RFI and Mainlobe Jamming Mitigation for Multi-Channel Imaging Radars.

摘要

A common approach to suppressing jamming or RFI is (adaptive) beamforming, where an antenna pattern null is formed by appropriately combining multiple receive channels. A sidelobe canceller is a common such implementation. Beamforming is undesirable when the interference source is in the mainlobe of the radar, because the antenna pattern null created by the beamformer produces a region where ground imaging cannot be performed This paper presents two conceptual alternatives to spatial beamforming. The first approach produces a SAR image by combining the pulse returns from multiple channels in a nonseparable way. This 'space time beamforming' is shown to produce a null which is significantly narrower and shallower than that produced by conventional spatial beamforming. Further, we demonstrate that the space time beamforming null becomes narrower as the length of the synthetic aperture (i.e., the doppler resolution) increases. A second alternative to spatial beamforming is presented which is useful when the interference source is nonwhite or when it is desirable to estimate the (spatially localized) interfering signal. This signal separation approach allows generic localized sources such as moving target signatures, vibrating target paired echoes, etc. to be separated from the clutter data.