Waveguide choke coupling having face of joint interrupted by orthogonally intersecting choke grooves to reduce unwanted mode resonance

摘要

902,128. Waveguide couplings and switches. DECCA Ltd. Aug. 15, 1960 [Aug. 19, 1959], No. 28399/59. Class 40 (8). A coupling between two waveguides is provided with choke grooves and with further grooves or recesses which define the boundaries of the leakage transmission path. The flange 11 of rectangular waveguide 10, Fig. 1, is provided with choke slots 12, 13 preferably one quarter-wavelength deep and arranged one quarter-wavelength from the edge of the waveguide. Further slots 14, 15 also about one quarter-wavelength deep, define the width of the leakage transmission path and confine the leakage energy to a mode similar to the TEM parallel-plate mode. So long as the width of the path is less than one half-wavelength, higher order symmetrical modes are suppressed. The two sets of grooves may cross each other and extend to the edges of the flange (Fig. 2, not shown). The two additional slots 14, 15 may each consist of two portions, each portion extending from an extremity of a choke slot to a point near a corner of the waveguide (Fig. 3, not shown). Fig. 5 shows a symmetrical version of this arrangement for use with a square waveguide 50. The shape of the outer edge of the slots is unimportant. Thus the slots shown in Fig. 5 may be of non-uniform width with the outer edges lying on a circle (Fig. 6, not shown). In the arrangement shown in Fig. 4, the outer edges of the slots 44, 45 extend outwardly to form additional slots 46, 47. In the case of a circular waveguide, the choke slot is circular and the slots forming the leakage path boundaries are arranged radially. The invention may be applied to a waveguide switch of the type having rectangularsection transmission paths 86, 87, Figs. 10 and 11, arranged within a cylindrical rotor 85 and arranged to connect pairs of terminals in a surrounding stator 80. One or more choke slots, e.g. 96, 97, 98, 99, are arranged between the ends of adjacent transmission paths and one or more circumferential slots, e.g. 100, 101, are arranged adjacent the narrow sides of the rectangular sections. The slots may be in either the rotor or the stator or in both. To enable accurate location of the rotor it is provided with a spring-pressed ball (Fig. 12, not shown) adapted to engage recesses in a plate 95 fixed to the cover 88 of the stator.