等效凹槽滤波器及其在无源相关定位雷达中的应用(英文)

归一化最小均方误差(NLMS)算法被广泛应用于无源相干定位(PCL)雷达系统的直达波和多径干扰对消。该文提出NLMS干扰对消器与雷达模糊函数结合可以等效为凹槽滤波器，该滤波器在雷达模糊函数平面中的零多普勒处产生一个凹槽。分析显示凹槽的宽度和深度与NLMS算法的步长密切相关。文章分析了凹槽对PCL雷达目标检测的影响，结果显示宽的凹槽会使PCL雷达系统的目标检测性能恶化。文章进一步提出了非均匀归一化最小均方误差(Non-uniform NLMS, NNLMS)算法，该算法能有效抑制具有多普勒频率的杂波，并且能有效降低雷达模糊函数的底噪。该算法引进了步长矩阵，利用该矩阵可以实现在不同的距离单元产生不同宽度的凹槽，每个距离门的凹槽宽度取决于杂波干扰的能量和多普勒频率。与传统NLMS相比，NNLMS算法可以实现更快的收敛速度，试验结果验证了该算法的有效性及优越性。 

Notch Filter Analysis and Its Application in Passive Coherent Location Radar (in English)

The Normalized Least-Mean-Squares (NLMS) algorithm is widely used to cancel the direct and multiple path interferences in Passive Coherent Location (PCL) radar systems. This study proposes that the interference cancelation using the NLMS algorithm and the calculation of the radar Cross Ambiguity Function (CAF) can be modeled as a notch filter, with the notch located at zero Doppler frequency in the surface of the radar CAF. The analysis shows that the notchs width and depth are closely related to the step size of the NLMS algorithm. Subsequently, the effect of the notch in PCL radar target detection is analyzed. The results suggest that the detection performance of the PCL radar deteriorates because of the wide notch. Furthermore, the Nonuniform NLMS (NNLMS) algorithm is proposed for removing the clutter with the Doppler frequency by using notch filtering. A step-size matrix is adopted to mitigate the low Doppler frequency clutter and lower the floor of the radar CAF. With the step-size matrix, can be obtained notches of different depths and widths in different range units of the CAF, which can filter the low Doppler frequency clutter. In addition, the convergence rate of the NNLMS algorithm is better than that of the traditional NLMS algorithm. The validity of the NNLMS algorithm is verified by experimental results.