MICROWAVE ENGINEERING

MICROWAVE ENGINEERING SANJEEVA GUPTA B.Sc. (Electrical) Electronics Engineering DINESH ARORA B.Sc. (Electrical) Electronics Engineering SATYA BHUSHAN SARNA B.Sec. (Electrical)Electronics Engineering PRASHANT LONKAR B.Sc. (Electrical) Electronics Engineering KHANNA PUBLISHERS 4575/15, Onkar House, Ground Floor Darya Ganj, New Delhi-110002 Phones : 23243042, 27224179; Fax : 23243043 email : khannapublishers@yahoo.in website : khannapublishers.in

Published by : Romesh Chander Khanna & Vineet Khanna for KHANNA PUBLISHERS 2-B, Nath Market, Nai Sarak Delhi- 110 006 (India) All Rights Reserved [This book or part there of cannot be translated or reproduced in any form (except for review or criticism) without the written permission of the Author and the Publishers] ISBN No. 81-7409-087-8 Third Edition : 2015 Price :Rs. 95.00 Computer Typeset by : Steps Computers, D-2/77, Dayal Pur, Delhi 110 094 Printed at : Bright Printers, Phari Bhojla Delhi 110 006

Foreward Microwave system has rapidly developed in the last three or four decades. Microwave communication is now being very widely used. All these required rapid development of microwave components and equipment. In the last two decades there has been very progress in this branch of electronic engineering with the addition of solid state devices and microstrip elements. This is primarily due to it increasing diverse application to fields like radio astronomy, long distance communication, defense navigation and to study of physical and chemical properties of matter. The rapid progress in microwave electronics has created an increasing demand for trained microwave engineering personal which has resulted in introduction of many microwave courses in various universities, and engineering institutes. This is a field which is of equal interest to electrical engineers and as physicists. A student entering this field is confronted with scarcity of a comprehensive book. There are many books by foreign authors dealing with different aspects of microwaves. However, there are very few books written by Indian authors for Indian students. I hope the attempt made by Sanjeeva Gupta will be successful and provide a useful for microwave engineers and physicists. Sd/- Prof. G.P.Srivastava Project Incharge, Training of Manpower in the Field of Microwave Engineering, Department of Physics and Astrophysics, University of Delhi.

Preface With the widening of the communication systems, the new Microwave Technology has come up very fast. In the last one decade, the Indian Post and Telegraph Department has spread a network of microwave links throughout the country. Since then, large scale requirement of microwave engineers is being felt by the country. There is hardly any book available by Indian authors to cope with the needs of the students. This inspired the authors to prepare and present this book. The authors hope that this book will go a long way in solving the basic need of the students in the field of Microwave Engineering. The book is recommended for the students preparing for degree Engineering Examinations, M.Sc. (Electronics) or for UPSC Engineering Services Examination. This book has been written after consulting vast literature in the field of Microwave Engineering. The authors acknowledge with the due courtesy the sources consulted in the preparation of this book. The authors are grateful to their teachers. Prof. G.P. Shrivastava (Department of Physics and Astrophysics, University of Delhi), PRof. R.S. Shukla and S.P. Mathur of Delhi Collage of Engineering who are responsible for moulding our thinking on this subject. The authors are grateful to Mr. Naresh Gupta and Mr. s. Nariharan for their help in Proof reading. The authors are also highly grateful and obliged for the most cooperative attitude of Shri Romesh Chander Khanna during the course of preparation of this book. Finally, the authors will be highly obliged for any positive criticisms and suggestions from the readers for improving this book with an object to serve the student community in better way. Authors

Contents 1. Microwave Principles 1-45 1.1. Introduction 1 1.2. Microwave Band 2 1.3. Millimeter Wave Band 3 1.4. Historical Background 4 1.5. Velocity of Waves Propagation in media 7 1.6. Advantages of Microwave Line of Sight Communication 8 1.7. 1.8. Wave Propagation and Noise 10 1.9. Bending of Ray Path due to Atmospheric Refractivity Gradient 15 1.10. Estimation of Microwave Link Parameters 19 1.11. Application of Ray and Wave Theories in Microwave Links 30 2. Maxwell s Equations 46 58 2.1. Faraday s Law 46 2.2. Displacement Current 51 2.3. Maxewell s Second Equation 53 3. Transmission Lines 59-109 3.1. Introduction 59 3.2. Basic Transmission Line Equations 61 3.2.1. Distortions in Transmission Lines 66 3.2.2. Types of Transmission Lines 69 3.2.3. Impedence matching by use of stubes 81 3.2.4. Matching 83 3.2.5. Concept of Transmission Line Converted to Wave Guide 92 3.3. Electromagnetic Field Equations 95 3.4. Historical Background of Maxwell s Field Equations 97 3.5. Maxwell s Electromagnetic Field equations for Electromagnetic Waves 101 3.6. Electromagnetic Plane waves 102 3.7. Polarisation of Electromagnetic Waves 104 4. Wave Guids 110 133 4.1. Introduction 110 4.2. Phase Velocity and Group Velocity in a Wave Guide 111 4.3. Mathematical Analysis of Rectangular Wave Guides 113 4.4. Transmission of TM Waves in Rectangular Wave Guide 116

4.4.1. Propagation properties and cut off Frequencies for Rectangular Wave guide 119 4.5. Transelectric Waves (TE Waves) 122 5. Microwave Components 134-168 5.1. Wave Guide Tees 134 5.1.1. E-plane Tee 134 5.1.2. H-plane Tee 136 5.1.3. Magic Tee 137 5.2. Wave meters 140 5.3. Directional Couplers 143 5.4. Isolators and Circulators 147 6. High Frequency Effects and Scaling 169-187 6.1. Scaling in Ultra-High-Frequency Tubes 169 6.2. Problems Associated with Conventional Tubes At UHF 196 6.3. Tubes for Ultra-High-Frequency 184 7. Klystrons 188 208 7.1. Klystron 188 7.1.1. Velocity Modulation 190 7.2. Multi-cavity Klystrons 192 7.3. Mathematical Analysis of Two Cavity Klystron 192 7.4. Performance and Applications 197 7.5. Reflex Klystron 198 7.5.1. Operation 199 7.5.2. Transit Time 200 7.6. Mathematical Analysis for Reflex Klystron 201 7.6.1. Relationship between accelerating voltage and repeller voltage 203 7.6.2. Relation between repeller voltage and frequency of operation of reflex Klystron 204 7.6.3. Modes 205 7.6.4. Performance 207 7.6.5. Tunning 207 7.6.6. Repeller protection 207 8. Magnetron and Travelling Wave Tube 209 228 8.1. Magnetron 209 8.1.1. Constructional Features of a cavity Magnetron 210 8.1.2. Parallel Plate Magnetron 211 8.1.3. Cylindrical Magnetron 215 8.2. Mechanism of Oscillations in Magnetron 218 9. Microwave Measurements 229 247 9.1. Measurements of Power 229 9.1.1. Measurement of Low Microwave Powers 229 9.1.2. Bolometer Methods 230

9.1.3. Extension of Bolometers Methods 233 9.1.4. Other Methods 234 9.1.5. Measurement of Medium & High Microwave Powers 234 9.2. Measurement of Frequency and Wavelength 236 9.2.1. Frequency Measurement 236 9.2.2. Wavelength Measurement 236 9.2.3. Standing Wave Detector 237 9.3. Measurement of Impedence 237 9.4. SWR Measurement 237 9.5. Impedance Measurement 240 9.6. Measurement Attenuation 241 9.6.1. Power Ratio method 242 9.6.2. Substitution Method 242 9.7.1. Measurement of Q by Transmission 242 9.7.2. The Determination of Cavity Q by VSWR Measurement 243 9.7.3. Decrement Measurement of Q 245 9.8. Measurement of Noise Factor 246 10. Microwave Attenuation 248 259 10.1. Horn Antennas 248 10.2. Antennas with Parabolic Reflectors 251 11. Radar Systems 260 300 11.1. Basic Principles 261 11.2. Radar Equation 262 11.3. Factors Influencing Maximum Range 264 11.4. Effects of Noise 266 11.5. Powers and Frequencies used in Radar 267 11.6. (a) Basic Pulsed Radar System 269 11.7. Modulators 270 11.8. Receiver Bandwidth Requirements 273 11.9. Factors Governing Plus Characteristic 274 11.10. Duplexer 276 11.11. Moving Target Indicator(MTI) 279 11.12. Tracking Radar Systems and Search Radar System 284 12. Propagation of Microwave 301 324 12.1. Space Wave Propagation over Ideal Flat Earth 302 12.2. Effect of Curvature of an Ideal Earth 306 12.3. Various Other Considerations in Space Wave Propagation 307 12.4. Atmospheric Effects in Space Wave Propagation 311 12.4.1. Refraction of Rays and the Radio Horizon 312 12.5. Duct Propagation 314 12.6. Tropospheric Scattering and Reflection 316 12.7. Fading of Space Wave Signals 318 12.8. Satellite Communication 319

12.9. Synchronous Satellite 320 12.10. Satellite Antennas 321 12.11. Ground Stations 322 12.12. Ground Antennas 323 13. Semiconductor Microwave Devices 325 343 13.1. UHF and Microwave Transistors 325 13.2. Varactors and Multipliers 326 13.3. Characteristics of Varactor Diode 328 13.4. Parameteric Amplifiers 331 Appendix A 344 348 1. Stoke s Theorem 344 2. Divergence Theorem 346 Appendix B 349 359 1. Attenuators 349 2. Dielectric Phase Shifter 352 3. Cavity Resonators 353 4. Principle of operation 353 5. Resonant Frequency of Rectangular Cavity 357 6. Q of Cavity Resonators 358 Appendix C-Smith Chart and Graphic Solutions of Transmission Line 360 376 1. Smith Chart for Analytical Equations 360 2. Commercial Rectangular smith chart 364 3. Standing wave Ration from Smith Chart 365 4. Impedance Matching 368 5. Matching by Impedance Matching Device 369 6. Matching by Single Stub 370 7. Matching by Double Stub 371

1 Microwave Principles 1.1 Introduction Microwaves are radiowaves of very short wavelength. Basically radiowaves are electromagnetic waves the term radio being introduced from the concept of radiation of electromagnetic waves. Accordingly there should not be any lower or higher limits of the wavelengths. However, it is usual to confine the wavelength of radiowaves within certain limits to have electronics systems to generate, radiate and detect the radio waves, while infrared and optical waves are covered by systems called optoelectronic systems. Table I Radio wave bands Frequency band Frequency range Wavelength range Extra Low Frequency (ELF) < 3 KHz > 100,000 m Very Low Frequency (VLF) 3 30 KHz 100,000 10,000 m Low Frequency (LF) 30 300 KHz 10,000 1,000 m Medium Frequency (MF) 300 3000 MHz 1,000 100 m High Frequency (HF) 3 30 MHz 100 10 m Very High Frequency (VHF) 30 300 MHz 10 1 m Ultra High Frequency (UHF) 300 3000 MHz 100 10 cm Super High Frequency 3 30 GHz 10 1 cm (SHF) or Microwave Extra High Frequency (EHF) or Millimeterwave 30 300 GHz 10 1 mm

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