Research On Space Time Anti-jamming Algorithm Of Satellite Navigation Terminal

The space time adaptive processor combines the advantages of spatial filter and time-domain filter,and it can improve the anti-jamming performance of the system.However,when the interference direction falls in the main lobe,the main beam deviation will affect the reception of the desired signal,when the interference direction falls in the side lobe,the high side lobe level will not be able to suppress the interference.Moreover,the stability of beamformer will be affected by the mismatch of snapshots and steering vector.Therefore,it is very important to study the main lobe interference suppression algorithm and the robust low side lobe algorithm.The main work of this paper is as follows:Firstly,the Beidou satellite B3 frequency signal is modeled and simulated,and the types of interference,array model and space time adaptive processor are introduced.On this basis,the space time least mean square algorithm,recursive least squares algorithm,interference subspace projection algorithm and linear constraint minimum variance algorithm are simulated and analyzed.The results show that the linear constrained minimum variance algorithm can improve the output signal-to-interference plus noise ratio under narrowband interference and wideband noise interference,and has good performance in both high and low signal-to-noise ratio.However,the algorithm cannot solve the main lobe interference and mismatch of steering vector.Secondly,in order to solve the problem of main lobe interference,the blocking matrix processing,the eigen projection processing,the oblique projection processing and the constrained signal-to-noise ratio algorithm based on diagonal loading are studied and simulated.The results show that the four algorithms have the problems of main beam shift and side lobe level elevation.Aiming at the problem of wave peak migration,whitening method and multi-directional constraint method are used to solve the problem.In order to solve the problem of side lobe level rising,a singular value decomposition algorithm is proposed.On the basis of this,a focusing matrix is constructed,which can focus the frequency band of wideband interference on a reference frequency and turn it into a narrowband main lobe interference.The simulation results show that the two algorithms can converge under the low snapshots,moreover,they have large signal-to-interference plus noiseratio improvement and good beam pattern.Finally,in order to solve the problem of side lobe interference,the effects of snapshot and steering vector mismatch are described,and then the uncertainty set model of steering vector is described.In order to reduce sidelobe level,the fourth order cumulant algorithm based on linear constraint minimum variance and the improved fourth order cumulant algorithm are studied.The simulation results show that the beam sidelobe level is reduced,and the improved algorithm also has a good beam map under the condition of low snapshots,but the computational complexity is increased.It is not good for practical application.Therefore,a constrained inverse beamforming algorithm is proposed,and then introducing the steering vector uncertainty set model into the algorithm to improve its stability.From four aspects: beam diagram,snapshots,signal direction error and running time,the simulation results show that the robust constrained inverse beamforming algorithm has better performance.