Iterative algorithm and performance of amplitude adaptive beamformer in interference and noise environment
H. S. C. Wang · The Journal of the Acoustical Society of America · 1977
Following the concept of an optimum amplitude shading beamformer in an interference and noise environment reported earlier [H. S. C. Wang, J. Acoust. Soc. Am. 56, S18(A) (1974); 61, 1251 (1977)], an iterative algorithm for the realization of such a signal processor is 6formulated. This algorithm essentially follows the steepest descent path of the total received interference and noise power at the beamformer output subject to the constraint that the main beam signal response is maintained at a fixed level. It is demonstrated that, for an interference incident on the first minor lobe of a line array 4.4 wavelength long, the algorithm reduces interference power to below ambient noise level in fewer than ten iterations and improves output SNR by 11 dB within 100 iterations. If the interference incidence is within the main beam (6.5° from MRA), approximately 40 iterations are needed to provide a 17-dB improvement of output SNR. When the interference is very close (2.5°) to MRA, the algorithm can still improve SNR by 6 dB within 500 iterations. Numerous beam patterns are exhibited to demonstrate their metamorphosis during the course of iterative optimization. It is estimated that the effectiveness/cost ratio of such a processor would be substantially higher than conventional adaptive beamformers.