Transmit beamformer design with nonlinear optimization

Two methods for maxmin transmit beamformer design with multiple simultaneous beams are compared. Both methods involve convex optimization with semidefinite relaxation. In the proposed method, resulting beamformer is taken as an initial estimate for another optimization problem which is nonconvex and nonlinear. As a second method, a well-known procedure, randomization is used. Comparisons are made using total power and phase-only constrained beamformers. It is shown that the proposed approach performs better than randomization.