Adaptive beamforming is sensitive to steering vector (SV) and covariance matrix mismatches, especially when the signal of interest (SOI) component exists in the training sequence. In this paper, we present a low-complexity robust adaptive beamforming (RAB) method based on an interference–noise covariance matrix (INCM) reconstruction and SOI SV estimation. First, the proposed method employs the minimum mean square error criterion to construct the blocking matrix. Then, the projection matrix is obtained by projecting the blocking matrix onto the signal subspace of the sample covariance matrix (SCM). The INCM is reconstructed by replacing part of the eigenvector columns of the SCM with the corresponding eigenvectors of the projection matrix. On the other hand, the SOI SV is estimated via the iterative mismatch approximation method. The proposed method only needs to know the priori-knowledge of the array geometry and angular region where the SOI is located. The simulation results showed that the proposed method can deal with multiple types of mismatches, while taking into account both low complexity and high robustness.

This paper presents a robust mathematical framework and algorithmic implementation for the design of fractional delay (FD) filters based on the Farrow structure. Although the conventional weighted least squares (WLS) approach provides a computationally efficient design, it typically suffers from prominent localized magnitude error peaks in specific regions, particularly at high frequencies and extreme fractional delays. To resolve this issue, an iteratively reweighted least squares (IRLS) optimization algorithm is proposed. By dynamically updating the weighting matrix according to the error distribution from preceding iterations, the IRLS algorithm steers the $L_2$-norm solution toward a minimax ($L_{\infty }$) equiripple design. Experimental evaluations demonstrate that the proposed method suppresses the peak magnitude error by 8.1 dB, yielding an approximately equiripple error surface across the frequency-delay plane.