A Three-Layer Microstrip Resonator for Complex Permittivity Measurement of Medium Loss Liquids Using 3D-FDTD Simulation

Cyrus Avaznia; Gholamreza Moradi

doi:10.52763/PJSIR.PHYS.SCI.60.2.2017.85.89

Cyrus Avaznia Department of Electrical Engineering, Amirkabir University of Technology, Tehran-15914, Iran
Gholamreza Moradi Wave Propagation and Microwave Measurement Research Laboratory, Department of Electrical Engineering, Amirkabir University of Technology, Tehran-15914, Iran

DOI: https://doi.org/10.52763/PJSIR.PHYS.SCI.60.2.2017.85.89

Keywords: microstrip resonator, microwave chemistry, complex permittivity measurement, 3D-FDTD

Abstract

A three-layer microstrip resonator is introduced to measure complex permittivities of medium
loss liquids. The device is configured such that the first layer containing the liquid under test; a sheet of
polytetrafluoroethylene (PTFE) is embedded in the middle layer, and the third layer functions as the base
on which the patch is printed. The base layer is inverted on PTFE layer, and reflection coefficient is
measured from 2.5 GHz to 5 GHz. The complex permittivities are extracted from the resonant frequency
and the 10-dB bandwidth of S-parameter for different combinations of ethanol and methanol. Indeed,
a three-layer microstrip resonator allows us to possess an affordable, and yet, high-accuracy electrical
device to measure complex permittivities of medium loss liquids. FDTD method is used for analysing
the structure and the results obtained by using FDTD method and the experimental data indicate a high
degree of similarity.