Title :
A 4 : 1 Transmission-Line Impedance Transformer for Broadband Superconducting Circuits
Author :
Ranzani, Leonardo ; Spietz, L. ; Popovic, Zoya ; Aumentado, J.
Author_Institution :
Dept. of Electr. & Comput. Eng., Univ. of Colorado, Boulder, CO, USA
Abstract :
We present a 4 : 1 superconducting transmission-line impedance transformer for cryogenic applications. The device transforms 25 Ω in the coplanar waveguide to 6.25 Ω in the microstrip and is designed to operate at 20 mK. Calibrated measurements in a dilution refrigerator demonstrate a -3 dB bandwidth from 1.6 to 13 GHz. In a modified Ruthroff design, a small capacitor is integrated at the input as a direct-current block, making it suitable for biasing and matching to low-impedance active circuits, such as superconducting quantum interference device (SQUID) amplifiers.
Keywords :
coplanar waveguides; cryogenic electronics; impedance convertors; impedance matching; superconducting transmission lines; SQUID amplifiers; bandwidth 1.6 GHz to 13 GHz; broadband superconducting circuits; coplanar waveguide; cryogenic applications; dilution refrigerator; direct-current block; impedance biasing; impedance matching; low-impedance active circuits; measurements calibration; modified Ruthroff design; resistance 25 ohm; resistance 6.25 ohm; superconducting quantum interference device amplifiers; superconducting transmission-line impedance transformer; temperature 20 mK; Bandwidth; Capacitors; Coplanar waveguides; Impedance; Niobium; SQUIDs; Superconducting microwave devices; Impedance matching; superconducting microwave devices; transformers;
Journal_Title :
Applied Superconductivity, IEEE Transactions on
DOI :
10.1109/TASC.2012.2202116
