Design For Tracking Loop Of Multi-mode Multi-frequency GNSS Receiver

With the development of modern science and technology, especially,the rapid development of communications, aerospace, and semiconductortechnology, global navigation satellite system (GNSS) has become themainstream system framework of positioning and navigation system. Atpresent, the system of satellite positioning and navigation that has beenput into operation in the world has GPS, GLONASS, GALLIEO and BD.Given the establishment of multiple navigation satellite constellationsystem, multi-mode multi-frequency GNSS receiver will greatly improvethe reliability, real-time performance and precision for the satellitenavigation and positioning. As for the design of the GNSS receiver,tracking module is always the key and core, and is also the technicaldifficulty. A thorough analysis and design is made for the tracking loop ofreceiver in this paper.Firstly, the basic composition and the positioning principle forGNSS system and the characteristic of the GNSS satellite signal wereintroduced in this paper. Then the processing to satellite signal wasdescribed which were capture and tracking, especially, for GPS. Besides,a comparison and analysis was made for the algorithm of tracking loop.Costas phase-locked loop and frequency locked loop of the carriertracking loop were detailed, and the phase difference and thecharacteristic of discriminator algorithms were analyzed. Then a twoquadrant arctangent algorithm was chosen as the discriminator algorithmof phase-locked loop and frequency locked loop with moderatecomputational complexity and good linear performance. No-coherentdelay lock loop was used to realize the pseudo-code tracking with thedetailed analysis of the features of pseudo-code tracking loopdiscriminator. Finally, comprehensive consideration the effect which wasthe vehicle dynamic performance of the receiver and noise interferencefor tracking signal, and combined the analysis of the characteristic of each order loop filters, the optimal loop bandwidth of receiver wascalculated by optimization design concept.Signal tracking for GPS was achieved according to the determinedtracking loop algorithm and the calculated optimal loop bandwidth. Theoutput of I and Q of current tracking loop and the integral results of threedifferent phases of advanced-code, intermediate-code and lag-code werecalculated according to the tracking results. At the same time, theperformance evaluation and testing were carried out for different loopfilter coefficient, damping coefficient and noise bandwidth. From the testresults, the performance of tracking loop is stable in this topic, and thevalidity of the design of the project is confirmed finally.