Miniaturized High-Temperature Superconductor Bandpass Filters Using Microstrip S-Type Spiral Resonators

Zhewang MA
Tamio KAWAGUCHI
Yoshio KOBAYASHI

Publication
IEICE TRANSACTIONS on Electronics   Vol.E88-C    No.1    pp.57-61
Publication Date: 2005/01/01
Online ISSN: 
DOI: 10.1093/ietele/e88-c.1.57
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Recent Trends of Microwave and Millimeter-Wave Passive Circuit Components and Technologies for Improvement of Characteristics)
Category: 
Keyword: 
high-temperature superconductor,  microstrip spiral resonator,  bandpass filter,  

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Summary: 
At frequencies currently used by mobile communications, many of the microstrip half-wavelength resonators are too large to realize miniaturized filters. For this reason, very small-sized microstrip spiral resonators and filters, using high-temperature superconductors (HTS), have been studied recently. In this paper, the resonant and coupling characteristics of microstrip G-type and S-type spiral resonators are investigated first by using an electromagnetic simulator. Then small-sized 4-pole, 8-pole, and 16-pole Chebyshev bandpass filters using S-type spirals are designed, respectively, with a midband frequency f0 = 1.93 GHz. The frequency responses of the filters satisfy well the desired specifications, and the measured frequency response of the 8-pole HTS filter agrees well with the theoretical prediction.