The Spiral Groove Of Any Shape With A Center Dielectric Rod Helical Groove Slow-wave Characteristics Of Study

As the key component of the beam-wave interaction of a Traveling Wave Tube (TWT) for exciting microwave energy, the slow-wave structure (SWS) basically determine the performance of the TWT. So, searching for novel slow-wave structures is one important developing direction of the TWT in order to improve the broadband characteristic and increase the operating frequency and power capacity.The thesis has thoroughly studied on a novel slow-wave structures—the arbitrarily-shaped helical groove waveguide and the dielectric into the arbitrarily-shaped helical groove waveguide. By a large amount of calculations, the influence of the structure dimensions and the dielectric parameters on dispersion characteristic and coupling impedance of this kind of slow-wave structure is obtained. Then, the linear beam-wave interaction theories of the arbitrarily-shaped helical groove waveguide and the dielectric into the arbitrarily-shaped helical groove waveguide are deduced. By the numerical calculations, the relationship is got between the small signal gain, bandwidth, electromagnetic " hot " velocity and the electronic beam, the structural parameters. The method of increasing the bandwidth or gain is obtained. Several important and valuable results which bring forth new ideas are achieved and listed as the followings:1. Considering the influence of high evanescent modes, we have obtained the common theory. By the comparing between theoretical calculation and experimental data, we found the theory can accurately describe the high-frequency characteristic of this kind of slow-wave helical groove structure. Then, five representative shapes are chosen and researched particularly (triangle shape, cosine shape, trapezoid shape, rectangular shape and swallow-tailed shape). The results show that:(a) The influence of the groove shape on the low cut-off frequency is great at certain groove depth; the high cut-off frequency is gradually lowered from triangle profile, cosine profile to swallow-tailed profile.(b) When the depth of the groove is relatively shallow, the helical triangle-shaped helical groove has the widest bandwidth, the least dispersion, and the fastest phase velocity.