Transceiver and System Design for Digital Communications Scott R. Bullock, P.E. Third Edition B SCITEQ PUBLISHtN^INC. SciTech Publishing, Inc. Raleigh, NC
Contents Preface xvii About the Author xxiii Transceiver Design 1 1.1 Frequency of Operation 2 1.2 The Link Budget 4 1.3 Power in dbm 5 1.4 Transmitter 9 1.4.1 Power from the Transmitter 10 1.4.2 Transmitter Component Losses 10 1.4.3 Transmitter Line Losses from the Power Amplifier to Antenna 10 1.4.4 Transmitter Antenna Gain 11 1.4.5 Transmitter Antenna Losses 12 1.4.6 Transmitted EIRP 13 1.5 Channel 14 1.5.1 Free-Space Attenuation 14 1.5.2 Propagation Losses 15 1.5.3 Multipath Losses 16 1.6 Receiver 17 1.6.1 Receiver Antenna Losses 18 1.6.2 Receiver Antenna Gain 19 1.6.3 Receiver Line Losses from the Antenna to the LNA 19 1.6.4 Receiver Component Losses 20 1.6.5 Received Signal Power at the Output to the LNA 21 1.6.6 Receiver Implementation Loss 22 1.6.7 Received Power for Establishing the SNR of a System 23 1.6.8 Received Noise Power 23 1.6.9 Noise Figure 23 1.6.10 Received Noise Power at the Detector 25 1.6.11 Receiver Bandwidth 26 1.6.12 Received E b /N 0 at the Detector 27 1.6.13 Receiver Coding Gain 28 1.6.14 Required E b /N 0 28 1.6.15 Link Budget Example 28
VÜi I CONTENTS 1.6.16 Spread Spectrum Systems 32 1.6.17 Receiver Spreading Losses 32 1.6.18 Process Gain 32 1.6.19 Received Power for Establishing the SNR for a Spread Spectrum System 33 1.7 Summary 33 The Transmitter 35 2.1 Basic Functions of the Transmitter 36 2.1.1 Antenna 36 2.1.2 Transmit/Receive Control 37 2.1.3 Power Amplifier 38 2.1.4 Upconversion 38 2.1.5 Sum and Difference Frequencies Generated in the Upconversion Process 40 2.2 Voltage Standing Wave Ratio 41 2.2.1 Maximum Power Transfer Principle 42 2.3 Digital Communications 44 2.3.1 Digital versus Analog Communications 45 2.3.2 Baseband Modulation of Digital and Analog Systems 45 2.3.3 Software Programmable Radios and Cognitive Radios 46 2.4 Digital Modulation 47 2.4.1 Phase-Shift Keying 48 2.4.2 Binary Phase-Shift Keying 48 2.4.3 Differential Phase-Shift Keying 50 2.4.4 Quadrature (Quaternary) Phase-Shift Keying 50 2.4.5 Offset QPSK 52 2.4.6 Higher Order PSK 52 2.4.7 Variations in PSK Schemes 54 2.4.8 ir/4 Differential QPSK 54 2.4.9 Differential 8-Level PSK 54 2.4.10 16-Offset Quadrature Amplitude Modulation 56 2.4.11 Phasor Constellations and Noise Immunity 57 2.4.12 Continuous Phase PSK 59 2.4.13 Spectral Regrowth 59 2.4.14 Minimum Shift Keying 60 2.4.15 Frequency-Shift Keying 62 2.4.16 Sidelobe Reduction Methods 63 2.4.17 Ideal Shaping Filter 63 2.5 Direct Sequence Spread Spectrum 66 2.5.1 Frequency-Hopping Spread Spectrum 67 2.5.2 Spread Spectrum 69
CONTENTS I ix 2.5.3 Jammer Resistance 69 2.5.4 Despreading to Realize Process Gain in the Spread Spectrum System 72 2.5.5 Maximal Length Sequence Codes 73 2.5.6 Maximal Length PN Code Generator 74 2.5.7 Maximal Length PN Code Taps 75 2.5.8 Gold Codes 75 2.5.9 Other Codes 76 2.5.10 Spectral Lines in the Frequency Domain 76 2.6 Other Forms of Spread Spectrum Transmissions 77 2.6.1 Time Hopping 77 2.6.2 Chirped-FM 78 2.7 Multiple Users 79 2.7.1 Other Methods for Multiuser Techniques 81 2.7.2 Orthogonal Signals 81 2.7.3 Quadrature Phase Detection of Two Signals 82 2.7.4 Orthogonal Frequency Division Multiplexing 83 2.7.5 Other OFDM Techniques 86 2.8 Power Control 86 2.9 Summary 88 The Receiver 91 3.1 Superheterodyne Receiver 91 3.1.1 Basic Functions of the Receiver 92 3.2 Antenna 93 3.3 Transmit/Receive Control 93 3.4 Limiters 94 3.5 Image Reject Filter/Band Reject Filter 94 3.6 Dynamic Range/Minimum Detectable Signal 94 3.7 Types of DR 97 3.7.1 Amplitude DR 97 3.7.2 Frequency DR 97 3.7.3 Single-Tone Frequency DR 98 3.7.4 Two-Tone Frequency DR 98 3.8 Second- and Third-Order Intermodulation Products 99 3.9 Calculating Two-Tone Frequency DR 101 3.10 System DR 102 3.11 Tangential Sensitivity 104 3.12 Low-Noise Amplifier 105 3.13 Downconversion 107 3.14 Splitting Signals into Multiple Bands for Processing 108 3.15 Phase Noise 109
X I CONTENTS 3.16 Mixers 110 3.16.1 Mixer Spur Analysis 112 3.16.2 Sixth-Order Analysis 113 3.17 Bandwidth Constraints 114 3.18 Filter Constraints 114 3.19 Group Delay 116 3.19.1 Group Delay Compensation 117 3.20 Sampling Theorem and Aliasing 118 3.21 Anti-Aliasing Filter 119 3.22 Analog-to-Digital Converter 121 3.23 Digital Signal Processing 122 3.24 Summary 122 AGC Design and PLL Comparison 125 4.1 AGC Design 125 4.2 AGC Amplifier Curve 127 4.3 Linearizers 130 4.4 Detector 131 4.5 Loop Filter 134 4.6 Threshold Level 134 4.7 Integrator 135 4.8 Control Theory Analysis 136 4.8.1 AGC Design Example 140 4.9 Modulation Frequency Distortion 142 4.10 Comparison of the PLL and AGC Using Feedback Analysis Techniques 144 4.11 Basic PLL 145 4.12 Control System Analysis 146 4.13 Detector 146 4.14 Loop Filter 147 4.15 Loop Gain Constant 147 4.16 Integrator 148 4.17 Conversion Gain Constant 148 4.18 Control Theory Analysis 148 4.19 Similarities Between the AGC and the PLL 152 4.20 Feedback Systems, Oscillations, and Stability 152 4.21 Summary 153 Demodulation 157 5.1 Types of Demodulation 157 5.2 Pulsed Matched Filter 158 5.3 Digital Matched Filter Correlator 160
CONTENTS I xi 5.4 Pulse Position Modulation 162 5.5 Code Division Encoding and Decoding 164 5.6 Coherent versus Differential Digital Modulation and Demodulation 164 5.6.1 Coherent Demodulation 167 5.7 Carrier Recovery 167 5.7.1 Squaring Loop 168 5.7.2 Costas Loop 172 5.7.3 Modified Costas Loop and AFC Addition 173 5.8 Despreading Correlator 174 5.9 Symbol Synchronizer 177 5.10 The Eye Pattern 179 5.11 Digital Processor 181 5.12 Intersymbol Interference 181 5.13 Scrambler/Descrambler 182 5.14 Phase-Shift Detection 182 5.15 Shannon's Limit 185 5.16 Summary 185 Basic Probability and Pulse Theory 189 6.1 The Gaussian Process 193 6.2 Quantization and Sampling Errors 195 6.3 Probability of Error 198 6.4 Probability of Detection and False Alarms 199 6.5 Pulsed System Probabilities Using the BDF 204 6.6 Error Detection and Correction 204 6.6.1 Error Detection 205 6.6.2 Error Detection Using Parity 205 6.6.3 Error Detection Using Checksum 206 6.6.4 Error Detection Using CRC 207 6.6.5 Error Correction 209 6.6.6 Error Correction using Redundancy 209 6.6.7 Forward Error Correction 210 6.6.8 Interleaving 210 6.6.9 Types of FEC 211 6.6.10 Block Codes 211 6.6.11 Linear Block Codes 212 6.6.12 Hamming Code 217 6.6.13 Convolutional Codes 220 6.7 Viterbi Decoder 220 6.7.1 Multi-h 221 6.8 Turbo and Low-Density Parity Check Codes 222 6.9 Theory of Pulse Systems 224
XÜ I CONTENTS 6.10 PN Code 226 6.11 Summary 227 Multipath 229 7.1 Basic Types of Multipath 230 7.2 Specular Reflection on a Smooth Surface 230 7.3 Specular Reflection on a Rough Surface 232 7.4 Diffuse Reflection 233 7.5 Curvature of the Earth 235 7.6 Pulse Systems (Radar) 236 7.7 Vector Analysis Approach 237 7.8 Power Summation Approach 238 7.9 Multipath Mitigation Techniques 239 7.9.1 Antenna Diversity 239 7.10 Summary 240 Improving the System Against Jammers 243 8.1 Burst Jammer 244 8.2 Adaptive Filter 247 8.3 Digital Filter Intuitive Analysis 248 8.4 Basic Adaptive Filter 250 8.5 Least Mean Square Algorithm 251 8.6 Digital/Analog ALE 253 8.7 Wideband ALE Jammer Suppressor Filter 258 8.8 Digital Circuitry 259 8.9 Simulation 260 8.10 Results 261 8.11 Amplitude and Phase Suppression Results 261 8.12 Gram-Schmidt Orthogonalizer 266 8.13 Basic GSO 268 8.14 Adaptive GSO Implementation 270 8.15 Intercept Receiver Comparison 272 8.16 Summary 275 Global Navigation Satellite Systems 279 9.1 Satellite Transmissions 279 9.2 Data Signal Structure 281 9.3 GPS Receiver 282 9.4 Atmospheric Errors 282 9.5 Multipath Errors 283 9.6 Narrow Correlator 283 9.7 Selective Availability 285 9.8 Carrier Smoothed Code 286
CONTENTS I xiii 9.9 Differential GPS 287 9.10 DGPS Time Synchronization 288 9.11 Relative GPS 289 9.12 Doppler 291 9.13 Kinematic Carrier Phase Tracking 291 9.14 Double Difference 292 9.15 Wide Lane/Narrow Lane 293 9.16 Other Satellite Positioning Systems 294 9.17 Summary 295 Satellite Communications 297 10.1 Communications Satellites 297 10.2 General Satellite Operation 298 10.2.1 Operational Frequencies 299 10.2.2 Modulation 300 10.2.3 Adaptive Differential Pulse Code Modulation 301 10.3 Fixed Satellite Service 301 10.4 Geosynchronous and Geostationary Orbits 302 10.5 Ground Station Antennas 303 10.5.1 Types of Antennas Used in Satellite Communications Systems 304 10.6 Noise and the Low-Noise Amplifier 306 10.6.1 Equivalent Temperature Analysis 306 10.7 The Link Budget 309 10.7.1 Effective Isotropic Radiated Power 309 10.7.2 Propagation Losses 309 10.7.3 Received Power at the Receiver 310 10.7.4 Carrier Power/Equivalent Temperature 312 10.8 Multiple Channels in the Same Frequency Band 312 10.9 Multiple Access Schemes 313 10.10 Propagation Delay 314 10.11 Cost for Use of the Satellites 314 10.12 Regulations 314 10.13 Types of Satellites Used for Communications 314 10.14 System Design for Satellite Communications 316 10.15 Summary 316 Broadband Communications and Networking 319 11.1 Mobile Users 319 11.2 Types of Distribution Methods for the Home 320 11.2.1 Power Line Communications 321 11.2.2 Orthogonal Frequency Division Multiplexing 321 11.3 Home Phoneline Networking Alliance 322
Xiv I CONTENTS 11.4 Radio Frequency Communications 322 11.4.1 IEEE 802.11 323 11.4.2 Bluetooth 324 11.4.3 WiMAX 326 11.5 Military Radios and Data Links 327 11.5.1 The Joint Tactical Radio System 327 11.5.2 Software Defined Radios 328 11.5.3 Software Communications Architecture 329 11.5.4 JTRS Radios (Clusters) 329 11.5.5 Waveforms 330 11.5.6 JTRS Network Challenge 331 11.5.7 Gateway and Network Configurations 331 11.5.8 Link 16 336 11.5.9 Link 16 Modulation 337 11.5.10 Time Division Multiple Access 338 11.5.11 "Stacked" Nets 338 11.5.12 Time Slot Reallocation 338 11.5.13 Bit/Message Structure 338 11.6 Summary 339 Direction Finding and Interferometer Analysis 341 12.1 Interferometer Analysis 342 12.2 Direction Cosines 342 12.3 Basic Interferometer Equation 344 12.4 Three-Dimensional Approach 345 12.5 Antenna Position Matrix 347 12.6 Coordinate Conversion Due to Ktch and Roll 349 12.7 Using Direction Cosines 350 12.8 Alternate Method 352 12.9 Summary 354 Answers 355 Chapter 1 355 Chapter 2 356 Chapter 3 360 Chapter 4 361 Chapter 5 362 Chapter 6 363 Chapter 7 364 Chapter 8 366 Chapter 9 367 Chapter 10 368 Chapter 11 368 Chapter 12 369
CONTENTS I xv Appendix 371 Appendix A 371 Appendix В 375 Appendix С 377 Appendix D 379 Index 381