| 摘要 |
758,957. Directive radio systems. BRITISH THOMSON-HOUSTON CO., Ltd. March 22, 1955 [March 23, 1954], No. 8483/54. Class 40 (7). An aerial system comprises a pair of primary elements located adjacent to each other and capable of transmitting and/or receiving electromagnetic energy of different wavelengths and having mutually perpendicular polarizations together with two reflectors, one designed to co-operate with each primary element, the reflectors being located one behind the other and the one nearest the elements being constructed to reflect energy of one polarization and pass energy of the other polarization used. The system may be used in a duplex signalling or radar arrangement and provides a smaller and more readily movable device for such arrangements where operation on two different wave. lengths is required than can be achieved by the use of two separate aerials. The reflectors may be of the " cheese " type or of paraboloidal or other form and it is desirable that they should be designed for offset feeding so that the primary elements are not in the path of the emergent beams. The rear reflector may conveniently be of sheet-metal construction whilst the front one may be a grid of parallel spaced wires. It is pointed out that for the best effect it is desirable to use a large ratio of focal length to aperture for the reflectors so that the polarization of the energy incident on the wire grid is everywhere substantially parallel or perpendicular, as the case may be, to the wires. The aerial system may be constructed as a unitary structure which may be rotated or oscillated to scan the beams. In some cases the reflectors may be fixed and the radiators moved independently. |
