Research On Time Domain Suppression Algorithm For GNSS Multipath Interference

Multipath interference has become a major issue affecting the application of Global Navigation Satellite System(GNSS)in complex environments.Multipath interference refers to the interference signal formed by satellite signals passing through the refraction of objects around the receiver antenna and reaching the receiver.It is one of the common error sources in satellite positioning systems.Research has shown that multipath interference can lead to pseudo range errors in satellite positioning systems,which can reach the level of meters or hundreds of meters,and have a serious impact on the positioning accuracy and reliability of GNSS.This impact will vary with observation time and environmental changes.Therefore,multipath interference suppression technology has become a bottleneck issue in improving the measurement accuracy of GNSS.The paper takes the Global Positioning System(GPS)as an example to study the principles of multipath interference,mathematical models of multipath signals,the impact of multipath interference on receivers,and suppression methods.The main work is as follows:Firstly,the sources and characteristics of multipath interference in GPS measurement error sources were analyzed.Based on the relationship between multipath signals and direct signals,a mathematical model of multipath signals was established.The mathematical model of multipath signals was verified through simulation.Secondly,the basic working principles of the pseudo code tracking loop and carrier tracking loop in GPS receivers were analyzed,and the mathematical model of multipath signals was used to simulate and analyze their impact on the pseudo code tracking loop and carrier tracking loop in GPS receivers.Once again,simulation and comparative analysis were conducted on the narrow correlation technology of time-domain multipath suppression algorithms,Multipath Estimating Delay Lock Loop(MEDLL)technology,and multipath suppression technology based on Weighted Fourier Transform and RELAXation(WRELAX)parameter estimation.And on the basis of traditional MEDLL technology,we have studied improved MEDLL technology based on residual estimation,improved MEDLL technology based on Kalman filtering,and improved MEDLL technology based on wavelet filtering and Kalman filtering.Finally,the estimation performance of the above algorithms in low signal-to-noise ratio environments was simulated and analyzed using the MATLAB simulation platform.The simulation results show that although the improved MEDLL technology based on residual estimation can estimate the number of multipath signals,it cannot eliminate the impact of noise;The improved MEDLL technology based on Kalman filtering can filter out most of the noise components in the signal and reduce the impact of noise on MEDLL’s estimation of multipath errors,but residual noise still has a certain impact;The improved MEDLL technology based on wavelet filtering and Kalman filtering has better noise suppression effect,which can accurately estimate the parameters of multipath signals,greatly eliminating the impact of noise,and effectively improving the suppression ability of multipath signals in low signal-to-noise ratio environments.