无源雷达系统中，为了快速重建目标回波，设计了基于变步长最小均方算法的自适应直达波干扰抑制系统，仿真表明，与定步长系统相比，该设计系统能以更快速度有效抑制直达波干扰。另外，为了解决直接计算互模糊函数运算量太大问题，引入了快速傅里叶变换计算方法，仿真表明运算量大大降低。最后，为了估计多普勒频移和时延参数，采用快速傅里叶变换方法计算互模糊函数最大值对应坐标，仿真表明两参数均估计正确。%An adaptive direct path wave interference suppression system based on variable step least mean square algorithm is designed to rebuild target echo signal in passive radar system. Simulation shows that,comparing with system based on con-stant step least mean square algorithm,the new system based on variable step least mean square algorithm can suppresses direct path wave interference effectively and rapidly. The fast Fourier transform is introduced into the system to reduce the calculated amount of cross ambiguity function. Simulation turns out that calculated amount has greatly been reduced. In order to estimate Doppler frequency shift and time delay patameters of echo signal correctly,the coordinates corresponding to maximum value of cross ambiguity function was calculated with fast Fourier transform. The simulation proved the correctness of the two estimated parameters.
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