An adaptive beamforming algorithm for broadband active sonar

An adaptive beamforming algorithm was developed for broadband active sonar with a convergence time on the order of the pulse duration and effective interference nulling capabilities which enhance desirable echoes. The algorithm is an element based time domain implementation in which beam data that is formed in the direction of each interferer is successively subtracted from the element data using an adaptive FIR filter. The algorithm was applied to impulsive source sonar data received on a bottomed hydrophone array. Collected data contained interfering active returns and noise from nearby shipping as well as desirable echoes from passive reflectors placed near the array. In a representative example, the algorithm adapted fast enough to null out active interference as well as shipping noise, which enhanced the signal to noise ratio of a passive reflector echo by 6 dB