Broad band electromagnetic characterization method of nematic liquid crystals using a coplanar waveguide

Abstract

A broad band electromagnetic extraction method of the dielectric tensor for nematic liquid crystals, associated to a measuring cell, is presented. The dielectric tensor is computed from S-parameter measurements obtained at the input planes of a coplanar waveguide supporting the nematic liquid crystal to be characterized, which is used as measuring cell. The extraction method of the dielectric tensor is based on the propagation of the dominant mode in the measuring cell. It is fast and easy. It uses analytical relationships, which are presented in this paper. The simulations results have demonstrated the validity of this extraction method in the 1GHz-40GHz frequency range for the electromagnetic characterization of nematic liquid crystals.

Dual-Band Uniaxial Dielectric Anisotropy Sensor Using Coupled-Line Resonators

“…As mentioned before, there is a correspondence between the resonance frequencies of the resonators and the effective dielectric constant of the sensor. Assuming first an isotropic sample, the dielectric constant of the SUT can be established as the qualitative equation in (6), in which ε SUT is the dielectric constant of the isotropic sample, A is a proportionality constant, and f r is the resonance frequency of the sensor [11].…”

“…On the other hand, nonresonant methods are capable of measuring the anisotropy in a wide frequency range, but they are not as accurate and sensitive as resonance-based sensors [3]. Nonresonant methods, including transmission and reflection methods, use the impedance and the propagation constant of a transmission line to determine the dielectric constant components [4], [5], [6]. These sensors are mainly used to get a general knowledge of the sample characteristics and accurate properties at distinct frequencies are extracted using resonant methods [7].…”