Technology of liquid crystal based antenna [Invited]

This article is to summarize the development of technology of the liquid crystal based antenna. Two major trends of such antennas are discussed. One is the electronically steered phased array, and the other is the antenna based on the metamaterials concept. The major function of liquid crystal in a phased-array antenna is obviously to adjust the phase of electromagnetic waves. Hence different kinds of phase shifters made of liquid crystal are talked over in this article. As for the metamaterial or metasurface based antenna, the liquid crystal is used to adjust the refractive index of the surroundings of the highly dense antenna elements to further determine if they resonate or not. Other than the liquid crystal based microwave devices, the development of liquid crystal itself is of great importance. The very heart of all the devices mentioned above shall be the characteristics of liquid crystal at microwave range. The material development is summarized as well.