Research On Coaxial Helical-Groove Slow-Wave Structure

Seeking for some new slow-wave structures with broader bandwidth and higher power capacity is the constant goal. Worldwide scholars have made a great effort in this field since 50's of twenty century. In recent years, especially, it has been developing rapidly due to excellent prospects of military and commercial application. The Coaxial helical-groove slow-wave structure, an all-metal slow-wave circuit, has advantages of good heat dissipation and great size. With coaxial structure, it has no low-cut frequency. Therefore it might be one of the middle bandwidth slow-wave structure with high-power capacity. In this dissertation, the expressions of the dispersion and the coupling impedance of the coaxial helical-groove slow-wave structure including rectangle-shaped helical-groove and ridge-loaded helical-groove are concluded, and the effect of various circuit dimensions on the RF characters is investigated by the numerical computation.; Then we have made small-signal analysis and large-signal analysis for beam-wave interaction in the slow-wave structure. The relations of bandwidth, efficiency and output power to the dimensions are discussed by numerical computation, so as to find the ways of broadening bandwidth and advancing output power. The major achievements are listed as the followings.(1) Based on field theory, the dispersion equation and the coupling impedance of the coaxial rectangle-shaped helical-groove slow-wave structure are obtained, and the influence of various circuit dimensions on the dispersion relation and the coupling impedance is discussed. The results of this paper would be helpful to designing this type of slow-wave structure.(2) The dispersion equation of the coaxial rectangle-shaped helical-groove slow-wave structure with an annular electron beam is obtained according to self-consistent field theory. The computation results of the hot dispersion equationindicate the relations between electron beam parameters and the small signal gain. (3) The coaxial ridge-loaded helical-groove structure is presented for the first time. Its dispersion equation and the expression of the coupling impedance are given by field-matching method. The relations of the phase velocity and the coupling impedance to the structural dimensions are discussed by numerical calculation. (4) The dispersion equation of the circuit with an annular electron beam is obtained according to self-consistent field theory. The influence of various electron beam parameters on the small signal gain is investigated and discussed by the numerical computation.(5) Referring to Tien's one-dimensional disc model, we put forward one-dimensional ring model within coaxial structure. On the basis of equivalent circuit, the equations describing the large-signal operation of the coaxial helical-groove traveling-wave amplifier are derived, then, the charge of high frequency voltage and electronic phase along longitudinal direction, and parameters such as saturation gain and interaction efficiency are discussed.(6) Using resonance method, we have made experiments on the dispersion of the coaxial helical groove slow wave structure, and the experimental results are in good agreement with the theoretical data...