Tunable stop band in the spectrum for a periodically corrugated waveguide

We have designed and investigated experimentally a planar periodically corrugated waveguide that allows to control the stop band and hence, transmission through the waveguide. Measurements show that location of the stop band in the frequency spectrum as well as its width depends on the relative position of two corrugated plates. The transmission varies from zero to a maximum value upon shifting of one periodic plate with respect to another on the half period of the corrugation. The results confirm the theoretical prediction of the geometry-driven spectrum transformation from a band-structure form to gapless one upon such a shift of the plates.