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Đề tài mô phỏng hệ thống thu phát tín hiệu GPS trên Matlab. Đề tài được thực hiện bằng công cụ mô phỏng Simulink. Đồ án được viết bằng tiếng anh hết sức chi tiết và dễ đọc. Mong sẽ giúp các bạn sinh viên, học viên cao học đang quan tâm về vấn đề này.
Global Positioning System Signal Simulation A Thesis presented for the Degree of Bachelor of Electrical Engineering (Honours) By Thiam Hock Tan Department of Information Technology and Electrical Engineering The University of Queensland Australia October 29, 2003 Candidate’s Declaration Candidate’s Declaration Head of School School of Engineering The University of Queensland St. Lucia, Queensland 4072 Dear Professor Simon Kaplan, In accordance with the requirements of the degree of Bachelor of Engineering (Honours) in the division of Electrical Engineering, I present the following thesis entitled “Global Positioning System Signal Simulation” This thesis was performed under the supervision of Professor Kurt Kubik and co- supervised by Dr Adam Postula. I certify that this thesis is my own and I acknowledged that it does not contain any material previously published for a degree at the University of Queensland or any other institution, except where acknowledged and referenced. Yours sincerely, Thiam Hock Tan i Acknowledgements Acknowledgements There are a number of people that I would like to give special thanks, who have contributed to the successful completion of this thesis. My apologies are extended to anyone whom I may have inadvertently missed. I would like to express my sincere appreciation to Professor Kurt Kubik and Dr Adam Postula for assisting and guiding me along this thesis. Without their help, this thesis will not reach the current stage and I greatly thank them for their precious time and efforts committed in the accomplishment of this thesis. I would like to thank Mr Bradley Houston for assisting me and helping me out regarding my doubts in MATLAB (Simulink) and help me clarify them. I also wish to thank my team mate, Mr Wai Cheng Yong who dedicated his time in the hardware so that I can concentrate in the software of this thesis to the completion of this thesis. Special thank is express to Mr Chin Chye Neo who stay up late with me in completing my thesis as we assist one another in our thesis, he is working on the “Ultra Wideband (Positioning)” thesis. He is a great motivator and has a strong sense of humour in times of difficulties to make us forget the present problems and work towards our final goal. Not forgetting to thank my dearest parents, Mdm Chee Kim Foo and Mr Eng Foo Tan who offer me the best education and taking so much pain and effort in guiding me till today. No words can represent my deepest gratitude for them. I just want to say, “It’s all within my heart”. ii Abstract Abstract Due to the modernization and advance technological advancement, days of using the street directory for navigation are soon going to be obsolete. Global Positioning System is the “Gateway to the Future”. This GPS Signal Simulator has the ability to simulate the current GPS L1 frequency at the user’s fingertips. Realistic generation of this L1 frequency allows the user to have a deeper understanding of what exactly the GPS signal is about and how it is coded and modulated. Coding of this signal is done by using the Coarse Acquisition (C/A) code. Data will spread across this C/A code before mapping onto the Binary Phase Shift Keying (BPSK) signal. This BPSK signal is modulated onto a carrier frequency to be transported along the communication channel. To be able to receive without any signal variations is almost impossible due to the extensive distance between the satellite and the receiver unit. Therefore, demonstration of signal variation can be done by using the Doppler shift in this simulation. Doppler Shift is the variation of frequency along the communication channel and it greatly depends on the location of the satellite. If the satellite is just above the user and at the closest position relative to the user, the Doppler frequency is zero. But other than this position, all other position involves Doppler shift and thus signal variation occurs. Other than Doppler shift, this simulation can observe the autocorrelation of any of the 32 satellite’s available in the GPS constellation right now. Delay of any amount of chips can be simulated to show the autocorrelation of the lag function. With this simulation, GPS L1 signal can be analyzed and observed to assist in any future GPS development. iii Contents Contents Candidate’s Declaration …………………… ………………………………………… i Acknowledgements ……………………………………………………………………… ii Abstract …………………………………………………………………………….…… iii List of Figures …………………………………………………………………… ……. ix List of Tables ………………………………………………………………………… xi Chapter 1 Introduction …………………………………………………………… 1 1.1 Overview of thesis …………………………………………………….… 2 1.2 Implementation ………………………………………………………… 2 1.3 Desired results ………………………………………………………… 3 1.4 Organization of Thesis ………………………………………………… 4 Chapter 2 Literature Review ……………………………………………………… 7 2.1 Global Positioning System ………………………………………………. 7 2.1.1 Control Segment ……………………………………………… 8 2.1.2 Space Segment ……………………………………………… 8 2.1.3 User Segment …………………………………………………. 9 2.2 GPS Signal Structure ……………………………………………………. 9 2.3 Determine User’s Location …………………………………………… 10 2.4 Pseudorange Measurement ………………………………………… … 11 2.5 Coarse Acquisition Code (C/A code) ………………………………… 12 2.6 Autocorrelation ……………………………………………………… 14 2.7 Doppler Shift ………………………………………………………… 16 2.8 Binary Phase Shift Keying (BPSK) ……………………………………. 20 2.9 Data Message Format ………………………………………………… 20 2.10 Summary of Chapter 2 ……………………………………………….… 21 iv Contents Chapter 3 GPS Signal Simulator in the Market …………………………………… 23 3.1 Accord GPS Correlator Simulator ………………………………… … 23 3.2 Welnavigate GS 600 …………………………………………………… 25 3.3 CAST 1000 Satellite Signal Simulator ………………………………… 27 3.4 Spirent Multi-Channel GPS/SBAS Simulation System STR4500 … … 28 3.5 Summary of Chapter 3 ……………………………………………….… 29 Chapter 4 Simulation of GPS L1 Signal Generator ……………………………… 31 4.1 Block Description …………………………………………………… 32 4.2 S-function ………………………………………………………………. 33 4.3 MATLAB function …………………………………………………… 34 4.3.1 MATLAB function (Right) …………………………………… 35 4.3.2 MATLAB function (Counter1023mega2) ……………………. 35 4.3.3 MATLAB function (Opmega) ……………………………… 35 4.4 Simulation of Part One ……………………………………………….… 36 4.4.1 Block 1 (Assign empty matrix) ……………………………… 37 4.4.2 Block 2 (50 bits data) …………………………………………. 37 4.4.3 Block 3 (Data input) …………………………………… …… 37 4.4.4 Block 4 (Sfunsv20460) …………………………………… … 37 4.4.5 Block 5 (Spreading block) ……………………………………. 38 4.4.6 Block 6 (SV 1 to 32) ………………………………………… 38 4.4.7 Block 7 (SV Selector) ………………………………………… 38 4.4.8 Block 8 (To file) …………………………………………….… 38 4.5 Interior of Part One Block 5 (Spreading Block) …………………… … 39 4.5.1 Block 1 (NA) ………………………………………………… 39 4.5.2 Block 2 (For Iterator) …………………………………………. 39 4.5.3 Block 3 (Goto i) ………………………………………………. 40 4.5.4 Block 4 (Port 1) …………………………………………… … 40 4.5.5 Block 5 (Port 2) ……………………………………………… 40 4.5.6 Block 6 (Selector) …………………………………………… 40 4.5.7 Block 7 (tmp_col) …………………………………………… 40 v Contents 4.5.8 Block 8 (Port 3) ……………………………………………… 40 4.5.9 Block 9 (num_B_eles) ……………………………………… 41 4.5.10 Block 10 (ones(size(u))) ……………………………………… 41 4.5.11 Block 11 (Mux) ……………………………………………… 41 4.5.12 Block 12 (double(u(1):u(2))) …………………………………. 41 4.5.13 Block 13 (Port 1) …………………………………………… 41 4.6 Interior of Part One Block 6 (SV 1 to 32) …………………………… 42 4.7 Simulation of Part Two ……………………………………………… 43 4.7.1 Block 1 (Input 1M C/A XOR Data) ………………………… 44 4.7.2 Block 2 (Fc = 10.23 MHz) ……………………………….…… 44 4.7.3 Block 3 (BPSK Modulation) ………………………………… 44 4.7.4 Block 4 (10 KHz Doppler Shift) …………………………… 44 4.7.5 Block 5 (Selector) …………………………………………… 44 4.8 Interior of Part Two Block 3 (BPSK Modulation) ………………… … 45 4.8.1 Block 1 (In 1) …………………………………………………. 45 4.8.2 Block 2 (Constant) ……………………………………………. 45 4.8.3 Block 3 (Switch) ……………………………………………… 45 4.8.4 Block 4 (Step) ……………………………………………… 46 4.8.5 Block 5 (Sum) ………………………………………………… 46 4.8.6 Block 6 (Inverse) …………………………………………… 46 4.8.7 Block 7 (In 2) ……………………………………………….… 46 4.8.8 Block 8 (Modulation) ……………………………………….… 46 4.8.9 Block 9 (Out 1) ……………………………………………… 46 4.9 Interior of Part Two Block 4 (10 KHz Doppler Shift) …………………. 47 4.9.1 Block 1 (In 1) ……………………………………………….… 47 4.9.2 Block 2 (Product) …………………………………………… 47 4.9.3 Block 3 (Relay) ……………………………………………… 47 4.9.4 Block 4 (Multi-port Switch) ………………………………… 48 4.9.5 Block 5 (In 2) …………………………………………………. 48 4.9.6 Block 6 (Product1) ……………………………………………. 48 4.9.7 Block 7 (Out 1) …………………………………………… … 48 vi Contents 4.10 Part One of Autocorrelation Simulation ……………………………… 48 4.10.1 Block 1 (SV Selector) ………………………………………… 49 4.10.2 Block 2 (SV 1 to 32) ………………………………………… 49 4.10.3 Block 3 (Autocorrelation) …………………………………… 49 4.10.4 Block 4 (Timing) …………………………………………… 49 4.10.5 Block 5 (Reshape) …………………………………………… 49 4.10.6 Block 6 (To Workspace) ……………………………………… 50 4.11 Interior of Part One Autocorrelation Block 2 (SV1 to 32) …………… 50 4.12 Part Two of Autocorrelation Simulation ……………………………… 51 4.12.1 Block 1 (From Workspace) ………………………………… 51 4.13 Summary of Chapter 4 …………………………………………………. 51 Chapter 5 User Manual ……………………………………………………………. 53 5.1 System Requirements ………………………………………………… 53 5.2 Getting the Files and Folders in the Right Location ………………… 54 5.3 Simulation Procedures for Part_1 ……………………………………… 55 5.4 Simulation Procedures for Part_2 ……………………………………… 56 5.5 Simulation Procedures for Autocorrelation_1 ……………………… 58 5.6 Simulation Procedures for Autocorrelation_2 ……………………….… 58 5.7 Summary of Chapter 5 …………………………………………………. 59 Chapter 6 Simulation Results and Analysis ………………………………………. 61 6.1 Data Stream of L1 Signal ……………………………………………… 61 6.2 Carrier Frequency of L1 Signal ……………………………………… 62 6.3 Converted Data Stream of L1 Signal ………………………………… 63 6.4 BPSK Data Stream of L1 Signal …………………………………… … 64 6.5 L1 Signal ……………………………………………………………… 65 6.6 Doppler Shift of L1 Signal …………………………………………… 66 6.7 Frequency Spectrum of Carrier ………………………………………… 67 6.8 Frequency Spectrum of L1 Signal …………………………………… 68 6.9 Autocorrelation Function of Space Vehicle ………………………….… 70 vii Contents 6.10 Problems Encountered and Rectification ………………………………. 71 6.11 Summary of Chapter 6 ……………………………………………….… 74 Chapter 7 Conclusion ………………………………………………………… … 75 7.1 Lessons learnt ………………………………………………………… 76 7.2 Further Development of this Simulator ……………………………… 76 Appendices …………………………………………………………………………… 77 Appendix A Sfun50 ………………………………………………………………… 77 Appendix B Sfunsv20460 …………………………………………………………… 78 Appendix C Sfunsv1000 …………………………………………………………… 80 Appendix D Right ………………………………………………………………….… 81 Appendix E Counter1023mega2 …………………………………………………… 82 Appendix F Opmega ………………………………………………………………… 89 Appendix G Sfunsv1 ………………………………………………………………… 90 Appendix H Sfunxcorr ……………………………………………………………… 92 Appendix I Sfuntime …………………………………………………………… … 94 References …………………………………………………………………………… 96 viii List of Figures List of Figures Figure 1.1: Picture of a satellite in space ………………………………………… … 2 Figure 2.1: GPS constellation ……………………………………………………… 7 Figure 2.2: GPS satellite signal …………………………………………………… 10 Figure 2.3: 4 satellites to get exact user’s location ……………………………….… 11 Figure 2.4: Pseudorange measurement ………………………………………… … 11 Figure 2.5: GPS C/A code generator ……………………………………………… 14 Figure 2.6: An Autocorrelation Function of SV 10 ………… …………………… 16 Figure 2.7: Doppler Principle ………………………………………………………. 17 Figure 2.8: Doppler Calculation ……………………………………………………. 18 Figure 4.1: S-function block …………………………………………………… … 33 Figure 4.2: MATLAB function block …………………………………………… 34 Figure 4.3: Block diagram of Part One …………………………………………… 36 Figure 4.4: Part One of Simulation ………………………………………………… 36 Figure 4.5: Spreading Block in Part One ………………………………………… 39 Figure 4.6: SV 1 to 32 Block in Part One ……………………………………… 42 Figure 4.7: Block diagram of Part Two …………………………………………… 43 Figure 4.8: Part Two of Simulation ……………………………………………… 43 Figure 4.9: BPSK Modulation Block in Part Two …………………………………. 45 Figure 4.10: 10 KHz Doppler Shift Block in Part Two …………………………… 47 Figure 4.11: Simulation of Autocorrelation Part One …………………………… … 48 Figure 4.12: SV 1 to 32 Block from Autocorrelation Part One ……………………… 50 Figure 4.13: Simulation of Autocorrelation Part Two ……………………………… 51 Figure 6.1: Data Stream from Part One of Simulation …………………………… 61 Figure 6.2: Carrier Frequency of 10.23 MHz ………………………………………. 62 Figure 6.3: Converted Data of Data Stream …………………………………… … 63 Figure 6.4: BPSK Data format of Data Stream …………………………………… 64 Figure 6.5: L1 signal of SV1 ……………………………………………………… 65 Figure 6.6: Doppler Shift of L1 Signal ………………………………………… … 66 ix [...]... simulations 21 Chapter 3 GPS Signal Simulator in the Market Chapter 3 GPS Signal Simulator in the Market GPS Signal Simulator is currently available in the commercial market But due to the specialization in this particular field, this type of simulator cost a huge amount of money and is used only by the company developing GPS receiver for simulating the signal characteristics of GPS to test if their receiver... characteristics of GPS In the following, a selected number of simulators are listed 3.1 Accord GPS Correlator Simulator This Simulator is a very powerful software package for understanding the characteristics of the GPS satellite signal and it’s processing in a typical GPS receiver It provides a sound platform to experiment with the various modules that constitute the signal processing section of a GPS receiver... The military uses the GPS in a wide range of scope, from navigation tools to target designation, air support to the integration of smart weapons [7] For the civilians, GPS are used in daily life applications, providing point-to-point navigation in public bus services, navigational usage by the hikers and mountaineers, and many more With the integration of the GPS in our life, the GPS will be a cornerstone... dramatic effects Therefore, GPS usage is very wide and depends on the individual user to use it appropriately Due to the technological advances and advancement of the human race, the need for accurate and immediate decision stimulated the boom of the GPS industries GPS receivers used to cost a “bomb” in the past, but due to great demand causing great supply, therefore current cheapest GPS receiver cost only... simulation of Global Positioning System (GPS) signal L1 using MATLAB software This software is particularly useful in technical computing and simulating program With the help of Simulink, which is a model based and system level design in real time simulation of the GPS signal can be carried out realistically The topics layout for each chapter is as follows In chapter 1, the GPS signal will be introduced and... and cost The main objective is to tap into the vast area of lucrative market of GPS In chapter 4, the simulation of the GPS signal generator will be discussed in details Due to the limitations of the software and the computer that the software is running on, certain constraints are present and made known Moving in depth into MATLAB (Simulink) block sets and how they are incorporated in this thesis simulation... cheapest GPS receiver cost only ten dollars Public transport nowadays uses GPS for navigation and receiving message from their control centre The GPS not only integrated into our lifestyle, but also has even become indispensable Faster pace of life requires quick responses and immediate reaction Consumers are the reason why the GPS is getting popular in our society 1 Chapter 1 Introduction Figure 1.1... G1 C/A SV(t) d(t) cos (Wc t) + G2 PSV(t) d(t) sin (Wc t) [8] The fundamental frequency (fo) is 10.23 MHz, L1 is 154 times fo and L2 is 120 times fo 9 2.2 GPS Signal Structure Figure 2.2 – GPS satellite signal [2] 2.3 Determine User’s Location The GPS uses 3 satellites to capture the user’s location and the fourth satellite to get the precise timing so that the distance of the user can be tracked and... by my partner, Yong Wai-Cheng [3] 1.3 Desired results The intended result is to build a GPS signal simulator But due to the limitation of equipments and human resource, the thesis scope change slightly to suit our present settings For software development, creation of the GPS L1 signal generator is required using MATLAB Simulink platform Whereas for the hardware development, designing and building the... the implementation of Global Positioning System (GPS) , users will be able to pin point the exact location that they are currently in The days of using the street directory or the map will soon be a matter of the past To non - military users, GPS appears to be a navigation tool for hiking and finding your current location Whereas for military users, GPS is very important as it plays a vital part in . ………………………………… 27 3.4 Spirent Multi-Channel GPS/ SBAS Simulation System STR4500 … … 28 3.5 Summary of Chapter 3 ……………………………………………….… 29 Chapter 4 Simulation of GPS L1 Signal Generator ………………………………. 54 5.3 Simulation Procedures for Part_1 ……………………………………… 55 5.4 Simulation Procedures for Part_2 ……………………………………… 56 5.5 Simulation Procedures for Autocorrelation_1 ……………………… 58 5.6 Simulation. show the autocorrelation of the lag function. With this simulation, GPS L1 signal can be analyzed and observed to assist in any future GPS development. iii Contents Contents Candidate’s