Dual-Band High-Temperature Superconducting Hairpin-Resonator Bandpass Filter Based on Two Pairs of Nondegenerate Modes

In this letter, a compact dual-band high-temperature superconducting (HTS) hairpin-resonator bandpass filter based on a multimode resonator is proposed. This multimode resonator consists of two hairpin resonators loaded with a common T-shaped stub. The T-shaped stub excites one pair of nondegenerate modes for the inner hairpin resonator, whereas the combination of T-shaped stub and the inner hairpin resonator produces another pair of nondegenerate modes for the outer hairpin resonator. Moreover, the former generates the higher passband, and the latter produces the lower passband, which is controlled independently by the corresponding hairpin resonator. Finally, the proposed dual-band HTS filter was fabricated and measured. Good agreement between simulation and measurement verifies the validity of this design methodology.