A 3D space-time filtering method is proposed for attenuating undesirable electromagnetic signals that propagate at or close to light speed across the surface of the plane that contains an array of antennas. Such signals may include the so-called radio frequency interference (RFI) that emanate from sources that lie well outside the directions of arrival (DOAs) of the signals of interest (SOIs). They may also include the intra-plane inter-antenna signals that result from the undesirable electromagnetic mutual coupling that exists between rectangularly-spaced antennas in aperture arrays (AAs) and in the focal plane arrays (FPAs) of paraboloidal dishes. Such signals have 3D space-time spectra possessing regions of support (ROSs) that are close to the surface of the 3D spectral light cone. They can therefore be attenuated by means of 3D space-time filters having 3D stopbands that include and encompass the surface of this light cone. Such a 3D space-time filter is described here and used to evaluate the validity of the proposed approach. Numerical results confirm that the proposed method significantly attenuates broadband RFI signals and moderately suppresses mutual coupling.

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. RFI mitigation workshop