Research On The Theory And Key Realization Technologies Of Space-Time Interference Suppression For GPS Receiver

Space-time interference suppression technology shows great predominance compared with only time, frequency or space field techniques for GPS receiver. Many kinds of interferences can be counteracted by space-time adaptive processing (STAP) technology. It can increase the degrees of freedom so remarkably that the anti-jamming capability can be enhanced essentially without increasing the number of antennas. This dissertation researched the theory and key realization technologies of space-time interference suppression for GPS receiver.Firstly, the dissertation discussed the theoretical foundation of space-time anti-jamming adaptive filtering for GPS receiver. The corresponding mathematical model was proposed; The optimal criterion of STAP was analyzed; The optimal weight expression in different constraints of LCMV criterion was deduced; The space-frequency response of STAP weight was simulated in different jammers (wideband, partialband and narrowband jammers) circumstances, the relationship was summarized between the jammer and degrees of space-frequency freedom and some available conclusions of space-time anti-jamming processing were drawed; The distortion of GPS signals induced by STAP was discussed. Through theoretical analysis and simulation experiments, it was pointed out that STAP could apply to GPS anti-jamming reliably in appropriate optimal criterions and constraints, and would not result in serious signal distortion. The discussion above has some referential value for the anti-jamming theory research and design of GPS space-time receiver.Along with the anti-jamming capability improvement through STAP, the computational complexity increases greatly. The reduced-rank simplification method aim at computation reduction is one of the key techniques for STAP. Two typical multistage iterative reduced-rank (MIRR) methods, multistage nested wiener filtering (MWF) algorithm and auxiliary vector filtering (AVF) algorithm were deeply analyzed and unified to the same reduced-rank frame on a certain enhanced condition. A simplified MIRR algorithm was deduced and analyzed to be used in space-time interference suppression for GPS receiver, which has low computational complexity and good performance. The algorithm has a parallel structure, processes receive signal in a data domain and suits hardware realization. For space-time spoofing interference suppression, a new approach combing PD (partial despreading) with MIRR was proposed, which overcomes the disadvantages like very long weight vector, large computation, slow convergence and Doppler shift influence.A new kind of approach was proposed for interference suppression of GPS receiver. It combines subspace projection with STAP based on the characteristics of GPS signals, noise and jammers. The optimal filter weight was deduced using subspace projection form. It was proposed that space-time interference subspace is constructed simply and effectively using the multistage decomposition character of the MWF based on the correlation subtractive architecture. Considering the strong interference in GPS receiver, an improved adaptive PASTd subspace tracking technique is proposed. It adds the steps of eigenvector orthogonalization and eigenvalue diagonal loading. The interference subspace is estimated more precisely and quickly. For LFM nonstationary interferences, it was proposed to detecte interferences and estimate parameters using STFT-Hough transformation, reconstructed interference instantaneous frequencies precisely. Combining the space characteristic, Space-time interference subspace is constructed. The numerical simulation results demonstrated that these algorithms proposed can construct space-time interference subspace simply and effectively. Interference suppression is achieved through projecting the received signal to the orthogonal subspace of space-time interference subspace.The quantization problem was deeply analyzed for designing a GPS space-time receiver. The loss of the receiver output SNR is researched for different length of AD quantization without interference. It was pointed out that the performance analysis of AD quantization with strong interferences can change to the quantization analysis without interferences on a certain condition. It was established a simple linearly equivalent model for analyzing the influence of the finite word length operation in IF-digitalized processor.A design scheme of space-time anti-jamming module was proposed for GPS receiver. The system construction was discussed. The structure and design target about the four submodules was given including antenna array submodule, RF submodule, IF anti-jamming submodule and DSP control submodule. The FPGA realization of IF anti-jamming submodule is analyzed emphatically.