High-frequency limits of superconducting tunnel junction mixers
- 1 December 1987
- journal article
- Published by AIP Publishing in Journal of Applied Physics
- Vol. 62 (11), 4482-4498
- https://doi.org/10.1063/1.339038
Abstract
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, fg =(Δ1+Δ2)/h≊87 GHz, of superconductor-insulator-superconductor (SIS) mixers, and at twice the junction gap frequency for S-I-normal metal (SIN) mixers ( fg =Δ1/h) with available millimeter wave sources. Because of the low transition temperature of Al (Tc ≊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 (∼34 Ω) six-junction array SIS mixer operated at f/fg ≊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. Several high-frequency limits are considered in this paper (such as Josephson switching noise, nonequilibrium phenomena, pair breaking, and energy gap limitations). Our results indicate that submillimeter wave SIS mixer receivers are likely to perform well, at least up to their gap frequencies, i.e., the THz region for large gap superconductors. Our QTM calculations showed that conversion gain larger than unity should be possible up to twice the gap frequency. Above this frequency the conversion loss will increase rapidly.Keywords
This publication has 47 references indexed in Scilit:
- Quantum detection at millimeter wavelengthsReviews of Modern Physics, 1985
- Quasiparticle mixing close to the gap frequency in aluminum tunnel junctionsIEEE Transactions on Magnetics, 1985
- Accurate noise measurements of superconducting quasiparticle array mixersIEEE Transactions on Magnetics, 1985
- 85--115-GHz Receivers for Radio AstronomyIEEE Transactions on Microwave Theory and Techniques, 1985
- SIS mixer analysis using a scale modelIEEE Transactions on Magnetics, 1983
- Infinite available gain in a 115 GHz SIS mixerPhysica B+C, 1981
- Negative resistance and conversion gain in SIS mixersPhysica B+C, 1981
- Large conversion efficiency and dynamic range for sis mixersPhysica B+C, 1981
- A SIMPLE QUALITATIVE DETERMINATION OF JOSEPHSON TUNNEL JUNCTION PARAMETERS NEAR THE TRANSITION TEMPERATURELe Journal de Physique Colloques, 1978
- Multiphoton Process Observed in the Interaction of Microwave Fields with the Tunneling between Superconductor FilmsPhysical Review B, 1963