Rectangular Waveguide Radial Combiners With Coaxial or Circular Intermediate Waveguide Sections Based on Stub Matching

This article presents a systematic design approach and a novel configuration for compact radial combiners with rectangular waveguide ports. The design approach relies on utilizing short-circuited stubs to match the rectangular waveguide ports to their first interface with the radial cavity. The integrated stubs can then be seamlessly integrated using either a pyramidal or a curvilinear profile that makes up the matching sections. The designs act as transformers between the frequency dispersive rectangular waveguide peripheral ports, and either an intermediate coaxial waveguide operating in the transversal electromagnetic mode (TEM) or a circular waveguide operating in the TM01 mode. Compact transitions are then used to connect the intermediate waveguide to a rectangular waveguide port. The proposed designs are aimed at applications where compact size and high-power handling are of high importance. The design methodology utilizes simplified models that take advantage of the inherent symmetry in the structure. In the curvilinear designs, the matching is achieved using a surface described by a third-order polynomial. The profiles minimize the reflection coefficient at the common intermediate port. Two designs are presented as proofs of concept. One design was fabricated and tested, demonstrating very good results.