The most critical part of a resonator design for electromagnetic material characterization is determining the optimum excitation aperture radius of the resonator. 11 pairs of galvanized iron plates with apertures of various radii ranging from 3 mm to 13 mm, increasing in average radial steps of 1 mm, were fabricated for use as the excitation walls of the resonator. In measurements, each pair of plates with an aperture hole was attached between two waveguide adapters and a waveguide section. Then, S-parameters were measured using a network analyzer. CST simulations for each case were also performed. The nature of the excitation (under, critical, and over couplings) was discussed from the measured and simulated results. The quality factor values were calculated using S_21 resonance curves obtained from both the measurements and the simulations for each radius. The optimum excitation aperture radius value for the R-band resonator was found to be approximately 7 mm for the chosen resonator dimensions. For this value of aperture, a maximum loaded quality factor was obtained and the resonator was critically coupled. For validation, theoretical radius values were also calculated and compared with the measured and simulated ones.
The most critical part of a resonator design for electromagnetic material characterization is determining the optimum excitation aperture radius of the resonator. 11 pairs of galvanized iron plates with apertures of various radii ranging from 3 mm to 13 mm, increasing in average radial steps of 1 mm, were fabricated for use as the excitation walls of the resonator. In measurements, each pair of plates with an aperture hole was attached between two waveguide adapters and a waveguide section. Then, S-parameters were measured using a network analyser. CST simulations for each case were also performed and compared with the measured ones which is not seen frequently in literature for a resonance structure. The nature of the excitation (under, critical, and over couplings) was discussed from the measured and simulated results. The quality factor values were calculated using S_21 resonance curves obtained from both the measurements and the simulations for each radius. The optimum excitation aperture radius value for the R-band resonator was found to be approximately 7 mm for the chosen resonator dimensions. For this value of aperture, a maximum loaded quality factor was obtained, and the resonator was critically coupled. For validation, theoretical radius values were also calculated and compared with the measured and simulated ones. This is a reliable and new method for showing that the obtained values are consistent.