RFID tag with tunable antenna and associated reader

• US 20050104790A1
• Filed: 11/30/2004
• Published: 05/19/2005
• Est. Priority Date: 08/15/2002
• Status: Active Grant

• Current Assignee: Symbol Technologies, LLC (Zebra Technologies Corporation)
• Original Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Inventors: Duron, Mark William
• Granted Patent: US 7,339,481 B2
• Time in Patent Office: Days
• US Class Current: 343/745
• CPC Class Codes: G06K 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs
• CPC Class Codes: G06K 19/0726 the arrangement including a circuit for tuning the resonance frequency of an antenna on the record carrier
• CPC Class Codes: G06K 19/07771 the record carrier comprising means for minimising adverse effects on the data communication capability of the record carrier, e.g. minimising Eddy currents induced in a proximate metal or otherwise electromagnetically interfering object
• CPC Class Codes: H01L 21/76229 Concurrent filling of a plurality of trenches having a different trench shape or dimension, e.g. rectangular and V-shaped trenches, wide and narrow trenches, shallow and deep trenches
• CPC Class Codes: H01L 21/76232 of trenches having a shape other than rectangular or V-shape, e.g. rounded corners, oblique or rounded trench walls H01L21/76229 takes precedence
• CPC Class Codes: H01L 21/76264 SOI together with lateral isolation, e.g. using local oxidation of silicon, or dielectric or polycristalline material refilled trench or air gap isolation regions, e.g. completely isolated semiconductor islands
• CPC Class Codes: H01L 21/823418 with a particular manufacturing method of the source or drain structures, e.g. specific source or drain implants or silicided source or drain structures or raised source or drain structures
• CPC Class Codes: H01L 21/823437 with a particular manufacturing method of the gate conductors, e.g. particular materials, shapes
• CPC Class Codes: H01L 21/823481 isolation region manufacturing related aspects, e.g. to avoid interaction of isolation region with adjacent structure
• CPC Class Codes: H01L 21/823814 with a particular manufacturing method of the source or drain structures, e.g. specific source or drain implants or silicided source or drain structures or raised source or drain structures
• CPC Class Codes: H01L 21/823828 with a particular manufacturing method of the gate conductors, e.g. particular materials, shapes
• CPC Class Codes: H01L 29/1083 with an inactive supplementary region, e.g. for preventing punch-through, improving capacity effect or leakage current
• CPC Class Codes: H01L 29/41783 Raised source or drain electrodes self aligned with the gate
• CPC Class Codes: H01L 29/66545 using a dummy, i.e. replacement gate in a process wherein at least a part of the final gate is self aligned to the dummy gate
• CPC Class Codes: H01L 29/66583 with initial gate mask or masking layer complementary to the prospective gate location, e.g. with dummy source and drain contacts
• CPC Class Codes: H01L 29/66628 recessing the gate by forming single crystalline semiconductor material at the source or drain location
• CPC Class Codes: H01L 29/66636 with source or drain recessed by etching or first recessed by etching and then refilled
• CPC Class Codes: H01L 29/7833 with lightly doped drain or source extension, e.g. LDD MOSFET's; DDD MOSFET's for thin film transistors H01L29/78618
• CPC Class Codes: H01L 29/7834 with a non-planar structure, e.g. the gate or the source or the drain being non-planar

Abstract

In one exemplary embodiment of the present invention a RFID tag for use in environments that cause antenna detuning is disclosed. The RFID tag comprises an antenna configured to receive radio frequency signals and an adjustable impedance adder coupled to the antenna. The impedance adder is configured to provide a needed amount of impedance to the antenna to compensate for detuning.

Claims

1. A RFID tag comprising:

a base impedance;

an antenna configured to receive radio frequency signals at about a resonant frequency when coupled to the base impendence; and

an adjustable impedance adder coupled to the antenna, the adjustable impedance adder configured to adjust the base impedance to compensate for a change in the resonant frequency of the antenna.

2. The RFID tag of claim 1 wherein a code is received by the RFID tag, the code specifying the needed amount of impedance.

3. The RFID tag of claim 2 further comprising a non-volatile writable memory configured to store the code.

4. The RFID tag of claim 1 wherein the RFID tag is inductively biased when no impedance is provided by the impedance adder.

5. The RFID tag of claim 1 wherein the impedance adder is an impedance tree comprising a plurality of capacitors, each capacitor switchably coupled to the antenna.

6. The RFID tag of claim 5 wherein the plurality of capacitors are in parallel with each other.

7. The RFID tag of claim 5 wherein the plurality of capacitors are in series with each other.

8. The RFID tag of claim 1 wherein the RFID tag is a semi-passive tag.

9. The RFID tag of claim 1 wherein the RFID tag is an active tag.

10. The RFID tag of claim 1 further comprising a state machine coupled to the antenna and the impedance adder, the state machine comprising different states corresponding to different amounts of impedance to be provided by the impedance adder.

11. The RFID tag of claim 10 wherein a RFID reader sends a signal indicative of a state to which to set the state machine.

12. The RFID tag of claim 3 wherein the memory stores the default setting for the impedance adder.

13. A method for adjusting the tuning of a RFID antenna:

receiving a signal at the RFID antenna, the signal including a setting indicative of an amount of impedance to provide to adjust the tuning of the RFID antenna;

adjusting an impedance source based on the amount of impedance indicated by the setting; and

coupling the amount of impedance from the impedance source to the RFID antenna.

14. The method of claim 13 wherein the step of coupling the amount of impedance further comprises coupling one or more capacitors to the RFID antenna to provide the amount of impedance.

15. The method of claim 14 further comprising setting the impedance source to a default setting.

16. The method of claim 15 further comprising storing the default setting to a non-volatile memory.

17. The method of claim 15 further comprising replacing the default setting with the setting provided in the signal.

18. A RFID tag comprising:

a RFID antenna designed to receive RF signals at about a resonant frequency; and

an impedance adjusting means for maintaining the resonant frequency of the RFID antenna, the impedance adjusting means coupled to RFID antenna.

21. The RFID tag of claim 18 wherein the impedance adjusting means for maintaining the resonant frequency is an impedance tree comprising a plurality of capacitors switchably coupled to the antenna.

22. The RFID tag of claim 18 wherein the RFID tag can be applied to a plurality of products, the impedance adjusting means set to provide a different amount of impedance for each of the plurality of products to which the RFID tag can be applied.

19. The RFID tag of claim 19 wherein the impedance adjusting means for maintaining the resonant frequency can be adjusted to provide more or less impedance to the RFID antenna to compensate for a shift in the resonant frequency of the RFID antenna.

20. The RFID tag of claim 19 further comprising a state machine coupled to the impedance adjusting means, the state machine including one or more states corresponding to different amounts of impedances to be provided by the impedance adjusting means.