Dynamic EAS detection system and method
First Claim
1. A method for detecting an electronic article surveillance tag while reducing far field electromagnetic fields, said method comprising:
- providing an antenna structure having a plurality of antenna elements wherein each antenna element comprises a respective transmission driver for driving its respective antenna element to emit a respective electromagnetic field; and
driving each one of said transmission drivers with a respective transmission signal to generate a respective electromagnetic field vector and wherein a sum of said electromagnetic field vectors adds to zero regardless of said antenna structure and the number of said antenna elements, and wherein no vector is separated from another vector by 90°
or 180°
, said driving step comprising digitally-phase shifting said transmission signal and then digitally up-converting said transmission signal; and
receiving a plurality of receive signals from the tag that are digitally down-converted and then digitally-phase shifted.
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Accused Products
Abstract
This invention relates to dynamically controlled, electronic article surveillance (EAS) systems whereby an array of antenna elements is digitally phased and actively driven for concurrent transmission, and digitally phased and combined in the receiver unit to improve security tag detection. In particular, the individual frequency and phase of the plurality of the transmit/receive signals are rapidly varied to allow for automated manipulation (steering) of the transmit field pattern and receive field sensitivity. It is the object of this invention to achieve the following features via means of digital phasing and dynamic computer control: sufficient far-field cancellation, null-free detection and uncompromised detection performance regardless of tag'"'"'s orientation.
37 Citations
10 Claims
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1. A method for detecting an electronic article surveillance tag while reducing far field electromagnetic fields, said method comprising:
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providing an antenna structure having a plurality of antenna elements wherein each antenna element comprises a respective transmission driver for driving its respective antenna element to emit a respective electromagnetic field; and driving each one of said transmission drivers with a respective transmission signal to generate a respective electromagnetic field vector and wherein a sum of said electromagnetic field vectors adds to zero regardless of said antenna structure and the number of said antenna elements, and wherein no vector is separated from another vector by 90°
or 180°
, said driving step comprising digitally-phase shifting said transmission signal and then digitally up-converting said transmission signal; andreceiving a plurality of receive signals from the tag that are digitally down-converted and then digitally-phase shifted. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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Specification