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US Patent 5349332 - EAS system with requency hopping
US Patent Issued on September 20, 1994
Estimated Patent Expiration Date:
October 13, 2012Estimated 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.
Estimated Patent Expiration Date:
October 13, 2012Estimated 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.AbstractAn EAS system in which a transmitter transmits an RF transmitter signal into an interrogation zone and a receiver receives RF signals from the interrogation zone. The received RF signals include any RF tag signals generated by tags situated in the zone and adapted to respond to the RF transmitter signal. In order to reduce interference effects, the RF carrier frequency of the transmitter signal is adapted to take on a plurality of different frequency values during different ones of a plurality of finite dwell time periods of the RF transmitter signal.Other References
| InventorsAssigneeApplicationNo. 959685 filed on 10/13/1992US Classes:340/572.2, Specified relationship between field and detection frequencies (e.g., nth order harmonics)340/551, Disturbance of magnetic field340/572.4Specified processing arrangement for detected signalField of Search340/551Disturbance of magnetic fieldExaminersPrimary: Swann, GlenAttorney, Agent or FirmUS Patent References3868669, 4063229, Article surveillanceIssued on: 12/13/1977 Inventor: Welsh , et al.4139844, Surveillance method and system with electromagnetic carrier and plural range limiting signals Issued on: 02/13/1979 Inventor: Reeder4212002, Method and apparatus for selective electronic surveillance Issued on: 07/08/1980 Inventor: Williamson4352098, Surveillance systems Issued on: 09/28/1982 Inventor: Stephen , et al.4356477, FM/AM Electronic security system Issued on: 10/26/1982 Inventor: Vandebult4429302, Electronic security system with noise rejection Issued on: 01/31/1984 Inventor: Vandebult4642640, Signal receptor-reradiator and surveillance tag using the same Issued on: 02/10/1987 Inventor: Woolsey , et al.4736207, Tag device and method for electronic article surveillance Issued on: 04/05/1988 Inventor: Siikarla , et al.5109217Method and apparatus for enhancing detection of electronic article surveillance tags in close proximity to electrically conductive objects Issued on: 04/28/1992 Inventor: Siikarla, et al. International ClassG08B 013/187 |
