| 摘要 |
782,042. Aerials. COMPAGNIE GENERALE DE TELEGRAPHIE SANS FIL. Nov. 16, 1955 [Nov. 18, 1954], No. 32801/55. Class 40 (7). An aerial system for the radiation or reception to or from the same direction of energy on two frequencies comprises two different primary elements for the respective frequencies mounted on opposite sides of a device which acts as a mirror for energy of the lower frequency and as a lens for energy of the higher frequency. The device may be constructed in the form of a number of perforated plates as described in Specification 689,408. These plates may be substantially parallel and paraboloidal with a common axis z. The plate nearest the element F2 acts as a mirror for waves of one of the frequencies and has feed F2 at the mirror focus. All the plates are provided with holes in a square lattice pattern, the sides of the lattice being smaller than the shortest wavelength to be transmitted. They act as a lens in respect of the higher frequency energy and a second primary element F1 is placed at the lens focus. The primary elements may be radiating horns or dipoles and the device may be so constructed that the primary element F2 can be off-set out of the path of the beam (Fig. 2, not shown). In another modification the plates are parabolic and doublets excited from a coaxial line are arranged along the focal axis to form the element F2 (Fig. 4, not shown). For manufacturing convenience the shaped plates of the device may be made up from a plurality of plane elements. The aerial system may be used in an object detection system in which it is desired to radiate search and interrogation signals of differing frequencies at the same time. The energy radiated may be amplitude, frequency, or pulse modulated.
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