8-GHz Narrowband High-Temperature Superconducting Filter With High Selectivity and Flat Group Delay
8-GHz Narrowband High-Temperature Superconducting Filter With High Selectivity and Flat Group Delay
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DOI：
10.1109/tmtt.2009.2022813
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发表时间：
2009-06
影响因子：
4.3
通讯作者：
Lu Gao;Liang Sun;Fei Li;Qiang Zhang;Yuehui Wang;Tao Yu;Jin Guo;Y. Bian;Chunguang Li;Xueqiang Zhang;Hong Li;Jibao Meng;Yusheng He
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文献类型：
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作者：
Lu Gao;Liang Sun;Fei Li;Qiang Zhang;Yuehui Wang;Tao Yu;Jin Guo;Y. Bian;Chunguang Li;Xueqiang Zhang;Hong Li;Jibao Meng;Yusheng He
本文报道了一种具有高选择性和平坦群延迟的窄带高温超导滤波器的开发。该滤波器的中心频率为 8.625 GHz，3dB 带宽为 42 MHz（分数带宽为 0.49%）。为了同时实现高带边陡度和出色的群延迟平坦度，我们在级联四重态耦合结构中引入了具有三对传输零点（一对用于高选择性，两对用于平坦群延迟）的14谐振器准椭圆函数响应。我们还开发了一种新型低辐射谐振器（双折叠谐振器），以减少寄生耦合并满足 8 GHz 滤波器的其他要求。该滤光片是在直径为 2 英寸、厚度为 0.5 毫米的 MgO 晶片上制作而成，并带有双面 YBCO 薄膜。测量结果显示，中频插入损耗为 1.6 dB，回波损耗优于 15.5 dB。高频和低频边缘的带缘陡度均超过 11.7 dB/MHz。 60dB矩形比小于1.25。在 5.98 MHz 处，带外抑制距离 3 dB 频带边缘超过 70 dB。群延迟的变化在 33 MHz（3 dB 带宽的 78.5%）范围内小于 23 ns，在 34.5 MHz（3 dB 带宽的 82%）范围内小于 30 ns。
This paper reports a development of a narrowband high-temperature superconducting filter with both high selectivity and flat group delay. The filter has a center frequency of 8.625 GHz and a 3-dB bandwidth of 42 MHz (a fractional bandwidth of 0.49%). In order to achieve both high band-edge steepness and excellent group-delay flatness, we introduce a 14-resonator quasi-elliptic function response with three pairs of transmission zeros (one pair for high selectivity and two pairs for flat group delay) in the cascaded quadruplet coupling structure. We also develop a novel low radiation resonator (double-folded resonator) to reduce the parasitic coupling and meet other requirements for the 8-GHz filter. The filter was fabricated on a 2-in-diameter 0.5-mm-thick MgO wafer with double-sided YBCO films. The measured results show a midband insertion loss of 1.6 dB and a return loss better than 15.5 dB. Band-edge steepness reaches over 11.7 dB/MHz at both the high- and low-frequency edges. The 60-dB rectangle ratio is less than 1.25. The out-of-band rejection is over 70 dB at 5.98 MHz from the 3-dB band edge. The variation of group delay is less than 23 ns over 33 MHz (78.5% of 3-dB bandwidth), and less than 30 ns over 34.5 MHz (82% of 3-dB bandwidth).