A robust formulation of an optimum cross‐spectral beamformer for line arrays

For linear arrays of equispaced hydrophones the power‐directional spectrum can be computed efficiently from the cross‐spectral matrix by means of the fast Fourier transform. We show how this can be done when the estimator structure is the conventional beamformer, and also when the estimation is accomplished by optimum (minimum variance) beamforming. It is shown that by computing a measure of superdirectivity it is possible to form a more robust estimate of the power‐directional spectrum as a linear combination of the other two estimates. Since the computations are done with the averaged cross‐spectral matrix the additional computer loading is small.