Upper panel: 3D CAD model for the WCA configuration. The mechanical layout with the downconverter unit visible and placed on its own plate. Middle panel: underside of the WCA, where the IF stage is located. Lower panel: photo of the assembled down-converter unit including all RF parts (i.e. the LO multiplier, amplifier, RF mixers, and isolators), but excluding the IF parts (i.e. the hybrid coupler and IF amplifiers).