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Publication Citation: A 4:1 transmission-line impedance transformer for broadband superconducting circuits

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Author(s): Leonardo M. Ranzani; Lafe F. Spietz; Jose A. Aumentado; Zoya Popovic;
Title: A 4:1 transmission-line impedance transformer for broadband superconducting circuits
Published: October 01, 2012
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.
Citation: IEEE Transactions on Applied Superconductivity
Volume: 22
Issue: 5
Pages: 6 pp.
Keywords: Superconducting microwave devices,impedance matching, transformers
Research Areas: Superconductivity, Ultrawideband
DOI: http://dx.doi.org/10.1109/TASC.2012.2202116  (Note: May link to a non-U.S. Government webpage)
PDF version: PDF Document Click here to retrieve PDF version of paper (738KB)