DYNAMIC EAS DETECTION SYSTEM AND METHOD

• US 20080303673A1
• Filed: 06/06/2008
• Published: 12/11/2008
• Est. Priority Date: 06/08/2007
• Status: Active Grant

• Current Assignee: CHECKPOINT SYSTEMS, INC. (CCL Industries Incorporated)
• Original Assignee: CHECKPOINT SYSTEMS, INC. (CCL Industries Incorporated)
• Inventors: Zeng, Kefeng, Oung, Harry
• Granted Patent: US 8,587,489 B2
• Time in Patent Office: Days
• US Class Current: 340/572.7
• CPC Class Codes: H01Q 1/2216 used in interrogator/reader equipment
• CPC Class Codes: H01Q 19/134 Rear-feeds; Splash plate feeds
• CPC Class Codes: H01Q 3/26 varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture H01Q3/12, H01Q3/22, H01Q3/24 take precedence
• CPC Class Codes: H01Q 7/00 Loop antennas with a substantially uniform current distribution around the loop and having a directional radiation pattern in a plane perpendicular to the plane of the loop

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.

Claims

1. An electronic article surveillance system comprising an antenna structure including three or more loops each connected to an independent transmission driver for generating a corresponding electromagnetic field wherein said transmission drivers are arranged to drive the loops in such a way that a vector sum of said electromagnetic fields of said independent transmission drivers is null in a far field and wherein no vector is separated from another vector by 180°

of phase.

2. The system of claim 1 wherein the transmission signals are digitally synthesized.

3. The system of claim 1 wherein the transmission signals are varied in phase relative to one another.

4. The system of claim 1, the antenna structure further comprising an electromagnetic core structure about which the loops of the antenna structure are wound.

5. The system of claim 4 wherein the electromagnetic core comprises either ferrite ceramic material or a composite ferrous and insulating material.

6. A dynamically controlled electronic article surveillance system for detecting security tags wherein an array of antenna elements is digitally phased and actively driven for concurrent transmission to generate a plurality of electromagnetic fields having respective vectors and wherein said system changes the phases between each of said vectors for interacting with security tags for effecting tag detection.

7. The system of claim 6 automatically steering said electromagnetic fields and scanning associated frequencies by rapidly varying an individual frequency and phase of a plurality of transmitted and received security tag signals via means of computer control.

8. The system of claim 6 further comprising a transmitter unit which drives concurrently a plurality of antennas, a receiver unit that processes and combines any received signals from the security tags, and a computer unit whereby both said transmitter unit and said receiver unit are dynamically controlled.

9. The system of claim 6 whereby an antenna structure for a wide aisle configuration comprises an even number of antenna elements arranged to form a pedestal pair such that half of the elements having a phase shift between 0°

are 180°

are located coplanar on one side of an exit aisle while another half of said antenna elements having a phase shift between 180°

are 360°

are located coplanar on said other side of the exit aisle.

10. The system of claim 7 wherein said plurality of transmitted and received security tag signals are digitally phased and dynamically controlled to create a circularly polarized helical RF field.