Communications: electrical – Condition responsive indicating system – Specific condition
Reexamination Certificate
1999-12-27
2001-08-07
Trieu, Van T. (Department: 2632)
Communications: electrical
Condition responsive indicating system
Specific condition
C340S568100, C340S572100
Reexamination Certificate
active
06271756
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to electronic article security (EAS) systems for detecting the presence of a security tag within a security zone and more particularly to an improved electronic article security system having the capability for localizing a resonant security tag within a portion of the security zone.
The use of electronic article security systems for detecting and preventing theft or unauthorized removal of articles or goods from retail establishments and/or other facilities such as libraries has become widespread. In general, such EAS systems employ a security tag, which is detectable by the EAS system and which is secured to the article to be protected. Such EAS systems are generally located at or around points of exit irom such facilities to detect the security tag, and thus the article, as it transits through the exit point.
Due to environmental and regulatory considerations, individual EAS systems are generally effective over only a limited area in which a security tag attached to a protected article may be reliably detected. Such area, typically referred to as a security zone, is generally limited to about six feet in width for a single EAS system. While many stores and libraries have only a single exit doorway of a size commensurate with such a six foot wide security zone, many other retail establishments have eight or ten exit doorways arranged side by side. Furthermore, large mall stores frequently have a generally wide open area or aisle of ten feet or more in width serving as a connection with the mall. Thus, in many such situations, a plurality of EAS systems are required to fully protect exit/entrance points having a width greater than that which can be reliably protected by a single EAS system.
In a large mall entryway that needs to be protected, it is likely that the store owner will not want to employ a traditional EAS system installation which would include multiple, large, side-side “pedestal” antenna structures, due to aesthetic visual or marketing reasons. Such store owners would prefer an “invisible” EAS system in which the EAS antenna structure is mounted in the floor beneath the entryway, hung over the entryway or both. Such EAS systems usually provide adequate detection of tagged merchandise transiting through the security zone but fail to provide a localization of a detection to a specific portion of the security zone. Thus, when many customers are in proximity of the entryway when an alarm is activated, store personnel generally have no way, other than trial and error, to determine which customer has set off an alarm with the tagged merchandise. This leads to either a lack of use of the EAS system as an effective security aid, or the owner having disgruntled customers who take their business elsewhere.
The present invention overcomes the problem of an “invisible” EAS system not being able to localize a tag detection to a specific portion of the security zone in a large entryway by utilizing a plurality of EAS sensors of the pulse-listen type, in combination with a plurality of antennas placed either above or below the entryway. The resulting EAS system determines the relative proximity of a detected security tag transiting through the security zone to each of the plurality of antennas in the array. The resulting EAS system achieves localization of a security tag to within a small portion of the security zone.
BRIEF SUMMARY OF THE INVENTION
Briefly stated the present invention provides a security tag detection and localization system for detecting a resonant security tag in a security zone comprising a plurality of detection zones, and generating an alarm signal localizing the resonant security tag to a detection zone. The system comprises: an antenna array for radiating interrogation signals and receiving response signals, the antenna array forming at least one of an upper and a lower boundary of the security zone and being arranged horizontally across a width and a length of the security zone, wherein the antenna array comprises at least two antennas, the antennas forming one of the upper and lower boundaries being disposed side-by-side in a single horizontal plane, each antenna being electromagnetically coupled to one of the detection zones; at least one electronic article security (EAS) sensor for transmitting interrogation signals to the antenna array, receiving response signals from the antenna array and generating an alarm signal; and an annunciator connected to each EAS sensor, for receiving the alarm signal and indicating a detection zone corresponding to the alarm.
In accordance with another aspect of the present invention there is an EAS sensor of the pulse-listen type for detecting and localizing a resonant security tag to a specific portion of a security zone comprising: a transmitter for generating an interrogation signal; a receiver for receiving a response signal from the security tag; a plurality of transmitting antennas for receiving the interrogation signal from the transmitter and radiating the interrogation signal into the security zone; a plurality of receiving antennas for receiving the response signal from the security tag and providing the response signal to the receiver, the response signal being a result of the interrogation signal interacting with the security tag and being re-radiated from the security tag; and an antenna switch connecting the transmitter to the transmitting antennas and the receiver to the receiving antennas, the antenna switch sequentially selecting pair-wise permutations, with replacement, of the antennas once over a predetermined time interval, such that each selected pair consists of one transmitting antenna and one receiving antenna, wherein an amplitude of an output from the receiver resulting from each permutation of the antennas is compared, thereby determining the location of the security tag to correspond with the portion of the security zone being in closest proximity to the antenna pair having the receiver output signal with the largest amplitude.
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patent: 6094173 (2000-07-01), Nylander
Davies, Jr. John E.
Eckstein Eric A.
Hopton, Jr. Edwin H.
Richie, Jr. William S.
Akin Gump Strauss Hauer & Feld L.L.P.
Checkpoint Systems Inc.
Trieu Van T.
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