GB986494A - Improvements relating to coupling devices for high frequency electrical circuits - Google Patents

Abstract

986,494. Waveguide directional couplers; magnetrons; travelling-wave tubes; klystrons. ELECTRIC & MUSICAL INDUSTRIES Ltd. May. 31, 1961 [June 7, 1960], No. 19864/60. Headings H1D and H1W. A directional coupler comprises two rectangular waveguide sections 1, 2 coupled by apertures 9 in a common narrow wall. The apertures are sealed by dielectric material e.g. ceramic discs and the input side of the coupler forms part of the envelope of a klystron, travelling-wave tube or magnetron. The coupler shown is of the whole-power type in which a progressive transfer of energy is achieved by gradual variation of propagation and coupling parameters. Thus, the outer walls of the sections are distorted to achieve a variation in width indicated in Fig. 2, where the three sections are taken on lines a, b, c of Fig. 1. At the two extremities of the coupling section the phase propagation constants are unequal and the apertures 9 are dimensioned to provide minimum coupling. At the centre, the propagation constants are equal and the coupling is a maximum. If the input is applied at the port 3, the characteristic coupled mode propagated is the high velocity mode, and if applied at the port 5, is the low velocity mode. In either case, an energy transfer, indicated in Fig. 2 by electric field intensity curves, takes place.