Methods of synthesis of overlapped subarrays with flat-topped radiation patterns in planar phased array antennas

Abstract

One of the approaches to the design of phased array antennas (PAA) for beam scanning in a limited region of space is associated with formation of overlapped subarrays with flat-topped radiation patterns of width equal to the width of the scan region. Unlike linear subarrays, for which there exist many technical solutions, planar overlapped subarrays can be formed by two ways. One of them is based on cascade connection of linear subarrays arranged perpendicularly to each other. Another way is based on use of beamforming networks. Since the problems concerning synthesis of overlapped subarrays with flat-topped patterns in planar PAA is not yet sufficiently considered in the literature, the indicated problem remains of interest. The work considers two methods of synthesis of planar overlapped subarrays with flat-topped radiation patterns. One method is a conventional method based on Fourier transform of the required radiation pattern. Another method introduced in the paper is new one. It allows determination of amplitude distribution over subarray aperture with providing maximum level of the subarray factor in the broadside direction and with taking into account power balance distributed over the subarray radiating elements. The proposed method is compared with the conventional method based on the Fourier transform, and advantages of the former method over the latter one are shown. The paper contains results obtained for amplitude distributions for a few cases of subarray excitation and appropriate subarray factors characterizing the capabilities of the new method. The method proposed in the paper can be applied in the further studies concerning development of networks for feeding overlapped subarrays in planar limited-scan PAA of modular construction.