Analysis of a Chiral Dielectric Supported Broadband Helix Slow-Wave Structure for Millimeter-Wave TWTs

A novel technique of broadbanding a helical slow-wave structure through negative dispersion shaping is proposed. The model considers a simple continuous chiral dielectric support for the helix inside a metallic barrel, unlike conventional helix slow-wave structures with three discrete dielectric supports at 1200 apart. The dispersion relation of the slow-wave structure was derived following sheath-helix abstraction, suitably benchmarked for special cases, and was used for analyzing the dispersion behavior of a typical slow-wave structure. Chiral dielectric loading could easily provide negative dispersion characteristics (required for broadband operation) by merely controlling the chirality parameter alone. The scheme with its simple geometric configuration is expected to be useful for millimeter-wave devices providing better thermal management.