Solid-State Spatial Combiner Modules for TWT Replacement

Significant progress has been made in solid-state spatial power combining under recent DARPA and ARO sponsorship, resulting in multiple demonstrations of power modules that can potentially challenge vacuum electronics in some applications. This paper will focus on a broadband waveguide-based spatial combining approach that shows promise for cost-effective MMIC-based power modules capable of generating hundreds of Watts of CW power at X-band, and scalable to higher frequencies up to Ka-band. The waveguide-based system uses stacked trays of broadband traveling-wave antenna structures, housed in a metal waveguiding enclosure that is operated in the dominant TE mode. Each antenna is then essentially a waveguide-to-transmission-line transformer that couples energy from the waveguide mode to a set of power amplifier circuits. The antennas can be electrically close for high power density. Thermal management is simplified by virtue of the modular tray architecture and the surrounding metallic walls which provide a convenient heat sink. Power enters and leaves the system in a single well-defined mode and therefore power distribution and collection is simplified. Such arrays also pose a well-defined electromagnetic problem, and consequently significant progress has been mad