A SPREAD SPECTRUM RANGING SYSTEM - ANALYSE AND SIMULATION A THESIS SUBMITTEDTO THE FACULTYOF GRADUATESTUDIES AND RESEARCH IN PARTIALFULFILLMENT OF THE REQUIREMENTS FOR THE DEGREEOF MASTEROF SCIENCE 1N ELECTRONICSYSTEMS ENGU BY Yong Luo Regina, Saskatchewan March 15, 1998 @ Copyright 1998 : Yong Lu0 395 Wellington Street 395. nie Wellington Ottawa ON KIA ON4 Ottawa ON K1A ON4 Canada Canada The author has gmuted a non- L'auteur a accordé une licence non exclusive licence allowing the exclusive permettant à la National Library of Canada to Bibliothèque nationale du Canada de reproduce, loan, distribute or sell reproduire, prêter, distribuer ou copies of this thesis in microform, vendre des copies de cette thèse sous paper or electronic formats. la forme de microfiche/nIm, de reproduction sur papier ou sur format électronique. The author retains ownership of the L'auteur conserve la propriété du copyright in this thesis. Neither the droit d'auteur qui protége cette thèse. thesis nor substantial extracts fiom it Ni la thése ni des extraits substantiels may be printed or otherwise de celle-ci ne doivent être imprimés reproduced without the author's ou autrement reproduits sans son permission. autorisation. Abstract A hybrid Direct Sequence Spread Spectrum ranging technique is analyzed and simulated in this research work. The DS/SS-CW ranging technique can be consid- ered as the combination of direct sequence spread spectrum ranging technique with the Continuous Wave (CW) ranging technique. The thesis illustrates the operation principle of the DS/SS-CW ranging. A theoretical analysis of the system perfor- mance is developed in terms of range detection, Signal-to-Noise Ratio (SNR) and the attenuation of multipath signals. The analysis reveals that the DS/SS-CW tech- nique has the same benefits in jamrning and multipath rejection as a spread spectrum systern, and the carrier phase can still be employed to obtain more accurate range information. Cornputer simulations are conducted to investigate the effects of noise, multipath signals as well as the system bandwidth. The research work suggests that the DSISS-CW technique is of pract ical value in high precision ranging applications. Acknowledgments I would like to express my sincere gratitude to Prof. R. Palmer, my thesis super- visor. His unlimited guidance, keen supervision, and invaluable criticism made the achievements in this work possible. The initial idea in this work originated frorn Prof. R. Palmer. My special thanks to him for introducing me to the treasure-house of the today's navigation technology. The Faculty of Graduate Studies and Research, and the Faculty of Engineering provided financial assistance during my period of study, which is much appreciated. Finally, 1 am indebted to my wife and my son whose love and understanding were essential in the completion of this work. Contents Abstract Acknowledgments .. Table of Contents 111 List of Figures vi Chapter 1 Introduction 1 1.1 Distance Ranging Techniques . 2 1.2 Principle of RF Ranging Techniques . 4 1.3 Propagation Path Effects . 7 1.4 Spread Spectrum System . 12 1.5 RF Distance Ranging in Existing Navigation Systems . 13 1.5.1 LORAN-C . 13 1.5.2 OMEGA . 15 1.5.3 NAVSTAR GPS . 16 1.6 Overview of the thesis . 17 Chapter 2 RF Range Measurement Techniques 18 2.1 CW Ranging Technique . 1s 2.2 DS/SS Ranging Technique ........................ 3 9 2.3 Tom Ranging ............................... 23 2.4 Hybrid spread spectrum ranging system ................ 27 Chapter 3 System Performance Analyses 30 3.1 System mode1 ............................... 30 3.2 Direct Path Signal Analysis ....................... 35 3.3 Range Detection ............................. 38 3.4 Signal-to-Noise Ratio ........................... 40 3.5 Multipath Rejection ........................... 43 3.6 Process Gain ............................... 46 3.7 A Hybrid DS/SS-CW System Design Example ............. 47 3.7.1 Carrier frequency consideration ................. 47 3.7.2 PN signal chip rate consideration ................ 49 3.7.3 Measurement time consideration ................. 51 3.7.4 The basic performance equation ................. 52 3.7.5 Calculation of multipath effects ................. 53 3.8 ChapterSummary ............................ 55 Chapter 4 System Simulation 58 4.1 System Mode1 for simulation ....................... 58 4.1.1 Sampling Frequency ....................... 60 4.12 System parameters ........................ 61 4.1.3 Design of FIR filters ....................... 62 4.1.4 Generation of Noise ........................ 63 4.1.5 Pseudo-Random Binary Sequence ................ 65 4.1.6 Multipatli channel mode1 ..................... 4.2 Simulation Studies of the System .................... 4.2.1 Range Detection ......................... 4.2.2 Impact of Noise .......................... 4.2.3 Effects of Multipath ....................... 4.3 Effects of the system bandwidth ..................... 4.4 Chapter summary ............................. Chapter 5 Conclusions Bibliography Appendix A Properties of PN Sequences A.l Periodic PN Sequences .......................... A.2 Partial Correlation ............................ A.3 PN Signals and the Properties ...................... A.4 Partial Correlation of PN Signals .................... List of Figures Two-way Distance Ranging ....................... Differential Distance Ranging ...................... Intersecting Hyperbolic Systems ..................... One-way Distance Ranging ........................ Propagation paths over the earth surface ................ Effect of ground-reflected signal ..................... LORAN station arrangement patterns ................. CW system ................................ Two-path mode1 receiving signal ..................... DS/SS system ............................... DS/SS Correlation; N .Length of PN sequence, ti .Chip duration . Tone-ranging technique .......................... Hybrid Spread Spectrum Ranging System ............... System Block Diagram .......................... Receiver Model .............................. Correlator output function ........................ Multipath signal with T < Tc ....................... Effects of multipath signal when T < Tc ................. System Simulation Model ........................ 4.2 Simulation mode1 for white noise (a) Noise PSD (b) Simulation PSD . 64 4.3 Linear feedback shift register arrangement ............... 66 4.4 Range detection (1) ............................ 70 4.5 Range detection (II) ........................... 71 4.6 Noise Output (1) Measurement Time Effects .............. 74 4.7 Noise Output (II) System bandwidth effects .............. 76 4.8 Signal-to-Noise Ratio Results (1) .................... 77 4.9 Signal-teNoise Ratio Results (2) .................... 78 4.10 Signal-to-Noise Ratio Results (3) .................... 78 4.11 Signal-to-Noise Ratio Results (4) .................... 79 4.12 Correlator Outputs Under Noise (1) ................... 80 4.13 Correlator Outputs Under Noise (2) ................... 81 4.14 Correlator Outputs Under Noise (3) ................... 81 4.15 Correlator Outputs Under Noise (4) ................... 82 4.16 Multipath signal output (1) ....................... 84 4.17 Multipath signal attenuation ....................... 85 4.18 Correlator receiver output ........................ 86 4.1 9 Phase measurernent error for 1 r 1 = O .1 ................. 88 4.20 Phase measurement error for Ir1 = 0.5 ................. 89 4-21 Phase measurernent error for 1 rl = 0.9 ................. 90 4.22 Phase measurement error for 1 rl = 1.2 ................. 91 4.23 Effects of the system bandwidth (a) ................... 92 4.24 Effects of the system bandwidth (b) ................... 93 4.25 Relative half-height width ........................ 94 A.l One period of PN signal for N = 7 ................... 109 vii A.2 (a) The basic chip correlation (b) The chip function correlation . 111 A.3 Mean and variance of partial correlation . 112 Chapter 1 Introduction Navigation can be defined as the process of directing the movement of a vehicle from one position to another. Navigation of any kind generally provides answers to three questions [l]: Where am I? How do 1 get to where 1 want to go? When will 1 arrive? The subject of navigation has a romantic and scientific background alrnost as old as civilization itself, and the subject has been one of the major concerns and interests throughout the recorded history. It has received the attention from the greatest scientists as well as monarchs. Modern navigation is a curious mixture of ancient and modern techniques. The magnetic compass, still in widespread use, is nearly a thousand years old, and the modern equivalent is used throughout the world. By contrast, inertial technology, the basis for some of today's most effective navigation systems, is only decades old, as is computer and satellite technology. Navigation has been progressing for 700 to 800 years, and is not "mature" in any sense [l]. The first 90 percent of this long history was concerned principally with navigation at sea. Since the first flight of the Wright brothers, the demands of aerial navigation have resul ted in an acceleration of development in navigation. Today, navigation technology has penetrated almost every civil and mili tary application, such as space navigation, land vehicle navigation, aircraft navigation , trafic control and marine navigation. The real milestone of today's art and science of navigation is the NAVSTAR Global Positioning System (GPS). Since