Design And Implementation Of A Fast Algorithm For GPS Navigation Space-time Joint Anti-interference

The satellites of GPS system are far away from the ground and the received power of GPS signal on the ground is very low.So the GPS receiver can be interfered by jammer easily.In this thesis,based on background of design a four-element anti-jamming GPS receiver,a fast implementation method of space-time adaptive anti-jamming algorithm is designed,and an IF space-time adaptive anti-jamming processor hardware is carried out.Firstly,the model of GPS satellite signal and interference is established according to the pattern four-element square antenna.A fast implementation method of space-time anti-jamming algorithm is designed based on the traditional power inversion algorithm without the direction of the satellite signal.The calculation load of fast algorithm is one-third of original algorithm.The performance of anti-jamming is analyzed.The influence of delay-tap number,snapshot number and direction of jamming on the performance of the algorithm is evaluated.Secondly,the hardware design and software implementation of algorithm of IF anti-jamming processor is accomplished.The schematic design,PCB design of IF anti-jamming processor are completed based on the architecture of FPGA and DSP.According to the procedure of the algorithm,the anti-jamming signal processing tasks are assigned on FPGA and DSP.The digital down conversion of four IF channels,the computation of covariance matrix and the processing of beamforming are implemented on FPGA.The calculation of weight based on fast power inversion algorithm is implemented on DSP.The reuse of calculation resource on FPGA chip is fulfilled by optimizing the design of FPGA software.The stability of software is improved through the timing optimization of FPGA program.The real-time performance of the weight calculation algorithm is realized by optimizing the assembly program on DSP.The updating time of weight is less than 0.85ms in case of four antennas and four delay taps.Thirdly,the performance of IF anti-jamming processor is evaluated on GPS IF interference simulator platform indoor.Then the effect of star searching for four-element anti-jamming GPS receiver is evaluated in the outdoor environment with interference.The anti-jamming performance of the processor is verified.