Design And Implementation Of GPS Anti-jamming Algorithm Based On Array Antenna

Since the GPS satellite navigation system appeard, it has been widely expanded from the military field to the commercial field all over the world, which produced a huge social value.In the military field, the GPS has become an important navigation equipment in the platform of the air, land and sea, which provides the precise position and attitude information. In the civil field, the vehicles and smart phones equipped with GPS bring about the huge market demands, and further promote the development of the GPS. However, the GPS signal is weak,which has a poor anti-interference ability. Therefore how to restrict the interference has become an challenge issue. In order to solve above problem and to improve the position accuracy, this paper made an in-depth study of the adaptive filter algorithm.By introducing the GPS system, positioning principle and signal structure, this paper listed several common types of interference and discussed the basic theory of adaptive antenna in detail. This paper studied the effect of the array element number, array element spacing and array structure towards the antenna pattern both in theory and simulation analysis.Then, the space-time filtering technology which belongs to the adaptive filtering was introduced and the input signal was given to model in mathematical methods. Considered the characteristics of the GPS signal, several kinds of optimal space-time filtering beamforming principle with its application and the known conditions required was analyzed in comparison.Thus, choosing the linear constrained minimum variance criterion as the beamforming principle and the power inversion algorithm as the GPS anti-jamming algorithm. In the algorithm implementation, in order to resolve the conflict between the convergence speed and the steady-state error, a new algorithm of the variable step size was proposed to solve the above problems by constructing the function model of step factor.With the comparison of the algorithms and filtering techniques, the simulation environment was given. First, the influence of the selection of key parameters in the new algorithm to the performance of the filter was deeply discussed, and we compared the convergence performance between the proposed algorithm and the traditional one. The simulation results showed the superiority both in convergence and steady-state error. Second,through the simulation of the space-time filtering performance based on the power inversion algorithm, the results verified the performance advantage such as the increased degree of freedom by the space-time filtering algorithm in the way of increasing the tap coefficient with the cost saving and limited volume, the ability to filter the interference signal came from the same direction of the desired signal, the suppression to the wideband interference signal.Finally, the half-hardware simulation platform of FPGA was set up. With the application of the Matlab, we generated GPS signal and achieved the algorithm implementation for FPGA.The simulation results showed a fast converge of the weight vectors of the power inversion algorithm, which verified the feasibility of the algorithm.