Sample Selection Method and Solution to Interference Incidence Angle Variation in Multi-Channel SAR Anti-Jamming Based on ADBF

To solve the anti-jamming problem of multi-channel SAR, adaptive beamforming technology can be used to enhance the desired signals and suppress the interference. In the process of beamforming, when calculating the optimal weight vector of each array element, it is necessary to estimate the interference-plus-noise covariance matrix by selecting interference and noise data samples. If the selected data samples are mixed with target signals, the target will be misjudged as interference and suppressed. This paper aims at the problem of sample selection in the anti-jamming process of multi-channel SAR, by eliminating the target component within the main clutter width in the azimuth frequency domain, the interference and noise data samples can be obtained, and then the covariance matrix can be calculated for beamforming. Another concern of this article is that the interference incidence angle varies with the movement of aerial carrier, so that the optimal weight vector obtained from the signal within a certain azimuth range may not applicable to the whole azimuth range. Regarding this issue, one method is to divide the azimuth pulses into several parts and recalculate the weights in each section, and the other method is to estimate weights in frequency domain then suppress interference in time domain. The effectiveness of the proposed methods is verified by imaging results of measured data, interference to noise ratio and signal to noise ratio. Compared with the direct sample selection method, the adaptive sample selection method improves the signal to noise ratio by nearly 8dB and decreases the interference to noise ratio by nearly 6dB, indicating that this method effectively saves the target and suppresses the interference. Both methods for the issue of interference incidence angle variation have achieved good interference suppression effects, and the interference to noise ratio has decreased by 11.32dB.