Electrical characterisation of liquid crystals at millimetre wavelengths using frequency selective surfaces

<br/><br/>Email<br/>Print<br/><br/> <br/><br/><br/><br/><br/><br/><br/><br/><br/><br/>The accurate measurement of the permittivity, loss tangent and dielectric anisotropy DC bias dependence for two different liquid crystal (LC) materials in the frequency range 140-165 GHz is described. The electrical characteristics are obtained by curve fitting computed transmission coefficients to the experimental spectral response of a new class of electronically reconfigurable frequency selective surface. The periodic structure is designed to yield bandpass filter characteristics with and without an applied bias control voltage in order to measure the tunability of the LC material which is inserted in a 705 µm-thick cavity.<br/>