A novel hardware configuration for an adaptive beamforming array using quadrature mirror filter banks

Abstract

The performance of a novel multirate subband adaptive beamforming array is evaluated. Instead of the traditional fast Fourier transform (FFT) filter, the quadrature mirror filter (QMF) bank is used here to partition or to subband the incoming signal frequency band. The QMF bank divides the spectrum into the lower and higher subbands. Beamforming is then carried out for both of these subbands. In this paper, the same concept is used, except for the fact that only one of the two subbands (in our case, the lower) is optimized for the desired subband output. This signal is then passed through a multiplier or a transformer, which generates the same output as the other subband (in our case, higher). Both the optimized and transformer outputs are then combined to produce the final signal. This method reduces the circuit complexity as well as the cost of the subband adaptive beamformer. The radiation responses, the mean-square errors, and the eigenspectrums are subjected to investigation. It is observed that the beamforming performance and the mean-square errors (MSE) remain the same for both the previous and novel configurations. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 21: 140–145, 1999.