Communications: electrical – Condition responsive indicating system – Specific condition
Reexamination Certificate
2000-04-03
2002-03-12
Tweel, John A. (Department: 2632)
Communications: electrical
Condition responsive indicating system
Specific condition
C340S572500
Reexamination Certificate
active
06356197
ABSTRACT:
CROSS REFERENCES TO RELATED APPLICATIONS
Not Applicable
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to electronic article surveillance and electronic article identification devices, and more particularly to an electronic article surveillance tag that includes electronic article identification, and an associated system and method.
2. Description of the Related Art
It is well known to provide electronic article surveillance (EAS) systems to prevent or deter unauthorized removal of articles from a controlled area. In a typical system, tags designed to interact with an electromagnetic field located at the exits of the controlled area are attached to articles to be protected. If a tag is brought into the field or “interrogation zone”, the presence of the tag is detected and appropriate action is taken, such as generating an alarm.
There are several types of EAS systems presently available that detect EAS tag signals by harmonic or field disturbance detection. U.S. Pat. No. 3,810,147 discloses an EAS marker or tag that includes an LC resonant circuit. The tag is typically interrogated by transmitting a swept frequency including the resonant frequency of the tag. The tag is detected by a receiver in the interrogation zone that detects a change in the interrogation field at the tuned frequency due to the resonance of the LC circuit. Manufacturing a tag with a precise resonant frequency requires stringent manufacturing tolerances, which can result in a more expensive tag. To manufacture a more affordable tag, manufacturing tolerances are relaxed resulting in a resonant frequency that may shift slightly from tag to tag. To interrogate the more affordable tags with variances in resonant frequency, a swept frequency is transmitted, which can require higher power usage than transmitting a discrete frequency.
An improved tag and associated EAS system utilizes an LC resonant circuit that includes a magnetic material that exhibits a “giant magneto-impedance” (GMI) effect when exposed to a magnetic field. As fully described hereinbelow, a GMI effect is a substantial change in impedance of the magnetic material when exposed to a magnetic field. The magnetic material can be a wire or ribbon and is connected to the LC circuit by soldering, plating, or etching to form part of the circuit. Additional information on magneto-impedance material can be found in a various published sources, such as U.S. Pat. No. 5,994,899.
A transmitted low frequency magnetic field interacts with the magnetic material to produce the GMI effect. The GMI effect due to the magnetic field causes the impedance of the magnetic material to change. The change in impedance of the material changes the resistance of the material causing the quality factor (Q) of the LC circuit to change. The change in Q results in a change in the output level of the LC circuit at resonance. In effect, the LC circuit and magnetic material modulate the transmitted resonant or carrier frequency with the low frequency magnetic field. The tag thus produces sidebands of the resonant frequency, which can be detected by suitable detection equipment.
The tag is interrogated by simultaneously transmitting a first signal at the LC circuit's tuned resonance frequency and a second signal comprising a low frequency alternating magnetic field. Because of the magnetic material, the tag mixes the resonant “carrier” frequency and the low frequency magnetic field, forming sidebands of the resonant frequency that can be detected by a suitable EAS receiver.
Sideband detection is an improvement over harmonic or field disturbance detection. In the detection of harmonics or a change in the fundamental, the carrier signal itself is a source of noise. The signals that are being detected are small, so even a small amount of carrier noise masks the desired signal. With sideband detection, the carrier frequency is not a noise source that masks detection of the sidebands. In addition to the sideband generating tag described above, U.S. Pat. No. 4,736,207, discloses a microwave tag which includes a tuned dipole antenna and a nonlinear circuit device that mixes two interrogate signals and re-radiates the first signal modulated by the second signal.
In addition to EAS, there is presently a desire to expedite and facilitate the removal of articles from controlled areas by gathering identification data about the article. As used herein, identification data means any data to be gathered, stored, or used pertaining to an article or object to be protected, monitored, retained, sold, inventoried, or otherwise controlled or distributed in some manner. For example, retail establishments desire to gather information pertaining to article identification, price, and pertinent inventory control data. Presently, bar codes provide some of this type of data. However, bar codes can only provide a small amount of read only data, and the bar code reader or scanner must be visually aligned with the bar code to properly read the bar code attached to the article, slowing the checkout or inventory process.
Radio frequency identification (RFID) utilizes radio frequency (RF) interrogation and reply frequencies to perform electronic article identification (EAI) functions. In RFID, a tag that responds with RF identification information, in response to an RF interrogation signal, is attached to an article to be identified. At present, RFID tags are well suited to provide article identification information, pricing information, inventory control, and can receive and store information such as the date and place of sale, sales price, and article manufacturing authenticity information. However, RFID tags are not well suited to EAS applications because of limited detection range as well as being prone to shielding and detuning when proximate certain materials, which can result in missed EAS detection. Presently EAS tags and RFID tags must both be attached to an article if identification and protection of the article are desired.
U.S. Pat. No. 5,859,587 discloses an RFID and EAS tag integrated within the same tag housing. The RFID and EAS functions in the '587 disclosure are electrically separate, discrete functions that are located within one enclosure. There is presently a desire for a tag that combines both EAS and EAI functions.
BRIEF SUMMARY OF THE INVENTION
In accordance with the present invention, there is provided an electronic article surveillance and identification tag and system. In a first aspect of the present invention, the tag couples energy from a radiated energy source, which includes first and second radiated signals. A mixing member in the tag mixes the first and second signals to produce a sideband of the first signal, which is re-radiated by the tag. A controller switches the mixing member into and out of the circuit according to a code stored within the controller that is associated with an article to be identified. As the mixing member is switched in and out, the sideband produced by the tag will be radiated in a sequential manner according to the stored code. A receiver detects the sideband, and a decoder recovers the stored code according to the sequence of received sideband emissions from the tag.
Radiated energy received by the tag provides power for the controller. As long as the controller is powered, the tag will continue to re-radiate the generated sideband in a sequence corresponding to the stored data code. When the coupled energy drops below a pre-selected minimum level, the controller becomes deactivated. When the controller is deactivated, the mixing member remains in the circuit and continues to mix the first and second signals to produce the sideband. The sideband is continually generated and re-radiated until the tag is removed from the radiated energy field. The tag thus performs as an EAS tag and an EAI tag when the coupled energy is above a pre-selected minimum level, and continues to perform as an EAS tag when the coupled energy drops below the pre-
Lian Ming-Ren
Patterson Hubert A.
Comoglio Rick F.
Kashimba Paul T.
Sensormatic Electronics Corporation
Tweel John A.
LandOfFree
Electronic article surveillance and identification device,... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Electronic article surveillance and identification device,..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Electronic article surveillance and identification device,... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2871557