Dual-Band High-Temperature Superconducting Bandpass Filter Using Dual-Mode Hairpin Ring Resonator

A compact dual-band high-temperature superconducting (HTS) bandpass filter using a novel hairpin ring resonator (HRR) is presented in this paper. The proposed HRR that provides two controllable resonant modes can be applied to construct dual-band frequency response conveniently. The resonance mechanism of modes and coupling property between resonators are well investigated. Then, four identical HRRs are cascaded for achieving a high-performance dual-band filter. Finally, a fourth-order HTS filter centered at 1.9 and 2.6 GHz is successfully designed and fabricated on MgO substrate with YBCO thin films. The obtained filter has a compact size (occupies only 17.6 mm × 14 mm). The measured results show a high performance and agree well with the simulated ones.