Tunable Reflectarray Resonant Elements Based on Non-Linear Liquid Crystal Materials

Abstract

The operation of the radar technology is based on the mechanical movement of the antenna. To overcome the flaw of the mechanical movement an electronically tunable reflectarray antenna based on non-linear properties of Liquid Crystal materials has been introduced. This paper presents a detailed analysis of the tunability performance of different X-band reflectarray resonant elements printed on 1 mm thick grounded Liquid Crystal materials. Dynamic phase range and frequency tunabilty of rectangular, dipole and ring elements have been investigated by using CST computer model. Non-linear material properties have been used to develop an algorithm based on Method of Moment, for dynamic phase distribution of three resonant elements. It has been shown that the ring element offers a maximum dynamic phase range of 248° as compared to dipole and rectangular elements which offer 238° and 160° respectively. Moreover a maximum frequency tunabilty of 796 MHz, 784 MHz and 716 MHz can be achieved for rectangular, dipole and ring elements respectively with a dielectric anisotropy of 0.45. Waveguide simulator measurements of passive reflectarray unit cells demonstrate that rectangular element is observed to offer a minimum reflection loss of 1.6 dB as compared to dipole and ring elements which offer 3.3 dB and 3.6 dB respectively.