Low noise SIS receiver performance using Pb alloy tunnel junctions

Abstract

A receiver noise temperature of 61 K (DSB) has been measured for a superconductor-insulator-superconductor (SIS) heterodyne receiver operating at 232 GHz, the lowest value reported to date for such a receiver employing a lead alloy junction. Analysis of the losses of the receiver components yields mixer noise temperature and conversion loss, T-m = 24 K and L-m = 2.1 dB (DSB). These are compared with predictions based on 3-port quantum mixer theory, made using the measured characteristics of the junction and an equivalent circuit for the waveguide mixer mount deduced from scaled modelling experiments