Imaging on Underwater Moving Targets With Multistatic Synthetic Aperture Sonar
Chou-Wei Kiang, Jean‐Fu Kiang
Abstract
A multistatic synthetic aperture sonar (SAS) configuration, composed of an active sonar, a towed receiver and a sonobuoy, is proposed to acquire the image of a moving target and estimate its velocity vector. The range model incorporates the time delay of an acoustic pulse between its emission and backscattered from the target to the receivers. An image is acquired from the received signals at one receiver after range cell migration correction (RCMC), range walk compensation (RWC) and compression, without prior knowledge on the motion parameters of the target. Range-frequency reversal transform (RFRT) and a modified second-order Wigner-Ville distribution (SoWVD) are used to estimate the chirp rate in the range model, and Radon transform is used to estimate the Doppler centroid. The velocity vector of the moving target is accurately estimated, within 3% of error and insensitive to noise, by using the Doppler centroids derived from the signals at the three receivers. Eight different scenarios are simulated to demonstrate the efficacy of the proposed method. The shape and size of the moving target can be clearly identified in all but one case. Three state-of-the-art methods are also used to verify the accuracy of the proposed method, the effects of noise are analyzed, and autofocus algorithms are applied to enhance the acquired images in some difficult cases.