Analysis of interference suppression performance in MR-FDA-MIMO radar

In this paper, we primarily analyze three situations affecting mainlobe interference suppression performance in minimum redundancy frequency diverse array multiple-input multiple-output (MR-FDA-MIMO) radar. The MR-FDA-MIMO radar breaks through the degrees of freedom (DOF) in the transmit dimension, the number of mainlobe interference suppression beyond the number of transmit elements. Utilizing a two-step beamforming technique, MR-FDA-MIMO mitigates sidelobe interference in the receive domain and counteract multiple false targets in transmit virtual domain. This paper provides a detailed analysis of the mainlobe interference suppression performance of MR-FDA-MIMO radar in the transmit virtual domain. First, the optimal output signal-to-interference-plus-noise ratio (SINR) based on the virtual array is derived, ultimately resulting in $SIN{R}_{out}=SNR+10\log \left(2M_M+1\right)$. Second, considering the presence of a true target in the virtual samples, the virtual covariance matrix is derived, showing that the power of the true target doubles in the virtual covariance matrix. Finally, the properties of the cross terms in the virtual covariance matrix for the multiple virtual samples algorithm are analyzed, and it was found that they are located between the false targets, and their number is related to the number of false targets Q, specifically, the number of cross terms is Q(Q-1)/2. The effectiveness of the analysis is verified through simulation examples.