A three-layer microstrip resonator for complex permittivity measurement of medium loss liquids using 3D-FDTD simulation

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.