Conceptual design of the Band 9 receiver. The RF signal enters the receiver through a cryostat window W and infrared filters F1 and F2. In the optics assembly (OA) the beam is refocused as well as split into orthogonal polarization components and combined with the LO signals. Each polarized beam feeds a SIS-based DSB mixer (SIS), and the resulting IF signal passes through a circulator (CIRC) before being amplified (LNA) for further processing. The LO signal is initially generated at the local oscilator unit (LOU) outside the cryostat and then multiplied by nine on the 110 K stage (×9). A pair of infrared blocking filters (F3) is placed in front of the LO sources in order to minimize the thermal radiation load from the 110 K level.