Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE
Performance of a sideband separating SIS mixer for 85-115 GHz
Vessen Vassilev, Victor Y. Belitsky, Christophe Risacher, Igor Lapkin, Alexey Pavolotsky, Erik Sundin
Abstract
We present results of the development and measurements of a heterodyne sideband separating SIS mixer for 85-115 GHz band. The sideband separation is achieved by using a quadrature scheme where a local oscillator (LO) pumps two identical mixer junctions with 90° phase difference. A key component in the mixer is a waveguide to microstrip double probe transition used as a power divider to split the input RF signal and to provide transition from waveguide to microstrip line. The double probe transition enables the integration of all mixer components on a single compact substrate. The design also involves coupled lines directional couplers to introduce the LO power to the mixer junctions. An additional pair of SIS junctions is used to provide termination loads for the idle ports of the couplers. Several mixer chips were tested and similar and consistent performance was obtained. The best single sideband noise temperature is below 40 K with IF bandwidth 3.4-4.6 GHz. The sideband suppression ratio is better than 12 dB for both sidebands across the entire RF band. The mixer was also successfully tested with 4-8 GHz IF band. In this paper we present complete mixer characterization data.