Phase-only Robust Minimum Dispersion Beamforming

A phase-only robust minimum dispersion (PO-RMD) beamformer is devised for non-Gaussian signals. The proposed PO-RMD employs a constant-modulus constraint on the weights, which is equivalent to simply phase shifting at each antenna. It adopts the minimum dispersion criterion to utilize the non-Gaussianity of the signals while employing the worst-case constraint to achieve the robustness against model uncertainty. A gradient projection algorithmic framework is developed to solve the resulting nonconvex optimization problem. In order to find a feasible point in the intersection of the constant-modulus and robustness constraint sets, an alternating projection algorithm is devised. More importantly, the closed-form expressions of the projection onto the two sets are derived, respectively. Simulation results demonstrate the effectiveness, accuracy and robustness of the PO-RMD.