Software Defined Radio using MATLAB® & Simulink' and the RTL-SDR

Robert W. Stewart Kenneth W. Barlee Dale S. W. Atkinson Louise H. Crockett

Department of Electronic and Electrical Engineering University of Strathclyde Glasgow, Scotland, UK 1st Edition

Table of Contents Book and Support File Information

i

Foreword

xi

A Few SDR Thoughts

xiii

Preface

xv

Acknowledgements

xix

1

Introduction 1.1 Real Time Desktop Software Defined Radio 1.2 What is the RTL-SDR? 1.3 What Do I Need to Get Started? 1.4 The Aim and Objectives of this Book 1.5 The Evolution of the Software Defined Radio Architecture 1.6 RTL-SDR Hardware 1.7 Interfacing with the RTL-SDR from MATLAB and Simulink 1.8 Practicalities and Some Challenges of (Low Cost) Desktop SDR 1.9 Working with Discrete and Continuous Time Signals and Equations . . . . 1.10 The Structure of the Book and Format of the Exercises

1 2 3 5 7 8 10 17 20 22 22

2

Open the Box! First SDR with MATLAB and Simulink 2.1 Getting Started: Hardware and Software Checklist 2.2 Getting Started: Installing the RTL-SDR Hardware Support Package 2.3 Getting Started: Book Support Files and the MATLAB Environment 2.4 Running the First Desktop RTL-SDR Receiver Designs 2.5 Summary

25 25 27 31 34 42

3

Radio Frequency Spectrum Viewing

43

3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 3.10 3.11 3.12 3.13 3.14

44 45 46 49 52 53 54 60 64 75 79 83 89 97

4

Different Signals, Different Frequencies Spectrum Usage and Allocations Around the Globe Working with a Suitable Antenna Go Forth and Explore the Spectrum! Spectral Viewing — Spectrum Analyser and Waterfall Plots Spectral Viewing — RTL-SDR Tuner GUI Controls Engineering Requirements — Eyeball Radio Tuning & More FM Radio Stations Mobile (Cell) Phone Signals—2G, 3G and 4G 433MHz: Key Fobs and Wireless Sensors Digital Video & Audio Signals Using Multiple RTL-SDRs Sweeping the Spectrum: Receiving from 25MHz to 1.75GHz Summary

Getting Started with MATLAB and Simulink

99

4.1

100

Introducing MATLAB

Software Defined Radio Using MATLAB & Simulink and the RTL-SDR 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 4.10 4.11 4.12 4.13 4.14

MATLAB Functions Plotting in MATLAB MATLAB Arrays, Matrices, and Structures MATLAB System Objects Introducing Simulink Creating Simulink Models Variables and Parameters Generating Frequency Domain Plots Sampling Rates, Samples and Frames Data Types Working with Input and Output Files Saving and Re-importing RTL-SDR Data Summary

107 111 115 121 125 127 142 150 152 159 161 165 170

Complex Signals, Spectra and Quadrature Modulation 5.1 Real and Complex Signals — it's all Sines and Cosines 5.2 Viewing Real Signals in the Frequency Domain via Complex Spectra 5.3 Standard Amplitude Modulation 5.4 Quadrature Modulation and Demodulation (QAM) 5.5 Quadrature Amplitude Modulation using Complex Notation 5.6 Quadrature Amplitude Demodulation using Complex Notation 5.7 Spectral Representation for Complex Demodulation 5.8 Frequency Offset Error and Correction at the Receiver 5.9 Frequency Correction using a Complex Exponential 5.10 RTL-SDR Quadrature / Complex Architecture 5.11 Summary

171 172 173 182 187 191 192 195 199 199 201 201

Amplitude Modulation (AM) Theory and Simulation

203

6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 6.9

203 203 210 217 225 227 227 231 234

Amplitude Modulation — An Introduction AM-DSB-SC: Double Sideband Suppressed Carrier AM AM-DSB-TC: Double Sideband Transmitted Carrier AM AM-SSB: Single Sideband AM AM-VSB: Vestigial Sideband AM Theoretical AM Demodulation Receiving and Downconv AM-DSB-TC Signals to Complex Baseband... Non-Coherent AM Demodulation: The Envelope Detector Summary

Frequency Tuning and Simple Synchronisation 7.1 Selecting a Frequency Band: Tuning 7.2 The Synchronisation Problem 7.3 Demodulation of AM Signals 7.4 Coherent Demodulation and Carrier Synchrony 7.5 Introduction to Phase Locked Loops 7.6 Discrete Time PLL Model 7.7 PLL Behaviours, Parameters and Characteristics 7.8 PLL Design

235 235 238 241 242 245 252 256 264

Table of Contents

8

9

v

7.9 PLL Performance in Noise 7.10 Carrier Synchronisation 7.11 Summary

272 273 277

Desktop AM Transmission and Reception

279

8.1 8.2 8.3 8.4 8.5 8.6

280 290 310 316 326 328

Transmitting AM Signals with a USRP* Radio Implementing Non-Coherent AM Receivers with the RTL-SDR Implementing Coherent AM Receivers with the RTL-SDR Audio Multiplexing with the USRP* and RTL-SDR Hardware Alternative Hardware for Generating Desktop AM Signals Summary

Frequency Modulation (FM) Theory and Simulation

329

9.1 9.2 9.3 9.4 9.5 9.6 9.7 9.8 9.9 9.10

329 331 335 347 348 350 355 358 361 366

The History of the FM Standard The Mathematics of FM & the Modulation Index FM Signal Bandwidth FM Demodulation Using Differentiation Receiving and Downconverting FM Signals to Complex Baseband Non-Coherent FM Demod: Complex Differentiation Discriminator Non-Coherent FM Demod: The Complex Delay Line Discriminator Coherent FM Demodulation: The Phase Locked Loop Demodulating Signals from Commercial FM Radio Stations Summary

10 Desktop FM Transmission and Reception 10.1 10.2 10.3 10.4 10.5 10.6 10.7 10.8

Transmitting Mono WFM Signals with the USRP* Hardware Implementing Mono FM Receivers with RTL-SDR and Simulink Transmitting Stereo WFM Signals with the USRP* Hardware Implementing Stereo FM Receivers with RTL-SDR and Simulink Manipulating the MPX: Transmitting AM Signals with FM Transmitters. Manipulating the MPX: Audio Multiplexing with FM Transmitters Alternative Hardware for Generating Desktop FM Signals Summary

11 Digital Communications Theory and Simulation 11.1 Digital Modulation Schemes 11.2 Pulse Shaping 11.3 Digital Up and Downconversion 11.4 Carrier Synchronisation 11.5 Timing Errors and Symbol Recovery 11.6 Symbol Timing Synchronisation 11.7 Digital Receiver Design: Joint Carrier and Timing Synchronisation 11.8 Coarse Frequency Synchronisation 11.9 Phase Ambiguity 11.10 Differential Encoding and Decoding 11.11 Synchronisation with a Unique Word 11.12 Summary

367 368 376 390 396 409 415 423 425 427 427 437 442 448 458 464 477 480 488 489 499 502

v

Sofiware Defined Radio UsingMATLAB & Simulink and the RTL-SDR 12 Desktop Digital Communications: QPSK Transmission and Reception 12.1 Pulse Shaping with Real Time QPSK Transmitter and Receiver Designs.. 12.2 Coarse Frequency Synchronisation in a Real-time System 12.3 Carrier and Timing Synchronisation with the RTL-SDR 12.4 Developing a Simple Communications Protocol 12.5 ASCII Encoding and Decoding 12.6 Data and Frame Synchronisation 12.7 ASCII Message Transmission and Reception 12.8 Transmitting Images Across the Desktop 12.9 Transmitting Data Using FM Transmitters 12.10 Summary

503 504 512 516 523 525 528 544 551 556 566

Appendix A: Hardware Setup

569

A.l A.2 A.3

The RTL-SDR Hardware Support Package The USRP* Hardware Support Package RTL-SDR Frequency Error Correction

569 571 577

Appendix B: Common Equations

581

Appendix C: Digital Filtering and Multirate C.l Filter Classes and Characteristics C.2 Filter Specification and Design C.3 FIR Filter Processing Architecture C.4 Computation and Trade-offs C.5 Multirate Filtering: The Motivation C.6 Decimation C.7 Interpolation

583 583 584 586 586 587 588 590

Appendix D: PLL Design D.l Digital Type 2 PLL Linear Model and Z-Domain Transfer Function D.2 Analogue Type 2 PLL Linear Model and S-Domain Transfer Function... D.3 Extraction of Digital PLL Params Based on Analogue PLL Equivalence .. D.4 Phase Detector Gain D.5 Oscillator Gain

593 593 596 597 602 605

Appendix E: AM and FM Transmitters E.l Upconverting AM Radio Signals with the Ham It Up E.2 Building an 'RT4' 433.9MHz AM Transmitter E.3 Using the Raspberry Pi as an FM Transmitter

607 607 612 619

References

629

List of Acronyms

635

Index

641