无耦合交叉线高温超导准椭圆函数滤波器

High Temperature Superconducting Quasi-Elliptic Function Filter Without Cross-Coupled Line

提出了一种用于设计高温超导小型化准椭圆函数滤波器的新型多曲折谐振器结构,在不改变滤波器总体布局的情况下,通过优化谐振器结构来直接实现拓扑逻辑上非相邻谐振器之间的交叉耦合,引入多对传输零点以提高滤波器的带外抑制。既能利于实现滤波器的小型化,也能避免耦合交叉线对加工工艺的特殊要求。利用自拟耦合矩阵,在31.5 mm×15.6 mm,厚度为0.5 mm、介电常数为24的双面YBCO/La Al O3/YBCO高温超导薄膜上,设计制作了具有3对传输零点的12阶CDMA 2 000高温超导滤波器。在77 K时测得滤波器的中心频率为830 MHz,带宽为10 MHz,带边滚降大于45 d B/MHz,带内插入损耗最优值小于0.4 d B,回波损耗整体优于-11.3 d B,加工测试结果与仿真设计结果基本吻合。

This paper presents a group of improved multi-zigzag resonators to design high temperature superconducting （HTS） miniaturization quasi-elliptic filter. With a little change of the filter＇s layout, cross-couplings between non-adjacent resonators in topology logic are directly achieved without any cross-coupling line by optimizing the resonator＇s structure, and multi-pairs of transmission zeros are introduced to improve out-of-band rejection of filter, which are not only beneficial for filter＇s miniaturization, but also avoids the high processing-technical requirement caused by cross-line coupling. By using a self-synthesized coupling matrix, a 12th-order HTS filter is designed with 3 pairs of transmission zeros on a double-sided YBCO/LaAlO3/YBCO high temperature superconducting thin film whose size is 31.5 mm×15.6 mm, thickness is 0.5 mm, and dielectric constant is 24. At 77 K, the filter＇s tested center frequency is 830 MHz with a bandwidth of 10 MHz, a band edge roll-off more than 45 dB/MHz, a insert losing less than 0.4 dB and a return losing better than -11.3 dB.