Low-noise sub-millimeter wave local oscillators for ALMA

High signal-to-noise ratio sub-millimeter wave local oscillators (LOs) were developed and produced for the Atacama Large Millimeter Array (ALMA). They cover fractional bandwidths of 15-25% from 92 to 942 GHz. The LOs were designed and tested for high signal-to-noise ratio since they are used to drive single-ended mixers. Integrated millimeter-wave multi-chip MMIC modules, employing custom and commercial MMICs, were designed to yield the required power and SNR performance. 73 modules of the LO have been produced for each of the six bands to date, with two more bands currently under construction.