Design of an X/Ku band overmoded coaxial waveguide diplexer for high power microwaves

In this paper, we present an overmoded coaxial waveguide diplexer at X/Ku band for high power microwaves. The design details and diplexing mechanism have been investigated. An overmoded filter based on coaxial corrugated waveguide is proposed as a band pass filter, which operates at TEM mode. To suppress excited TMon modes and keep fundamental TEM mode, the filter is optimized and designed. The designed filter possesses a transmission efficiency over 99% from 9.23GHz to 9.47GHz, while reflection efficiency is over 99% from 9.35GHz to 9.65GHz. A concentric waveguide with 22 coupling holes is designed as an injection structure to diplex Ku band microwaves to the overmoded coaxial waveguide and at the same time stop the X band microwaves. Hence, the diplexing manifold can combine X band and Ku band microwaves into the common waveguide. According to the simulation results, the power handling capacity of the designed diplexer is at giga-watt level, and its transmission efficiency is over 99%.