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IEEE Transactions on Magnetics

Parametric amplification in Josephson tunnel junction arrays at 33 GHz

Francis N. Goodall, F.V. Bale, S. Rudner, T. Claeson, Thomas F. Finnegan

Published Jan 1, 1979• 10 citations
Publisher

Abstract

Progress on the development of a low-noise superconducting parametric amplifier operated at liquid helium temperatures and designed for practical use with a radio telescope at 33 GHz is reported. Series arrays of small Pb - Pb oxide - Pb tunnel junctions (\sim 20 \mum × 20 μm) are coupled in a microstrip configuration and the Josephson device is operated as a reflection-type amplifier in the doubly degenerate mode. Various practical considerations in using such a devise on a telescope are reviewed. In preliminary experiments, gains of greater than 13 dB have been observed near 33 GHz.

DOI
10.1109/tmag.1979.1060278

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Journal of Applied Physics•Mar 1, 1977•42 citations
Progress on the development of a low-noise superconducting parametric amplifier operated at liquid helium temperatures and designed for practical use with a radio telescope at 33 GHz is reported. Series arrays of small Pb - Pb oxide - Pb tunnel junctions (\sim 20 \mum × 20 μm) are coupled in a microstrip configuration and the Josephson device is operated as a reflection-type amplifier in the doubly degenerate mode. Various practical considerations in using such a devise on a telescope are reviewed. In preliminary experiments, gains of greater than 13 dB have been observed near 33 GHz.
Arrays of 10 or 40 series-connected small densely packed Josephson tunnel junctions were successfully operated as parametric amplifiers at 10 GHz. Between 50 and 90% of the junctions in an array were observed to work coherently in the amplification process. Signal gain exceeding 24 dB was achieved with a pump power as low as −50 to −70 dBm. A power width (i.e., the range of the pump power for a gain within 3 dB of the peak gain) of 0.25 dB and a bandwidth of 15 MHz were measured for 20-dB gain. The power width was in accordance with theory but the bandwidth was reduced, probably due to noise saturation effects. The latter effects can be reduced by lowering the input noise temperature or by including an external band limitation. The noise temperature was also increased by saturation; however, with an external bandwidth of 60 MHz, a noise temperature of 30±20 K was measured. The application of a magnetic field has proved extremely useful as a means of tuning the amplifiers to stable high-gain operating points. This tuning was also utilized in evaluating the amplifier parameters, and the theory by Feldman, Parrish, and Chiao has been verified. The upper frequency limit for a lead tunnel junction amplifier ought to be well above 300 GHz.
We have observed doubly degenerate parametric amplification and oscillation at 36 GHz from a single point-contact Josephson junction. The experimental results agree qualitatively with theoretical calculations based on the resistively shunted junction model. The estimated noise temperature of an amplifier with 11 dB net gain is consistent with zero, but has an upper limit of 50 K. Attempts to observe parametric amplification in the singly degenerate mode with a pump frequency of 72 GHz were not successful.