THE MICROWAVE ENGINEERING HANDBOOK

VOLUME 1

Microwave components

Edited by

Bradford L. Smith International Patents Consultant and Engineer with the Alcatel group in Paris, France, and

Senior Member of the IEEE and the French SEE

and

Michel-Henri Carpentier Professor in the 'Grandes Ecoles', France,

Fei low of the IEEE and President of the French SEE

m CHAPMAN & HALL

London • Glasgow • New York • Tokyo • Melbourne • Madras

Contents

Contributors xv

Preface xvii

Historie timeline xx

1 Introduction to the microwave engineering handbook 1 1.1 What are microwaves? 1 1.2 What can microwaves do? 3 1.3 Microwave transmitters 6 1.4 Parameters influencing the choice of a transmitter 7 1.5 From the triode to MMICs 8 1.6 History of semiconduetor microwave devices 9 Bibliography 14

PART ONE MICROWAVE VACUUM ELECTRONICS 17

2 Microwave tubes 19 2.1 Introduction 19

2.1.1 Common principles 19 2.1.2 Microwave cireuits for electron tubes 21

2.2 Cathodes 24 2.2.1 Thermionic emission 25 2.2.2 Thermionic cathodes 28 2.2.3 Impregnated cathode Operation 31 2.2.4 Life considerations 31 2.2.5 Secondary emission 32

2.3 Vacuum techniques 34 2.3.1 Pumping techniques 34 2.3.2 Vacuum tightness measurements 35 2.3.3 Pumping methods 36 2.3.4 Vacuum maintenance 36

2.4 Materials for electron tubes 36 2.4.1 Metals 37 2.4.2 Dielectrics - 38 2.4.3 Magnetic materials 39

Bibliography 39

vi Contents

3 Power grid tubes 3.1 Vacuum diodes 3.2 The triode

3.2.1 Characteristic curve sets 3.2.2 Operating class

3.3 Tetrodes 3.3.1 High frequency Operation of grid tubes

3.4 Grid tube technology 3.4.1 Cathodes 3.4.2 Grids 3.4.3 Anodes 3.4.4 Cooling

4 Cross-field tubes 4.1 The electron beam 4.2 Electron interaction 4.3 Distributed-emission tubes

4.3.1 The magnetron 4.3.2 Distributed emission

Bibliography

5 Linear-beam tubes 5.1 Introduction 5.2 Electron beams for linear-beam tubes

5.2.1 General 5.2.2 Cathodes 5.2.3 Beam control

5.3 Beam-focusing 5.3.1 General 5.3.2 Focusing with uniform magnetic field 5.3.3 Periodic permanent magnet (PPM) focusing

5.4 Klystrons 5.4.1 General 5.4.2 Velocity modulation 5.4.3 The cavity resonator 5.4.4 Gain and bandwidth 5.4.5 Power and efficiency 5.4.6 Recent developments

5.5 Travelling wave tubes 5.5.1 Principles of Operation 5.5.2 Helix travelling wave tubes 5.5.3 Coupled-cavity TWTs 5.5.4 Efficiency improvements

Problem Bibliography

Contents vii

6 Fast-wave devices 111 6.1 Introduction 111 6.2 How can an electron beam interact with a fast wave? 111 6.3 Electron cyclotron masers and gyrotrons 113 6.4 The magnetron injection gun (MIG) 117 6.5 Characteristics of electron beams 118 6.6 Interaction of the electron beam with the RF fields 119 6.7 The resonant cavity 122 6.8 Power 124 6.9 Practical high power gyrotrons 125

6.10 Free electron lasers 126 Problem 129 References 131

7 Associated equipment for tubes 133 7.1 The role of modulators in radar 133

7.1.1 Definitions - general 133 7.1.2 The modulator and the radar function 134 7.1.3 Modulators and the tube used 134 7.1.4 Relations with neighbouring subassemblies 135

7.2 General schematic of modulators 135 7.2.1 General schematic 135 7.2.2 PFN molulator (pulse forming network) 137 7.2.3 Hard tube modulator 143 7.2.4 Grid tube modulator 144 7.2.5 Other types of modulators 145

7.3 Power supplies 147 7.3.1 Conventional unregulated power supplies 147 7.3.2 Conventional regulated power supplies 148 7.3.3 Chopped power supplies 150

7.4 Switches 153 7.4.1 Ideal and real Switches 154 7.4.2 Vacuum tube 155 7.4.3 Spark gap 157 7.4.4 Gas-filled thyratron 157 7.4.5 Thyristor—RBDT—GTO—ZTO 158 7.4.6 MOS transistor-transistor 160 7.4.7 General problems related to the use of semiconductors 160

7.5 Stability 161 7.6 Measurements 162

7.6.1 Power measurements 162 7.6.2 Stability measurement 163

8 The laser 165 8.1 State and energy levels of the atom and molecule 165

viii Contents

.2

.3 ,4 ,5 6 7

Light absorption and emission Amplification of light Optical pumping Modes of a resonator Laser oscillation The main lasers 8.7.1 8.7.2 8.7.3 8.7.4 8.7.5 8.7.6 8.7.7 8.7.8

The ruby lasers The neodymium lasers The dye lasers The He-Ne laser The C0 2 laser The argon and krypton ions lasers The excimer lasers The other lasers

166 167 168 169 170 171 171 173 173 174 176 177 178 179

PART TWO SOLID STATE DISCRETE DEVICES 181

9 p-i-n and varactor diodes 183 9.1 Introduction 183 9.2 Physical behaviour of a p-i-n diode 184

9.2.1 Structure 184 9.2.2 Potential barrier p+n, p+-i-n+, p+-v-n+ and p+-7i-n+ 184 9.2.3 Capacitance voltage characteristic - punchthrough voltage 184 9.2.4 Dielectric relaxation frequency 187 9.2.5 Forward biased p-i-n diode 188 9.2.6 p-i-n diode in transient applications 190 9.2.7 Thermal behaviour of a p-i-n diode 192 9.2.8 Choice of a p-i-n diode 193 9.2.9 Equivalent circuit of the diode 195

9.3 Applications 195 9.3.1 p-i-n diode attenuators 195 9.3.2 Switching diodes 198 9.3.3 Phase shifters 201

9.4 Technology of the p-i-n diode 201 9.4.1 Raw material 201 9.4.2 Diode dimensions 202 9.4.3 Manufacturing of the diode 204

9.5 Electrical characteristics of diodes 204 9.6 Limiter p-i-n diodes 204

9.6.1 Main application 204 9.6.2 Working principle 206

9.7 Multiplier varactor 209 9.7.1 Main applications 209

Bibliography 212

Contents ix

IMPATT and Gunn diodes 213 10.1 General 213 10.2 IMPATT diodes (IMPact ionization mode Avalanche

Transit Time) 213 10.3 Gunn diodes 216

10.3.1 Comparative intrinsic properties of GaAs, GalnAs and InP TEDs 218

10.3.2 Possible operating modes 221 10.3.3 Operating mechanisms of n+-n-n+ devices 225

10.4 Comparative noise behaviour of IMPATT and Gunn diodes 225 10.5 Power generation, thermal effects 227

10.5.1 CWcase 228 10.5.2 Pulsed Operation 228

10.6 Harmonie Operation 228 References 229

Schottky diodes for reeeption 231 11.1 General 231 11.2 Current and depletion layer capacitance of a Schottky

diode 232 11.2.1 Forward current 232 11.2.2 Reverse current 234 11.2.3 Depletion layer capacitance 234

11.3 Practical realization and equivalent cireuits 234 11.3.1 Equivalent cireuit of the chip 235 11.3.2 Equivalent cireuit of the packaged Schottky diode 236

11.4 Application of discrete Schottky diodes 237 Reference 237

Diodes: associated cireuits 239 12.1 Schottky barrier diodes and p+junetion diodes:

equivalent cireuits 239 12.2 Variable conductance of a Schottky diode for use as a

detector 241 12.3 Variable capacitance of a diode for use in voltage control

oscillators 243 12.4 p-i-n diode switches 246

12.4.1 Equivalent cireuit: reverse bias cireuit condition 246 12.4.2 Equivalent cireuit: forward bias conditions 247 12.4.3 Simplified equivalent cireuit 247 12.4.4 Reflection type switches, parallel diodes 247 12.4.5 Reflection type switches, series diodes 248 12.4.6 Matched switches 250 12.4.7 SPNT switches 250

Contents

12.5 p-i-n diode phase shifters 253 12.5.1 Loaded line phase shifters 253 12.5.2 Reflection type phase shifter 255

12.6 Diodes in negative resistance amplifiers: IMPATT and Gunn diodes 256 12.6.1 General principle of Operation 256 12.6.2 Stability condition 257 12.6.3 Bandwidth 258

12.7 Power combining of diodes (IMPATT and Gunn diodes) 259 12.7.1 Impedance levels within the combiner 259 12.7.2 Parasitic oscillations 260

Microwave transistors 261 13.1 Introduction 261

13.1.1 Bipolartransistors 261 13.1.2 FET 263

13.2 Microwave Silicon bipolar transistors 264 13.2.1 Theory and design 264 13.2.2 Microwave power transistors 277 13.2.3 Microwave bipolar transistor manufacture 295

References 300

MESFET Operation principles and device modelling 303 14.1 Charge control principles and basic equations 303 14.2 Large drain voltage effects 307 14.3 Saturated drain current threshold voltage, transconductance,

gate source and gate drain capacitances 308 14.4 Remarks concerning various parasitic effects 309

14.4.1 Intrinsic input resistance 309 14.4.2 Output conductance in Saturation 310 14.4.3 Gate resistance 311 14.4.4 Source resistance 312 14.4.5 Other special aspects related to recessed structures 313 14.4.6 Wiring inductances and input/output parasitic

capacitances 313 14.5 Equivalent circuit and various gain expressions 313

14.5.1 Power gain expression 315 14.6 Class A power MESFET 316

14.6.1 Power dependence 317 14.7 Low noise MESFETs 318

14.7.1 General theory of noisy quadrupoles 318 14.7.2 Noise figure definition 319 14.7.3 Noise sources in MESFETs 321

Contents xi

15 GaAs FET manufacture technology Thomson-CSF 323 15.1 Introduction 323 15.2 Tools and principles 325

15.2.1 Material aspects 325 15.2.2 Lithographie tools 328 15.2.3 Metallization 330 15.2.4 Dielectric deposition/passivation 331 15.2.5 Dry etching techniques 333

15.3 Basic process 333 15.3.1 Device isolation 333 15.3.2 Ohmic contacts 333 15.3.3 Gate definition 334

15.4 Two-dimensional electron GaAs FET (TEGFET or HEMT) 335 15.4.1 Introduction 335 15.4.2 Principles of Operation 335 15.4.3 Advantages of TEGFETs (HEMTs) 337

15.5 Conclusions 338

PART THREE OPTO-ELECTRONICS AND INFRARED COMPONENTS 339

16 Solid-state opto-electronic devices 341 16.1 General introduction 341 16.2 Optical fibres 342

16.2.1 Losses 348

17 Optical sources 349 17.1 Emission and absorption of radiation in semiconduetors 349 17.2 The laser diode 354

17.2.1 Laser diode geometry 354 17.2.2 Electrical properties: electron and hole injeetion and

confinement by heterojunetion 355 17.2.3 Waveguiding in a laser diode: optical confinement 356 17.2.4 Optical feedback in a laser diode and threshold

conditions 359 17.2.5 Main characteristics of laser diodes 362

17.3 Direct modulation 362 17.4 External modulation of a CW source 365

17.4.1 Introduction to integrated optics 365 17.4.2 A review of some modulator/switch struetures 367 17.4.3 RF modulation in integrated optics 369 17.4.4 Intrinsic resonance in integrated optics 373 17.4.5 Short synthesis on external modulation 376

17.5 Solid-state photodetectors 377

xii Contents

17.5.1 Detection of RF-modulated radiation 377 17.5.2 Optical link energy budget 381

References 382

18 Infrared passive sensors 385 18.1 General 385 18.2 Multiplexed focal plane arrays 388

18.2.1 Advantages of multiplexed focal plane arrays 388 18.2.2 State-of-the-art detectors multiplexed within the

focal plane 390 18.2.3 The IRCCD concept - a universal concept 392

18.3 Example of IRCCD technology 393 18.3.1 Sensor technology 394 18.3.2 Hybridization technology 398 18.3.3 Silicon technology 398

18.4 Definition and calculation of an IRCCD component 398 18.4.1 Photovoltaic detectors 398 18.4.2 Readout circuit 402 18.4.3 Dispersions 410

18.5 How to specify an IRCCD component 410 18.5.1 Introduction 410 18.5.2 Parameters to be defined 411

18.6 Cryogeny for focal plane arrays 415 18.6.1 Introduction 415 18.6.2 Main operational cooling Systems 415 18.6.3 Encapsulations 419

PARTFOUR ANALYTICAL METHODS 423

19 Passive theory and devices 425 19.1 Basic Solutions to the problem of guided wave propagation 425

19.1.1 Equations of guided waves 425 19.1.2 Types of Solutions 426

19.2 Guiding structures 427 19.2.1 Homogenous structures 427 19.2.2 Non-homogeous guiding structures 434

19.3 Junctions in waveguides and lines 443 19.3.1 Scattering waves 443 19.3.2 Modelling of multi-port circuits 453

19.4 Microstrip discontinuities 456 19.4.1 Effect of discontinuities on propagation 456 19.4.2 Modelling 457 19.4.3 Some examples of discontinuities 461

19.5 Passive elements and microwave circuits - examples 463

Contents xiii

19.5.1 Elements 463 19.5.2 Circuits 464

Bibliography 480

20 CAD Software 481 20.1 General goals of CAD tools 481 20.2 History 482 20.3 The components of a CAD chain 483 20.4 Major Simulation functions 484

20.4.1 Analysis functions 484 20.4.2 Optimization functions 486

Index 491