Shielded balanced loop antennas for electronic security systems
Patent 4251808 Issued on February 17, 1981. Estimated Expiration Date: 
November 15, 1999. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
November 15, 1999. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent References 3810147 3863244 A multi-frequency resonant tag circuit for use with an electronic security system having improved noise discrimination Patent #: 3967161 InventorApplicationNo. 06/094429 filed on 11/15/1979US Classes:340/572.7, Specified antenna structure343/842Loop-type antennaExaminersPrimary: Swann, III, Glen R.Attorney, Agent or FirmInternational ClassesG08B 13/24 (20060101)H01Q 7/04 (20060101) H01Q 7/00 (20060101) AbstractFor use in an electronic security system for detection of a resonant tag, an antenna system has a transmitting antenna and a receiving antenna at least one of which includes two or more twisted loops lying in a common plane with each loop being twisted 180° to be in phase opposition, and a conductive shield enclosing each twisted loop antenna. The conductive shield has a grounded shorted turn portion enclosing the periphery of the antenna, and a shield portion enclosing the crossed conductors of each pair of twisted loops, this latter shield portion being insulated from the shorted turn portion to prevent current flow in the crossover shield portion. | |
