Tunable liquid crystal double-layer frequency selective surface with wide transmission band and small insertion loss

Abstract

ABSTRACT In this paper, a tunable Frequency Selective Surface (FSS) based on liquid crystal (LC) with a wide transmission band, large tuning range, high tuning rate, and miniaturization is designed. First, a single-layer FSS is developed with two frequency selective layers and one LC tunable layer. The simulation and experiment results show that the single-layer FSS has a transmission bandwidth greater than 4.25 GHz, and the LC change can make the center frequency of the transmitted band shift to the lower frequency by 576 MHz, with a tuning rate of 4.2%. Subsequently, a double-layer FSS is designed by adding a coupling layer to the single-layer FSS, achieving a flat-top passband and enhancing the tuning rate. Simulation and experimental validation show that altering the LC state enables continuous tuning of the center frequency of the double-layer FSS from 14.95 GHz to 13.86 GHz, with a tuning rate of 7.2%. This structure exhibits a flat-top passband wider than 5.7 GHz, a relative bandwidth of 41%, and a rectangular coefficient below 1.877. Moreover, the double-layer FSS demonstrates favorable polarization stabilization and wide incidence angle stabilisation properties in various states.