Research On Bias Analysis And Unbiased Algorithm In Satellite Navigation Antenna Array Anti-jamming Processing

Global Navigation Satellite Systems(GNSS)are often influenced by interference signals in practice,especially in military applications.Military satellite navigation receivers are often in the harsh electromagnetic environment.In order to improve the anti-jamming performance of the receivers,the antenna array anti-jamming technology is often used.The antenna array can significantly improve the receivers' anti-jamming performance,but it may lead to the distortion of GNSS signal at the same time,resulting in code phase and carrier phase measurement bias.Finally,positioning accuracy will be reduced.How to use the array antenna receivers to realize the high precision positioning and navigation has become a research hotspot.In this context,this paper has mainly done the following the works:(1)For the mechanism of GNSS signal distortion caused by antenna array anti-jamming processing is unclear,this paper theoretically analyzes the mechanism of code phase and carrier measurement bias of GNSS signal under different weighting criterions.The theoretical models of code phase and carrier phase under different weighting criterions are built,and the effectiveness of theoretical models is verified by software simulation.The theoretically analysis shows that: space-only MVDR criterion introduces no measurement bias.Space-only PI criterion dose not introduce code phase bias,but it will introduce carrier phase measurement bias which is influenced by spatial correlation coefficient.Both space-time MVDR and space-time PI criterion introduce code phase and carrier phase measurement bias which are influenced by spatial correlation coefficient,interference signal and number of taps.The measurement bias can reach several meters,which cannot meet the demand for high-accuracy GNSS applications.The results of this part lay the theoretical foundation for the unbiased weighting algorithm.(2)Considering that the channel mismatch of antenna array is inevitable in practice,the actual performance of different channels of antenna array is tested by using the hardware platform.It is used to build the theoretical model of the channel mismatch.The code phase and carrier phase measurement bias of GNSS signal caused by amplitude-frequency characteristic mismatch,mean group delay mismatch and group delay jitter mismatch and the anti-jamming performance are analyzed under different weighting criterions.The results show that: taking the existing antenna array channel parameters as reference,channel amplitude-frequency mismatch does not increase the measurement bias of different anti-jamming criterions,but it can decrease the anti-jamming performance of antenna array,especially for space-only anti-jamming criterions under which the anti-jamming performance can decrease 30 dB.Channel mean group delay mismatch can obviously increase the measurement bias of space-only criterions,but will not increase the measurement bias of space-time criterions.Moreover,it does not significantly influence the anti-jamming performance of antenna array.Channel group delay jitter mismatch will significantly increase the measurement bias of different anti-jamming criterions and the measurement bias under the simulation condition can be more than 10 meters.What's more,channel group delay jitter mismatch also decrease the anti-jamming performance of antenna array significantly and the maximum of the anti-jamming performance can reach 60 dB.(3)In order to solve the shortcomings of the existing unbiased weighting algorithms,including a large amount of computation and anti-jamming performance decreasing,a novel unbiased space-time weighting algorithm based on the MVDR algorithm is proposed.This algorithm can guarantee the linear phase of the space-time filter,and does not introduce code phase and carrier phase bias.In addition,the proposed space-time adaptive processor consumes only one degree of freedom to guarantee phase linearity,so it could avoid loss of anti-jamming performance.Theoretical analysis and simulation results show the effectiveness of the proposed algorithm.In the end,the main research work of the paper is summarized,and the work to be carried out in the next step is forecasted.