Research On The GPS Anti-jamming Based On Variable Step LMS Algorithm

GPS is currently the most widely used navigation and positioning system,but because of its small signal power and complex working environment,it is highly susceptible to interference from interfering signals,resulting in its loss of navigation and positioning.In addition,the Beidou satellite navigation system independently developed by China is also facing similar problems,so it is very meaningful to study the GPS anti-jamming problem.The working principle,signal characteristics,interference form and common anti-jamming technology of GPS are briefly introduced.The basic principle of adaptive nulling antenna is analyzed.The common adaptive algorithms are introduced.The simulation results are given.The advantages and disadvantages of linear constrained minimum variance?LCMV?algorithm,recursive least square?RLS?algorithm and least mean square?LMS?algorithm are given,and LMS is selected as the research object.Aiming at the contradiction of the traditional fixed-step LMS between the convergence speed and the steady-state mean square error,an improved variable-step LMS algorithm based on hyperbolic sine function is proposed and analyzed by studying the common variable-step LMS algorithm.The step size is adjusted by the correlation valuee_?n?e_?n-1?of the error,so that the step size is only related to the useful signal,and is independent of the noise signal,so it can reduce the noise sensitivity and improve the convergence speed as well as anti-jamming performance.The parameters,the number of interference sources,the number of array elements,the jammer-to-noise ratio,and the impact of the array on the performance of the algorithm.Finally,the improved variable step size LMS algorithm is compared with the common variable step size LMS algorithm and the LCMV algorithm.The experimental results show that the larger the jamming-to-noise ratio is,the stronger the anti-interference ability of the algorithm is;the anti-jamming performance of the Y array is the best,the square array is second,and the uniform linear array is slightly worse;the anti-jamming ability,convergence speed,steady state,the square error and other indicators of SinhLMS are better than SVSLMS,ArctanLMS,FLMS and LCMV algorithms,so the improved variable step size LMS algorithm based on hyperbolic sine function is better.