Radio Frequency Interference Cancelation for Skywave Over-the-Horizon Radar

In the user-congested high-frequency band, skywave over-the-horizon radar (OTHR) is easily interfered by radio frequency interference (RFI). Among the existing methods, transient and nontransient RFIs are suppressed by time-domain methods and beamforming methods, respectively. However, the existing beamforming methods cannot work in transient cases, whereas the time-domain methods are usually time-consuming and suffer performance loss in mass interference cases. Therefore, a unified method for two kinds of RFI cancelation is preferred. In this letter, based on the frequency characteristics of the RFI and the regular processing procedure of the skywave OTHR, an adaptive RFI cancelation scheme is proposed. In this scheme, the RFI is localized in the frequency domain, after which snapshots are chosen to complete the frequency-domain adaptive beamforming. The proposed scheme makes it possible to completely cancel both kinds of RFI in the beamforming stage, which is timesaving and proper for practical application. The performance of the proposed scheme is evaluated by experimental data.