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Kim K.-T.;Kim M.-S.;Chong Y.-W.
- Progress in Superconductivity
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- v.7 no.1
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- pp.11-16
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- 2005
Coupling of non-linear oscillators have long been an interesting problem for physicists. The coupling phenomena have been frequently observed in Josephson junction series array, which have been used for Josephson voltage standard. Interestingly pronounced self-generation effect has been found during recent development of Josephson arrays for programmable Josephson voltage standard. But the coupling effect between the self-generations is not fully understood yet. We present harmonically approximated analytical solutions for coupled self-generations in the Josephson arrays, i.e., Superconductor-Insulator-Normal metal-Insulator-Superconductor (SINIS) array, externally shunted Superconductor-Insulator-Supercondctor (es-SIS) array, Superconductor-Normal metal-Superconductor (SNS) array. We find that the coupling between the self-generated Josephson oscillations through microwave transmission line plays critical role in microwave property of the Josephson array.
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Kim, K.T.;Kim, M.S.;Chong, Y.;Kim, W.S.;Song, W.
- Progress in Superconductivity
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- v.9 no.1
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- pp.56-61
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- 2007
The most recent improvement in the 10 V array system was carried out with focusing on noise reduction. We have evaluated the uncertainty of the 10 V Josephson array system after the improvement. The uncertainty evaluation of 10 V standard included a comparison with a programmable Josephson array system at 1 V. Every contribution to the measurement uncertainty was evaluated in the level of $10^{-10}$. The estimated combined uncertainty was found to be approximately $10^{-9}$ at 10 V, which was limited only by the indirect verifying method. In the near future, a direct comparison with another 10 V Josephson voltage standard is expected to be carried out to provide more accurate uncertainty evaluation for the KRISS Josephson voltage standard.
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이문규;남상욱;엄경환;김규태
- Journal of the Korean Institute of Telematics and Electronics D
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- v.35D no.3
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- pp.1-10
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- 1998
A new oscillator configuration is presented and tested for Josephson voltage standard operated at the cryogenic(4.2K) temperature. Features of active devices are investigated in aspects of 1/f noise, output power, and current collapse at low temperature. The output power of oscillator is optimized by a nonlinear design approach called Harmonic Two Signal Method(HTSM). The embedding newworks of the generalized six oscillators with tow loads are derived. A HEMT oscilliator is designed in X-Band for the Josephson voltage standard and tested at room and cryogenic(4.2K) temperatures. Oscillation frequency, output power, C/N ratio, and fequency stability are compared at room and low temperatures.
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홍현권;박세일;김규태
- Progress in Superconductivity
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- v.4 no.1
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- pp.59-63
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- 2002
10-V Josephson junction array arranged in 8 parallel stripline paths was fabricated using self-aligning and reactive ion etching techniques. These techniques were introduced in detail with aim of obtaining high-quality junctions. The array has 18,184 Josephson junctions with the area of $12\mu\textrm{m}$$\times$$38\mu\textrm{m}$. The gap voltage and minimum critical current density were about 2.7 ㎷ and ／$23 A\textrm{cm}^2$, respectively. And the critical current density and leakage current at 5 volt were about 27 $A／\textrm{cm}^2$ and $5\mu\textrm{A}$, respectively When operated in the frequency range of 76-88 ㎓, the away generated constant voltage steps up to 14-19 V. The step size near 10-V was more than 7 $\mu\textrm{A}$.
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Chu, Hyung-Gon;Kang, Joon-Hee
- 한국초전도학회:학술대회논문집
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- v.10
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- pp.160-164
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- 2000
Digital to analog converters based on the Josephson effect are promising for voltage standard, because they produce voltage steps with high precision and good stability. In this paper, we made a simulation study on RSFQ D/A converter. RSFQ D/A converter was composed of NDRO cells, T(toggle) flip-flops, D flip-flops, Splitters and Confluence Buffers. Confluence Buffer was used to reset the D/A converter. We also obtained operating margins of the important circuit values by simulational experiments.
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