On the attenuation of interference and mutual coupling in antenna arrays using 3D space-time filters

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.