Microwave Engineering: Concepts and Fundamentals

770 Pages·2014·58 MB·English

by  Ahmad Shahid Khan

EnginEEring - ElEctrical K
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a Microwave
“… demonstrates a good understanding of the author’s knowledge of
n
microwave engineering. The book has extensive practical applications
and a wide variety of problems with worked solutions. it is written in
engineering
such a way that the reader, through personal study, could achieve a
s atisfactory education on the subject.”
—Brian Klaveness, Principal lecturer and Programme leader at glyndwr University,
Wrexham, UK
ConCepts and
e
M
Detailing the active and passive aspects of microwaves, Microwave Fundamentals
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Engineering: Concepts and Fundamentals covers everything from wave
propagation to reflection and refraction, guided waves, and transmission
i
g
lines, providing a comprehensive understanding of the underlying principles
c
at the core of microwave engineering. This encyclopedic text not only
encompasses nearly all facets of microwave engineering, but also gives all i
topics—including microwave generation, measurement, and processing— r
n
equal emphasis. Packed with illustrations to aid in comprehension, the book:
• Describes the mathematical theory of waveguides and o
e
ferrite devices, devoting an entire chapter to the Smith chart
and its applications
ew
• Discusses different types of microwave components, antennas,
tubes, transistors, diodes, and parametric devices
r
• Examines various attributes of cavity resonators, semiconductor
a
and RF/microwave devices, and microwave integrated circuits
• Addresses scattering parameters and their properties, as well as i
v
planar structures including striplines and microstrips n
• Considers the limitations of conventional tubes, behavior of charged
e
particles in different fields, and the concept of velocity modulation
g
Based on the author’s own class notes, Microwave Engineering: Concepts
and Fundamentals consists of 16 chapters featuring homework problems,
references, and numerical examples. PowerPoint® slides and MATLAB®-
based solutions are available with qualifying course adoption.
K20512
ISBN-13: 978-1-4665-9141-7
90000
ahmad Shahid Khan
9 781466 591417
K20512_Cover_mech.indd All Pages 2/4/14 4:36 PM
MICROWAVE
ENGINEERING
CONCEPTS AND
FUNDAMENTALS

Microwave
engineering
ConCepts and
Fundamentals
ahmad Shahid Khan
Boca Raton London New York
CRC Press is an imprint of the
Taylor & Francis Group, an informa business
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Contents
Preface ................................................................................................................xxvii
Author .................................................................................................................xxix
1 Introduction .....................................................................................................1
1.1 Introduction ...........................................................................................1
1.2 Microwave Frequency Bands ..............................................................2
1.3 Advantages ............................................................................................3
1.4 Components of Microwave System ....................................................5
1.4.1 Microwave Generation ............................................................5
1.4.2 Microwave Processing ............................................................6
1.4.3 Microwave Transmission ........................................................6
1.4.4 Microwave Measurements .....................................................8
1.4.5 Microwave Antennas ..............................................................9
1.5 Applications ...........................................................................................9
1.5.1 Communication ........................................................................9
1.5.2 Radars ......................................................................................11
1.5.3 Radio Astronomy ...................................................................11
1.5.4 Navigation ...............................................................................12
1.5.5 Home Appliances ...................................................................12
1.5.6 Industrial Heating .................................................................13
1.5.7 Plasma Generation .................................................................13
1.5.8 Weaponry System ..................................................................13
1.5.9 Spectroscopy ...........................................................................13
1.6 Health Hazards ...................................................................................13
Descriptive Questions ...................................................................................14
Further Reading .............................................................................................14
2 Fundamentals of Wave Propagation .........................................................17
2.1 Introduction .........................................................................................17
2.2 Basic Equations and Parameters .......................................................17
2.3 Nature of Media ..................................................................................19
2.4 Wave in Lossless Media .....................................................................19
2.5 Wave in Lossy Media ..........................................................................21
2.6 Conductors and Dielectrics ...............................................................22
2.7 Polarisation ..........................................................................................24
2.8 Depth of Penetration ...........................................................................26
2.9 Surface Impedance ..............................................................................27
2.10 Poynting Theorem ..............................................................................27
2.11 Reflection and Refraction ...................................................................29
2.12 Direction Cosines, Wavelength and Phase Velocity ......................31
v
vi Contents
2.13 Classification of the Cases of Reflection ..........................................32
2.14 Normal Incidence Cases ....................................................................33
2.14.1 Perfect Conductor ..................................................................34
2.14.2 Perfect Dielectric ....................................................................35
2.15 Oblique Incidence ...............................................................................36
2.15.1 Perfect Conductor ..................................................................36
2.15.1.1 Perpendicular (or Horizontal) Polarisation ........36
2.15.1.2 Parallel (or Vertical) Polarisation ..........................36
2.15.2 Perfect Dielectric ....................................................................37
2.15.2.1 Perpendicular (Horizontal) Polarisation .............39
2.15.2.2 Parallel (Vertical) Polarisation ..............................39
2.15.2.3 Brewster’s Angle .....................................................39
2.15.2.4 Total Internal Reflection ........................................40
2.16 Parallel Plane Guide ...........................................................................40
2.17 Transverse Waves ................................................................................42
2.17.1 Transverse Electric Waves ....................................................42
2.17.2 Transverse Magnetic Waves .................................................44
2.18 Characteristics of TE and TM Waves ...............................................45
2.19 Transverse Electromagnetic Waves ..................................................47
2.20 Wave Impedances ...............................................................................48
2.21 Attenuation in the Walls of Parallel Plane Guide ...........................51
2.22 Transmission Lines .............................................................................53
2.23 Equations Governing Transmission Line Behaviour .....................54
2.23.1 Transmission Line Equations ...............................................54
2.23.2 Solution of Transmission Line Equations ...........................56
2.23.2.1 Exponential Form ...................................................56
2.23.2.2 Hyperbolic Form ....................................................57
2.24 Lossless RF and UHF Lines with Different Terminations ............58
2.25 Reflection Phenomena ........................................................................61
2.26 Resonance Phenomena in Line Sections .........................................62
2.27 Quality Factor of a Resonant Section ...............................................63
2.28 UHF Lines as Circuit Elements .........................................................63
2.29 Applications of Transmission Lines .................................................66
2.29.1 Quarter-Wave Section as Tuned Line .................................66
2.29.2 Quarter-Wave Section as Impedance Transformer ...........67
2.29.3 Quarter-Wave Section as Voltage Transformer .................67
2.29.4 Line Sections as Harmonic Suppressors ............................68
2.29.4.1 Suppression of Third Harmonics .........................68
2.29.4.2 Suppression of Even Harmonics ..........................69
2.29.5 Line Sections for Stub Matching .........................................69
2.29.5.1 Single Stub Matching .............................................69
2.29.5.2 Double Stub Matching ...........................................70
2.30 Types of Transmission Lines .............................................................70
2.31 Coaxial Cables .....................................................................................71
2.32 Limitations of Different Guiding Structures ..................................73
Contents vii
Problems ..........................................................................................................84
Descriptive Questions ...................................................................................85
Further Reading .............................................................................................86
3 Waveguides ....................................................................................................87
3.1 Introduction .........................................................................................87
3.2 Interrelation between Transmission Line and Waveguide ...........87
3.2.1 Impact of Frequency Change ...............................................89
3.3 Rectangular Waveguide .....................................................................90
3.3.1 Transverse Magnetic Wave ...................................................93
3.3.2 Transverse Electric Wave ......................................................96
3.3.3 Behaviour of Waves with Frequency Variation .................96
3.3.4 Possible and Impossible Modes ...........................................97
3.3.4.1 Lowest Possible TM Mode ....................................97
3.3.4.2 Lowest Possible TE Mode ......................................97
3.3.4.3 Impossibility of TEM Wave ..................................97
3.3.5 Field Distribution for Different Modes ...............................98
3.3.5.1 TE Wave ...................................................................98
3.3.5.2 TM Wave ..................................................................99
3.3.6 Excitation of Modes .............................................................100
3.3.6.1 TE Modes ...............................................................100
3.3.6.2 TM Modes .............................................................100
3.3.7 Wave Impedances ................................................................101
3.3.7.1 TM Wave ................................................................101
3.3.7.2 TE Wave .................................................................101
3.3.7.3 Variation of Z , υ and λ with Frequency ...........102
z
3.3.8 Circuit Equivalence of Waveguides ..................................103
3.3.8.1 TM Wave ................................................................103
3.3.8.2 TE Wave .................................................................105
3.3.9 Power Transmission in Rectangular Waveguide ............106
3.3.10 Attenuation in Waveguides ................................................107
3.3.11 Quality Factor .......................................................................108
3.4 Circular Waveguide ..........................................................................109
3.4.1 TM Waves ..............................................................................111
3.4.2 TE Waves ...............................................................................112
3.4.3 Solution of Wave Equation .................................................112
3.4.3.1 Field Expressions for TM Wave ..........................114
3.4.3.2 Field Expressions for TE Wave ...........................115
3.4.4 TEM Modes in Circular Waveguide .................................116
3.4.5 Mode Designation in Circular Waveguide ......................117
3.4.6 Field Distribution in Circular Waveguide ........................118
3.4.7 Mode Excitation....................................................................119
3.4.8 Cutoff Frequencies ...............................................................119
3.4.9 Attenuation in Circular Waveguides ................................119
3.5 Dielectric Waveguides ......................................................................119
viii Contents
3.5.1 Dielectric Slab Waveguide ..................................................120
3.5.2 Dielectric Rod Waveguide ..................................................123
3.6 Physical Interpretation of Wave Terminology ..............................124
3.6.1 Modes ....................................................................................124
3.6.2 Mode Designations ..............................................................124
3.6.3 Dominant Mode ...................................................................124
3.6.4 Cutoff Frequency ..................................................................125
3.6.5 Usable Frequency Range .....................................................125
3.6.6 Characteristic Impedance ...................................................125
3.6.7 Guide Wavelength ...............................................................125
3.6.8 Phase Velocity.......................................................................125
3.6.9 Group Velocity......................................................................125
3.6.10 Transformation of Modes ...................................................126
3.6.11 Mode Disturbance ...............................................................126
3.6.12 Multimode Propagation ......................................................126
3.6.13 Group Velocity Variations ..................................................127
3.6.14 Wavefront Movement ..........................................................128
3.6.15 Spurious Modes ...................................................................128
3.7 Relative Merits of Waveguides ........................................................129
3.7.1 Copper Losses ......................................................................129
3.7.2 Dielectric Loss ......................................................................129
3.7.3 Insulation Breakdown .........................................................129
3.7.4 Power-Handling Capability ...............................................130
3.7.5 Radiation Losses ..................................................................130
3.8 Limitations of Waveguides ..............................................................130
Problems ........................................................................................................135
Descriptive Questions .................................................................................136
Further Reading ...........................................................................................137
4 Cavity Resonators .......................................................................................139
4.1 Introduction .......................................................................................139
4.2 Shapes and Types of Cavities ..........................................................140
4.2.1 Cavity Shapes .......................................................................140
4.2.2 Cavity Types .........................................................................140
4.2.3 Reentrant Cavities ................................................................142
4.2.3.1 Resonant Frequency .............................................143
4.3 Cavity Formation ..............................................................................144
4.3.1 Formation of a Rectangular Cavity ...................................144
4.3.2 Formation of a Cylindrical Cavity .....................................145
4.4 Fields in Cavity Resonators .............................................................145
4.4.1 Rectangular Cavity Resonator ...........................................146
4.4.1.1 Mode Degeneracy .................................................148
4.4.2 Circular Cavity Resonator ..................................................148
4.4.3 Semi-Circular Cavity Resonator ........................................150
4.5 Quality Factor ....................................................................................150
Contents ix
4.6 Coupling Mechanism .......................................................................154
4.7 Tuning Methods ................................................................................154
4.8 Advantages and Applications .........................................................155
4.9 Dielectric Resonators ........................................................................156
Problems ........................................................................................................160
Descriptive Questions .................................................................................160
Further Reading ...........................................................................................161
5 Microwave Ferrite Devices .......................................................................163
5.1 Introduction .......................................................................................163
5.2 Ferrites ................................................................................................165
5.3 Faraday’s Rotation .............................................................................167
5.4 Non-Reciprocal Ferrite Devices ......................................................168
5.4.1 Gyrators .................................................................................169
5.4.1.1 Gyrator with Input–Output Ports Rotated
by 90° ......................................................................169
5.4.1.2 Gyrator with 90° Twist .........................................170
5.4.2 Isolators .................................................................................170
5.4.2.1 Faraday’s Rotation Isolators ................................171
5.4.2.2 Resonance Isolator ...............................................172
5.4.3 Circulators .............................................................................173
5.4.3.1 Three-Port Circulators .........................................173
5.4.3.2 Four-Port Circulators ...........................................175
5.5 Ferrite Phase Shifter .........................................................................178
5.6 Ferrite Attenuators ............................................................................178
5.7 Ferrite Switches .................................................................................179
5.8 YIG Filters...........................................................................................179
5.9 Figures of Merit of Ferrite Devices .................................................180
Problems ........................................................................................................182
Descriptive Questions .................................................................................182
Further Reading ...........................................................................................183
6 Smith Chart ..................................................................................................185
6.1 Introduction .......................................................................................185
6.2 Characteristic Parameters of a Uniform Transmission Line ......185
6.3 Polar Chart .........................................................................................189
6.4 Smith Chart for Impedance Mapping ............................................191
6.5 Smith Chart for Admittance Mapping...........................................195
6.6 Information Imparted by Smith Chart ..........................................197
6.6.1 Mapping of Normalised Impedances ...............................197
6.6.2 Rotation by 180°....................................................................198
6.6.3 Reflection and Transmission Coefficients ........................198
6.6.4 Voltage Standing Wave Ratio .............................................200
6.6.5 Two Half-Wave Peripheral Scales ......................................200
6.6.6 Inversion of Impedance/Admittance ................................202