Optimal subarray selection strategy for long towed array based on target range

Abstract

The larger the aperture of the towed array, the higher the array gain. However, when the aperture dimension is very large, the far field assumption may no longer hold. As such, simply using the plane wave beamforming method with the whole array to obtain the target signal will inevitably cause signal distortion. This article first proposes that in order to obtain less distorted signal, the coherence bandwidth of the beam-domain signal should be larger than the bandwidth of the source signal. Following, this paper analyzes the locating performance of the towed array. It is shown that the bearing estimation is more accurate than the range estimation. However, when the shape of the towed array is almost colinear, the range of the target can be approximately estimated. Hence, this paper puts forward a dynamic aperture choosing algorithm according to the target range, which dynamically selects the optimal subarray to perform appropriate beamforming method by trading-off between the array gain and the coherence bandwidth. The sea trial data verifies the feasibility of estimating the target range by long towed array when the tow ship moves slowly in a straight line. Simulation results show that this algorithm has better performance than previous methods when the targets are located at any range.