Design and Implementation of a Reconfigurable Transmitarray Employing Varactor-Tuned Huygens Elements for Dynamic Beam Shaping

Abstract

Most conventional reconfigurable transmitarrays rely on multilayer frequency-selective surfaces and PIN diodes, limiting transmittance and multibit modulation, which constrains beamforming accuracy and gain enhancement. In this letter, we propose a phase-modulated reconfigurable transmitarray prototype featuring a Huygens element modulated by two varactor diodes to achieve multibit and highly transmissive cell performance, thus enabling a wide range of highly precise beam modulation in transmissive mode. Specifically, the reconfigurable transmitarray board has two varactor diodes inserted into the sliding symmetric dipoles printed on a bilayered dielectric substrate, achieving Huygens resonance with an average transmission amplitude of 0.8 dB and enabling dynamic 2-bit phase compensation. In addition, the derivation and simulation results of the equivalent circuit based on the lattice network demonstrate the design of the tunable Huygens metasurface can change the intensity of Huygens electromagnetic resonance. The fabricated transmitarray prototype provides matched 2-bit phase modulation, with phase states separated by approximately 90° according to measurements in an anechoic chamber. Beam measurements of the prototype show a beam sweep angle of up to 50° corresponding to a 4 dB gain loss, an aperture efficiency of 27.5%, and a 3 dB gain bandwidth of 6.3% from 10.7 GHz to 11.4 GHz.