Beamforming of broad-band bandpass plane waves using polyphase 2-D FIR trapezoidal filters

A new discrete-domain method is proposed for the beamforming of temporally broad-band bandpass plane waves (PWs) using a real-coefficient 2-D spatio-temporal (ST) finite-impulse response (FIR) filter having a novel rectangularly symmetric double-trapezoidal-shaped passband. The arriving temporally broad-band-bandpass ST PWs are received by a 1-D uniformly distributed sensor array. The sensor signals are pre-filtered, down-shifted to the intermediate frequency (IF) band, low-pass filtered and synchronously sampled by the real IF tri-stage temporal sampler array, resulting in a real-valued 2-D sampled sequence. The beamforming operation is then carried out on this 2-D sampled sequence using the real-coefficient 2-D FIR double-trapezoidal filter. Arithmetic complexity in the hardware implementation of the 2-D FIR double-trapezoidal filter is significantly reduced by using an array of real-coefficient polyphase 1-D FIR filters. Experimental results have confirmed that this method is capable of enhancing the desired temporally broad-band-bandpass ST PWs according to their directions of arrival under severe co-channel interference.