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A proposed microwave system for on-line measurement of specific gravity and moisture content of dimension… Loo, James 1987

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A PROPOSED MICROWAVE SYSTEM FOR ON-LINE MEASUREMENT OF SPECIFIC GRAVITY AND MOISTURE CONTENT OF DIMENSION LUMBER by JAMES LOO B . A . S c , The U n i v e r s i t y of B r i t i s h  Columbia, 1985  A THESIS SUBMITTED I N PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE  in THE FACULTY OF GRADUATE STUDIES Electrical  We accept  this  Engineering  t h e s i s as conforming -  to the r e q u i r e d  standard  THE UNIVERSITY OF BRITISH COLUMBIA August 1987 © James Loo, 1987  In presenting this thesis in p a r t i a l fulfilment of the requirements for an advanced degree at The University of B r i t i s h Columbia, I agree that the Library s h a l l make i t freely available for reference and study. I further agree that permission for extensive copying of t h i s thesis for scholarly purposes may be granted by the Head of my Department or by his or her representatives. It i s understood that copying or publication of this thesis for f i n a n c i a l gain s h a l l not be allowed without my written permission.  E l e c t r i c a l Engineering The University of B r i t i s h Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1W5 Date: September  1987  ABSTRACT A 10 GHz microwave bridge measurement system has been developed to automatically measure the electromagnetic  field  parameters transmitted through a d i e l e c t r i c material. These parameters are used to calculate the complex d i e l e c t r i c constant with the free-space transmission technique. The system i s used to measure the f i e l d parameters transmitted through dimension  lumber  and a c o r r e l a t i o n i s made with two strength determining factors of lumber: s p e c i f i c gravity and moisture content. Hemlock and Douglas F i r wood samples were tested and a grading technique implemented. The system i s capable of estimating the s p e c i f i c gravity to ±0.05 accuracy and the moisture content to ±3.0% accuracy.  was  TABLE  O F CONTENTS  Abstract  i i  Table of Contents  i i i  L i s t of Figures  vi  L i s t of Tables  ix  Acknowledgements  x  1. INTRODUCTION 1.1. Background on Dimension Lumber 1.1.1. V a r i a b i l i t y in Wood 1.2. S p e c i f i c Gravity Property 1.3. Moisture Content 1.4. Grading 1.4.1. S p e c i f i c Gravity Measurements 1.4.2. Moisture Content Measurement Devices 1.4.3. Microwave meters 1.5. Thesis Objectives 1.6. Thesis Outline  1 1 1 2 4 5 7 8 9 10 10  2. DIELECTRIC PROPERTIES OF WOOD 2.1. Factors Affecting Permittivity 2.1.1. Moisture Content 2.1.2. S p e c i f i c Gravity 2.1.3. Temperature 2.2. Previous Wood Microwave Investigations 2.3. Wave Propagation in Wood 2.4. P r i n c i p l e s of Microwave Measuring Systems  12 12 12 13 13 14 16 17  3. DIELECTRIC CONSTANT MEASUREMENT SYSTEM 3.1. System Requirements 3.2. Microwave Bridge Free Space Technique 3.3. Theoretical Considerations 3.4. Transmission C o e f f i c i e n t 3.5. Frequency Selection 3.6. Measurement System Configuration 3.6.1. Microwave C i r c u i t Layout 3.6.2. Data Acquisition 3.6.3. Bridge Balancing Algorithm 3.7. Measurement System Performance 3.7.1. Accuracy 3.7.2. Speed 3.7.3. Dynamic Range  19 19 19 21 23 24 25 25 27 28 29 29 32 33  4. EXPERIMENTAL PROCEDURES AND RESULTS 4.1. Experimental Procedures  34 34  iii  4.2. Results 4.2.1. Effect of Moisture Content on 4.2.2. Effect of Specific Gravity on 4.2.3. Effect of Moisture Content on Constant 4.2.4. Effect of Specific Gravity on Constant 4.2.5. Effect of Temperature 4.2.6. Integrated Data Analysis 4.2.6.1. Grading Technique 4.2.6.2. Accuracy 4.3. Douglas F i r Data  AA and A0 .. AA and L\<p .. Dielectric Dielectric  37 37 40 40 40 49 54 57 57 60  5. CONCLUSIONS AND SUGGESTIONS FOR IMPROVEMENT 5.1. Conclusions 5.2. Limitations of the Measurement System 5.3. Further Improvements  63 63 64 66  REFERENCES  69  Appendix A Derivation of Free Space Transmission Coefficient  72  Appendix B Permittivity Calculation  75  from Free Space Measurements  APPENDIX C Data Acquisition C i r c u i t r y  78  APPENDIX D Interface C i r c u i t r y  82  APPENDIX E Bridge Balancing Program  86  Appendix F Attenuator and Phase Shifter Calibration  102  Appendix G Environmental Testing Chamber  106  Appendix H Detailed Experimental Data  107  Appendix I Photographs of the System  127  iv  Li s t  ofFigures  Fig.  1.1 Strength as a function of s p e c i f i c gravity  3  Fig.  1.2 Strength as a function of moisture content  3  F i g . 3.1 Basic microwave bridge c i r c u i t  20  F i g . 3.2 Experimental microwave bridge c i r c u i t  26  Fig. 4.1 Microwave signal p o l a r i z a t i o n  35  F i g . 4.2 Microwave measurements as a function of grain angle ..35 F i g . 4.3 Attenuation and phase s h i f t as a function of moisture content for a t y p i c a l s p e c i f i c gravity. Hemlock: transverse p o l a r i z a t i o n  38  Fig. 4.4 Attenuation and phase s h i f t as a function of moisture content for a t y p i c a l s p e c i f i c gravity. Hemlock: longitudinal polarization  39  F i g . 4.5 Attenuation and phase s h i f t as a function of moisture content for various s p e c i f i c gravities-. Hemlock: transverse polarization  41  F i g . 4.6 Attenuation and phase s h i f t as a function of moisture content for various s p e c i f i c g r a v i t i e s . Hemlock: longitudinal polarization  42  F i g . 4.7 Attenuation and phase s h i f t as a function of s p e c i f i c gravity for various moisture contents. Hemlock: transverse polarization  43  F i g . 4.8 Attenuation and phase s h i f t as a function of s p e c i f i c gravity for various moisture contents. Hemlock: longitudinal polarization  44  F i g . 4.9 Permittivity as a function of moisture for various s p e c i f i c g r a v i t i e s . Hemlock: transverse p o l a r i z a t i o n  45  F i g . 4.10 Permittivity as a function of moisture for various s p e c i f i c g r a v i t i e s . Hemlock: longitudinal polarization  content  content  F i g . 4.11 Permittivity as a function of s p e c i f i c gravity for various moisture contents. Hemlock: transverse p o l a r i z a t i o n v  46  47  F i g . 4.12 P e r m i t t i v i t y as a function of s p e c i f i c gravity for various moisture contents. Hemlock: longitudinal polarization  48  F i g . 4.13 Attenuation and phase s h i f t as a function of temperature for various moisture contents. Specific gravity=0.39. Hemlock: transverse polarization  50  F i g . 4.14 Attenuation and phase s h i f t as a function of temperature for various moisture contents. Specific gravity=0.40. Hemlock: transverse polarization  51  F i g . 4.15 Attenuation and phase s h i f t as a function of temperature for various moisture contents. Specific gravity=0.54. Hemlock: transverse polarization  52  F i g . 4.16 D i e l e c t r i c constant as a function of temperature for various moisture contents. Specific gravity=0.40. Hemlock: transverse polarization  53  F i g . 4.17 Phase s h i f t as a function of attenuation for various s p e c i f i c g r a v i t i e s and moisture contents. Hemlock: transverse polarization  55  Fig. 4.18 Phase s h i f t as a function of attenuation for various s p e c i f i c g r a v i t i e s and moisture contents. Hemlock: longitudinal polarization  56  Fig. 4.19 Phase s h i f t as a function of attenuation for various s p e c i f i c g r a v i t i e s and moisture contents. Douglas F i r : transverse polarization  61  F i g . C.1 Schematic diagram of amplifier c i r c u i t  80  Fig. C.2 Schematic diagram of analog/digital converter c i r c u i t 81 F i g . D.1 Schematic diagram of interface board #1  84  F i g . D.2 Schematic diagram of interface board #2  85  F i g . F.1 Microwave c i r c u i t for control device c a l i b r a t i o n ....103 F i g . F.2 Attenuator c a l i b r a t i o n results General Microwave Model 3455  vi  104  Fig. F.3 Phase s h i f t e r c a l i b r a t i o n results General Microwave Model 7728  105  Fig. G.1 View of the environmental testing chamber  106  F i g . H.1 Phase s h i f t as a function of attenuation. Specific gravity constant(0.36,0.38). Hemlock: transverse polarization  108  Fig. H.2 Phase s h i f t as a function of attenuation. Specific gravity constant(0.43,0.50). Hemlock: transverse polarization  109  F i g . H.3 Phase s h i f t as a function of attenuation. Specific gravity constant(0.54,0.63). Hemlock: transverse polarization  110  Fig. H.4 Phase s h i f t as a function of attenuation. Specific gravity constant(0.64). Hemlock: transverse polarization  111  Fig. H.5 Phase s h i f t as a function of attenuation. Moisture content constant(0%,3%) . Hemlock: transverse polarization  112  Fig. H.6 Phase s h i f t as a function of attenuation. Moisture content constant(6%,9%). Hemlock: transverse polarization  113  Fig. H.7 Phase s h i f t as a function of attenuation. Moisture content constant(12%,15%). Hemlock: transverse polarization  114  F i g . H.8 Phase s h i f t as a function of attenuation. Moisture content constant(18%,21%). Hemlock: transverse polarization  115  Fig. H.9 Attenuation and phase s h i f t as a function of moisture content for a t y p i c a l s p e c i f i c gravity. Douglas F i r : transverse polarization  116  F i g . H.10 Attenuation and phase s h i f t as a function of moisture content for various s p e c i f i c g r a v i t i e s . Douglas F i r : transverse polarization  117  F i g . H.11 Attenuation and phase s h i f t as a function of s p e c i f i c gravity for various moisture contents. Douglas F i r : transverse polarization  118  vii  Fig.  Fig.  Fig.  Fig.  Fig.  Fig.  Fig.  Fig.  Fig.  H.12  H.13  H.14  H.15  H.16  H.17  H.18  H.19  P e r m i t t i v i t y as a f u n c t i o n of moisture for various s p e c i f i c g r a v i t i e s . Douglas F i r : t r a n s v e r s e p o l a r i z a t i o n  content 119  P e r m i t t t i v i t y as a f u n c t i o n of s p e c i f i c g r a v i t y f o r v a r i o u s moisture contents. Douglas F i r : t r a n s v e r s e p o l a r i z a t i o n  120  Phase s h i f t as a f u n c t i o n of a t t e n u a t i o n . S p e c i f i c g r a v i t y constant(0.38,0.42). Douglas F i r : t r a n s v e r s e p o l a r i z a t i o n  121  Phase s h i f t as a f u n c t i o n of a t t e n u a t i o n . S p e c i f i c g r a v i t y constant(0.47,0.54). Douglas F i r : t r a n s v e r s e p o l a r i z a t i o n  122  Phase s h i f t as a f u n c t i o n of a t t e n u a t i o n . S p e c i f i c g r a v i t y constant(0.57,0.61). Douglas F i r : t r a n s v e r s e p o l a r i z a t i o n  123  Phase s h i f t as a f u n c t i o n of a t t e n u a t i o n . Moisture content c o n s t a n t ( 0 % , 3 % ) . Douglas F i r : t r a n s v e r s e p o l a r i z a t i o n  124  Phase s h i f t as a f u n c t i o n of a t t e n u a t i o n . Moisture content c o n s t a n t ( 6 % , 9 % ) . Douglas F i r : t r a n s v e r s e p o l a r i z a t i o n  125  Phase s h i f t as a f u n c t i o n of a t t e n u a t i o n . Moisture content c o n s t a n t ( 1 2 % ) . Douglas F i r : t r a n s v e r s e p o l a r i z a t i o n  126  1.1 View of t r a n s m i t t i n g p o r t i o n of microwave bridge c i r c u i t  127  Fig.  1.2 View of r e c e i v i n g p o r t i o n of microwave b r i d g e  128  Fig.  1.3 View of microwave b r i d g e c i r c u i t  128  Fig.  1.4 View of A/D c o n v e r t e r c i r c u i t  129  Fig.  1.5 View of i n t e r f a c e board #1  129  Fig.  1.6 View of i n t e r f a c e board #2  130  viii  Li s t of  Tables  Table 3.1 Permittivity measurement results  30  Table 3.2 Permittivity measuring errors due to control device uncertainty  31  Table 4.1 Specific gravity estimation range of Hemlock: transverse polarization  58  Table 4.2 Specific gravity estimation range of Hemlock: longitudinal polarization  59  Table 4.3 Specific gravity estimation range of Douglas F i r : transverse polarization  62  ix  ACKNOWLEDGEMENTS  I would l i k e to acknowledge my appreciation to my  research  supervisor Dr. M.M.Z. Kharadly for his keen interest, assistance, and support  throughout the course of this project.  Grateful acknowledgement i s made to the University of B r i t i s h Columbia for a University Graduate Fellowship for the academic year 1986-1987, and to the Natural Sciences  and  Engineering Research Council for support of the project under grant A3344. I also thank Forintek Canada Corporation Western Forest Products Laboratories for providing the conditioned wood samples and for providing some moisture content measuring instrumentat ion. I am grateful to Mr. Ron Green for a s s i s t i n g in the building of the environmental testing chamber, Mr. Roger Mulligan for a s s i s t i n g in the design and construction of the data a c q u i s i t i o n c i r c u i t board, and Ms. Joanna Taylor and Mr. a s s i s t i n g in measuring the wood samples.  x  Shen Liang for  1.  INTRODUCTION  j 1.1.  BACKGROUND ON DIMENSION LUMBER  Dimension 3.5  inches  sawmill's as  main  defects  such  use of dimension  material  in stress  bearing  pieces  wide  is  n a t u r a l l y produced  slope  variations  o f wood c a n d i f f e r  individual  under  conditions  properties trees.  a variety  such  i n the design specific  and the presence of  and height  specific  gravity  i n strength  occurs  growth  tends  of different  within  species  Wood  from  t o be o f l o w e r  1  soil  are alive  ages.  and  Variation  and within  p r a c t i c e s can improve  i n t r e e s . Wood  Wood  uncontrolled  location,  at different  due  trees[l2].  and e l e v a t i o n . Trees  properties  i s lowered.  trees  widely  as geographical  Silvicultural  diameter  fast-growing  on  i n t h e c h a r a c t e r i s t i c s between  wood o f d i f f e r e n t  physical  consideration  of grain,  lumber i s  structures.  p r i m a r i l y depends  p r e c i p i t a t i o n , exposure,  produce of  Strength  i s a  i n Wood  to  type,  i s a primary  content,  1.1.1. V a r i a b i l i t y  environmental  i n width,  to  knots[l2].  as  Individual  o r more  important  structures. moisture  i s 1.5 inches  which  An  wood s t r e n g t h  wooden  product  and 3 . 5 inches  product.  a construction  gravity,  a timber  i n thickness  Therefore, of  lumber,  yield  the rate of  i s increased but  i n t e n s i v e l y managed specific  gravity  than  2 wood from older slow-growing trees of the same size. Within a p a r t i c u l a r tree, the s p e c i f i c gravity of wood varies with i t s location in the tree. For instance, s p e c i f i c gravity tends to increase from p i t h to bark and from crown to base for c o n i f e r s .  1.2.  S P E C I F I C GRAVITY PROPERTY  The  s p e c i f i c gravity of wood i s a measure of the r e l a t i v e  amount of s o l i d c e l l wall material in a given volume. Basic specific gravity i s defined as: sp gr (basic) = oven dry weight of sample green volume of sample  (1)  2 expressed as a ratio to the density of water (1g/cm ). A strong relationship exists between s p e c i f i c gravity and strength of clear wood. This r e l a t i o n s h i p can be roughly approximated by the equationf21 ]: S=K(G)  (2)  n  where S i s a strength property  ( i . e . modulus of rupture,  compression p a r a l l e l to grain), K i s a proportionality constant d i f f e r i n g for each strength property, G i s the s p e c i f i c gravity, and n i s an exponent that defines the shape of the curve representing the relationship. F i g . 1.1 i l l u s t r a t e s t h i s relationship for one strength property at two moisture contents.  i 0  Fig.  1.1  '  i 0.1  1  i —i— —i— —i— —i— —i—'—i—'—i—'—f 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Specific gravity 1  1  1  1  1  S t r e n g t h as a f u n c t i o n (from Wangaard[21]) .  of s p e c i f i c  Moisture Content Fig.  1.2  S t r e n g t h as a f u n c t i o n (from Wangaard[21])•  gravity  (%) of moisture  content  4 1.3. MOISTURE CONTENT Wood i s a hygroscopic substance having an a f f i n i t y for water and other polar molecules. Moisture content in wood i s expressed as a percentage of the oven dry weight of wood: mc%= weight of wood with moisture - oven dry weight of wood x 100% (3) oven dry weight of wood Water i s held in wood in two ways: bound and free. For bound water, the water molecules are hydrogen-bonded with the c e l l wall. A s l i g h t l a t e r a l expansion of the c e l l wall occurs to accommodate bound water. When a l l available hydrogen bonding s i t e s have been occupied by l i q u i d molecules, the c e l l wall i s completely saturated. This i s c a l l e d the fiber saturation point. Above this point, usually about 30% mc, water i s stored as free water in the c e l l lumina and the wood i s referred to as green wood. Wood strength properties are greatly affected by the quantity of water present. I t s strength and e l a s t i c c h a r a c t e r i s t i c s vary inversely with i t s moisture content below the fiber saturation point as i l l u s t r a t e d in F i g . 1.2 for several strength properties!21]. The strength properties do not change with moisture content above the fiber saturation point. Knowledge of the moisture content i s important during drying because wood must be dried to a maximum moisture content of 19%  5  in order to meet building code requirements  in s t r u c t u r a l  applications. High moisture content levels affect strength and can cause glue f a i l u r e s during the manufacture of glued wood products. Freshly cut wood i s often k i l n dried to achieve the desired moisture content. Overdried wood, on the other hand, suffers from s p l i t s and twists due to shrinkage, resulting in lower commercial value and higher drying costs. The moisture content of k i l n dried lumber can vary across the length, width, and thickness of a piece of wood.  1.4.  GRADING  Over the past few decades, construction lumber has experienced a deterioration in q u a l i t y . Lumber suffers from greater warping and increased proportion of lower grades which causes problems in construct ion[22]. It i s desirable to quantify wood quality by estimating the mechanical  strength of every piece of wood as i t i s produced. The  measurement must be nondestructive so that the wood's useful properties are not affected by the measurement. Standards  exist  imposing minimum strengths for timber used in bearing structures. If quality can be rapidly and accurately estimated then wood may be more e f f i c i e n t l y used. Material and cost savings result using stress graded timber since high safety factors become unnecessary.  6 Visual grading i s most commonly used to evaluate wood q u a l i t y . Wood i s c l a s s i f i e d and sorted according to the  presence  of v i s i b l e knots and defects. The grading rules tend to be very conservative, resulting in i n e f f i c i e n t use of wood because high density timber can pass for low q u a l i t y . In addition, low density timber can pass for high quality and cause construction problems. A very e f f e c t i v e grading technique i s mechanical  stress  rating in which the s t i f f n e s s of a piece of wood i s estimated by measuring i t s deflection under a bending load. The modulus of e l a s t i c i t y can be calculated i f the wood dimensions are known. In addition, each piece receives a v i s u a l inspection for features that are important  for i t s usage. However, this device can only  measure strength in the f l a t plane and cannot measure strength at the ends of a board. Broken pieces can cause interruptions to continuous operation. Any feasible technology for stress grading of  dimension  lumber must s a t i s f y certain minimum c r i t e r i a : 1.  i t must address a l l the main factors a f f e c t i n g strength  2.  i t must recognize and accommodate the complex nature and v a r i a b i l i t y of lumber. Many of the existing techniques are technically sound but are only suitable for measuring uniform materials  3.  i t should be capable of operating continuously in a m i l l environment with minimal attention  7  4.  i t should be simple to operate, requiring minimal t r a i n i n g . It i s useful to measure two primary wood strength  indicators: s p e c i f i c gravity and moisture content, during production on-line in a m i l l . This would enable the estimation of strength and would complement a mechanical stress rating device. There are currently several d i f f e r e n t methods used for estimating these two properties of wood. One common method for measuring moisture content i s a destructive technique which consists of weighing a wood specimen before and after oven drying to zero moisture c o n t e n t [ l ] . The volume i s measured to deduce i t s s p e c i f i c gravity. This technique i s suitable for experimental purposes on a limited number of samples but i s not useful for production purposes since i t i s slow and destructive.  1.4.1. S p e c i f i c Gravity Measurements Radiation  meter:  The density of wood can be estimated by  measuring the absorption of penetrating radiation. Beta and gamma radiation can be used but they are affected by moisture and have limited range. To measure lumber of p r a c t i c a l thicknesses and moisture contents, large dosages are required. However, ionizing radiation can pose a health hazard i f not properly used. Radiation meters are also very sensitive to sensor positioning and c a l i b r a t i o n .  8  1.4.2. Moisture Content Measurement Devices DC  r e s i s t ance  meter:  The direct current resistance between two  electrodes inserted into a piece of wood i s related to the moisture content. A DC resistance meter i s inexpensive and portable. However, the measuring process i s very slow and only a small number of samples can be tested in a given time. This technique only provides the moisture content of the surface layers unless long probes are used. The estimates are dependent on species and temperature  so correction factors must be applied.  These meters are useful for spot checks but are unsuitable for continuously monitoring moisture contents on-line in a m i l l . RF  power loss  meter:  The d i e l e c t r i c constant of wood i s related  to i t s moisture content. The moisture content i s estimated from RF power loss in wood placed adjacent to two RF electrodes. This type of meter i s limited to measuring moisture content near the surface because the e l e c t r i c f i e l d decreases exponentially into the wood. The meter i s insensitive to moisture in the core of thick samples. Infrared  meter:  A given amount of heat radiation i s applied to  the surface of a piece of lumber and the temperature  of the wood  is measured with an infrared detector. Since the s p e c i f i c heat of water i s accurately known, the quantity of moisture present can be computed. Infrared devices only sense the surface moisture and are most accurate for free water. This device i s only suitable for estimating wood moisture content of green wood before drying  9 in order to estimate required drying time. These devices have limited accuracy when moisture gradients arise as a result of k i l n drying[6]. High temperature  k i l n drying  can produce very wide variations in moisture content between the shell and core. For example, the s h e l l can have 4 to 6% moisture content while the core can have 25 to 30% moisture content after an i n i t i a l drying.  1.4.3. M i c r o w a v e m e t e r s Microwaves can be used because the d i e l e c t r i c properties of wood at microwave frequencies are dependent upon moisture content, s p e c i f i c gravity, and other main properties which affect strength such as knots and slope of grain. Microwave meters allow rapid non-contact measurement and are capable of scanning wood in real time. The volume properties are measured instead of only the surface properties. Resolution can be varied by focussing and frequency selection. The fast response of microwaves i s suitable for on-line measurements with the speeds encountered environments.  in m i l l  Microwave equipment has become more affordable so  the technology i s commercially competitive. Microwave monitors have been successfully used in estimating the moisture content of materials such as coal, sand, concrete, wheat, and paper[9]. Water in these materials, however, tends to be uniformly d i s t r i b u t e d and the material density i s constant.  10  1.5. THESIS OBJECTIVES  This work i s the development  of a microwave grading system  module proposed by Kharadly[7] to measure two primary strength determining properties of wood: s p e c i f i c gravity and moisture content. In t h i s thesis, work i s undertaken to: 1.  design and implement a non-contact system that can automatically measure and continuously monitor the microwave d i e l e c t r i c properties of materials in real time  2.  experimentally determine the relationship between the d i e l e c t r i c properties of wood and i t s moisture content, s p e c i f i c gravity, and temperature for two softwood species common to B r i t i s h Columbia: Hemlock and Douglas F i r  3.  u t i l i z e the relationships observed in (2) to implement a technique for estimating the s p e c i f i c gravity and moisture content of a species from microwave measurements and assess the accuracy of the technique.  1.6. THESIS OUTLINE  Chapter 2 discusses some of the basic factors that affect wood p e r m i t t i v i t y . Chapter 3 presents a microprocessor-controlled microwave system which automatically measures the parameters of an  11  electromagnetic wave transmitted through a d i e l e c t r i c sample. Descriptions of the various sub-systems are included as well as measured system performance. The experimental results of microwave measurements on wood as a function of i t s s p e c i f i c gravity, moisture content, and temperature for two species are presented in Chapter  4. A grading  technique based on measurements i s presented and i t s accuracy i s assessed. Conclusions and suggestions for improvement and further development of the work described in this thesis are contained in Chapter  5.  2. D I E L E C T R I C PROPERTIES OF WOOD  The d i e l e c t r i c properties of a material can be expressed e x p l i c i t l y in terms of the permittivity  e=e'-e"  where  e'=e 'c r  = 0  d i e l e c t r i c constant, e"=loss factor for materials, co=angular frequency of the microwave, and e = d i e l e c t r i c constant of free 0  space. The loss tangent (tan5) i s defined as e"/e'. Permittivity is a measure of the polarization which the material undergoes in an applied electromagnetic f i e l d . The permittivity of wood i s a function of i t s water content and physical properties. The parameters of an electromagnetic f i e l d interacting with wood are related to the p e r m i t t i v i t y of wood, i t s dimensions, and the measuring system configuration.  2.1. FACTORS AFFECTING P E R M I T T I V I T Y  2.1.1. M o i s t u r e  Content  The p r i n c i p l e of microwave moisture content measurement i s based on the fact that water has a greater d i e l e c t r i c constant and i s more lossy than most dry substances at high frequencies. A small variation in water quantity can cause s i g n i f i c a n t changes in the o v e r a l l permittivity of a wet substance such as wood. For example, in the microwave frequency range, e ' of pure water t y p i c a l l y ranges from 20 to 80 and tan5 ranges from 0.05 to 1.5. 12  13 Most dry materials, on the other hand, t y p i c a l l y have e ' ranging from 1 to 4 and tan5 ranging from 0.001 to 0.2. At low moisture contents bound water in wood has r e s t r i c t e d p o l a r i z a t i o n but at higher moisture contents water has increased p o l a r i z a t i o n . The d i e l e c t r i c constant approaches that of dry wood as a minimum for low moisture contents. At higher moisture contents the water contribution increases, resulting in a higher d i e l e c t r i c constant.  2 . 1 . 2 . S p e c i f i c Gravity The s p e c i f i c gravity of wood depends on the r e l a t i v e amounts of s o l i d wood material and a i r present in a given volume. Dense wood has a larger proportion of c e l l s with thicker walls and smaller a i r c a v i t i e s . A i r has a d i e l e c t r i c constant of approximately  1.0 but s o l i d c e l l u l o s e wood substance has a value  of approximately  4.5. Hence, a relationship should exist between  the s p e c i f i c gravity of wood and d i e l e c t r i c constant.  2.1.3. Temperature The d i e l e c t r i c properties of water are functions of temperature  so the p e r m i t t i v i t y of wet wood i s also affected by  temperature[5]. Any microwave measurement system must account for temperature  e f f e c t s because wood i s graded  in a variety of  1 4  environmental conditions.  2.2.  PREVIOUS WOOD MICROWAVE INVESTIGATIONS The primary objective in microwave wood grading  i s to  correlate measured microwave properties with the physical properties of materials. Detailed observations  on the d i e l e c t r i c  properties of wood at microwave frequencies are l i m i t e d but results are available at lower  frequencies.  Many experimenters have observed the anisotropy p e r m i t t i v i t y . The d i e l e c t r i c constant  of wood  of wood longitudinal to the  grain i s greater than that transverse to the grain at a l l frequencies. S k a a r [ l 7 ] attempts to explain wood anisotropy in terms of the structure of c e l l walls. Wood c e l l c e l l u l o s e i s composed of chain molecules which are p a r a l l e l at intervals throughout their length. These form c r y s t a l l i t e s whose long axes are p a r a l l e l to the long axes of the wood c e l l s and hence p a r a l l e l to the grain. Hydroxyl groups and water molecules are arranged along the sides of the c e l l u l o s e molecules. Polarization due to rotation or vibration occurs more easily when an e l e c t r i c f i e l d i s applied p a r a l l e l to the c e l l u l o s e chains than when the electric field  i s perpendicular. This difference in dipole  polarizations accounts for the anisotropy of the d i e l e c t r i c constant.  15 Skaar[l7] and Peterson[12] observed that the complex permittivity increases with moisture content in the 2.0 MHz to 15.0 MHz range for a variety of pieces tested and found a correlation between permittivity and s p e c i f i c gravity. James and Hamill[4] investigated Douglas F i r at the three microwave frequencies of 1, 3, and 8.53 GHz and found that e' and tan5 have a well-defined relationship with moisture content for both longitudinal and transverse directions. Similar observations were made by Tinga[l9] at 2.45 GHz. However, both studies did not consider the effect of s p e c i f i c gravity variations and made no attempt to grade wood. Tiuri[20] studied the microwave properties of Finnish Spruce and Pine at 100 MHz, 1GHz, 4 GHz, and 10 GHz and observed similar patterns of increasing e' and tanS with moisture content for a limited number of samples. No difference between the d i e l e c t r i c properties of heartwood and sapwood at 10 GHz was observed. They were unable to accurately determine specific gravity using microwaves. The authors designed the Fi nnograder Stress  Grading  Machine which measures moisture content with 10 GHz microwaves and measures density with gamma radiation. The moisture content measurements must be corrected for density and the density measurements must be corrected for moisture content. However, technical d e t a i l s on the performance of the system are sparse.  16 Yen[24] used a 4.81 GHz microwave system to study the relationship between the d i e l e c t r i c properties of wood and i t s physical properties for nondestructive testing. The system used an e l e c t r i c a l l y modulated mechanically spun dipole as a scattering device for microwaves transmitted through wood samples. Yen observed trends in the d i e l e c t r i c properties of wood as a function of i t s physical properties but d i d not test enough specimens to produce a r e l i a b l e grading device. The instrumentation i s delicate and not p r a c t i c a l for use in a wood m i l l environment. Kharadly[7] noticed that a unique relationship exists between microwave parameters and the physical properties of wood using a simple microwave bridge c i r c u i t . The s p e c i f i c gravity and moisture content of wood can be simultaneously estimated by measuring the attenuation and phase s h i f t of a plane wave transmitted through wood.  2.3. WAVE PROPAGATION IN WOOD The amplitude, A, and the phase, </>, of an electromagnetic wave propagating through a medium are related to the e l e c t r i c a l parameters e, u, a of the medium. Suppose a wave i s propagating in the d i r e c t i o n of positive x: A e^x v  where:  =  [  A o  e^°][e-  ( a +  ^  ) x  ]  17 •A ,0 =amplitude and phase at x x  x  •A ,^amplitude and phase at x=0 0  • a,j3=attenuation and phase c o e f f i c i e n t s of the medium and are known functions of e, M ,  and a. a takes both ohmic and  p o l a r i z a t i o n losses into account. The microwave i s attenuated  (e ) and phase-delayed ( 0 x ) a x  r e l a t i v e to x=0 as i t propagates a distance x in the medium. If a wave i s normally  incident on a slab of material of  thickness t located between x=0 and x=t, the wave w i l l be p a r t i a l l y reflected at the interface x=0, attenuated and phase-shifted, and then p a r t i a l l y reflected at the interface x=t. These p a r t i a l r e f l e c t i o n s w i l l result in s l i g h t l y altered o v e r a l l values of attenuation and phase delay. Changes in s p e c i f i c gravity or moisture content w i l l cause changes in e and tan5 of the wood. This y i e l d s new values of attenuation and phase s h i f t .  2.4.  PRINCIPLES  OF  MICROWAVE  MEASURING  SYSTEMS  Measuring the s p e c i f i c gravity and moisture content of materials with microwave instrumentation requires[8]: 1.  determining  the r e l a t i o n s h i p between the material  p e r m i t t i v i t y , s p e c i f i c gravity and moisture content: e=f,(mc,sp gr)  18  2.  determining the relationship between the electromagnetic wave characteristics,  3.  and the material p e r m i t t i v i t y , e: $=f (e) 2  determining the relationship between the instrumentation outputs, *, and the electromagnetic wave c h a r a c t e r i s t i c s , *=f (*)• 3  The permittivity of materials i s a function f, of material state and structure. It i s also dependent on temperature and frequency. The function f  2  i s affected by measuring system design  factors such as frequency, sensor dimensions, matching. The function f  3  and impedance  depends on the design of transducers,  amplifiers, and signal processing devices. In general, the relationships are non-linear and the d i e l e c t r i c properties of multiphase mixtures are not well understood. The starting point to a p r a c t i c a l microwave instrument design i s to experimentally determine the relationships: attenuation=A(mc,sp.gr) and phase  shift=9(mc,sp.gr)  Regardless of the complexity of these relationships i t i s possible to determine the weight of water and dry material from the measured values of attenuation and phase s h i f t . Instead of exactly solving the complicated a n a l y t i c a l relations, an empirical method may be used to find: mc=M(attenuation, phase s h i f t ) and sp gr=p(attenuation, phase s h i f t )  3. D I E L E C T R I C CONSTANT MEASUREMENT SYSTEM  3.1. SYSTEM REQUIREMENTS  There are several methods available for measuring permittivity at microwave frequencies[15]. The present application requires a rapid non-contact  method suitable for  measuring large sheet samples having l i t t l e preparation. Since wood i s an inhomogeneous material, a large measurement area i s required to obtain an average value. These requirements  suggest  the use of a free-space technique. In moisture content measurements, best results have been obtained with various types of microwave bridges arranged to compare the attenuation and phase s h i f t of an unknown element with that of a standard attenuator and phase s h i f t e r [ 9 ] . A microwave bridge c i r c u i t i s favoured because of i t s low cost and simplicity for usage in an i n d u s t r i a l environment.  3.2. MICROWAVE BRIDGE FREE SPACE TECHNIQUE  A basic block diagram of a microwave bridge i s shown in F i g . 3.1. The system consists of a microwave signal which i s s p l i t into two channels: a reference channel and a test channel. The reference channel contains a variable attenuator and a variable phase s h i f t e r while the test channel contains 19  Reference  Channel  Variable Phase Shifter  Variable Attenuator Source  Matched Detector  Isolator  Isolator  Isolator Test Sample  Test F i g . 3.1  Channel  Basic microwave bridge c i r c u i t .  o  21 transmitting and receiving antennas. The two channels are combined and the signal i s incident upon a c r y s t a l diode detector whose response i s amplified and displayed. The testing section of the device consists of two horn antennas separated by a fixed distance. The transmitting  antenna  launches a l i n e a r l y polarized plane wave which i s normally incident upon a d i e l e c t r i c sample in the propagation path. A receiving antenna c o l l e c t s the signal transmitted through the dielectric. For each d i e l e c t r i c sample measurement, the attenuator and phase s h i f t e r values required to produce a n u l l at the display output are noted before and after inserting the sample in the propagation path. The difference between the device values can be related to the complex d i e l e c t r i c constant. The operation of t h i s microwave bridge i s independent  of the source power l e v e l and  detector s e n s i t i v i t y provided that the transmitted signal i s detectable.  3.3.  THEORETICAL CONSIDERATIONS The e l e c t r i c f i e l d s of the two signals propagating in the  two channels and incident upon the power combiner are assumed to have the form[3]: e =E,cos(27rft + 0) 1  22 e =E cos(27rf t + 0) 2  2  where f=microwave signal frequency, E, ,E =magnitudes in channels 2  1 and 2, and 0,0=phases i n channels  1 and 2. The general transfer  function of the detector element has the form: i=a,e+a e +...+a e +... 2  (5)  n  where e=e +e . For low signal levels, the detector response i s 1  2  e s s e n t i a l l y square law so only the second order term in the expansion i s considered. The detector output  i s fed into an amplifier whose output  voltage i s : V=*K(E, +E + 2E E cos(0-9) ) 2  (6)  2  2  1  2  where K i s a gain constant. V can be made zero i f : E +E +2E E cos(0-5)=O 2  1  (7)  2  2  1  2  which i s possible i f E,=E  2  and  <f>-8=nir,  where n=1,3,5,...  The bridge can be adjusted to a n u l l by varying the attenuator and phase s h i f t e r in the reference channel. Any change in the test channel due to an object in the test section can be compensated for by varying the two reference devices to re-acquire a n u l l . Therefore the r e l a t i v e attenuation and phase of the unknown signal introduced by a test object can be determined i f n i s known.  23 3.4.  TRANSMISSION COEFFICIENT To compute the permittivity of the unknown sample, the  transmission c o e f f i c i e n t must be known. The transmission c o e f f i c i e n t can be calculated from: •A ,0 =attenuator 0  and phase s h i f t e r setting with no sample  o  present •A,,0,=attenuator and phase s h i f t e r setting with sample present •AA=A,-A =attenuation s h i f t 0  •A0=0,-0 =phase o  shift  (in dB)  (in degrees)  The amplitude and phase of an electromagnetic wave transmitted through a d i e l e c t r i c depend on the e l e c t r i c and magnetic  properties of the medium. The transmission c o e f f i c i e n t  of a l i n e a r l y polarized plane wave normally incident upon a homogeneous d i e l e c t r i c slab of thickness 1 i s (Appendix A): T, = 3  4ze"~yl (z+1)2-( -i)2 -27l z  (8)  e  where: • z=normalized  impedance of d i e l e c t r i c sample=y/(u/e )//(u /e 0  z=1/V(1/e ) since n=u n r  0  and  e=e e r  0  where M =1 r  0  )  for non-magnetic  materials such as wood • 7=complex propagation constant in d i e l e c t r i c = j/3 /( e' (1 - jtan5)) 0  • /3 = 27r/X = free space propagation constant 0  0  •X =free space 0  wavelength  24 The measured attenuation s h i f t and phase s h i f t are related to T,  3  where: AA=|T |  The term (z-1) e 2  A0=Arg(T, )-p l  and  13  (9)  0  3  in the denominator of (8) accounts for the  2 - y l  effect of multiple internal r e f l e c t i o n s in the slab. If the material i s lossy or s u f f i c i e n t l y thick, e'^^O  so the  transmission c o e f f i c i e n t can be approximated by: T, ~4ze  71  3  (z-H)  2  ( 1 0 )  F i r s t order estimates for e' and tanS can then be a n a l y t i c a l l y obtained: e -(l + U*/p l)) ,  ,  (11)  2  0  e"/e'=tan5~ ln[r/e"((1//e')+1) /4] 2  (12)  (-M/«72) where  r=lO  _ A A / 1  °.  The exact permittivity i s obtained by solving Eq. numerically using Eqs.  (11) and  (8)  (12) as i n i t i a l guesses  (Appendix B).  3.5.  FREQUENCY SELECTION The choice of frequency depends on the type, structure,  layer thickness, and moisture content range of the material under t e s t . The diameter of the structural p a r t i c l e s must be considerably smaller than the wavelength. Softwood tracheids  25 average 25-45  nm  in diameter and 3-4 mm in length. The cost of  components at various frequencies i s important since i t determines the economic f e a s i b i l i t y of microwave wood grading versus other methods. The most commonly available and least costly microwave components are presently found at X-band ( 8 . 4 - 1 2 . 0 GHz,  2.5-3.6  cm). X-band microwaves e a s i l y meet the  wavelength size requirements and have been used by other i n v e s t i g a t o r s [ 4 , 7 , 1 4 ] to study d i e l e c t r i c behaviour of wood over a wide range of moisture contents.  3 . 6 . MEASUREMENT SYSTEM CONFIGURATION  3.6.1.  Microwave C i r c u i t Layout  The experimental setup i s shown in F i g . 3 . 2 . The source consists of a 10 GHz Varian X-13 reflex klystron. The CW signal is s p l i t among two channels by a 10 dB d i r e c t i o n a l coupler. The reference channel signal propagates through a General Microwave 8-bit d i g i t a l l y programmable PIN diode attenuator model 3358 (0-60 dB attenuation) and a General Microwave 8-bit d i g i t a l l y programmable phase s h i f t e r model 7728 ( 0 - 3 6 0 ° phase s h i f t ) . The transmission c o e f f i c i e n t s of these two devices are measured over a l l settings at an operating frequency of 1 0 . 1 9 GHz. A l l components, except for the SMA control devices, are WR90 copper waveguide propagating the dominant T E  1 0  mode. The l i n e a r l y  Microcomputer  LL Interface  R e f e r e n c e Channel Isolator A0 manual Klystron Power  F requency  Supply  Meter  Klystron  T  AA manual  AA manual  Isolator  AA digital  Matched Isolator  —> Isolator  T e s t Channel  F i g . 3.2  Analog/ Digital Converter  —»  T  Isolator  —»  A0 digital  Experimental microwave bridge c i r c u i t .  Detector  27 polarized test signal i s applied to the sample under test using pyramidal horn antennas separated by approximately 55 cm. The two channels are recombined  by a 6 dB d i r e c t i o n a l  coupler and the signals are fed into a Microwave Associates 1N23C diode detector. Various isolators placed in the c i r c u i t  minimize  the effect of mismatches and prevent the sample's reflected signal from entering the system and a f f e c t i n g the measurements. Placing i s o l a t o r s in the c i r c u i t minimizes channel interact ion[11]. A l l d i r e c t i o n a l couplers are of the high d i r e c t i v i t y type ( d i r e c t i v i t y exceeding 40 dB) to minimize passage of unwanted signals through the system.  3.6.2. Data Acquisition Automated signal l e v e l monitoring and control of the attenuator and phase s h i f t e r are performed by an Intel 8088 based microcomputer operating at 4.77 MHz. The DC diode detector response i s amplified and then d i g i t i z e d by an 8-bit analog to d i g i t a l (A/D) converter. Two separate amplifier modes e x i s t . A low gain amplifier (5X) operates when the detector output i s high (20 mV - 1V) and a higher gain (50X) amplifier operates when the output i s low (0 - 20 mV) because of the non-linear c h a r a c t e r i s t i c s of the c r y s t a l diode. When the microwave signal is high, the signal output changes rapidly but higher resolution is required when the signal level i s low to locate a signal n u l l  28 for  bridge balancing. The magnitude of the mixer output signal i s  indicated to the microcomputer v i a a status b i t and enables selection of the appropriate gain. D e t a i l s of the A/D converter board are given in Appendix C. The attenuator, phase s h i f t e r , and A/D converter are controlled by 8-bit output control signals from an Intel 8255 programmable peripheral interface connected to the 8088 address/data  3.6.3.  Bridge  bus (Appendix D).  Balancing  Algorithm  An 8088 assembly language program performs A/D sampling of the amplified detector output and controls attenuation and phase s h i f t settings to locate a n u l l . The computer alternately adjusts the two control devices u n t i l the detector signal l e v e l i s minimized. I n i t i a l l y the attenuator i s set at 0 dB while the phase s h i f t e r i s scanned from 0° to 360° in 10° increments. The phase setting that produces a minimum detector signal l e v e l serves as a f i r s t phase approximation.  The attenuator i s then  scanned from 0 dB to 20 dB in 1.0 dB increments  to search for the  minimum detector signal l e v e l . The two devices are then alternately scanned near the f i r s t approximation for  points to search  an absolute minimum l e v e l . The search i s complete when the  two control devices do not change their settings between successive scans. The exact transmission c o e f f i c i e n t for each device i s determined from a look-up table of c a l i b r a t i o n values  29 at the measuring frequency  stored in memory (Appendix F ) . This  i t e r a t i v e procedure i s necessary because the phase s h i f t e r ' s insertion loss varies with i t s phase setting and the attenuator's phase s h i f t varies with i t s attenuation setting. If the d i g i t a l attenuator were phase-free and the d i g i t a l phase s h i f t e r had a constant insertion loss, the bridge could be balanced with a single i t e r a t i o n . Details of the 8088 assembly language balancing program are provided in Appendix E.  3.7. MEASUREMENT SYSTEM PERFORMANCE  3.7.1.  Accuracy  To test the system's accuracy, various measurements were performed on several slabs of homogeneous d i e l e c t r i c test samples. The results are l i s t e d in Table 3.1. The d i e l e c t r i c constants measured using the Roberts-Von Hippel method [16] are enclosed for comparison. The d i e l e c t r i c constants are a l l within 10% of each other while the bridge-measured loss tangents tended to be inaccurate for these low loss materials. Several factors contribute to inaccurate p e r m i t t i v i t y estimates. The resolution  of the attenuator and phase s h i f t e r are  limited by the size of their least s i g n i f i c a n t b i t s . The smallest attenuator step size i s 0.25  dB and the smallest phase s h i f t e r  step size i s 1.4°. Errors of ±0.5 dB result in the estimate of AA  30  Material  Kcm)  AA(dB)  e  r  i  tan5  polystyrene  1.65  1 .4  97.8  2 .59(2 .59)  0 .028(0. 002)  expanded polystyrene  2 .50  1 .3  1 30.6  2 .03(1 .86)  0 .019(0. 004)  styrofoam  10 .30  0.0  20.7  1.03(1 .07)  0 .000(0. 023)  polythene  1.68  0.5  1 02.7  2 .28(2 .36)  0 .003(0. 003)  polythene  1.38  1 .0  91 .0  2 .33(2 .36)  0 .031(0. 003)  polythene  0 .98  0.1  61 .9  2 .30(2 .36)  0 .006(0. 003)  polythene  0 .50  1 .3  31.1  2 .28(2 .36)  0 .088(0. 003)  wood (dry)  2 .94  3.9  1 36.4  1.65(1 .61 )  0 .061(0. 037)  Table 3.1  Permittivity measurement results. Roberts-Von Hippel technique measurements enclosed in parentheses.  31  Material  e '(min)  tan5(min)  tan5(max)  polystyrene  2.49  2.62  0.001  0.032  expanded polystyrene  1 .99  2.05  0.011  0.028  styrofoam  1 .03  1 .04  -0.005  0.003  polythene  2.25  2.33  -0.020  0.017  polythene  2.28  2.38  0.007  0.056  polythene  2.12  2.30  -0.022  0.040  polythene  1 .88  2.42  -0.003  0. 1.49  wood (dry)  1 .64  1 .67  Table 3.2  r  e '(max)  0.054  0.067  Permittivity measuring errors due to control device uncertainty.  32 and errors of ±2.8° result in the estimate of A#. The minimum and maximum possible values of e  1  and tan6 for these low loss  samples resulting from such errors are l i s t e d in Table 3.2. The errors in AA are s i g n i f i c a n t for these low loss test materials to cause incorrect tan5 estimates since these errors are comparable to the magnitude of AA. However, these errors do not appreciably a f f e c t the d i e l e c t r i c constant estimates for a l o s s i e r material such as wood. AA for a 4 cm thick wood sample t y p i c a l l y  lies  between 2 dB and 20 dB and A0 t y p i c a l l y l i e s between 80° and 640° so the r e l a t i v e errors i n estimated e  1  and tan5 due to device  resolution are not as s i g n i f i c a n t . Errors also arise because the wave incident on the board deviates s l i g h t l y from an ideal plane wave. Data presented in Chapter 4 indicate that these deviations in the p e r m i t t i v i t y measurements do not a f f e c t the parameter estimates of wood since experimental data for wood exhibits scatter that exceeds these deviations.  3.7.2. Speed  The bridge requires an average of 50 msec to balance to a n u l l point using a 4.77 MHz 8088 microprocessor in an IBM PCjr microcomputer. Approximately three i t e r a t i o n s are required to n u l l the bridge when no sample i s present and approximately  five  33  i t e r a t i o n s are r e q u i r e d when wood i s p r e s e n t . T h i s corresponds  to a measurement  moves through  3.7.3.  interval  r e s o l u t i o n of 25 cm i f a sample  the t e s t s e c t i o n a t 5 m/s.  Dynamic Range  At h i g h a t t e n u a t i o n l e v e l s , the low s i g n a l s i n both are d i f f i c u l t t o d e t e c t . The microwave bridge c i r c u i t  channels  i s capable  of a c c u r a t e l y measuring a t t e n u a t i o n s up to 22 dB before the signal  l e v e l at the d e t e c t o r i s too low to balance. The system  balances when AA i s between 22 dB and 27 dB but the balance p o i n t s are not a c c u r a t e and r e p e a t a b l e . At higher a t t e n u a t i o n s , the c i r c u i t  i s unable  to balance.  4.  4.1.  EXPERIMENTAL  EXPERIMENTAL  PROCEDURES  AND  RESULTS  PROCEDURES  The microwave bridge c i r c u i t detailed in Chapter 3 was used to measure attenuation and phase s h i f t in dimension wood samples at 10.19  GHz.  I n i t i a l measurements were performed using a manually controlled attenuator and phase s h i f t e r in the reference branch of the microwave bridge c i r c u i t . The microwave source i s modulated by a 1 KHz signal and an analog HP 415E  standing wave  indicator monitors the output signal l e v e l of the detector. Bridge balancing i s performed by manually adjusting the control devices u n t i l a voltage n u l l is v i s u a l l y i d e n t i f i e d at the indicator. Microwave measurements were performed on wood samples of a p a r t i c u l a r species having d i f f e r i n g s p e c i f i c g r a v i t i e s and moisture contents. Two polarizations were used: transverse and longitudinal. The e l e c t r i c f i e l d i s oriented perpendicular to the grain d i r e c t i o n for transverse polarization and the e l e c t r i c f i e l d i s oriented p a r a l l e l to the grain d i r e c t i o n for longitudinal polarization as shown in F i g . 4.1. The effects of small deviations in the polarization are shown in F i g . 4.2. Angular deviations of less than 15° in the polarization do not 34  r  200  00  c ~o 3 C CD  Angle (degrees) F i g . 4.2  Microwave measurements as a f u n c t i o n of g r a i n a n g l e .  36 s i g n i f i c a n t l y affect the measured quantities so naturally occurring small slope of grain angles do not a f f e c t the measurements. Approximately 100 samples of clear, knot-free Hemlock having an approximate  size of 23 cm x24 cm x 4 cm and varying s p e c i f i c  g r a v i t i e s were conditioned in a humidity chamber to roughly 25% moisture content. Measurements were performed on these pieces in the environmental chamber (Appendix G) with both p o l a r i z a t i o n s . The samples were a i r - d r i e d and measurements were repeated. Each sample was weighed immediately before i t was measured. As air-drying became d i f f i c u l t at approximately 8% moisture content, the samples were heated in a microwave oven and allowed to cool to room temperature between measurements. This process was continued u n t i l the samples did not lose any weight between dryings in the microwave oven. At t h i s point the pieces were considered oven dry. The s p e c i f i c gravity of each sample was computed and the moisture content at each measuring  stage was  evaluated from the intermediate weighings. A l l measurements were performed at room temperature  (19°C to 23°C).  The Hemlock samples ranged in thickness from 3.6 cm to 4.1 cm with an average thickness of 3.8 cm. The measurements were normalized to 3.8 cm using a linear scaling factor because AA and A# are l i n e a r l y related to thickness for small thickness deviations[24].  37 4.2. RESULTS  4.2.1. Effect of Moisture Content on AA and Atf> Figs. 4.3 and 4.4 show the variation of AA and A0 with moisture content for one t y p i c a l s p e c i f i c gravity. The anisotropic d i e l e c t r i c property of wood i s evident. The general shape of the attenuation graph agrees with that obtained by Purslow[l4] in that the attenuation increases exponentially with bound moisture content. The attenuation increases slowly with moisture content in the 0% to about 8% range and then increases rapidly with higher moisture contents. According to Stamm[l8], this i s due to a change in response between mono-molecularly  held  and poly-molecularly held water. At lower moisture contents water is bound mono-molecularly  and i s so strongly bonded to the wood  substance that the molecules have limited mobility. Attenuation is minimal since minimal energy i s lost from the waves as they traverse the wood. From about 8% to 25% moisture content, the attenuation changes rapidly with increasing moisture content. The poly-molecularly held water becomes predominant, with i t s weaker bonding. This behaviour was observed for both p o l a r i z a t i o n s . Anisotropy in phase s h i f t measurements was also observed.  350-1  HEMLOCK frequency = 10.19 GHz tranverse polarization specific gravity=0.38  100-  Legend o  50-  10  15  20  samplel  »  sample2  •  sample3  25  Moisture Content (%)  F i g . 4.3 Attenuation and phase s h i f t as a function of moisture content for a t y p i c a l specific gravity. Hemlock: transverse p o l a r i z a t i o n .  40  39  450  :  HEMLOCK  400-  frequency=10.19 GHz longitudinal polarization specific gravity=0.38  350300  :  250  :  o 1  200-  8  4  a  150-; 100  Legend  :  o samplel 50  o sample2  J  • sample3  0-  10 15 Moisture Content (%)  Fig.  4.4  20  25  A t t e n u a t i o n and phase s h i f t as a f u n c t i o n of moisture content f o r a t y p i c a l specific gravity. Hemlock: l o n g i t u d i n a l p o l a r i z a t i o n .  40 4.2.2. E f f e c t  of Specific  G r a v i t y on AA a n d A#  Figs. 4.5 and 4.6 show the variation of AA and A0 with moisture content for various s p e c i f i c g r a v i t i e s . As s p e c i f i c gravity increases, AA and A0 tend to increase for a particular moisture content. Figs. 4.7 and 4.8 e x p l i c i t l y i l l u s t r a t e the effect of s p e c i f i c gravity for various moisture contents.  4.2.3. E f f e c t  o f M o i s t u r e C o n t e n t on D i e l e c t r i c C o n s t a n t  The variation of e ' and tan6 with moisture content i s shown in Figs. 4.9 and 4.10 for various s p e c i f i c g r a v i t i e s . The d i e l e c t r i c constant and loss tangent increase with moisture contents for both polarizations as expected.  4.2.4. E f f e c t  of Specific  G r a v i t y on D i e l e c t r i c C o n s t a n t  Figs. 4.11 and 4.12 show the variation of e * and tan5 with s p e c i f i c gravity for various moisture contents. The effect of s p e c i f i c gravity on p e r m i t t i v i t y i s not as s i g n i f i c a n t as the e f f e c t of moisture content. These relationships between the d i e l e c t r i c and physical properties of wood show similar trends to those obtained by other researchers using lower frequencies and d i f f e r e n t measurement techniques!17,23,24].  However, these measurements used a i r and  oven dried wood having a moisture gradient, representative of  25  41 HEMLOCK  transverse polarization  Legend A sg=0.36 * sg-0-38 •  59=0.43  B sg=0.50 a sg=0.54 x sg=0.63 5  10  15  Moisture Content  20  25  (%)  500 HEMLOCK  transverse polarization  Legend A sg=0.36 x sg=0.38 • sg=0.43 H sg=0.50 s sg=0.54  5  10  15  Moisture Content  Fig.  4.5  (%)  A t t e n u a t i o n and phase s h i f t a s a f u n c t i o n of moisture content for various s p e c i f i c g r a v i t i e s . Hemlock: t r a n s v e r s e polarization.  HEMLOCK longitudinal polarization  Legend A  sg=0.36  x sg=0.38 •  sg=0.43  H sg=0.50 ffi sg=0.54 * -i  1 1  r5  -i 10  15  1 1 1 1 120  sg=0.63  25  Moisture Content (%)  700HEMLOCK  longitudinal polarization 600  500  400-  Legend A  sg=0.36  x sg=0.38 •  sg=0.43  H sg-0.50  100-  ffi sg=0.54 x 10  -i—i—i—[— 15  20  sgfO^^  25  Moisture Content (%)  4.6  A t t e n u a t i o n a n d phase s h i f t a s a f u n c t i o n o f moisture content f o r various s p e c i f i c g r a v i t i e s . Hemlock: l o n g i t u d i n a l polarization.  25 HEMLOCK  transverse polarization  20-  CQ 3,  15-  o c  10-  C  Legend A mc=05 x mc=6%  5-  • mc=12% H mc=18% —1—1—1—1—1—1—1—r-  35  0.40  T-r-r0.45  T  1 1 [ T-  0.50  1  1'  0.55  1  1  1  1 1 1 1  1 0.60  1 0.65  Specific Gravity  500 HEMLOCK  transverse polarization  400CO  300CO  Legend  <x> Vi  D CL SI  A  200-  mc=0%  x mc=6% • mc=12% H mc=18% 1—I—1—1—1—1—1—;—1—1—1—j—1—1—1—1—1—1—1—1—1—j—1—1—1—1—1  0.35  0.40  0.45  0.50  0.55  0.60  0.65  Specific Gravity  F i g . 4.7 Attenuation and phase s h i f t as a function of s p e c i f i c gravity for various moisture contents. Hemlock: transverse p o l a r i z a t i o n .  Fig.  4.8  Attenuation and phase s h i f t as a function of s p e c i f i c gravity for various moisture contents Hemlock: longitudinal p o l a r i z a t i o n .  45 HEMLOCK  transverse polarization  3.5-  C _o (/> c o  CJ  o  Legend  2.5-  A sg=0.36  o  x sg=0.38 •  b  sg=0.43  B sg=0.50 S sg=0.54 x sg=0.63  "l— —' 1  10  5  15  20  25  Moisture Content (%)  0.30 HEML0CK  transverse polarization  0.25-  Legend A sg=0.36 x sg=0.38 •  sg=0.43  8 sg=0.50 B sg=q.54  0.00  x sg=0.63 -1  1  |  5  1  I  I  1  1  10  15  I  20  -i  1  1 j  25  Moisture Content (%)  F i g . 4.9  P e r m i t t i v i t y as a f u n c t i o n of moisture content for various s p e c i f i c g r a v i t i e s . Hemlock: t r a n s v e r s e p o l a r i z a t i o n .  46 HEMLOCK longitudinal polarization  Legend A sg=0.36 sg  =0.38  sg  =0.43  sg =0.50 =0.54 sg  5  i  1 1  r~  10 5 20 Moisture Content (%) 1  =0.63  i 25  0.5HEMLOCK longitudinal polarization  Legend A  sg=0.36  x sg=0.38 •  sg=0.43  B  sg=0.50  a sg=0.54  5  F i g . 4.10  10 15 20 Moisture Content (%)  Permittivity as a function of moisture content for various s p e c i f i c g r a v i t i e s . Hemlock: longitudinal p o l a r i z a t i o n .  HEMLOCK  transverse polarization 3.5  c c o  o -5?  Legend 2  A mc=0% x mc=6%  1.5-  O mc=12% B mc=18% -i—|—i—i—i—r-  0.35  0.40  0.45  I 0.60 1  0.50  0.55  1  1  1  1  I 0.65  Specific Gravity  0.30-1 HEMLOCK  transverse polarization  0.25-  -£  0.20  Ui  c  £  0.15  cn in O  Legend  0.10-1  A mc=0% x mc=6%  0.05  • mc=12% B mc=18%  0.00  T 1 1 1  0.35  i g . 4.11  11  0.40  J 0.45  1 1 1  I ' 0.50 1  1  -  1  1  '  I  1  0.55  '  1  1  ' 0.60 I  1  1  1  I 0.65  Specific Gravity  Permittivity as a function of s p e c i f i c gravity for various moisture contents. Hemlock: transverse p o l a r i z a t i o n .  Fig.  4.12  Permittivity as a function of s p e c i f i c gravity for various moisture contents. Hemlock: longitudinal p o l a r i z a t i o n .  49 i n d u s t r i a l conditions, while other researchers used conditioned wood with uniform moisture content. Lint 10] did not find a correlation between p e r m i t t i v i t y and s p e c i f i c gravity at 1 KHz. At this lower frequency, i n t e r f a c i a l , dipolar, atomic, and electronic polarizations contribute to the p e r m i t t i v i t y . Hence, small impurities in wood and s l i g h t variations in chemical composition affect the p e r m i t t i v i t y more than differences in s p e c i f i c gravity do. Since only atomic and electronic polarizations contribute at microwave frequencies, the effects of impurities on the d i e l e c t r i c constant do not dominate the effect of specific gravity.  4.2.5. E f f e c t of  Temperature  Three pieces of Hemlock having different s p e c i f i c g r a v i t i e s (0.39, 0.40, and 0.54) were soaked and p a r t i a l l y a i r dried. They were in turn frozen and measured using the electronic microwave bridge as they were warmed from -15°C to room temperature. The temperature of the test sample was monitored with a calibrated LM335 s o l i d state temperature transducer penetrating about 5 cm into the wood. Results are shown in Figs. 4.13 to 4.15. Both AA and A 0 increase as the temperature increases. The dependence of e ' and tan5 on temperature for one sample i s i l l u s t r a t e d in F i g . 4.16. For green pieces with moisture contents above the fiber saturation point, d i s c o n t i n u i t i e s in AA and A# were observed at  F i g . 4.13  Attenuation and phase s h i f t as a function o temperature for various moisture contents. Specific gravity=0.39. Hemlock: transverse p o l a r i z a t i o n .  F i g . 4.14  Attenuation and phase s h i f t as a function of temperature for various moisture contents. Specific gravity=0.40. Hemlock: transverse p o l a r i z a t i o n .  F i g . 4.15  Attenuation and phase s h i f t as a function of temperature for various moisture contents. Specific gravity=0.54. Hemlock: transverse p o l a r i z a t i o n .  3-|  c o vt c o  specific  53  gravity=0.40  2.5-  CJ  o TJ  <x> a>  b  Legend  1.50  mc=39.5%  » mc=17.9% * mc=12.3% 1  -15  -10  i  1  10  -5  15  20  Temperature ( ° C )  F i g . 4.16  D i e l e c t r i c constant as a f u n c t i o n of temperature f o r v a r i o u s moisture c o n t e n t s . S p e c i f i c gravity=0.40. Hemlock: t r a n s v e r s e p o l a r i z a t i o n .  54 approximately 0°C. This corresponds to a phase change from ice to l i q u i d water. For moisture contents below the f i b e r saturation point, there are no d i s c o n t i n u i t i e s at 0°C indicating that bound water does not undergo a phase change at the freezing point of water. This i s i l l u s t r a t e d by the steady continuous variation in AA and  A<f>  as the temperature  pure water. AA and  A<j>  passes through the freezing point of  appear to vary l i n e a r l y with  temperature  for various bound moisture contents. The slopes are preserved for d i f f e r e n t moisture contents and for d i f f e r e n t s p e c i f i c g r a v i t i e s . Therefore, values of measured AA and A0 at any temperature corrected to other  can be  temperatures.  4.2.6. Integrated Data Analysis The data can be presented to simultaneously show the two measured parameters and the two physical parameters. Plots of A# vs AA for various s p e c i f i c g r a v i t i e s are shown in Figs. H.1 to H.4 for transverse p o l a r i z a t i o n . Each s p e c i f i c gravity occupies a unique region on the p l o t . S i m i l a r l y , plots of A0 vs AA for various moisture contents are shown in Figs. H.5 to H.8. Each moisture content also occupies a unique region on the plot. Lines of constant s p e c i f i c g r a v i t i e s and constant moisture contents are combined and displayed in F i g . 4.17 for transverse polarization and in F i g . 4.18 for longitudinal polarization at room temperature.  450 HEMLOCK 400  frequency transverse thickness  350-  300-  250  200  150  100-1  50 0  2  4  6  8  10  12  14  16  18  20  22  24  Attenuation (dB) F i g . 4.17  Phase s h i f t as a f u n c t i o n of a t t e n u a t i o n f o r v a r i o u s s p e c i f i c g r a v i t i e s and moisture c o n t e n t s . Hemlock: t r a n s v e r s e p o l a r i z a t i o n . Room Temperature.  tn cn  100  | i i i i [ i i i i | i i i i | i i i i | i i i i | i i i i | i i i i [ i i i i | i i i  0  5  Fig. 4.18  10  15  20  25  30  35  Attenuation (dB)  40  i [  i i i i | i i i i  45  50  55  Phase shift as a function of attenuation for various s p e c i f i c g r a v i t i e s and moisture contents. Hemlock: longitudinal p o l a r i z a t i o n . Room Temperature,  cn  57 4.2.6.1. Grading  Technique  These results confirm Kharadly's[7] observation that the dependence of AA and A0 on s p e c i f i c gravity and moisture content is orderly. At a fixed temperature there i s a unique combination  and for either p o l a r i z a t i o n ,  of s p e c i f i c gravity and moisture  content corresponding to any measured combination of AA and A0. Thus when AA and A0 are measured, the estimates: mc=M(AA,A0)  and  sp gr=p(AA,A0)  can be obtained. A look-up table in microcomputer memory matches estimates of moisture content and s p e c i f i c gravity with each possible combination of measured attenuation and phase s h i f t at room temperature. The table i s stored  in the microcomputer's  memory and i s referred to when the bridge successfully balances. The e f f e c t of temperature  can be compensated for by scaling  AA and A0 to the c a l i b r a t i o n table temperature  p r i o r to look-up.  4.2.6.2. Accuracy The accuracy of the technique was studied by comparing minimum and maximum possible parameter estimates due to scatter with t h e i r actual values. From studying Figs. H.5 to H.8, the moisture content estimates are accurate to approximately ±3.0%. A similar accuracy i s obtained for longitudinal p o l a r i z a t i o n . Table 4.1 l i s t s the s p e c i f i c gravity results obtained for Hemlock with  Actual Specific Gravity  Low Estimate  0.33  High Estimate  Max Deviation  0.36  ±0.03  9.1  Max % Deviation  0.36  0.33  0.37  ±0.03  8.3  0.37  0.33  0.39  ±0.04  10.8  0.38  0.36  0.43  ±0.05  13.2  0.39  0.34  0.42  ±0.05  12.8  0.40  0.36  0.42  ±0.04  10.0  0.43  0.38  0.47  ±0.05  11.6  0.44  0.40  0.48  ±0.04  9.1  0.45  0.40  0.48  ±0.05  11.1  0.47  0.43  0.50  ±0.04  8.5  0.49  0.44  0.54  ±0.05  10.2  0.50  0.45  0.53  ±0.05  10.0  0.51  0.48  0.56  ±0.05  9.8  0.52  0.47  0.57  ±0.05  9.6  0.53  0.50  0.58  ±0.05  9.4  0.54  0.49  0.57  ±0.05  9.3  0.56  0.54  0.57  ±0.02  3.6  0.60  0.58  0.63  ±0.03  5.0  0.63  0.58  0.64  ±0.05  7.9  Table  4.1  Specific gravity estimation transverse p o l a r i z a t i o n .  range  of  Hemlock:  Actual Specific Gravity  Low Estimate  0.33  Max % Deviation  High Estimate  Max Deviation  0.36  ±0.03  9.1  0.36  0.33  0.39  ±0.03  8.3  0.37  0.36  0.44  ±0.07  18.9  0.38  0.33  0.41  ±0.05  13.2  0.39  0.36  0.44  ±0.05  12.8  0.40  0.36  0.44  ±0.04  10.0  0.41  0.37  0.43  ±0.04  9.8  0.43  0.36  0.47  ±0.07  16.3  0.44  0.38  0.52  ±0.08  18.2  0.45  0.38  0.51  ±0.07  15.6  0.47  0.41  0.52  ±0.06  12.8  0.48  0.41  0.53  ±0.07  14.6  0.49  0.44  0.53  ±0.05  10.2  0.50  0.43  0.54  ±0.07  14.0  0.51  0.43  0. 56  ±0.08  15.7  0.52  0.47  0.56  ±0.05  9.6  0.53  0.51  0.60  ±0.07  13.2  0.54  0.50  0.60  ±0.06  11.1  0.56  0.54  0.58  ±0.02  3.6  0.60  0.58  0.62  ±0.02  3.3  0.62  0.60  0.63  ±0.02  3.2  0.63  0.60  0.64  ±0.03  4.8  0.64  0.60  ±0.04  6.7  Table  4.2  Specific gravity estimation longitudinal polarization.  range  of  Hemlock:  60 transverse polarization and table 4.2  l i s t s results with  longitudinal p o l a r i z a t i o n . The transverse s p e c i f i c gravity estimates are assessed to be approximately accurate to ± 0 . 0 5 and the longitudinal estimates are accurate to approximately  ±0.08.  The greater accuracy obtainable with transverse polarization indicates that i t is more suitable for grading. This polarization is also preferred since transverse measurements require less dynamic range than longitudinal measurements.  4.3.  DOUGLAS FIR  DATA  Approximately  50 pieces of knot-free Douglas F i r were  e l e c t r o n i c a l l y measured using transverse p o l a r i z a t i o n . The microwave properties show similar variation to Hemlock as i l l u s t r a t e d in Figs. H.9  to H.11.  Figs. H.12  and H.13  show the  permittivity dependence. The relationships between AA and A0 for various constant s p e c i f i c g r a v i t i e s and moisture contents are shown in Figs. H.14 4.19  to H.19.  for room temperature,  These results, summarized in F i g .  are also suitable for a grading  algorithm. Their accuracies are studied by comparing the possible estimation ranges due to scatter for s p e c i f i c gravity and moisture content with their actual values. Specific gravity results are tabulated in Table 4.3 and are assessed to have an accuracy of ± 0 . 0 5 . The moisture content estimates are accurate to approximately ±3.0%  based on Figs. H.17  to  H.19.  0  2  4  6  8  10  12  14  16  18  20  Attenuation (dB) Fig. 4.19  Phase s h i f t as a function of attenuation for various s p e c i f i c g r a v i t i e s and moisture contents. Douglas F i r : transverse p o l a r i z a t i o n . Room Temperature.  Actual Specific G r a v i ty  Low Estimate  0.38  Max % Deviat ion  High Estimate  Max Deviation  0.40  ±0.02  5.3  0.41  0.38  0.43  ±0.03  7.3  0.42  0.38  0.45  ±0.04  9.5  0.43  0.42  0.45  ±0.02  4.7  0.44  0.42  0.48  ±0.04  9.1  0.45  0.42  0.47  ±0.03  6.7  0.47  0.46  0.51  ±0.04  8.5  0.48  0.47  0.52  ±0.04  8.3  0.49  0.44  0.51  ±0.05  10.2  0.51  0.49  0.56  ±0.05  9.8  0. 52  0.51  0.57  ±0.05  9.6  0.54  0.52  0.56  ±0.02  3.7  0. 55  0.54  0.57  ±0.02  3.6  0.57  0.56  0.58  ±0.01  1.8  0.58  0.57  0.61  ±0.03  5.2  0.61  0.58  ±0.03  4.9  Table  4.3  Specific gravity estimation transverse p o l a r i z a t i o n .  range  of  Douglas F i r :  5. CONCLUSIONS AND SUGGESTIONS FOR IMPROVEMENT  5.1. CONCLUSIONS  The objectives of this thesis have been met; in p a r t i c u l a r : 1.  A measurement system employing a microwave bridge c i r c u i t and the free-space technique was designed and tested which allows the rapid, non-contact measurement of p e r m i t t i v i t y . A microcomputer  performs automatic measurements by sampling the  balance signal and adjusting a l o g i c - c o n t r o l l e d attenuator and a l o g i c - c o n t r o l l e d phase s h i f t e r to balance the bridge. The p e r m i t t i v i t y estimates i s assessed to be accurate to ±10% for e ' but errors occur in tan5 estimates for low loss materials (tan5<0.05). These errors decrease when a lossy material such as wood i s measured. 2.  The d i e l e c t r i c properties of wood were measured to determine a dependence on i t s physical properties. The dependence of attenuation, phase s h i f t , d i e l e c t r i c constant, and loss tangent on s p e c i f i c gravity, moisture content, and temperature was observed for Hemlock and Douglas F i r .  3.  The grading relationship proposed by Kharadly[7] was confirmed and used to implement a grading technique. Detailed c a l i b r a t i o n curves were created for the two species to estimate s p e c i f i c gravity and moisture content from attenuation and phase s h i f t measurements. The microwave  63  64 properties  exhibit  so c o r r e c t i o n s grading 4.  The  a predictable  t o measured AA  wood a t d i f f e r e n t  accuracy  and  A0  can  with  be  temperature  applied  when  temperatures.  of t h e t e c h n i q u e  was  approximately  ±0.05 f o r s p e c i f i c  approximately  ±3.0%  using  behaviour  assessed  polarization,  the s p e c i f i c  approximately  ±0.08 and  be  g r a v i t y measurement  f o r bound m o i s t u r e  transverse polarization.  to  Using  content  and  measurement  longitudinal  gravity accuracy  approximately  i s assessed  ±3.0%  for  to  be  moisture  content.  The  measurement  environment. monitor  present  single and  can  THE  and  f o r use  in a  mill  could continuously  some m o d i f i c a t i o n s . The be made r u g g e d  to  system  withstand  system  MEASUREMENT SYSTEM requires approximately  reading for a s t a t i c  faster  balancing  analog/digital  convertor reduced  c o n v e r t e r can  ( i . e . 20 MHz)  ( i . e . 10 M S )  and  be  to o b t a i n a  microprocessor  used  high  a faster  c o n v e r s i o n time,  to approximately  50 ms  sample. A f a s t e r  time. With p r e s e n t l y a v a i l a b l e  microprocessors  be  with  suitable  conditions.  LIMITATIONS OF The  to operate  no moving p a r t s and  industrial  1.  I t i s simple  would be  microwave parameters  contains  5.2.  system  to reduce  the  speed  analog/digital  the b a l a n c e  10 msec. T h i s would  time  can  i n c r e a s e the  65 resolution for the scanning of moving materials. The balancing time can be further reduced by r e s t r i c t i n g the i n i t i a l scanning range when grading clear, knot-free wood because the s p e c i f i c gravity and moisture content would not vary greatly between scan points. A microwave knot detection instrument[7] could locate defects and warn the microprocessor to increase the i n i t i a l scanning 2.  The Varian X-13  range.  klystron in the present experimental  configuration can provide s u f f i c i e n t power (=* 300 mW CW) for accurate measurements up to 22 dB attenuation. At higher attenuations, the detector signal in the measuring channel i s s u f f i c i e n t l y small (=*-16 dBm)  that a balancing n u l l i s  d i f f i c u l t to accurately locate with the electronic system. The system has s u f f i c i e n t dynamic range to measure the attenuation and phase s h i f t for a l l s p e c i f i c g r a v i t i e s and bound moisture contents using transverse p o l a r i z a t i o n on 2-inch nominal dimension clear knot free wood. The klystron power source can be replaced by a s o l i d state source of higher power (^1 W CW)  to provide greater  frequency s t a b i l i t y , and the a b i l i t y to penetrate thicker, denser, or wetter samples. It would also provide the a b i l i t y to accurately measure longitudinal microwave parameters automatically for the entire range of t y p i c a l s p e c i f i c g r a v i t i e s and bound moisture contents. If measurements are  66 made using both polarizations, two separate estimates of s p e c i f i c gravity and moisture content can be obtained and averaged.  5.3.  FURTHER IMPROVEMENTS  Improvements can be made in both the experimental technique used to investigate wood d i e l e c t r i c properties and the instrumentation used: 1.  Moisture content gradients and high moisture pockets can form in the samples during a i r drying. At high average  moisture  contents (>18%), zones of free water may be present. Since the present experimental method measures average transmission parameters over a 10 cm X 10 cm zone, data scatter occurs at higher moisture contents. To investigate the d i e l e c t r i c behaviour of uniformly dried wood, each sample should be s l i g h t l y dried and sealed a i r tight to allow uniform moisture levels to be reached throughout  the sample prior to each  measurement. However, moisture gradients are representative of actual moisture conditions encountered  in i n d u s t r i a l k i l n  drying. 2.  The presence of v o l a t i l e extractives such as resins and o i l s in wood affect the moisture constant estimate. Oven drying causes these v o l a t i l e substances to evaporate and introduces errors in the oven dry measuring methods used. Alternative  67  methods for accurately measuring moisture content  such as  d i s t i l l a t i o n [ 1 ] can be used. No consideration i s given to the type of cut in the samples measured. A test sample can contain several zones of d i f f e r i n g s p e c i f i c g r a v i t i e s because s p e c i f i c gravity can vary throughout a tree. To investigate the exact dependence of d i e l e c t r i c properties on cut geometry, d i f f e r e n t cuts should be analyzed  separately. However, a l l cut types are  encountered in m i l l s and no on-line grading system  separates  wood into different cuts prior to grading. The e f f e c t s of 1 - 3 were minimized in t h i s investigation by performing tests on a large number of samples and studying the general trends in the results as various parameters were changed. The lookup tables that are created are based on average measurements over a large number of samples. This approach introduces scatter in the microwave measurements and leads to inaccuracies in parameter estimation but i s representative of actual i n d u s t r i a l conditions. The present  system measures stationary wood but a system  measuring moving wood would require a position monitoring sensor. D i g i t a l thickness and non-contact infrared temperature sensors are also required for an automated measurement system.  68 The  information obtained by the system can be used with other  instruments  of a proposed Advanced Grading System[7] which  measure slope of grain and detect knots with microwaves. A prediction algorithm can be developed to estimate  the  strength of lumber whose s p e c i f i c gravity, moisture content, slope of grain, and knot locations have been measured along i t s length. For the long term, the system can be miniaturized by using microstrip components to replace the waveguide. M i c r o s t r i p c i r c u i t r y i s inexpensive and can be accurately produced in quantity. This could result in low-cost portable compact devices suitable for on-site measurements.  REFERENCES [ 1] ASTM, "Annual Book of ASTM Standards", Volume 4.09 Wood, American Society for Testing and Materials, 1983. [ 2] C o l l i n , R.E., " F i e l d Theory of Guided Waves", McGraw-Hill, 1960. [ 3] Dyson, J.D., "The Measurement of Phase at UHF and Microwave Frequencies", IEEE Trans, on Microwave Theory and Techniques, V o l . MTT-14, No. 9, September, 1986, pp. 410-423. [ 4] James, W.L., and D.W. Hamill, "Dielectric Properties of Douglas Fir--Measured at Microwave Frequencies", Forest Products Journal, V o l . 15, No.2, pp. 51-56, February, 1965. [ 5] James, W.L., " D i e l e c t r i c Behaviour of Douglas F i r at Various Combinations of Temperature, Frequency, and Moisture Content", Forest Products Journal, Vol. 27, No. 6, pp. 44-48, June, 1977. [ 6] James, W.L., E.T. Choong, D.G. Arganbright, D.K. Doucet, M.R. Gorvad, W.L. Galligan, and W.T. Simpson, "Moisture Levels and Gradients in Commercial Softwood Dimension Lumber Shortly After Kiln-drying", Forest Products Journal, V o l . 34, No. 11/12, pp. 59-64, Nov./Dec, 1984. [ 7] Kharadly, M.M.Z., "Microwave Diagnostics for Stress-Rating of Dimension Lumber", F i f t h Nondestructive Testing of Wood Symposium, Sept. 9-11, 1985. Washington State University, Pullman, Washington, 1985.  69  70  [ 8] Kraszewski, A., "Microwave Instrumentation f o r M o i s t u r e Content Measurement",  J . of Microwave Power, 8(3/4), 1973.  [ 9] Kraszewski, A., "Microwave Aquametry — Microwave Power,  A Review", J . of  15(4), 1980.  [10] L i n , R.T., "Review of the D i e l e c t r i c  P r o p e r t i e s of Wood and  C e l l u l o s e " , F o r e s t Products J o u r n a l , V o l . 17, No. 7, pp. 61-66, J u l y , 1967. [11] Magid, M., " P r e c i s i o n Microwave Phase S h i f t  Measurements",  IRE T r a n s a c t i o n s on Instrumentation, V o l . 1-7, pp 321-331, December 1958. [12] Panshin, A.J., and de Zeeuw, C. Textbook of Wood  Technology,  Fourth E d i t i o n . McGraw-Hill, 1980. [13] Peterson, R.W.,  "The D i e l e c t r i c P r o p e r t i e s of Wood", F o r e s t  Products L a b o r a t o r i e s of Canada T e c h n i c a l Note No. 16, C a t . No. R57-16, 1960. [14] Purslow,  D.F., "The Use of a Microwave Moisture Meter f o r  Studying Moisture Changes i n Timber", J . of the I n s t i t u t e of Wood Science, V o l . 5(4) #28, pp. 40-46, 1971. [15] Redheffer, R.M., Techniques Montgomery,  "The Measurement  of D i e l e c t r i c  Constants",  of Microwave Measurements, Ch. 10, C G . Ed. New York: McGraw-Hill, 1947.  [16] Roberts, S, and von H i p p e l , A., "A New Method f o r Measuring D i e l e c t r i c Constant and Loss i n the Range of Centimeter Waves", J . of A p p l i e d P h y s i c s , V o l . 17, pp. 610-616, 1946.  July,  71 [17] Skaar, C., "The D i e l e c t r i c Properties of Wood at Several Radio Frequencies", New York State College of Forestry at Syracuse University Technical Publication No. 69, 1948. [18] Stamm, A.J.,"Wood and Cellulose Science", The Ronald Press Co., New York, 1964. [19] Tinga, W.R., " D i e l e c t r i c Properties of Douglas F i r at 2.45 GHz", J . of Microwave Power., Vol.4, No. 3, p.162, 1969. [20] T i u r i , M, Jokela, K, and H e i k k i l a , S, "Microwave Instrumentation for Accurate Moisture and Density Measurement of Timber", J . of Microwave Power, 15(4), Dec. 1980. [21] Wangaard, F.F., "The Mechanical Properties of Wood", John Wiley & Sons, Inc., New York, 1950. [22] Wood Structures, A design guide and commentary. Compiled by ASCE Structural D i v i s i o n . Published by American Society of C i v i l Engineers, 1975. [23] Yavorsky, J.M., "A Review of E l e c t r i c a l Properties of Wood", New York State College of Forestry at Syracuse University Technical Publication No. 73, 1951. [24] Yen, Y.H., "Microwave Electromagnetic Nondestructive Testing of Wood in Real-Time", PhD Thesis, The University of Wisconson-Madison, 1981.  APPENDIX A DERIVATION OF FREE SPACE TRANSMISSION COEFFICIENT  The relationship between electromagnetic waves at an interface between two semi-infinite media i s obtained from a wave transmission matrix analysis[2]:  medium 1 c1  medium 2 c 2  b,  b,  A ! j-  1  A 1 1 A,2  C  2  A  b  2  2  1 A 2 2  AI 2" P1  T, A ,=R, 2  2  A2 2 T i"RiR; =  2  where: T =transmission y2  c o e f f i c i e n t from medium 1 to medium 2  T 1 t r a n s m i s s i o n c o e f f i c i e n t from medium 2 to medium 1 2  72  73 R,=reflection c o e f f i c i e n t in medium 1 at interface R =reflection c o e f f i c i e n t in medium 2 at interface 2  If z=impedance of medium 2 normalized to impedance of medium 1, then the relationship i s :  ci  z+1  z-1  c2  b,  z-1  z+1  b  2z 2z  2z 2z  2  For a d i e l e c t r i c slab of width 1 and complex impedance z, the wave transmission matrix i s obtained by cascading three matrices corresponding to two interfaces separated by a medium of complex impedance z and complex propagation constant 7: //////////// medium 1 / medium 2 / //////////// c, //////////// > //////////// //////////// //////////// <  b,  medium 3 c  3  ////////////  //////////// b //////////// < //////////// ////////////  3  >  74 C1  z+1 2z  z-1 2z  b,  z-1 2z  z+1 2z  0  0  z+1 2  -(z-1) 2  e- 7 l  (z-1)  (z+1)  which g i v e s :  C1  sinh7l(z +1)+cosh7l 2z  b,  sinh7l(z -1) 2z  2  2  -sinh7l(z +1)+cosh7l 2z  2  Therefore,  sinh7l(1-z ) 2z 2  the transmission c o e f f i c i e n t  is:  T  1 3  =  1 = A,,  4ze - 7 l (Z+1)2-( -I)2 " Z  e  2 7 1  from  medium  c  3  b  3  1 t o medium 3  APPENDIX B P E R M I T T I V I T Y CALCULATION  FROM FREE SPACE MEASUREMENTS  The accompanying Fortran program calculates the complex p e r m i t t i v i t y from microwave bridge measurements. The material i s assumed to have a uniform d i e l e c t r i c constant throughout i t s volume. The effects of interface r e f l e c t i o n s are incorporated into the complex transmission c o e f f i c i e n t . A f i r s t order approximation  to e' and tan8 i s made using  Eqs. 11 and 12. These serve as i n i t i a l guesses to the exact solution of Eq. 8. A grid i s formed in the e' and tan5 axes. The transmission c o e f f i c i e n t s at eight neighbouring  points are  evaluated using Eq. 8 and the point whose transmission c o e f f i c i e n t deviation from the measured value i s minimum serves as the new guess point. This process i s repeated u n t i l the updated guess point i s unchanged between successive i t e r a t i o n s . -2 The value of e' i s accurate to ±10  and tan5 i s accurate to  ±10 . - 3  The complex propagation constant of a plane wave in the d i e l e c t r i c medium i s :  7 = J 0 r V [ e ' (1-Jtan6)3  75  76 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84  C C  C C C C C C  THIS PROGRAM INPUTS THE EXPERIMENTAL ATTENUATION AND PHASE MEASUREMENTS AND COMPUTES THE CORRESPONDING COMPLEX PERMITTIVITY COMMON / B L K t/ WIDTH,BETAF WAVEL'O.029426 PI'S.1415926 WIDTH-0.01300 BETAF = 2 . 0 * P I / W A V E L INPUT EXPERIMENTAL DATA A T T F S P ' F R E E SPACE ATTENUATION PHASP'FREE SPACE PHASE SHIFT ATTWO'WOOD ATTENUATION ; PHAWD'WOOD  R E A D ( 5 , 4 9 9 ) WIDTH R E A D ( 5 . 5 0 0 ) ATTFSP R E A D ( S . 5 1 0 ) PHASP R E A 0 ( 5 , 5 0 O ) ATTWD R E A 0 ( 5 . 5 1 O ) PHAWD 499 FORMAT( F 10. 5) 500 F0RMAT(F5.2) 510 FORMAT(F5.1) C ECHO INPUT W R I T E ( 6 , 7 9 9 ) WIDTH W R I T E ( 6 . 8 0 0 ) ATTFSP W R I T E ( 6 . 8 1 0 ) PHASP W R I T E ( 6 , 8 2 0 ) ATTWD W R I T E ( 6 . 8 3 0 ) PHAWD C 799 F0RMAT( 'SAMPLE THICKNESS ' . F 1 1 . 7 . ' CM') 800 F O R M A T * ' F R E E - S P A C E ATTENUATION BALANCE' ' , F 5 . 2 , ' DB') 810 FORMAT(' FREE-SPACE PHASE BALANCE = ' . F 5 . 1, ' DEGREES') 820 FORMAT(' WOOD ATTENUATION 8ALANCE- ' . F 5 . 1 . ' DEGREES') 830 FORMATC WOOD PHASE 8ALANCE" ' . F 5 . 1 . ' DEGREES') DELATT=EXP(- 1 . 0 * ( A T T W D - A T T F S P ) / 2 0 . O ' A L O G I 1 0 . 0 ) ) DELWD»ATTWD-ATTFSP C DELPH'PHAWD-PHASP C OUTPUT RELEVANT CALCULATIONAL DATA WRITE(6,840) DELWD.DELATT 840 FORMAT(' WOOD ATTENUATION' ' , F 5 . 2 , ' DB ' , ' OR ' . F 5 . 2 ) W R I T E ( 6 , 8 5 0 ) DELPH 850 FORMAT(' ACTUAL PHASE SHIFT = ' , F 6 . 1 . ' DEGREES') C CONVERSION TO RADIANS DELPH'DELPH/180.0»PI C OBTAIN SOLUTION CALL S O L V E ( D E L A T T . D E L P H . E 1 . T A N D E L ) WRITE(6,550) 550 F O R M A T ! / / . ' * » » » EXECUTION TERMINATED « • * • ' ) STOP END C C A SUBROUTINE TO DETERMINE THE EXACT VALUE OF E ' AND LOSS TANGENT C FROM ATTENUATION ANO PHASE SHIFT MEASUREMENTS C SUBROUTINE S O L V E ( D E L A T T , D E L P H , E 1 , T A N D E L ) COMPLEX TRANS COMPLEX TMAT(5) DIMENSION EPS 1 ( 5 ) . T A N D ( 5 ) . D M A G ( 5 ) . D A N G ( 5 ) COMMON / B L K 1 / WIDTH,BETAF MAXNUM'100 AIRPH'BETAF'WIDTH ARGANG'DELPH+AIRPH COSVAL'COS(ARGANG) SINVAL = SIN ( ARGANG) C GET INITIAL APPROXIMATION CALL G U E S S I D E L A T T , D E L P H , E 1 . T A N D E L ) C ECHO INITIAL APPROXIMATION WRITE(6,860) E1,TANDEL 860 F O R M A T ( / / . ' A P P R O X E1» ' . F 8 . 4 , ' APPROX TANDEL" ' . F S . 4 . / > C CALC EXACT VALUE BY MINIMIZATION OF DEVIATIONS AT NEIGHBOURING C POINTS. NEGLECT DEVIATION ANGLE MEASUREMENTS C ASSIGNING VALUES FOR E l AND LOSS TANGENT AT NEIGHBOURING POINTS NCOUNT'O 90 CONTINUE EPS 1(1)"E1 TAND(1)-TANDEL EPS1(2)'E1+0.001 TANO(2)'TANOEL EPS1(3)"E1 TAN0(3)-TANOEL*O.O01 EPS1(4)'E1-0.001 TAND(4)'TANDEL EPS1(5)'E1 TAND(5)'TANDEL-0.001 3  '  PHASE SHIFT  85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 1 10 111 112 113 114 115 116 117 118 119 120 121 '22 123 124 125 126 127 128 129 130 131 132 '33 134 135 '36 137 '38 139 140 141 '42 143 144 145 146 147 '48 149 '50 '51 152 153 154 155 156 157 158 159 160 161 162 163 '64 '65 166 '67 168 '69 170 '71 172 173 174  C  CALCULATION OF TRANSMISSION COEFFICIENTS FOR NEIGHBOURING POINTS DO 100 ICNT*1.5 PERM1-EPSKICNT) TANN'TANDtICNT) C EVALUATE COMPLEX TRANSMISSION COEFFICIENT TMAT(ICNT)"TRANS(PERM 1.TANN) TR REAL(TMAT(ICNT)) TI»AIMAG(TMAT(ICNT)) C EVALUATION OF REAL ANO IMAGINARY COMPONENT DEVIATIONS HOLDR=TR-DELATT*COSVAL C NEGATIVE SIN TERM DUE TO THE E X P ( - J « B ' L ) HOLDI TI+DELATT' SINVAL IF (ICNT.NE.1) GOTO 99 WRITE(6.690) NCOUNT,PERM1,TANN.TR.TI,HOLDR.HOLDI 690 F0RMAT(I4.2X.F7.3.2X.F7.3,3X,F10.6.3X.F10.6.3X.F11 7.3X.F11.7) 99 CONTINUE C EVALUATION OF THE DEVIATION MAGNITUDE DMAG(ICNT)=SQRT(H0LDR*H0LDR HOLDI*HOLDI) C EVALUATION OF THE DEVIATION ANGLE DANG(ICNT)=ANGTAN(HOLDR.HOLDI) 100 CONTINUE C SELECT POINT HAVING MINIMUM DEVIATION C TEMPORARILY ASSUME CENTRAL POINT ( I V A L ) HAS MINIMUM DEVIATION RMIN-OMAGd) IVAL-1 DO 110 JCNT=1.5 IF (OMAG(JCNT) LE RMIN) IVAL-vJCNT 110 CONTINUE IF (IVAL.EQ.1) GOTO 200 NCOUNT-NCOUNT+1 E1-EPS1(IVAL) TANDEL-TANO(IVAL) IF (NCOUNT.LE.MAXNUM) GOTO 90 WRITE(6,700) 700 FORMAT('MAXIMUM NUMBER OF ITERATIONS EXCEEDED') 200 CONTINUE WRITE(6,710) EPS 1( 1),TAND( 1) 7 10 FORMAT*//,'VALUE OF E1=',F9.5.3X,'VALUE OF LOSS TANGENT*' F9 5) WRITE(6,720) DMAGI1),DANG(1) 720 FORMAT)/, MAGNITUDE DEVIAT 10N=' .F9.5, ' ANGULAR DEVIATION-' F9 5) WRITE(6,730) 730 FORMAT!'SUCCESSFUL SOLUTION --> MAGNITUDE DEVIATION MINIMIZED') RETURN END tt  n  +  C C  A PROGRAM TO FINO THE FIRST ORDER APPROXIMATION  TO E' ANO  E' '  SUBROUTINE GUESS(OELATT.DELPH.E1.TANDEL) COMMON /BLK1/ WIDTH,BETAF RTE 1 * 1 . 0+DELPH/( BETAF * WIDTH ) E1=RTE1*RTE1 ARG1*(DELATT*RTE 1 *( 1.O/RTE1+1.0)*«2. )/4.0 ARG2-(-1 0 * B E T A F * R T E 1 « W I D T H ) / 2 . 0 TANDEL=ALOG(ARG1)/ARG2 RETURN END C C C  C C C C  A FUNCTION TO EVALUATE THE ARCTANGENT OF A SPECIFIED GIVEN ITS OPPOSITE AND ADJACENT SIDES  ANGLE  FUNCTION ANGTAN(X.Y) PI>3.14159 ANGLE FOUND IN QUADRANT 1 IF((X.GE.0).AND.(Y G E . 0 ) ) ANGLE=ATAN2(Y.X) ANGLE FOUNO IN OUADRANT 2 IF<(X LE.0).AND.(Y G E . 0 ) ) ANGLE=ATAN2(Y,X)+PI ANGLE FOUND IN OUADRANT 3 I F ( ( X . L E . O ) . A N D . ( Y . L E . 0 ) ) ANGLE-ATAN2(Y.X)+PI ANGLE FOUND IN OUADRANT 4 I F ( ( X GE.0).ANO.(Y.LE.0)) ANGLE ATAN2(Y,X)+2.0*PI CONVERSION TO DEGREES AND RETURN ANGTAN-ANGLE/PI*180.0 RETURN END 3  C  C C C  CALCULATE COMPLEX TRANS COEFF AS A FUNCTION OF E' AND  LOSS  COMPLEX FUNCTION TRANS(E1,TANDEL) COMPLEX CMPLX.CEXP.CSORT COMPLEX CNUM.COEN.Z.EPS.GAMMA COMMON /BLK1/ WIDTH,BETAF E2-E1'TANDEL E P S » C M P L X ( E 1 , - 1 0*E2) Z-1 0/CSORT(EPS) GAMMA*(0,1.0)*BETAF/Z CDENM (Z-M 0 ) " 2 ) - < (Z-1 . O) • «2 ) »CEXP(-2 . O'GAMMA* WIDTH ) CNUM-4 ,0'Z"CEXP( - 1 . O'GAMMA'WIDTH) TRANS-CNUM/COEN RETURN END  TAN  APPENDIX C DATA ACQUISITION  CIRCUITRY  The data acquisition board consists of a variable gain amplifier and an A/D converter. The dc output of the c r y s t a l detector has a nonlinear response c h a r a c t e r i s t i c . Signal conditioning i s required for input to the A/D converter. High resolution i s required for d i g i t i z a t i n g low signal levels in the v i c i n i t y of a n u l l . Lower resolution i s adequate for higher signal levels since accuracy  i s not necessary away from a n u l l  point. A two-stage amplifier c i r c u i t was b u i l t with both stages operating for low signal levels to provide high gain (250X) and only a single stage operating to provide the gain (5X) for high signal l e v e l s . A comparator monitors the signal l e v e l to select the appropriate gain. Input signal range is indicated to the microcomputer via a status b i t . The low signal output  i s fed into  input channel 0 and the high signal output i s fed into input channel  1 of the analog-to-digital converter. A 4066 switch  l i m i t s both signals to a 5V maximum to protect the A/D  converter  input stage. A National Semiconductor ADC  0808 A/D converter  conversion time) i s driven by a 4.0 MHz  (100  MS  clock signal and a 5V  reference voltage i s provided by an AD584KH precision voltage regulator. The A/D converter has a ten segment LED bar graph attached to the 8-bit data output l i n e s to provide visual 78  79 indication of signal levels for v e r i f i c a t i o n purposes during testing. A single LED segment indicates the signal range. A 200 ns pulse, generated by a DM7412, i s fed into the start conversion input of the A/D converter. Upon completion  of conversion the A/D  converter emits an EOC pulse to toggle a D f l i p - f l o p . The data acquisition board i s shown in Figs. C.1 and C.2.  Operation The microprocessor  reads the status of the signal l e v e l  indicator b i t to select the appropriate A/D channel. A start conversion signal i s fed to the DM7412 to i n i t i a t e conversion. Upon completion  of conversion, the EOC pulse toggles the f l i p  flop. The microprocessor  continuously p o l l s the f l i p - f l o p status  and reads the A/D converter data when conversion i s complete.  +15V  } 2 0 K Balance  lA/VV,  VIN  VREF  Fig. C . 1  Schematic diagram of amplifier  circuit.  CO  o  DM7412 IN INO  INO  INI  £7 INI +3V-  vcc  QE  START VCC ALE ee ECC 7 3 lCLKlD • 5 V i i IPHC ICLTf -TTlGND 1Q  GND  vcc  c  c  >4 iY3 5; 1A3 1A1 (si 1Y1 18  74LS74  3 ADD C8 84 ADD Bes ADD A  1A4 GND  12 1Y4 v  eo -•3V  CO  Y3 J 2A3 19 7 3Y8 rX. 2A2 13 9 2A1 2  CQNV EDC CLR EDC RDY ADD C ADD B ADD A  100 -VW 470  AMr 470  oo  IT)  L  P <  VCC  CD4049 LF356N  GND  DCIS  CD4049  riCIA  GND  SCALE  •5V  Fig. C.2  Schematic diagram of analog/digital converter c i r c u i t .  APPENDIX D INTERFACE  CIRCUITRY  Interface board #1 i s configured to decode address  lines  A0-A10. A 74LS138 3-to-8 l i n e decoder decodes address l i n e s A2, A3, and A5 to enable selection of an appropriate I/O port. The decoder selects two Intel 8255 programmable peripheral interfaces on interface board #2. Lines AO and A1 select the 8255's mode of operation. Schematics of the interface boards are shown in F i g s . D.1 and D.2. The f i r s t 8255 i s programmed to output data bytes to ports A and B. Port A controls the d i g i t a l l y programmable phase s h i f t e r while port B controls the d i g i t a l l y programmable attenuator. Port C remains unused. The second 8255 i s programmed to read and write with the data acquisition board. Port A inputs the data byte produced by the A/D converter while port B writes to the A/D converter to select the appropriate analog input channel. 8255 #1 i s configured as two output ports by issuing an OUT command to port 643 with 128 as a data byte for the chip programming mode. 8255 #2 i s configured as a single input port, a single output port, and a hybrid port by writing an OUT command to port 82  647 with 152 as data for the chip programming mode.  Port Assignments 640 (output mode - eight b i t s ) : phase s h i f t e r control 641 (output mode - eight b i t s ) : attenuator control 642 (unused) 643 8255#1 programming port 644 (input mode - eight b i t s ) : A/D converter data 645 (output mode - eight b i t s ) : A/D converter address selector 646A (output mode): UPPER: PC7 unused PC6 unused PC5 scale indicator PC4 EOC ready 646B (input mode): signal l e v e l indicator, EOC ready PC3 unused PC2 unused PC1 clear EOC PCO start conversion 647 8255#2 programming port  IBM P C j r  I/D channel  connector  arises  8 * * 8 * 8 6 5  8  2 a  <  74LS245  g528S2g|oi  •  "5k  < 1  e55a5?  74LS541 ro 2 5  S *  » ?  53  74LS541*  5  R 3  •  <  -< n to »  74LS138  74LS04  74LS30  SR < x o  s  "H  26-pin  connector  GND Al A2 A3 A4 AS A6 A7 A8  •12V-12V-+SV VCC 20 10 Yl 17 Y2 Y3 It Y4 13 Y5 14 Y6 U Y7 It Y8 U  GND Al A2 A3 A4 AS At> A7 A8  VCC Yl Y2 Y3 Y4 Y5 Y6 Y7 Y8  jJiT  •sv-  Fig. D.2  0.2S dB 0J dB 1.0 dB •9 2.0 dB 4.0 dB 10 8.0 dB U 164 dB It 32.0 dB 13 • i t v - 14 •V -V -urvGND 4 7  Schematic diagram of inte  GND 1Y4 1Y3 1Y2 1Y1 2Y1 2Y2 2Y3 2Y4  VCC 1A4 ^ 1A3 CM 1A2 CO 1A1 * J 2A1 ^ 2A2 2A3 17 2A4  to d i g i t a l attenuator  CONV EOC CLR EOC ROY SCALE ADD C ADD B ADD A  3»"  PAO PA1 PAS PA3 PA4 PAS PA6 PA7  to d i g i t a l phase shi fter  -•3 V 17 14 19 14 13 IC U  GND VCC 10 1A1 IY1 2A2 2Y2 2Y1 ^ 2A1 19 2Y3 CO it J 2A3 1A4 1Y4 14 1A3 1Y3 1A2 G 1Y2  LO  IO 00 01 CM oo 02 D3 D4 05 06 D7 VCC GND  •V -V 19 •SV I. 4* Ut 2.8* 3 3.6* 13 II.3* 11 22.5* « 43.0* • 90.0' 7 180.0* GND  -•SV  ace board #2.  CD  cn  APPENDIX E BRIDGE BALANCING PROGRAM  The accompanying  8088 assembly language program locates  settings for the d i g i t a l l y programmable attenuator and phase s h i f t e r that produce a n u l l signal at the detector. The attenuator i s i n i t i a l l y set at 0 dB as the phase s h i f t e r is scanned from 0° to 360  0  in 10° steps. The detector signal i s  sampled after each new setting. The phase s h i f t setting  that  produces the minimum detector level i s located and the device i s set at that value. The attenuator i s then scanned from 0 dB to 21 dB in 1 dB steps to locate the setting that produces a minimum signal l e v e l . The attenuator i s then set at that value (A,). The phase shifter i s scanned from 0,-10° to #,+10° and fixed at the minimum signal level setting. The attenuator in turn i s scanned from A,-2 dB to A,+2 dB and fixed at the minimum signal level setting. This i t e r a t i v e process i s repeated u n t i l the attenuator and phase s h i f t e r settings remain unchanged between successive i t e r a t i o n s . The total phase s h i f t and attenuation in the system are the sum of values from the c a l i b r a t i o n data (Appendix F ) .  86  The  IBM P e r s o n a l Computer A s s e m b l e r 09-11-87  PAGE  1 -1  87 1  page,132  2  B A L L ASH  3  T h i s a s s e m b l y language r o u t i n e b a l a n c e s  4  b r i d g e c r c u i t by a d j u s t i n g t h e a t t e n u a t i o n and phase  a microwave  5  i n one b r a n c h t o match t h e a t t e n u a t i o n and phase i n t h e  6  other  branch.  7 Balance  8  i s o b t a i n e d when t h e sampled s i g n a l  i s minimized.  9 Algorithm:  10 11  a)  A U phase v a l u e s f r o m 0 t o 360 d e g r e e s a r e o u t p u t  b)  A t t e n u a t i o n v a l u e s f r o m 0 t o 20 dB a r e o u t p u t t o  to determine t h e f i r s t  12 13  determine the f i r s t  14  order  order  approximation.  approximation.  15  c)  Phase v a l u e i s r e f i n e d  16  d)  Attenuation value i s refined  17  e)  Phase and a t t e n u a t i o n a r e c o n t i n u o u s l y r e f i n e d  18  constant  until  (within tolerance) values are obtained.  19  JAMES LOO  20  August 1, 1987  21  22  constants  definition  23  = 0280  phport  e q u 640  phase s h i f t e r  24  = 0281  attport  equ 641  attenuator port  25  = 0283  portl  e q u 643  8255 #1 i n i t i a l i z a t i o n p o r t  location  26  = 0287  port2  e q u 647  8255 #2 i n i t i a l i z a t i o n p o r t  location  27  = 001E  maxit  e q u 30  maximum b a l a n c e  28  = 0071  stop_key  e q u 113  q key = q u i t  port  iterations  29  = 0072  r e s t _ k e y e q u 114  r key = r e s t a r t  30  = 000D  cr  equ 13  carriage return character  31  = 000A  If  e q u 10  l i n e feed  0000  data  allowed  character  32 33 34 35  r  36  I  37  0000  38  0002  39  0003  40  0004  segment memory a l l o c a t i o n f o r  variables  ???? ?? ??  port  dw ?  ; p o r t f o r BALANCE  I ova I  db ?  ;low t r i a l  hival  db ?  ;high t r i a l  step  db ?  .•increment  at t e n  db ?  /balanced  attenuation  phase  db ?  /balanced  phase  balval  db ?  / v a l u e o b t a i n e d by BALANCE  attold  db ?  /old  a t t e n (from previous  balance)  phold  db ?  /old  phase ( f r o m p r e v i o u s  balance)  attdif  db ?  / d i f f between new and o l d a t t  phdif  db ?  / d i f f between new and o l d phase  41  0005  42  0006  43  0007  44  0008  45  0009  46  000A  47  000B  48 49  o ooc 000D  50  000F  ?? ?? ?? ?? ?? ?? ?? ?? ?? ???? ??  51 52  0010  000A  base  0012  attval  53  0014  ???? ????  phval  v a l u e f o r BALANCE v a l u e f o r BALANCE f o r BALANCE  flag  db ?  / f l a g v a r i a b l e f o r BALANCE  dat  dw ?  / v a l u e sampled by A/D c o n v e r t e r  balcnt  db ?  /count o f b a l a n c i n g  dw 10  /base t o p r i n t numbers i n  dw ?  / f i n a l atten value after  dw ?  / f i n a l phase v a l u e a f t e r b a l a n c i n g  iterations balancing  The IBM Personal Computer Assembler 09-11-87  PAGE  1-2  88 54  0016  ??  maxsamp db ?  ;max acceptable EOC waiting cycles  55 56 57 58 59 60  0017  ??  adcount  ;number of A/0 samples obtained  61 62 63 64 65 66  ; output messages to display 0018  003B  67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106  db ?  0067  007B  008B  009B  00AB  00C4  OODD  00F4  0111  00 OA 4A 61 60 65 73 20 4C 6F 6F 2C 20 77 61 6F OD  4D 61 62 72 OA  69 76 6F 79 55  44 65 70 60 65 6E 66 20 45 74 72 69 20 65 6E 65 65 72 20 24 OD OA OA 65 72 20 60 61 6E 20 24 00 OA OA 74 61 72 2E 3F 20 OD OA 41 6E 75 61 6E 3D 20 00 OA 50 65 20 53 74 3D 20 OD OA OA 72 61 74 73 20 72 69 72 65 24 00 OA 41 73 61 60 73 20 72 69 72 65 24 OD OA 4E 61 6C 61 20 70 6F 62 6C 65 OD OA 41 73 61 6D 20 63 6F 20 65 78 64 65 64  63 65 72 20 42  72 20 61 24 43  startjness  db cr,If,'James Loo, Microwave Laboratory $'  6F 4C 74 20  db cr,tf,'UBC Department of Electrical engineering $'  61 72 74 74 20 6F 6C 65 63 63 61 6C 67 69 6E 69 6E 67 45 6E 74 43 6F 60 64 20 3F  prompt  db cr,If,If,'Enter Command ? $'  52 74 24 74 74 24 68 68 24 49 69 65 64  65 73 2E 2E  promptr  db c r , I f , I f , ' R e s t a r t . . . ? $'  74 65 69 6F  attmess  db cr,If,'Attenuation= $'  61 73 69 66  phmess  db cr,If,'Phase Shift= $'  74 6F 71 3D  65 6E 75 20  itmess  db cr,If,If,'Iterations  44 6C 71 3D  20 65 75 20  admess  db c r , l f , ' A / D samples required= $'  6F 20 6E 63 73 73 20 24 2F 44 70 6C 75 6E 63 65 20 24  62 65 69  nomess  db c r , l f , ' N o balance possible $'  20  nobalmess db c r , l f , ' A / D sample count exceeded $'  2F 70 65 64  required= $'  65 74 65  00 OA OA 2A 2A 2A 2A 20 45 78 65 63  stopmess db cr,If,If,'**** Execution Terminated **** $'  The IBM Personal Computer Assembler 09-11-87  107 108 109 110 111  75 54 61 2A  74 65 74 2A  69 72 65 2A  6F 60 64 20  PAGE  1-3  89  6E 20 69 6E 20 2A 24  112 113  ; calibration values for ; General Microwave Model 7728 phase shifter (in degrees)  114 115 116  ; tabulated values are 10X actual value. ;  117 118 119 120 121 122 123 124 125  0134  0000 000F 0014 001E 0028 013E 0032 003C 0041 0050 005A  2,  3,  4  dw 0050, 0060, 0065, 0080, 0090  ; 5,  6,  7,  8,  9  ; 10,  0152  0096 00A5 00AF 00BE  dw 0150, 0165, 0175, 0190, 0205  ; 15, 16,  00CD 015C 0007 00E1 00EB 00FA  dw 0215, 0225, 0235, 0250, 0265  ; 20, 21, 22, 23, 24  dw 0275, 0290, 0305, 0325, 0330  ; 25, 26, 27, 28, 29  0 1 6 8 0177 0 1 8 6  dw 0345, 0360, 0375, 0390, 0405  ; 30, 31, 32, 33, 34  01BD 01C7 01D6  dw 0420, 0445, 0455, 0470, 0490  ; 35, 36, 37, 38, 39  0208 021C 0226  dw 0505, 0520, 0540, 0550, 0570  ; 40, 41, 42, 43, 44  025D 026C 027B  dw 0585, 0605, 0620, 0635, 0655  ; 45, 46, 47, 48, 49  02AD 02C1 02CB  dw 0665, 0685, 0705, 0715, 0735  ; 50, 51, 52, 53, 54  02FD 030C 0318  dw 0745, 0765, 0780, 0795, 0810  ; 55, 56, 57, 58, 59  0348 035C 0366  dw 0830, 0840, 0860, 0870, 0890  ; 60, 61, 62, 63, 64  0393 03A7 03BB  dw 0910, 0915, 0935, 0955, 0960  ; 65, 66, 67, 68, 69  03E3 03F2 0406  dw 0980, 0995, 1010, 1030, 1040  ; 70, 71, 72, 73, 74  0433 043D 0451  dw 1055, 1075, 1085, 1105, 1115  ; 75, 76, 77,  047E 0480 04A1  dw 1135, 1150, 1165, 1185, 1205  ; 80, 81, 82, 83, 84  04CE 04E2 04F1  dw 1215, 1230, 1250, 1265, 1285  ; 85, 86, 87, 88, 89  01E8 050F 0523 0532 0546 0550 01F2 0564 0573 0582 0596  dw 1295, 1315, 1330, 1350, 1360  ; 90, 91, 92, 93, 94  dw 1380, 1395, 1410, 1430, 1445  ; 95, 96, 97, 98, 99  1  0  9  129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151  0170  156  1,  dw 0100, 0110, 0125, 0140, 0145  0166 0113 0122 0131 0145 014A  153 154 155  ; 0,  0064 006E 007D 008C  127 128  152  ph_phcal dw 0000, 0015, 0020, 0030, 0040  0148  0 0 9 1  126 0  phase shifter settings  017A 0184 018E 0198 01A2 01AC 01B6 01C0 01CA 0104 01DE  0159 0195 01A4 01EA 01F9 023A 0249 028F 0299 02DF 02E9 032A 033E 037A 038E 03C0 03D4 0410 041F 045B 046F 04B5 04BF  0505  11, 12, 17,  13, 14 18, 19  78, 79  05A5  157  01FC 05AF 05B9 05C8 0507  dw 1455, 1465, 1480, 1495, 1510  ;100, 101, 102, 103, 104  158 159  05E6 0206 05F5 05FF 060E 0618  dw 1525, 1535, 1550, 1560, 1570  ;105, 106, 107, 108, 109  The IBM Personal Computer Assembler 09-11-87  PAGE  1-4  90 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212  0622 0631 0640 064F 0659 0663 0672 0677 0686 0690 069A 06A4 06B3 06BD 06C7 0601  dw 1585, 1600, 1615, 1625, 1635  ; 110, 111, 112, 113, 114  dw 1650, 1655, 1670, 1680, 1690  ;115, 116, 117. 118, 119  dw 1700, 1715, 1725, 1735, 1745  ;120, 121, 122, 123, 124  0608 06EA 06EF 06FE 0700 0238 0717 0721 0726 0735 073F 0242 0749 0758 0767 076C 077B  dw 1755, 1770, 1775, 1790, 1805  ;125, 126, 127. 128, 129  dw 1815, 1825, 1830, 1845, 1855  ;130, 131, 132, 133, 134  dw 1865, 1880, 1895, 1900, 1915  ;135, 136, 137, 138, 139  024C 0780 078F 079E 07A3  dw 1920, 1935, 1950, 1955, 1970  ;140, 141, 142, 143, 144  07B2 07BC 07CB 070A 07E4  dw 1980, 1995, 2010, 2020, 2035  ;145, 146, 147, 148, 149  082 F  dw 2050, 2065, 2080, 2095, 2110  ;150, 151, 152, 153, 154  0875  dw 2125, 2135, 2150, 2165, 2185  ; 155. 156, 157, 158, 159  08CA  dw 2200, 2215, 2230, 2250, 2265  ;160, 161, 162, 163, 164  091F  dw 2280, 2300, 2315, 2335, 2355  ;165, 166, 167, 168, 169  0974  dw 2370, 2390, 2400, 2420, 2440  ;170, 171, 172, 173, 174  09CE  dw 2460, 2480, 2495, 2510, 2530  ;175, 176, 177. 178, 179  0A1E  dw 2540, 2560, 2580, 2590, 2610  ;180, 181, 182, 183, 184  0A69  dw 2625, 2640, 2655, 2665, 2685  ;185, 186, 187. 188, 189  OABE  dw 2705, 2715, 2730, 2750, 2760  ;190, 191, 192, 193, 194  0B04  dw 2780, 2790, 2805, 2820, 2835  ;195, 196, 197, 198, 199  0B4F  dw 2850, 2870, 2880, 2895, 2905  ;200, 201, 202, 203, 204  0B9A  dw 2925, 2940, 2955, 2970, 2985  ;205, 206, 207, 208, 209  0BE5  dw 3005, 3020, 3030, 3045, 3065  ;210, 211, 212, 213, 214  0C3A  dw 3085, 3100, 3115, 3130, 3145  ;215, 216, 217. 218, 219  0C85  dw 3155, 3170, 3190, 3205, 3220  ;220, 221, 222, 223, 224  OCCB  dw 3235, 3250, 3265, 3275, 3290  ;225, 226, 227, 228, 229  ODOC  dw 3300, 3315, 3330, 3340, 3355  ;230, 231, 232. 233, 234  0048  dw 3365, 3385, 3390, 3400, 3415  ;235, 236, 237, 238, 239  0210 021A 0224 022E  0256 0260 026A 0274 027E 0288 0292 029C 02A6 02B0 02BA 02C4 02CE 02D8 02E2 02EC 02F6 0300 030A  07F3 0802 0811 0820 083E 0840 0857 0866 0889 0898 08A7 08B6 0809 08E8 08FC 090B 0933 0942 0956 0960 0988 099C 09B0 09BF 09E2 09EC 0A00 0A14 0A32 0A41 0A50 0A5F 0A7D 0A91 0A9B OAAA 0AC8 OADC 0AE6 0AF5 0B13 0B22 0B36 0B40 0B59 0860 0B7C 0B88 08A9 OBBD OBCC 0BD6 0BF9 OCOD 0C1C 0C2B 0C49 0C53 0C62 0C76 0C94 0CA3 0CB2 0CC1 OCDA 0CE4 0CF3 0002 0D1B 0D25 0D39 003E 0057  The IBM P e r s o n a l Computer A s s e m b l e r 09-11-87  PAGE  1-5  91  213  0314  214 215  031E  216 217  dw 3430, 3445, 3450, 3465, 3475  ;240, 2 4 1 , 242, 243, 244  0098 0DA7 OOAC 0D8B  dw 3480, 3495, 3500, 3515, 3525  ;245, 246, 247, 248, 249  dw 3535, 3545, 3560, 3570, 3580  ;250, 2 5 1 , 252, 253, 254  dw 3585  ;255  0DC5 0328  218 219  0066 0D75 0D7A 0089 0D93  ODCF 0DD9 0DE8 0DF2 00 FC  0332  0E01  220  c a l i b r a t i o n v a l u e s f o r phase s h i f t e r a t t e n u a t i o n  221  at  222  All  10.19 GHz ( i n d B ) . v a l u e s a r e 10X  setting  223 224  0334  00 00 01 01 01  0,  1,  2,  3,  225  0339  02 02 02 02 03  db  2,  2,  2,  2,  3  5,  6,  7,  8,  9  226  033E  04 04 04 04 05  db  4,  4,  4,  4,  5  10,  11,  12.  13,  14  227  0343  05 05 06 06 06  db  5,  5,  6,  6,  6  15,  16,  17,  18,  19  228  0348  06 07 07 07 08  db  6,  7,  7,  7,  8  20,  21,  22,  23,  24  229  0340  08 09 09 09 OA  db  8,  9,  9,  9, 10  25,  26,  27,  28,  29  230  0352  OA OB OB OB OB  db 10, 11. 11, 11, 11  30,  31,  32,  33,  34  231  0357  0B OB OB OB OB  db 11, 11, 11, 11, 11  35,  36,  37,  38,  39  232  035C  OB OC OC OC OC  db 11, 12, 12, 12, 12  40,  41,  42,  43,  44  233  0361  OC OC OC 00 OD  db 12, 12, 12, 13, 13  45,  46,  47,  48,  49  234  0366  OD OD OD OD OC  db 13, 13, 13, 13, 12  50,  51,  52,  53,  54  235  036B  OC OC OC OA OA  db 12, 12, 12, 10, 10  55,  56,  57,  58,  59  236  0370  OA OA 09 09 09  9  60,  61,  62,  63,  64  237  0375  09 09 09 OA OA  db 10, 10, db 9, 9,  69  238  037A  OA OB OB OB OB  239  037F  OB OB OB OB OC  240  0384  241  0389  242  p h _ a t t c a l db  0,  0,  1,  9,  1  1,  9,  4  9, 10, 10  65,  66,  67,  68,  70,  71,  72,  73,  74  75,  76,  77,  78,  79  OC OC OC OC OC  db 10, 11, 11, 11, 11 db 11, 11, 11, 11, 12 db 12, 12, 12, 12, 12  80,  81,  82,  83,  84  OC OC OC OC OC  db 12, 12, 12, 12, 12  85,  86,  87,  88,  89  038E  OB OB OB OB OB  90,  91,  92,  93,  94  243  0393  OB OB OB OA OA  db 11, 11, 11. 11, 11 db 11, 11, 11, 10, 10  95,  96,  97,  98,  99  244  0398  OA OA 09 09 09  db 10, 10,  9,  9,  9  100,  101,  102,  103,  104  245  039D  09 08 08 07 07  db  9,  8,  8,  7,  7  •105,  106,  107,  108,  109  246  03A2  07 07 07 07 07  db  7,  7,  7,  7,  7  •110,  111,  112,  113,  114  247  03A7  06 06 06 06 06  db  6,  6,  6,  6,  6  115,  116,  117,  118,  119  248  03AC  06 05 05 05 05  db  6,  5,  5,  5,  5  •120,  121,  122,  123,  124  249  03B1  05 05 05 04 04  db  5,  5,  5,  4,  4  •125,  126,  127,  128,  129  250  03B6  04 05 05 05 05  db  4,  5,  5,  5,  5  130,  131,  132,  133,  134  251  03BB  06 06 07 07 07  db  6,  6,  7,  7,  7  135,  136,  137,  138,  139  252  03C0  07 07 08 08 08  db  7,  7,  8,  8,  8  140,  141,  142,  143,  144  253  03C5  09 09 OA OA OA  db  9,  9, 10, 10, 10  145,  146,  147,  148,  149  254  03CA  OA OB OB OB OB  151,  152,  153,  154  03CF  OC OC OC OD OE  155,  156,  157,  158,  159  256  03D4  OE OE OE OE OF  db 10, 11, 11, 11, 11 db 12, 12, 12, 13, 14 db 14, 14, 14, 14, 15  150,  255  160,  161,  162,  163,  164  257  0309  OF OF OF OF OF  db 15, 15, 15, 15, 15  165,  166,  167,  168,  169  258  03DE  OF OF OF OF OF  db 15, 15, 15, 15, 15  170,  171,  172,  173,  174  259  03E3  OF OF OF OE OD  db 15, 15, 15, 14,  13  175,  176,  177,  178,  179  260  03E8  00 OC OC OC OC  180,  181,  182,  183,  184  261  03ED  OB OA OA 09 09  db 13, 12, 12, 12, 12 db 11, 10, 10, 9, 9  185,  186,  187,  188,  189  262  03F2  08 07 07 07 07  db  8,  7,  7,  7,  7  190,  191,  192,  193,  194  263  03F7  07 08 08 08 08  db  7,  8,  8,  8,  8  195,  196,  197,  198,  199  264  03FC  08 08 09 09 09  db  8,  8,  9,  9,  9  200,  201, 202,  203,  204  265  0401  09 09 09 09 09  db  9,  9,  9,  9,  9  205,  206,  208,  209  207,  The IBM P e r s o n a l Computer A s s e m b l e r 0 9 - 1 1 - 8 7  1-6  PAGE  92 266  0406  09 09 09 09 09  db  9,  9,  9.  9,  9  2 1 0 , 2 1 1 , 2 1 2 , 2 1 3 , 214  267  040B  09 09 09 09 09  db  9.  9.  9,  9,  9  2 1 5 . 2 1 6 , 2 1 7 , 2 1 8 , 219  268  0410  09 09 09 09 08  db  9,  9.  9,  9,  8  2 2 0 , 2 2 1 , 2 2 2 , 2 2 3 , 224  269  0415  08 08 07 07 06  db  8,  8,  7,  7,  6  2 2 5 . 2 2 6 , 2 2 7 , 2 2 8 , 229  270  041A  06 06 06 06 06  db  6,  6.  6,  6,  6  2 3 0 , 2 3 1 . 2 3 2 , 234, 235  271  041F  05 05 05 05 04  db  5.  5.  5,  5,  4  2 3 6 , 2 3 7 , 2 3 8 , 2 3 9 , 240  272  0424  04 04 04 04 03  db  4,  4,  4.  4,  3  2 4 1 , 2 4 2 , 2 4 3 , 244, 245  273  0429  03 03 02 02 02  db  3.  3,  2.  2,  2  2 4 6 , 2 4 7 , 2 4 8 , 2 4 9 , 250  274  042E  02 02 02 02 01  db  2,  2,  2.  2,  1  2 5 1 . 2 5 2 . 2 5 3 , 254, 255  275  0433  01  db  1  256  276 277  c a l i b r a t i o n v a l u e s f o r G e n e r a l M i c r o w a v e Model 3455  278  a t t e n u a t o r phase s h i f t s ( i n d e g r e e s )  279  all  settings  phase v a l u e s a r e 10X  280 281  0434  282 283  043E 0448 0452 045C 0466 0470  0484 048E 0498 04A2 04AC 04B6 04C0 04CA 04D4  317  14  5.  6,  7,  8,  9  0010 0011 0013 0015  dw  16,  17,  19,  21,  23  10,  11,  12,  13,  14  0019 001B 001D 0020  dw  25,  27,  29,  32,  34  15,  16,  17.  18,  19  0024 0026 0029 002B  dw  36,  38,  41.  43,  45  20,  21,  22.  23,  24  0030 0032 0035 0037  dw  48,  50,  53,  55,  58  25,  26,  27,  28,  29  003C 003F 0041 0044  dw  60,  63,  65,  68,  71  30,  31,  32.  33,  34  0049 004C 004F 0052  dw  73.  76,  79.  82,  84  35,  36,  37,  38,  39  0057 005A 005D 0060  dw  87,  90,  93.  96,  99  • 40,  41,  42,  43,  44  0066 0069 006C 006 F  108, 111, 114  ; 45,  46,  47,  48.  49  dw 118, 121, 124, 127, 130  ? 50,  51,  52,  53,  54  dw 133, 136, 139, 143, 146  ; 55,  56,  57,  58.  59  152, 156. 159, 162  ; 60,  61,  62,  63,  64  dw 165, 169, 172, 175, 179  ; 65,  66,  67,  68,  69  196  ;  70,  71,  72,  73,  74  dw 2 0 0 , 2 0 3 , 2 0 7 , 2 1 0 , 214  ;  75,  76,  77,  78,  79  dw 2 1 7 , 2 2 0 , 2 2 4 , 2 2 7 . 230  ; 80.  81,  82,  83,  84  dw 2 3 4 , 2 3 8 , 2 4 1 , 2 4 5 , 248  ; 85,  86,  87,  88,  89  dw 2 5 2 , 2 5 5 , 2 5 8 , 2 6 2 , 265  ;  91.  92,  93,  94  dw 102, 105,  0076 0079 007C 007F 0085 0088 008B 008F 0095 0098 009C 009F  dw 149,  00A5 00A9 OOAC OOAF 00B6 OOBA OOBD 00C1  dw 182, 186, 189, 193,  00C8 OOCB OOCF 00D2 0009 OODC OOEO 00E3 00E6  040E  316 318  12.  0006  314 315  11,  00C4  312 313  9,  00B3  310 311  8,  00A2  308 309  dw  0092  306 307  0008 0009 000B OOOC  0082  304 305  4  0072  302 303  3,  0063  300 301  2.  0054  298 299  1,  0047 047A  296 297  0,  003A  294 295  6  5,  002D  292 293  3,  0022  290 291  2.  0017  288 289  0.  000E  286 287  a t t _ p h c a l dw  0006  284 285  0000 0002 0003 0005  OOEA OOEE 00F1 00F5 00F8  04E8  OOFC OOFF 0102 0106 0109  90,  The IBM Personal Computer Assembler 09-11-87  PAGE  1-7  93 319  04F2  320 321  04FC 0506 0510 051A 0524 052E 0538 0542  108,  109  dw 320, 324, 327, 331, 335  •110,  111,  112,  113,  114  dw 339, 343, 347, 351, 354  •115,  116,  117,  118,  119  0173  dw 358, 362, 367, 371, 375  120,  121,  122,  123,  124  0182 0186  dw 379, 383, 386, 390, 394  125. 126,  127,  128,  129  0182 0186  dw 379, 383, 386, 390, 394  130,  131.  132,  133.  134  0191 0195 0199  dw 398, 401, 405, 409, 414  135,  136,  137,  138,  139  01A2 01A6 01AA 01AE  dw 418, 422, 426, 430, 434  140,  141,  142,  143,  144  dw 438, 442, 447, 451, 455  145,  146,  147,  148,  149  0140 0144 0147 014B 0153 0157 015B 015F 0166 016A 016F 017B 017F 017B 017F 018E 019E  054C  338 339  107,  018A  336 337  106,  dw 303, 307, 310, 313, 317  018A  334 335  •105,  0133 0136 0139  012F  0177  332 333  104  100,  0162  330 331  103.  dw 286, 290, 293, 297, 300  011E  014F  328 329  101, 102,  0122 0125 0129  01B2 0556  340  01B6 01 BA 01BF 01C3 01C7  341  ; attenuator attenuation c a l i b r a t i o n values  342  ; f o r 10.19 GHz ( i n dB)  343  ;  344  ;  345  0560  346 347  056A 0574 057E 0588  059C 05A6 05B0 05BA 05C4 05CE  2.  3,  4  000D OOOF 0012 0014  13,  15,  18.  20,  23  5.  6.  7,  8,  9  dw 25,  28,  30,  33,  35  ' 10,  11.  12.  13.  14  du  38,  40,  43.  45.  48  • 15,  16.  17,  18.  19  dw 50,  53,  55,  58,  60  ; 20,  21.  22,  23.  24  dw 63,  65,  68.  70,  73  ; 25,  26,  27,  28,  29  dw 75,  78,  80,  83,  85  ; 30,  31.  32.  33,  34  dw 88,  90,  93.  95,  98  ; 35,  36,  37,  38,  39  dw 100, 103,  105,  108,  110  ; 40,  41,  42,  43,  44  dw 113, 115,  118,  120,  123  ; 45,  46.  47.  48,  49  dw 125, 128,  130,  133,  135  ; 50,  51.  52,  53,  54  dw 138, 140,  143,  145,  148  ; 55,  56,  57.  58,  59  dw 150, 153,  155, 158,  160  ; 60,  61,  62,  63,  64  dw 163, 165,  168.  173  ; 65,  66,  67,  68,  69  dw  0019 001C 001E  0021  0026 0028 002B 002D 0032 0035 0037 003A 003 F 0041 0044 0046 004B 004E 0050 0053 0058 005A 005D 005 F 0064 0067 0069 006C 0071 0073 0076 0078 007D 0080 0082 0085 008A 008C 008F 0091 0094  05D8  370 371  1.  0087  368 369  0,  007B  366 367  10  006E  364 365  8,  0062  362 363  5,  0055  360 361  3.  0049  358 359  0.  003C 0592  356 357  dw  0030  354 355  att_attcal  0023  352 353  0003 0005 0008  0017  350 351  0000  setting  a l l values are 10X  0OOA  348 349  96,  0130  326 327  99  95,  012C  324 325  98,  dw 269, 272, 276, 279, 283  011B  322 323  97.  0100 0110 0114 0117  0096 0099 009B 009E 00A0  05E2  00A3 00A5 00A8 OOAA  170,  The IBM Personal Computer Assembler 09-11-87  372 373 374 375 376 377 378 379 380  00AD OOAF 00B2 00B4 00B7 00B9 05 F6 OOBC OOBE 00C1 00C3  05EC  00C6 0600 00C8 OOCB OOCD OODO 00D2 060A 0005 00D7 OODA OODC OODF 0614 00E1 00E4 00E6 00E9  PAGE  1-8  94  dw 175, 178, 180, 183, 185  ; ro. 71.  72,  73,  74  dw 188, 190, 193, 195, 198  ; 75, 76.  77,  78,  79  dw 200, 203, 205, 208, 210  ; so,81,  82,  83.  84  dw 213, 215, 218, 220, 223  ; 85, 86,  87.  88,  89  dw 225, 228, 230, 233, 235  ; 90. 91.  92,  93,  94  OOEB OOEE OOFO 00F3 00F5  dw 238, 240, 243, 245, 248  ; 95, 96,  97,  98,  99  385  00F8 0628 OOFA OOFD OOFF 0102  dw 250, 253, 255, 258, 260  ;100, 101, 102, 103, 104  386 387 388  0104 0107 0109 010C 010E 0111  dw 263, 265, 268, 270, 273  ;105. 106, 107. 108, 109  dw 275, 278, 280, 283, 285  ;110, 111, 112, 113, 114  dw 288, 290, 293, 295, 298  ;115, 116. 117, 118, 119  dw 300, 303, 305, 308, 310  ;120, 121, 122, 123, 124  dw 313, 315, 318, 320, 323  ;125, 126, 127, 128, 129  dw 325, 328, 330, 333, 335  ;130, 131, 132, 133, 134  dw 338, 340, 343, 345, 348  ;135. 136. 137, 138, 139  dw 350, 353, 355, 358, 360  ;140, 141, 142, 1*3, 144  381 382 383 384  389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424  061E  0632 063C  0113 0116 0118 011B 0110 0646 0120 0122 0125 0127 012A 0650 012C 012F 0131 0134 0136 065A 0139 013B 013E 0140 0143 0664 0145 0148 014A 0140 014F 066E  0152 0154 0157 0159 015C 0678 015E 0161 0163 0166 0168 0682  data  ends  » #  0000 0000  stack 80 [  segment stack dw 128 dup(?)  ???? ] 0100  stack  ends  i »  0000 0000  code BRIDGE  segment proc far assume cs:code,ds:data,ss:stack  1  0000  1E  0001 0004 0005 0008  B8 0000 50 B8 R 8E 08  push ds mov ax,0 push ax mov ax,data mov ds,ax 1 1  ;configure for return to DOS  The IBM Personal Computer Assembler 09-11-87  PAGE  1-9  95 425 426 427 428 429 430 431 432 433 434 435 436 437  #  000A 00OA 000D 000F 0010  BA 0283 BO 80 EE BA 0287  mov mov out mov  0013 0015  BO 98 EE  mov al,152 out dx.al  dx.portl al,128 dx.al dx,port2  ;write 8255 #1 programming byte  ;write 8255 #2 programming byte  ; ; Await input commands from keyboard  ;  438  0016 0019 001B  439 440 441  001D 001D 0020  BA 0067 R B4 09  442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471  0022 0024  CD 21 B4 00  0026 0028 002A 002C 002F 002F 0031 0033 0036 0038 003A 003C  CD 3C 75 E9  16 71 03 01B1 R  3C 75 BA B4 CD EB  72 09 007B R 09 21 CE  003C 003E 0040 0045 0048 004A  3C 75 C6 BA 33 EE  00 DD 06 0017 R 00 0281 CO  472 473 474 475 476 477  ;re-initialize ports  restart:  BA 0018 R B4 09 CD 21  mov dx,offset start_mess ;output i n i t i a l message mov ah,9 int 21h key_in: mov dx,offset prompt mov ah,9 int 21h mov ah,0 int 16h cmp al,stop_key jne no_q jmp done  ;output prompt for keyboard input ;print prompt comments ;read keyboard function ;keyboard I/O ;test for q (lower case--quit) ;no q detected ;q detected  no_q: cmp al,rest_key jne no_r mov dx,offset promptr ;output for restart mov ah,9 int 21h jmp restart no_r: cmp a l , 13 jne key_in mov adcount,0 mov dx,attport xor ax,ax out dx,al  ;test for ENTER key ;re-read keyboard until q or ENTER .•initialize A/D sample counter ; i n i t i a l attenuation=0 dB ; during phase scan  ; ;  configure for i n i t i a l phase scan  ; 004B 0051 0056 005B 0060 0063 0066  C7 C6 C6 C6 E8 AO A2  06 0000 06 0002 06 0003 06 0004 01B9 R 0007 R 0006 R  R 0280 R 00 R 03 R 07  mov port.phport mov loval,0 mov hival,3 mov step,7 call balance mov al,balval mov phase,al  .•configure phase shifter port ;Iova 1=0 ;terminate loop after 1 cycle ;step=7 (approx 10 degrees)  ;retain balanced phase  ; ;  configure for i n i t i a l attenuator scan  ; 0069 C7 06 0000 R 0281 006F C6 06 0002 R 00 0074 C6 06 0003 R 54  mov port.attport mov Ioval,0 mov hival,84  .•configure attenuator port ;Iova1=0 ;hival=84  The IBM P e r s o n a l Computer A s s e m b l e r  09-11-87  PAGE  1-10  96 478  0079  C6 06 0004 R 04  mov  479  007E  E8 01B9 R  call  step,4 balance  ;step=4 (1 d B )  480  0081  AO 0007 R  mov  al.balval  481  0084  A2 0005 R  mov  atten,al  ;atten=balval  482  0087  C6 06 OOOF R 00  mov  balcnt.O  ; i n i t i a l i z e balance  counter  ;  483 484  008C  485  008C  FE 06 OOOF R  inc b a l c n t  /increment  486  0090  80 3E OOOF R 1E  cmp b a l c n t , m a x i t  ; l i m i t # of i t e r a t i o n s  487  0095  75 OA  jne  488  0097  BA OODD R  mov d x , o f f s e t nomess  489  009A  B4 09  mov ah,9  490  009C  CD 21  i n t 21h  491  009E  E9 01AE R  jmp newval  492  00 A1  itrate:  balok  balance  counter  ;unable t o balance-->try agai ; o u t p u t u n s u c c e s s f u l message  /maximum i t e r a t i o n s  reached  balok:  493  /  494  ;  495  ;  c o n f i g u r e r e g i s t e r s f o r phase s h i f t e r al,phase  scan  496  00A1  AO 0006 R  mov  497  00A4  A2 0009 R  mov p h o l d . a l  498  00A7  C7 06 0000 R 0280  mov p o r t . p h p o r t  / c o n f i g u r e phase s h i f t e r p o r t  499  00AD  AO 0006 R  mov  /set  500  00B0  2C 03  sub a 1,3  al,phase I ova I,a I  /remember o l d phase s e t t i n g  lower  limit  501  00B2  A2 0002 R  mov  502  00B5  AO 0006 R  mov a I,phase  503  0OB8  04 04  add a l , 4  504  OOBA  A2 0003 R  mov h i v a I , a I  /hival=phase+4  505  00BO  C6 06 0004 R 01  mov  ;step=1 (1.4 d e g r e e s )  506  00C2  E8 01B9 R  call  balance  507  00C5  AO 0007 R  mov  al.balval  508  00C8  A2 0006 R  step,1  mov p h a s e , a l  509  /  510  ;  511  ;  /loval=phase-3 /set  upper  limit  ;phase=balval  configure registers for attenuator  scan  512  OOCB  AO 0005 R  mov  al,atten  513  OOCE  A2 0008 R  mov  attold,al  514  0001  C7 06 0000 R 0281  mov  port.attport  515  0007  3C 03  cmp a l , 3  516  00D9  72 11  jb  lowend  517  0008  8A D8  mov  bl,al  518  OOOD  2C 03  sub a l , 3  /set  519  000 F  A2 0002 R  mov  /loval=atten-3  520  00E2  80 C3 04  add b l , 4  /set  521  00E5  88 1E 0003 R  mov  /hival=atten+4  522  00E9  EB OB 90  I ova I,a I hival.bl  /remember o l d a t t e n s e t t i n g /configure attenuator port  lower upper  limit limit  jmp o k a t t  523  ;  524  ; s e t s c a n range f o r lowa t t e n u a t o r  525  ;  settings  526  OOEC  527  OOEC  C6 06 0002 R 00  mov  I ova 1,0  ; l o v a 1=0  (lower  limit)  528  00F1  C6 06 0003 R 07  mov  hival,7  /hival=7  (upper  limit)  529  0OF6  530  00F6  mov  step,1  /step=1 (0.25 d B )  lowend  okatt: C6 06 0004 R 01  The IBM Personal Computer Assembler 09-11-87  PAGE  1-11  97 531  OOFB  E8 01B9 R  call  532  OOFE  AO 0007 R  mov a l . b a l v a l  533  0101  A2 0005 R  balance  mov atten,al  534  ;  535  ;  536  ;  ;atten=balval  check for phase changes between i t e r a t i o n s  537  0104  AO 0006 R  mov  538  0107  8A 1E 0009 R  mov bl,phold  539  010B  2A C3  sub  al,bl  540  010D  79 02  jns  posta  541  010F  F6 D8  neg a I  542  0111  543  0111  3C 00  cmp a 1,0  545  0113  76 03  jna  546  0115  E9 008C R  jmp i t r a t e  al.phase ;al=phase-phold  posta: ;no phase v a r i a t i o n  544  547  ;  548  ; check for  549  ;  skipl  attenuation changes  550  0118  551  0118  AO 0005 R  skipl: mov a l . a t t e n  552  01 IB  8A 1E 0008 R  mov b l . a t t o l d  553  011F  2A C3  sub a l , b l  554  0121  79 02  jns  555  0123  F6 D8  556  0125  557  0125  3C 01  cmp a 1,1  558  0127  76 03  jna  559  0129  E9 008C R  560  012C  561  012C  8A 1E 0006 R  mov bl,phase  562  0130  32 FF  xor bh.bh  563  0132  8A 87 0334 R  mov al,ph_attcal[bx]  ;get phase s h i f t e r atten  564  0136  32 E4  xor ah,ah  / c l e a r high order b i t  565  0138  A3 0012 R  mov attval.ax  ;store i n main memory  566  013B  03 DB  add bx,bx  ;double f o r word address  567  013D  8B 87 0134 R  mov ax,ph_phcal [bx]  ;get phase s h i f t e r phase (word)  568  0141  A3 0014 R  mov phval.ax  ;store i n main memory  569  0144  8A 1E 0005 R  mov bt,atten  ;put 8 b i t atten value i n bx  570  0148  32 FF  xor bh.bh  571  014A  03 DB  add bx,bx  572  014C  8B 87 0560 R  mov ax,att_attcal[bx] /get atten attenuation (word)  573  0150  01 06 0012 R  add attval,ax  574  0154  8B 87 0434 R  mov  575  0158  01 06 0014 R  add phval.ax  ;al=atten-attold  postp  neg a I postp: ;1 b i t attenuator v a r i a t i o n tolerance  writeout  jmp i t r a t e writeout:  ax,att_phcal[bx]  ;put 8 b i t phase value i n bx  /double f o r word address /add attenuation to t o t a l /get attenuator phase s h i f t (word) /add phase s h i f t to t o t a l  576  015C  BA 0088 R  mov dx,offset attmess /get attenuation message  577  015F  B4 09  mov ah,9  578  0161  CD 21  int 21h  579  0163  A1 0012 R  mov ax,attval  580  0166  E8 0253 R  call  581  0169  AO 0005 R  mov a l . a t t e n  582  016C  32 E4  xor ah,ah  583  016E  E8 0271 R  c a l l decimal out  write_dec  (byte)  /write out attenuation message /write out actual attenuation /(in  dB)  The IBM Personal Computer Assembler  09-11-87  PAGE  1-12  98  584  0171  BO 29  585  0173  E8 028A R  c a l l character_out  586  0176  BA 009B R  mov dx,offset phmess  587  0179  B4 09  mov ah,9  588  mov a l , ' ) ' ;get  phase s h i f t message  017B  CD 21  int 21h  589  0170  A1 0014 R  mov ax.phval  590  0180  E8 0253 R  c a l l write_dec  ;write out actual phase s h i f t  591  0183  AO 0006 R  mov aI,phase  ;(in  degrees)  592  0186  32 E4  xor ah,ah  ;get  i t e r a t i o n counter message  ;write out phase s h i f t message  593  0188  E8 0271 R  call  594  018B  BO 29  mov a 1 , )  595  0180  E8 028A R  c a l l character out  596  0190  BA OOAB R  mov dx,offset  597  0193  B4 09  mov ah,9  598  0195  CD 21  int 21h  599  0197  AO OOOF R  mov a I,balcnt  600  019A  32 E4  xor ah,ah  decimal_out 1  1  itmess  601  019C  E8 0271 R  call  602  019F  BA 00C4 R  mov dx,offset admess  603  01A2  B4 09  mov ah,9  604  01A4  CD 21  int 21h  605  01A6  AO 0017 R  mov al,adcount  606  01A9  32 E4  xor ah,ah  607  01 AB  E8 0271 R  608  call  ;write i t e r a t i o n counter  decimal_out ;get  A/D sample counter message  ;get  A/D sample counter  decimal_out  *  609  01AE  610  01AE  611  01B1  612  01B1  BA 0111 R  mov dx, o f f s e t stopmess  613  01B4  B4 09  mov ah,9  614  0186  CO 21  int 21h  615  01B8  CB  ret  616  01B9  newval: E9 001D R  jmp key_in  ;jump point f o r no balance  done:  BRIDGE  ; p r i n t termination message  endp  617 618  This subroutine outputs phase or attenuation s e t t i n g s from a  619  low l i m i t to a high l i m i t and searches f o r the minimum  620  signal  level  621 622  01B9  623  01B9  B9 0700  mov cx,2000  ;cx=2000 ( i n i t a r b i t r a r y  624  01BC  AO 0002 R  mov a l , l o v a l  ;al=low index ;ah=high index  BALANCE  proc near low value)  625  01BF  8A 26 0003 R  mov ah.hival  626  01C3  8B 16 0000 R  mov dx,port  627  01C7  628  01C7  EE  out dx,al  629  01C8  50  push ax  .•remember ax r e g i s t e r  630  01C9  52  push dx  .•remember dx r e g i s t e r  631  01 CA  E8 01F0 R  c a l l sample  ;get  632  01 CD  5A  pop dx  .•restore dx r e g i s t e r  633  01CE  58  pop ax  .•restore ax r e g i s t e r  634  01CF  8B 1E OOOD R  mov bx,dat  ;store sample value i n bx  635  01D3  3B 09  cmp bx,cx  /compare with e x i s t i n g  636  01D5  77 05  ja bigger  balseq: .•output current value  sample value  low value  The IBM Personal Computer Assembler  09-11-87  PAGE  1-13  99  637  01D7  8B CB  mov cx.bx  ;update new minimum sample value  638  01D9  A2 000C R  mov f l a g , a l  ;update new minimum index  639  01DC  640  01DC  02 06 0004 R  add a I,step  ;index update:  641  01E0  3A C4  cmp a I,ah  .•compare new index with high value  642  01E2  75 E3  Jne balseq  643  01E4  AO OOOC R  mov a I , f l a g  644  01E7  A2 0007 R  mov b a l v a l . a l  645  01EA  8B 16 0000 R  mov dx,port  646  01EE  EE  out dx.al  647  01EF  C3  ret  648  01 FO  bigger:  BALANCE  bl=bl+step  ;balval = f l a g index ;output minimum value  endp  649 650  This subroutine samples the microwave s i g n a l  651  and returns a d i g i t a l value  652  If the signal  653  l i e s i n the 1000-1255 range.  654  If the signal  655  l i e s i n the 0-255 range  i s on i t shigh s c a l e , the output i s on i t s low s c a l e , the output  656 657  01F0  SAMPLE  658  01F0  sampstart:  659  01F0  C6 06 0016 R 14  mov maxsamp,20  /initialize  660  01F5  BA 0286  mov dx,646  ;out 646,0  661  01F8  33 CO  xor ax,ax  / c l e a r s t a r t conversion s i g n a l  662  01FA  EE  out dx.al  /and c l e a r EOC f l a g  663  01 FB  EC  in a I,dx  /al=inp(646) s i g n a l  664  01 FC  24 20  and al,00100000b  /al = 32?  665  01 FE  75 24  jnz  666  0200  BA 0285  mov dx,645  667  0203  BO 01  mov a 1,1  668  0205  EE  out dx,al  /out 645,1:  669  0206  BA 0286  mov dx,646  / s e l e c t high A/D channel  670  0209  B8 0003  mov ax,3  671  020C  EE  672  020D  673  0200  FE OE 0016 R  dec maxsamp  /decrement sample counter  674  0211  74 37  jz  /compare count with max allowable  675  0213  EC  in a I,dx  /al=in(646)  676  0214  24 10  and al,00010000b  /check status of EOC f l a g ( b i t #4)  677  0216  74 F5  jz  /re-sample  678  0218  BA 0284  mov dx,644  proc near counter  range?  lowdat  out dx,al  /out 646,3: s t a r t conversion  eoc_high_wait: escape  eoc_high_wait  EOC b i t u n t i l EOC done  679  021B  EC  in a I,dx  /al=inp(644): input high data  680  021C  32 E4  xor ah,ah  / c l e a r higher order r e g i s t e r  681  021E  05 03E8  add ax,1000  /ax=ax+1000  682  0221  EB 1F 90  jmp datsign  683  0224  684  0224  BA 0285  mov dx,645  685  0227  33 CO  xor ax,ax  686  0229  EE  out dx,al  687  022A  BA 0286  mov dx,646  688  0220  B8 0003  mov ax,3  689  0230  EE  out dx,al  lowdat:  /out 645,0: s e l e c t  low A/D channel  /out 646,3: s t a r t conversion  The IBM Personal Computer Assembler  09-11-87  PAGE  1-14 100  690  0231  691  0231  FE OE 0016 R  dec maxsamp  /decrement sample counter  692  0235  74 13  jz  /compare count with max allowable  693  0237  EC  in al.dx  ;al=in(646)  694  0238  24 10  and al,00010000b  /check status of EOC f l a g ( b i t #4  695  023A  74 F5  jz  /re-sample  696  023C  BA 0284  mov dx,644  697  023F  EC  in al,dx  /al=inp(644): input low s c a l e dat  698  0240  32 E4  xor ah,ah  /clear high order  699  0242  700  0242  A3 OOOD R  mov dat,ax  /dat=sampled signal  701  0245  FE 06 0017 R  inc  /increment A/D sample counter  702  0249  C3  ret  eoc_low_wait: escape  eoc_low_wait  EOC b i t u n t i l EOC done  register  datsign: adcount  value  703 704  •  maximum EOC waiting cycles exceeded  705 706  024A  707  024A  BA 00 F4 R  mov dx,offset nobalmess  708  024D  B4 09  mov ah,9  709  024 F  CD 21  int 21h  710  0251  EB 90  711  0253  escape: /write out max A/D sample message  jmp sampstart SAMPLE  / r e s t a r t from beginning  endp  712 713 714 715  A subroutine to print the contents of  716  the AX r e g i s t e r divided by 10.  717 718 719  0253  720  0253  33 D2  xor dx,dx  /clear higher order word  721  0255  F7 36 0010 R  div base  /double word d i v i s i o n by 10  722  0259  52  push dx  /store remainder  723  025A  E8 0271 R  call  / p r i n t AX r e g i s t e r  724  0250  BO 2E  mov a I,'.  725  025 F  E8 028A R  c a l l character_out  726  0262  58  pop ax  /place remainder  727  0263  E8 0271 R  call  / p r i n t AX r e g i s t e r  728  0266  BO 20  mov a l ,  729  0268  E8 028A R  c a l l character_out  730  026B  BO 28  mov a 1, ('  731  0260  E8 028A R  c a l l character_out  732  0270  C3  733  0271  WRITEJ3EC proc near  decimal_out 1  decimal_out 1  on stack  / p r i n t decimal point i n AX  1  1  ret WRITE_DEC endp  734 735 736  • This subroutine outputs a byte i n decimal  737  • AX contains number to be p r i n t e d  form  738 739  0271  740  0271  741  0274  742  0274  DECIMALJXJT proc near B9 0000  mov cx,0  / i n i t i a l i z e counter  another_digit: 41  inc cx  contents  /increment  counter  register  contents  The IBM Personal Computer Assembler 09-11-87  PAGE  1-15  1 743  0275  33 D2  xor dx.dx  ; c l e a r high order word  744  0277  F7 36 0010 R  div base  ,-divide by base  745  027B  52  push dx  .•remainder i s less s i g d i g i t  746  027C  3D 0000  cmp ax,0  ; i s the quotient  747  027F  75 F3  jne another_digit  ; i f not, more number to convert  748  0281  749  0281  58  pop ax  .•retrieve d i g i t from the stack  750  0282  04 30  add  ;convert to asci i  751  0284  E8 028A R  call  752  0287  E2 F8  loop p r i n t _ d i g i t s  ;do a l I of the d i g i t s  753  0289  C3  ret  ;return to c a l l e r  754  028A  zero?  print_digits: al,'0' characterout  ; p r i n t the character  DECIMALJXJT endp  755 756  output a s i n g l e character  757  character to p r i n t  758  ax and d l destroyed  in al  759 760  028A  761  028A  8A DO  CHARACTERJXJT proc near mov d l , a l  /character to output  762  028C  B4 02  mov ah,2  ;output character f u n c t i o n  763  028E  CD 21  int 21h  ; p r i n t character  764  0290  C3  ret  765  0291  CHARACTERJXJT endp  0291  code  766 767 768  ends end  APPENDIX F ATTENUATOR AND PHASE SHIFTER CALIBRATION The transmission c o e f f i c i e n t s of the d i g i t a l l y  programmable  attenuator and phase s h i f t e r were manually measured using a microwave bridge c i r c u i t as shown in F i g . F.1. An HP X382A rotary vane variable attenuator and an HP X885A rotary vane phase shifter serve as the devices in the reference branch. The HP X382A has minimal phase s h i f t variation with setting and the HP 885A has minimal insertion loss change with s e t t i n g . The measured transmission c o e f f i c i e n t s at 10.19 GHz are shown in Figs. F.2 and F.3. The attenuations and phase s h i f t s of the two devices at a balance point are summed to obtain the t o t a l transmission parameter.  102  A A  A0  manual  manual  Matched Detector  Source  VSWR Indicator  Isolator  AA  or  A0  digital 7V  Isolator  Isolator  Interface TS  Microcomputer  Fig.  F.1  Microwave  circuit  for control  device  calibration. o  to  104  0  25  50  75  100  125  Setting  Fig.  F.2  Attenuator calibration results G e n e r a l M i c r o w a v e M o d e l 3455.  105  Setting  F i g . F.3  Phase s h i f t e r c a l i b r a t i o n results General Microwave Model 7728.  APPENDIX G ENVIRONMENTAL TESTING CHAMBER A testing chamber was constructed by l i n i n g the i n t e r i o r of a plywood box with thermally insulating polystyrene foam. Two cutouts are made on opposite ends of the box for placement of pyramidal horns. Thin (1 cm) low density styrofoam layers i n front of the horns provide an insulating layer. The effect of this styrofoam on the microwave parameters i s minimal because i t has low d i e l e c t r i c constant (e=*1.03) and low loss tangent (tan6£0.0l). Refrigeration panels of a Nova Kool freezing unit are mounted in the box on both sides as indicated in F i g . G1 and can cool the chamber down to -20°C. A rotatable stand holds and orients the sample for any incident p o l a r i z a t i o n angle.  F i g . G.1  View of the environmental 106  testing chamber.  APPENDIX H DETAILED EXPERIMENTAL DATA  Figs. H.1 to H.8 show attenuation vs phase s h i f t plots for various constant s p e c i f i c gravities and moisture contents for Hemlock using transverse p o l a r i z a t i o n . Figs. H.9 to H.19 show a l l the experimental  results obtained  using Douglas F i r samples and transverse p o l a r i z a t i o n .  107  435 410-3 HEMLOCK  transverse polarization  Legend °  samplel  » sample2 • sample3 6  8  10  12  14  16  18  20  22  24  Attenuation (dB)  Fig.  H.1  Phase s h i f t a s a f u n c t i o n o f a t t e n u a t i o n . S p e c i f i c g r a v i t y constant(0.36,0.38) Hemlock: t r a n s v e r s e p o l a r i z a t i o n .  435 -g 410 -j 385-^  HEMLOCK transverse polarization  360-i 335  Legend  -j  310-j  '  285  > sample2  -j  samplel  sample3  260-i  K  235  ' sample4  4 210 4  > sample5  185-j  ' sample6  •pacific gro«lt)r«0.S0  160-j  • sample7  135 4 110  • sample8  -j  85 ~  > sample9  1  4  T 8  10  —r  -  12 14  "T 16  -  18  20  T  22 24  Attenuation (dB)  Fig.  H.2  Phase s h i f t a s a f u n c t i o n o f a t t e n u a t i o n . S p e c i f i c g r a v i t y constant(0.43,0.50) Hemlock: t r a n s v e r s e p o l a r i z a t i o n .  435^ 410 -. 385-.  HEMLOCK  transverse polarization  360 \  335-i 310-j 285 \  260-i 235-i 210-! 185 \  Sp.ciflc  160 \  Gra.ltyIO.SJ  Legend  135-!  ° samplel  110-j 85 J  4  "i— 2 —r 4 ~i— 6 —r 8 1  _,  1  10  12  "i—•—r 14 16  18  20  22  sample2  24  Attenuation (dB)  F i g . H.3  Phase s h i f t as a function of attenuation. S p e c i f i c gravity constant(0.54,0.63). Hemlock: transverse p o l a r i z a t i o n .  Fig. H.4  Phase s h i f t as a function of attenuation. S p e c i f i c gravity constant(0.64). Hemlock: transverse p o l a r i z a t i o n .  F i g . H.5  Phase s h i f t as a function of attenuation. Moisture content constant(0%,3%). Hemlock: transverse p o l a r i z a t i o n .  Fig. H.6  Phase s h i f t as a function of attenuation. Moisture content constant(6%,9%). Hemlock: transverse p o l a r i z a t i o n .  F i g . H.7  Phase s h i f t as a function of attenuation. Moisture content constant(12%,15%). Hemlock: transverse p o l a r i z a t i o n .  435 i  60 i — ' — i — i — i — i — i — ' — i — ' — i — — i — — i — — i — i — i — — i — ' — i 1  0  2  4  6  8  10  1  12  1  14  1  16  18  20  22  Attenuation (dB)  Fig.  H.8  Phase s h i f t as a function of attenuation. Moisture content constant(18%,21%). Hemlock: transverse p o l a r i z a t i o n .  DOUGLAS FIR frequency = 10.19 GHz transverse polariztion specific grovity = 0.*2  Legend o samplel a sample2 • sample3 * sample4 5  10 Moisture Content (%)  Fig.  H.9  15  i  20  Attenuation and phase s h i f t as a function of moisture content for a t y p i c a l s p e c i f i c gravity. Douglas F i r : transverse p o l a r i z a t i o n .  DOUGLAS FIR transverse polarization  Legend A  sg=0.42  x sg=0.50 •  sg=0.54  H sg=0.57 -J— 10  l 12  14  —r16  18  Moisture Content (%)  Fig.  H.10  Attenuation and phase s h i f t as a function of moisture content for various s p e c i f i c g r a v i t i e s . Douglas F i r : transverse p o l a r i z a t i o n .  16  118 D O U G L A S FIR transverse polarization  14 12 -  3  10  c o  •' 5  8  3 C  5  Legend mc=0%  6  mc=3% mc=6" mc=9%  mc=12^ 0.40  0.45  0.50  0.55  0.60  Specific Gravity  350-i  300-  %  DOUGLAS FIR t r a n s v e r s e polarization  250  cn C  200  -C CO  0) 0) O X  Legend  150  mc=0%  0_  mc=3%  100  mc=6% mc=9% mc=12%  50 0.40  0.45  0.50  0.55  0.60  Specific Gravity  Fig.  H.11  A t t e n u a t i o n and phase s h i f t as a f u n c t i o n of specific gravity for various moisture contents. Douglas F i r : transverse polarization.  4  119  DOUGLAS FIR transverse polarization 3.5  1 -) 0  Fig.  H.12  ,  1  2  1  1  4  1  1  6  ,  1  1  1  1  1  8 10 12 Moisture Content (%)  ,  p—i 14  1  16  ,  •  sg=0.54  B  sg=0.57  1  18  Permittivity as a function of moisture for various s p e c i f i c g r a v i t i e s . Douglas F i r : transverse p o l a r i z a t i o n .  content  DOUGLAS FIR transverse polarization  Legend mc=0% mc=3% mc 6% =  mc=9% mc=12% 0.40  0.45  0.50  0.55  0.60  Specific Gravity  Fig. H.13  P e r m i t t t i v i t y as a function of s p e c i f i c gravity for various moisture contents. Douglas F i r : transverse p o l a r i z a t i o n .  400  F i g . H.14  121  Phase s h i f t as a function of attenuation. Specific gravity constant(0.38,0.42). Douglas F i r : transverse p o l a r i z a t i o n .  100 H 0  1—i 2  1 1 1 1 1 1 ' 4  6  8  1— —i—' 1  10  12  1—'—i 14  16  '—i 18  ' — i 20  Attenuation (dB)  Fig. H.15  Phase s h i f t as a function of attenuation. Specific gravity c o n s t a n t ( 0 . 4 7 , 0 . 5 4 ) . Douglas F i r : transverse p o l a r i z a t i o n .  F i g . H.16  Phase s h i f t as a function of attenuation. Specific gravity constant(0.57,0.61). Douglas F i r : transverse p o l a r i z a t i o n .  400-i  124 DOUGLAS FIR transverse polarization  350-  a>  £  300-  CO "D £  250-  to O  200-  0_ moisture content=0% 150-  1008  10  12  14  16  18  20  Attenuation (dB)  400-,  DOUGLAS FIR transverse polarization 350  %  300-  Oi 0 ^  1c  250-  <s  a  200  CL moisture content=3% 150-  1006  Fig. H.17  8  10  ~~r~ 12  Attenuation (dB)  -"i— 14  16  18  20  Phase s h i f t as a function of attenuation. Moisture content constant(0%,3%). Douglas F i r : transverse p o l a r i z a t i o n .  F i g . H.18  Phase s h i f t as a function of attenuation. Moisture content constant(6%,9%). Douglas F i r : transverse p o l a r i z a t i o n .  Fig. H.19  Phase s h i f t as a function of attenuation. Moisture content constant(12%). Douglas F i r : transverse p o l a r i z a t i o n .  APPENDIX I PHOTOGRAPHS OF THE SYSTEM Figs. 1.1 to 1.3 show various parts of the measurement system and Figs. 1.4 to 1.6 show the data a c q u i s i t i o n c i r c u i t boards.  Fig. 1.1  View of transmitting portion of microwave bridge c i r c u i t . 127  Fig. 1.2  View of receiving portion of microwave bridge c i r c u i t .  Fig. 1.3  View of microwave bridge c i r c u i t .  Fig. 1 . 5  View of interface board #1.  1 30  F i g . 1.6  View of interface board #2.  

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