Radio frequency bias current scheme for dc superconducting quantum interference device

• Published in: IEEE transactions on applied superconductivity Vol. 9; no. 2; pp. 3813 - 3816
• Main Authors: Zhang, Y., He, D.F., Wolters, N., Otto, R., Barthels, K., Zeng, X.H., Yi, H.R., Krause, H.-J., Braginski, A.I., Faley, M.J.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: New York, NY IEEE 01.06.1999; Institute of Electrical and Electronics Engineers
• Subjects: Applied sciences; Bias; Circuit noise; Circuit properties; Direct current; Distributed parameter circuits; Electric, optical and optoelectronic circuits; Electronics; Exact sciences and technology; Flux; Microwave circuits, microwave integrated circuits, microwave transmission lines, submillimeter wave circuits; Noise; Radio frequencies; Radio frequency; Radiofrequency interference; Readout electronics; Resonance; SQUIDs; Superconducting device noise; Superconducting devices; Superconducting quantum interference devices; Superconducting transmission lines; Transmission lines; Amplitude frequency characteristic; Transmission line; Circuit design; Superconducting quantum interferometer device; Bandwidth; Matching circuit; Resonant circuit; 1/f noise; Radiofrequency; High temperature superconductor; Bias current
• ISSN: 1051-8223; 1558-2515
• DOI: 10.1109/77.783858

We have developed a radio frequency bias current scheme with reversal frequency up to 50 MHz for dc superconducting quantum interference devices (SQUIDs). The SQUID and the readout electronics, were connected via a quarter wavelength (/spl lambda//4) transmission line. This transmission line not only transported the SQUID signal, but also served as the resonant matching circuit. For a dc SQUID of inductance 115 pH (loop size 75/spl times/75 /spl mu/m/sup 2/), we measured a flux noise of 33 /spl mu//spl phi//sub 0///spl radic/Hz at 77 K in the flux locked loop configuration. The corner frequency of 1/f noise was less than 0.5 Hz.