A Novel Multi-Resonant Rectangular Waveguide Junction and Its Applications in Compact Waveguide Multi-Band Filters and Multiplexers

This paper presents a novel multi-resonant rectangular waveguide junction suitable for the design of multi-band filters and multiplexers. The junction can have multiple posts to realize up to four resonant modes. The compact designs, enabled by the junction, are achieved by coupling the resonant modes to coaxial cavities, which are much smaller than regular waveguide cavities at the same frequency. To realize multi-band filters, identical junctions are used at the input and the output of the filter to split and recombine the separate frequency channels. In the multiplexer cases, each channel is coupled at its output to a modified junction that has a single resonant post tuned to the proper channel frequency. Three design examples are provided with an experimental proof of concept of a dual-band filter with a five pole filter in each band. The experimental results agree well with simulations verifying the design approach.