Microstrip Patch Sensors for Complex Permittivity Measurement of Medium Loss Liquids Using 3D-FDTD

Two novel microstrip resonators are designed to measure the complex permittivity of medium loss liquids. These resonators have two layers, the first one is the sample layer and the second one is the base layer that the patch is printed on it. The base layer is suspended or inverted on the sample layer and the S-parameter is measured. The complex permittivity of the sample layer is extracted from the resonance frequency and the 3-dB bandwidth of the S-parameter. In this paper, binary mixtures of ethanol and methanol are used as sample layer. FDTD is a well-known computational method and is used for analyzing the structures. The experimental results for both of these resonators are really good and agree with reference values.