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US Patent 5349332 - EAS system with requency hopping

US Patent Issued on September 20, 1994
Estimated Patent Expiration Date: Icon_subject 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.
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Abstract

An 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

  • Schilling, Donald L. et al., "Spread Spectrum Goes Commercial" IEEE Spectrum, Aug. 199

Inventors

Assignee

Application

No. 959685 filed on 10/13/1992

US 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 signal

Field of Search

340/551Disturbance of magnetic field

Examiners

Primary: Swann, Glen

Attorney, Agent or Firm

US Patent References

3868669, 4063229, Article surveillance
Issued 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: Reeder
4212002, Method and apparatus for selective electronic surveillance
Issued on: 07/08/1980
Inventor: Williamson
4352098, Surveillance systems
Issued on: 09/28/1982
Inventor: Stephen ,   et al.
4356477, FM/AM Electronic security system
Issued on: 10/26/1982
Inventor: Vandebult
4429302, Electronic security system with noise rejection
Issued on: 01/31/1984
Inventor: Vandebult
4642640, 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 Class

G08B 013/187

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