Microwave Devices and Circuit Design

Transcription

1 Microwave Devices and Circuit Design Ganesh Prasad Srivastava Vijay Laxmi Gupta

2 MICROWAVE DEVICES and CIRCUIT DESIGN GANESH PRASAD SRIVASTAVA Professor (Retired) Department of Electronic Science University of Delhi VIJAY LAXMI GUPTA Reader Department of Electronic Science University of Delhi

3 MICROWAVE DEVICES AND CIRCUIT DESIGN Ganesh Prasad Srivastava and Vijay Laxmi Gupta 2006 by PHI Learning Private Limited, Delhi. All rights reserved. No part of this book may be reproduced in any form, by mimeograph or any other means, without permission in writing from the publisher. ISBN The export rights of this book are vested solely with the publisher. Fifth Printing November, 2013 Published by Asoke K. Ghosh, PHI Learning Private Limited, Rimjhim House, 111, Patparganj Industrial Estate, Delhi and Printed by Syndicate Binders, A-20, Hosiery Complex, Noida, Phase-II Extension, Noida (N.C.R. Delhi).

4 Contents Preface ix 1. INTRODUCTION Microwave Engineering Microwave Frequencies An Overview of Applications of Microwaves Bandwidth Electromagnetic Noise Antenna Size and Reflection from Targets Microwave Interaction with Materials Stable Oscillation Frequencies Microwave Circuits Microwave Matching Networks Historical Landmarks First Experiments in Radio Communications Electromagnetic Theory of Radiation First Waveguide Development of Microwave Tubes Ferrite Devices Satellite Communication Solid State Devices Microwave Transistors In This Text 5 Suggested Further Reading 6 2. TRANSMISSION LINES Introduction Circuit Model of a Transmission Line Wave Propagation Constant Characteristics Impedance, Z 0 12 iii

5 iv CONTENTS 2.3 Physical Significance of Propagation Constant Equations Propagation Factor and Characteristic Impedance of Transmission Line Ideal or Lossless Line Line with Low Losses Waveform Distortions The Open Two-wire Line The Coaxial Line Transmission Line at High Frequencies Impedance and Admittance of Short-circuited and Open-circuited Lines Short-circuited Line Open-circuited Line Q(Quality Factor) of Resonant Lines Quarter-wave Line Impedance Matching by Stubbing Impedance Measurement Using Transmission Lines Solved Examples 42 Questions 51 Suggested Further Reading PLANAR TRANSMISSION LINES Introduction The Symmetrical Strip Transmission Lines Geometry of Special Planar Transmission Lines Characteristics of Transmission Lines Electrostatic Solution Design Formulas Substrate Materials Criteria for Substrate Selection The Stripline The Coplanar Waveguide The Slot Line Fin Lines 82 Questions 84 References THE SCATTERING MATRIX Introduction Network Representation Impedance Representation Admittance Representation Hybrid Representation G-Parameter Representation ABCD-Parameter Representation Inverse Chain Parameters Parameter Conversion 93

6 CONTENTS v 4.4 Scattering Parameters Conversion of S-Parameters into Other Network Parameters General Properties of Scattering Matrices of Linear Lossless Microwave Devices Application of Scattering Matrix Concepts to Tees Magic or Hybrid Tee Alternative Microstrip Realization of Hybrid Junction (Magic Tee) Translation of Reference Planes Scattering Matrix of Some Simple Microwave Devices Additional Examples Flow Graphs of Two-port Devices Signal Flow Graph for Three- and Four-port Devices Three-port Devices Four-port Devices Crossing Some Aspects of a Two-port Junction Scattering Matrix Shunt Susceptance jb Series Reactance jx Scattering Transfer Parameters 140 Questions 143 References 147 Suggested Further Reading SMITH CHART AND IMPEDANCE MATCHING Introduction Decibels and Nepers Derivation of Reflection Coefficient (Expression Based on Simple Transmission Line Equations) The Smith Transmission Line Chart Application of Smith Chart Determination of Unknown Impedance Impedance Matching Quarter-wave Transformer Quarter-wave Transformers with Extended Bandwidth Stub-matching Using Smith Chart Matching with Three Stubs Compressed Smith Chart The Normalized Impedance and Admittance Smith Chart The Normalized Z Y Smith Chart Impedance Matching Using Lumped Elements Impedance Matching Networks Microstrip Matching Networks 203 Questions 214 References 220 Suggested Further Reading 220

7 vi CONTENTS 6. WAVEGUIDES, CAVITIES AND RESONATORS Introduction Rectangular Waveguides Solution of Wave Equations Transverse Electric (E z = 0) Mode Transverse Magnetic (H z = 0) Mode Power Flow in Rectangular Waveguides Circular Waveguides TM Wave Equation TE Modes in Circular Waveguides Resonant Cavities Rectangular Cavity Cylindrical Cavity Quality Factor of a Cavity Dielectric Resonators (DRs) Material Properties Modes of Operation 253 Questions 257 Suggested Further Reading SOLID STATE MICROWAVE DEVICES Introduction Bipolar Transistor Microwave Transistor Cut-off Frequency Microwave Characterization Device Geometry and Performance Field Effect Transistors MESFET Construction and Operation Transconductance and Output Resistance Capacitance Voltage Characteristics Second-order Effects Biasing a Microwave Transistor DC Biasing of a Microwave GaAs MESFET DC-Biasing Circuits for Microwave Silicon Transistor Biasing Circuit Design HEMT Devices Current Voltage Characteristics Small Signal Device Model Parasitic Inductances L S, L D, and L G Parasitic Resistances R S, R D, and R G Capacitances C GS, C GD, and C DS Transconductance, g m Output Conductance, g DS 286

8 CONTENTS vii 7.7 Microwave Semiconductor Diodes PIN Diodes PIN Diode Parameters PIN Diode Switches PIN Diode as a Phase Shifter IMPATT and Related Avalanche Transit Time Devices The Physics of IMPATT Diodes Avalanche Multiplication Output Power and Quality Factor Equivalent Circuit of IMPATT Diodes IMPATT Diode Oscillators and Amplifiers IMPATT Diode Power Combiners Gunn Diode Operating Principle Electron Dynamics in Negative Differential Mobility Medium Domain Formation Gunn Oscillation Mode LSA Diodes Practical Gunn Oscillators 312 Questions 314 References 315 Suggested Further Reading MICROWAVE COMPONENTS Introduction Lumped Elements for Microwave Integrated Circuits (MICs) Capacitive Elements Inductive Elements Resistive Elements Directional Coupler Waveguide Directional Couplers The Quadrature Hybrid Coupled-line Directional Coupler The Lange Coupler The Power Divider Resistive Divider Wilkinson Power Divider Frequency Behaviour Variable Power Dividers Some Waveguide Components Waveguide Variable Attenuation Dielectric Phase Shifter Quarter-wave Plate Half-wave Plate Precision Phase Shifter and Precision Attenuator 371

9 viii CONTENTS 8.7 Ferrite Non-reciprocal Devices Faraday Rotation Microwave Ferrite Devices Circulator 383 Questions 386 References MICROWAVE AMPLIFIERS AND OSCILLATORS Introduction Signal Flow Graph and Its Application to Microwave Circuit Design Applications Amplifier Stability Unconditional Stability Contant Gain Circles Unilateral Operation Unconditionally Stable Case S ii < Potentially Unstable Case ( S ii > 1) Figure of Merit (Unilateral Case) Simultaneous Conjugate Matching (Bilateral Case) Noise in Microwave Amplifiers Broadband Transistor Amplifier Design Balanced Amplifier Oscillator Design One-port Negative Resistance Oscillator Transistor Oscillator Dielectric Resonator Oscillator Some Common Facts 458 Questions 460 References 463 INDEX

10 Preface A thorough knowledge of microwave engineering is necessary for B.Tech. students pursuing courses in Electronics and Communication Engineering and M.Sc. students pursuing courses in Electronics Science. Though there are many good books covering Maxwell s equations and their application to analysis and synthesis of microwave circuits, the authors have endeavoured to write a textbook that particularly emphasizes two areas: (1) Scattering parameters and their relationships with other parameters like impedance, admittance, hybrid and ABCD, as during the analysis of microwave circuits, very often we have to switch from one system to another; (2) Smith chart, a design tool for microwave engineers, used in one form or the other for analyzing and synthesizing all microwave circuits. The concept of Smith chart is somewhat difficult to grasp, therefore, an attempt is made to clarify these concepts by solving several problems. As microwave engineering predominantly involves circuit analysis and design, the emphasis in this book is also on solving Maxwell s equations for different types of microwave transmission lines, like microstrip, stripline, coplanar, fin lines, and H-guides. In order to understand which type of line is to be used for a particular problem, the basic concepts of transmission lines are comprehensively explained. The bulky waveguide is gradually giving way to new types of transmission lines which have less weight and are smaller in size and therefore for many applications the waveguide circuits are being increasingly replaced. Earlier, the study of waveguides and microwave components was based on the field theory concept and solution of Maxwell s equations, but modern microwave engineering consists of study of planar components, monolithic integrated circuits, network analysis and active circuit design. Thus there is a need to study new tools and techniques to analyze these devices and circuits. For example, earlier, the open-circuit stubs were not used for tuning purposes because of spurious radiation, but now for miniature components the open-circuit configuration is often used. Many new active devices like bipolar and field effect transistors, and lumped microwave components are being widely used for the design of microwave amplifier and oscillator circuits. Dielectric resonators and low noise amplifiers are finding wide applications, hence their study has also been duly emphasized in this textbook. For high power and high frequency applications the microwave tubes are still used, but for low to moderate power applications the semiconductor devices are more suitable. Therefore, greater emphasis is placed in this text on the study of performance and geometry of microwave semiconductor devices. ix

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