Amplitude-adaptive beamformer for planar arrays
H. S. C. Wang · The Journal of the Acoustical Society of America · 1980
An amplitude-adaptive beamformer configured for a class of planar arrays with quadrantal symmetry is conceived and described. The adaptive algorithm is developed based on the principle that directional interferences and noise can be rejected or minimized by adjusting the amplitude shading of the array elements with their phase shifts fixed [H. S. C. Wang, J. Acoust. Soc. Am. 61, 1251 (1977); J. Acoust. Soc. Am. Suppl. 1 62, S51 (1977)]. The algorithm utilizes an estimate of the covariance matrix of the interference and noise field from properly sampled and delayed “quad signals” of the array, thus reducing the number of independent adaptive channels by a factor of four. It can be shown that the algorithm converges to the optimum shading solution previously reported by the author. The performance of such an adaptive beamformer was demonstrated by simulation on a digital computer with a two-tone interference incident on a side lobe of a 52-element planar array. In a typical example, interference power at the beamformer output was reduced by 40.9 dB after 20 iterations.