Patent GB-660034-A (GB)
Title: Improvements in antennas of the solid dielectric type
IPC: H01Q13/28
Filed: 1949-01-07
Abstract: 660,034. Aerials. RADIO CORPORATION OF AMERICA. Jan. 7, 1949 [Jan. 7, 1948], No. 566/49. Class 40 (vii). An antenna for U.H.F. comprises an elongated body of solid dielectric for guiding energy to be transmitted therefrom having localized parts of different electrical properties from those of the dielectric, thereby causing radiation from spaced points along the dielectric body. The non-directional embodiment of Fig. 1 comprises a polystyrene rod 10 having a diameter between # and ¢ of the free space wavelength and crossed dipoles inserted in transverse holes drilled in the rod 10 at distances of the order of one wavelength along the rod, circularly polarized energy being fed into the rod as indicated by the arrow. If a plane polarized transverse wave is fed in at the bottom of the rod the radiation pattern will be directional and steerable according to the relation between the planes of the polarization and dipoles. In the embodiment of Fig. 2 directional radiation is obtained by short wires 22 (somewhat less than 5# long) inserted in a rectangular dielectric rod 20 and spaced apart of the order of A. The wires may be shorter near the source of power or inserted for varying distances from the central axis of the rod so that each radiates the same amount of power. A metal bar 30 having a non-circular outer surface is rotated near one face of the dielectric rod 20 to vary the speed of propagation of energy within the rod in a cyclic manner and thereby cause scanning over a small angle. This arrangement is compact and suitable for highspeed scanning and may be fitted easily into the wing of an airplane. If it is desired to direct all the energy into a beam from one side of the rod only a metal plate may be attached to the side of the rod so as to lie parallel to, and  # away from, the plane of the short wires 22, as in Fig. 3 (not shown). The modification of Fig. 4 (not shown), comprises two rows of short wires 22, ¢ # apart and staggered by a distance equal to half a wavelength within the dielectric. Instead of inserting metal wires the discontinuities in the dielectric rod may comprise holes drilled therein as in Fig. 5 (not shown). An alternative construction is shown in Fig. 6 wherein a dielectric tube 61 contains metal spheres 62 spaced by dielectric plugs 64 to be # apart centre-to-centre. All these embodiments are broadside antennµ and not end-fire type. A further scanning array is shown in Fig. 7, where a dielectric sheet 70 having a curved edge 71 supports a large number of radiating wires 75 in holes drilled in one flat surface of the sheet. The curved edge of the sheet is placed between two parallel metal plates 72 which constitute a thin wave-guide section for coupling between the main wave-guide WG and the dielectric sheet. The curved edge acts as a lens to make the wavefront entering the dielectric approximately straight, giving lines of equal phase such as 74, on which the radiating wires 75 are inserted. As indicated more clearly in Fig. 8 (not shown), wires are bent at right-angles after emerging from the surface of the sheet to radiate in a direction perpendicular to the plane of the sheet. A second set of wires 76 may be inserted at points differing in phase by 180 degrees from the points where the wires 75 are inserted, their ends being bent over in the opposite direction to those of wires 75. Scanning is obtained by swinging the wave-guide WG as indicated by the arrow S, causing the equi-phase lines 74 to be tilted with respect to the lines of radiators 75 and 76.