鐵氧體(Ferrite)之磁導率並非一個常數型式，其受飽和磁化量、直流外加磁場及操作頻率影響，因此我們欲透過給予不同的外加磁場來調控張量型式的磁導率，而不同的磁導率會改變電磁波的傳播特性。若阻抗匹配則電磁波可以全部穿透，反而言之，若阻抗不匹配則電磁波全反射。我們提出了一個帶有環型鐵氧體的同軸結構，其可作用在大約2.45 GHz的頻率下，藉由簡單地調整外加磁場，讓入射波可以完全通過或完全反射，如此一來，此同軸鐵氧體的結構可當作一種開關器裝置，由模擬軟體得知此開開器的開與關狀態轉換需要44高斯的磁場大小。在實體設計上，此開關器包含了鐵氧體、紅銅、鐵氟龍、鋁以及N型接頭，透過網路分析儀(VNA)量測此開關器之效果，並利用高斯計量測開與關狀態轉換之磁場大小約為62高斯，亦由逆向工程之方法將此開關器的工作機制以數學式描述，初步的分析其物理意義，對未來設計其他頻段之開關器提供了基礎理論。最後，將此快速開關器推廣至不同鐵氧體的材料特性、結構設計的改變，不同條件下，模擬與量測結果的討論。

The permeability of ferrite is a second rank tensor, depending on the saturation magnetization, the dc bias magnetic field, and the operating frequency. By adjusting the applied bias magnetic field, the permeability tensor can be manipulated which may change the propagating properties of the wave. Here we proposed a coaxial structure with a toroidal ferrite. At frequency around 2.45 GHz, the incident wave can totally transmit or totally reflect by simply adjusting the bias magnetic field. The coaxial-ferrite structure can serve as a switch. The difference of the magnetic bias is just 44 Gauss for the transparent state and the opaque state by simulation. The switch is developed by ferrite, copper, teflon, aluminum and N-type connectors. Actually, this device can switch on or off by adjusting 62 Gauss magnetic bias. It facilitates a high-speed, high-power, and compact switch. The theoretical analysis is derived and the underlying physics is explained, which provide a solid ground for designing similar switches at other frequency bands.

[1]David M. Pozar, Microwave Engineering, 3rd ed. (Addison-Wesley,Massachusetts, 2005), Chap. 9.
[2]E. P. Wohlfarth, Ferromagnetic materials: a handbook on the properties of magnetically ordered substances. (Elsevier, North-Holland, 1980) vol. 2.
[3]T. H. Chang, “Gyromagnetically-induced transparency for ferrites,” Am. J. Phys., vol. 84, no. 4, pp. 279-283, Apr. 2016.
[4]John D. Jackson, Classical Electrodynamics, 3rd ed. (Wiley, New York, 1998), Chap. 7.
[5]C. H. Tsai, “Characterizing the Complex Permittivity and Permeability with a Dual Cavity System,” M.S. thesis, National Tsing Hua University, 2017.
[6] Robert E. Collin, Foundations for Microwave Engineering, 2nd ed. (McGraw Hill, New York, 1992), Chap. 6.
[7] R. K. Wangsness, “Ferrimagnetic resonance and some related effects,” Am. J. Phys., vol. 24, pp. 60–66 , 1956.
[8]A. Parsa, T. Kodera, and C. Caloz, “Ferrite based non-reciprocal radome, generalized scattering matrix analysis and experimental demonstration,” IEEE Trans. Antennas Propag., vol. 59, no.3, pp. 810–817, Dec. 2011.
[9]M. Pardavi-Horvath, “Microwave applications of soft ferrites,” J. Magn. Magn. Mater., vol. 215, pp. 171-183, Jun. 2000.
[10]T. Kodera, D. L. Sounas and C. Caloz, “Magnetless nonreciprocal metamaterial (MNM) technology: application to microwave components,” IEEE Trans. Microw. Theory Tech., vol. 61, pp. 1030-1042, Mar. 2013.
[11]C. Goldsmith, T. H. Lin, B. Powers, W. R. Wu, B. Norvell, “Micromechanical membrane switches for microwave applications,” IEEE MTT-S Int. Microwave Symp., vol. 1, pp. 91-94, 1995.
[12]V. G. Harris, A. Geiler, Y. Chen, S. D. Yoon, M. Wu, A. Yang, Z. Chen,P. He, P. V. Parimi, X. Zuo, C. E. Patton, M. Abe, O. Acher, and C.Vittoria, “Recent advances in processing and applications of microwave ferrites,” J. Magn. Magn. Mater., vol. 321, pp. 2035– 2047, July 2009.
[13]J. D. Adam, L. E. Davis, G. F. Dionne, E. F. Schloemann, and S. N. Stitzer, “Ferrite devices and materials,” IEEE Trans. Microw. Theory Tech., vol. 50, pp. 721–737, Mar. 2002.
[14]V. A. Dmitriyev, “Symmetry of microwave devices with gyrotropic media-complete solution and applications,” IEEE Trans. Microw. Theory Tech., vol. 45, no. 3, pp. 394–401, Mar. 1997.
[15]J. R. Truedson, K. D. McKinstry, R. Karim, and C. E. Patton, “Effective linewidth due to conductivity losses in barium ferrite,” IEEE Trans. Magn., vol. 28, no. 5, pp. 3309–3311,Sept. 1992.
[16]D. Polder and J. Smit, “Resonance phenomena in ferrites,” Rev. Mod. Phys., vol. 25, pp. 89–90, Jan. 1953.
[17]J. R. Truedson, K. D. McKinstry, R. Karim, and C. E. Patton, “Effective linewidth due to conductivity losses in barium ferrite,” IEEE Trans. Magn., vol. 28, no. 5, pp. 3309–3311, Sept. 1992.
[18]M. M. Abusitta, D. Zhou, R. A. Abd-Alhameed, and P. S. Excell, “Design of controlled RF switch for beam steering antenna array,” PIERS Online., vol. 4, no. 3, pp. 356-360, 2008.
[19]M.-S. Lee and Y.-H. Kim, “Design and performance of a 24-GHz switch-antenna array FMCW radar system for automotive applications,” IEEE Trans. Veh. Technol., vol. 59, no. 5, pp. 2290–2297, Jun. 2010.
[20]N. A. Riza, “High-speed high-isolation 2 × 2 fiber-optic switch for wideband radar photonic beamforming controls,” J. Lightw. Technol., vol. 26, no. 15, pp. 2500–2505, July 2008.
[21]B. Kuanr, I. R. Harward, D. L. Marvin, T. Fal, R. E. Camley, D. L.Mills, and Z. Celinski, “High-frequency signal processing using ferromagnetic metals,” IEEE Trans. Magn., vol. 41, no. 10, pp. 3538–3543, Oct. 2005.