LC resonant circuit with amplification device

• US 20050012615A1
• Filed: 04/30/2004
• Published: 01/20/2005
• Est. Priority Date: 05/01/2003
• Status: Active Grant

• Current Assignee: CHECKPOINT SYSTEMS, INC. (CCL Industries Incorporated)
• Original Assignee: CHECKPOINT SYSTEMS, INC. (CCL Industries Incorporated)
• Inventors: Piccoli, Anthony F., Appalucci, Lawrence, Mazoki, Gary T., Perez, David Lopez, SolerBonnin, Luis Francisco
• Granted Patent: US 7,129,843 B2
• Time in Patent Office: Days
• US Class Current: 340/572.100
• CPC Class Codes: G06K 19/07749 the record carrier being capable of non-contact communication, e.g. constructional details of the antenna of a non-contact smart card
• CPC Class Codes: G06K 7/10178 including auxiliary means for focusing, repeating or boosting the electromagnetic interrogation field comparable booster antennas integrated on the record carrier itself G06K19/07794
• CPC Class Codes: G08B 13/2414 using inductive tags
• CPC Class Codes: G08B 13/2431 Tag circuit details
• CPC Class Codes: H01Q 1/2225 used in active tags, i.e. provided with its own power source or in passive tags, i.e. deriving power from RF signal
• CPC Class Codes: H01Q 23/00 Antennas with active circuits or circuit elements integrated within them or attached to them
• 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

A security tag includes a combination of a resonant frequency circuit with an adjacent amplification shield for enhancing output signal amplitude. The amplification shield is located adjacent to the resonant frequency circuit and is preferably in the same or substantially the same plane as the resonant frequency circuit or is in a close, generally parallel plane. In an exemplary embodiment, the resonant frequency circuit includes an inductor electrically coupled to a capacitor. The resonant frequency circuit has a center frequency and is arranged to resonate in response to exposure to electromagnetic energy at or near the center frequency, providing an output signal having an amplitude. The amplification shield is arranged to direct a portion of the electromagnetic energy to the resonant frequency circuit to amplify the amplitude of the output signal from the resonant frequency circuit.

Claims

1. A resonant LC circuit device, comprising:

a resonant frequency circuit including an inductor electrically coupled to a capacitor, said resonant frequency circuit having a center frequency and arranged to resonate in response to exposure to electromagnetic energy at or near the center frequency, providing an output signal having an amplitude; and

an amplification shield adjacent said resonant frequency circuit, said amplification shield arranged to direct a portion of the electromagnetic energy to said resonant frequency circuit to amplify the amplitude of the output signal from the resonant frequency circuit.

2. The resonant LC circuit device of claim 1, wherein said amplification shield is passive.

3. The resonant LC circuit device of claim 1, wherein said amplification shield is substantially planar and metallic.

4. The resonant LC circuit device of claim 1, wherein said resonant frequency circuit includes a dielectric substrate having first and second surfaces on opposite sides thereof, said inductor including a conductive pattern on said first surface, said capacitor including first and second electrodes, said first electrode having a first conductive plate on said first surface coupled to said first conductive pattern, said second electrode having a second conductive plate on said second surface, said resonant frequency circuit further including a conductive trace electronically coupling said second conductive plate and said first conductive pattern.

5. The resonant LC circuit device of claim 4, wherein said amplification shield extends from one of said first conductive plate and said second conductive plate.

6. The resonant LC circuit device of claim 1, wherein said amplification shield includes a center portion having an aperture within which said resonant frequency tag is located.

7. The resonant LC circuit device of claim 6, wherein said amplification shield surrounds and is coplanar with said resonant frequency tag.

8. The resonant LC circuit device of claim 6, wherein said amplification shield has an outer edge and includes a slotted groove extending from said aperture to said outer edge to provide an open loop eliminating inductive short-circuiting of said inductor of said resonant frequency circuit.

9. The resonant LC circuit device of claim 1, wherein said amplification shield is substantially planer and has a generally polygon-shaped configuration.

10. The resonant LC circuit device of claim 1, wherein said amplification shield is substantially planer and has a generally circular shaped configuration.

11. The resonant LC circuit device of claim 1, wherein said amplification shield is substantially planer and includes two generally semicircular shaped metallic portions spaced apart to form a generally circular shaped configuration.

12. The resonant LC circuit device of claim 1, wherein said amplification shield includes a center portion having an aperture, said resonant frequency circuit located adjacent said aperture.

13. The resonant LC circuit device of claim 12, wherein said amplification shield overlaps said aperture.

14. The resonant LC circuit device of claim 1, wherein said amplification shield is located within said inductor.

15. The resonant LC circuit device of claim 1, including a central portion, said resonant frequency circuit being formed outside of said central portion, said amplification shield being positioned within said central portion so that said amplification shield is spaced apart from said resonant frequency circuit to amplify the amplitude of the output signal from the resonant frequency circuit.

16. The resonant LC circuit device of claim 15, wherein said amplification shield is generally coplanar to said resonant frequency circuit.

17. The resonant LC circuit device of claim 1, wherein said amplification shield is connected to said capacitor.

18. A resonant LC circuit device, comprising:

passive response means to resonate an output signal having an amplitude in response to exposure of said passive response means to electromagnetic energy at or near a desired frequency; and

passive amplification means to direct a portion of the electromagnetic energy to said passive response means to amplify the amplitude of the output signal.

19. A method for passively amplifying a response output signal from a LC circuit device, comprising

resonating an output signal having an amplitude from the resonant LC circuit device in response to exposure of the resonant LC circuit device to electromagnetic energy at or near a desired frequency;

and

directing a portion of the electromagnetic energy to the resonant LC circuit device to amplify the amplitude of the output signal.