| 摘要 |
755,011. Aerials. STANDARD TELEPHONES & CABLES, Ltd. July 25, 1952 [Aug. 3, 1951], No. 18390/51. Class 40 (7). Directive aerial systems required to produce narrow beams for radio link or radar purposes include iris systems consisting of energy absorbing means cutting off and absorbing radiation from the primary element directed in undesired directions. The primary element may be situated at the focal point of a concave mirror 3 and energy from it directed vertically through the apertures in three iris units 5, 6 and 7 before being directed by reflector 4 in the required direction. The lowest iris 5 is preferably of hemispherical shape 5a but may be conical 5b; it is placed to cut off all radiation except that passing through aperture 8 in a substantially vertical direction. Dish-shaped iris 6 and substantially flat iris 7 are added to further improve the beam. The energy absorbing surfaces of the iris units are mounted on a rigid backing of metal or wood 11. The surface itself consists of a honeycomb structure of dissipating waveguides 15. The guides are an odd multiple of a quarter of the working wavelength long and formed of, or coated with, high-loss material. The ends of the tubes are sealed by layers 16 and 17 of the same material and the surface not supported by the backing 11 given a layer of varnish 13. The aerial system may be used for transmission or reception. If it is to be used for reception the outer (backing) surface of the iris units should be metal, so as to act as a reflector, except immediately surrounding the aperture where energy absorbing material is preferred to prevent eddy currents. |
