Optimal Sidelobe Reduction of Matched Filter for Bistatic Sonar

For bistatic sonar, the weak signal of target is often buried by the side lobes of strong direct blast after pulse compression. A method is proposed in this paper to suppress the side lobes of matched filter output. The basic idea is to design an FIR filter at the output of matched filter, so that to minimize the ISL (Integrated Side lobe Level), while keeping the main lobe unchanged. The optimal solution is achieved utilizing the convex optimization method. In numerical simulation, the performance of the method is compared with conventional matched filter plus Hamming window methods. The performance is improved 30dB with output gain unchanged simultaneously. The method is also used to design a close-in side lobe-free filter. The close-in side lobe level could achieve-80dB in the simulation.