A Method for Wideband Interference Suppression Based on Conditional Frequency-Wavenumber Spectrum Density

Estimating the direction of arrival (DOA) of weak targets in strong broadband interference environments has been a significant challenge. Reducing the mainlobe width of the broadband beamformer and suppressing interference leakage are effective ways to enhance the weak targets. To do this, this article introduces an interference cancellation method based on the frequency-wavenumber (FK) spectrum. The Fourier transform is applied to the signals, followed by the spatial transformation along the array element, obtaining the FK spectrum. Subsequently, the interference and its leaky energy distributed on the conditional FK spectrum density are adaptively nullified. The final broadband beamforming is obtained by synthesizing this reduced spectrum density. This approach provides energy compensation effect for the high-frequency components of the signal, inherited from FK-based beamforming methods, demonstrating high angular resolution. Furthermore, it designs the beamforming weight in the FK domain, enabling precise suppression of multiple interference signals, thereby significantly enhancing the weak target. Experimental data indicate the method of a high angular resolution, effectively reducing detection blind spots by 42%. When the angle difference between the target and the interference is 4°, the SINR can be improved by more than 3.9 dB.