Dielectric Sheet Perturbation to Metallic Air-Filled Cavity - Technique of Microwave Non-Destructive Testing (MNDT)

This paper focuses on the dielectric sheet perturbation to the dominant TE₁₁₁ mode resonant frequency of a circular cavity. Split-cylinder resonator method (Fang, et. al., 2004) is used to improve the non-destructive technique and gives accurate measurement for low permittivity materials at multiple frequency points. For fixed dimensions of cavity and different thickness of the dielectric materials which are placed in the middle of the air-filled cavity, it shows that the dominant resonant frequency varies with the permittivity of the samples. This relationship is verified and calculated using vector network analyzer and MAPLE software respectively. Eleven samples with different thickness have been measured and the results show that each sample has its own values of permittivity at a certain frequency. The results demonstrate that this project leads to the possibility of using the circular cavity with TE₁₁₁ mode resonant frequency as a microwave nondestructive testing for other different types of dielectric materials