Optimizing Superconducting Matching Circuits for Nb SIS Mixers Operating Around the Gap Frequency
Optimizing Superconducting Matching Circuits for Nb SIS Mixers Operating Around the Gap Frequency
复制标题
优化在间隙频率附近运行的 Nb SIS 混频器的超导匹配电路
DOI：
10.1109/tasc.2007.897336
复制
发表时间：
2007
影响因子：
1.8
通讯作者：
T. M. Klapwijk
中科院分区：
文献类型：
--
作者：
C. Lodewijk;O. Noroozian;D. Loudkov;T. Zijlstra;A. Baryshev;F. P. Mena;T. M. Klapwijk
The bandwidth and noise temperature of superconducting-insulating-superconducting (SIS) mixers are strongly determined by the matching between antenna and tunnel-junction. Optimal scientific benefit from Band 9 (600 to 720 GHz) of the Atacama large millimeter array requires a proper design of the matching circuit by taking into account the energy gap of the niobium (680 GHz). In preliminary experiments we have found that tapered structures lead to significant improvements, which suggests that a systematic analysis of optimized geometrical shapes might be beneficial. The tuning circuits are analysed using a model, which includes the Mattis-Bardeen theory for the surface impedance of Nb and which allows arbitrary shapes. We will present simulations and experimental results focusing on the transmission efficiency, which can conveniently be evaluated experimentally by using a Fourier transform spectrometer. We will show how the shape influences the transmission efficiency and relate it to observed noise temperatures of the mixers.
