U.S. patents available from 1976 to present.
U.S. patent applications available from 2005 to present.

EAS system with requency hopping

Patent 5349332 Issued on September 20, 1994. Estimated Expiration Date: Icon_subject October 13, 2012. 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

3868669

Article surveillance
Patent #: 4063229
Issued on: 12/13/1977
Inventor: Welsh ,   et al.

Surveillance method and system with electromagnetic carrier and plural range limiting signals
Patent #: 4139844
Issued on: 02/13/1979
Inventor: Reeder

Method and apparatus for selective electronic surveillance
Patent #: 4212002
Issued on: 07/08/1980
Inventor: Williamson

Surveillance systems
Patent #: 4352098
Issued on: 09/28/1982
Inventor: Stephen ,   et al.

FM/AM Electronic security system
Patent #: 4356477
Issued on: 10/26/1982
Inventor: Vandebult

Electronic security system with noise rejection
Patent #: 4429302
Issued on: 01/31/1984
Inventor: Vandebult

Signal receptor-reradiator and surveillance tag using the same
Patent #: 4642640
Issued on: 02/10/1987
Inventor: Woolsey ,   et al.

Tag device and method for electronic article surveillance
Patent #: 4736207
Issued on: 04/05/1988
Inventor: Siikarla ,   et al.

Method and apparatus for enhancing detection of electronic article surveillance tags in close proximity to electrically conductive objects Patent #: 5109217
Issued on: 04/28/1992
Inventor: Siikarla, et al.

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

Examiners

Primary: Swann, Glen

Attorney, Agent or Firm

International Class

G08B 013/187

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
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