ANALYSIS OF A CIRCULAR WAVEGUIDE LOADED WITH DIELECTRIC AND METAL DISCS

A circular waveguide loaded with dielectric and metal discs was chosen to evaluate its dispersion characteristics and dispersion shaping with change of structure parameters for wideband coalescence of beam- and waveguide-mode dispersion characteristics for wideband gyro-TWT performance. The azimuthally symmetric TE-mode analysis of the structure was carried out in fleld matching technique by considering the propagating wave in cylindrical free-space region having radius equal to the hole-radius of metal disc, and the stationary waves in free-space and dielectric regions between two consecutive metal discs. The dispersion relation and, in accordance, a computer code were developed. Further, the roots of the dispersion relation for various sets of the structure parameters were obtained using the developed computer code; the dispersion characteristics were plotted; and the dispersion shaping was projected for typically chosen TE01-, TE02- and TE03-modes. The analytical results were validated against those obtained for the conventional and earlier published structures, and also those obtained using commercially available simulation tool. Finally, a study on azimuthal electric fleld available over the radial coordinate was carried out to show the control of structure parameter on the gyrating electron beam position for the chosen operating mode of a dielectric and metal discs loaded gyro-TWT.