Microwave Design and Performance of PTB 10 V Circuits for the Programmable Josephson Voltage StandardReport as inadecuate




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At Physikalisch-Technische BundesanstaltPTB, superconducting 10 V circuits for the programmable Josephson voltage standardPJVS are routinely manufactured on the basis of NbxSi1-x barrier junctions. This paper describes in detail the basic design principles foran operating frequency of 70 GHz. It starts with single junctions, discussestheir insertion into microstriplines and closes with the whole microwave circuitcontaining 69,632 NbxSi1-x barrier junctions arranged over128 microstriplines connected in parallel. The microwave attenuation of this junctiontype 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 junctionsin one of the outermost striplines. The arrangement of these subarrays determinesthe optimum performance of the complete 10 V series array. The high performanceof programmable 10 V circuits fabricated at PTB is characterized by measured operatingmargins 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 around70 GHz, is explained by microwave reflections caused by the rf waveguide insidethe cryoprobe. We determine the current margins in dependence of the output powerof a microwave synthesizer and show that 60 mW is sufficient to achieve currentmargins larger than 1 mA.

KEYWORDS

Josephson Voltage Standard, Programmable Josephson Voltage Standard PJVS, SNS Josephson Junction, NbxSi1-x Josephson Junction

Cite this paper

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.





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

Source: http://www.scirp.org/



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