Multipath Mitigation Loop Tracking Technique For New Navigation Signals

To achieve spectrum sharing and improve the system’s performance, many countrieshave proposed modernization program of satellite navigation systems. In thismodernization program, many countries use a new signal modulation-----BOC modulation.Therefore, they produce the BOC signal and various signals of its new variant. Althoughthe new signal system brings in a series of performance improvements, it puts forwardhigher requirements for the performance of anti-multipath algorithms. The purpose of thispaper is to design and implement the multipath algorithm tracking loop for new satellitenavigation signal system which means the paper is about to come up with a anti-multipathsignal algorithm which is suitable for new signal system.Firstly, this paper introduces the modulation of new signal system which includes thesignal generation, autocorrelation function and power spectral density. It also describesseveral signal tracking algorithms for BOC modulation signal. Then, it introduces thecharacteristics of multipath phenomena. By analyzing through the multipath model, itconfirms the impact of multipath interference on delay locked loop and carrier trackingloop.The paper focuses on the principles and the anti-multipath performances of threeanti-multipath technologies which are based on code tracking loop (narrow-related,Double-Delta and MEDLL). We implement the simulations of those three algorithms on theMATLAB. Through the analyses and researches on multipath error envelope of thealgorithms, we conclude that the more correlators we have in code tracking loop, the moreaccurate estimation we can achieve for time delay. However, the increasing number ofcorrelators can affect the speed of processing, so we need to compromise between cost andaccuracy. Also, it shows that MEDLL algorithm has a better anti-multipath performancethan the other two algorithms which can basically eliminate the code tracking error causedby multipath.The final part of this paper describes the MEDLL algorithm flowchart. It alsointroduces the process of estimation of the multipath parameters (phase estimation, delay estimation, magnitude estimation) and the steps of loop iteration. The diagram of MEDLLalgorithm software implementation for new signal system is given in the end.