Modular Design of Pyramidal Radial Combiners Based on Nonuniform Parallel Plate Waveguide Sections With Constant Impedance

This article presents a comprehensive treatment to a systematic design methodology of pyramidal waveguide radial combiners, which is based on nonuniform parallel plate waveguide sections with constant wave impedance. A theoretical framework for the design process is first presented, paving the way to a straightforward design procedure for radial combiners with different bandwidths and a different number of ports realized in metallic waveguides. The methodology to design the radial combiner starts with designing the individual transformer sections that provide matching between the individual parallel plate waveguide ports and the common coaxial line output port. This is followed by the design of transitions from coaxial lines to the individual parallel plate waveguide with the appropriate boundary condition. Proper design of different transformer sections makes it possible to achieve the required constant impedance levels for proper matching transformer designs. Two proof-of-concept prototypes were designed, simulated, fabricated, and tested demonstrating good measured results.