The figure shows a prototype radial power-combining waveguide structure, capable of operation at frequencies from 31 to 36 GHz, that features an unusually large number (N = 24) of combining (input) ports. The combination of wide-band operation and large N is achieved by incorporating several enhancements over a basic radial power-combiner design. In addition, the structure can be operated as a power divider by reversing the roles of the input and output ports.

In this structure, full-height waveguides at the combining ports are matched in impedance to reduced-height radial waveguides inside the combiner base. This match is effected by impedance-transforming stepped waveguide sections. This matching scheme is essential to achievement of large N because N is limited by the height of the waveguides in the base.

This Power Combiner contains 24 internal reduced-height radial waveguides with impedance-transforming height and width steps, plus an internal central matching post.

Power is coupled from the 24 reduced-height radial waveguides into the TE01 mode of a circular waveguide in the base with the help of a matching post at the bottom of the base. (“TE” signifies “transverse electric,” the first subscript is the azimuthal mode number, and the second subscript is the radial mode number.) More specifically, the matching post matches the reflections from the walls of the 24 reduced-height waveguides and enables the base design to exceed the bandwidth requirement.

After propagating along the circular waveguide, the combined power is coupled, via a mode transducer, to a rectangular waveguide output port. The mode transducer is divided into three sections, each sized and shaped as part of an overall design to satisfy the mode-conversion and output-coupling requirements while enabling the circular waveguide to be wide enough for combining the 24 inputs over the frequency range of 31 to 36 GHz. During the design process, it was found that two different rectangular waveguide outputs could be accommodated through modification of only the first section of the mode converter, thereby enabling operation in multiple frequency ranges.

This work was done by Larry Epp, Daniel Hoppe, Abdur Khan, and Daniel Kelley of Caltech for NASA’s Jet Propulsion Laboratory.

In accordance with Public Law 96-517, the contractor has elected to retain title to this invention. Inquiries concerning rights for its commercial use should be addressed to:

Innovative Technology Assets Management
Mail Stop 202-233
4800 Oak Grove Drive
Pasadena, CA 91109-8099
(818) 354-2240
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Refer to NPO-41511, volume and number of this NASA Tech Briefs issue, and the page number.