Code correlation technique provides all components of the satellite signal 1. Squaring Technique(p. 82) 1. Satellite clock reading Navigation messa In general, it is more difficult to resolve 3. Un-modulated carrier ies of the squared signals with hah Correlation technique is performed b A reference carrier is generated in receiver which is hen biphase modulated with a replica of the known Advantage and disadvantage RN code 2. The resulting reference signal is correlated with the Independent of PRN codes received satellite signal Satellite clock and the satellite orbit information are lost in the process. contains the navigation message which can be decoded and SNR is substantially reduced in the squaring process, eliminated by high-pass filtering. The final result is the Doppler shifted carrier on which a hase measurement can be Characteristics of The Four Techniques 1. All four approaches to recover the L2 carrier in the presence f A-S suffer from a substantial degradation in the SNR. 2. Cross Correlation Technique(p. 82) 2. Without no codeless or quasi-codeless techn ecovers gPs signal information as well as the code 3. Code Correlation plus Squaring correlation technique. Technique(p. 83) 3. Weaker signals are more sensitive to high ionospheric activities and interfering gamming)signals which may 4. Z-tracking technique (p. 83) The most recent quasi-codeless technique is: Z tracking SNR Degradation Compared to Code Correlation Technique The best performance in the presence of A-S) correlation tion plus squ Assignment 5 Summary 2. Describe the characters of C/A code P-code and Y-code? at is w-code, What is Y-code, What is relationship w-code What have we learnt? Which parts are important? 5. How to generate C/A-code? How to generation P-code? 8. How many parts does a receiver unit consists of? What is the 9. What is radio frequency(RF) section? Why does the multi channel has higher accuracy than single channel receive 10. Please describe in detail the GPS signal processing technique? 11. What is Squaring technique, Cross correlation technique, code 66 Correlation technique is performed by 1. A reference carrier is generated in receiver which is then biphase modulated with a replica of the known PRN code. 2. The resulting reference signal is correlated with the received satellite signal. Code correlation technique provides all components of the satellite signal 1. Satellite clock reading 2. Navigation message 3. Un-modulated carrier • After removal of the PRN code, the received signal still contains the navigation message which can be decoded and eliminated by high-pass filtering. • The final result is the Doppler shifted carrier on which a phase measurement can be performed. 1. Squaring Technique (p. 82) • Independent of PRN codes • Satellite clock and the satellite orbit information are lost in the process. • SNR is substantially reduced in the squaring process, In general, it is more difficult to resolve the ambiguities of the squared signals with halved wavelength. Advantage and Disadvantage 2. Cross Correlation Technique (p. 82) 3. Code Correlation plus Squaring Technique (p. 83) 4. Z-tracking technique (p. 83) The most recent quasi-codeless technique is: Z-trackingTM (The best performance in the presence of A-S). Characteristics of The Four Techniques SNR Degradation Compared to Code Correlation Technique Z-tracking -14 dB Code correlation plus squaring -17 dB Cross correlation -27 dB Squaring -30 dB 1. All four approaches to recover the L2 carrier in the presence of A-S suffer from a substantial degradation in the SNR. 2. Without exception, no codeless or quasi-codeless technique recovers GPS signal information as well as the code correlation technique. 3. Weaker signals are more sensitive to high ionospheric activities and interfering (jamming) signals which may even cause a loss of lock. Summary What have we learnt? Which parts are important? Assignment 5 1. How to generate GPS signal in orbit? 2. Describe the characters of C/A code, P-code and Y-code? 3. What is W-code, What is Y-code, What is relationship W-code and Y-code? 4. What is PRN? 5. How to generate C/A-code? How to generation P-code? 6. What is navigation message? Please explain in detail the characters of each subframe? 7. What is the signal processing principle? 8. How many parts does a receiver unit consists of ? What is the function of each part? 9. What is radio frequency (RF) section? Why does the multi channel has higher accuracy than single channel receiver? 10. Please describe in detail the GPS signal processing technique? 11. What is Squaring technique, Cross correlation technique, code correlation plus squaring technique and Z-tracking technique?