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Applied Superconductivity, IEEE Transactions on

Issue 1 • Date March 1992

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Displaying Results 1 - 6 of 6
  • Fabrication of high quality Nb/AlO/sub x/-Al/Nb Josephson junctions. I. Sputtered Nb films for junction electrodes

    Page(s): 1 - 14
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    The stress, surface morphology, superconducting characteristics, and crystal structure of sputtered Nb films were evaluated to judge their applicability to Josephson-junction electrodes. The film qualities were compared between Nb films deposited by DC and RF magnetron sputtering. The authors concluded that DC-sputtered Nb films are more suitable for junction electrodes and studied the relationship between their film quality and sputtering parameters. They observed that the Nb film characteristics were determined solely by the cathode voltage during sputtering regardless of the other parameters. The authors discuss the changes in film characteristics during Josephson integrated circuit processing.<> View full abstract»

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  • Superconductive gigahertz power supply for Josephson multichip systems

    Page(s): 15 - 20
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1657 KB)  

    To confirm a gigahertz frequency power supply in a multichip system, three-stage superconductive filter-type powering device (SFPD) chips and a resistive load chip for a 500 gate Josephson device were designed and fabricated. Low-loss capacitors required for this gigahertz operation were also developed. The authors tested the operation of the three-stage SFPDs in a multichip configuration with resistive load. A superconductive power supply with frequencies as high as 2.0 GHz was demonstrated in a multichip system for the first time. For a 2.0-GHz SFPD, normal operation was confirmed with a resonant frequency of 2.1 GHz, a resonant level of -31 dB, and a current gain of 22.4. The 0.1- Omega input impedance of the device system was successfully transformed to 49.9 Omega .<> View full abstract»

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  • High-speed experiments on a QFP-based comparator for ADCs with 18-GHz sample rate and 5-GHz input frequency

    Page(s): 21 - 25
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (425 KB)  

    The authors report on the high-speed operation of a superconducting comparator circuit, based on coupling the quantum flux parametron (QFP) to an RF SQUID, which can be used to build a flash-type analog-to-digital converter (ADC). Simulations of this circuit show that it is expected to achieve operation with input signal bandwidths greater than 4 GHz and with a dynamic range equal to at least 4 b of resolution. A QFP-based comparator fabricated with a process using NbN/Pb-alloy Josephson junctions of 5 mu m by 5 mu m and a current density of 100 A/cm/sup 2/ has been examined to evaluate the properties of the QFP-ADC. Analog-to-digital conversion of the comparator has been observed with a QFP activation frequency up to 18.2 GHz. By employing a sampling method, input signals with frequencies up to 5.4 GHz have also been digitized.<> View full abstract»

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  • Quantum flux parametron (QFP) shift registers clocked by an inductive power distribution network and errorless operation of the QFP

    Page(s): 26 - 32
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (877 KB)  

    The authors present 4- and 12-b shift registers capable of operating from DC up to 8.56 and 4.24 GHz, respectively. These circuits' total on-chip power dissipation is estimated to be roughly 10 nW. A novel clock current distribution network permits such high clock frequency and such low on-chip power dissipation. The clock is applied as a standing wave and is distributed by inductive division. With this clock current distribution scheme, no power is dissipated along the clock lines. In spite of the circuits' low output amplitude (tens of microvolts) and of the large crosstalk with the clock frequency, the output waveforms are captured in time domain at microwave frequencies. Also, for the 12-b device, 10/sup 15/ error free operations per quantum flux parametron (QFP) are demonstrated. Finally, the 12-b shift register is the largest QFP circuit reported to date; it is composed of 48 QFPs and one DC SQUID.<> View full abstract»

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  • The distributed Josephson inductance phase shifter

    Page(s): 33 - 38
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    The authors report on a novel microwave phase shifter featuring rapid electronic adjustment, continuous phase control true time delay operation, high device fault tolerance, and very broadband operation. By coupling a large number of superconducting quantum interference devices (SQUIDs) to a superconducting microstrip transmission line, a variable magnetic medium in which the wave velocity is controlled electronically is created. The authors have measured 60 degrees phase shift at 10 GHz, and wideband operation from 5 to 15 GHz for an 8-cm-long Nb transmission line coupled to 1600 SQUIDs, each containing a single Nb/AlO/sub x//Nb tunnel junction. The observed phase shift corresponds to a change in wave velocity of about 1 part in 60.<> View full abstract»

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  • High-T/sub c/ superconducting monolithic phase shifter

    Page(s): 39 - 44
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (470 KB)  

    A high temperature superconducting (HTS) X-band phase shifter using a distributed Josephson inductance (DJI) approach was designed and fabricated. Phase swings of over 60 degrees were measured at 65 K and below, with measurable phase shifts at temperatures above 77 K. High quality HTS films and superconducting quantum interference devices (SQUIDs) were deposited by laser ablation. A total of 40 HTS step edge SQUIDs were successfully integrated into a monolithic HTS circuit to produce a phase shifter in a resonant configuration. The magnitude of the Josephson inductance is calculated and a lumped element model is compared to measurements.<> View full abstract»

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Aims & Scope

IEEE Transactions on Applied Superconductivity contains articles on the applications of superconductivity and other relevant technology.

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Meet Our Editors

Editor-in-Chief
Britton L. T. Plourde
Syracuse University
bplourde@syr.edu
http://www.phy.syr.edu/~bplourde