RFID tag with separate transmit and receive clocks and related method

• US 20060273882A1
• Filed: 06/01/2005
• Published: 12/07/2006
• Est. Priority Date: 06/01/2005
• Status: Abandoned Application

• Current Assignee: Intel Corporation
• Original Assignee: Intel Corporation
• Inventors: Posamentier, Joshua
• Application Number:
  US11/142,424
• Publication Number:
  US 20060273882A1
• Time in Patent Office: Days
• US Class Current: 340/10.400
• 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

Abstract

An RFID tag includes separate transmit and receive clocks. In at least one embodiment, the transmit clock frequency is adjusted based on an amount of power available to transmit a response signal to a reader.

Claims

1. A method comprising:

receiving an interrogation signal from a remote reader device;

measuring a power related parameter of said interrogation signal; and

adjusting a frequency of a transmit oscillator based on a measured value of said power related parameter to generate a transmit clock.

2. The method of claim 1, wherein:

said interrogation signal includes amplitude shift keying (ASK) modulation.

3. The method of claim 1, wherein:

measuring a power related parameter of said interrogation signal includes measuring a signal strength of said interrogation signal.

4. The method of claim 1, further comprising:

generating a response signal for communication to the remote reader device using said transmit clock.

5. The method of claim 4, wherein generating a response signal includes:

processing a command portion of said interrogation signal to determine one or more commands of said remote reader device; and

generating a baseband response to said one or more commands using said transmit clock.

6. The method of claim 5, wherein:

generating a response signal includes using backscatter antenna impedance modulation to modulate the impedance of an antenna based on said baseband response.

7. The method of claim 1, wherein:

adjusting a frequency of a transmit oscillator includes setting a higher frequency for a higher value of said power related parameter and a lower frequency for a lower value of said power related parameter.

8. The method of claim 1, wherein:

adjusting a frequency of a transmit oscillator includes applying a voltage to a voltage controlled oscillator.

9. An apparatus for use in an RFID tag, comprising:

a power sensor to measure a power related parameter of a received interrogation signal; and

an adjustable-frequency transmit oscillator to adjust a transmit clock frequency of the RFID tag based on an output of said power sensor.

10. The apparatus of claim 9, further comprising:

a tag command processor to recognize and process one or more commands of said interrogation signal.

11. The apparatus of claim 10, further comprising:

a tag response state machine to generate a tag response based on an output of said tag command processor, said tag response state machine being coupled to receive an output signal from said transmit oscillator.

12. The apparatus of claim 9, further comprising:

an antenna modulation controller to modulate an antenna using backscatter antenna impedance modulation at said transmit clock frequency.

13. The apparatus of claim 9, wherein:

said adjustable-frequency transmit oscillator includes a voltage-controlled oscillator.

14. An RFID tag, comprising:

a dipole antenna to receive an interrogation signal from a wireless channel;

a power sensor to measure a power related parameter of said received interrogation signal; and

an adjustable-frequency transmit oscillator to adjust a transmit clock frequency of the RFID tag based on an output of said power sensor.

15. The RFID tag of claim 14, further comprising:

a tag command processor to recognize and process one or more commands of said interrogation signal.

16. The RFID tag of claim 15, further comprising:

a tag response state machine to generate a tag response based on an output of said tag command processor, said tag response state machine being coupled to receive an output signal from said transmit oscillator.

17. The RFID tag of claim 14, further comprising:

an antenna modulation controller to modulate an antenna using backscatter antenna impedance modulation at said transmit clock frequency.

18. The RFID tag of claim 14, wherein:

said adjustable-frequency transmit oscillator includes a voltage-controlled oscillator.