Mirroring Properties of Sub-band Adaptive Beamforming Arrays using Quadrature Mirror Filter Banks
The concept of the sub-band adaptive beamforming arrays (ABA) is derived from the conventional fullband adaptive antenna arrays. Instead of doing the beamforming for the entire frequency band as in the full band ABA, only one sub-band of the frequency band is subjected to the same in here. The sub-banding of the full frequency band is done here by a quadrature mirror filter (QMF) bank. In a previous attempt, an approximate method has been proposed to reproduce the higher sub-band output from the lower sub-band output . However, the higher sub-band has higher centre frequency, which demands higher Nyquist bandwidth. This will increase the operational complexity of the sub-band ABA. Recently it has been shown that the QMF sub-band adaptive beamforming can be performed by optimising the higher sub-band output and then, multiplying the signal output with a transforming factor that generates the lower sub-band output . The lower frequency band requires only lower Nyquist bandwidth. It is believed that this will reduce the hardware complexity, the cost and the workload of the earlier version of the QMF sub-band ABA system . In this work, a hardware implementation and its characteristics of such a sub-band ABA to generate the combined output from the higher sub-band is investigated.
KeywordsMean Square Error Wideband Signal Quadrature Mirror Filter Lower Subband Entire Frequency Band
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