An overview of quasi-optical power combining: were we are and how we got here

There is a continuing and unmet need for high power, solid-state sources at microwave and millimeter wavelengths. At microwave frequencies, transmission line or cavity combiners have been successful, but at millimeter wavelengths this approach has problems in terms of losses, power output and dimensional tolerances. In the past few years, significant efforts have been carried out to develop planar arrays of solid-state oscillators in order to produce spatial power combining. These structures have used open Fabry-Perot as well as conventional transmission lines for combining the active devices, to proved feedback for coherent locking of the individual oscillating devices and to couple energy to an electromagnetic wavebeam. In addition a new class of hybrid planar quasi-optical waveguides and resonators are under investigation for power combining. Active devices utilized have included two terminal GUNN or IMPATT diodes as oscillators, and three terminal devices such as FETs or HEMTs as both oscillators and amplifiers. With three terminal devices currently being more popular. This presentation discusses architectures under active investigation