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A modeling approach is proposed based on transmission line theory for thecharacterization of the periodic rectangular waveguide grating (RWG) structure.Using an equivalent circuit (EC) model the dispersion equation of the structureis derived with largely reduced workloads as compared to the conventionalfield-theory method. An EC based analysis of the RWG structure is performed.Numerical results show a good consistency between the two methods as varyingstructural parameters of significance. The proposed approach is also used forthe taper design with the objective of minimizing wave reflection of thestructure. A resulting multistage taper can deliver a low cumulative reflectioncoefficient on the order of 10^{-3}. Furthermore, the coherence performance ofan RWG based planar Cerenkov maser (PCM) is studied on the driving electronbeam interacting with the traveling harmonic wave. This includes the impacts ofthe grating height uniformity, due to practical machining uncertainty, on thenet wave reflection as well as on the growth rate of the wave in the maser. Theobtained results show, that a non-uniformity on the order of 50 micrometers inthe grating height can increase the reflection level by at least one order ofmagnitude. The PCM coherence can be considerably degraded, in terms of asignificant reduction in the wave growth rate of more than 30% with respect toits theoretical value.

Modeling and characterization of a rectangular waveguide grating structure using transmission line theory for planar Cerenkov masers