RFI Suppression Method with Improved Eigen Subspace Decomposition for Low-Frequency Radar

Due to the complex electromagnetic environment in the low-frequency band, both useful signals and other radio frequency (RF) signals enter the radar receiver indiscriminately, affecting the operation of the radar. Conventional radio frequency interference (RFI) suppression methods only have a good effect on narrowband interference (NBI). Faced with the complex RF environment, they cannot effectively suppress RFI, especially wideband interference (WBI) in the form of digital terrestrial multimedia broadcast (DTMB). To solve the problem of RFI suppression in the complex electromagnetic environment, an improved eigen subspace decomposition method is proposed in this paper. First, the echo signal matrix is implemented with eigendecomposition to obtain eigenvalues with different distribution characteristics, and the ratio of adjacent eigenvalues is used to detect whether there exists NBI in echo signal. Then, the NBI is modelled and estimated. According to the distribution characteristics of different eigenvalues after NBI suppression, those eigenvalues including WBI are determined by K-means clustering. Then, the interference subspace of WBI is accurately constructed, and the WBI can be suppressed. Through the processing of simulated and measured data, it can be proved that the proposed method can effectively suppress complex RFI.