| Travelling wave tubes (TWT) are the heart parts of radar systems, communication systems, electronic counter-measures, remote-control &test devices, accurate guidance equipment, etc., and play important roles in the modern nation defensive equipment and economic areas. Moreover, as the key component of the beam-wave interaction of a travelling wave tube for exiting microwave energy, the slow-wave structure (SWS) basically determines the performance of the TWT. In this dissertation, a series of detailed studies have been made by theoretical method combining with numerical analysis, and a great deal of valuable conclusions have been obtained. All the works in this dissertation provide theoretical basis and technical ensurance for designing the high power TWTs.Our main and creative works are as following:1. A detailed numerical calculation for the propagating wave's dispersion characteristics has been made. The dispersion equation of the symmetrical mode propagating in the high power ring-plane slow wave circuit is developed, by means of the special variational method, combining with the field matching method. The numerical results of the dispersion equation are also compared with the experimental values when the different number of basic functions is chosen. Finally, the numerical results are given in terms of dispersion relation curve and the influence of several geometrical dimensions on the dispersion characteristics is discussed. It shows that the ring-plane TWT, which is of large diameter, and allows for high average power capability, can improve the propagating wave's characteristics and gain a relative broad bandwidth by means of modifying the geometrical dimensions of the circuits.2. Linear theory of the beam-wave interaction in the ring-plane TWT has been studied. Firstly, in considering the thickness and the relativistic effect of the hollow electron beam, the hot dispersion relation including the electron beam space chargeineffect for the ring-plane traveling wave tube is obtained in this paper, by making use of the variational method and combining with the field matching method. Secondly, the numerical results are given in terms of the small signal gain curve. Finally, the influence of the radius of the electron beam, current of the electron beam, the acceleration voltage and the geometrical dimension of the slow-wave structure on the small signal gain are discussed. Studies present that: there exists an optimum beam voltage for the maximum gain; the gain increases with the beam current; the beam radius effects the gain intensively; the ring-plane TWT is appropriate to work in the millimeter wave band for it's character of high gain and narrow band, and can gain both high power output and relative broad bandwidth by choosing appropriate beam parameters and geometry dimensions.3. The thermal behavior of the ring-plane TWT in the interaction area is analyzed by means of the thermodynamic method. The geometric factor is defined by solving the heat conductive equation, which describes the temperature characteristics in the case of the constant heat transferring coefficient. Starting from the definition of the geometric factor, the actual temperature rising of all the assembly of the TWT is calculated, under the case of that the heat conducting coefficient varies with the temperature. Making use of the numerical results, the maximum temperature is also given in diagrams. The influences of the thermal and geometrical parameters on the heat behavior are discussed. By the discussion we can get the designing principles as following: the thickness of the pole pieces should been decreased and the axial width should been increased as possible as on the condition of ensuring the focus of beam; the radial length and thickness of plane should been considered carefully, and make radial length more shorter, thickness more bigger but not cause strong dispersion; the dimension of the ring have dramatically affect on both the power capability and the dispersion, so the... |
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