Non-Bragg resonance in substrate integrated waveguide

Electromagnetic (EM) wave propagation in periodic structure is an interesting research topic in electronic, optical and laser systems. Conventionally, wave propagation in periodic media can be characterized by the Bragg's law where the resonance frequency can be determined by the periodicity of the media and a wave incident angle. However, there is also a kind of non-Bragg resonance which cannot be characterized by the traditional Bragg's law. A non-Bragg resonance has been observed in a rectangular waveguide with corrugated walls by the Cheng et al. [1]. The resonance frequency depends on the waveguide height (or thickness), the periods and amplitudes of the corrugations, and a phase shift between the corrugated walls. Since non-Bragg resonance only occurs under specific geometric conditions, it is also known as geometric resonance [1].