This is the first book primarily about the satellite payload of satellite communications systems. It represents a unique combination of practical systems engineering and communications theory. It tells about the satellites in geostationary and low-earth orbits today, both the so-called bent-pipe payloads and the processing payloads. The on-orbit environment, mitigated by the spacecraft bus, is described. The payload units (e.g. antennas and amplifiers), as well as payload-integration elements (e.g. waveguide and switches) are discussed in regard to how they work, what they do to the signal, their technology, environment sensitivity, and specifications. At a higher level are discussions on the payload as an entity: architecture including redundancy; specifications--what they mean, how they relate to unit specifications, and how to verify; and specification-compliance analysis (“budgets”) with uncertainty. Aspects of probability theory handy for calculating and using uncertainty and variation are presented. The highest-level discussions, on the end-to-end communications system, start with a practical introduction to physical-layer communications theory. Atmospheric effects and interference on the communications link are described. A chapter gives an example of optimizing a multibeam payload via probabilistic analysis. Finally, practical tips on system simulation and emulation are provided. The carrier frequencies treated are 1 GHz and above. Familiarity with Fourier analysis will enhance understanding of some topics. References are provided throughout the book for readers who want to dig deeper.
Payload systems engineers, payload proposal writers, satellite-communications systems designers and analysts, and satellite customers will find that the book cuts their learning time. Spacecraft-bus systems engineers, payload unit engineers, and spacecraft operators will gain insight into the overall system. Students in systems engineering, microwave engineering, communications theory, probability theory, and communications simulation and modelling will find examples to supplement theoretical texts.
Table of Contents
Preface xix
Acknowledgments xxi
About the author xxiii
Abbreviations xxv
1 Introduction 1
1.1 What This Book Is About 1
1.2 Payload 3
1.3 Conventions 6
1.4 Book Sources 7
1.5 Summary of Rest of the Book 7
References 9
Part I Payload
2 Payload’s On-Orbit Environment 13
2.1 What Determines Environment 13
2.2 On-Orbit Environment 20
2.3 General Effects of Environment on Payload 27
References 31
3 Antenna 33
3.1 Introduction 33
3.2 General Antenna Concepts 35
3.3 Single-Beam Reflector Antenna 48
3.4 Horn 54
3.5 Antenna Array 57
3.6 Reflector-Based Multibeam Antenna 64
3.7 Autotrack 68
Appendix 3.A 70
3.A.1 Decibel 70
3.A.2 Antenna Pattern of General Aperture 71
3.A.3 Antenna Pattern of Antenna Array 72
References 73
4 Filter and Payload-Integration Elements 79
4.1 Introduction 79
4.2 Impedance Mismatch 80
4.3 RF Lines for Payload Integration 82
4.4 Other Payload-Integration Elements Aside from Switch 94
4.5 Filter 97
4.6 Switch and Redundancy 111
Appendix 4.A 116
4.A.1 Filter Poles and Zeros 116
References 117
5 Low-Noise Amplifier And Frequency Converter 123
5.1 Introduction 123
5.2 Low-Noise Amplifiers and Frequency Converters in Payload 124
5.3 Intermodulation Products 126
5.4 Low-Noise Amplifier 127
5.5 Frequency Converter 132
Appendix 5.A 142
5.A.1 Formula for Integrating Phase Noise Spectrum 142
References 143
6 Preamplifier and High-Power Amplifier 147
6.1 Introduction 147
6.2 High-Power Amplifier Concepts and Terms 148
6.3 Traveling-Wave Tube Amplifier versus Solid-State Power Amplifier 153
6.4 Traveling-Wave Tube Amplifier Subsystem 155
6.5 Solid-State Power Amplifier 170
References 176
7 Payload’s Communications Parameters 181
7.1 Introduction 181
7.2 Gain Variation with Frequency 184
7.3 Phase Variation with Frequency 187
7.4 Channel Bandwidth 189
7.5 Phase Noise 190
7.6 Frequency Stability 190
7.7 Spurious Signals from Frequency Converter 191
7.8 High-Power Amplifier Nonlinearity 192
7.9 Spurious Signals from High-Power Amplifier Subsystem 192
7.10 Stability of Gain and Power-Out of High-Power Amplifier Subsystem 194
7.11 Equivalent Isotropically Radiated Power 195
7.12 Figure of Merit GTs 196
7.13 Self-Interference 199
7.14 Passive Intermodulation Products 201
Appendix 7.A 201
7.A.1 Antenna Testing 201
7.A.2 Relation of Gain and Phase Ripple 202
7.A.3 Independence of GTs on Reference Location 203
References 204
8 More Analyses for Payload Development 207
8.1 Introduction 207
8.2 How to Deal with Noise Figure 208
8.3 How to Make and Maintain Payload Performance Budgets 211
8.4 High-Power Amplifier Topics 223
8.5 How to Avoid Monte Carlo Simulations on Gaussian Random Variables 231
Appendix 8.A 232
8.A.1 Elements of Probability Theory for Payload Analysis 232
8.A.2 Definition of Random Variable and Probability Density Function 232
8.A.3 Mean, Standard Deviation, and Correlation 233
8.A.4 Sum of Random Variables 234
8.A.5 Gaussian Probability Density Function 235
8.A.6 Uniform and Panel-Illumination Probability Density Function 237
8.A.7 Standard Deviation of Drift of Unknown Magnitude and Direction 238
References 239
9 Processing Payload 241
9.1 Introduction 241
9.2 Capabilities of Current Processing Payloads 242
9.3 Digital-Processing Elements Common to Both Nonregenerative and Regenerative Payloads 245
9.4 Nonregenerative Processing-Payload 248
9.5 Regenerative Payload 250
References 254
Part II Payload in End-To-End Communications System
10 Principles of Digital Communications Theory 259
10.1 Introduction 259
10.2 Communications Theory Fundamentals 260
10.3 Modulating Transmitter 268
10.4 Filters 278
10.5 Demodulating Receiver 281
10.6 SNR, EsN0, and EbN0 293
10.7 Summary of Signal Distortion Sources 295
Appendix 10.A 297
10.A.1 Sketch of Proof that Pulse Transform and Signal Spectrum Are Related 297
References 298
11 Communications Link 299
11.1 Introduction 299
11.2 End-to-End CN0 300
11.3 Signal Power on Link 301
11.4 Noise Level on Link 311
11.5 Interference on Link 312
11.6 Link Budget 317
References 318
12 Probabilistic Treatment Of Multibeam Downlinks 321
12.1 Introduction 321
12.2 Multibeam-Downlink Payload Specifications 322
12.3 Repeater-Caused Variation of C and CIself and Nominal Value 324
12.4 Combining Antenna-Caused Variation into Repeater-Caused Variation 333
12.5 Payload-Caused Variation of C(IþN) 337
12.6 Combining Atmosphere-Caused Variation into Payload-Caused Variation 337
12.7 Optimizing Multibeam-Downlink Payload Specified on Link Availability 339
Appendix 12.A 340
12.A.1 Iteration Details for Optimizing Multibeam Payload Specified on Link Availability 340
12.A.2 Pdf of Diurnal Variation in Delta of East and West Panel Illumination 342
References 342
13 End-To-End Communications System Model With Focus On Payload 343
13.1 Introduction 343
13.2 Considerations for Both Software Simulation and Hardware Emulation 344
13.3 Additional Considerations for Simulation 352
13.4 Additional Considerations for Emulation 359
References 362
Index 363
