AN UNSYMMETRICAL-DIELECTRIC LOADED HELICAL STRUCTURE WITH NEGATIVE DISPERSION CHARACTERISTICS AND A WIDEBAND TRAVELLING-WAVE TUBE USING THE SAME

摘要

An unsymmetrical-dielectric loaded helical structure with negative dispersion characteristics and a wideband TWT using the same is disclosed. The helical structure has a helix disposed between the electron-beam-generating apparatus and the electron beam collector, dielectric supporting rods, and a metal envelope. The dielectric supporting rods is constructed of at least one first dielectric supporting rod with a first dielectric constant, and a plurality of second dielectric supporting rods with a second dielectric constant. The first dielectric constant is greater than the second dielectric constant, so that increasing capacitive impedances of the low-frequency waves are considerable with respect to those of the high-frequency waves are considerably with respect to those of the high-frequency waves, resulting in negative dispersion characteristics with larger phase velocities of the high-frequency waves than those of the low-frequency waves.