Design of SIS Mixers for SMA 400 - 520 GHz Band

Abstract

SIS junction mixers were designed for SMA 400 - 520 GHz band, which is similar to ALMA band 8 (380 - 500 GHz). Two schemes were used to tune out the parasitic capacitance of the junction. When shunt inductors were employed, the input resistance is equal to R (close to R0), much higher than R/(omegaRC)2 when series inductors were used. This facilitates the impedance matching between the junction and the waveguide probe. Waveguide probe design was varied to achieve a low feed-point impedance to match the junction resistance. The optimal feed- point impedances for lower receiver noise temperature were also discussed.