Microwave Design and Performance of PTB 10 V Circuits for the Programmable Josephson Voltage Standard - World Journal of Condensed Matter Physics

WJCMP > Vol.4 No.3, August 2014

Microwave Design and Performance of PTB 10 V Circuits for the Programmable Josephson Voltage Standard ()

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DOI: 10.4236/wjcmp.2014.43016 3,253 Downloads 4,349 Views Citations

Author(s)

Franz Müller, Thomas J. Scheller, Jinni Lee, Ralf Behr, Luis Palafox, Marco Schubert, Johannes Kohlmann

Affiliation(s)

Physikalisch-Technische Bundesanstalt (PTB), Braunschweig, Germany.

ABSTRACT

At Physikalisch-Technische Bundesanstalt (PTB), superconducting 10 V circuits for the programmable Josephson voltage standard (PJVS) are routinely manufactured on the basis of Nb_xSi_1-x barrier junctions. This paper describes in detail the basic design principles for an operating frequency of 70 GHz. It starts with single junctions, discusses their insertion into microstriplines and closes with the whole microwave circuit containing 69,632 Nb_xSi_1-x barrier junctions arranged over 128 microstriplines connected in parallel. The microwave attenuation of this junction type is a key parameter for the 10 V design and we report its experimental determination. Special attention has been devoted to subarrays with just a few Josephson junctions in one of the outermost striplines. The arrangement of these subarrays determines the optimum performance of the complete 10 V series array. The high performance of programmable 10 V circuits fabricated at PTB is characterized by measured operating margins in all subarrays of more than 1 mA centered at the same dc bias current. The observed modulation of the current margins, when changing the frequency around 70 GHz, is explained by microwave reflections caused by the rf waveguide inside the cryoprobe. We determine the current margins in dependence of the output power of a microwave synthesizer and show that 60 mW is sufficient to achieve current margins larger than 1 mA.

KEYWORDS

Josephson Voltage Standard, Programmable Josephson Voltage Standard (PJVS), SNS Josephson Junction, Nb_xSi_1-x Josephson Junction

Share and Cite:

Müller, F. , Scheller, T. , Lee, J. , Behr, R. , Palafox, L. , Schubert, M. and Kohlmann, J. (2014) Microwave Design and Performance of PTB 10 V Circuits for the Programmable Josephson Voltage Standard. World Journal of Condensed Matter Physics, 4, 107-122. doi: 10.4236/wjcmp.2014.43016.

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