A novel robust adaptive beamforming based on diagonal loading is proposed in this paper, aiming at robustness against steering vector mismatches in spatially colored noise fields. The received data is prewhitened first according to the noise covariance, with a corresponding ellipsoidal steering vector uncertainty set defined at the same time. Then the loading level is determined based on worst-case performance optimization. Other than searching for the optimal loading by iteration, a simple closed-form solution is suggested after some approximations. Besides its low computational cost, the closed-form solution reveals how different factors affect the optimal loading. Numerical examples confirm the excellent performance of the proposed approach as well as the accurate approximation of the closed-form solution to the actual optimal loading.
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