20-40-GHz broadband frequency doubler with gallium aresenide varactor.

A crossed waveguide type varactor frequency doubler is described here which gives a conversion efficiency of 39% and a 4-GHz bandwith (-1 dB) around 40 GHz for 100-mW input power. Gallium arsenide varactor diodes in commerical packages are used, permitting great flexibility, in particular in molecular spectroscopy experiments.