Liquid crystals for signal processing applications in the microwave and millimeter wave frequency ranges

Abstract

Liquid crystal technology has a long well-established history of applications in visible light, primarily in the display industry. In contrast, applications at lower frequencies (microwave through infrared) are less common. In this paper, we examine non-display applications and review the use of liquid crystal materials for tunable signal processing devices operating at microwave and millimeter wave frequencies. These devices include tunable phase shifters, filters (bandpass and bandstop), antennas and antenna arrays, resonators, and frequency selective surfaces. We also give a short review of the typical characteristics of liquid crystals in these frequency ranges.