NOISE TEMPERATURE LIMIT OF A SUPERCONDUCTING HOT-ELECTRON BOLOMETER MIXER

A theoretical analysis for the noise temperature of a low-temperature hot-electron superconducting mixer has been presented. The contributio n of both Johnson noise and electron temperature fluctuations has been evaluated. The theoretical limit of the single-side band noise temper ature of the device due to the intrinsic noise mechanisms has been est imated to be as low as 20-40 K, depending on the film material. The co rresponding noise bandwidth can be as large as 2-3 GHz, for a device w ith the electron-phonon cooling mechanism. An improvement of the sensi tivity is not necessarily followed by a decrease of the mixer conversi on gain bandwidth. (C) 1996 American Institute of Physics.