Detection of passive weak signals based on high gain wide-band beamformer

A wide-band beamforming scheme for uniform circular array is proposed to improve the detection performance for weak passive signals in this paper. In our processing scheme, the wide-band signals sampled from the underwater acoustic array are firstly decomposed into different narrow-band signals using FFT, and then the narrow-band high gain beamforming process is performed for each subband of the FFT outputs. The subband beamformer outputs are squared and summed using the Eckart weighting coefficients. The length of FFT is selected to make every subband satisfy the condition of narrow-band assumption. The fifty percent of overlapping ratio and -30 dB sidelobe level Chebyshev window are used for FFT processing to obtain better system performance. This approach was employed to process some wide-band experimental data recorded from a 24-element circular array at a lake in China. Compared to the conventional beamforming, enhanced detection performance is obtained without improving the complexity of realization.