RFID tag modification for full depth backscatter modulation

• US 20060145819A1
• Filed: 01/04/2005
• Published: 07/06/2006
• Est. Priority Date: 01/04/2005
• Status: Active Grant

• Current Assignee: Battelle Memorial Institute
• Original Assignee: Battelle Memorial Institute
• Inventors: Pratt, Richard M., Scott, Jeffrey Wayne
• Granted Patent: US 7,760,073 B2
• 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

A modulated backscatter radio frequency identification device includes a diode detector configured to selectively modulate a reply signal onto an incoming continuous wave; communications circuitry configured to provide a modulation control signal to the diode detector, the diode detector being configured to modulate the reply signal in response to be modulation control signal; and circuitry configured to increase impedance change at the diode detector which would otherwise not occur because the diode detector rectifies the incoming continuous wave while modulating the reply signal, whereby reducing the rectified signal increases modulation depth by removing the reverse bias effects on impedance changes. Methods of improving depth of modulation in a modulated backscatter radio frequency identification device are also provided.

Claims

1. A modulated backscatter radio frequency identification device comprising:

a diode detector configured to selectively modulate a reply signal onto an incoming continuous wave;

communications circuitry configured to provide a modulation control signal to the diode detector, the diode detector being configured to modulate the reply signal in response to be modulation control signal; and

circuitry configured to increase impedance change at the diode detector which would otherwise not occur because the diode detector rectifies the incoming continuous wave while modulating the reply signal, whereby reducing the rectified signal increases modulation depth by removing the reverse bias effects on impedance changes.

2. A modulated backscatter radio frequency identification device in accordance with claim 1 wherein the circuitry configured to increase impedance change comprises a transistor.

3. A modulated backscatter radio frequency identification device in accordance with claim 1 wherein the circuitry configured to increase impedance change comprises a MOSFET transistor.

4. A modulated backscatter radio frequency identification device in accordance with claim 1 wherein the circuitry configured to increase impedance change comprises a transistor having a control electrode coupled to be controlled by the modulation control signal.

5. A modulated backscatter radio frequency identification device in accordance with claim 1 wherein the circuitry configured to increase impedance change comprises a transistor having a control electrode coupled to the modulation control signal, a first power electrode coupled to the diode detector, and a second power electrode coupled to ground.

6. A method of improving depth of modulation in a modulated backscatter radio frequency identification device including a diode detector configured to selectively modulate a reply signal onto an incoming continuous wave and communications circuitry configured to provide a modulation control signal to the diode detector, the diode detector being configured to modulate the reply signal in response to the modulation control signal, the method comprising:

increasing impedance change at the diode detector which would otherwise not occur because the diode detector rectifies the incoming continuous wave while modulating the reply signal, whereby reducing the rectified signal increases modulation depth by removing the -reverse bias effects on impedance changes.

7. A method in accordance with claim 6 wherein only one component is added to increase impedance change.

8. A method in accordance with claim 7 wherein the component is a transistor.

9. A method in accordance with claim 6 wherein impedance change is increased using a MOSFET transistor.

10. A method in accordance with claim 6 wherein impedance change is increased using a transistor having a control electrode coupled to be controlled by the modulation control signal.

11. A method in accordance with claim 6 wherein the impedance change is increased using a transistor having a control electrode coupled to the modulation control signal, a first power electrode coupled to the diode detector, and a second power electrode coupled to ground.

12. A modulated backscatter radio frequency identification device comprising:

an antenna;

a diode detector coupled to the antenna, for use in receiving radio frequency data from a reader and in replying to the interrogator by modulating a reply signal onto an incoming continuous wave from the reader, the diode detector having an output and an input;

communications circuitry including a processor having a digital input and having a modulation control output configured to provide a modulation control signal to the diode detector, the diode detector being configured to modulate the reply signal in response to be modulation control signal;

front end circuitry coupled between the diode detector and the communications circuitry, the front end circuitry including a comparator having an output coupled to the digital input of the processor, having a positive input coupled to the output of the diode detector, and having a negative input, the front end circuitry further including a voltage divider having a first resistor coupled between the positive input and the negative input and having a second resistor coupled between the negative input and ground, the front end circuitry further including a capacitor coupled between the negative input and ground, the front end circuitry further including a resistor coupled between the positive input and ground, and the front end circuitry further including circuitry configured to selectively short the capacitor.

13. A modulated backscatter radio frequency identification device in accordance with claim 12 wherein the circuitry configured to short the capacitor is arranged to reduce voltage build up at the diode detector which would otherwise occur because the diode detector rectifies the incoming continuous wave while modulating the reply signal, whereby modulation depth is increased.

14. A modulated backscatter radio frequency identification device in accordance with claim 12 wherein the circuitry configured to selectively short the capacitor comprises a transistor.

15. A modulated backscatter radio frequency identification device in accordance with claim 12 wherein the circuitry configured to selectively short the capacitor shorts the capacitor from time to time.

16. A modulated backscatter radio frequency identification device in accordance with claim 12 wherein the circuitry configured to selectively short the capacitor comprises a MOSFET transistor.

17. A modulated backscatter radio frequency identification device in accordance with claim 12 wherein the circuitry configured to selectively short the capacitor comprises a MOSFET transistor having a gate coupled to the modulation control output.

18. A modulated backscatter radio frequency identification device in accordance with claim 12 wherein the circuitry configured to selectively short the capacitor comprises a MOSFET transistor having a gate coupled to the modulation control output.

19. A modulated backscatter radio frequency identification device in accordance with claim 12 wherein the circuitry configured to selectively short the capacitor comprises a transistor having a control electrode coupled to the modulation control output, a first power electrode coupled to the diode detector, and a second power electrode coupled to ground.

20. A modulated backscatter radio frequency identification device comprising:

an antenna;

a diode detector coupled to the antenna, for use in receiving radio frequency data from a reader and in replying to the interrogator by modulating a reply signal onto an incoming continuous wave from the reader, the diode detector having an output and an input;

communications circuitry including a processor having a digital input and having a modulation control output configured to provide a modulation control signal to the diode detector, the diode detector being configured to modulate the reply signal in response to be modulation control signal;

front end circuitry coupled between the diode detector and the communications circuitry, the front end circuitry including circuitry configured to reject spurious radio frequency signals having an output coupled to the digital input of the processor, having a first input coupled to the output of the diode detector, and having a second input, the front end circuitry further including a voltage divider having a first resistor coupled between the first input and the second input and having a second resistor coupled between the second input and ground, the front end circuitry further including a capacitor coupled between the second input and ground, the front end circuitry further including a resistor coupled between the first input and ground, and the front end circuitry further including a transistor having a control electrode coupled to the modulation control output, having a first power electrode coupled to the second input, and having a second power electrode coupled to ground.

21. A modulated backscatter radio frequency identification device in accordance with claim 20 wherein the circuitry configured to reject spurious radio frequency signals comprises a comparator having a positive input defining the first input and having a negative input defining the second input.

22. A modulated backscatter radio frequency identification device in accordance with claim 20 wherein the transistor, in operation, shorts the capacitor from time to time.

23. A modulated backscatter radio frequency identification device in accordance with claim 20 wherein the transistor is a MOSFET transistor.

24. A modulated backscatter radio frequency identification device comprising:

an antenna;

a diode detector coupled to the antenna, for use in receiving radio frequency data from a reader and in replying to the interrogator by modulating a reply signal onto an incoming continuous wave from the reader, the diode detector having an output and an input;

communications circuitry including a processor having a digital input and having a modulation control output configured to provide a modulation control signal to the diode detector, the diode detector being configured to modulate the reply signal in response to be modulation control signal;

front end circuitry coupled between the diode detector and the communications circuitry, the front end circuitry including a comparator having an output coupled to the digital input of the processor, having a positive input coupled to the output of the diode detector, and having a negative input, the front end circuitry further including a voltage divider having a first resistor coupled between the positive input and the negative input and having a second resistor coupled between the negative input and ground, the front end circuitry further including a capacitor coupled between the negative input and ground, the front end circuitry further including a resistor coupled between the first input and ground, and the front end circuitry further including a transistor having a control electrode coupled to the modulation control output, having a first power electrode coupled to the second input, and having a second power electrode coupled to ground.

25. A modulated backscatter radio frequency identification device in accordance with claim 24 wherein the transistor, in operation, shorts the capacitor from time to time.

26. A modulated backscatter radio frequency identification device in accordance with claim 24 wherein the transistor is a MOSFET transistor.