Compact superconducting dual-log spiral resonator with high Q-factor and low power dependence

• Published in: IEEE transactions on applied superconductivity Vol. 12; no. 2; pp. 1813 - 1817
• Main Authors: Hejazi, Z.M., Excell, P.S.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.06.2002; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Applied sciences; Approximation; Circuit properties; COPPER OXIDE; CURRENT DENSITY; DENSITY; Electric, optical and optoelectronic circuits; Electronic circuits; Electronics; Exact sciences and technology; Frequency; Geometry; Insertion loss; Microstrip resonators; Microwave circuits, microwave integrated circuits, microwave transmission lines, submillimeter wave circuits; Oscillators, resonators, synthetizers; Q factor; Resonant frequencies; Resonators; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Spirals; Superconducting devices; Superconducting materials; SUPERCONDUCTIVITY; SUPERCONDUCTORS; THIN FILMS; Transistors; YBCO superconductors; Yttrium barium copper oxide; YTTRIUM OXIDE; Performance evaluation; Superconducting thin films; Spiral shape; Approximate method; High Q factor; Logarithmic function; Microstrip resonator; Experimental study; Superconducting microwave devices; Quaternary compound; Superconducting resonator; Barium oxide; Line width; Resonance frequency; Insertion loss; Yttrium oxide; Copper oxide; Low-power electronics; Current density; Comparative study; High temperature superconductor
• ISSN: 1051-8223; 1558-2515
• DOI: 10.1109/TASC.2002.1020342

A new dual-log spiral geometry is proposed for microstrip resonators, offering substantial advantages in performance and size reduction at subgigahertz frequencies when realized in superconducting materials. The spiral is logarithmic in line spacing and width such that the width of the spiral line increases smoothly with the increase of the current density, reaching its maximum where the current density is maximum (in its center for /spl lambda//2 resonators). Preliminary results of such a logarithmic ten-turn (2 /spl times/ 5 turns) spiral, realized with double-sided YBCO thin film, showed a Q.-factor seven times higher than that of a single ten-turn uniform spiral made of YBCO thin film and 64 times higher than a copper counterpart. The insertion loss of the YBCO dual log-spiral has a high degree of independence of the input power in comparison with a uniform Archimedian spiral, increasing by only 2.5% for a 30-dBm increase of the input power, compared with nearly 31% for the uniform spiral. A simple approximate method, developed for prediction of the resonant frequency of the new resonators, shows a good agreement with the test results.