Reconfigurable Transmitarray Based on Frequency Selective Surface for 2D Wide-Angle Beam Steering

Abstract

A novel reconfigurable transmitarray (RTA) with two-dimensional (2D) wide beam steering capability is presented herein. Different from the traditional RTA with the discrete phase compensation (one-bit or multi-bits phase shift), a second order parallel bandpass filter model is used to realize the RTA elements with a 180° continuous phase compensation. A sandwich structure composed of the two patches with rectangular slots and the middle ground sheet with the cruciform slot is constructed for the phase shift characteristics of the frequency selective surface (FSS), and two varactor diodes are loaded across the rectangular slots on the two top and bottom patches. The simulated results show that the proposed elements could achieve continuous transmission phase compensation from 0° to 180° with a 3 dB insert loss within the operating band of 11.8–12.6 GHz. The RTA prototype with 16×16 elements and an aperture size of 6λ0×6λ0 at 12.2 GHz is fabricated and measured for experimental verification. The measured results show that its beam scanning range can reach ±50° in both horizontal and vertical planes with a peak gain of 22.76 dBi and a aperture efficiency of 24.65%. Furthermore, the sidelobe levels (SLLs) are lower than −17.8 dB, which is much better than most RTAs. The proposed RTA has potential applications in radar, microwave imaging and wireless communication systems with low-cost fabrication and a stable performance.