Beam-Steerable Passive Transmitarray Optimized Based on an Adjacent Algorithm

Abstract

This paper presents a novel adjacent algorithm for the design of a beam-steerable passive transmitarray (TA) antenna. Even if the beam of a feed antenna is steering by varying the phase offset of the antenna array forming the feed antenna, the existing passive TA, which improves the gain only in the boresight direction, cannot improve the gain in all directions in which the beam is steering. To minimize the difference in the phase shift between different phase offsets by adjusting the reference phase instead of searching the entire space made up of the reference phase of each phase offset, an adjacent algorithm to change the reference phase with an adjacent phase that minimizes the objective function was adopted. This strategy improved the $O$ ( $\text{n}^{\mathrm {k-1}}$ ) algorithm to a linear algorithm of $O$ (n). It was also experimentally shown that optimization using the adjacent algorithm did not change the final result regardless of the initial value. Weighing the magnitude of the electric field (E field), the average optimized phase shift was obtained to determine the phase shift of the passive TA unit cell. Simulation of a TA consisting of an effective simple medium with a thickness of 2.5 mm reflecting the previously determined phase shift showed that the gain was improved by less than 1 dB when the phase offset was 0° and by more than 1 dB when the phase offset was 75°.