Low phase noise 33-40-GHz signal generation using multilaser phase-locked loops

A technique is described in which multiple lasers are heterodyne phase locked in series to generate low phase noise millimeter-wave difference frequencies. The maximum frequencies generated are limited neither by the bandwidth of the loop components nor by the frequency of the radio frequency source. By locking together three external-cavity lasers, 33-40.5-GHz signals are produced with very low phase noise.