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ABSTRACT: This paper presents a mathematical model for determining the stable phase-lock areas of microwave-biased superconductor-normal metal- superconductor Josephson junctions with low normal state resistance and small junction capacitance. The calculations are based on the resistively shunted junction model. The theoretically determined phase-lock areas are in accordance with the experimental results on Nb/HfTi/Nb junctions.
Journal of Applied Physics 12/2008; · 2.17 Impact Factor
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ABSTRACT: The paper describes the theory and the experimental results for the synthesis of precision waveforms by using the pulse-width modulation of the power of the microwave, which drives the superconductor–insulator–normal metal–insulator–superconductor Josephson array. The synthesized sine waveform has a high precision. Its harmonic content was determined to be less than 0.003%. This degree of harmonic content is in agreement with the theory.
Journal of Applied Physics 12/2008; · 2.17 Impact Factor
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Russian Mathematical Surveys - RUSS MATH SURVEY-ENGL TR. 01/2008; 63(3):557-559.
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ABSTRACT: The paper discusses the dynamics of different types of overdamped Josephson junctions biased by a sinusoidal microwave current. The results clarify the theoretical background for optimizing the single junction and the junction array parameters for their use as alternating current (ac) wave form synthesizers. The determined phase lock areas demonstrate the degree of overlap for Shapiro steps [S. Shapiro, Phys. Rev. Lett. 11, 80 (1963)] of different orders as a function of the normalized frequency μ=2πfω<sub>c</sub><sup>-1</sup> , where f is the microwave frequency and ω<sub>c</sub> is the Josephson junction characteristic frequency. For μ≤0.7 , which is a typical operation range for superconductor-insulator-superconductor Josephson junctions in the conventional direct current (dc) voltage standard at the bias frequency range from 10 to 100 GHz , the Shapiro steps overlap completely. For μ≥1.4 [typical for superconductor-normal-superconductor junctions at the same frequency range], the steps do not overlap. This allows for ac voltage synthesis by means of binary arrays and pulse-driven systems. For 0.7≤μ≤1.4 there is a range of partially overlapping Shapiro steps, which allows a rapid switching of the Josephson dc voltages for ac synthesis by microwave power modulation. Experimentally we have achieved this range through properly designed superconductor-insulator-normal-insulator-superconductor junctions.
Journal of Applied Physics 12/2006; · 2.17 Impact Factor
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Russian Mathematical Surveys 03/2004; 59:377-378. · 0.53 Impact Factor
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ABSTRACT: A rectangular-pulse generator based on a Josephson chip is described. An array consisting of 512 nonhysteretic Josephson junctions connected in series and pumped by a 10-GHz-microwave oscillator is used. The sampling step and maximum amplitude depend on the used chip and pump frequency, and are 0.04 and 10 mV, respectively. The switching time is 600 ns with current control and 50 ns with the microwave power modulation.
Instruments and Experimental Techniques 10/2003; 46(6):776-779. · 0.36 Impact Factor
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ABSTRACT: The paper discusses the development of the method for studying the dynamics of an overdamped Josephson junction biased by
a periodic current with controlled parameters, suggested earlier by the authors. The results obtained allow several known
experimental observations to be explained. Analytic expressions for the rate of transient process damping and energy expenditures
necessary for switching a Josephson junction from one quantum state to another are derived. Problems of interactions between
the bias current and supercurrent and the influence of cosϕ-type terms on the rates of transient process damping and energy
conversion are discussed. The results for junction biasing by short (uni-or bipolar) δ function-shaped pulses are obtained
in the form of exact analytic expressions. Diagrams illustrating the dependence of the Shapiro step width on the shape of
biasing pulses are given.
Journal of Experimental and Theoretical Physics 08/2003; 97(3):624-631. · 1.03 Impact Factor
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ABSTRACT: A high-precision comparison of dc voltages generated by a 10 GHz SINIS (superconductor/insulator/normal/insulator/superconductor) Josephson non-hysteretic junction array and a 70 GHz SIS (superconductor/insulator/superconductor) Josephson junction array is described. The paper also describes a method of minimizing the Type A measurement uncertainty. The measurements were carried out at the 10 mV level. The agreement between both output voltages was determined to 0.2 nV with a Type A uncertainty of 0.5 nV.
Metrologia 03/2003; 38(5):471. · 1.75 Impact Factor
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ABSTRACT: A low-frequency waveform synthesizer based on the Josephson-junction (JJ) array is described. A 10-GHz 8-bit JJ-array chip with junctions of a superconductor–insulator–normal-conduction metal–insulator–superconductor type is used in the device. Application-specific software has been developed to control the synthesizer. The preliminary results of synthesis of low-frequency waveforms are presented in a tabular form.
Instruments and Experimental Techniques 08/2002; 45(5):660-664. · 0.36 Impact Factor
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ABSTRACT: The operation principle of a digital-to-analogue conversion (DAC) for an accurate AC waveform synthesis based on a pulse width modulation (PWM) of an output voltage of an overdamped Josephson junction (JJ) array is considered. The PWM of the voltage is achieved by the PWM of a sine microwave JJ array bias at a constant DC bias. A set-up realizing the above method is described. To illustrate the synthesizer operation principle, JJ array I-V curves at two microwave power levels and an example of the PWM voltage signal are shown.
Precision Electromagnetic Measurements, 2002. Conference Digest 2002 Conference on; 02/2002
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ABSTRACT: The effects used for quantum Josephson digital-to-analogue (D/A) conversion are discussed. The dynamics of an overdamped Josephson junction (JJ) driven by a series of short 2π-pulses of programmable intensity and repetition rate is described. The results are presented both analytically and in graphical form.
Precision Electromagnetic Measurements, 2002. Conference Digest 2002 Conference on; 02/2002
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ABSTRACT: An analytic method is developed for studying the electrodynamic properties of Josephson junctions biased with a sequence of
delta-function pulses. Such investigations are of interest in connection with developing, on the basis of the Josephson effect,
analog-to-digital converters and synthesizers producing signals of a preset form with a fundamental precision. Analytic expressions
are obtained that determine phase lock conditions, the mean voltage across the junction, and the boundaries of Shapiro’s steps.
The results obtained are presented in a graphical form for the cases of unipolar and bipolar bias of a junction. The results
are discussed and compared with those known from previous investigations.
Journal of Experimental and Theoretical Physics 11/2001; 93(6):1280-1287. · 1.03 Impact Factor
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ABSTRACT: An experimental setup for accurate measurement of the voltage difference between two Josephson junction arrays irradiated at different microwave frequencies is described. The measurement technique is proposed and the experiment is performed. It is shown that the maximum accuracy is achieved at the optimum measurement time depending on both the measurement conditions and noise behavior of the test equipment.
Instruments and Experimental Techniques 08/2001; 44(5):655-661. · 0.36 Impact Factor
