Patent GB-677457-A (GB)
Title: Method and device for focussing of radiations by means of stationary reflector and refractor gratings
IPC: H01Q19/00
Filed: 1949-12-03
Abstract: 677,457. Aerials. PILLOT DE COLIGNY, G. DE. Dec. 3, 1949 [Dec. 4, 1948], No. 31103/49. Class 40 (vii). A device for reflecting or refracting waves of radiant energy comprises, as appropriate, a plurality of portions of paraboloidal reflectors or of hyperboloidal refractors having a common focus and axis and so arranged with respect to one another that the aberration normally occurring for off-axial positions of a primary radiator is substantially obviated. The invention is particularly applicable to systems employing linearly or conically scanning beams of radio waves, wherein a primary radiator is oscillated in the vicinity of the focus of a reflector or refractor of radio waves. Fig. 1 illustrates a radio-wave reflector comprising a plurality of portions 31-36 of a family of paraboloids, the portions selected being those lying on and adjacent to a curve 20, the formula for which is derived in the Specification. The primary radiator 15 is oscillated about an axis 17 over an arc passing through the common focus 7 to the paraboloids. In the case illustrated the axis 17 does not intersect the common axis 8 to the paraboloids; in the case when the two axes do intersect the curve 20 degenerates into a circle. The paraboloids are successively spaced apart by a half-wave- 'length at the frequency of operation along the axis 8 so that the radiation is reflected from individual elements to form a cophasal wavefront. Fig. 5 shows a practical construction of reflector, the reflecting elements being supported by wooden mounting members. The complete aerial system is shown in Fig. 4, the primary radiator comprising a vertical slot 55 fed from a movable wave-guide 60 connected to a fixed guide 59 via a rotating joint 61. The guide 60 is put into oscillatory motion by means of continuous rotation of a wheel 63. A screen 39 is arranged in front of the slot 55 to prevent radiation over the arc 58. In an alternative embodiment, Figs. 14, 15 and 16 (not shown), the reflector elements are portions of paraboloidal cylinders and the primary element comprises the virtual image of a point source produced by a further paraboloidal-cylindrical mirror disposed perpendicularly to the first cylindrical elements so that the focusing in two perpendicular directions is obtained separately. Figs. 12 and 13 (not shown), illustrate a waveguide-fed reflector wherein the open end of the waveguide follows a spiral curve to produce a spiral scanning beam. Fig. 17 (not shown), illustrates the formation of a refractor according to the invention. The refractor comprises a plurality of annular elements forming parts of convex-plano lenses, having convex surfaces facing the primary radiator 15 which are portions of successive members of a family of hyperboloids. The elements all lie on or adjacent to a curve 320, the formula for which is derived, intersecting the family of hyperboloids. In the example shown, wherein the rotation axis 17 lies on the axis 8 of the family of hyperboloids, the curve 320 degenerates into a circle. Specification 677,460 is referred to.