| 摘要 |
1,113,664. Aerials; radar. HITACHI SEISAKUSHO KABUSHIKI KAISHA. 22 April, 1965 [30 April, 1964 (2); 16 June, 1964; 24 June, 1964; 29 June, 1964], No. 17060/65. Headings H4A and H4D. An arrangement for detecting the presence of an obstacle in the path of a vehicle includes a directive waveguide aerial having at least one leaky slot, the leaky waves are directed across that path and reflections by the obstacle and/or reflecting means on the remote side of the path re-enter the waveguide to constitute a signal for obstacle detection. The leaky waveguide aerial may be a spaced helix of a single conductor, or a parallel winding of several conductors, provided with a dielectric matching layer and with an enveloping metallic shield incorporating slots of variable sizes and spacings to permit variation of the radiated beam axis relative to the longitudinal axis of the helix and to permit variation of leakage magnitude; a horn concentrates the beam in the horizontal plane. The reflecting means may be a corrugated plate with the corrugations so orientated and dimensioned to reflect energy back to the leaky waveguide such that it travels back to the transmitting end of the waveguide but is of reduced amplitude when an obstacle is present. A common reflector may be used for a double-track railway, which also need have only one leaky waveguide, between the two tracks, if reflectors are placed at the two boundaries. The preferred leaky waveguide structure is the subject-matter of Specification 1,113,665. |
