Computationally Efficient Narrowband RFI Mitigation for Pulse Compression Radar

Mitigating in-band, continuous-wave (CW) radio frequency interference (RFI) is a common problem for radar systems which themselves may employ continuous-wave waveforms. The source of this RFI can be intentional or unintentional spectral artifacts of near-by narrowband communications systems. Radar signal modulations of just a few megahertz are frequently quite broad compared to the modulation bandwidths of the interferers. So, characterization of RFI by a simple tone can be sufficient to assess its impact. When the RFI sources are unanticipated or of uncertain characteristics, there is motivation to mitigate them in a responsive manner in receive processing. A computationally efficient RFI cancellation method for receive is described here. Salient properties of this method are the recovery of radar sensitivity in the presence of narrowband RFI and the preservation of pulse compression time sidelobe levels. In fact, the technique described here overcomes the disadvantages of isolating and removing an RFI source that is completely immersed in the radar waveform in both time and frequency. While removing each of possibly multiple RFI sources with surgical IIR filters, little secondary influences on pulse compression responses arise because the IIR filter is suitably designed with finite word influences and impulse-response time sidelobes in mind.