The achieved progress is based on computer aided modelling of waveguide SIS mixers. The computations have been verified in experiments with scale models and with existing SIS mixers. Model predictions of low-noise, fixed-tuned operation of mixers with new versions of the Nb printed circuits containing SIS junctions and impedance transformers are now confirmed by the performance of the receivers based on the new mixers.
Modelling of sideband rejection in the mixers supports the optimization of the mixer and the SIS junctions printed circuit design with the aim of providing stable, low noise receiver operation with good rejection of the image band.
The SIS mixers consist of a mixer block, a single backshort and an integrated circuit with the SIS junctions printed on the quartz substrate. Being conservative with the mixer blocks, except the 3 mm mixer, we made new designs of the integrated superconductive circuits optimized with the mixer model according to different criteria: coverage of the specified frequency bands, stability of mixer operation, and sideband rejection using a single backshort or a broad band, fixed tuned operation of the mixer.