Patent GB-672976-A (GB)
Title: Improvements relating to radiators for ultra high frequency electro-magnetic energy and apparatus embodying the same
IPC: F41A9/34
Filed: 1949-03-03
Abstract: 672,976. Wave-guides. BRITISH THOMSON-HOUSTON CO., Ltd., CRAICK, W., MILNE, K., and TAYLOR, H. B. March 2, 1950 [March 3, 1949; Nov. 2, 1949], Nos. 5846/49 and 28076/49. Class 40 (vii). [Also in Group XL (c)] A rotary wave-guide coupling comprises two coaxial ring-shaped wave-guides of rectangular cross-section having apertures spaced along the opposed walls of the two guides and means for confining the energy transmitted by the apertures in one guide and received by the apertures in the other guide so that the transmission is substantially unaffected by relative rotation between the two guides about their common axis. Rotary coupling. As shown in Figs. 3 and 4, the coupling comprises two horizontal coplanar co-axial annular guides 10 and 16 of rectangular cross-section with horizontal major axes, the outer fixed guide having zig-zag resonant slots 15 in the inner cylindrical wall, the inner rotatable guide having similar slots 20 in the outer cylindrical wall, and the radial distance between the slotted walls being an odd number of quarter wavelengths. The outer guide is mounted in a rectangular groove in the inner surface of a short cylindrical member 12 and the inner guide is mounted in a rectangular groove in the outer surface of a co-axial cylindrical member 17, annular end plates 13, 14 and 18, 19 being secured to the members 12 and 17 to enclose the annular space between the guides so that all the radiation emitted by the outer guide is received by the inner guide. To prevent leakage at the junction of the end plates, annular rings are provided having #/4 ditches 31. The outer guide 10 is fed at four quadrantally spaced points 21 by a branched system of wave-guides also of rectangular cross section, the transmitter being coupled to a wave-guide section 22 making a rightangled joint with a short section 23 which has an E-plane junction with a semi-circular guide 24 terminating in two E-plane junctions at the centres of two arcuate guides 25 which terminate in vertical sections leading to E-plane junctions with the radiating guide 10 at points 21. The inner guide 16 is coupled to a vertical guide 26 by an E-plane junction at one point on its periphery. In order to diffuse the energy transmitted between the outer and inner guides and thereby prevent modulation when rotation occurs, each slot in both guides is associated with a stub wave-guide 27 constituted by vertical radial plates extending between the end plates 13, 14 and 18, 19 respectively, the side plates of the stubs being flared to form horns 28 and the intersection of adjacent flared portions being extended by short radial vanes 29. The narrow dimension of the stubs must be small enough to suppress the mode polarized parallel to the wide dimension. When two rotary couplings as above are mounted coaxially, the axial space occupied by each coupling may be reduced by arranging the components 24 and 25 of the multiple feed in a common plane, Figs. 8 and 9 (not shown). In a modification, Figs. 5-7 (not shown), the two co-axial annular guides 10 and 16 are of equal diameter and are relatively displaced axially with their opposing narrow walls containing the slots; in this case the members 13, 14 and 18, 19 for confining the radiation comprise co-axial cylinders and the opposite walls of the stub wave-guides are parallel. Multiple or single feed may be used for either case. Figs. 4, 5 (not shown) and 6, 7 (not shown), of the first Provisional Specification, illustrate simplified forms of the two forms of rotary coupling described above in which the diffusing stub guides are omitted, the members for confining the radiation comprising two parallel discs or two coaxial cylinders respectively attached to the outer and lower annular guides. Specification 592,162 is referred to.