RF and Baseband Techniques for Software Defined Radio

Transcription

1 RF and Baseband Techniques for Software Defined Radio Peter B. Kenington ARTECH HOUSE BOSTON LONDON artechhouse.com

2 Contents Preface Scope of This Book Organisation of the Text xi xi xi Acknowledgements xiii CHAPTER 1 Introduction What Is a Software-Defined Radio? The Requirement for Software-Defined Radio Introduction Legacy Systems The Benefits of Multi-standard Terminals Economies of Scale Global Roaming Service Upgrading Adaptive Modulation and Coding Operational Requirements Key Requirements Reconfiguration Mechanisms Business Models for Software-Defined Radio Introduction Base-Station Model Impact of OBSAI and CPRI Handset Model New Base-Station and Network Architectures Separation of Digital and RF Tower-Top Mounting BTSHoteling Smart Antenna Systems Introduction Smart Antenna System Architectures Power Consumption Issues Calibration Issues 21 v

3 Contents 1.8 Projects and Sources of Information on Software Defined Radio SDR Forum World Wide Research Forum (WWRF) European Projects 23 References 24 CHAPTER 2 Basic Architecture of a Software Defined Radio Software Defined Radio Architectures Ideal Software Defined Radio Architecture Required Hardware Specifications Digital Aspects of a Software Defined Radio Digital Hardware Alternative Digital Processing Options for BTS Applications Alternative Digital Processing Options for Handset Applications Current Technology Limitations A/D Signal-to-Noise Ratio and Power Consumption Derivation of Minimum Power Consumption Power Consumption Examples ADC Performance Trends Impact of Superconducting Technologies on Future SDR Systems 54 References 55 CHAPTER 3 Flexible RF Receiver Architectures Introduction Receiver Architecture Options Single-Carrier Designs Multi-Carrier Receiver Designs Zero IF Receiver Architectures Use of a Six-Port Network in a Direct-Conversion Receiver Implementation of a Digital Receiver Introduction Frequency Conversion Using Undersampling Achieving Processing Gain Using Oversampling Elimination of Receiver Spurious Products Noise Figure Receiver Sensitivity Blocking and Intercept Point Converter Performance Limitations ADC Spurious Signals Use of Dither to Reduce ADC Spurii Alternative SFDR Improvement Techniques Impact of Input Signal Modulation on Unwanted Spectral Products Aperture Error Impact of Clock Jitter on ADC Performance 111

4 Contents VII Impact of Synthesiser Phase Noise on SDR Receiver Performance Converter Noise Figure Influence of Phase Noise on EVM for a Linear Transceiver Introduction SVE Calculation Without Phase Noise Disturbance Approximation of a Local Oscillator Phase Noise Characteristic Incorporation of the LO Phase Noise into the EVM Calculation Example Results EVM Performance of a Multi-Stage System Relationship Between EVM, PCDE, andp 134 References 135 СИ ЛГИ К i Multi-Band and General Coverage Systems Introduction Multi-Band Flexible Receiver Design The Problem of the Diplexer RF Transmit/Receive Switch Switched Diplexers Diplexer Elimination by Cancellation Achieving Image Rejection Introduction Use of a High IF Image-Reject Mixing Dynamic Range Enhancement Feedback Techniques Feedforward Techniques Cascaded Non-Linearity Techniques Use of Diplexer Elimination, Image-Reject Mixing, and High Dynamic Range Techniques in a Receiver 179 References 180 Flexible Transmitters and PAs Introduction Differences in PA Requirements for Base Stations and Handsets Comparison of Requirements Linearisation and Operational Bandwidths Linear Upconversion Architectures Analogue Quadrature Upconversion Quadrature Upconversion with Interpolation Interpolated Bandpass Upconversion Digital IF Upconversion Multi-Carrier Upconversion Weaver Upconversion Non-Ideal Performance of High-Speed DACs 204

5 VIII Contents Linear Transmitter Utilising an RF DAC Use of Frequency Multiplication in a Linear Upconverter Constant-Envelope Upconversion Architectures PLL-Based Reference or Divider Modulated Transmitter PLL-Based Directly-Modulated VCO Transmitter PLL-Based Input Reference Modulated Transmitter Use of a Direct-Digital Synthesizer to Modulate a PLL-Based Transmitter A PLL-Based Transmitter Utilising Modulated Fractional-N Synthesis Broadband Quadrature Techniques Introduction to Quadrature Techniques Active All-Pass Filter Use of Highpass and Lowpass Filters Polyphase Filtering Broadband Passive All-Pass Networks Multi-Zero Networks Tunable Broadband Phase Splitter Lange Coupler Multiplier-Divider Techniques 228 References 229 ; *..'. Linearisation and RF Synthesis Techniques Applied to SDR Transmitters Introduction Power Amplifier Linearisation Techniques Predistortion Analogue Predistortion Feedforward Basic Operation Power Efficiency Maintaining Feedforward System Performance Performance Stabilisation Techniques Relative Merits of the Feedforward Technique Transmitter Linearisation Techniques Digital Predistortion Relative Merits of Predistortion Techniques Feedback Techniques RF Feedback Envelope Feedback Polar Loop Cartesian Loop RF Synthesis Techniques Polar RF Synthesis Transmitter Sigma-Delta Techniques Power Efficiency 296

6 IX 6.6 Summary of the Relative Merits of Various Linear Amplifier and Transmitter Techniques 297 References 301 Appendix A 90 Phase-Shift Networks 305 A.l General Structure 305 Reference 309 Appendix В Phase Noise in RF Oscillators 311 B.l Leesons Equation 311 B.1.1 SSB Phase Noise Characteristic of a Basic Oscillator. 311 B.l.2 Leesons Equation 311 References 312 Acronyms and Abbreviations 313 About the Author 319 Index 321