A single-stage ring resonator capable of introducing six modes within the ultra-wideband (UWB) passband is presented. The sextuple-mode resonator consists of three rings and three sets of stepped-impedance open stubs. Based on this sextuple-mode resonator, a UWB filter fed by the interdigital-coupling line (ICL) is designed. And we propose a two-round interpolation method to obtain the filter’s initial dimensions. The designed filter is fabricated on a double-sided YBCO/MgO/YBCO high-temperature superconducting (HTS) thin film for demonstration. The experimental results show that this UWB filter produces eight resonances in the passband eventually, which effectively improves the in-band reflection and the band-edge steepness. Moreover, the upper stopband performance is enhanced due to the transmission zeros (TZs) generated by the stepped-impedance open stubs and the ICL structure. The measured good performance verifies the practicability of the two-round interpolation approach, which can also be extended to other odd–even-mode filter designs.

提出了一种能够在超宽带 (UWB) 通带内引入六种模式的单级环形谐振器。六重模式谐振器由三个环和三组阶梯阻抗开路短截线组成。基于这种六模谐振器，设计了一种由叉指耦合线（ICL）馈电的超宽带滤波器。我们提出了一种两轮插值方法​​来获得滤波器的初始尺寸。设计的滤波器是在双面 YBCO/MgO/YBCO 高温超导 (HTS) 薄膜上制造的，用于演示。实验结果表明，该UWB滤波器最终在通带内产生8个谐振，有效改善了带内反射和带边陡度。而且，由于阶梯阻抗开路短截线和 ICL 结构产生的传输零点 (TZ)，因此提高了上阻带性能。测量的良好性能验证了两轮插值方法​​的实用性，该方法也可以扩展到其他奇偶模式滤波器设计。