ALMA Band 5 (163-211 GHz) sideband separation mixer design

Paper in proceeding, 2008

We present the design of ALMA Band 5 sideband separation mixer based on Niobium superconducting SIS junctions and first experimental results for the double side band mixer. In this mixer the LO injection circuitry is integrated on the mixer substrate using a microstrip line directional coupler with slot-line branches in the ground plane. The isolated port of the LO coupler is terminated by a wideband floating elliptical termination. The mixer employs two SIS junctions with junction area of 3 ?m2 each, in twin junction configuration, followed by a quarter wave transformer to couple it to the RF probe. First measurements of the DSB mixer show promising results with noise temperature around 35K over the entire band.