Title :
SIS mixers for low noise millimetre-wave heterodyne receivers
Author :
Davies, S.R. ; Cunningham, C.T. ; Little, L.T.
Author_Institution :
Electron. Eng. Labs., Kent Univ., Canterbury, UK
fDate :
3/22/1988 12:00:00 AM
Abstract :
The development of ultra-low-noise receivers at frequencies of >200 GHz is primarily driven by astronomical applications. The most sensitive millimeter-wave receivers that have presently been constructed make use of the strong mixing afforded by superconductor-insulator-superconductor (SIS) tunnel junctions. In a collaborative project between UKC and RAL, a 230 GHz laboratory receiver has been built using a lead alloy SIS junction as the mixing element, mounted in 4:1 reduced-height waveguide, terminated at one end with a circular cross-section, adjustable backshort. Best results indicate a double-sideband receiver noise temperature of TR(DSB)≃120 K, which represents state-of-the-art performance at this frequency. Initial difficulties in achieving good mixing performance prompted an investigation into the importance of the `quality´ of mixer block backshort tuning elements. An analysis of the mixer equivalent circuit is presented which allows for loss in a non-ideal mixer block, and 3-port mixer model calculations are discussed which incorporate this analysis into the Tucker quantum theory of mixing
Keywords :
equivalent circuits; gold alloys; indium alloys; lead alloys; mixers (circuits); nonlinear network analysis; radio receivers; radioastronomical techniques; radiotelescopes; solid-state microwave circuits; superconducting junction devices; 230 GHz; 3-port mixer model calculations; EHF; MM wave type; PbInAu-PbAu; RAL; SIS mixers; UKC; adjustable backshort; backshort tuning elements; heterodyne receivers; low noise; millimetre-wave; mixer equivalent circuit; mixing element; radioastronomy; radiotelescopes; reduced-height waveguide; submillimetre frequencies; superconductor-insulator-superconductor; tunnel junctions;
Conference_Titel :
Microwave Devices, Fundamentals and Applications, IEE Colloquium on