A Linear Near-Field Interference Cancellation Method Based on Deconvolved Conventional Beamformer Using Fresnel Approximation

In underwater acoustic detection using towed arrays, the in-band radiation noise of the tow-ship generates significant interference. In this article, a high-resolution spatial filter based on the deconvolved conventional beamformer (dCv) is proposed to mitigate the impact of this noise on the detection on the beam of interest. The tow-ship interference is near field, thus, the dCv cannot be applied directly as the point spread function is shift variant. In this work, a solution to this problem involving the Fresnel approximation is developed. It is demonstrated analytically that the Fresnel approximation is not sensitive to the accuracy of the estimation of the interference range, and its applicability depends on the arrival angle of the interference. Experimental results show that the linearity of the dCv spatial filter ensures that the amplitude and phase of the array signal can be retrieved with no distortion, which is critical for acoustic detection.