Reflectionless Substrate Loaded Waveguide Bandstop Filter

We present a new waveguide structure featuring reflectionless bandstop filtering and its design method. The reflectionless bandstop filtering is achieved simply by putting a substrate containing microstrip resonators on the bottom surface of a standard rectangular waveguide structure. Hence, whenever needed, a bandstop filtering functionality can be readily added without any structural change in an existing waveguide-based low-power wireless communications system. To verify the proposed structure and design method, reflectionless bandstop filters with one and three attenuation poles were designed, assembled, and evaluated through measurements.