Optimum Aperture Radius of R-Band Rectangular Resonator for Use in Electromagnetic Material Characterization

Yıl 2025, Cilt: 8 Sayı: 2 , 163 - 173 , 30.11.2025

Merve Durmuş , Alp Oral Salman

https://doi.org/10.34088/kojose.1642870

https://izlik.org/JA23UT65WZ

Öz

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.

Anahtar Kelimeler

Aperture excitation , Bethe’s aperture theory , Rectangular resonator , R-band , Q-factor , Electromagnetic material characterization.

Optimum Aperture Radius of R-Band Rectangular Resonator for Use in Electromagnetic Material Characterization

https://izlik.org/JA23UT65WZ

Öz

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.

Anahtar Kelimeler

Aperture excitation , Bethe’s aperture theory , Rectangular resonator , R-band , Q-factor , Electromagnetic material characterization

Etik Beyan

The authors of this article declare that the materials and methods used in this study do not require ethical committee permission and/or legal-special permission.

Kaynakça

• [1] Chen L.F., Ong C.K., Neo C.P., Varadan V.V., Varadan V.K., 2004. Microwave Electronics: Measurement and Materials Characterization, West Sussex: John Wiley & Sons, England.
• [2] Vinoy K.J., Jha R.M., 1996. Radar Absorbing Materials: From Theory to Design and Characterization, Boston: Kluwer Academic Publishers, USA.
• [3] Pozar D.M., 2012. Microwave Engineering, 4th ed. New Jersey: John Wiley & Sons Inc., USA.
• [4] Bethe H.A, 1944. Theory of Diffraction by Small Holes. Physics Review, 66, pp. 163-182.
• [5] Collin R.E., 1990. Field Theory of Guided Waves., 2nd ed., John Wiley & Sons Ltd., New York, USA.
• [6] Stratton J.A., 1941. Electromagnetic Theory. McGraw-Hill Book Co., New York, USA.
• [7] Montgomery C.G., 1948. Principles of Microwave Circuits, McGraw-Hill Book Co. Inc., New York, USA.
• [8] Marcuvitz N., 1951. Waveguide Handbook., McGraw-Hill Book Co. Inc., New York, USA.
• [9] McDonald N.A., 1972. Electric and Magnetic Coupling through Small Apertures in Shield Walls of any Thickness. IEEE Transactions on Microwave Theory and Techniques, 20, pp. 689-695.
• [10] McDonald N.A., 1985. Polynomial Approximations for the Electric Polarizabilities of Some Small Apertures. IEEE Transactions on Microwave Theory and Techniques, 33, pp.1146-1149.
• [11] Wheeler H.A., 1964. Coupling Holes Between Resonant Cavities or Waveguides Evaluated in Terms of Volume Ratios. IEEE Transactions on Microwave Theory and Technique, 12, pp. 231-244.
• [12] Kajfez D., Chebolu S., Abdul-Gaffoor M.R., Kishk A.A., 1999. Uncertainty Analysis of the Transmission Type Measurement of Q-Factor. IEEE Transactions on Microwave Theory and Techniques, 47, pp. 367-371.
• [13] Kajfez D., Hwan E.J., 1984. Q Factor Measurements with Network Analyzer. IEEE Transactions on Microwave Theory and Techniques, 32, pp.666-670.
• [14] Kajfez D., 1995. Q Factor Measurements with Scalar Network Analyzer. IEE Proc.-Microw. Antennas Propag., 142, pp. 369-372.
• [15] Sucher M., Fox J., 1963. Handbook of Microwave Measurements, 3rd ed., John Wiley and Sons, West Sussex, England.
• [16] Salman A.O., Alper F. 2023, R-Bant Boşluk Rezonatörü ile Bazı Mikrodalga Malzemelerinin Karmaşık Dielektrik ve Manyetik Geçirgenliklerinin Belirlenmesi. Kocaeli Üniversitesi Fen Bilimleri Dergisi, 6, pp. 27-35.
• [17] Durmuş M., 2018. R-Bant Dikdörtgen Boşluk Rezonatörü için Uygun Uyarım Açıklık Yarıçapının Bulunması. M.Sc. Thesis. Kocaeli Universitesi Fen Bilimleri Enstitüsü.