Phase-Only Beam Broadening of Contiguous Uniform Subarrayed Arrays

In modern antenna systems, beam broadening of subarrayed arrays provides continuous coverage of a wide angular extent in a cost-effective manner. While many methods have been published that address beam broadening of traditional (non-subarrayed) arrays, there is a knowledge gap in the published literature with respect to efficient beam broadening of contiguous uniform subarrayed arrays. This article presents efficient methods for beam broadening of contiguous uniform subarrayed arrays where the excitation of each element is not individually controlled, but the elements of the array are grouped together as subarrays to have the same element excitations. Particularly, this article focuses on phase-only optimization to preserve maximum power output. Three modified iterative Fourier transform (IFT) methods and one genetic algorithm (GA) are presented to efficiently search the vast solution space of possible phase settings for a solution that satisfies the desired broadened pattern. These methods are evaluated on idealized 1 \times 40 and 1 \times 80 linear arrays with five element subarrays and 40 \times 40 and 80 \times 80 element rectangular arrays with 5 \times 5 element subarrays. The proposed modified IFT methods are found to be faster than the GA approach, while the GA approach only offers a few percentage points of better effectiveness.