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.

中文翻译：

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微波和毫米波频率范围内用于信号处理的液晶

液晶技术在可见光领域有着悠久的应用历史，主要用于显示行业。相反，较低频率的应用（通过红外线的微波）则不太常见。在本文中，我们研究了非显示应用，并回顾了液晶材料在微波和毫米波频率下用于可调谐信号处理设备的使用。这些设备包括可调移相器，滤波器（带通和带阻），天线和天线阵列，谐振器以及频率选择表面。我们还简要回顾了这些频率范围内液晶的典型特性。