High-frequency limits of superconducting tunnel junction mixers

Journal Article · Tue Dec 01 00:00:00 EST 1987 · J. Appl. Phys.; (United States)

DOI:https://doi.org/10.1063/1.339038· OSTI ID:6084592

Winkler, D; Claeson, T

We have investigated high-frequency limits of superconducting quasiparticle mixers from experiments on Al/Al-oxide-In/Al (or Ag) tunnel junctions, and from calculations based on Tucker's quantum theory of mixing (QTM). The small superconducting energy gap of Al enabled us to study mixer performance at around the junction gap frequency, f/sub g/ = (..delta../sub 1/+..delta../sub 2/)/happrox. =87 GHz, of superconductor-insulator-superconductor (SIS) mixers, and at twice the junction gap frequency for S-I-normal metal (SIN) mixers ( f/sub g/ = ..delta../sub 1//h) with available millimeter wave sources. Because of the low transition temperature of Al (T/sub c/ approx. =1.3 K), a dilution refrigerator was used for providing temperatures below 1 K. The best mixer conversion efficiency was obtained for a low-resistance (approx.34 ..cap omega..) six-junction array SIS mixer operated at f/f/sub g/ approx. =1 (in this case 73 GHz). The coupled single sideband conversion gain (with no image rejection) was -13.8 dB and the available conversion gain was estimated to -8.4 dB. Complicating nonequilibrium phenomena made it difficult to compare the performance of these relatively high-current-density mixers to the QTM. However, good agreement between calculated and corresponding measured conversion efficiencies and dynamic resistance values was obtained for the low-current-density mixers. Noise due to switching between rf-induced Josephson steps and interference from Josephson mixing could be quenched by a magnetic field.

• Research Organization: Department of Physics, Chalmers University of Technology, S-412 96 Goeteborg, Sweden
• OSTI ID: 6084592
• Journal Information: J. Appl. Phys.; (United States), Vol. 62:11
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
MIXERS
EFFICIENCY
NOISE
PERFORMANCE
SUPERCONDUCTING JUNCTIONS
RADIO TELESCOPES
RADIOASTRONOMY
TUNNEL EFFECT
ANTENNAS
ASTRONOMY
ELECTRICAL EQUIPMENT
ELECTRONIC EQUIPMENT
EQUIPMENT
JUNCTIONS
RADIO EQUIPMENT
TELESCOPES
420201* - Engineering- Cryogenic Equipment & Devices