Optimization of spatial filter for DPI and multipath interferences in passive radar

Spatial smoothing technique is an effective spatial filtering to eliminating the direct path interference(DPI) and multipath interferences in passive radar based on opportunity of illuminators, such as FM broadcast transmitter. The optimal weights are often acquired with respect to subarrays. This fact implies that there are extra adaptive degrees of freedom to be unused to improve the performance of spatial smoothing adaptive array. A novel spatial filter based on secondary optimization for spatial smoothing is proposed in the paper. We show how to optimize the adaptive array such that the pattern of array can minimize white noise power and match desired respond. Simulation results by applying real collected data show the proposed method is superior detect performance in comparison with conventional spatial smoothing.