X Band Test Bench Developement Requiring High Voltage Bias for Electronic Tunable Devices Using Anisotropic Materials

In this paper, we present complete operating bench experiments used to characterize a type of tunable devices in the microwave domain. This type of tunable devices requires unusual high AC/DC bias voltage (up to 400V). The experimental characterization system is based on the reflection and transmission parameters of a quadrupole placed between the two ports of a network analyzer, in the 8-12 GHz range. For the dielectric characterizations of materials, it is possible to determine the real part (’) and the imaginary part (’’) of the dielectric constant ( of the material. For tunable devices using polymer dispersed liquid crystals, it is necessary to apply a high electric driving field (up to 4V/µm @1 kHz). In the test bench, we used a microstrip phase shifter which presents a 100µm-thick active part. Therefore a 400V external voltage bias device was developed. We first present an applicative circuit, that is, a phase shifter, which is machined to study the electronic behaviors of anisotropic materials. We then present the design and characteristics of the bias circuit. Secondly, we present experimental results for two Polymer Dispersed Liquid Crystals made with two different monomers (NOA65-Norland, and PolyPropylene Glycol Di Acrylate540), with a commercial liquid crystal (5CB-Merck).