The introduction of rods with optimized cross-sectional shape in slow-wave structures (SWSs) for wideband helix traveling-wave tubes can sensibly improve the dispersion maintaining an adequate interactionimpedance level. In this brief, a procedure for analyzing helix SWSs loaded with rods of arbitrary shape, by using an analysis method adopting the inhomogeneous dielectric loading approach, is proposed. The advantages,
in terms of SWS-dispersion improvement, of adopting optimized rod shapes in comparison to the typical rod shapes (i.e., rectangular, circular, and T-shaped) utilized up to now, are also demonstrated.