Passive ranging sonar based on multi-beam towed array

In this paper we study passive range estimation using various beamformer for a linear hydrophone array. One common method of determining the time delay and, hence, the arrival angle relative to the sensors axis is to compute the cross correlation function. Because of the finite observation time, however, the cross correlation function cannot be precisely calculated. We make appropriate sub-arrays in a linear array of N sensors and apply the beamformers such as a conventional beamformer, weighted-and-sum to compare. These beamformers of the sub-arrays make their own beams in equal increments to the equal-range in the known direction of the target step by step, the opposite side of the array make beams, also. As a result of these, the maximum values can be determined by measuring the power of summed output of the each beamformer. Performance of passive range estimation based on conventional beamformers is compared with a method using time delay estimation, it analyzes the range estimation error according to the bearing estimation error.