b l e D-2 S e t t i n g t h e i n t e r r u p t r a t e o f t he r e a l t i m e c l o c k . D I S P L A Y P A N E L r CIRCUIT C A R D S A N D BACK P L A N E C O N N E C T O R P A N E L 5 0 ' P I N - * - J U J Q F i g . D - l P h y s i c a l c o n f i g u r a t i o n o f t he m i n i c o m p u t e r i n t e r f a c e . • ! 1 I - Q < ixl cn < cn U J o < o < > o z Id ZD O L U CC 16 ANALOG INPUTS v I/O B U S E X T E N S I O N 88 Mzv 9 K.ZT 3 Q TEST FONT ( 2.4576 MHl) IC27 5 IUL -wv- > 82101 2 . 2 H A 24576MHr SpF | < 8 ( i r L f—i [ZD i—f̂ f" :i5pF ;68pF -VW-4 /IC32 O 2,3 IC 3 6.7 i2. II 14 5 , i + 5 v i + 5 V UkSl » r K5j ICI M II S I 12 ; I C 2 14 II S I 12 vcc vcc 10 I 2.3 IC 6 6,7 12 11 (4 5 0+5V K> I 2,3 I C 7 6,7; a. II 14 5 sv I C 8 6,7 '2 g 14 5 T ~ J X r 60 Hz vcc IC 9 7 9 10'. II I f CLOCK 1 5 12 O IC 4 14 6 7 8 3 12 13 6 1 1 C10 10 4 5 II 14 2 6 II 14 IC 13 i 4 5 12 13 IC298^X Bal O- DEVICE SELECT (44) (H) IC 31 IC 31 yTOAM) 9 V 8 ^ At>2 A«2 Ad2 Af2 » IC3 60 Hr- VCC 6 960 Hi BVI -OBV2 IC 27 tSV . PfOGRAMABLE FR&UENCY -OACI 3 12 13 6 IC II 1 10 4 • J II 14 2 3 6 II W IC 14 4 5 '2 13 Bj O+SV IC 12 5 II 14 2 • 5 V - r ° < itai 3 6 II 14 IC IS 4 5 12 13 3 6 II W IC 16 4 5 12 13 Av2 A12 Au2 As 2 Ar2 An2 Ap2 Am 2 AI2 Aj2 AK2 An2 DOpF .apF _ i z 7 V -0 + I5V Ad I -0 + I2V -O -I2V . 1 r- -O -IS V Abl -0*5 Aa2 Ba2 —O GNO Ac2,Bc2 A11, en O E V NO T Y P E DESCRIPTION iCl - I . S T 7493 4 BIT BlfJARY COUNTER T 16 IC 4 S.'J 7492 DiV'.OE B Y 2 AND 6 IC 5 - 8 SN 7 4 9 0 D E C A C E COUNTER IC 9 Sf; 74 i5 i I0F8 W U L T l P L C X E H . IC 10-12 . MC 14526 PROGRAMMABLE DIVIDER IC - I J -22 311 74175 OUAD D F L i P F L O P IC 23 MM 5375AE DIGITAL CLOCK IC 24 INTEL 3601 r - P O M 7 SEGMENT T O BCD - IC 2 6 MC 14050 H E X C M O S B U F F E R IC 25,27,28 MC I4Q4 9 H E X C M O S I N V E R T E R B U F F E R IC 2 9 - 3 0 SN 7406 H E X INVERTER/OPEN COLLECTOR IC 31 S N 7400 OUAO 2 - INPUT N A N D IC 32 MC 14049 H E X CMOS INVERTER B U F F E R IC 3 3 S N 7 4 0 8 QUAD 2 - I N P U T A N D A ,B 16PIN D I P SOCKET CONNECTOR 2 . 4 5 7 6 MH: C R Y S T A L DES IGNED J D Mc NiCOL D R A F T E D R D R 0 B N Y : K D TiM DATE F E B 1 5 - 7 7 I S S U E I S H T I OF 2 ATMOSPHERIC PROPAGATION OF MILLIMETRE WAVES NOVA COMPUTER INTERFACE - DIGITAL CLOCK CARD 4 i a >-2 8̂ 9 4 5 IC 1 17 12 2 7 1 0 15 13 I I I I 89 BIOBII BI2 9 4 IC 18 5 12 1 2 7 10. B 15 I I I I BO B4 HS B6 9 4 IC 19 5 12 13 1 2 7 O 15 I I I Al A2 A3 4 IC 20 5 12 13 15' 2 7 O I I I I A5 A6 A7 A3 IC 21 2 7 10 15 M i l . A9 AOAJI AI2 9 4 IC 5 22 12 1 0 2 7 10 15 AO i 7UNES 31 1>* I C 27 IC 29 32 D E S I G N E D J D Mc N'lCOL CRAFTED R O f iOBNY DATE FEB 2 0 - 7 7 I S3UE I | C K D JO^I SHT 2 OF 2 ATMOSPHERIC PROPAGATION OF MILLIMETRE WAVES NOVA COMPUTER INTERFACE -DIGITAL CLOCK CARD + 5V • 5V '2.2 k X iooaa ICOOil o • «W\r icoaa A 2 ( U (L) AO (L) ICZOAA K;20BA C20cA (L) 6 7 9 IC 17 14 5 4 3 2 1 13 12 II 10 i^c(jC2SC KT| (C) 5 4 C22A (B) 1 i 13 10 IC238 II 12 5 4 1 IC23A 3 2 5WB) C32F IOPUS (H) OEVICE SELECT ( H). l O O p f i , 0 0 0 i V X OATIB (M ) lOOpF 2 X 1000 TL I00PF - 1 1 0 0 3 DATIC(H) X 12 I0PLSIH ) OOpF r X 1000 A lOOpF -1- '°0°il. DATOA IH ) X IC 33 IOpF •4-f—Wv—^" . _L IOOOJI OATOB(H) X DATOC (H ) •Bo I QATIAlH) B f l -Bh2 -Bhl -Bf2 -8j2 -Bjl D £ V NO T Y P E D E S C R I P T I O N iC i -16 SN 74251 fl TO 1 MULT IPLEXER OPEN COLLECTOR IC 17 SN 74149 8 LINE PRIORITY ENCODER IC >8 - 1 9 SN 7400 QUAD 2 INPUT NAND IC 20-21 SN 74 OG HEX INVERTER B U F F E R OPEN COLLECTOR I C 2 2 - 2 3 SN 7474 DUAL D F L O P IC 24 SN 74 32 QUAD 2 INPUT OR IC 25 SN 7400 QUAD. 2 INPUT NAND IC 2 0 - 2 7 SN 74123 DUAL RETRIG MON0STA8LE MJLT!V.bRATOR IC 28 IC 2 9 - 3 0 SN 74279 QUAD S - R FLIP fltf IC 3 1 F 9301 1 LINE TO 10 L INE DEMULTIPLEXER IC 32 SN74I6 HEX INVERTER BUFFER IC 33-34 MC3C0 I Q U A D A N D GATE DES IGNED . J 0 Mc N ICOL O R A F T E D P DR08NY CK.O 1t>M D A T E F E S IS- 77 ISSUE S H T I OF 2 ATMOSPHERIC PROPAGATION OF MILLIMETRE WAVES INTERFACE-DIGITAL MULTIPLEXER S I AI a a pi At2 A2 B2C2 02 Ad2 A3 B3 C3 03 A«2 A4 64 04 04 Af 2 A5 B5 C5 05 An2 AS B6 C6 06 Aj2 A7 BT C7 07 Ak2 A8 68 C8 08 AI2 X Y V< Z Gl • 15 14 • 13 • 12 4 3 2 I ICI E 9 - F 9 - G9- H 9 - 7 II 10 9 E2- F 2. G 2 • H2 • 4 3 2 1 IC2 6 7 II 10 9 E3 F3 G3 H3 4 3 2 1 IC3 6 7 II 10 9 E4 - F4 . G4- H4- 4 3 2 1 IC4 « 7 II 10 ? E5 • F 5 . G 3 • H 5 • 4 3 2 1 ics e 7 II '10 9 E6 - F6- G6- H6- 4 3 2 1 IC6 1 7 II 10 9 E7 - F7 • G7 - H7 • 4 3 2 1 IC7 12 7 II 10 9 E8 • F 8 • G8 • H8 4 3 . I 15 j4 1 3 ICS 6 1 2 7 II 1 0 9 A9 EB C9 09 Am 2 AiO BK3 00 CIO An 2 All 611 Ol OD Ap2 4 3 2 1 IC9 i 7 II 10 9 EO_ FIO- GO- HIO- 4 3 2 1 IC 10 6 7 II 10 9 Ell. Fll- a i - H»- 4 3 2 1 IC II 6 7 II 1 0 9 AI2 BI2 02 012 Af 2 = 1 • AO B3 CO 03 As 2 AI4 B14 CM 014 At 2 AIS B>5 CS OlS Au2 AI6BI6CI6 016 Av2 EI2- FI2- GI2- HI2- 4 3 2 1 ICI2 6 II 10 9 EI3- FI3- GI3- HO- 4 3 2 1 IC 13 6 II 10 9 EI4 • FI4 • GW • HW • 4 3 2 1 ICI4 6 7 II O 9 EI5- F6- GI5- HI5" 4 3 2 1 IC 15 6 7 II 10 9 EI6 - FI6 - GI6- HI6- ;4 3 2 I •A ICI6 6 1 2 7 II 10 9 (H) (H) (H) 7 10 II IC26B g 12 0 (L) 1 14 5 4 3 IC 31 9 10 II 12 2 13 + 5V 9 m i l I V A f - IC 32 OAU Aal Acl IC32 TO LEO S START (L) -OAk I O E S l G l l C O J 0 l/c U I C O L Off A F T E O R OHOi i - IY DATE FEB 2 2 - 7 7 | IG^UC | 5 M T 2 O F 2 ATMOSPHERIC PROPAGATION OF MILLIMETRE WAVES INTERFACE-DIGITAL MULTIPLEXER •XttSJOR DESIGNATION CONf£CTOR DESIGNATION I I I 1 J I - 15 - 14 - 16 " 40- 31 " 30- 6 - 5- 29- 28- 4 - . 3 - 27- 26- 2 - I - ' SIGN. I = f OVERRATE CM MULTIPL. IQ̂ WULTIPL fCCO 8C0 2 0 0 . 100 80 4 0 20 J2_ IC I 24 25 1 50 1_ 13 II 9 I IC 2 3 5 1 3 1 2 II 10 9 8 IC 3 2 1 3 4 5 6 3 2 1 4 -* 6 7 8 A 9 10 II 1 2 13 ,M ' 15 16 NOTE I J5-45 44 20 19 43 42 18' 17. 41. 40. 16 15 39- 38- 8 i IQT 50 8 < \0*> 13 12 II 10 9 8 4 2 1 1 IC 7 2 3 4 8» 10* 4 5 6 2 13 12 1 II 10 8» 10S 9 8 4 2 2 IC 8 3 4 1 5 6 IC 9 I 2 3 4 5 16 J2 -13- 14- 16- 40- 31 - 30- 6 _ 5 - 2 9- 28- 4 - 3 " 27- 26- 2 - I - SIGN : l= + OVERRAKGE IO-'MULTIPL. O-* MULTIPL. 1000 . 809 4 0 0 200 100 80 40 20 10 13 12 II 10 9' 8 1 IC 4 j 24 25 • I >C 5 2 3 4 5 6 13 12 II 10 9 . 8 I 'C 6 2 3 4 5 6 II 12 13 14 IS 16 NOTE I J3 - 37- 36- 12- II - 35- 34- 31 30- 6 3 8-« 10S 4 » I0 6 2 x IQ6 I x I0 6 8 « 105 4 t 10' 105 i3 i ; II 10 9 8 I IC 10 2 3 4 5 6 1 10- 8 O* V— 2 - 4 10 4 2 10* 1 10* 8 I0 3 4 103 2 10* 1 105 13 II 9 I IC II 3 5 13 II . 9 I IC 12 NOTE I CONNECTOR OESOiATiON SIGN'T= V 13 12 II 9 , IC 13 3 4 5 6 DATA LAMP j 1000 PER AVG 100 PEP AVG 2« I0 2 1 « 10* 8 « 10' 13 12 II 10 9 8 IC 14 1 2 3 4 5 6 3 4,10' 2 « 10' 1 < 10' 8 x 10° j 4 « 10° 2 « 10° 13 12 II 10 9 8 IC 15 1 2 3 4 5 6 1 , 10° 8 i 10-' 4 i I0"1 .2 « I0-* • 1 , D"< 5 6 7 8 E 9 10 24 23 SO • 1_ T NOTE I J 4 - 4 5 - 4 3 - 41 3 9 - 2 0 - 18- 1 6 - 14 • NOTE I NOTES 1.1000SI ,1/8 WATT PULL UP RESISTORS TO EACH CONNECTOR PIN RA INGAVGE ' 0 ' 13 12 1 V 11 10 9 8 2 2 j , IC 17 2 V 3 4 5 6 '5' 5 6 '6' 13 12 II 10 IC 18 7 8 F ' 7 ' 25 O.SV " a Aal Abl Acl Ad I 1 3 12 II 10 g 8 IC 16 1 3 5 IILQ. t VvV- lUi k—vw- IWL 1 WV IkJL • W r IhQ 4 VvV 6 • 3V IkJl I—vw- ( L) (L) I D - J I - 4 9 - J2-49 - J3-49 -J4- 49 OE V NO D E V T Y P E IC 1 - 18 SN74 I7 HEX B U F F E R - O P E N COLLECTOR DES IGNED J D Mc NiCOL DRAFTED fi' D<=CS.\rr CKD D A T E FEB 2 0 - 7 7 ISSUE 1 SHT | OF | ATMOSPHERIC PROPAGATION OF MILLIMETRE WAVES INTERFACE-BUFFER BUS Bm2 Bml So 2 Bn I Bp2 Bpl Btl Bt2 BE2 Brl B.2 Br 2 AI2 Ap2 A»2 8d I Bit 2 Bel TO MNOOZ EI3 Pt2 TO MNOO 2 Ajl Bol (OSO) Bbl (OS I ) Bel (0S2) Bdl(DS3) BellOS 1) ) BfKOS 5) Anl(STRT) Ami (CLR) Ahl IRQENB) Ajl (MSKO) Akl (DATA X) Al IIIORSn Bll (INTA ) Bpl DATA XI Bnl DATA XI 2 OEVICE INTR INTERFACE MNOO 3 LOC 13 A ft B Brl DATA X2 Bhl SELO .AvI SEL,B Aul INTR Bkl (INTP IN) Bml (INTP IN) B> I (DEV X2) ArKOEV XI) Al l XI COMPLETE Bui X2 COMPLETE Adl XI BUSY At I X2 BUSY i I O - z z < r 2' z o o IflkA.IWATT - H l M r r -Aol Abl Acl _L. J . Adl « A«l - Aft - AM MN006 INPUT AJ 1 Akl All ( LOC ISA) Ami Anl H Apl - Arl - Atl Aul FROM MN002 E3 PIN 12,6, 8, a 10. ESPTN'IO 0 0 2 L 0 A 0 E N A B L £ °~ FROM MN002 E3 PIN4 TO MN002 EI9PINI STROBEC EOCi Btl (1 ) A|2 Bdl (2) Akl Be I (3) Ad2 Bb 1 (4) Ajl Bol (5) Af2 A» 1 (6) Ah 1 Aul (7) At2 Atl ,(8) Afl BJ 2 (9) Ah2 Bb 2 (O) Atl Bf 2 (II) Ab2 Bt 2 (12) Aol Bd2 MNOO 7 A/ D Bb2 CARD Av2 L0C.I2AaB Au2 Ar2 Ap2 Abl At 2 (8) Acl Arl (4) Apl (2) Afl2 (1 ) Am2 A|2 All - 0 4 - 5 V -O GNO -O* B V -O - I 5 V OEV. NO TYPE DE SCRI PTION IC 1.4,5,10. SN 74 00 QUAD 2-INPUT NAND IC II SN 7404 HEX INVERTER £ 12, 17-20 SN 7416 HEX OPEN COLLECTOR INVERTER IC 9,3.16 MC 3001 QUAD 2-INPUT AND IC 8,19 OM 8601 RETRIG MONOSTABLE MULTIVIBRATOR ' 1 C 2,6.7 OM 9602 DUAL MONOSTABLE MULTIVIBRATOR OESIGNED D HOLMES DRAFTED R OROBNY | CKD ToM DATE FEB 21 - 77 ] I SSUE I | SHT I OF 2 ATMOSPHERIC PROPAGATION OF MILLIMETRE VWVES INTERFACE : A / 0 CONTROL UNIT t i t - > -7 • 5V • 5V 9 API 3.9 «J1 9. ? I « fln" , 3.9UL ( + 5V 4 V2 2 C IC 2 330pF (NOP) '| -v. . l_2f NB |'£" 2 1 iZERO MUX An I 19 nn. 4 5V • 5V 9 + 5V I 22kO> Bal O - EOC IC 19 »2.2na =470pF TO . C13 PIN 13 Abl 9 + 5V 9 13 II 12 1/2 14 10 £6 i 4 . 7 u y £330 pfl J • 5V O 13 II 12 1/2 M OtC7 15 '.4-TkQ. J 39pf J33U1 B*l< 4 *3 i ce II 3 8 I 2 ^rioopF ( TRIG ) F AID (OEV. CODE) (OEV) • 5V 9 d [4 2f 6 I C 7 7 »4.7ka A*2 O— (12) AI2 fT + 5V • 5V m 9 2 5 4 1/2 2 IC6 I »4.7vn. Au2 o- Av2 O— (15) :330pF ICI IC4 SPARE -OAJI ICII 113) . ICII ' ]j| IC L 0 ^ > - ^ > ° ° A C 1 OAtl -OAdl OESIGNEO: D HOLMES C K D 3D*t DRAFTED: R DROBNY OATEFEBIS -77 jlSSUE I j SHT 2 OF 2 ATMOSPHERIC PROPAGATION OF MILLIMETRE WAVES INTERFACE :A/D CONTROL UNIT Ami O — An I O - Apl O - Arl O - A»l O - Aul O - fcdl o- Ael O- Af I O - Ahl O- I CI JJ—H IC 2 7 2 II 6 3 9 14 I C 3 7 2. II 6 Ajl O - Akl O - Al I O - AC2 O - - A / W Ikil Ao 2 O - Ad 20- Ae 20- Af 20— Ah Z O- Aj 2 O - Ak 20— Al 2 0- Am20- Ao I O- A»l o- -Wv— Z2k£L o t e y •47 mo. I 1 4 SONALERT "I IBka I I r Av2 O CLOCK 960 Hz 5V O 10 5 2 3 14 IC 7 I 12 9 e ii L S B COMMON SET Abl o FAST SET I „ "~1 Ab2 O - : 1 O . Acl O - 0*9- SLOW SET | _ IC4 7 2 II 6 9 14 I C 5 7 2 II 6 r t 5V Q 10 5 2 3 14 IC 8 I 12 9 8 II - O A " 7 B O — -02 \ 9 o - o' 9 ico- H O — r -t-5V P 10 5 2 3 ||4 IC 9 I 12 9 8 II ~ (H) (H) 0 « ' 2 MSB A»2 OEV NO OEV TYPE ICI-6 MONSANTO MAN 1 DIGIT DISPLAY 1 C7-9 SN 7493 4 BIT BINARY COUNTER IC 10 SN 7400 QUAD 2-INPUT NAND D E S I G N E D ' J D '.'c N iCOL D R A F T E D R | C K D Tan DATE F E B 2 2 - 7 7 ISSUE S M I I O F I ATMOSPHERIC PROPAGATION OF MILLIMETRE WAVES INTERFACE-DISPLAY PANEL 4 .3 D - l  APPENDIX E D a t a A c q u i s i t i o n S o f t w a r e E - l O p e r a t i o n As t h e Nova 840 m i n i c o m p u t e r f a c i l i t y was s h a r e d by many u s e r s i t was n e c e s s a r y t o a l l o w ea s y i n t e r r u p t i o n o f t h i s p r o g r a m . A s i n g l e s h e e t o f o p e r a t i n g i n s t r u c t i o n s , g i v e n i n F i g . E - l , s u p p l i e d t he e s s e n - t i a l i n f o r m a t i o n . F o r u s e r s w i t h some f a m i l i a r i t y w i t h t he c ompu te r , few p r o b l e m s w e r e e n c o u n t e r e d i n c o r r e c t l y s t o p p i n g and r e s t a r t i n g t h e p r o g r a m . A m a g n e t i c t a p e becomes f u l l a f t e r a bou t 80 h o u r s o f r e c o r d i n g . A t t h a t t ime, t h e o p e r a t o r s h o u l d s t o p t h e p r o g r a m , l o a d a b l a n k t ape a n d , w h i l e r e s t a r t i n g , n o t i f y t h e p r o g r am as t o t h e r a c k number o f t h e new t a p e and t he f i l e number ( p r e s u m a b l y ' 0 0 ' ) . T h i s a c t i o n m o d i f i e s t he c o n t e n t s o f t h e b o o k k e e p i n g f i l e ' P A R A M ' , w h i c h h o l d s t h e c u r r e n t t a p e r a c k number and t h e n e x t f i l e t o be opened . A s amp le o f t he d i a l o g u e i s c o n t a i n e d i n F i g . E - 2 . The d a t a a c q u i s i t i o n p r o g r am m a i n t a i n s a r e c o r d o f p rog ram a c t i v i t y i n a l i n e f i l e named ' L O G F I L E ' ; i n p a r t i c u l a r , i t i n d i c a t e s s t a r t i n g and s t o p p i n g t i m e s and w h i c h f i l e s w e r e w r i t t e n . A sample o f a t y p i c a l l o g e n t r y i s g i v e n i n F i g . E - 3 . The o p e r a t o r w i l l n o t e t h a t i t i s a d v i s a b l e t o d e l e t e o l d e n t r i e s o c c a s i o n a l l y t o p r e v e n t t h e l e n g t h b e c o m i n g e x c e s s i v e . E-2 S o f t w a r e Backup and R e s t o r a t i o n Th rough e i t h e r h a r d w a r e o r s o f t w a r e e r r o r s , t h e d i s k - r e s i d e n t o p e r a t i n g s y s t e m o r u s e r p rog rams may be o v e r w r i t t e n . To m i n i m i z e down - t i m e due t o t h i s , two d i s k s a r e m a i n t a i n e d I n w o r k i n g o r d e r . R e s t o r a t i o n o f d i s k s i s p e r f o r m e d on t h e m i n i c o m p u t e r f r o m a m a g n e t i c t ape b a c k u p . 98. The prodecure i s as fo l lows: 1. Perform a f u l l i n i t i a l i z a t i o n per DGC manual 093-000188-00 2. LOAD/V/R MT0:3 LOAD/V/R MT0:6 LOAD/V/R MT0:7 3. CDIR JOHN DIR JOHN <aDPO:LINK.CM@ 4. LOAD/V/R MT0:XX 5. @ASSEMBLE^ 6. @L0ADER.B@ In the above, f i l e XX contains the l a t e s t backup of the data acqu i s i t i on software. I f changes are made to the software, a new back- up may be wr i t t en by loading the above tape and entering '@BACKUP.MY@' . (Care must be taken to modify th is source f i l e so as to wr i te to the next free tape f i l e and not overwrite the previous backup.) E-3 Magnetic Tape Data Format The output i s composed of an i n t e g r a l number of records, each 32 words long and of the format given i n Table 4.2. On the tape, each f i l e contains not greater than 120 blocks of exact ly 60 records (3840 bytes) each. E-4 Software Modi f ica t ion . . Most minor adjustments to the data acqu i s i t ion software may be made by modifying the task 'START' alone. Table E - l l i s t s 6 parameters which cont ro l the output data format, the queue length, the interrupt rate and the sampling sequence. They may be changed wi th in cer ta in 99 . The s equence i n w h i c h t a s k s a r e i n i t i a t e d and t h e p r i o r i t i e s w h i c h t h e y a r e a s s i g n e d a r e c o n t a i n e d i n a t a b l e i n ' S T A R T ' . When a d d i n g new t a s k s t o t he s y s t e m , i t i s n o r m a l t o p l a c e t h e i r name and p r i o r i t y i n t h i s t a b l e . Ca re must be t a k e n t h a t p rog ram s t a r t - u p and o p e r a t i o n a r e n o t hampered by t h e new t a s k . Name LRELR NRECB NBLKF NRECQ IRATE NSAMS P r e s e n t V a l u e 3 2 . 6 0 1 2 0 4 0 0 ( 3 0 2 0 0 ) G 1 6 D e f i n i t i o n Number o f wo rd s p e r r e c o r d Number o f r e c o r d s p e r t a p e b l o c k Maximum number o f b l o c k s p e r f i l e Number o f r e c o r d s i n t h e queue I n t e r r u p t r a t e c o n t r o l wo rd [16 Hz] Number o f i n t e r r u p t s p e r d a t a r e c o r d T a b l e E - l C e r t a i n d a t a a c q u i s i t i o n p r og r am p a r a m e t e r s . WEATHER DATA AQUISITION SYSTEM FROM: J o h n M c N i c o l , Rm. 448 S t a r t i n g and S t o p p i n g P r o c e d u r e s TO STOP: 1. M o m e n t a r i l y , f l i c k s w i t c h r e g i s t e r b i t 0 t o Z e r o ( downward ) . 2 . P r e s s " R e t u r n " . 3. Remove t h e d i s k p a c k . a n d t a p e . TO START: 1. C o r r e c t l y l o a d t h e m a g n e t i c t a p e ( w i t h "REMOTE" o n ) . 2 . Connec t t h e I/O bus w i t h s w i t c h 2 up . 3. P e r f o r m t h e u s u a l s i g n on p r o c e d u r e s . 4 . Type @ GO @. 5. Respond w i t h a c a r r i a g e r e t u r n t o t h e n e x t s t a t e m e n t . 6. T h a t ' s a l l . [The m a g n e t i c t a p e s h o u l d now b e s p a c i n g f o r w a r d , o r t h e l i g h t s u n d e r t h e compute r f l a s h i n g ] . hJovA 8 4 0 . : S W I T C H B I T ^ v o o o o & o o c o c> e o o o C o o o o o a o o & & Fig . E - l Instruction sheet for the data acquisit ion system. START CURRENT TAPE.ID IS RB0889 NEXT TAPE FILE TO BE WRITTEN IS MT0:31 IF OK,RETURN. OTHERWISE ENTER 'NO' AND RETURN. NO ENTER TAPE RACK NUMBER: RB0891 ENTER TWO DIGIT FILE NUMBER: 00 CURRENT TAPE ID IS RB0891 NEXT TAPE FILE TO BE WRITTEN IS MT0:00 IF OK ̂ RETURN. OTHERWISE ENTER 'NOV AND RETURN. LOAD MAGNETIC TAPE, STRIKE ANY KEY 724 DATA AQUISITION TERMINATED Fig . E-2 Dialogue while changing tapes +++++DATA AQUISITION PROGRAM ENTRY+++++RB0889 03/15/77 23:12:25 MT.0:24 03/16/77 01:20:49 MT0:25 03/16/77 03:20:49 MT0:26 03/16/77 05:20:49 MT0:27 03/16/77 07:20:49 MT0:28 03/16/77 09:20:49 MT0:29 03/16/77 10:05:06 MT0:30 NORMAL TERMINATION AT 03/16/77 10:05:12 Fig . E - 3 A typical 'LOGFILE1 entry. It indicates that data was written.on f i l e s 24 to 29 between 2312 March 15 and 1005 March 16. . 1 0 2 . APPENDIX F P o s t - P r o c e s s i n g And A n a l y s i s P rograms F - l P o s t - P r o c e s s i n g A g e n e r a l d e s c r i p t i o n o f t h e prog rams w h i c h f a c i l i t a t e d a t a b a s e f o r m a t i o n i s g i v e n i n S e c t i o n 4 . 4 . 2 . The names o f t h e p a r t i c u l a r p rog rams and t h e r e q u i r e d d e v i c e a s s i g n m e n t s a r e g i v e n h e r e . C e r t a i n d e v i c e a s s i g n m e n t s a r e common t o a l l p r o g r a m s ; t h e y a r e : 0 = i n p u t m a g n e t i c t a p e 5 = c o n t r o l c a r d s ( u s u a l l y g i v e t a p e p o s i t i o n i n g d a t a ) 12 = a " s c r a t c h p a d " l i n e f i l e . The i n d i v i d u a l p rog rams a r e : 1. S c a l i n g / C o n v e r s i o n name = HASH2 1 = o u t p u t t a p e 10 = a l i n e f i l e c o n t a i n i n g v a r i a b l e names e t c . 2 . T r a n s f e r t o D a t a Base name = COPY 1 = o u t p u t t a p e 3. Ca lcomp P l o t t i n g name = PL0T1B , PL0T2B, PL0T3B, PL0T4B 4. Tape L i s i t i n g ( u n i t 5 n o t used) name •= DATASNIFF The f o r m a t o f t h e d a t a on l a b e l l e d t a p e i s g i v e n b y T a b l e F - l . . F -2 A n a l y s i s P rog rams To f a c i l i t a t e t h e a n a l y s i s o f d a t a a c o l l e c t i o n o f programs were written t o p l a c e an a b r e v i a t e d v e r s i o n o f d a t a b a s e f i l e s i n d i s k storage and to p r o d u c e v a r i o u s s t a t i s t i c a l summar ies o f t h e d a t a . A l l 103 . o f t h e s e p rog rams r e q u i r e a s c r a t c h pad l i n e f i l e a s s i g n e d t o u n i t 12 and a c c e p t a l i s t o f d a t a f i l e s and b a s e l i n e s i g n a l l e v e l s on u n i t 5. A s h o r t d e s c r i p t i o n o f e a c h i s g i v e n b e l o w : ' Z 3 ' T r a n s f e r s a f i l t e r e d v e r s i o n o f t h e a m p l i t u d e and p a t h - a v e r a g e r a i n r a t e t o a s e q u e n t i a l f i l e w i t h t h e same name as t h e t ape f i l e . U n i t 0 i s a s s i g n e d t o t he s o u r c e m a g n e t i c t a p e . ' Z 4 ' Computes and appends t h e s t a t i s t i c s t o s e l e c t e d f i l e s . ' Z 5 ' P r i n t s t h e i n d i v i d u a l s t a t i s t i c s o f e a ch f i l e . ' Z 6 ' P r i n t s t h e g roup s t a t i s t i c s o f t h e f i l e s s p e c i f i e d by u n i t 5. ' Z 7 ' A c c e p t s t h e b a s e l i n e s i g n a l l e v e l w i t h e a c h f i l e and p r i n t s group, s t a t i s t i c s o f a t t e n u a t i o n v s r a i n r a t e . ' Z 8 ' As Z 7 , b u t i n a d d i t i o n p l o t s t h e s t a t i s t i c s . The f o r m a t o f t h e s e q u e n t i a l f i l e u s e d h e r e i s g i v e n i n F i g . F - 2 . RECORD WORD ASSIGNMENT I A ( 2 ) = MONTH, A ( 3 ) = DAY, A ( 4 ) = YEAR A ( 5 ) = N number o f c h a n n e l s ; A ( 7 , 8 , 9) = f i l e name 2 t o 6 F i v e 6 4 - c h a r a c t e r comments 7 t o 9 The t i t l e and u n i t s a s s o c i a t e d w i t h t h e i * " * 1 c h a n n e l a r e c o n t a i n e d i n t h e i t n wo rd o f r e c o r d s 7, 8 and 9. 10 t o 14 F i v e 6 4 - c h a r a c t e r comments 15 t o end The f l o a t i n g p o i n t v a l u e s o f t h e i * " * 1 c h a n n e l a t s u c - c e s s i v e p o i n t s i n t i m e a r e g i v e n by t h e i 1 - * 1 wo rd i n s u c c e s s i v e r e c o r d s . T a b l e F - l Fo rmat o f d a t a b a s e f i l e s RECORD LENGTH NUMBER (WORDS) CONTENTS 11 A(l) = Number of words i n record 2 and 3 = N A(2) = Averaging time A(3), A(4), A(5) = Source f i l e name A(6), A(7), A(8) = MONTH/DAY/YEAR A (9 ) , A(10), A( l l ) = HOURS/MIN/SEC 2 N 3 N 4 100 Path-average rain rate at successive points i n time Amplitude at corresponding points i n time Number of sample points i n 100 classes of rain rate 5 500 To be read as a 5 x 100 matrix A(1,J) = mean path-average rain rate A(2,J) = mean amplitude of points in J*"*1 rain rate class A(3,J) = standard deviation of amplitude A(4,J) = minimum amplitude in the class A(5,J) = maximum amplitude i n the class Table F-2 Format of disk-resident s t a t i s t i c a l summaries. 1 0 5 . REFERENCES D. S i lve r thorn and R. Tetarenko, "Microwave Radio Spreads TV", T e l e s i s , V o l . 5, pp. 209-213, 1976. 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