Abstract:

An adaptive beamforming algorithm based on nonlinear constraint was presented. Firstly, the algorithm modified the eigenvectors corresponding to signal subspace of the covariance matrix of the receiving signals. SOI(signal of interest) was not contained in the modified covariance matrix but interference signal and noise were contained. Then LCMV (linearly constrained minimum covariance) method and the modified covariance matrix were adopted in the new approach to obtain weight vector of adaptive pattern. To improve the robust characteristics, nonlinear constraint method was used to optimize the weight vector of adaptive pattern. The final solution of weight vector was different from alterably diagonal loading and the unknown parameter in optimal solution can be obtained easily and accurately. The SINR (signal to interference plus noise ratio) of the new algorithm has robust characteristics for random steering vector errors and is not sensitive to power change of SOI. Simulation results prove the validity of the new algorithm.

Key words: array antennas, nonlinear constraint, beamforming