SCATTERING RESONANCES ON A FAST-WAVE STRUCTURE,

The scattering resonances, or generalized Woods anomalies, that are exhibited on a fast-wave structure are investigated. The fast-wave struc ture analyzed here in detail consists of a par allel-plate waveguide perturbed by a series of periodic, parallel slits in the top plate. In the range agamma 12, the plane wave scatter ing problem is considered for both E and H mode polarizations, and the anomalies are found to manifest themselves as a rapid variation in the phase of the reflection coefficient. When agamma 12, there are no higher order diffracted waves, and the magnitude of the reflection coefficient is therefore fixed at unity. The relative peri odicity is next extended to the range 12 agamma 1, and the scattering problem consid ered for E mode polarization. The periodicity is now such that both the reflected wave and the first higher order diffracted wave propagate transversely. Under such circumstances, it is convenient to use a scattering description for the fields, and the anomalies may then be ob served as rapid variations in both magnitude and phase of the scattering coefficients. Author