NFC or RFID device RF detuning detection and driver output power regulation

• US 10,164,600 B2
• Filed: 10/12/2015
• Issued: 12/25/2018
• Est. Priority Date: 10/12/2015
• Status: Active Grant

• Current Assignee: NXP B.V. (NXP Semiconductors NV)
• Original Assignee: NXP B.V. (NXP Semiconductors NV)
• Inventors: Kormann, Leonhard, Wobak, Markus, Nunziata, Fred George
• Primary Examiner(s): Tsvey, Gennadiy
• Application Number:
  US14/881,095
• Publication Number:
  US 20170104468A1
• Time in Patent Office: 1,170 Days
• CPC Class Codes: G06K 7/10148 the step consisting of dynamically tuning the resonant circuit of the interrogation device that is emitting the interrogation signal, e.g. for impedance matching inside of the interrogation device for tuning related to loop aerials in general H01Q7/00
• CPC Class Codes: G06K 7/10158 methods and means used by the interrogation device for reliably powering the wireless record carriers using an electromagnetic interrogation field
• CPC Class Codes: G06K 7/10217 parameter settings controlling the transmission power of the interrogator
• CPC Class Codes: H03H 7/38 Impedance-matching networks
• CPC Class Codes: H04B 5/77 for interrogation

Abstract

A near field communication (NFC) or Radio Frequency Identification (RFID) reader device for contact-less communication includes a transmitter block connected to an antenna via a matching circuitry. An electromagnetic carrier signal and modulated data information are emitted via this main antenna. Any secondary object brought into the vicinity of the main antenna influences the primary resonant circuit resulting in a load change seen by the transmitter. This detuning can cause increased power consumption, RF (Radio Frequency) standard incompliance, and device damage. The present disclosure describes devices and methods on how to detect detuning and how to regulate the transmitter'"'"'s output.

Claims

1. A method for detuning detection and transmitter (TX) current regulation, the method comprising:

monitoring, by a sensor within a transmitter in a transmitter reader mode of a radio frequency (RF) device, a transmitter (TX) current and/or voltage at a maximum predetermined transmitter power level that corresponds to a first operational gear associated with a first corresponding specific register configuration, wherein the TX current and/or voltage is output by an output driver of the transmitter to drive an antenna and matching circuit of the RF device;

detecting a change in the TX current and/or voltage as output by the output driver, and

in response to the detected change, detecting an initial detuning of the antenna and matching circuit arising from a load change on the antenna resulting from interaction with a further resonant circuit; and

in response to detection of the initial detuning, reducing the TX current to match inductance between the antenna and matching circuit and the further resonant circuit by shifting the transmitter power level to one of a plurality of lower discrete gears based on a comparison between a predicted TX current and a plurality of TX current thresholds, wherein each lower discrete gear is associated with a different specific register configuration, and a discrete, predetermined transmitter power level that is below the maximum predetermined transmitter power level, and further wherein the transmitter is configured to initiate reading in highest gear and only shift to a lower gear to match inductance between the antenna and matching circuit and the further resonant circuit.

2. The method of claim 1, wherein the TX current is reduced by changing a transmitter supply voltage or a transmitter internal resistance, wherein monitoring by the sensor further includes monitoring the TX current and the TX voltage, and detecting the initial detuning of the antenna and matching circuit is responsive to the change in the TX current and TX voltage output by the output driver.

3. The method of claim 2, wherein changing the transmitter supply voltage or the transmitter internal resistance is controlled using a control unit including circuitry.

4. The method of claim 3, wherein changing the transmitter supply voltage or the transmitter internal resistance is performed by an active attenuator.

5. The method of claim 1, wherein the transmitter is a Near Field Communication (NFC) transmitter or a Radio Frequency Identification (RFID) transmitter, and further including

monitoring, by another sensor within the transmitter of the RF device, a change in a voltage and/or current of the antenna and matching circuit, and

wherein the detecting of the initial detuning of the antenna and matching circuit is responsive to:

the change in the TX current and/or voltage as output by the output driver; and

the change in the voltage and/or current of the antenna and matching circuit.

6. The method of claim 1, furthering including:

monitoring, by another sensor within the transmitter, a voltage or current of an antenna and matching circuit; and

wherein the detecting further includes;

detecting a change in the voltage or current of the antenna and matching circuit; and

in response to the detected change in the voltage or current of the antenna and matching circuit, detecting the initial detuning of the antenna and matching circuit.

7. A method for detuning detection and transmitter (TX) current regulation, the method comprising:

monitoring, by a sensor within a transmitter of a radio frequency (RF) device, a transmitter (TX) voltage and/or current as output by an output driver of the transmitter to drive an antenna and matching circuit of the RF device, wherein the antenna and matching circuit is in a transmitter reader mode at a maximum predetermined transmitter power level that corresponds to a first operational gear associated with a first corresponding specific register configuration;

detecting a change in the TX voltage and/or current using the sensor;

detecting, in response to the detected change, an initial detuning of the antenna and matching circuit arising from a load change on the antenna resulting from interaction with a further resonant circuit; and

in response to detection of the initial detuning, reducing the transmitter (TX) current to match inductance between the antenna and matching circuit and the further resonant circuit by shifting the transmitter power level to one of a plurality of lower gears based on a comparison between a predicted TX current and a plurality of TX current thresholds, wherein each lower gear is associated with a different specific corresponding register configuration, and a discrete, predetermined transmitter power level that is below the maximum predetermined transmitter power level, and further wherein the transmitter is configured to initiate reading in highest gear and only shift to a lower gear to match inductance between the antenna and matching circuit and the further resonant circuit.

8. The method of claim 7, wherein reduction of the TX current is achieved by changing a transmitter supply voltage or a transmitter internal resistance.

9. The method of claim 8, wherein changing the transmitter supply voltage or the transmitter internal resistance is controlled using a control unit.

10. The method of claim 9, wherein changing the transmitter supply voltage or the transmitter internal resistance is performed by an active attenuator.

11. The method of claim 7, further comprising:

monitoring a voltage or current at one or more nodes of the antenna and matching circuit.

12. The method of claim 7, further comprising:

monitoring, by a sensor within a transmitter, a transmitter (TX) current and/or voltage; and

detecting

a change in the TX current and/or voltage,

in response to the detected change in the TX current and/or voltage and a detected change in the voltage or current of the antenna and matching circuit, the detuning of the antenna and matching circuit by a change in the TX current and/or voltage and/or a change in the voltage or current of the antenna and matching circuit.

13. The method of claim 7, wherein the transmitter is a Near Field Communication (NFC) transmitter or a Radio Frequency Identification (RFID) transmitter.

14. A device for detuning detection and transmitter (TX) current regulation, the device comprising:

a transmitter circuit including;

an active attenuator configured to generate a transmitter (TX) voltage;

a first sensor;

a second sensor;

an output driver configured and arranged to output an TX current and/or voltage; and

a control unit; and

an antenna and matching circuit configured to be driven by the TX current corresponding to the TX voltage as output by the output driver, wherein

the first sensor is configured to monitor the TX current and/or voltage;

the second sensor is configured to monitor a voltage or current of the antenna and matching circuit; and

the control unit, including circuitry, configured to;

detect a change in the TX current and/or voltage as output by the output driver and a change in the voltage or current of the antenna and matching circuit;

detect, in response to the detected change in the TX current and/or voltage and the detected change in the voltage or current of the antenna and matching circuit, an initial detuning of the antenna and matching circuit arising from a load change on the antenna resulting from interaction with a further resonant circuit, and

in response to detection of the initial detuning, reduce the TX current to match inductance between the antenna and matching circuit and the further resonant circuit, wherein the device is configured to initially operate at a maximum predetermined transmitter power level that corresponds to a first operational gear associated with a first corresponding specific register configuration, and further wherein inductance is matched between the antenna and matching circuit and the further resonant circuit by shifting the transmitter power level to one of a plurality of lower gears based on a comparison between a predicted TX current and a plurality of TX current thresholds, wherein each lower gear is associated with a different specific corresponding register configuration, and a discrete, predetermined transmitter power level that is below the maximum predetermined transmitter power level.

15. The device of claim 14, wherein the control unit reduces the TX current by changing a TX supply voltage or a TX internal resistance.

16. The device of claim 15 further comprising:

a pre-driver configured to generate an amplified signal for input to the active attenuator.

17. The device of claim 16, wherein the second sensor monitors the voltage or current of the antenna and matching circuit at one or more nodes of the antenna and matching circuit.

18. The device of claim 14, wherein the device is a Near Field Communication (NFC) device or a Radio Frequency Identification (RFID) device.

19. The device of claim 14, wherein the control unit, including the circuitry, is further configured to detect the initial detuning of the antenna and matching circuit in response to the detected change in the TX current and/or voltage and the detected change in the voltage or current of the antenna and matching circuit.