Research On Interference And Multipath Suppression Technologies For High-Precision Measurement Of Satellite Navigation

With the continuous development of global satellite navigation systems,more and more navigation applications are increasingly demanding high-precision measurements.Especially the high-precision measurement problem in the interference scene has become a research hotspot.In addition,multipath error is one of the main error sources,which constrains the high precision application of satellite navigation.This paper focuses on the high-precision measurement problems in interference and multipath scenarios,researching the unbiased interference suppression,multipath suppression algorithm performance evaluation and multipath parameter estimation,interference and multipath joint suppression.The main works and innovations are as follows:(1)For the problem that frequency domain interference suppression(FDIS)algorithm causes the distortion of the auto-correlation function(ACF)of the navigation signal,the theoretical model of the distorted ACF under the non-ideal condition of the channel is established.Based on the comprehensive analysis of the influence of the FDIS algorithm in term of the pseudo-range measurement,this paper proposes an unbiased FDIS algorithm based on spectrum compensation,which uses the tracking loop estimation parameters to reconstruct the received signal and compensates for the signal energy loss caused by the FDIS algorithm.Through using the proposed method,the pseudo-range measurement bias introduced by the FDIS is effectively eliminated.The simulation results show that the pseudo-range measurement bias is reduced by 86%and 83% respectively under the condition of symmetric and asymmetric quadratic curve group delay.(2)For the problem of the insufficient algorithm performance evaluation for the Code Correlation Reference Waveform(CCRW)based multipath suppression technology,the CCRW multipath suppression performance evaluation model in complex scene is proposed.In witch the performance analysis models with the limited front end bandwidth,the non-ideal channel characteristics,and FDIS algorithm are established,respectively.Additionally,the multipath suppression and code tracking performance for a real receiver channel characteristics is analyzed under the conditions with and without interference.The results for different local reference waveforms and different code frequencies are given.The analysis results show that the multipath suppression and code tracking performance of the BPSK(10)signal is seriously degraded,and the W2 waveform with larger gate wave width should be selected in the receiver design,while BPSK(1)signal are less affected by the channel non-ideal.This conclusion has an important guiding value for the actual receiver design.(3)For the problem that the direction of arrival(DOA)and the code delay of the multipath cannot be estimated simultaneously using traditional multipath detection and parameter estimation methods.In this paper,an open-loop multipath parameter estimation method based on DOA estimation and beamforming is proposed.First,the DOA estimation method based on the L-type antenna array is used to realize the DOA fast estimation of the despread array signal,and the local code used for the despreading processing is a combination of codes with different delays relative to the direct signal.So that the DOA estimation of the multipath signals with different time delays can be achieved.Second,the parameters of the multipath signal are estimated using the array beamforming and open-loop method.Each multipath signal is separated and outputted using a beamformer constructed with the estimated DOA parameter,and the code delay is estimated using the open-loop method.From the simulation results,for multipath signals with actual carrier-to-noise ratio greater than 30 d BHz,the delay estimation error,carrier-to-noise ratio estimation error,and DOA estimation error are less than0.0094 chips,1 d B,and 1.93 degrees,respectively.(4)For the problem that both the space-time filter and multipath signal causes the pseudo-range measurement error,an array antenna based interference and multipath joint suppression algorithm is proposed.The despreading process is performed after the interference suppression process using subspace projection method.The DOA parameters of the direct signal and the multipath signals are estimated by the sparse recovery method.Using the estimated DOA parameters,the unbiased beamformer is constructed,which can eliminate the pseudo-range measurement bias introduced by the space-time filter and multipath error.To reduce the computational complexity,the algorithm can be simplified into a blind beamforming algorithm based on direct signal DOA estimation,in which only the DOA of the direct signal is needed to estimate.For the incident direction of the direct signal changes slowly,the two-dimensional DOA search range can be reduced significantly.The unbiased beamformer using the direct signal DOA parameter can eliminate the pseudo-range bias introduced by space-time filter and reduce the multipath error by increasing the signal energy of the direct signal.The simulation results show that the pseudo-range error is reduced from-31.9m using the traditional blind beamforming algorithm to-1.4m using the proposed method.For the high-precision measurement requirements of GNSS application in complex scenarios,the key technologies of unbiased interference suppression and multipath suppression are studied.The research results can be used for improving the service accuracy of Bei Dou system under interference and multipath scenarios.