RESONANCE PROPERTIES OF AN X-BAND RECTANGULAR WAVEGUIDE SECTION WITH AN INHOMOGENEOUS DIELECTRIC INSET

Abstract

Subject and Purpose. In modern dielectrometry, the problem of detecting foreign inclusions in a radio-transparent material, which are significantly smaller than the operational wavelength, remains very important. The problem becomes even more complicated if it is required to determine complex permittivity of these inclusions. This work analyzes the conditions for the correct use of the original resonance method proposed by the authors earlier for determining permittivity of a local inclusion when its dimensions and dielectric constant change. Methods and Methodology. The measured module consists of a rectangular X-band waveguide, which is partially filled with a dielectric in the form of a rectangular Teflon matrix with a local cubic inclusion inside. The dimensions of the matrix are fixed and are 23 mm × 10 mm × 30 mm. Numerical modeling is performed using the Ansys HFSS software package. The dependences of the resonance frequencies of the module upon changing the dielectric constant of the cube are analyzed. The cube permittivity was changed between 3.8 and 100 in 5-unit steps. Permittivity of the material of the cube is determined by comparing arrays of calculated data with experimental results. Results. Numerical modeling of the module was performed and its electrodynamics properties were determined in the frequency band of 8…10 GHz at different sizes and permittivity of the inclusion. For a cube with a facet size of 2 mm, the resonance frequency decreases with a permittivity increase of the material. For a cube with a facet size of 3 mm and permittivity above 50, additional resonances appear in the structure due to the excitation of resonant modes of the cube itself. Conclusion. It has been shown that by varying the dielectric permittivity of the cubic inset between 3.8 and 100 it proves possible to provide for resonant mode excitation over the frequency range specified. This allows estimating the dielectric permittivity of the cubic inset’s material by way of comparing the calculated versus measured data arrays concerning resonant frequency dependences upon material parameters.