Kh.D. Kachayev, M.A. Fursaev

A method of modelling the frequency characteristics of the cells of a square-wave slow-wave structure with throttle supports is discussed here whereas these cells are a transformer of resistances. The cells provide the matching of such a slow-wave structure with the energy output in a straight wave M-type amplifiers. The geometrical parameters of the transforming cells differ from those of the cells of the regular part of the amplifier-s slow-wave structure. The transforming cells contain elements that change their transforming characteristics while their geometrical parameters are varied. The modelling method is based on using an equivalent circuit replacing the transforming cells and on representation of the square-wave slow-wave structure with throttle supports as an aggregate of strip circuit sections. The equivalent system of such cells is a four-pole device loaded on the resistance equal to the wave resistance of the slow-wave structure. The frequency dependencies of this four-pole device-s input resistance are calculated while employing electric circuit theory. The modelling of the transforming cells - frequency characteristics has been realized in a concrete variant while the length of one of the throttles was varied. Data on the frequency dependence calculation of the transforming cells - input resistance for a number of the throttle length values are adduced. The discussed variant of the resistance transformer shows that it is possible to obtain a practically independent value of the active component of the input resistance in the frequency band exceeding 15 % and with an insignificant reactive component of this resistance. This bandwidth is quite enough to provide stable functioning of a straight wave M-type amplifier. When the loop length varies, changes occur in the frequency dependence slope sign of the input resistance-s active component as well as in the character of its reactive component. Thus the loop length changes make it possible to match the energy output with the regular part of the amplifier-s slow-wave structure. It is concluded that the discussed method of modelling allows to simplify the process of matching the slow-wave structure with the energy output of straight wave M-type amplifiers.