DISTRIBUTED QUASI-PARTICLE MIXING IN A NONLINEAR TRANSMISSION-LINE ATSUBMILLIMETER WAVELENGTHS

A new class of distributed mixer based on the non-linear quasiparticle tunnel current in a superconductor-insulator-superconductor transmiss ion line has been proposed and tested. The Nb /Al/AlOx/Nb junctions us ed in our mixers are typically 200 nm wide and are between 1 and 2 gui ded wavelengths long. Compared with the traditional submillimeter lump ed element quasiparticle mixer, the distributed mixer requires lower c ritical current densties, lower magnetic field as well as simpler tuni ng circuitry. Experiments have been performed in various sub-millimete r frequency bands. Receiver noise temperatures of 66 K at 460 GHz, 210 K at 630 GHz and 600 K at 780 GHz have been measured. These noise tem peratures are comparable to or slightly better than the noise temperat ures of the corresponding lumped element mixers.