Enhanced Wideband Adaptive Arrays with Different Length Quadrature Mirror Filter Banks

The performance of a sub-band adaptive beamforming array (ABA) using different length quadrature mirror filter banks (QMF) for wideband signals is investigated. Delay taps have to be introduced to the full band ABA for wideband signalsʹ operation for deep suppression of the interference. The addition of more taps may result in an increase of uncorrelated noise to the ABA operation. Hence an undesirable power loss at the direction perpendicular to the ABA may occur. The problem of the loss introduced by the additional taps is overcome by introducing a QMF based sub-banding concept. In this paper, different kernels QMF banks are used for the evaluation and hence the comparison of the beamforming application. The beamforming performance of the ABA using the short kernel QMF (eighth order) sub-band ABA is compared with that using a long kernel QMF (sixteenth order). The sub-band ABA with long kernel QMF shows improved signal gain and deep suppression of interference (similar to the short kernel QMF) in the direction perpendicular to the ABA, compared to the full band ABA.