An adaptive algorithm of direct path interference suppression for active sonar detection

In order to eliminate direct path interference(DPI)between active sonars in navy battle form- ation and to detect weak echoes from underwater targets, an adaptive algorithm based on frequency-domain adaptive filtering(FDAF)to depress DPI is proposed in this paper.The algorithm combines adaptive tilt- ering and replica correlator(or matched filter processing)technology. First, the novel frequency-domain adaptive filtering to the data that come from the receiver array is applied. Secondly, the output of adap- tive filtering is correlated with a replica of the transmitted pulse. Finally, the target echo is extracted and DPI is eliminated. Compared with basic LMS algorithm, the new FDAF algorithm with variable step-size factor leads to a considerable reduction in computational complexity, and improves the convergence rate and basically ensures the DPI suppression and the extraction of target echo during a ping of an active sonar transmission Numerical experiments prove that the proposed algorithm is superior to the conventional method in the presence of strong DPI,especially in some aspects such as accuracy and robnstness of target echo extraction.