Compact high-selectivity high-temperature superconducting wideband bandpass filter using triple-mode stub-loaded loop resonator

摘要

A triangle triple-mode stub-loaded loop resonator (SLLR) is proposed in thisletter and used for wideband filter design. Also, this SLLR can produce multipletransmission zeros for high-selectivity bandpass filter (BPF) design withoutadding extra circuit unit. To verify the unique characteristics of the proposedSLLR, a compact wideband BPF is designed and fabricated using hightemperaturesuperconducting YBCO thin films on a MgO substrate. Furthermore,a novel meander structure is introduced to realize compact size andstrong input/output coupling design. The measured results show that the 3-dBfractional bandwidth is of 50.6% (2.55-4.28 GHz), and the selectivity factor ofthe passband is 0.87 with a maximum insertion loss of 0.07 dB, indicating goodagreement with the theoretical expectation.