Research Progress of High Temperature Superconducting Filters in China

Recent developments in China for the design and application of high temperature superconducting (HTS) filters are reviewed. Progress in fabrication of HTS thin films with various physical and chemical methods are introduced first, since high quality double-sided thin films provide the groundwork for filters. In the past decade, hundreds of HTS filters have been designed in China with excellent performance, e.g., 0.05 dB minimum insertion loss,
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23 dB return loss,
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110 dB out-of-band rejection and 220 dB/MHz band-edge slope, etc. Novel design methods, i.e., coupling matrix extracting method, bandpass filters with wide stop band, linear phase filters, multiplexers, multi-band and multi-mode filters as well as tunable filters will be discussed in detail. Applications to mobile communication base stations, meteorological radar, deep space detection and satellite technology will be also reviewed.