Superconducting dual-band filters

Several compact and high-performance HTS dual-band BPF based on multi-mode resonators have been reviewed in this chapter. Firstly a series of novel and compact dual-mode or quadruple-mode resonators are presented for constituting the loworder dual-band filters with the electrically small size and ultra-low insertion loss. Then, a novel dual-mode HRR is demonstrated and developed to an eighth-order HTS dual-band filter with sharp passband slope and deep out of band attenuation. In light of the development of more flexible resonant structures and efficient design theory, more compact and high-performance HTS dual-band, even the triple-band or quad-band filter can be designed in the future so as to meet the requirement for the high-quality service of various multi-functional wireless system.