Rectangular Waveguide-Based Liquid Dielectric Characterization: A Novel Microwave Measurement Method

This paper presents a novel characterization technique for estimating the relative permittivity of a liquid dielectric material placed in a short-circuited rectangular WR90 waveguide. This technique uses the two-dimensional finite difference time domain (FDTD) method to calculate the relative permittivity based on the displacement of the first electric field node in the waveguide as measured by the MWT530 device. The results for distilled water and paraffin oil at 10.425 GHz in the X band show good agreement with those obtained using the High Frequency Structure Simulator (HFSS) for the same materials. Compared to existing methods, this technique is simpler, faster, and more accurate for material characterization. It does not require sophisticated measurement equipment or extensive theoretical knowledge. This makes it particularly suitable for classroom teaching.