Analysis of Flanged Rectangular Waveguide Probe for Nondestructive Absorbing Materials Characterization Using FDTD Simulation

Abstract

In this paper, the flanged open-ended rectangular waveguide probe technique is studied using Finite Difference Time-Domain simulation (FDTD). Both generally lossy and high loss electromagnetic materials are considered to investigate the influence of probe flange size, operating frequency and sample thickness on complex permittivity (er) and permeability (μr) and thickness measurement. Variations in the probe flange size for different frequencies, material under test type and thickness are simulated. It is found that using of waveguide probe with finite flange affects probe input reflection coefficient substantially in some cases. To verify the obtained simulations results, a series of experiments are conducted for this purpose. Both er and μr of material under test under different measurement conditions are extracted using FDTD modeling and compared with reference data. In order to evaluate the degree of accuracy of this technique, error analysis to various sources of errors and most importantly the effect of finite flange size are also demonstrated by using the measured data compared with the analytical model results. Simulations and measurements results have shown that the consideration of probe flange large enough for the practical purpose to be infinite is restricted by the constitutive parameters (er and μr) and operating frequency as well as the thickness of the material under test. The FDTD simulations and experiments results are presented.