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RADIO FREQUENCY INTRUSION DETECTION SYSTEM

  • US 3,794,992 A
  • Filed: 02/07/1972
  • Issued: 02/26/1974
  • Est. Priority Date: 02/07/1972
  • Status: Expired due to Term
First Claim
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1. A radio frequency intrusion detection system for detecting the presence of an intruding object in a radio frequency radiation field adapted to be produced by a radio frequency transmitting source, which comprises a receiving antenna disposed remotely from the transmitting source of said radiation field at such a distance that the capacitative and inductive coupling from the source is insignificant at the radiation field frequency, said antenna being disposed below the surface of the terrain upon which said radiation field is incident and to which said field is coupled when said object is in proximity to said antenna, and receiver means connected to said antenna and responsive to radio frequency signals generated in said antenna by said radiation field when coupled to said antenna by said object for providing an output indicative of the presence of said object.

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