  As the Atacama Large Millimeter/submillimeter Array (ALMA) nears completion,
73 dual-polarization receivers have been delivered for each of Bands 3 (84-116
GHz) and 6 (211-275 GHz). The receivers use sideband-separating superconducting
Nb/Al-AlOx/Nb tunnel-junction (SIS) mixers, developed for ALMA to suppress
atmospheric noise in the image band. The mixers were designed taking into
account dynamic range, input return loss, and signal-to-image conversion (which
can be significant in SIS mixers). Typical SSB receiver noise temperatures in
Bands 3 and 6 are 30 K and 60 K, resp., and the image rejection is typically 15
dB.
