Space-time digital filtering of radio astronomical signals using 3-D Cone Filters

Abstract

In this paper, 3-D space-time (ST) processing is proposed as a technique to enhance signals of interest (SOIs) by attenuating near-over-the-horizon radio frequency interferences (RFIs) that exist on dense phased arrays used in the next generation of radio telescopes. The proposed approach is based on the difference between the regions of support (ROSs) in the 3-D frequency domain of the Fourier transforms of the SOIs and RFIs. A 3-D linear phase filter bank structure, consisting of 1-D FIR filters and 2-D circularly symmetric FIR filters, is employed to suppress the RFIs. The performance of the proposed 3-D ST filtering approach is illustrated using synthesized broadband (BB) SOIs and BB RFIs on dense aperture arrays (DAAs) and on focal plane arrays (FPAs). Results are presented that indicate the potential for successful mitigation of near-over-the-horizon BB RFIs without significantly distorting the BB SOIs. The advantage of the proposed ST filtering approach is its inherent capability of BB processing.