Accession Number:

ADA230167

Title:

SIS Mixer Research

Descriptive Note:

Final technical rept. 1 Feb 1989-31 May 1990

Corporate Author:

VIRGINIA UNIV CHARLOTTESVILLE DEPT OF ELECTRICAL AND COMPUTER ENGINEERING

Report Date:

1990-11-01

Pagination or Media Count:

14.0

Abstract:

Theoretical and experimental research has been conducted to elucidate the basic physics behind the properties of superconductor-insulator-superconductor SIS tunnel junction receiving devices. The properties of an SIS mixer using a slightly nonideal junction, with finite LO power, were determined by analytic expansion of the equations of the quantum theory of mixing. The resulting equations have a particularly simple form. The minimum noise temperature is controlled by the leakage current of the junction. Even the most nearly ideal junctions made today require a considerable LO for best sensitivity nevertheless, even a comparatively large leakage current allows mixer noise to be only a small factor above the quantum limit. The saturation properties of SIS mixers subjected to broad-band thermal noise obey the equations derived for monochromatic saturating signals. The Josephson junction tuning inductor was analyzed with the conclusion that such a device is not feasible with present fabrication techniques. Computer calculations using synthetic SIS junction I-V characteristics predicted the performance of an optimized receiver over its entire operating frequency range. Many aspects of the operation of SIS mixers were clarified and unexpected new phenomena were predicted. A photon picture interpretation of the quantum theory of mixing is in the early stages of development. Niobium nitride edge junctions with excellent current-voltage characteristics were fabricated using novel barrier formation processes. The role of surface damage in the quality of NbN edge junction electrical characteristics was investigated and unexpected results were obtained.

Subject Categories:

  • Electrical and Electronic Equipment
  • Electricity and Magnetism

Distribution Statement:

APPROVED FOR PUBLIC RELEASE