PROPAGATION CHARACTERISTICS OF A VARIANT OF DISC-LOADED CIRCULAR WAVEGUIDE

The shaping of dispersion characteristics in a variant of disc-loaded circular waveguide was studied through electromagnetic analysis for assessing the structure for wideband coalescence of the beam- and waveguide-mode dispersion characteristics that entails the wideband gyro-travelling-wave tube (gyro-TWT) performance. In this variant of disc-loaded circular waveguide, the alternate disc- hole radii were varying, however, the structure was periodic. The structure periodicity coupled with Floquet's theorem and fleld- matching technique resulted into the dispersion relation of the inflnitely long structure. A numerical code was developed to solve the dispersion relation, and the dispersion characteristics of the structure were analyzed for the azimuthally symmetric TE-modes. The efiects of structure parameters were studied for getting a straight-line portion of the dispersion characteristics over a wide frequency range. The dispersion shaping was projected for typically chosen TE01-mode. The results were validated against those obtained for the conventional and un-conventional known structures and those obtained using commercially available simulation tool. The variation of azimuthal electric fleld intensity over the radial coordinate was also studied to examine the control of structure parameter for maxima-position, where the gyrating electron beam would be positioned for optimum beam- wave interaction in a gyro-TWT.