Construction and Characterization of a Sideband-separating heterodyne mixer for Band 9 of ALMA

In this article we present the design, modeling and construction of a side-band-separating (2SB) heterodyne receiver for the frequency range from 600 to 720 GHz that corresponds to band 9 band of ALMA. The characteristics of this receiver present a significant improvement over the current double-sideband (DSB) configuration currently under development. The core of the mixer consists of a quadrature hybrid, two LO injectors, two superconductor-insulator-superconductor (SIS) junctions, three signal-termination loads, and two IF filtering systems. All these parts were modeled and optimized prior construction. Our 2 mixer exploits waveguide technology and has been constructed in the split-block technique. We used state-of-the-art CNC micromachining which permitted us to obtain the small dimensions required for this frequency range. The constructed receiver presents a good performance but we suggest various ideas for further improvement