An Ultracompact Superconducting Bandpass Filter at 40 MHz Using Spiral Resonators and a New Feedline Structure
An Ultracompact Superconducting Bandpass Filter at 40 MHz Using Spiral Resonators and a New Feedline Structure
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DOI：
10.1109/tasc.2012.2187648
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发表时间：
2012-03
影响因子：
1.8
通讯作者：
Ying Zhang;Xubo Guo;B. Cao;B. Wei;Xiaoping Zhang;Xiaoke Song;Guannan Suo;Guoyong Zhang
中科院分区：
文献类型：
--
作者：
Ying Zhang;Xubo Guo;B. Cao;B. Wei;Xiaoping Zhang;Xiaoke Song;Guannan Suo;Guoyong Zhang
本文介绍了一种在LaAlO_3衬底上实现的40 MHz带宽为0.5 MHz的超导滤波器。它的尺寸为40 mm×19 mm，仅相当于0.02λG0×0.01λG0，其中λG0是基片上50-Ω线在中带频率的导波波长。分析了谐振器结构对展开长度的影响，进而分析了谐振器尺寸的影响。具有正互感的螺旋谐振器可以大大减小谐振器的展开长度，并用于实现滤波器的小型化。为了实现强外耦合，提出了螺旋腔内螺旋馈线结构。此外，在六极点滤波器中增加了一条交叉耦合线，以改善带边陡度。成功地设计并制作了滤光片。测试结果表明，该功放的插入损耗为0.3分贝，回波损耗为-19.2分贝，带外抑制为80分贝，边沿陡峭，与电磁模拟结果吻合较好。
This paper presents a superconducting filter with a bandwidth of 0.5 MHz at 40 MHz on a LaAlO3 substrate. It has a compact size of 40 mm × 19 mm, which amounts to only 0.02 λg0 × 0.01 λg0, where λg0 is the guided wavelength of the 50-Ω line on the substrate at the midband frequency. The effect of the resonator structure on the unwound length and, hence, the size of the resonator is analyzed. A spiral resonator with positive mutual inductances between adjacent microstrip turns can greatly reduce the resonator's unwound length and is used to miniaturize the filter size. A feedline structure spiraled inside the spiral resonator is proposed to realize a strong external coupling. Furthermore, a cross-coupling line is added to the six-pole filter to improve the band-edge steepness. The filter is successfully designed and fabricated. The measured results demonstrate a 0.3-dB insertion loss, a -19.2 dB return loss, an 80-dB out-of-band rejection, and steep band edges, which are in good agreement with electromagnetic simulations.