Dot‐shaped transmit beamforming with nonuniform time‐modulated concentric circular frequency diverse array

Abstract

In this study, a true three‐dimensional dot‐shaped beamforming, in which the transmitted energy in a spatial region (azimuth, elevation, and range) is focused is performed with the nonuniform time‐modulated concentric circular frequency diverse array (NUTM‐CCFDA). The CCFDA structure with a radially outward increasing frequency offset between the rings has structural symmetry that provides the advantage of full scanning in the azimuth plane without any significant change in beam shape. Moreover, the NUTM, where the antenna elements are simply excited with a different modulation frequency in each ring, uses the in‐phase/quadrature channel modulator to realize a single sideband. The proposed NUTM‐CCFDA structure exhibits efficient beam scanning with the switch time‐on instant without using variable phase shifters to steer the dot‐shaped beam. Thus, NUTM‐CCFDA not only realizes a true dot‐shaped beam with better angle resolution on the first harmonic components but also has a simpler configuration than the conventional frequency diverse arrays with sophisticated variable frequency/phase shifters.