Attenuation in Superconducting Rectangular Waveguides

• Published in: Frequenz Vol. 69; no. 3; pp. 111 - 117
• Main Authors: Yeap, Kim Ho, Mei Teh, Joyce Shu, Nisar, Humaira, Yeong, Kee Choon, Hirasawa, Kazuhiro
• Format: Journal Article
• Language: English
• Published: Berlin De Gruyter 01.03.2015; Walter de Gruyter GmbH
• Subjects: attenuation; complex conductivity; Constants; Critical temperature; cutoff frequency; Electrical engineering; gap frequency; Mathematical analysis; Propagation; propagation constant; Rectangular waveguides; superconducting waveguide; Superconductivity; Walls; Wave attenuation; Waveguides
• ISSN: 0016-1136; 2191-6349
• DOI: 10.1515/freq-2014-0078

We present an accurate analysis on the attenuation of waves, propagating in rectangular waveguides with superconducting walls. The wavenumbers and in the and directions, respectively, are first obtained as roots of a set of transcendental equations developed by matching the tangential fields at the surface of the wall with the electrical properties of the wall material. The complex conductivity of the superconducting waveguide is obtained from the extended Mattis–Bardeen theory. The propagation constant is found by substituting the values of and into the dispersion relation. We have computed and compared the loss in the waveguides below and above the critical temperature. At frequencies above the cutoff frequency but below the gap frequency , the loss in the superconducting waveguide is significantly lower than that in a normal conducting waveguide. Above the gap frequency, however, the result indicates that the attenuation in the waveguide below the critical temperature is higher than that at room temperature. We attribute the higher loss as due to the higher surface resistance and field penetration for superconducting waveguides operating above the gap frequency.