Strong Echo Cancellation Based on Adaptive Block Notch Filter in Passive Radar

In passive radar, the waveform is not controlled by the system, so strong echoes usually produce high sidelobes in the correlation function. Since the sidelobes can mask the weak targets, strong echo cancellation methods are required. The generalized adaptive notch filter (GANF) is an efficient method compared with the extensive cancellation algorithm. However, the GANF estimates different frequencies separately (in parallel or series), and a point-by-point iterative operation is adopted, which leads to heavy computational burden. This letter presents a multifrequency estimation notch filter which is a simplified GANF based on the signal model. Furthermore, an adaptive block notch filter is proposed to reduce the processing time. The efficiency of the block notch filter is verified by simulations.