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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.Sc, The University of B r i t i s h Columbia, 1985 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE in THE FACULTY OF GRADUATE STUDIES E l e c t r i c a l Engineering We accept t h i s thesis as conforming -to the required standard THE UNIVERSITY OF BRITISH COLUMBIA August 1987 © James Loo, 1987 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at The University of British Columbia, I agree that the Library shall make i t freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the Head of my Department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Electrical Engineering The University of British 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 f i e l d parameters transmitted through a dielectric material. These parameters are used to calculate the complex dielectric constant with the free-space transmission technique. The system is used to measure the f i e l d parameters transmitted through dimension lumber and a correlation is made with two strength determining factors of lumber: specific gravity and moisture content. Hemlock and Douglas Fir wood samples were tested and a grading technique was implemented. The system is capable of estimating the specific gravity to ±0.05 accuracy and the moisture content to ±3.0% accuracy. T A B L E O F C O N T E N T S Abstract i i Table of Contents i i i List of Figures vi List of Tables ix Acknowledgements x 1. INTRODUCTION 1 1.1. Background on Dimension Lumber 1 1.1.1. Variability in Wood 1 1.2. Specific Gravity Property 2 1.3. Moisture Content 4 1.4. Grading 5 1.4.1. Specific Gravity Measurements 7 1.4.2. Moisture Content Measurement Devices 8 1.4.3. Microwave meters 9 1.5. Thesis Objectives 10 1.6. Thesis Outline 10 2. DIELECTRIC PROPERTIES OF WOOD 12 2.1. Factors Affecting Permittivity 12 2.1.1. Moisture Content 12 2.1.2. Specific Gravity 13 2.1.3. Temperature 13 2.2. Previous Wood Microwave Investigations 14 2.3. Wave Propagation in Wood 16 2.4. Principles of Microwave Measuring Systems 17 3. DIELECTRIC CONSTANT MEASUREMENT SYSTEM 19 3.1. System Requirements 19 3.2. Microwave Bridge Free Space Technique 19 3.3. Theoretical Considerations 21 3.4. Transmission Coefficient 23 3.5. Frequency Selection 24 3.6. Measurement System Configuration 25 3.6.1. Microwave Circuit Layout 25 3.6.2. Data Acquisition 27 3.6.3. Bridge Balancing Algorithm 28 3.7. Measurement System Performance 29 3.7.1. Accuracy 29 3.7.2. Speed 32 3.7.3. Dynamic Range 33 4. EXPERIMENTAL PROCEDURES AND RESULTS 34 4.1. Experimental Procedures 34 i i i 4.2. Results 37 4.2.1. Effect of Moisture Content on AA and A0 .. 37 4.2.2. Effect of Specific Gravity on AA and L\<p .. 40 4.2.3. Effect of Moisture Content on Dielectric Constant 40 4.2.4. Effect of Specific Gravity on Dielectric Constant 40 4.2.5. Effect of Temperature 49 4.2.6. Integrated Data Analysis 54 4.2.6.1. Grading Technique 57 4.2.6.2. Accuracy 57 4.3. Douglas Fir Data 60 5. CONCLUSIONS AND SUGGESTIONS FOR IMPROVEMENT 63 5.1. Conclusions 63 5.2. Limitations of the Measurement System 64 5.3. Further Improvements 66 REFERENCES 69 Appendix A Derivation of Free Space Transmission Coefficient 72 Appendix B Permittivity Calculation from Free Space Measurements 75 APPENDIX C Data Acquisition Circuitry 78 APPENDIX D Interface Circuitry 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 i v Li s t ofFigures Fig. 1.1 Strength as a function of specific gravity 3 Fig. 1.2 Strength as a function of moisture content 3 Fig. 3.1 Basic microwave bridge c i r c u i t 20 Fig. 3.2 Experimental microwave bridge circuit 26 Fig. 4.1 Microwave signal polarization 35 Fig. 4.2 Microwave measurements as a function of grain angle ..35 Fig. 4.3 Attenuation and phase shift as a function of moisture content for a typical specific gravity. Hemlock: transverse polarization 38 Fig. 4.4 Attenuation and phase shift as a function of moisture content for a typical specific gravity. Hemlock: longitudinal polarization 39 Fig. 4.5 Attenuation and phase shift as a function of moisture content for various specific gravities-. Hemlock: transverse polarization 41 Fig. 4.6 Attenuation and phase shift as a function of moisture content for various specific gravities. Hemlock: longitudinal polarization 42 Fig. 4.7 Attenuation and phase shift as a function of specific gravity for various moisture contents. Hemlock: transverse polarization 43 Fig. 4.8 Attenuation and phase shift as a function of specific gravity for various moisture contents. Hemlock: longitudinal polarization 44 Fig. 4.9 Permittivity as a function of moisture content for various specific gravities. Hemlock: transverse polarization 45 Fig. 4.10 Permittivity as a function of moisture content for various specific gravities. Hemlock: longitudinal polarization 46 Fig. 4.11 Permittivity as a function of specific gravity for various moisture contents. Hemlock: transverse polarization 47 v Fig. 4.12 Permittivity as a function of specific gravity for various moisture contents. Hemlock: longitudinal polarization 48 Fig. 4.13 Attenuation and phase shift as a function of temperature for various moisture contents. Specific gravity=0.39. Hemlock: transverse polarization 50 Fig. 4.14 Attenuation and phase shift as a function of temperature for various moisture contents. Specific gravity=0.40. Hemlock: transverse polarization 51 Fig. 4.15 Attenuation and phase shift as a function of temperature for various moisture contents. Specific gravity=0.54. Hemlock: transverse polarization 52 Fig. 4.16 Dielectric constant as a function of temperature for various moisture contents. Specific gravity=0.40. Hemlock: transverse polarization 53 Fig. 4.17 Phase shift as a function of attenuation for various specific gravities and moisture contents. Hemlock: transverse polarization 55 Fig. 4.18 Phase shift as a function of attenuation for various specific gravities and moisture contents. Hemlock: longitudinal polarization 56 Fig. 4.19 Phase shift as a function of attenuation for various specific gravities and moisture contents. Douglas F i r : transverse polarization 61 Fig. C.1 Schematic diagram of amplifier circuit 80 Fig. C.2 Schematic diagram of analog/digital converter circuit 81 Fig. D.1 Schematic diagram of interface board #1 84 Fig. D.2 Schematic diagram of interface board #2 85 Fig. F.1 Microwave circuit for control device calibration ....103 Fig. F.2 Attenuator calibration results General Microwave Model 3455 104 vi Fig. F.3 Phase shifter calibration results General Microwave Model 7728 105 Fig. G.1 View of the environmental testing chamber 106 Fig. H.1 Phase shift as a function of attenuation. Specific gravity constant(0.36,0.38). Hemlock: transverse polarization 108 Fig. H.2 Phase shift as a function of attenuation. Specific gravity constant(0.43,0.50). Hemlock: transverse polarization 109 Fig. H.3 Phase shift as a function of attenuation. Specific gravity constant(0.54,0.63). Hemlock: transverse polarization 110 Fig. H.4 Phase shift as a function of attenuation. Specific gravity constant(0.64). Hemlock: transverse polarization 111 Fig. H.5 Phase shift as a function of attenuation. Moisture content constant(0%,3%) . Hemlock: transverse polarization 112 Fig. H.6 Phase shift as a function of attenuation. Moisture content constant(6%,9%). Hemlock: transverse polarization 113 Fig. H.7 Phase shift as a function of attenuation. Moisture content constant(12%,15%). Hemlock: transverse polarization 114 Fig. H.8 Phase shift as a function of attenuation. Moisture content constant(18%,21%). Hemlock: transverse polarization 115 Fig. H.9 Attenuation and phase shift as a function of moisture content for a typical specific gravity. Douglas F i r : transverse polarization 116 Fig. H.10 Attenuation and phase shift as a function of moisture content for various specific gravities. Douglas F i r : transverse polarization 117 Fig. H.11 Attenuation and phase shift as a function of specific gravity for various moisture contents. Douglas F i r : transverse polarization 118 v i i F i g . H.12 P e r m i t t i v i t y 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 119 F i g . 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 120 Fi g . H.14 Phase s h i f t as a function of attenuation. Spe c i f i c gravity constant(0.38,0.42). Douglas F i r : transverse p o l a r i z a t i o n 121 Fi g . H.15 Phase s h i f t as a function of attenuation. S p e c i f i c gravity constant(0.47,0.54). Douglas F i r : transverse p o l a r i z a t i o n 122 Fi g . H.16 Phase s h i f t as a function of attenuation. Spe c i f i c gravity constant(0.57,0.61). Douglas F i r : transverse p o l a r i z a t i o n 123 Fi g . H.17 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 124 Fig. 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 125 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 126 Fi g . 1.1 View of transmitting portion of microwave bridge c i r c u i t 127 Fi g . 1.2 View of receiving portion of microwave bridge 128 Fi g . 1.3 View of microwave bridge c i r c u i t 128 Fig. 1.4 View of A/D converter c i r c u i t 129 Fig. 1.5 View of interface board #1 129 Fi g . 1.6 View of interface board #2 130 v i i i 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 A C K N O W L E D G E M E N T S I would like 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 is made to the University of British 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 assisting in the building of the environmental testing chamber, Mr. Roger Mulligan for assisting in the design and construction of the data acquisition circuit board, and Ms. Joanna Taylor and Mr. Shen Liang for assisting in measuring the wood samples. x 1 . INTRODUCTION j 1.1. BACKGROUND ON DIMENSION LUMBER D i m e n s i o n lumber, a t i m b e r p r o d u c t w h i c h i s 1 . 5 i n c h e s t o 3 . 5 i n c h e s i n t h i c k n e s s and 3 . 5 i n c h e s o r more i n w i d t h , i s a s a w m i l l ' s main p r o d u c t . An i m p o r t a n t u s e o f d i m e n s i o n lumber i s as a c o n s t r u c t i o n m a t e r i a l i n s t r e s s b e a r i n g s t r u c t u r e s . T h e r e f o r e , wood s t r e n g t h i s a p r i m a r y c o n s i d e r a t i o n i n t h e d e s i g n o f wooden s t r u c t u r e s . S t r e n g t h p r i m a r i l y depends on s p e c i f i c g r a v i t y , m o i s t u r e c o n t e n t , s l o p e o f g r a i n , and t h e p r e s e n c e of d e f e c t s s u c h a s k n o t s [ l 2 ] . 1.1.1. V a r i a b i l i t y i n Wood I n d i v i d u a l p i e c e s o f wood c a n d i f f e r w i d e l y i n s t r e n g t h due t o wide v a r i a t i o n s i n t h e c h a r a c t e r i s t i c s between t r e e s [ l 2 ] . Wood i s n a t u r a l l y p r o d u c e d under a v a r i e t y o f d i f f e r e n t u n c o n t r o l l e d e n v i r o n m e n t a l c o n d i t i o n s s u c h a s g e o g r a p h i c a l l o c a t i o n , s o i l t y p e , p r e c i p i t a t i o n , e x p o s u r e , and e l e v a t i o n . T r e e s a r e a l i v e and p r o d u c e wood o f d i f f e r e n t p r o p e r t i e s a t d i f f e r e n t a g e s . V a r i a t i o n of p h y s i c a l p r o p e r t i e s o c c u r s w i t h i n s p e c i e s and w i t h i n i n d i v i d u a l t r e e s . S i l v i c u l t u r a l p r a c t i c e s c a n improve t h e r a t e o f d i a m e t e r and h e i g h t g r o w t h i n t r e e s . Wood y i e l d i s i n c r e a s e d but s p e c i f i c g r a v i t y i s l o w e r e d . Wood from i n t e n s i v e l y managed f a s t - g r o w i n g t r e e s t e n d s t o be o f l o w e r s p e c i f i c g r a v i t y t h a n 1 2 wood from older slow-growing trees of the same size. Within a particular tree, the specific gravity of wood varies with i t s location in the tree. For instance, specific gravity tends to increase from pith to bark and from crown to base for conifers. 1.2. SPECIFIC GRAVITY PROPERTY The specific gravity of wood is a measure of the relative amount of solid c e l l wall material in a given volume. Basic specific gravity is defined as: sp gr (basic) = oven dry weight of sample (1) green volume of sample 2 expressed as a ratio to the density of water (1g/cm ). A strong relationship exists between specific gravity and strength of clear wood. This relationship can be roughly approximated by the equationf21 ]: S=K(G) n (2) where S is a strength property (i.e. modulus of rupture, compression parallel to grain), K is a proportionality constant differing for each strength property, G is the specific gravity, and n is an exponent that defines the shape of the curve representing the relationship. Fig. 1.1 illustrates this relationship for one strength property at two moisture contents. i ' i 1 i 1—i—1—i—1—i—1—i—1—i—'—i—'—i—'—f 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Specific gravity F i g . 1.1 Strength 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 (from Wangaard[21] ) . Moisture Content (%) F i g . 1.2 S t r e n g t h as a f u n c t i o n of moisture content (from Wangaard[2 1 ] ) • 4 1.3. MOISTURE CONTENT Wood is a hygroscopic substance having an af f i n i t y for water and other polar molecules. Moisture content in wood is 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 is 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 slight lateral expansion of the c e l l wall occurs to accommodate bound water. When a l l available hydrogen bonding sites have been occupied by liquid molecules, the c e l l wall is completely saturated. This is called the fiber saturation point. Above this point, usually about 30% mc, water is stored as free water in the c e l l lumina and the wood is referred to as green wood. Wood strength properties are greatly affected by the quantity of water present. Its strength and elastic characteristics vary inversely with its moisture content below the fiber saturation point as illustrated in Fig. 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 is important during drying because wood must be dried to a maximum moisture content of 19% 5 in order to meet building code requirements in structural applications. High moisture content levels affect strength and can cause glue failures during the manufacture of glued wood products. Freshly cut wood is often kiln dried to achieve the desired moisture content. Overdried wood, on the other hand, suffers from splits and twists due to shrinkage, resulting in lower commercial value and higher drying costs. The moisture content of kiln 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 quality. Lumber suffers from greater warping and increased proportion of lower grades which causes problems in construct ion[22]. It is desirable to quantify wood quality by estimating the mechanical strength of every piece of wood as i t is 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 efficiently used. Material and cost savings result using stress graded timber since high safety factors become unnecessary. 6 Visual grading is most commonly used to evaluate wood quality. Wood is classified and sorted according to the presence of visible knots and defects. The grading rules tend to be very conservative, resulting in inefficient use of wood because high density timber can pass for low quality. In addition, low density timber can pass for high quality and cause construction problems. A very effective grading technique is mechanical stress rating in which the stiffness of a piece of wood is estimated by measuring it s deflection under a bending load. The modulus of elasticity can be calculated i f the wood dimensions are known. In addition, each piece receives a visual inspection for features that are important for its usage. However, this device can only measure strength in the flat 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 satisfy certain minimum c r i t e r i a : 1. i t must address a l l the main factors affecting strength 2. i t must recognize and accommodate the complex nature and variability 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 mill environment with minimal attention 7 4 . i t should be simple to operate, requiring minimal training. It is useful to measure two primary wood strength indicators: specific 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 different methods used for estimating these two properties of wood. One common method for measuring moisture content is a destructive technique which consists of weighing a wood specimen before and after oven drying to zero moisture content[l]. The volume is measured to deduce its specific gravity. This technique is suitable for experimental purposes on a limited number of samples but is not useful for production purposes since i t is slow and destructive. 1.4.1. Specific 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 practical 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 calibration. 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 is related to the moisture content. A DC resistance meter is inexpensive and portable. However, the measuring process is 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 mi l l . RF power loss meter: The dielectric constant of wood is related to its moisture content. The moisture content is estimated from RF power loss in wood placed adjacent to two RF electrodes. This type of meter is limited to measuring moisture content near the surface because the electric f i e l d decreases exponentially into the wood. The meter is insensitive to moisture in the core of thick samples. Infrared meter: A given amount of heat radiation is applied to the surface of a piece of lumber and the temperature of the wood is measured with an infrared detector. Since the specific heat of water is 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 is 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 kiln drying[6]. High temperature kiln drying can produce very wide variations in moisture content between the shell and core. For example, the shell 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 dielectric properties of wood at microwave frequencies are dependent upon moisture content, specific 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 is suitable for on-line measurements with the speeds encountered in mill environments. Microwave equipment has become more affordable so the technology is 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 distributed and the material density is constant. 10 1.5. THESIS OBJECTIVES This work is the development of a microwave grading system module proposed by Kharadly[7] to measure two primary strength determining properties of wood: specific gravity and moisture content. In this thesis, work is undertaken to: 1. design and implement a non-contact system that can automatically measure and continuously monitor the microwave dielectric properties of materials in real time 2. experimentally determine the relationship between the dielectric properties of wood and i t s moisture content, specific gravity, and temperature for two softwood species common to British Columbia: Hemlock and Douglas Fir 3. u t i l i z e the relationships observed in (2) to implement a technique for estimating the specific 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 permittivity. Chapter 3 presents a microprocessor-controlled microwave system which automatically measures the parameters of an 11 electromagnetic wave transmitted through a dielectric 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 its specific gravity, moisture content, and temperature for two species are presented in Chapter 4. A grading technique based on measurements is presented and it s accuracy is assessed. Conclusions and suggestions for improvement and further development of the work described in this thesis are contained in Chapter 5. 2. DIELECTRIC PROPERTIES OF WOOD The dielectric properties of a material can be expressed explicitly in terms of the permittivity e = e ' - e " where e ' = e r ' c 0 = dielectric constant, e"=loss factor for materials, co=angular frequency of the microwave, and e 0=dielectric constant of free space. The loss tangent (tan5) is 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 is a function of its water content and physical properties. The parameters of an electromagnetic fi e l d interacting with wood are related to the permittivity of wood, its dimensions, and the measuring system configuration. 2.1. FACTORS AFFECTING PERMITTIVITY 2.1.1. M o i s t u r e Content The principle of microwave moisture content measurement is based on the fact that water has a greater dielectric constant and is more lossy than most dry substances at high frequencies. A small variation in water quantity can cause significant changes in the overall permittivity of a wet substance such as wood. For example, in the microwave frequency range, e ' of pure water typically ranges from 20 to 80 and tan5 ranges from 0.05 to 1.5. 12 13 Most dry materials, on the other hand, typically 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 restricted polarization but at higher moisture contents water has increased polarization. The dielectric 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 dielectric constant. 2.1 .2 . Specific Gravity The specific gravity of wood depends on the relative amounts of solid wood material and air present in a given volume. Dense wood has a larger proportion of cells with thicker walls and smaller air cavities. Air has a dielectric constant of approximately 1.0 but solid cellulose wood substance has a value of approximately 4.5. Hence, a relationship should exist between the specific gravity of wood and dielectric constant. 2.1.3. Temperature The dielectric properties of water are functions of temperature so the permittivity of wet wood is also affected by temperature[5]. Any microwave measurement system must account for temperature effects because wood is graded in a variety of 1 4 environmental conditions. 2 . 2 . PREVIOUS WOOD MICROWAVE INVESTIGATIONS The primary objective in microwave wood grading is to correlate measured microwave properties with the physical properties of materials. Detailed observations on the dielectric properties of wood at microwave frequencies are limited but results are available at lower frequencies. Many experimenters have observed the anisotropy of wood permittivity. The dielectric constant of wood longitudinal to the grain is greater than that transverse to the grain at a l l frequencies. Skaar [ l7] attempts to explain wood anisotropy in terms of the structure of c e l l walls. Wood c e l l cellulose is composed of chain molecules which are parallel at intervals throughout their length. These form crystallites whose long axes are parallel to the long axes of the wood cells and hence parallel to the grain. Hydroxyl groups and water molecules are arranged along the sides of the cellulose molecules. Polarization due to rotation or vibration occurs more easily when an electric f i e l d is applied parallel to the cellulose chains than when the electric f i e l d is perpendicular. This difference in dipole polarizations accounts for the anisotropy of the dielectric constant. 1 5 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 specific gravity. James and Hamill[4] investigated Douglas Fir 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 specific 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 dielectric 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 details on the performance of the system are sparse. 16 Yen[24] used a 4.81 GHz microwave system to study the relationship between the dielectric properties of wood and i t s physical properties for nondestructive testing. The system used an electri c a l l y modulated mechanically spun dipole as a scattering device for microwaves transmitted through wood samples. Yen observed trends in the dielectric properties of wood as a function of its physical properties but did not test enough specimens to produce a reliable grading device. The instrumentation is delicate and not practical for use in a wood mill 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 specific gravity and moisture content of wood can be simultaneously estimated by measuring the attenuation and phase shift 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 electrical parameters e, u, a of the medium. Suppose a wave is propagating in the direction of positive x: A v e ^ x = [ A o e ^ ° ] [ e - ( a + ^ ) x ] where: 17 •Ax,0 x=amplitude and phase at x •A 0,^amplitude and phase at x=0 • a,j3=attenuation and phase coefficients of the medium and are known functions of e, M , and a. a takes both ohmic and polarization losses into account. The microwave is attenuated (e a x ) and phase-delayed ( 0 x ) relative to x=0 as i t propagates a distance x in the medium. If a wave is normally incident on a slab of material of thickness t located between x=0 and x=t, the wave wi l l be partially reflected at the interface x=0, attenuated and phase-shifted, and then partially reflected at the interface x=t. These partial reflections will result in slightly altered overall values of attenuation and phase delay. Changes in specific gravity or moisture content will cause changes in e and tan5 of the wood. This yields new values of attenuation and phase shift. 2.4. P R I N C I P L E S O F M I C R O W A V E M E A S U R I N G S Y S T E M S Measuring the specific gravity and moisture content of materials with microwave instrumentation requires[8]: 1. determining the relationship between the material permittivity, specific gravity and moisture content: e=f,(mc,sp gr) 18 2 . determining the relationship between the electromagnetic wave characteristics, and the material permittivity, e: $=f 2(e) 3 . determining the relationship between the instrumentation outputs, *, and the electromagnetic wave characteristics, *=f 3(*)• The permittivity of materials is a function f, of material state and structure. It is also dependent on temperature and frequency. The function f 2 is affected by measuring system design factors such as frequency, sensor dimensions, and impedance matching. The function f 3 depends on the design of transducers, amplifiers, and signal processing devices. In general, the relationships are non-linear and the dielectric properties of multiphase mixtures are not well understood. The starting point to a practical microwave instrument design is 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 is possible to determine the weight of water and dry material from the measured values of attenuation and phase shift. Instead of exactly solving the complicated analytical relations, an empirical method may be used to find: mc=M(attenuation, phase shift) and sp gr=p(attenuation, phase shift) 3. DIELECTRIC 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 is an inhomogeneous material, a large measurement area is 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 shift of an unknown element with that of a standard attenuator and phase shifter[9]. A microwave bridge circuit is favoured because of its low cost and simplicity for usage in an industrial environment. 3.2. MICROWAVE BRIDGE FREE SPACE TECHNIQUE A basic block diagram of a microwave bridge is shown in Fig. 3.1. The system consists of a microwave signal which is spli t into two channels: a reference channel and a test channel. The reference channel contains a variable attenuator and a variable phase shifter while the test channel contains 19 R e f e r e n c e Channel Source Isolator Variable Attenuator Isolator Variable Phase Shifter Isolator Test Sample Matched Detector T e s t Channel Fig. 3.1 Basic microwave bridge c i r c u i t . o 21 transmitting and receiving antennas. The two channels are combined and the signal is incident upon a crystal diode detector whose response is amplified and displayed. The testing section of the device consists of two horn antennas separated by a fixed distance. The transmitting antenna launches a linearly polarized plane wave which is normally incident upon a dielectric sample in the propagation path. A receiving antenna collects the signal transmitted through the dielectric. For each dielectric sample measurement, the attenuator and phase shifter values required to produce a null 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 dielectric constant. The operation of this microwave bridge is independent of the source power level and detector sensitivity provided that the transmitted signal is detectable. 3 . 3 . THEORETICAL CONSIDERATIONS The electric fields of the two signals propagating in the two channels and incident upon the power combiner are assumed to have the form[3]: e1=E,cos(27rft + 0) 22 e2=E2cos(27rf t + 0) where f=microwave signal frequency, E, ,E2=magnitudes in channels 1 and 2, and 0,0=phases in channels 1 and 2. The general transfer function of the detector element has the form: i=a,e+a2e +...+ane +... (5) where e=e1+e2. For low signal levels, the detector response is essentially square law so only the second order term in the expansion is considered. The detector output is fed into an amplifier whose output voltage i s : V=*K(E,2+E22 + 2E 1E 2cos(0-9) ) (6) where K is a gain constant. V can be made zero i f : E 1 2+E 2 2+2E 1E 2cos(0-5)=O (7) which is possible i f E,=E2 and <f>-8=nir, where n=1,3,5,... The bridge can be adjusted to a null by varying the attenuator and phase shifter 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 null. Therefore the relative attenuation and phase of the unknown signal introduced by a test object can be determined i f n is known. 23 3 . 4 . TRANSMISSION COEFFICIENT To compute the permittivity of the unknown sample, the transmission coefficient must be known. The transmission coefficient can be calculated from: •A0,0o=attenuator and phase shifter setting with no sample present •A,,0,=attenuator and phase shifter setting with sample present •AA=A,-A0=attenuation shift (in dB) • A 0 = 0 , - 0 o=phase shift (in degrees) The amplitude and phase of an electromagnetic wave transmitted through a dielectric depend on the electric and magnetic properties of the medium. The transmission coefficient of a linearly polarized plane wave normally incident upon a homogeneous dielectric slab of thickness 1 is (Appendix A): T, 3= 4ze"~yl  ( z + 1 ) 2 - ( z - i ) 2 e - 2 7 l (8) where: • z=normalized impedance of dielectric sample=y/(u/e )//(u0/e0 ) z=1/V(1/e ) since n=urn0 and e = e r e 0 where Mr=1 for non-magnetic materials such as wood • 7=complex propagation constant in dielectric = j/30/( e' (1 - jtan5)) • /30 = 27r/X0 = free space propagation constant •X0=free space wavelength 24 The measured attenuation shift and phase shift are related to T,3 where: AA=|T13| and A0=Arg(T,3)-p0l (9) The term (z-1) 2e 2 - y l in the denominator of (8) accounts for the effect of multiple internal reflections in the slab. If the material is lossy or sufficiently thick, e'^^O so the transmission coefficient can be approximated by: T, 3~4ze 7 1 (z-H) 2 ( 1 0 ) First order estimates for e' and tanS can then be analytically obtained: e , - ( l + U*/p , 0l)) 2 (11) e"/e'=tan5~ ln[r/e"((1//e')+1)2/4] ( - M / « 7 2 ) where r = l O _ A A / 1 ° . (12) The exact permittivity is obtained by solving Eq. (8) numerically using Eqs. (11) and (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 test. The diameter of the structural particles 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 is important since i t determines the economic feasibility 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 easily meet the wavelength size requirements and have been used by other investigators[4 , 7 , 1 4] to study dielectric behaviour of wood over a wide range of moisture contents. 3 . 6 . MEASUREMENT SYSTEM CONFIGURATION 3 . 6 . 1 . Microwave Circuit Layout The experimental setup is shown in Fig. 3 . 2 . The source consists of a 10 GHz Varian X-13 reflex klystron. The CW signal is split among two channels by a 10 dB directional 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 shifter model 7728 ( 0 - 3 6 0 ° phase s h i f t ) . The transmission coefficients of these two devices are measured over a l l settings at an operating frequency of 10.19 GHz. A l l components, except for the SMA control devices, are WR90 copper waveguide propagating the dominant T E 1 0 mode. The linearly Microcomputer LL Interface R e f e r e n c e Channel Klystron Power Supply Klystron F requency Meter —» Isolator A0 manual T Isolator AA manual AA manual —> Isolator T e s t Channel A0 digital AA digital Isolator —» T Isolator Matched Detector Analog/ Digital Converter Fig. 3.2 Experimental microwave bridge c i r c u i t . 27 polarized test signal is applied to the sample under test using pyramidal horn antennas separated by approximately 55 cm. The two channels are recombined by a 6 dB directional coupler and the signals are fed into a Microwave Associates 1N23C diode detector. Various isolators placed in the circ u i t minimize the effect of mismatches and prevent the sample's reflected signal from entering the system and affecting the measurements. Placing isolators in the circ u i t minimizes channel interact ion[11]. A l l directional couplers are of the high directivity type (directivity exceeding 40 dB) to minimize passage of unwanted signals through the system. 3.6.2. Data Acquisition Automated signal level monitoring and control of the attenuator and phase shifter are performed by an Intel 8088 based microcomputer operating at 4.77 MHz. The DC diode detector response is amplified and then digitized by an 8-bit analog to digital (A/D) converter. Two separate amplifier modes exist. A low gain amplifier (5X) operates when the detector output is high (20 mV - 1V) and a higher gain (50X) amplifier operates when the output is low (0 - 20 mV) because of the non-linear characteristics of the crystal diode. When the microwave signal is high, the signal output changes rapidly but higher resolution is required when the signal level is low to locate a signal null 28 for bridge balancing. The magnitude of the mixer output signal is indicated to the microcomputer via a status bit and enables selection of the appropriate gain. Details of the A/D converter board are given in Appendix C. The attenuator, phase shifter, 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 bus (Appendix D). 3 .6 .3 . Bridge B a l a n c i n g A l g o r i t h m An 8088 assembly language program performs A/D sampling of the amplified detector output and controls attenuation and phase shift settings to locate a null. The computer alternately adjusts the two control devices until the detector signal level is minimized. I n i t i a l l y the attenuator is set at 0 dB while the phase shifter is scanned from 0° to 360° in 10° increments. The phase setting that produces a minimum detector signal level serves as a f i r s t phase approximation. The attenuator is then scanned from 0 dB to 20 dB in 1.0 dB increments to search for the minimum detector signal level. The two devices are then alternately scanned near the f i r s t approximation points to search for an absolute minimum level. The search is complete when the two control devices do not change their settings between successive scans. The exact transmission coefficient for each device is determined from a look-up table of calibration values 29 at the measuring frequency stored in memory (Appendix F). This iterative procedure is necessary because the phase shifter's insertion loss varies with i t s phase setting and the attenuator's phase shift varies with i t s attenuation setting. If the di g i t a l attenuator were phase-free and the d i g i t a l phase shifter had a constant insertion loss, the bridge could be balanced with a single iteration. Details of the 8088 assembly language balancing program are provided in Appendix E. 3.7. MEASUREMENT SYSTEM PERFORMANCE 3.7.1. A c c u r a c y To test the system's accuracy, various measurements were performed on several slabs of homogeneous dielectric test samples. The results are listed in Table 3.1. The dielectric constants measured using the Roberts-Von Hippel method [16] are enclosed for comparison. The dielectric 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 permittivity estimates. The resolution of the attenuator and phase shifter are limited by the size of their least significant bits. The smallest attenuator step size is 0.25 dB and the smallest phase shifter step size is 1.4°. Errors of ±0.5 dB result in the estimate of AA 30 Material Kcm) AA(dB) polystyrene 1 .65 1 .4 expanded polystyrene 2 .50 1 .3 styrofoam 10 .30 0.0 polythene 1 .68 0.5 polythene 1 .38 1 .0 polythene 0 .98 0.1 polythene 0 .50 1 .3 wood (dry) 2 .94 3.9 e r i tan5 97.8 2 .59(2 .59) 0 .028(0. 002) 1 30.6 2 .03(1 .86) 0 .019(0. 004) 20.7 1 .03(1 .07) 0 .000(0. 023) 1 02.7 2 .28(2 .36) 0 .003(0. 003) 91 .0 2 .33(2 .36) 0 .031(0. 003) 61 .9 2 .30(2 .36) 0 .006(0. 003) 31.1 2 .28(2 .36) 0 .088(0. 003) 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 er'(min) e '(max) 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 0.054 0.067 Table 3.2 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 listed in Table 3.2. The errors in AA are significant 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 affect the dielectric constant estimates for a lossier material such as wood. AA for a 4 cm thick wood sample typically l i e s between 2 dB and 20 dB and A0 typically lies between 80° and 640° so the relative errors in estimated e 1 and tan5 due to device resolution are not as significant. Errors also arise because the wave incident on the board deviates slightly from an ideal plane wave. Data presented in Chapter 4 indicate that these deviations in the permittivity measurements do not affect 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 null point using a 4.77 MHz 8088 microprocessor in an IBM PCjr microcomputer. Approximately three iterations are required to null the bridge when no sample is present and approximately five 33 i t e r a t i o n s are required when wood i s present. This i n t e r v a l corresponds to a measurement resolution of 25 cm i f a sample moves through the test section at 5 m/s. 3 . 7 . 3 . Dynamic Range At high attenuation l e v e l s , the low signals in both channels are d i f f i c u l t to detect. The microwave bridge c i r c u i t i s capable of accurately measuring attenuations up to 22 dB before the signal l e v e l at the detector i s too low to balance. The system balances when AA i s between 22 dB and 27 dB but the balance points are not accurate and repeatable. At higher attenuations, the c i r c u i t i s unable to balance. 4. E X P E R I M E N T A L P R O C E D U R E S A N D R E S U L T S 4.1. E X P E R I M E N T A L P R O C E D U R E S The microwave bridge cir c u i t detailed in Chapter 3 was used to measure attenuation and phase shift 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 shifter in the reference branch of the microwave bridge c i r c u i t . The microwave source is modulated by a 1 KHz signal and an analog HP 415E standing wave indicator monitors the output signal level of the detector. Bridge balancing is performed by manually adjusting the control devices until a voltage null is visually identified at the indicator. Microwave measurements were performed on wood samples of a particular species having differing specific gravities and moisture contents. Two polarizations were used: transverse and longitudinal. The electric f i e l d is oriented perpendicular to the grain direction for transverse polarization and the electric f i e l d is oriented parallel to the grain direction for longitudinal polarization as shown in Fig. 4.1. The effects of small deviations in the polarization are shown in Fig. 4.2. Angular deviations of less than 15° in the polarization do not 34 r 2 0 0 00 c ~o 3 C CD Angle (degrees) F i g . 4.2 Microwave measurements as a function of grain angle. 36 significantly affect the measured quantities so naturally occurring small slope of grain angles do not affect the measurements. Approximately 100 samples of clear, knot-free Hemlock having an approximate size of 23 cm x24 cm x 4 cm and varying specific gravities 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 polarizations. The samples were air-dried 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 until the samples did not lose any weight between dryings in the microwave oven. At this point the pieces were considered oven dry. The specific 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 linearly 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 typical specific gravity. The anisotropic dielectric property of wood is 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 is 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 is so strongly bonded to the wood substance that the molecules have limited mobility. Attenuation is minimal since minimal energy is 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 its weaker bonding. This behaviour was observed for both polarizations. Anisotropy in phase shift measurements was also observed. 350-1 100-50-HEMLOCK frequency = 10.19 GHz tranverse polarization specific gravity=0.38 10 15 20 Moisture Content (%) 25 Legend o samplel » sample2 • sample3 Fig. 4.3 Attenuation and phase shift as a function of moisture content for a typical specific gravity. Hemlock: transverse polarization. 40 39 450 : 400-350-300 : 250 : 200-150-; 100 : 50 J 0-HEMLOCK frequency=10.19 GHz longitudinal polarization specific gravity=0.38 o 1 8 4 a 10 15 20 Moisture Content (%) 25 Legend o samplel o sample2 • sample3 F i g . 4.4 A t t e n u a t i o n and p h a s e s h i f t a s a f u n c t i o n o f m o i s t u r e c o n t e n t f o r a t y p i c a l s p e c i f i c g r a v i t y . H emlock: 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 S p e c i f i c G r a v i t y on AA and A# Figs. 4.5 and 4.6 show the variation of AA and A0 with moisture content for various specific gravities. As specific gravity increases, AA and A0 tend to increase for a particular moisture content. Figs. 4.7 and 4.8 explicitly illustrate the effect of specific gravity for various moisture contents. 4.2.3. E f f e c t of M o i s t u r e Content 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 is shown in Figs. 4.9 and 4.10 for various specific gravities. The dielectric constant and loss tangent increase with moisture contents for both polarizations as expected. 4.2.4. E f f e c t of S p e c i f i c G r a v i t y on D i e l e c t r i c C o n s tant Figs. 4.11 and 4.12 show the variation of e * and tan5 with specific gravity for various moisture contents. The effect of specific gravity on permittivity is not as significant as the effect of moisture content. These relationships between the dielectric and physical properties of wood show similar trends to those obtained by other researchers using lower frequencies and different measurement techniques!17,23,24]. However, these measurements used air and oven dried wood having a moisture gradient, representative of 25 41 HEMLOCK transverse polarization 5 10 15 20 Moisture Content (%) 25 Legend A sg=0.36 * sg-0-38 • 59=0.43 B sg=0.50 a sg=0.54 x sg=0.63 500 HEMLOCK transverse polarization 5 10 15 Moisture Content (%) Legend A sg=0.36 x sg=0.38 • sg=0.43 H sg=0.50 s sg=0.54 F i g . 4.5 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 v a r i o u s 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 . HEMLOCK longitudinal polarization -i 1 1 r- -i 1 1 1 1 1-5 10 15 20 Moisture Content (%) 25 L e g e n d A sg=0.36 x sg=0.38 • sg=0.43 H sg=0.50 ffi sg=0.54 * sg=0.63 700-600 500 4 0 0 -H E M L O C K longitudinal polarization 100-10 -i—i—i—[— 15 20 Moisture Content (%) 25 L e g e n d A sg=0.36 x sg=0.38 • sg=0.43 H sg-0.50 ffi sg=0.54 x s g f O ^ ^ 4.6 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 v a r i o u s 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 p o l a r i z a t i o n . CQ 3 , C o c 25 20-15-10-5-HEMLOCK transverse polarization —1—1—1—1—1—1—1—r-35 0.40 T-r-r-0.45 T 1 1 [ T-0.50 1 1 ' 1 1 1 1 1 1 1 1 1 0.55 0.60 0.65 Specific Gravity Legend A mc=05 x mc=6% • mc=12% H mc=18% CO 500 400-300-CO <x> Vi D SI CL 200-HEMLOCK transverse polarization Legend A 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 Fig. 4.7 Attenuation and phase shift as a function of specific gravity for various moisture contents. Hemlock: transverse polarization. Fig. 4.8 Attenuation and phase shift as a function of specific gravity for various moisture contents Hemlock: longitudinal polarization. 45 HEMLOCK transverse polarization 3.5-C _o (/> c o CJ o o b 2.5-" l — 1 — ' 5 10 15 20 Moisture Content (%) 25 Legend A sg=0.36 x sg=0.38 • sg=0.43 B sg=0.50 S sg=0.54 x sg=0.63 0.30 0.25-H E M L 0 C K transverse polarization 0.00 -1 1 | 1 I I 1 1 5 10 15 I 20 Moisture Content (%) -i 1 1 j 25 Legend A sg=0.36 x sg=0.38 • sg=0.43 8 sg=0.50 B sg=q.54 x sg=0.63 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 . content 46 HEMLOCK longitudinal polarization i 1 1 r~ 5 10 15 20 Moisture Content (%) i 25 Legend A sg=0.36 sg =0.38 sg =0.43 sg =0.50 =0.54 sg =0.63 0.5-HEMLOCK longitudinal polarization 5 10 15 20 Moisture Content (%) Legend A sg=0.36 x sg=0.38 • sg=0.43 B sg=0.50 a sg=0.54 Fig. 4.10 Permittivity as a function of moisture content for various specific gravities. Hemlock: longitudinal polarization. 3.5 c c o o -5? 2 1.5-HEMLOCK transverse polarization - i — | — i — i — i — r -0.35 0.40 0.45 0.50 0.55 Specific Gravity Legend A mc=0% x mc=6% O mc=12% B mc=18% 1 I 1 1 1 1 I 0.60 0.65 0.30-1 0.25--£ 0.20 Ui c £ 0.15 cn in O 0.10-1 0.05 0.00 HEMLOCK transverse polarization T 1 1 1 1 1 1 1 1 J 1-0.35 0.40 0.45 Legend A mc=0% x mc=6% • mc=12% B mc=18% 1 I ' 1 1 ' I 1 ' 1 1 I 1 ' 1 1 I 0.50 0.55 0.60 0.65 Specific Gravity ig. 4.11 Permittivity as a function of specific gravity for various moisture contents. Hemlock: transverse polarization. Fig. 4.12 Permittivity as a function of specific for various moisture contents. Hemlock: longitudinal polarization. gravity 49 industrial conditions, while other researchers used conditioned wood with uniform moisture content. Lint 10] did not find a correlation between permittivity and specific gravity at 1 KHz. At this lower frequency, interfacial, dipolar, atomic, and electronic polarizations contribute to the permittivity. Hence, small impurities in wood and slight variations in chemical composition affect the permittivity more than differences in specific gravity do. Since only atomic and electronic polarizations contribute at microwave frequencies, the effects of impurities on the dielectric 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 specific gravities (0.39, 0.40, and 0.54) were soaked and partially air 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 solid state temperature transducer penetrating about 5 cm into the wood. Results are shown in Figs. 4.13 to 4.15. Both AA and A0 increase as the temperature increases. The dependence of e ' and tan5 on temperature for one sample is illustrated in Fig. 4.16. For green pieces with moisture contents above the fiber saturation point, discontinuities in AA and A# were observed at Fig. 4.13 Attenuation and phase shift as a function o temperature for various moisture contents. Specific gravity=0.39. Hemlock: transverse polarization. Fig. 4.14 Attenuation and phase shift as a function of temperature for various moisture contents. Specific gravity=0.40. Hemlock: transverse polarization. Fig. 4.15 Attenuation and phase shift as a function of temperature for various moisture contents. Specific gravity=0.54. Hemlock: transverse polarization. 3-| s p e c i f i c g r a v i t y = 0 . 4 0 53 c o vt c o C J o TJ <x> a> b 2 . 5 -1.5-- 1 5 - 10 1 i 1 - 5 10 Temperature (°C) 15 20 Legend 0 mc=39.5% » mc=17.9% * mc=12.3% 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. S p e c i f i c gravity=0.40. Hemlock: transverse 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 liquid water. For moisture contents below the fiber saturation point, there are no discontinuities at 0°C indicating that bound water does not undergo a phase change at the freezing point of water. This is illustrated by the steady continuous variation in AA and A<f> as the temperature passes through the freezing point of pure water. AA and A<j> appear to vary linearly with temperature for various bound moisture contents. The slopes are preserved for different moisture contents and for different specific gravities. Therefore, values of measured AA and A0 at any temperature can be corrected to other 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 specific gravities are shown in Figs. H.1 to H.4 for transverse polarization. Each specific gravity occupies a unique region on the plot. Similarly, 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 specific gravities and constant moisture contents are combined and displayed in Fig. 4.17 for transverse polarization and in Fig. 4.18 for longitudinal polarization at room temperature. 4 5 0 4 0 0 3 5 0 -3 0 0 -2 5 0 2 0 0 150 100-1 5 0 H E M L O C K f requency t r a n s v e r s e th ickness 0 2 4 6 8 10 12 14 16 18 2 0 2 2 24 Attenuation (dB) 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 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 i [ i i i i | i i i i 0 5 10 15 20 2 5 3 0 3 5 4 0 45 5 0 5 5 Attenuation (dB) Fig. 4.18 Phase shift as a function of attenuation for various specific gravities and moisture contents. Hemlock: longitudinal polarization. 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 specific gravity and moisture content is orderly. At a fixed temperature and for either polarization, there is a unique combination of specific 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 specific gravity with each possible combination of measured attenuation and phase shift at room temperature. The table is stored in the microcomputer's memory and is referred to when the bridge successfully balances. The effect of temperature can be compensated for by scaling AA and A0 to the calibration table temperature prior 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 their actual values. From studying Figs. H.5 to H.8, the moisture content estimates are accurate to approximately ±3.0%. A similar accuracy is obtained for longitudinal polarization. Table 4.1 l i s t s the specific gravity results obtained for Hemlock with A c t u a l Low S p e c i f i c E s t i m a t e G r a v i t y 0.33 0.36 0.33 0.37 0.33 0.38 0.36 0.39 0.34 0.40 0.36 0.43 0.38 0.44 0.40 0.45 0.40 0.47 0.43 0.49 0.44 0.50 0.45 0.51 0.48 0.52 0.47 0.53 0.50 0.54 0.49 0.56 0.54 0.60 0.58 0.63 0.58 High Max E s t i m a t e D e v i a t i o n 0.36 ± 0 . 0 3 0.37 ± 0 . 0 3 0.39 ± 0 . 0 4 0.43 ± 0 . 0 5 0.42 ± 0 . 0 5 0.42 ± 0 . 0 4 0.47 ± 0 . 0 5 0.48 ± 0 . 0 4 0.48 ± 0 . 0 5 0.50 ± 0 . 0 4 0.54 ± 0 . 0 5 0.53 ± 0 . 0 5 0.56 ± 0 . 0 5 0.57 ± 0 . 0 5 0.58 ± 0 . 0 5 0.57 ± 0 . 0 5 0.57 ± 0 . 0 2 0.63 ± 0 . 0 3 0.64 ± 0 . 0 5 Max % D e v i a t i o n 9.1 8.3 10.8 13.2 12.8 10.0 11.6 9.1 11.1 8.5 10.2 10.0 9.8 9.6 9.4 9.3 3.6 5.0 7.9 T a b l e 4.1 S p e c i f i c g r a v i t y e s t i m a t i o n range of Hemlock: t r a n s v e r s e p o l a r i z a t i o n . A c t u a l Low S p e c i f i c E s t i m a t e G r a v i t y 0.33 0.36 0.33 0.37 0.36 0.38 0.33 0.39 0.36 0.40 0.36 0.41 0.37 0.43 0.36 0.44 0.38 0.45 0.38 0.47 0.41 0.48 0.41 0.49 0.44 0.50 0.43 0.51 0.43 0.52 0.47 0.53 0.51 0.54 0.50 0.56 0.54 0.60 0.58 0.62 0.60 0.63 0.60 0.64 0.60 High Max E s t i m a t e D e v i a t i o n 0.36 ± 0 . 0 3 0.39 ± 0 . 0 3 0.44 ± 0 . 0 7 0.41 ± 0 . 0 5 0.44 ± 0 . 0 5 0.44 ± 0 . 0 4 0.43 ± 0 . 0 4 0.47 ± 0 . 0 7 0.52 ± 0 . 0 8 0.51 ± 0 . 0 7 0.52 ± 0 . 0 6 0.53 ± 0 . 0 7 0.53 ± 0 . 0 5 0.54 ± 0 . 0 7 0. 56 ± 0 . 0 8 0.56 ± 0 . 0 5 0.60 ± 0 . 0 7 0.60 ± 0 . 0 6 0.58 ± 0 . 0 2 0.62 ± 0 . 0 2 0.63 ± 0 . 0 2 0.64 ± 0 . 0 3 ± 0 . 0 4 Max % D e v i a t i o n 9.1 8.3 18.9 13.2 12.8 10.0 9.8 16.3 18.2 15.6 12.8 14.6 10.2 14.0 15.7 9.6 13.2 11.1 3.6 3.3 3.2 4.8 6.7 T a b l e 4.2 S p e c i f i c g r a v i t y e s t i m a t i o n range of 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 . 60 transverse polarization and table 4.2 l i s t s results with longitudinal polarization. The transverse specific gravity estimates are assessed to be approximately accurate to ±0 .05 and the longitudinal estimates are accurate to approximately ± 0 . 0 8 . 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 Fir were electronically measured using transverse polarization. The microwave properties show similar variation to Hemlock as illustrated 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 specific gravities and moisture contents are shown in Figs. H.14 to H.19. These results, summarized in Fig. 4.19 for room temperature, are also suitable for a grading algorithm. Their accuracies are studied by comparing the possible estimation ranges due to scatter for specific 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 shift as a function of attenuation for various specific gravities and moisture contents. Douglas F i r : transverse polarization. Room Temperature. A c t u a l Low S p e c i f i c E s t i m a t e G r a v i ty 0.38 0.41 0.38 0.42 0.38 0.43 0.42 0.44 0.42 0.45 0.42 0.47 0.46 0.48 0.47 0.49 0.44 0.51 0.49 0. 52 0.51 0.54 0.52 0. 55 0.54 0.57 0.56 0.58 0.57 0.61 0.58 H i g h Max E s t i m a t e D e v i a t i o n 0.40 ± 0 . 0 2 0.43 ± 0 . 0 3 0.45 ± 0 . 0 4 0.45 ± 0 . 0 2 0.48 ± 0 . 0 4 0.47 ± 0 . 0 3 0.51 ± 0 . 0 4 0.52 ± 0 . 0 4 0.51 ± 0 . 0 5 0.56 ± 0 . 0 5 0.57 ± 0 . 0 5 0.56 ± 0 . 0 2 0.57 ± 0 . 0 2 0.58 ± 0 . 0 1 0.61 ± 0 . 0 3 ± 0 . 0 3 Max % D e v i a t ion 5.3 7.3 9.5 4.7 9.1 6.7 8.5 8.3 10.2 9.8 9.6 3.7 3.6 1.8 5.2 4.9 T a b l e 4.3 S p e c i f i c g r a v i t y e s t i m a t i o n range of 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 . 5. CONCLUSIONS AND SUGGESTIONS FOR IMPROVEMENT 5.1. CONCLUSIONS The objectives of this thesis have been met; in particular: 1. A measurement system employing a microwave bridge circuit and the free-space technique was designed and tested which allows the rapid, non-contact measurement of permittivity. A microcomputer performs automatic measurements by sampling the balance signal and adjusting a logic-controlled attenuator and a logic-controlled phase shifter to balance the bridge. The permittivity estimates is 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 is measured. 2. The dielectric properties of wood were measured to determine a dependence on its physical properties. The dependence of attenuation, phase shift, dielectric constant, and loss tangent on specific 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 calibration curves were created for the two species to estimate specific gravity and moisture content from attenuation and phase shift measurements. The microwave 63 64 p r o p e r t i e s e x h i b i t a p r e d i c t a b l e behaviour with temperature so c o r r e c t i o n s to measured AA and A0 can be a p p l i e d when gra d i n g wood at d i f f e r e n t temperatures. 4. The accuracy of the technique was assessed to be approximately ±0.05 f o r s p e c i f i c g r a v i t y measurement and approximately ±3.0% f o r bound moisture content measurement us i n g t r a n s v e r s e p o l a r i z a t i o n . Using l o n g i t u d i n a l p o l a r i z a t i o n , the s p e c i f i c g r a v i t y accuracy i s assessed to be approximately ±0.08 and approximately ±3.0% f o r moisture c o n t e n t . The measurement system would be s u i t a b l e f o r use i n a m i l l environment. I t i s simple to operate and c o u l d c o n t i n u o u s l y monitor microwave parameters with some m o d i f i c a t i o n s . The system c o n t a i n s no moving p a r t s and can be made rugged to withstand i n d u s t r i a l c o n d i t i o n s . 5.2. LIMITATIONS OF THE MEASUREMENT SYSTEM 1. The present system r e q u i r e s approximately 50 ms to o b t a i n a s i n g l e reading f o r a s t a t i c sample. A f a s t e r microprocessor and f a s t e r a n a l o g / d i g i t a l c o n v e r t e r can be used to reduce the b a l a n c i n g time. With p r e s e n t l y a v a i l a b l e h i g h speed m i c r o p r o c e s s o r s ( i . e . 20 MHz) and a f a s t e r a n a l o g / d i g i t a l c o n v e r t o r ( i . e . 10 M S ) c o n v e r s i o n time, the balance time can be reduced to approximately 10 msec. T h i s would 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 restricting the i n i t i a l scanning range when grading clear, knot-free wood because the specific 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 range. 2. The Varian X-13 klystron in the present experimental configuration can provide sufficient power (=* 300 mW CW) for accurate measurements up to 22 dB attenuation. At higher attenuations, the detector signal in the measuring channel is sufficiently small (=*-16 dBm) that a balancing null is d i f f i c u l t to accurately locate with the electronic system. The system has sufficient dynamic range to measure the attenuation and phase shift for a l l specific gravities and bound moisture contents using transverse polarization on 2-inch nominal dimension clear knot free wood. The klystron power source can be replaced by a solid state source of higher power (^ 1 W CW) to provide greater frequency stability, 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 typical specific gravities and bound moisture contents. If measurements are 66 made using both polarizations, two separate estimates of specific 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 dielectric properties and the instrumentation used: 1. Moisture content gradients and high moisture pockets can form in the samples during air 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 dielectric behaviour of uniformly dried wood, each sample should be slightly dried and sealed air 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 industrial kiln drying. 2. The presence of volatile extractives such as resins and oi l s in wood affect the moisture constant estimate. Oven drying causes these volatile substances to evaporate and introduces errors in the oven dry measuring methods used. Alternative 67 methods for accurately measuring moisture content such as distillation[1] can be used. No consideration is given to the type of cut in the samples measured. A test sample can contain several zones of differing specific gravities because specific gravity can vary throughout a tree. To investigate the exact dependence of dielectric properties on cut geometry, different cuts should be analyzed separately. However, a l l cut types are encountered in mills and no on-line grading system separates wood into different cuts prior to grading. The effects of 1 - 3 were minimized in this 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 is representative of actual industrial conditions. The present system measures stationary wood but a system measuring moving wood would require a position monitoring sensor. Digital 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 specific gravity, moisture content, slope of grain, and knot locations have been measured along its length. For the long term, the system can be miniaturized by using microstrip components to replace the waveguide. Microstrip circuitry is 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] Collin, R.E., "Field 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, Vol. 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, Vol. 15, No.2, pp. 51-56, February, 1965. [ 5] James, W.L., "Dielectric Behaviour of Douglas Fir 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, Vol. 34, No. 11/12, pp. 59-64, Nov./Dec, 1984. [ 7] Kharadly, M.M.Z., "Microwave Diagnostics for Stress-Rating of Dimension Lumber", Fifth Nondestructive Testing of Wood Symposium, Sept. 9-11, 1985. Washington State University, Pullman, Washington, 1985. 69 70 [ 8] Kraszewski, A., "Microwave Instrumentation for Moisture Content Measurement", J. of Microwave Power, 8(3/4), 1973. [ 9] Kraszewski, A., "Microwave Aquametry — A Review", J. of Microwave Power, 15(4), 1980. [10] L i n , R.T., "Review of the D i e l e c t r i c Properties of Wood and Cellulose", Forest Products Journal, Vol. 17, No. 7, pp. 61-66, July, 1967. [11] Magid, M., "Precision Microwave Phase S h i f t Measurements", IRE Transactions on Instrumentation, Vol. 1-7, pp 321-331, December 1958. [12] Panshin, A.J., and de Zeeuw, C. Textbook of Wood Technology, Fourth Edition. McGraw-Hill, 1980. [13] Peterson, R.W., "The D i e l e c t r i c Properties of Wood", Forest Products Laboratories of Canada Technical Note No. 16, Cat. No. R57-16, 1960. [14] Purslow, D.F., "The Use of a Microwave Moisture Meter for Studying Moisture Changes in Timber", J . of the Insti t u t e of Wood Science, Vol. 5(4) #28, pp. 40-46, 1971. [15] Redheffer, R.M., "The Measurement of D i e l e c t r i c Constants", Techniques of Microwave Measurements, Ch. 10, C G . Montgomery, Ed. New York: McGraw-Hill, 1947. [16] Roberts, S, and von Hippel, A., "A New Method for Measuring D i e l e c t r i c Constant and Loss in the Range of Centimeter Waves", J . of Applied Physics, Vol. 17, pp. 610-616, July, 1946. 71 [17] Skaar, C., "The Dielectric 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., "Dielectric Properties of Douglas Fir 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 Heikkila, 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 Division. Published by American Society of C i v i l Engineers, 1975. [23] Yavorsky, J.M., "A Review of Electrical 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 is obtained from a wave transmission matrix analysis[2]: medium 1 c 1 b, medium 2 c 2 b, A 1 1 A , 2 A 2 1 A 2 2 C 2 b 2 A ! j - 1 A I 2 " P 1 A 2 , = R , T,2 A 2 2 = T 2 i " R i R ; where: Ty2=transmission coefficient from medium 1 to medium 2 T 2 1 transmission coefficient from medium 2 to medium 1 72 73 R,=reflection coefficient in medium 1 at interface R 2=reflection coefficient in medium 2 at interface If z=impedance of medium 2 normalized to impedance of medium 1, then the relationship i s : c i z+1 z-1 c2 2z 2z b, z-1 z+1 b 2 2z 2z For a dielectric slab of width 1 and complex impedance z, the wave transmission matrix is 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 / medium 3 //////////// c, //////////// c 3 > //////////// > //////////// //////////// //////////// b, //////////// b 3 < //////////// < //////////// //////////// 74 C 1 b, z+1 2z z-1 2z z-1 2z z+1 2z 0 0 e - 7 l z+1 -(z-1) 2 2 (z-1) (z+1) which g i v e s : C 1 s i n h 7 l ( z 2 + 1 ) + c o s h 7 l s i n h 7 l ( 1 - z 2 ) c 3 2z 2z b, s i n h 7 l ( z 2 - 1 ) - s i n h 7 l ( z 2 + 1 ) + c o s h 7 l b 3 2z 2z T h e r e f o r e , the 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 1 to medium 3 i s : T 1 3 = 1 = 4ze - 7 l A,, ( Z + 1 ) 2 - ( Z - I ) 2 e " 2 7 1 APPENDIX B PERMITTIVITY CALCULATION FROM FREE SPACE MEASUREMENTS The accompanying Fortran program calculates the complex permittivity from microwave bridge measurements. The material is assumed to have a uniform dielectric constant throughout i t s volume. The effects of interface reflections are incorporated into the complex transmission coefficient. A f i r s t order approximation to e' and tan8 is 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 is formed in the e' and tan5 axes. The transmission coefficients at eight neighbouring points are evaluated using Eq. 8 and the point whose transmission coefficient deviation from the measured value is minimum serves as the new guess point. This process is repeated until the updated guess point is unchanged between successive iterations. -2 The value of e' is accurate to ±10 and tan5 is accurate to ±10 - 3. The complex propagation constant of a plane wave in the dielectric medium i s : 7=J0rV[e' (1-Jtan6)3 75 76 1 C THIS PROGRAM INPUTS THE EXPERIMENTAL ATTENUATION AND PHASE 2 C MEASUREMENTS AND COMPUTES THE CORRESPONDING COMPLEX PERMITTIVITY 3 COMMON /BLK t/ WIDTH,BETAF 4 WAVEL'O.029426 5 P I 'S .1415926 6 WIDTH-0.01300 7 BETAF = 2.0*PI /WAVEL 8 C 9 C INPUT EXPERIMENTAL DATA 10 C ATTFSP'FREE SPACE ATTENUATION 11 C PHASP'FREE SPACE PHASE SHIFT 12 C ATTWO'WOOD ATTENUATION ; PHAWD'WOOD PHASE SHIFT 13 C 14 READ(5,499) WIDTH 15 READ(5.500) ATTFSP 16 READ(S.510) PHASP 17 REA0(5,50O) ATTWD 18 REA0(5.51O) PHAWD 19 499 FORMAT( F 10. 5) 20 500 F0RMAT(F5.2) 21 510 FORMAT(F5.1) 22 C ECHO INPUT 23 WRITE(6,799) WIDTH 24 WRITE(6.800) ATTFSP 25 WRITE(6.810) PHASP 26 WRITE(6,820) ATTWD 27 WRITE(6.830) PHAWD 28 C 29 799 F0RMAT( 'SAMPLE THICKNESS 3 ' .F 1 1 . 7 . ' CM') 30 800 FORMAT*'FREE-SPACE ATTENUATION BALANCE' ' , F 5 . 2 , ' DB' ) 31 810 FORMAT(' FREE-SPACE PHASE BALANCE = ' . F 5 . 1, ' DEGREES') 32 820 FORMAT(' WOOD ATTENUATION 8ALANCE- ' . F 5 . 1 . ' DEGREES') 33 830 FORMATC WOOD PHASE 8ALANCE" ' . F 5 . 1 . ' DEGREES') 34 DELATT=EXP(- 1.0*(ATTWD-ATTFSP)/20.O'ALOGI 10.0)) 35 DELWD»ATTWD-ATTFSP 36 C 37 DELPH'PHAWD-PHASP 38 C OUTPUT RELEVANT CALCULATIONAL DATA 39 WRITE(6,840) DELWD.DELATT 40 840 FORMAT(' WOOD ATTENUATION' ' , F 5 . 2 , ' DB ' , ' OR ' . F 5 . 2 ) 41 WRITE(6,850) DELPH 42 850 FORMAT(' ACTUAL PHASE SHIFT = ' , F 6 . 1 . ' DEGREES') 43 C CONVERSION TO RADIANS 44 D E L P H ' D E L P H / 1 8 0 . 0 » P I 45 C OBTAIN SOLUTION 46 CALL SOLVE(DELATT.DELPH.E1.TANDEL) 47 WRITE(6,550) 48 550 F O R M A T ! / / . ' * »»» EXECUTION TERMINATED « • * • ' ) 49 STOP 50 END 51 C 52 C A SUBROUTINE TO DETERMINE THE EXACT VALUE OF E ' AND LOSS TANGENT 53 C FROM ATTENUATION ANO PHASE SHIFT MEASUREMENTS 54 C 55 SUBROUTINE SOLVE(DELATT,DELPH,E1,TANDEL) 56 COMPLEX TRANS 57 COMPLEX TMAT(5) 58 DIMENSION EPS 1(5).TAND(5).DMAG(5).DANG(5) 59 COMMON / B L K 1 / WIDTH,BETAF 60 MAXNUM'100 61 AIRPH'BETAF'WIDTH 62 ARGANG'DELPH+AIRPH 63 COSVAL'COS(ARGANG) 64 SINVAL = SIN ( ARGANG) 65 C GET INITIAL APPROXIMATION 66 CALL GUESSIDELATT,DELPH,E1.TANDEL) 67 C ECHO INITIAL APPROXIMATION 68 WRITE(6,860) E1,TANDEL 69 860 FORMAT(/ / . 'APPROX E1» ' . F 8 . 4 , ' APPROX TANDEL" ' . F S . 4 . / > 70 ' C CALC EXACT VALUE BY MINIMIZATION OF DEVIATIONS AT NEIGHBOURING 71 C POINTS. NEGLECT DEVIATION ANGLE MEASUREMENTS 72 C ASSIGNING VALUES FOR E l AND LOSS TANGENT AT NEIGHBOURING POINTS 73 NCOUNT'O 74 90 CONTINUE 75 EPS 1(1)"E1 76 TAND(1)-TANDEL 77 EPS1(2) 'E1+0.001 78 TANO(2)'TANOEL 79 EPS1(3)"E1 80 TAN0(3)-TANOEL*O.O01 81 EPS1(4 ) 'E1 -0 .001 82 TAND(4)'TANDEL 83 EPS1(5) 'E1 84 TAND(5) 'TANDEL-0.001 85 C CALCULATION OF TRANSMISSION COEFFICIENTS FOR NEIGHBOURING POINTS 86 DO 100 ICNT*1.5 87 PERM1-EPSKICNT) 88 TANN'TANDtICNT) 89 C EVALUATE COMPLEX TRANSMISSION COEFFICIENT 90 TMAT(ICNT)"TRANS(PERM 1.TANN) 91 TR t tREAL(TMAT(ICNT)) 92 TI»AIMAG(TMAT(ICNT)) 93 C EVALUATION OF REAL ANO IMAGINARY COMPONENT DEVIATIONS 94 HOLDR=TR-DELATT*COSVAL 95 C NEGATIVE SIN TERM DUE TO THE EXP(-J«B'L) 96 HOLDI nTI+DELATT' SINVAL 97 IF (ICNT.NE.1) GOTO 99 98 WRITE(6.690) NCOUNT,PERM1,TANN.TR.TI,HOLDR.HOLDI 99 690 F0RMAT(I4.2X.F7.3.2X.F7.3,3X,F10.6.3X.F10.6.3X.F11 7.3X.F11.7) 100 99 CONTINUE 101 C EVALUATION OF THE DEVIATION MAGNITUDE 102 DMAG(ICNT)=SQRT(H0LDR*H0LDR+HOLDI*HOLDI) 103 C EVALUATION OF THE DEVIATION ANGLE 104 DANG(ICNT)=ANGTAN(HOLDR.HOLDI) 105 100 CONTINUE 106 C SELECT POINT HAVING MINIMUM DEVIATION 107 C TEMPORARILY ASSUME CENTRAL POINT (IVAL) HAS MINIMUM DEVIATION 108 RMIN-OMAGd) 109 IVAL-1 1 10 DO 110 JCNT=1.5 111 IF (OMAG(JCNT) LE RMIN) IVAL-vJCNT 112 110 CONTINUE 113 IF (IVAL.EQ.1) GOTO 200 114 NCOUNT-NCOUNT+1 115 E1-EPS1(IVAL) 116 TANDEL-TANO(IVAL) 117 IF (NCOUNT.LE.MAXNUM) GOTO 90 118 WRITE(6,700) 119 700 FORMAT('MAXIMUM NUMBER OF ITERATIONS EXCEEDED') 120 200 CONTINUE 121 WRITE(6,710) EPS 1( 1),TAND( 1) '22 7 10 FORMAT*//,'VALUE OF E1=',F9.5.3X,'VALUE OF LOSS TANGENT*' F9 5) 123 WRITE(6,720) DMAGI1),DANG(1) 124 720 FORMAT)/, MAGNITUDE DEVIAT 10N=' .F9.5, ' ANGULAR DEVIATION-' F9 5) 125 WRITE(6,730) 126 730 FORMAT!'SUCCESSFUL SOLUTION --> MAGNITUDE DEVIATION MINIMIZED') 127 RETURN 128 END 129 130 C A PROGRAM TO FINO THE FIRST ORDER APPROXIMATION TO E' ANO E' ' 131 C 132 SUBROUTINE GUESS(OELATT.DELPH.E1.TANDEL) '33 COMMON /BLK1/ WIDTH,BETAF 134 RTE 1 * 1 . 0+DELPH/( BETAF * WIDTH ) 135 E1=RTE1*RTE1 '36 ARG1*(DELATT*RTE 1 *( 1.O/RTE1+1.0)*«2. )/4.0 137 ARG2-(-1 0*BETAF*RTE1«WIDTH)/2.0 '38 TANDEL=ALOG(ARG1)/ARG2 139 RETURN 140 END 141 C '42 C A FUNCTION TO EVALUATE THE ARCTANGENT OF A SPECIFIED ANGLE 143 C GIVEN ITS OPPOSITE AND ADJACENT SIDES 144 145 FUNCTION ANGTAN(X.Y) 146 PI>3.14159 147 C ANGLE FOUND IN QUADRANT 1 '48 IF((X.GE.0).AND.(Y GE.0)) ANGLE=ATAN2(Y.X) 149 C ANGLE FOUNO IN OUADRANT 2 '50 IF<(X LE.0).AND.(Y GE.0)) ANGLE=ATAN2(Y,X)+PI '51 C ANGLE FOUND IN OUADRANT 3 152 IF((X.LE.O).AND.(Y.LE.0)) ANGLE-ATAN2(Y.X)+PI 153 C ANGLE FOUND IN OUADRANT 4 154 IF((X GE.0).ANO.(Y.LE.0)) ANGLE 3ATAN2(Y,X)+2.0*PI 155 C CONVERSION TO DEGREES AND RETURN 156 ANGTAN-ANGLE/PI*180.0 157 RETURN 158 END 159 C 160 C CALCULATE COMPLEX TRANS COEFF AS A FUNCTION OF E' AND LOSS TAN 161 C 162 COMPLEX FUNCTION TRANS(E1,TANDEL) 163 COMPLEX CMPLX.CEXP.CSORT '64 COMPLEX CNUM.COEN.Z.EPS.GAMMA '65 COMMON /BLK1/ WIDTH,BETAF 166 E2-E1'TANDEL '67 EPS»CMPLX(E1,- 1 0*E2) 168 Z-1 0/CSORT(EPS) '69 GAMMA*(0,1.0)*BETAF/Z 170 CDENM (Z-M 0 ) " 2 ) - < (Z-1 . O) • «2 ) »CEXP(-2 . O'GAMMA* WIDTH ) '71 CNUM-4 ,0'Z"CEXP( - 1 . O'GAMMA'WIDTH) 172 TRANS-CNUM/COEN 173 RETURN 174 END 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 crystal detector has a nonlinear response characteristic. Signal conditioning is required for input to the A/D converter. High resolution is required for digitizating low signal levels in the vicinit y of a null. Lower resolution is adequate for higher signal levels since accuracy is not necessary away from a null point. A two-stage amplifier circuit was built 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 levels. A comparator monitors the signal level to select the appropriate gain. Input signal range is indicated to the microcomputer via a status bit. The low signal output is fed into input channel 0 and the high signal output is fed into input channel 1 of the analog-to-digital converter. A 4066 switch limits both signals to a 5V maximum to protect the A/D converter input stage. A National Semiconductor ADC 0808 A/D converter (100 M S conversion time) is driven by a 4.0 MHz clock signal and a 5V reference voltage is 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 lines to provide visual 78 79 indication of signal levels for verification purposes during testing. A single LED segment indicates the signal range. A 200 ns pulse, generated by a DM7412, is 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 is shown in Figs. C.1 and C.2. Operation The microprocessor reads the status of the signal level indicator bit to select the appropriate A/D channel. A start conversion signal is fed to the DM7412 to initiate conversion. Upon completion of conversion, the EOC pulse toggles the f l i p flop. The microprocessor continuously polls the f l i p - f l o p status and reads the A/D converter data when conversion is complete. +15V VIN VREF } 2 0 K Balance lA/VV, Fig. C . 1 Schematic diagram of amplifier c i r c u i t . CO o DM7412 IN INO INI £7 +3V-100 -VW AMr 470 470 INO INI vcc QE START ALE ECC ADD C ADD B ADD A 84 7 es 9 ee 7 3 -TTlGND VCC lCLKlD IPHC ICLTf 1Q • 5 V i i v c c GND 12 >4 83 74LS74 vcc 1Y4 iY3 5; 1A1 (si CO 2 Y3 J 3Y8 rX. 1A4 GND 1A3 1Y1 2A3 2A2 2A1 eo -•3V 18 19 13 oo IT) P L < CQNV EDC CLR EDC RDY ADD C ADD B ADD A LF356N SCALE VCC CD4049 GND D C I S CD4049 r i C I A GND •5V Fig. C.2 Schematic diagram of analog/digital converter c i r c u i t . APPENDIX D INTERFACE CIRCUITRY Interface board #1 is configured to decode address lines A0-A10. A 74LS138 3-to-8 line decoder decodes address lines 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 Figs. D.1 and D.2. The f i r s t 8255 is programmed to output data bytes to ports A and B. Port A controls the dig i t a l l y programmable phase shifter while port B controls the di g i t a l l y programmable attenuator. Port C remains unused. The second 8255 is 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 is 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 is 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 shifter 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 level indicator, EOC ready PC3 unused PC2 unused PC1 clear EOC PCO start conversion 647 8255#2 programming port IBM PCjr I/D channel connector 8 * * 8 * 8 6 5 < 8 1 2 a < 74LS245 g528S2g|oi arises 74LS541 ro 2 5 S * » ? 74LS138 "5k e 5 5 a 5 ? • 53 74LS541* 5 74LS04 R 3 • < S R -< n to » < x o 74LS30 s "H 26-pin connector •sv-LO 00 IO 01 CM 02 oo PAO D3 PA1 D4 PAS 05 PA3 06 PA4 D7 PAS VCC PA6 GND PA7 Fig. D.2 Schematic diagram of inte GND Al A2 A3 A4 AS A6 A7 A8 VCC Yl Y2 Y3 Y4 Y5 Y6 Y7 Y8 jJiT 20 10 •12V--12V--+SV 19 17 Ut It 3 13 13 14 11 U « It • U 7 GND Al A2 A3 A4 AS At> A7 A8 VCC Yl Y2 Y3 Y4 Y5 Y6 Y7 Y8 •V -V •SV I. 4* 2.8* 3.6* II. 3* 22.5* 43.0* 90.0' 180.0* GND GND 1A1 2A2 2Y1 2Y3 1A4 1A3 1A2 VCC IY1 2Y2 ^ 2A1 CO J 2A3 1Y4 1Y3 G 1Y2 3»" GND 1Y4 VCC 1A4 1Y3 ^ 1A3 1Y2 CM 1A2 1Y1 CO 1A1 2Y1 *J 2A1 2Y2 ^ 2A2 2Y3 2A3 2Y4 17 2A4 -•3 V 17 4 14 7 19 • 14 9 13 10 IC U U It 10 19 i t 14 • i tv --urv-13 14 0.2S dB 0J dB 1.0 dB 2.0 dB 4.0 dB 8.0 dB 164 dB 32.0 dB •V - V GND -•SV CONV EOC CLR EOC ROY SCALE ADD C ADD B ADD A to d i g i t a l phase shi fter to d i g i t a l attenuator ace board #2. CD cn APPENDIX E BRIDGE BALANCING PROGRAM The accompanying 8088 assembly language program locates settings for the digita l l y programmable attenuator and phase shifter that produce a null signal at the detector. The attenuator is i n i t i a l l y set at 0 dB as the phase shifter is scanned from 0° to 360 0 in 10° steps. The detector signal is sampled after each new setting. The phase shift setting that produces the minimum detector level is located and the device is set at that value. The attenuator is then scanned from 0 dB to 21 dB in 1 dB steps to locate the setting that produces a minimum signal level. The attenuator is then set at that value (A,). The phase shifter is scanned from 0,-10° to #,+10° and fixed at the minimum signal level setting. The attenuator in turn is scanned from A,-2 dB to A,+2 dB and fixed at the minimum signal level setting. This iterative process is repeated until the attenuator and phase shifter settings remain unchanged between successive iterations. The total phase shift and attenuation in the system are the sum of values from the calibration data (Appendix F). 8 6 The IBM Perso n a l Computer Assembler 09-11-87 PAGE 1 -1 87 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 = 0280 = 0281 = 0283 = 0287 = 001E = 0071 = 0072 = 000D = 000A page,132 B A L L ASH This assembly language r o u t i n e balances a microwave b r i d g e c r c u i t by a d j u s t i n g the a t t e n u a t i o n and phase i n one branch t o match the a t t e n u a t i o n and phase i n the other branch. Balance i s ob t a i n e d when the sampled s i g n a l i s minimized. A l g o r i t h m : a) A U phase v a l u e s from 0 t o 360 degrees are output to determine the f i r s t order approximation. b) A t t e n u a t i o n v a l u e s from 0 t o 20 dB are output to determine the f i r s t order approximation. c) Phase v a l u e i s r e f i n e d d) A t t e n u a t i o n value i s r e f i n e d e) Phase and a t t e n u a t i o n are c o n t i n u o u s l y r e f i n e d u n t i l constant ( w i t h i n t o l e r a n c e ) v a l u e s are ob t a i n e d . JAMES LOO August 1, 1987 con s t a n t s d e f i n i t i o n phport equ 640 a t t p o r t equ 641 p o r t l equ 643 port2 equ 647 maxit equ 30 stop_key equ 113 re s t _ k e y equ 114 c r equ 13 If equ 10 phase s h i f t e r p o r t a t t e n u a t o r p o r t 8255 #1 i n i t i a l i z a t i o n p o r t l o c a t i o n 8255 #2 i n i t i a l i z a t i o n p o r t l o c a t i o n maximum balance i t e r a t i o n s a l l o w e d q key = q u i t r key = r e s t a r t c a r r i a g e r e t u r n c h a r a c t e r l i n e feed c h a r a c t e r 34 0000 data segment 35 r memory a l l o c a t i o n f o r v a r i a b l e s 36 I 37 0000 ???? port dw ? ;port f o r BALANCE 38 0002 ?? I ova I db ? ;low t r i a l v a l u e f o r BALANCE 39 0003 ?? h i v a l db ? ;high t r i a l v a l u e f o r BALANCE 40 0004 ?? s t e p db ? .•increment f o r BALANCE 41 0005 ?? at t e n db ? /balanced a t t e n u a t i o n 42 0006 ?? phase db ? /balanced phase 43 0007 ?? b a l v a l db ? /value o b t a i n e d by BALANCE 44 0008 ?? a t t o l d db ? / o l d a t t e n (from p r e v i o u s balance) 45 0009 ?? p h o l d db ? / o l d phase (from p r e v i o u s balance) 46 000A ?? a t t d i f db ? / d i f f between new and o l d a t t 47 000B ?? p h d i f db ? / d i f f between new and o l d phase 48 oooc ?? f l a g db ? / f l a g v a r i a b l e f o r BALANCE 49 000D ???? dat dw ? /value sampled by A/D c o n v e r t e r 50 000F ?? b a l c n t db ? /count of b a l a n c i n g i t e r a t i o n s 51 0010 000A base dw 10 /base t o p r i n t numbers i n 52 0012 ???? a t t v a l dw ? / f i n a l a t t e n v a l u e a f t e r b a l a n c i n g 53 0014 ???? phval 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 The IBM Personal Computer Assembler 09-11-87 PAGE 1-2 88 54 0016 ?? 55 0017 ?? 56 57 58 59 0018 00 OA 4A 61 60 65 60 73 20 4C 6F 6F 2C 61 20 4D 69 63 72 6F 62 77 61 76 65 20 4C 63 61 62 6F 72 61 74 64 6F 72 79 20 24 65 003B OD OA 55 42 43 20 66 44 65 70 61 72 74 67 60 65 6E 74 20 6F 68 66 20 45 6C 65 63 69 74 72 69 63 61 6C 70 20 65 6E 67 69 6E 71 65 65 72 69 6E 67 72 20 24 73 0067 OD OA OA 45 6E 74 74 65 72 20 43 6F 60 75 60 61 6E 64 20 3F 76 20 24 77 007B 00 OA OA 52 65 73 78 74 61 72 74 2E 2E 79 2E 3F 20 24 80 008B OD OA 41 74 74 65 81 6E 75 61 74 69 6F 82 6E 3D 20 24 83 009B 00 OA 50 68 61 73 84 65 20 53 68 69 66 85 74 3D 20 24 86 00AB OD OA OA 49 74 65 87 72 61 74 69 6F 6E 88 73 20 72 65 71 75 89 69 72 65 64 3D 20 90 24 91 00C4 00 OA 41 2F 44 20 92 73 61 60 70 6C 65 93 73 20 72 65 71 75 94 69 72 65 64 3D 20 95 24 96 OODD OD OA 4E 6F 20 62 97 61 6C 61 6E 63 65 98 20 70 6F 73 73 69 99 62 6C 65 20 24 100 00F4 OD OA 41 2F 44 20 101 73 61 6D 70 6C 65 102 20 63 6F 75 6E 74 103 20 65 78 63 65 65 104 64 65 64 20 24 105 0111 00 OA OA 2A 2A 2A 106 2A 20 45 78 65 63 maxsamp db ? ;max acceptable EOC waiting cycles adcount db ? ;number of A/0 samples obtained ; output messages to display startjness db cr,If,'James Loo, Microwave Laboratory $' db cr,tf,'UBC Department of Electrical engineering $' prompt db cr,If,If,'Enter Command ? $' promptr db cr,If ,If , 'Restart. . .? $' attmess db cr,If,'Attenuation= $' phmess db cr,If,'Phase Shift= $' itmess db cr,If,If,'Iterations required= $' admess db cr , l f , 'A/D samples required= $' nomess db cr, lf , 'No balance possible $' nobalmess db cr , l f , 'A/D sample count exceeded $' stopmess db cr,If,If,'**** Execution Terminated **** $' The IBM Personal Computer Assembler 09-11-87 PAGE 1-3 89 107 75 74 69 6F 6E 20 108 54 65 72 60 69 6E 109 61 74 65 64 20 2A 110 2A 2A 2A 20 24 111 112 ; calibration values for 113 ; General Microwave Model 7728 phase shifter (in degrees) 114 ; tabulated values are 10X actual value. 115 ; phase shifter settings 116 117 0134 0000 000F 0014 001E ph_phcal dw 0000, 0015, 0020, 0030, 0040 ; 0, 1, 2, 3, 4 118 0028 119 013E 0032 003C 0041 0050 dw 0050, 0060, 0065, 0080, 0090 ; 5, 6, 7, 8, 9 120 005A 121 0148 0064 006E 007D 008C dw 0100, 0110, 0125, 0140, 0145 ; 10, 11, 12, 13, 14 122 0 0 9 1 123 0152 0096 00A5 00AF 00BE dw 0150, 0165, 0175, 0190, 0205 ; 15, 16, 17, 18, 19 124 00CD 125 015C 0007 00E1 00EB 00FA dw 0215, 0225, 0235, 0250, 0265 ; 20, 21, 22, 23, 24 1 2 6 0 1 0 9 127 0166 0113 0122 0131 0145 dw 0275, 0290, 0305, 0325, 0330 ; 25, 26, 27, 28, 29 128 014A 129 0170 0159 0 1 6 8 0177 0 1 8 6 dw 0345, 0360, 0375, 0390, 0405 ; 30, 31, 32, 33, 34 130 0195 131 017A 01A4 01BD 01C7 01D6 dw 0420, 0445, 0455, 0470, 0490 ; 35, 36, 37, 38, 39 132 01EA 133 0184 01F9 0208 021C 0226 dw 0505, 0520, 0540, 0550, 0570 ; 40, 41, 42, 43, 44 134 023A 135 018E 0249 025D 026C 027B dw 0585, 0605, 0620, 0635, 0655 ; 45, 46, 47, 48, 49 136 028F 137 0198 0299 02AD 02C1 02CB dw 0665, 0685, 0705, 0715, 0735 ; 50, 51, 52, 53, 54 138 02DF 139 01A2 02E9 02FD 030C 0318 dw 0745, 0765, 0780, 0795, 0810 ; 55, 56, 57, 58, 59 140 032A 141 01AC 033E 0348 035C 0366 dw 0830, 0840, 0860, 0870, 0890 ; 60, 61, 62, 63, 64 142 037A 143 01B6 038E 0393 03A7 03BB dw 0910, 0915, 0935, 0955, 0960 ; 65, 66, 67, 68, 69 144 03C0 145 01C0 03D4 03E3 03F2 0406 dw 0980, 0995, 1010, 1030, 1040 ; 70, 71, 72, 73, 74 146 0410 147 01CA 041F 0433 043D 0451 dw 1055, 1075, 1085, 1105, 1115 ; 75, 76, 77, 78, 79 148 045B 149 0104 046F 047E 0480 04A1 dw 1135, 1150, 1165, 1185, 1205 ; 80, 81, 82, 83, 84 150 04B5 151 01DE 04BF 04CE 04E2 04F1 dw 1215, 1230, 1250, 1265, 1285 ; 85, 86, 87, 88, 89 1 5 2 0 5 0 5 153 01E8 050F 0523 0532 0546 dw 1295, 1315, 1330, 1350, 1360 ; 90, 91, 92, 93, 94 154 0550 155 01F2 0564 0573 0582 0596 dw 1380, 1395, 1410, 1430, 1445 ; 95, 96, 97, 98, 99 1 5 6 05A 5 157 01FC 05AF 05B9 05C8 0507 dw 1455, 1465, 1480, 1495, 1510 ;100, 101, 102, 103, 104 158 05E6 159 0206 05F5 05FF 060E 0618 dw 1525, 1535, 1550, 1560, 1570 ;105, 106, 107, 108, 109 The IBM Personal Computer Assembler 09-11-87 160 0622 161 0210 0631 0640 064F 0659 162 0663 163 021A 0672 0677 0686 0690 164 069A 165 0224 06A4 06B3 06BD 06C7 166 0601 167 022E 0608 06EA 06EF 06FE 168 0700 169 0238 0717 0721 0726 0735 170 073F 171 0242 0749 0758 0767 076C 172 077B 173 024C 0780 078F 079E 07A3 174 07B2 175 0256 07BC 07CB 070A 07E4 176 07F3 177 0260 0802 0811 0820 082 F 178 083E 179 026A 0840 0857 0866 0875 180 0889 181 0274 0898 08A7 08B6 08CA 182 0809 183 027E 08E8 08FC 090B 091F 184 0933 185 0288 0942 0956 0960 0974 186 0988 187 0292 099C 09B0 09BF 09CE 188 09E2 189 029C 09EC 0A00 0A14 0A1E 190 0A32 191 02A6 0A41 0A50 0A5F 0A69 192 0A7D 193 02B0 0A91 0A9B OAAA OABE 194 0AC8 195 02BA OADC 0AE6 0AF5 0B04 196 0B13 197 02C4 0B22 0B36 0B40 0B4F 198 0B59 199 02CE 0860 0B7C 0B88 0B9A 200 08A9 201 02D8 OBBD OBCC 0BD6 0BE5 202 0BF9 203 02E2 OCOD 0C1C 0C2B 0C3A 204 0C49 205 02EC 0C53 0C62 0C76 0C85 206 0C94 207 02F6 0CA3 0CB2 0CC1 OCCB 208 OCDA 209 0300 0CE4 0CF3 0002 ODOC 210 0D1B 211 030A 0D25 0D39 003E 0048 212 0057 PAGE 1-4 90 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 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 dw 1920, 1935, 1950, 1955, 1970 ;140, 141, 142, 143, 144 dw 1980, 1995, 2010, 2020, 2035 ;145, 146, 147, 148, 149 dw 2050, 2065, 2080, 2095, 2110 ;150, 151, 152, 153, 154 dw 2125, 2135, 2150, 2165, 2185 ; 155. 156, 157, 158, 159 dw 2200, 2215, 2230, 2250, 2265 ;160, 161, 162, 163, 164 dw 2280, 2300, 2315, 2335, 2355 ;165, 166, 167, 168, 169 dw 2370, 2390, 2400, 2420, 2440 ;170, 171, 172, 173, 174 dw 2460, 2480, 2495, 2510, 2530 ;175, 176, 177. 178, 179 dw 2540, 2560, 2580, 2590, 2610 ;180, 181, 182, 183, 184 dw 2625, 2640, 2655, 2665, 2685 ;185, 186, 187. 188, 189 dw 2705, 2715, 2730, 2750, 2760 ;190, 191, 192, 193, 194 dw 2780, 2790, 2805, 2820, 2835 ;195, 196, 197, 198, 199 dw 2850, 2870, 2880, 2895, 2905 ;200, 201, 202, 203, 204 dw 2925, 2940, 2955, 2970, 2985 ;205, 206, 207, 208, 209 dw 3005, 3020, 3030, 3045, 3065 ;210, 211, 212, 213, 214 dw 3085, 3100, 3115, 3130, 3145 ;215, 216, 217. 218, 219 dw 3155, 3170, 3190, 3205, 3220 ;220, 221, 222, 223, 224 dw 3235, 3250, 3265, 3275, 3290 ;225, 226, 227, 228, 229 dw 3300, 3315, 3330, 3340, 3355 ;230, 231, 232. 233, 234 dw 3365, 3385, 3390, 3400, 3415 ;235, 236, 237, 238, 239 The IBM Per s o n a l Computer Assembler 09-11-87 PAGE 1-5 91 213 214 215 216 217 218 219 220 221 222 223 0314 0066 0D75 0D7A 0089 0D93 031E 0098 0DA7 OOAC 0D8B 0DC5 0328 ODCF 0DD9 0DE8 0DF2 00 FC 0332 0E01 dw 3430, 3445, 3450, 3465, 3475 ;240, 241, 242, 243, 244 dw 3480, 3495, 3500, 3515, 3525 ;245, 246, 247, 248, 249 dw 3535, 3545, 3560, 3570, 3580 ;250, 251, 252, 253, 254 dw 3585 ;255 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 at 10.19 GHz ( i n dB). A l l v a l u e s are 10X s e t t i n g 224 0334 00 00 01 01 01 p h _ a t t c a l db 0, 0, 1, 1, 1 0, 1, 2, 3, 4 225 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 db 10, 10, 9, 9, 9 60, 61, 62, 63, 64 237 0375 09 09 09 OA OA db 9, 9, 9, 10, 10 65, 66, 67, 68, 69 238 037A OA OB OB OB OB db 10, 11, 11, 11, 11 70, 71, 72, 73, 74 239 037F OB OB OB OB OC db 11, 11, 11, 11, 12 75, 76, 77, 78, 79 240 0384 OC OC OC OC OC db 12, 12, 12, 12, 12 80, 81, 82, 83, 84 241 0389 OC OC OC OC OC db 12, 12, 12, 12, 12 85, 86, 87, 88, 89 242 038E OB OB OB OB OB db 11, 11, 11. 11, 11 90, 91, 92, 93, 94 243 0393 OB OB OB OA OA 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 db 10, 11, 11, 11, 11 150, 151, 152, 153, 154 255 03CF OC OC OC OD OE db 12, 12, 12, 13, 14 155, 156, 157, 158, 159 256 03D4 OE OE OE OE OF db 14, 14, 14, 14, 15 160, 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 db 13, 12, 12, 12, 12 180, 181, 182, 183, 184 261 03ED OB OA OA 09 09 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, 207, 208, 209 The IBM P e r s o n a l Computer Assembler 0 9 - 1 1 - 8 7 PAGE 1-6 92 266 0406 09 09 09 09 09 db 9 , 9 , 9 . 9 , 9 210, 211 , 212, 213 , 214 267 040B 09 09 09 09 09 db 9 . 9 . 9 , 9 , 9 215. 216, 217, 218, 219 268 0410 09 09 09 09 08 db 9 , 9 . 9 , 9 , 8 220, 221 , 222, 223 , 224 269 0415 08 08 07 07 06 db 8 , 8 , 7 , 7 , 6 225. 226, 227, 228, 229 270 041A 06 06 06 06 06 db 6 , 6 . 6 , 6 , 6 230, 231 . 232, 234, 235 271 041F 05 05 05 05 04 db 5 . 5 . 5 , 5 , 4 236, 237, 238, 239, 240 272 0424 04 04 04 04 03 db 4 , 4 , 4 . 4 , 3 241 , 242, 243 , 244, 245 273 0429 03 03 02 02 02 db 3 . 3 , 2 . 2 , 2 246, 247, 248, 249, 250 274 042E 02 02 02 02 01 db 2 , 2 , 2 . 2 , 1 251 . 252. 253 , 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 Genera l Microwave Model 3455 278 a t t e n u a t o r phase s h i f t s ( i n degrees ) 279 a l l phase v a l u e s a r e 10X s e t t i n g s 280 281 0434 0000 0002 0003 0005 a t t _ p h c a l dw 0. 2 . 3 , 5 , 6 0 , 1 , 2 . 3 , 4 282 0006 283 043E 0008 0009 000B OOOC dw 8 , 9 , 11 , 12. 14 5 . 6 , 7 , 8 , 9 284 000E 285 0448 0010 0011 0013 0015 dw 16, 17, 19, 2 1 , 23 10, 11 , 12, 13, 14 286 0017 287 0452 0019 001B 001D 0020 dw 25 , 27 , 29 , 32 , 34 15, 16, 17. 18, 19 288 0022 289 045C 0024 0026 0029 002B dw 36 , 3 8 , 4 1 . 43 , 45 20 , 2 1 , 22 . 2 3 , 24 290 002D 291 0466 0030 0032 0035 0037 dw 4 8 , 50 , 5 3 , 55 , 58 25 , 26 , 27 , 28 , 29 292 003A 293 0470 003C 003F 0041 0044 dw 60 , 6 3 , 6 5 , 68 , 71 30 , 3 1 , 3 2 . 3 3 , 34 294 0047 295 047A 0049 004C 004F 0052 dw 73 . 76 , 79 . 82 , 84 3 5 , 36 , 3 7 , 38 , 39 296 0054 297 0484 0057 005A 005D 0060 dw 87 , 9 0 , 9 3 . 9 6 , 99 • 4 0 , 4 1 , 4 2 , 4 3 , 44 298 0063 299 048E 0066 0069 006C 006 F dw 102, 105, 108, 111, 114 ; 4 5 , 46 , 47 , 4 8 . 49 300 0072 301 0498 0076 0079 007C 007F dw 118, 121, 124, 127, 130 ? 50 , 5 1 , 52 , 53 , 54 302 0082 303 04A2 0085 0088 008B 008F dw 133, 136, 139, 143, 146 ; 55 , 56 , 57 , 58 . 59 304 0092 305 04AC 0095 0098 009C 009F dw 149, 152, 156. 159, 162 ; 60 , 6 1 , 62 , 6 3 , 64 306 00A2 307 04B6 00A5 00A9 OOAC OOAF dw 165, 169, 172, 175, 179 ; 6 5 , 66 , 67 , 68 , 69 308 00B3 309 04C0 00B6 OOBA OOBD 00C1 dw 182, 186, 189, 193, 196 ; 70 , 7 1 , 72 , 73 , 74 310 00C4 311 04CA 00C8 OOCB OOCF 00D2 dw 200, 203, 207, 210, 214 ; 75 , 76 , 77 , 78 , 79 312 0006 313 04D4 0009 OODC OOEO 00E3 dw 217, 220, 224, 227. 230 ; 80 . 8 1 , 8 2 , 8 3 , 84 314 00E6 315 040E OOEA OOEE 00F1 00F5 dw 234, 238, 241 , 245, 248 ; 8 5 , 86 , 87 , 8 8 , 89 316 00F8 317 04E8 OOFC OOFF 0102 0106 dw 252, 255 , 258, 262, 265 ; 9 0 , 9 1 . 92 , 9 3 , 94 318 0109 The IBM Personal Computer Assembler 09-11-87 PAGE 1-7 93 319 04F2 0100 0110 0114 0117 dw 269, 272, 276, 279, 283 95, 96, 97. 98, 99 320 011B 321 04FC 011E 0122 0125 0129 dw 286, 290, 293, 297, 300 100, 101, 102, 103. 104 322 012C 323 0506 012F 0133 0136 0139 dw 303, 307, 310, 313, 317 •105, 106, 107, 108, 109 324 0130 325 0510 0140 0144 0147 014B dw 320, 324, 327, 331, 335 •110, 111, 112, 113, 114 326 014F 327 051A 0153 0157 015B 015F dw 339, 343, 347, 351, 354 •115, 116, 117, 118, 119 328 0162 329 0524 0166 016A 016F 0173 dw 358, 362, 367, 371, 375 120, 121, 122, 123, 124 330 0177 331 052E 017B 017F 0182 0186 dw 379, 383, 386, 390, 394 125. 126, 127, 128, 129 332 018A 333 0538 017B 017F 0182 0186 dw 379, 383, 386, 390, 394 130, 131. 132, 133. 134 334 018A 335 0542 018E 0191 0195 0199 dw 398, 401, 405, 409, 414 135, 136, 137, 138, 139 336 019E 337 054C 01A2 01A6 01AA 01AE dw 418, 422, 426, 430, 434 140, 141, 142, 143, 144 338 01B2 339 0556 01B6 01 BA 01BF 01C3 dw 438, 442, 447, 451, 455 145, 146, 147, 148, 149 340 01C7 341 ; attenuator attenuation calibration values 342 ; for 10.19 GHz (i n dB) 343 ; a l l values are 10X setting 344 ; 345 0560 0000 0003 0005 0008 att_attcal dw 0. 3. 5, 8, 10 0, 1. 2. 3, 4 346 0OOA 347 056A 000D OOOF 0012 0014 dw 13, 15, 18. 20, 23 5. 6. 7, 8, 9 348 0017 349 0574 0019 001C 001E 0021 dw 25, 28, 30, 33, 35 ' 10, 11. 12. 13. 14 350 0023 351 057E 0026 0028 002B 002D du 38, 40, 43. 45. 48 • 15, 16. 17, 18. 19 352 0030 353 0588 0032 0035 0037 003A dw 50, 53, 55, 58, 60 ; 20, 21. 22, 23. 24 354 003C 355 0592 003 F 0041 0044 0046 dw 63, 65, 68. 70, 73 ; 25, 26, 27, 28, 29 356 0049 357 059C 004B 004E 0050 0053 dw 75, 78, 80, 83, 85 ; 30, 31. 32. 33, 34 358 0055 359 05A6 0058 005A 005D 005 F dw 88, 90, 93. 95, 98 ; 35, 36, 37, 38, 39 360 0062 361 05B0 0064 0067 0069 006C dw 100, 103, 105, 108, 110 ; 40, 41, 42, 43, 44 362 006E 363 05BA 0071 0073 0076 0078 dw 113, 115, 118, 120, 123 ; 45, 46. 47. 48, 49 364 007B 365 05C4 007D 0080 0082 0085 dw 125, 128, 130, 133, 135 ; 50, 51. 52, 53, 54 366 0087 367 05CE 008A 008C 008F 0091 dw 138, 140, 143, 145, 148 ; 55, 56, 57. 58, 59 368 0094 369 05D8 0096 0099 009B 009E dw 150, 153, 155, 158, 160 ; 60, 61, 62, 63, 64 370 00A0 371 05E2 00A3 00A5 00A8 OOAA dw 163, 165, 168. 170, 173 ; 65, 66, 67, 68, 69 The IBM Personal Computer Assembler 09-11-87 PAGE 1-8 94 372 00AD 373 05EC OOAF 00B2 00B4 00B7 dw 175, 178, 180, 183, 185 ; ro. 71. 72, 73, 74 374 00B9 375 05 F6 OOBC OOBE 00C1 00C3 dw 188, 190, 193, 195, 198 ; 75, 76. 77, 78, 79 376 00C6 377 0600 00C8 OOCB OOCD OODO dw 200, 203, 205, 208, 210 ; so, 81, 82, 83. 84 378 00D2 379 060A 0005 00D7 OODA OODC dw 213, 215, 218, 220, 223 ; 85, 86, 87. 88, 89 380 OODF 381 0614 00E1 00E4 00E6 00E9 dw 225, 228, 230, 233, 235 ; 90. 91. 92, 93, 94 382 OOEB 383 061E OOEE OOFO 00F3 00F5 dw 238, 240, 243, 245, 248 ; 95, 96, 97, 98, 99 384 00F8 385 0628 OOFA OOFD OOFF 0102 dw 250, 253, 255, 258, 260 ;100, 101, 102, 103, 104 386 0104 387 0632 0107 0109 010C 010E dw 263, 265, 268, 270, 273 ;105. 106, 107. 108, 109 388 0111 389 063C 0113 0116 0118 011B dw 275, 278, 280, 283, 285 ;110, 111, 112, 113, 114 390 0110 391 0646 0120 0122 0125 0127 dw 288, 290, 293, 295, 298 ;115, 116. 117, 118, 119 392 012A 393 0650 012C 012F 0131 0134 dw 300, 303, 305, 308, 310 ;120, 121, 122, 123, 124 394 0136 395 065A 0139 013B 013E 0140 dw 313, 315, 318, 320, 323 ;125, 126, 127, 128, 129 396 0143 397 0664 0145 0148 014A 0140 dw 325, 328, 330, 333, 335 ;130, 131, 132, 133, 134 398 014F 399 066E 0152 0154 0157 0159 dw 338, 340, 343, 345, 348 ;135. 136. 137, 138, 139 400 015C 401 0678 015E 0161 0163 0166 dw 350, 353, 355, 358, 360 ;140, 141, 142, 1*3, 144 402 0168 403 0682 data ends 404 » 405 # 406 0000 stack segment stack 407 0000 80 [ dw 128 dup(?) 408 ???? 409 ] 410 411 0100 stack ends 412 i 413 » 414 0000 code segment 415 0000 BRIDGE proc far 416 assume cs:code,ds:data,ss:stack 417 1 418 0000 1E push ds ;configure for return to DOS 419 0001 B8 0000 mov ax,0 420 0004 50 push ax 421 0005 B8 R mov ax,data 422 0008 8E 08 mov ds,ax 423 1 424 1 The IBM Personal Computer Assembler 09-11-87 PAGE 1-9 95 425 # 426 000A restart: ;re-initialize ports 427 00OA BA 0283 mov dx.portl 428 000D BO 80 mov al,128 429 000F EE out dx.al ;write 8255 #1 programming byte 430 0010 BA 0287 mov dx,port2 431 0013 BO 98 mov al,152 432 0015 EE out dx.al ;write 8255 #2 programming byte 433 ; 434 ; Await input commands from keyboard 435 ; 436 0016 BA 0018 R mov dx,offset start_mess ;output init ial message 437 0019 B4 09 mov ah,9 438 001B CD 21 int 21h 439 001D key_in: 440 001D BA 0067 R mov dx,offset prompt ;output prompt for keyboard input 441 0020 B4 09 mov ah,9 442 0022 CD 21 int 21h ;print prompt comments 443 0024 B4 00 mov ah,0 ;read keyboard function 444 0026 CD 16 int 16h ;keyboard I/O 445 0028 3C 71 cmp al,stop_key ;test for q (lower case--quit) 446 002A 75 03 jne no_q ;no q detected 447 002C E9 01B1 R jmp done ;q detected 448 002F no_q: 449 002F 3C 72 cmp al,rest_key 450 0031 75 09 jne no_r 451 0033 BA 007B R mov dx,offset promptr ;output for restart 452 0036 B4 09 mov ah,9 453 0038 CD 21 int 21h 454 003A EB CE jmp restart 455 003C no_r: 456 003C 3C 00 cmp al , 13 ;test for ENTER key 457 003E 75 DD jne key_in ;re-read keyboard until q or ENTER 458 0040 C6 06 0017 R 00 mov adcount,0 .•initialize A/D sample counter 459 0045 BA 0281 mov dx,attport ; ini t ia l attenuation=0 dB 460 0048 33 CO xor ax,ax ; during phase scan 461 004A EE out dx,al 462 ; 463 ; configure for initial phase scan 464 ; 465 004B C7 06 0000 R 0280 mov port.phport .•configure phase shifter port 466 0051 C6 06 0002 R 00 mov loval,0 ;Iova 1=0 467 0056 C6 06 0003 R 03 mov hival,3 ;terminate loop after 1 cycle 468 005B C6 06 0004 R 07 mov step,7 ;step=7 (approx 10 degrees) 469 0060 E8 01B9 R call balance 470 0063 AO 0007 R mov al,balval 471 0066 A2 0006 R mov phase,al ;retain balanced phase 472 ; 473 ; configure for init ial attenuator scan 474 ; 475 0069 C7 06 0000 R 0281 mov port.attport .•configure attenuator port 476 006F C6 06 0002 R 00 mov Ioval,0 ;Iova1=0 477 0074 C6 06 0003 R 54 mov hival,84 ;hival=84 The IBM Personal Computer Assembler 09-11-87 PAGE 1-10 96 478 0079 C6 06 0004 R 04 mov step,4 ;step=4 (1 dB) 479 007E E8 01B9 R c a l l balance 480 0081 AO 0007 R mov a l . b a l v a l 481 0084 A2 0005 R mov a t t e n , a l ; a t t e n = b a l v a l 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 i t r a t e : 485 008C FE 06 OOOF R inc b a l c n t /increment balance counter 486 0090 80 3E OOOF R 1E cmp balcnt,max i t ; l i m i t # of i t e r a t i o n s 487 0095 75 OA jne balok ;unable t o balance-->try agai 488 0097 BA OODD R mov d x , o f f s e t nomess ;output u n s u c c e s s f u l message 489 009A B4 09 mov ah,9 490 009C CD 21 i n t 21h 491 009E E9 01AE R jmp newval /maximum i t e r a t i o n s reached 492 00 A1 balok: 493 / 494 ; 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 scan 495 ; 496 00A1 AO 0006 R mov al,phase /remember o l d phase s e t t i n g 497 00A4 A2 0009 R mov p h o l d . a l 498 00A7 C7 06 0000 R 0280 mov port.phport / 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 al,phase /set lower l i m i t 500 00B0 2C 03 sub a 1,3 501 00B2 A2 0002 R mov I ova I,a I /loval=phase-3 502 00B5 AO 0006 R mov a I,phase /s e t upper l i m i t 503 0OB8 04 04 add a l , 4 504 OOBA A2 0003 R mov h i vaI,a I /hival=phase+4 505 00BO C6 06 0004 R 01 mov step,1 ;step=1 (1.4 degrees) 506 00C2 E8 01B9 R c a l l balance 507 00C5 AO 0007 R mov a l . b a l v a l 508 00C8 A2 0006 R mov phase,al ;phase=balval 509 / 510 ; c o n f i g u r e r e g i s t e r s f o r a t t e n u a t o r scan 511 ; 512 OOCB AO 0005 R mov a l , a t t e n /remember o l d a t t e n s e t t i n g 513 OOCE A2 0008 R mov a t t o l d , a l 514 0001 C7 06 0000 R 0281 mov p o r t . a t t p o r t / c o n f i g u r e a t t e n u a t o r p o r t 515 0007 3C 03 cmp a l , 3 516 00D9 72 11 j b lowend 517 0008 8A D8 mov b l , a l 518 OOOD 2C 03 sub a l , 3 /set lower l i m i t 519 000 F A2 0002 R mov I ova I,a I / l o v a l = a t t e n - 3 520 00E2 80 C3 04 add b l , 4 /set upper l i m i t 521 00E5 88 1E 0003 R mov h i v a l . b l /hival=atten+4 522 00E9 EB OB 90 jmp o k a t t 523 ; 524 ; s e t scan range f o r low at t e n u a t o r s e t t i n g s 525 ; 526 OOEC lowend 527 OOEC C6 06 0002 R 00 mov I ova 1,0 ; l o v a 1=0 (lower l i m i t ) 528 00F1 C6 06 0003 R 07 mov h i v a l , 7 /hival=7 (upper l i m i t ) 529 0OF6 o k a t t : 530 00F6 C6 06 0004 R 01 mov step,1 /step=1 (0.25 dB) The IBM Personal Computer Assembler 09-11-87 PAGE 1-11 97 531 OOFB E8 01B9 R ca l l balance 532 OOFE AO 0007 R mov al.balval 533 0101 A2 0005 R mov atten,al ;atten=balval 534 ; 535 ; check for phase changes between iterations 536 ; 537 0104 AO 0006 R mov al.phase 538 0107 8A 1E 0009 R mov bl,phold 539 010B 2A C3 sub al,bl ;al=phase-phold 540 010D 79 02 jns posta 541 010F F6 D8 neg a I 542 0111 posta: 543 0111 3C 00 cmp a 1,0 ;no phase variation 544 545 0113 76 03 jna skipl 546 0115 E9 008C R jmp itrate 547 ; 548 ; check for attenuation changes 549 ; 550 0118 sk i p l : 551 0118 AO 0005 R mov al.atten 552 01 IB 8A 1E 0008 R mov bl.attold 553 011F 2A C3 sub al,bl ;al=atten-attold 554 0121 79 02 jns postp 555 0123 F6 D8 neg a I 556 0125 postp: 557 0125 3C 01 cmp a 1,1 ;1 bit attenuator variation tolerance 558 0127 76 03 jna writeout 559 0129 E9 008C R jmp itrate 560 012C writeout: 561 012C 8A 1E 0006 R mov bl,phase ;put 8 bit phase value in bx 562 0130 32 FF xor bh.bh 563 0132 8A 87 0334 R mov al,ph_attcal[bx] ;get phase shifter atten (byte) 564 0136 32 E4 xor ah,ah /clear high order b i t 565 0138 A3 0012 R mov attval.ax ;store in main memory 566 013B 03 DB add bx,bx ;double for word address 567 013D 8B 87 0134 R mov ax,ph_phcal [bx] ;get phase shi f t e r phase (word) 568 0141 A3 0014 R mov phval.ax ;store in main memory 569 0144 8A 1E 0005 R mov bt,atten ;put 8 bit atten value in bx 570 0148 32 FF xor bh.bh 571 014A 03 DB add bx,bx /double for word address 572 014C 8B 87 0560 R mov ax,att_attcal[bx] /get atten attenuation (word) 573 0150 01 06 0012 R add attval,ax /add attenuation to total 574 0154 8B 87 0434 R mov ax,att_phcal[bx] /get attenuator phase s h i f t (word) 575 0158 01 06 0014 R add phval.ax /add phase sh i f t to total 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 /write out attenuation message 579 0163 A1 0012 R mov ax,attval 580 0166 E8 0253 R ca l l write_dec /write out actual attenuation 581 0169 AO 0005 R mov al.atten / ( i n dB) 582 016C 32 E4 xor ah,ah 583 016E E8 0271 R ca l l decimal out The IBM Personal Computer Assembler 09-11-87 PAGE 1-12 98 584 0171 BO 29 mov a l , ' ) ' 585 0173 E8 028A R c a l l character_out 586 0176 BA 009B R mov dx,offset phmess ;get phase s h i f t message 587 0179 B4 09 mov ah,9 588 017B CD 21 int 21h ;write out phase shift message 589 0170 A1 0014 R mov ax.phval 590 0180 E8 0253 R c a l l write_dec ;write out actual phase sh i f t 591 0183 AO 0006 R mov aI,phase ;( i n degrees) 592 0186 32 E4 xor ah,ah 593 0188 E8 0271 R c a l l decimal_out 594 018B BO 29 mov a 1, 1) 1 595 0180 E8 028A R c a l l character out 596 0190 BA OOAB R mov dx,offset itmess ;get iteration counter message 597 0193 B4 09 mov ah,9 598 0195 CD 21 int 21h 599 0197 AO OOOF R mov a I,balcnt ;write iteration counter 600 019A 32 E4 xor ah,ah 601 019C E8 0271 R c a l l decimal_out 602 019F BA 00C4 R mov dx,offset admess ;get A/D sample counter message 603 01A2 B4 09 mov ah,9 604 01A4 CD 21 int 21h 605 01A6 AO 0017 R mov al,adcount ;get A/D sample counter 606 01A9 32 E4 xor ah,ah 607 01 AB E8 0271 R c a l l decimal_out 608 * 609 01AE newval: 610 01AE E9 001D R jmp key_in ;jump point for no balance 611 01B1 done: 612 01B1 BA 0111 R mov dx, offset stopmess 613 01B4 B4 09 mov ah,9 614 0186 CO 21 int 21h ;print termination message 615 01B8 CB ret 616 01B9 BRIDGE endp 617 618 This subroutine outputs phase or attenuation settings from a 619 low limit to a high limit and searches for the minimum 620 signal level 621 622 01B9 BALANCE proc near 623 01B9 B9 0700 mov cx,2000 ;cx=2000 ( i n i t arbitrary low value) 624 01BC AO 0002 R mov al,loval ;al=low index 625 01BF 8A 26 0003 R mov ah.hival ;ah=high index 626 01C3 8B 16 0000 R mov dx,port 627 01C7 balseq: 628 01C7 EE out dx,al .•output current value 629 01C8 50 push ax .•remember ax register 630 01C9 52 push dx .•remember dx register 631 01 CA E8 01F0 R c a l l sample ;get sample value 632 01 CD 5A pop dx .•restore dx register 633 01CE 58 pop ax .•restore ax register 634 01CF 8B 1E OOOD R mov bx,dat ;store sample value in bx 635 01D3 3B 09 cmp bx,cx /compare with existing low value 636 01D5 77 05 ja bigger 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 flag,al ;update new minimum index 639 01DC bigger: 640 01DC 02 06 0004 R add a I,step ;index update: bl=bl+step 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,flag 644 01E7 A2 0007 R mov balval.al ;balval = flag index 645 01EA 8B 16 0000 R mov dx,port 646 01EE EE out dx.al ;output minimum value 647 01EF C3 ret 648 01 FO BALANCE endp 649 650 This subroutine samples the microwave signal 651 and returns a d i g i t a l value 652 If the signal is on its high scale, the output 653 lies in the 1000-1255 range. 654 If the signal is on its low scale, the output 655 lies in the 0-255 range 656 657 01F0 SAMPLE proc near 658 01F0 sampstart: 659 01F0 C6 06 0016 R 14 mov maxsamp,20 / i n i t i a l i z e counter 660 01F5 BA 0286 mov dx,646 ;out 646,0 661 01F8 33 CO xor ax,ax /clear start conversion signal 662 01FA EE out dx.al /and clear EOC flag 663 01 FB EC in a I,dx /al=inp(646) signal range? 664 01 FC 24 20 and al,00100000b /al = 32? 665 01 FE 75 24 jnz lowdat 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 /select high A/D channel 670 0209 B8 0003 mov ax,3 671 020C EE out dx,al /out 646,3: start conversion 672 020D eoc_high_wait: 673 0200 FE OE 0016 R dec maxsamp /decrement sample counter 674 0211 74 37 jz escape /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 flag (bit #4) 677 0216 74 F5 jz eoc_high_wait /re-sample EOC bit until EOC done 678 0218 BA 0284 mov dx,644 679 021B EC in a I,dx /al=inp(644): input high data 680 021C 32 E4 xor ah,ah /clear higher order register 681 021E 05 03E8 add ax,1000 /ax=ax+1000 682 0221 EB 1F 90 jmp datsign 683 0224 lowdat: 684 0224 BA 0285 mov dx,645 685 0227 33 CO xor ax,ax 686 0229 EE out dx,al /out 645,0: select low A/D channel 687 022A BA 0286 mov dx,646 688 0220 B8 0003 mov ax,3 689 0230 EE out dx ,a l /out 646,3: start conversion The IBM Personal Computer Assembler 09-11-87 PAGE 1-14 1 0 0 690 0231 eoc_low_wait: 691 0231 FE OE 0016 R dec maxsamp /decrement sample counter 692 0235 74 13 jz escape /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 flag (bit #4 695 023A 74 F5 jz eoc_low_wait /re-sample EOC bit until EOC done 696 023C BA 0284 mov dx,644 697 023F EC in al,dx /al=inp(644): input low scale dat 698 0240 32 E4 xor ah,ah /clear high order register 699 0242 datsign: 700 0242 A3 OOOD R mov dat,ax /dat=sampled signal value 701 0245 FE 06 0017 R inc adcount /increment A/D sample counter 702 0249 C3 ret 703 704 • maximum EOC waiting cycles exceeded 705 706 024A escape: 707 024A BA 00 F4 R mov dx,offset nobalmess 708 024D B4 09 mov ah,9 /write out max A/D sample message 709 024 F CD 21 int 21h 710 0251 EB 90 jmp sampstart /restart from beginning 711 0253 SAMPLE endp 712 713 714 715 A subroutine to print the contents of 716 the AX register divided by 10. 717 718 719 0253 WRITEJ3EC proc near 720 0253 33 D2 xor dx,dx /clear higher order word 721 0255 F7 36 0010 R div base /double word division by 10 722 0259 52 push dx /store remainder on stack 723 025A E8 0271 R c a l l decimal_out /print AX register contents 724 0250 BO 2E mov a I,'. 1 /print decimal point 725 025 F E8 028A R ca l l character_out 726 0262 58 pop ax /place remainder in AX register 727 0263 E8 0271 R c a l l decimal_out /print AX register contents 728 0266 BO 20 mov a l , 1 1 729 0268 E8 028A R c a l l character_out 730 026B BO 28 mov a 1, 1(' 731 0260 E8 028A R ca l l character_out 732 0270 C3 ret 733 0271 WRITE_DEC endp 734 735 736 • This subroutine outputs a byte in decimal form 737 • AX contains number to be printed 738 739 0271 DECIMALJXJT proc near 740 0271 B9 0000 mov cx,0 / i n i t i a l i z e counter 741 0274 another_digit: 742 0274 41 inc cx /increment counter The IBM Personal Computer Assembler 09-11-87 PAGE 1-15 1 743 0275 33 D2 xor dx.dx 744 0277 F7 36 0010 R div base 745 027B 52 push dx 746 027C 3D 0000 cmp ax,0 747 027F 75 F3 jne another_digit 748 0281 print_digits: 749 0281 58 pop ax 750 0282 04 30 add al,'0' 751 0284 E8 028A R c a l l characterout 752 0287 E2 F8 loop print_digits 753 0289 C3 ret 754 028A DECIMALJXJT endp 755 756 output a single character 757 character to print in al 758 ax and dl destroyed 759 760 028A CHARACTERJXJT proc near 761 028A 8A DO mov dl , a l 762 028C B4 02 mov ah,2 763 028E CD 21 int 21h 764 0290 C3 ret 765 0291 CHARACTERJXJT endp 766 767 0291 code ends 768 end ;clear high order word ,-divide by base .•remainder is less sig d i g i t ; i s the quotient zero? ; i f not, more number to convert .•retrieve d i g i t from the stack ;convert to asci i ;print the character ;do alI of the d i g i t s ;return to c a l l e r /character to output ;output character function ;print character APPENDIX F ATTENUATOR AND PHASE SHIFTER CALIBRATION The transmission coefficients of the d i g i t a l l y programmable attenuator and phase shifter were manually measured using a microwave bridge circuit as shown in Fig. 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 shift variation with setting and the HP 885A has minimal insertion loss change with setting. The measured transmission coefficients at 10.19 GHz are shown in Figs. F.2 and F.3. The attenuations and phase shifts of the two devices at a balance point are summed to obtain the total transmission parameter. 102 A A manual A 0 manual S o u r c e I s o l a t o r M a t c h e d D e t e c t o r VSWR I n d i c a t o r I s o l a t o r AA or A0 dig i ta l 7V I s o l a t o r I n t e r f a c e TS M i c r o c o m p u t e r F i g . F.1 M i c r o w a v e c i r c u i t f o r c o n t r o l d e v i c e c a l i b r a t i o n . o to 104 0 25 50 75 100 125 Setting F i g . F.2 A t t e n u a t o r c a l i b r a t i o n r e s u l t s G e n e r a l M i c r o w a v e M o d e l 3455. 105 Setting Fig. F.3 Phase shifter calibration results General Microwave Model 7728. APPENDIX G ENVIRONMENTAL TESTING CHAMBER A testing chamber was constructed by lining the interior 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 in front of the horns provide an insulating layer. The effect of this styrofoam on the microwave parameters is minimal because i t has low dielectric 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 Fig. G1 and can cool the chamber down to -20°C. A rotatable stand holds and orients the sample for any incident polarization angle. Fig. G.1 View of the environmental testing chamber. 106 APPENDIX H DETAILED EXPERIMENTAL DATA Figs. H.1 to H.8 show attenuation vs phase shift plots for various constant specific gravities and moisture contents for Hemlock using transverse polarization. Figs. H.9 to H.19 show a l l the experimental results obtained using Douglas Fir samples and transverse polarization. 107 435 410-3 HEMLOCK transverse polarization Legend ° samplel » sample2 • sample3 6 8 10 12 14 16 Attenuation (dB) 18 20 22 24 F i g . H.1 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(0.36,0.38) 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-^ 360 - i 335 -j 310-j 285 -j 260- i 235 4 210 4 185-j 160-j 135 4 110 -j 85 1~ H E M L O C K transverse polarization •pacific gro«lt)r«0.S0 4 T 8 10 — r -12 14 "T -16 18 20 T 22 24 Attenuation (dB) Legend ' samplel > sample2 K sample3 ' sample4 > sample5 ' sample6 • sample7 • sample8 > sample9 F i g . H.2 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(0.43,0.50) 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-. 360 \ 335-i 310-j 285 \ 260-i 235-i 210-! 185 \ 160 \ 135-! 110-j 85 J -HEMLOCK transverse polarization Sp.ciflc G r a . l t y I O . S J Legend ° samplel 4 s a m p l e 2 "i—1—r_ ,~i—1—r "i—•—r 2 4 6 8 10 12 14 16 18 20 22 24 Attenuation (dB) Fig. H.3 Phase shift as a function of attenuation. Specific gravity constant(0.54,0.63). Hemlock: transverse polarization. Fig. H.4 Phase shift as a function of attenuation. Specific gravity constant(0.64). Hemlock: transverse polarization. Fig. H.5 Phase shift as a function of attenuation. Moisture content constant(0%,3%). Hemlock: transverse polarization. Fig. H.6 Phase shift as a function of attenuation. Moisture content constant(6%,9%). Hemlock: transverse polarization. Fig. H.7 Phase shift as a function of attenuation. Moisture content constant(12%,15%). Hemlock: transverse polarization. 435 i 60 i— ' — i — i— i — i— i — ' — i — ' — i — 1 — i — 1 — i — 1 — i — i— i — 1 — i — ' — i 0 2 4 6 8 10 12 14 16 18 20 22 Attenuation (dB) Fig. H.8 Phase shift as a function of attenuation. Moisture content constant(18%,21%). Hemlock: transverse polarization. DOUGLAS FIR frequency = 10.19 GHz transverse polariztion specific grovity = 0.*2 5 10 15 Moisture Content (%) i 20 Legend o samplel a sample2 • sample3 * sample4 Fig. H.9 Attenuation and phase shift as a function of moisture content for a typical specific gravity. Douglas F i r : transverse polarization. DOUGLAS FIR transverse polarization -J— 10 l 12 14 —r-16 18 Moisture Content (%) Legend A sg=0.42 x sg=0.50 • sg=0.54 H sg=0.57 Fig. H.10 Attenuation and phase shift as a function of moisture content for various specific gravities. Douglas F i r : transverse polarization. 16 14 12 -3 1 0 c o '•5 8 3 C 5 6 DOUGLAS FIR transverse polarization 0.40 0.45 0.50 Specific Gravity 0.55 0.60 Legend mc=0%  mc=3%  mc=6" mc=9% mc=12^ 118 350 - i 300-% 250 cn C 200 - C CO 0) 0) O 150 X 0_ 100 50 DOUGLAS FIR transverse polarization 0.40 0.45 0.50 0.55 Specific Gravity 0.60 Legend mc=0%  mc=3%  mc=6% mc=9% mc=12% F i g . H.11 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 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 m o i s t u r e c o n t e n t s . D o u g l a s 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 . 4 3.5 DOUGLAS FIR transverse polarization 119 • sg=0.54 B sg=0.57 1 -) , 1 1 1 1 1 , 1 1 1 1 1 , p — i 1 , 1 0 2 4 6 8 10 12 14 16 18 Moisture Content (%) Fig. H.12 Permittivity as a function of moisture content for various specific gravities. Douglas F i r : transverse polarization. DOUGLAS FIR transverse polarization 0.40 0.45 0.50 0.55 Specific Gravity 0.60 Legend mc=0%  mc=3% mc =6% mc=9% mc=12% Fig. H.13 Permitttivity as a function of specific gravity for various moisture contents. Douglas F i r : transverse polarization. 400 121 Fig. H.14 Phase shift as a function of attenuation. Specific gravity constant(0.38,0.42). Douglas F i r : transverse polarization. 100 H 1—i 1 1 1 1 1 1 ' 1—1—i—' 1—'—i ' — i ' — i 0 2 4 6 8 10 12 14 16 18 20 Attenuation (dB) Fig. H.15 Phase shift as a function of attenuation. Specific gravity constant(0 . 4 7 , 0 . 5 4 ) . Douglas F i r : transverse polarization. Fig. H.16 Phase shift as a function of attenuation. Specific gravity constant(0.57,0.61). Douglas F i r : transverse polarization. 400 - i 350-124 DOUGLAS FIR transverse polarization a> £ CO "D O 0_ 300-£ 250-to 200-150-moisture content=0% 100-12 16 18 8 10 Attenuation (dB) 14 20 400-, 350 DOUGLAS FIR transverse polarization % 300-Oi 0 ^ 250-1c <s a 200 CL 150-moisture content=3% 100- ~~r~ 12 -"i— 14 6 8 10 Attenuation (dB) 16 18 20 Fig. H.17 Phase shift as a function of attenuation. Moisture content constant(0%,3%). Douglas F i r : transverse polarization. Fig. H.18 Phase shift as a function of attenuation. Moisture content constant(6%,9%). Douglas F i r : transverse polarization. Fig. H.19 Phase shift as a function of attenuation. Moisture content constant(12%). Douglas F i r : transverse polarization. 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 acquisition circuit 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 Fig. 1.6 View of interface board #2. 

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