Investigation of SIS Up-Converters for Use in Multi-pixel Receivers
We propose the use of SIS junctions as a frequency up-converter based on quasiparticle mixing in frequency division multiplexing circuits for multi-pixel heterodyne receivers. Our theoretical calculation showed that SIS junctions have the potential to achieve positive gain and low-noise characteristics in the frequency up-conversion process at local oscillator (LO) frequencies larger than the voltage scale of the dc nonlinearity of the SIS junction. We experimentally observed up-conversion gain in a mixer with four-series Nb-based SIS junctions at the LO frequency of 105 GHz for the first time.
KeywordsSIS junction Up-conversion Positive gain Multi-pixel heterodyne receivers Frequency division multiplexing
We thank G. de Lange of SRON and E. Tong of Harvard Smithsonian Center for Astrophysics for fruitful discussions on the FDM scheme and the up-converter simulation, respectively. We also would like to thank T. Takahashi and K. Kaneko of NAOJ for technical assistance with the experiments.
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