Semi-transparent RFID tags

• US 20060250251A1
• Filed: 05/06/2005
• Published: 11/09/2006
• Est. Priority Date: 05/06/2005
• Status: Active Grant

• Current Assignee: Dominic M. Kotab
• Original Assignee: Intelleflex Corporation
• Inventors: Stewart, Roger Green
• Granted Patent: US 7,714,726 B2
• Time in Patent Office: Days
• US Class Current: 340/572.700
• CPC Class Codes: G06K 19/047 the record carrier being shaped as a coin or a gambling token
• CPC Class Codes: G06K 19/0702 the arrangement including a battery
• CPC Class Codes: G06K 19/07773 Antenna details antennas for wireless devices, e.g. RFID tags, in general H01Q1/22
• CPC Class Codes: G06K 7/10316 using at least one antenna particularly designed for interrogating the wireless record carriers antennas in general H01Q1/22
• 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

Abstract

A “semi-transparent” antenna and Radio Frequency (RF) device implementing the same. The semi-transparent antenna gathers some of the RF energy in a carrier signal, but most of the energy in the RF wave does not couple into the antenna. Accordingly, because the antenna minimally affects the electromagnetic RF fields surrounding the antenna even in the vicinity of the antenna, assemblies of objects carrying the RF devices can be formed while maintaining acceptable communications with the RF devices.

Claims

1. A Radio Frequency (RF) device, comprising:

a circuit; and

an antenna coupled to the circuit, wherein the antenna minimally affects electromagnetic RF fields surrounding the antenna even in the vicinity of the antenna.

2. The RF device of claim 1, wherein the circuit has an input impedance greater than an impedance of the antenna.

3. The RF device of claim 1, wherein the antenna has a sheet resistivity of greater than about 1 Ω

/sq.

4. The RF device of claim 1, wherein the antenna has a sheet resistivity of greater than about 10 Ω

/sq.

5. The RF device of claim 1, wherein a total impedance of the RF device presented to the RF wave is greater than about 1000 Ω

.

6. The RF device of claim 1, wherein a total impedance of the RF device presented to the RF wave is greater than about 10 KΩ

.

7. The RF device of claim 1, wherein a total impedance of the RF device presented to the RF wave is greater than about 100 KΩ

.

8. The RF device of claim 1, wherein a total impedance of the RF device presented to the RF wave is greater than about 100 KΩ

.

9. The RF device of claim 1, wherein the antenna is non-resonant.

10. The RF device of claim 1, wherein at least 50% of the RF energy striking the antenna passes through the antenna.

11. The RF device of claim 1, wherein the antenna is formed from a conducting polymer.

12. The RF device of claim 1, wherein the antenna is formed from a conductive paste having a sheet resistance of at least about 1 Ω

/sq.

13. The RF device of claim 1, wherein the antenna is formed from a metal having a sheet resistivity of at least about 1 Ω

/sq.

14. The RF device of claim 1, wherein the RF device is embodied on a Radio Frequency Identification (RFID) tag.

15. A Radio Frequency Identification (RFID) system, comprising:

an RFID tag implementing the RF device of claim 1;

and

an RFID reader in communication with the RFID tag.

16. A Radio Frequency (RF) antenna, comprising:

a planar conductor having a sheet resistivity of at least about 1 Ω

/sq.

17. A Radio Frequency (RF) device, wherein a total impedance of the RF device presented to the RF wave is greater than about 1000Ω

.

18. A wirelessly readable assembly of objects, comprising:

a plurality of objects arranged in close proximity to each other, each object having a Radio Frequency (RF) device coupled thereto, each RF device comprising;

a circuit; and

an antenna coupled to the circuit, wherein the antenna minimally affects electromagnetic RF fields surrounding the antenna,

wherein the circuit is capable of communicating with a remote device via RF signals.

19. The assembly of objects of claim 18, wherein the objects are poker chips.

20. The assembly of objects of claim 18, wherein the objects are documents.

21. The assembly of objects of claim 18, wherein the objects are designed to be stacked, wherein each of the objects has an average thickness, defined between ends thereof adapted for abutting adjacent objects, of less than about ¼

inch.

22. The assembly of objects of claim 18, wherein the assembly of objects includes at least 3 of the objects.

23. A Radio Frequency Identification (RFID) system, comprising:

the assembly of objects of claim 18;

and

an RFID reader in communication with the objects.

24. A method for identifying each object in an assembly of objects, comprising:

sequentially communicating with each of a plurality of Radio Frequency (RF) devices coupled to objects, wherein the objects are oriented in close proximity with each other such that an RF carrier wave must pass through a radar profile of at least one of the RF devices to reach at least one other of the RF devices.

25. The method of claim 24, wherein the objects are stacked.

26. The method of claim 24, wherein the RF carrier wave must pass through an antenna of the at least one of the RF devices to reach the at least one other of the RF devices.

27. The method of claim 24, wherein the method is performed by an RFID system.

28. A plurality of RFID tagged objects wherein an operating range of the objects varies by less than 50% even when said objects are positioned directly adjacent each other.