THEORETICAL CONSIDERATIONS FOR THZ SIS MIXERS

In this paper we examine what is known and what is not known about the behavior of submillimeter SIS mixers. Data indicate that for low frequency SIS mixers, Josephson 'drop-back' noise occurs at low dc bias voltage when the instantaneous voltage switches to zero during each rf cycle. A simplistic extrapolation of this effect gives an upper frequency limit of roughly omega //g//a//p/2 for SIS mixing. It is now clear that drop-back noise can be avoided up to at least omega //g//a//p.