RFID system with selectable backscatter parameters

• US 20050052279A1
• Filed: 08/27/2004
• Published: 03/10/2005
• Est. Priority Date: 08/29/2003
• Status: Abandoned Application

• Current Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Original Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Inventors: Bridgelall, Raj
• Application Number:
  US10/927,775
• Publication Number:
  US 20050052279A1
• Time in Patent Office: Days
• US Class Current: 340/10.100
• 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 19/0724 the arrangement being a circuit for communicating at a plurality of frequencies, e.g. for managing time multiplexed communication over at least two antennas of different types
• CPC Class Codes: G06K 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer

Abstract

A RFID tag for use in an RFID system is disclosed. The RFID tag comprises an antenna operable to receive a carrier wave from an RFID reader. A state machine is coupled to the antenna and receives a backscattering command comprising a backscattering parameter for the RFID tag to use for backscattering the carrier wave. A modulator is coupled between the antenna and the state machine. The modulator produces a modulated backscatter signal, based at least partially dependent on the backscattering command.

Claims

1. A RFID tag comprising:

an antenna operable to receive a carrier wave from an RFID reader;

a state machine coupled to the antenna, the state machine operable to receive a backscattering command comprising a backscattering parameter for the RFID tag to use for backscattering the carrier wave; and

a modulator coupled between the antenna and the state machine, the modulator operable to produce a modulated backscatter signal, at least partially formed based on the backscattering parameters.

2. The RFID tag of claim 1 wherein the backscattering command determines the frequency of the modulated backscatter signal.

3. The RFID tag of claim 1 wherein the backscattering command determines the modulation scheme of the modulated backscatter signal.

4. The RFID tag of claim 1 further comprising a non-volatile memory that stores a code related to a product.

5. The RFID tag of claim 4 wherein the memory is a read/write memory.

6. The RFID tag of claim 1 wherein the antenna is operable to receive a frequency in the ultra high frequency range.

7. The RFID tag of claim 1 further comprising a voltage rectifier operable to convert an induced AC voltage induced by the carrier wave to a DC voltage.

8. The RFID tag of claim 1 further comprising an oscillator, the frequency of the oscillator determining the frequency of the modulated backscatter signal.

9. The RFID tag of claim 8 wherein a frequency outputted by the oscillator is determined by the state of the state machine as set by the backscattering command.

10. The RFID tag of claim 9 wherein a timing signal sent with the carrier wave is used to determine the frequency of the modulated backscattered signal.

11. The RFID tag of claim 10 wherein the frequency produced by the timing signal is determined by the state of the state machine as set by the backscattering command.

12. A RFID reader for use in an RFID system comprising:

signal strength quality indicator means for determining a signal strength of one or more frequencies in a range of frequencies;

processor means for generating a command based on the output of the signal strength circuit; and

transceiver means for generating a signal containing the command.

13. The RFID reader of claim 12 wherein the command determines a frequency an RFID tag should use for a backscatter signal.

14. The RFID reader of claim 12 wherein the command determines a modulation scheme an RFID tag should use for a backscatter signal.

15. The RFID reader of claim 12 wherein the RFID reader is coupled to a point of sales system.

16. A method for operating an RFID tag comprising:

determining a backscatter modulation signal setting based on a command received from an RFID reader; and

generating a backscatter modulation signal based at least partially on the backscatter modulation signal setting.

17. The method of claim 16 wherein the step of determining a backscatter signal setting based on a command received from an RFID reader further comprises setting a state of a state machine such that the backscatter modulation signal is set to a specific frequency.

18. The method of claim 16 wherein the step of determining a backscatter signal setting based on a command received from an RFID reader further comprises setting a state of a state machine such that a selected modulation scheme is used to modulate the backscatter modulation signal.

19. The method of claim 16 further comprising the steps of:

inducing an AC voltage from a received carrier wave;

rectifying the AC voltage to produce a DC voltage; and

powering the RFID tag at least partly with the DC voltage.

20. The method of claim 16 further comprising sending a product identification number in the backscatter modulation signal.