Superconducting Wideband Bandpass Filter Based on Triple-Mode Resonator

A high-temperature superconducting wideband bandpass filter based on a triple-mode resonator is developed in this letter. A novel triple-mode resonator, which can not only generate a wide passband at low frequency but also suppress the harmonic responses and obtain a wide stopband, is proposed. To further improve the selectivity, we load two stubs at the input and output ports to generate one transmission zero at the low passband. The simulation results show that the filter is centered at 1 GHz (f
_c
) with 111% 3-dB fractional bandwidth and has an upper stopband to 3.5f
_c
. The measured results show that the return loss is larger than 15 dB, and the insertion loss is less than 0.26 dB.