Analysis of Loaded Substrate Integrated Waveguides and Attenuators

This letter provides an approximate analysis of a slotted substrate integrated waveguide with periodic loading elements using the transverse resonance technique. The technique is used to design a travelling wave attenuator whereby pin diodes are capacitively coupled to the waveguide slot. By changing the bias, and therefore loading resistance, a very constant, variable attenuation is produced over the waveguide band.