Hybrid Reflectarray Antenna of Passive and Active Unit Cells for Highly Directive Two-Direction Beam Steering

Abstract

A hybrid reflectarray antenna (RA) composed of passive and active unit cells that can steer a beam into two selected directions with high aperture efficiencies is designed and experimentally verified. The hybrid RA is implemented by a combination of one-bit active and passive unit cells, which enables the quantization of phase profiles of the reflection coefficients on the antenna surface to 120°. This combination can improve the quantization efficiency of the conventional one-bit reconfigurable RA quantized with 180°. A combination of the passive unit cells of which the phases of reflection coefficients are 180° is determined to be included simultaneously in two quantized phase profiles for two-direction beam steering. As a proof of concept, the hybrid RA operating at 10.1 GHz is designed to steer the beam to the vertical angles <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\theta $ </tex-math></inline-formula> of −18° and 18° on the E-plane. By comparing them with those of the one-bit RA, we confirmed that the aperture efficiencies are improved by 41.85% and 69.41% in simulations and by 37.19% and 60.19% in measurements for the vertical angles <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\theta $ </tex-math></inline-formula> of −18° and 18°, respectively.