Adaptive Gradient Search Algorithm for Displaced Subarrays With Large Element Spacing

In this letter, an adaptive gradient search algorithm for displaced subarray optimization is presented. The displaced subarray technique, which is able to suppress the high grating lobes caused by large interelement spacing (i.e., over one-half wavelength), has attracted much attention. In this case, it could reduce the number of active elements as well as the cost of conventional phased array antennas. However, the optimal solution of each displaced subarray location is hard to achieve. The proposed algorithm is a practical method to solve such a nonconvex problem. By gradually reducing the iteration step size, when the search times of each step are enough, the solution is able to converge to a satisfying solution. The effectiveness and the stable performance of our proposed method are verified by various numerical examples.