A Novel Waveguide-Below-Cutoff Structure With an Extended Cutoff Frequency

In this letter, a novel waveguide-below-cutoff (WBC) structure with electromagnetic bandgap (EBG) surfaces is proposed to increase the cutoff frequency without sacrificing the waveguide size. To implement the proposed WBC structure, EBG arrays with various via patterns are fabricated and attached to the wide walls inside a normal rectangular waveguide. Transmission loss of the WBC structure is measured in terms of different EBG arrays, and it is confirmed that the cutoff frequency could be extended to higher frequencies accordingly.