Conversion Gain in MM-Wave Quasiparticle Heterodyne Mixers

摘要

The physical mechanisms which give rise to conversion gain in SIS quasiparticle mixers are studied. It is shown that the S-shape tunneling structure at the gap voltage of the I-V curve is essential in achieving conversion gain. In the development of SIS quasiparticle mixers, a new approach is used to analyse the embedding network of the mixing experiment. This method as described in this paper has the advantage over conventional methods that no separate measurements are necessary. In order to obtain a complete picture of the performance of SIS quasiparticle mixers, the photon-assisted tunneling theory used by Tucker to describe quasiparticle mixing is extended here to include pair current contribution. Based on this complete quantum theory the effects of the Josephson noise on SIS quasiparticle mixing is discussed and an upper frequency limit of SIS quasiparticle mixing is estimated. (Author)