Measurement of Dielectric Constants of Nematic Liquid Crystals at mm-Wave Frequencies Using Patch Resonator

A new technique for the measurement of dielectric constants of nematic liquid-crystal (LC) materials at millimeter-wave frequencies is presented. The proposed method utilizes an electric field to align the LC molecules, therefore offering safety and enormous size reduction over the method using the magnetic field to achieve LC directors´ orientation. The measurement device is planar and consists of a rectangular patch resonator with the LC cell directly beneath it. Two preconditioned surface preparations, corresponding to transverse and longitudinal rubbing of the patch surface and ground plane in contact with LC, are investigated. Using the same measurement device with the two preconditioned surfaces, the measurements of dielectric constants and dielectric constant anisotropy of a nematic LC commonly known as E7 are conducted, and the results are found to agree to within 1% while confirming earlier published data.