GB960683A - Improvements in or relating to waveguides - Google Patents

Abstract

960,683. Electromagnetic waveguides. MARCONI CO. Ltd. June 14, 1960 [Nov. 30, 1959], No. 40577/59. Heading H1W. A waveguide coupling arrangement comprises two hollow circular sectioned waveguides 1 and 2 joined end to end and constructed to propagate therethrough radio energy in the H on mode, the waveguide walls providing conductive paths parallel to the axes of the guides and each sharing a different impedance over the major part of its length, at least one of the guides, 1, having internal grooves la whose dimensions are varied in such manner that the minimum diameter of the guide over the grooved portion remains constant, thereby to provide a gradual transition of surface impedance from the value over the major part of the lengths of the guide to another value approaching that of the surface impedance of the other guides at the end thereof. The guides 1 and 2 are held together by a sleeve 4, the guide 2 in Fig. 1 being a helical guide 2a in a sheath 2b of synthetic material. In the construction shown in Figs. 1 and 3 the grooving la is in the form of internal ring triangular grooves, in a solid walled grade, which are of a depth and/or width which is increased from groove to groove towards the end of the guide or of a depth and/or width which is increased from group of grooves to group of grooves towards the end of the guide. Alternatively the grooving can be in the form of a screw thread of increasing depth and/or width towards the end of the guide. In the construction shown in Fig. 2 the guide 2 consists of a metal helix 2c whose turns are in contact contained in a sheath 2b of synthetic material, the metal helix being formed of metal wire or strip the cross-sectional dimensions of which are reduced, either gradually or in steps, over a length at one end of the guide. In the construction shown in Fig. 3 the flexible guide 2 is built up of metal rings 2d spaced by rings 2e of dielectric material. The desired gradual variation of surface impedance, which may be effected in a solid walled guide or a flexible guide, or in both, can be in accordance with a linear, binormal or exponential law.