Beamforming a towed line array of unknown shape

Beamforming a curved towed array of known shape is easily done by matching the received signals to the calculated signals for an incident plane wave. If the array shape is unknown, the beam pattern can be calculated for the array moving along an assumed space–time curve. The sharpness of the beam pattern is defined as the sum of the squares of the beam outputs in different look directions. Next the space–time curve is changed by an iteration procedure until the sharpness is maximum. Sample calculations for simulated and actual data show that this method generates an improved beam pattern and, in the simulated data case, a good estimate of the true array space–time curve.