Analysis of a coaxial waveguide corrugated with wedge-shaped radial vanes or ridges considering azimuthal harmonic effects

Abstract

The analysis was developed for a coaxial waveguide for two configurations - one in which the central conductor is corrugated in axial slot-wedges, with ridge-wedges between them, and the other in which the outer conductor is provided with radial metal vane-wedges. Azimuthal harmonics were considered in the structure regions, the effects of which were ignored in earlier published analyses based on the surface impedance model to replace the interface between the two structure regions by a homogeneous reactive surface. For both the structure configurations, one and the same form of the dispersion relation with proper interpretation of the symbol for the radius of the ridge/vane was obtained. The dispersion relation obtained by the present analysis was validated against that obtained by other analytical methods reported in the literature. The shape of the dispersion characteristics is found uncontrollable by the structure parameters, and therefore the structure cannot be used for broadbanding a gyro-TWT. However, the plot of the eigenvalue versus the ratio of the outer conductor to ridge/vane radii strongly depended on the ridge/vane parameters. Thus the structure with its cross section tapered and ridge/groove parameters optimized has the potential for providing mode rarefaction in high-power, over-sized, over-moded gyrotrons.