Research On Beamforming Algorithm Of Reconstructing Interference-Plus-Noise Covariance Matrix

Beamforming algorithm makes antenna array get information on particular direction by adjusting weighting coefficient on different array elements. The minimum variance distortionless response (MVDR) beamforming algorithm can achieve good output performance under ideal conditons. However, subject to sampling points, orientation error or desired signal existing in sampling signals, the performance of algorithm may decline. The dissertation focuses on interference-plus-noise covariance matrix reconstruction (CMR) algorithms for different conditions. By using the matrix reconstructed to replace sampled covariance matrix, the impact of desired signal existing in sampling signals can be weakend, and the output performance of algorithms under high SNRs conditions can be enhanced.The antenna array model and several typical beamforming algorithms are firstly described in this dissertation, and the impact of system error to output performance is analyzed. Then, a revised interference orientation based CMR (IOB-CMR) algorithm is proposed. By adding Lp norm and L2norm constraint on its cost function respectively, the output performance is improved when the interference orientation error exists. The ESB-CMR algorithm based on eigenvalue decomposition is also proposed, which does not need DOA of interference signals as prior information with good robustness. Then, combine the ESB-CMR algorithm with the modified array algorithm as well as the forward backward spatial smoothing (FBSS) algorithm, which are named as the MESB-CMR algorithm and the FBSS-ESB-CMR algorithm. These algorithms are suitable for coherent signals conditions. For the number limitation of processible coherent signals in the MESB-CMR algorithm and the array aperture lost in the FBSS-ESB-CMR algorithm, the Toeplitz-ESB-CMR algorithm is proposed, which uses the eigenvector corresponding to the maximum eigenvalue to construct Toeplitz matrix. At last, combine the ESB-CMR algorithm and the Toeplitz-ESB-CMR algorithm with the incoherent signal-subspace method (ISM) to process frequency domain signals in wideband signals conditions. These algorithms can avoid the procedure of frequency focusing in coherent signal-subspace method (CSM). The performance of the algorithms proposed in this dissertation is evaluated and analyzed by simulation experiments.