Transmitter calibration for NFC (near field communication) device

• US 10,644,756 B2
• Filed: 07/30/2018
• Issued: 05/05/2020
• Est. Priority Date: 07/30/2018
• Status: Active Grant

• Current Assignee: NXP B.V. (NXP Semiconductors NV)
• Original Assignee: NXP B.V. (NXP Semiconductors NV)
• Inventors: Hueber, Gernot, Macnamara, Ian Thomas
• Primary Examiner(s): Trandai, Cindy
• Application Number:
  US16/049,436
• Publication Number:
  US 20200036412A1
• Time in Patent Office: 645 Days
• CPC Class Codes: H04B 17/12 of transmit antennas, e.g. of the amplitude or phase
• CPC Class Codes: H04B 5/24 Inductive coupling
• CPC Class Codes: H04B 5/48 Transceivers
• CPC Class Codes: H04B 5/72 for local intradevice communication

Abstract

This specification discloses methods and systems for controlling a NFC (near field communication) transmitter output with enhanced accuracy. This is achieved by first doing a device and/or system level calibration of the Tx (transmitter) by testing at the device and/or system level. Then using the testing results to generate a set of Tx calibration data, which will be used by a Tx control unit to control the Tx outputs (such as Tx output power, Tx output voltage, Tx output current, etc.) with enhanced accuracy. In some embodiments, the Tx control unit controls the Tx output with enhanced accuracy by using the Tx calibration data to tune one or more of the following: (i) Tx supply, (ii) Tx driver, (iii) matching network.

Claims

1. A device that communicates via inductive coupling, the device comprising:

a matching network;

an antenna;

a transmitter (Tx) unit, including a radio frequency transmitter, the Tx unit configured to generate a transmit signal that is transmitted through the matching network and the antenna;

a Tx control unit including circuitry that stores a look-up table having a plurality of calibration data sets, the Tx control unit configured to;

receive an indication of a target Tx output,

determine a first calibration data set associated with the target Tx output from the look-up table and based on the indication of the target Tx output, wherein the plurality of calibration data sets are generated during testing at a device level, and each of the plurality of calibration data sets is associated with a different target Tx output and a plurality of settings of components of the Tx unit associated with the different target Tx output; and

output at least one control signal based on the first calibration data set to control at least one setting of a component of the Tx unit of the plurality of settings of the components, wherein the at least one setting is configured to tune the Tx unit to generate the target Tx output;

wherein the target Tx output is associated with a target Tx output power level, and the plurality of settings of components of the Tx unit, for each of the plurality of calibration data sets, includes one of or a combination from among;

a supply voltage setting of the Tx unit, a pulse modulation setting of the Tx unit, and a control setting that indicates a number of drivers of a Tx driver of the Tx unit to use.

2. The device of claim 1, wherein the plurality of settings of components of the Tx unit, for each of the plurality of calibration data sets, includes:

the supply voltage setting of the Tx unit, the pulse modulation setting of the Tx unit, and the control setting that indicates a number of drivers of a Tx driver of the Tx unit to use.

3. The device of claim 1, wherein the target Tx output is a target Tx output voltage level, wherein each of the plurality of calibration data sets include a Tx supply voltage, pulse modulation of a Tx signal, Tx impedance, number of Tx drivers turned on, and an impedance setting of the matching network.

4. The device of claim 1, wherein the target Tx output is a target Tx output current level, and the Tx control unit is configured to output the at least one control signal based on the first calibration data set to control at least one setting of a plurality of components of the Tx unit.

5. The device of claim 1 further comprising:

a receiver (Rx) unit, including a radio frequency receiver, the Rx unit configured to receive a signal from a counterpart device.

6. The device of claim 5,

wherein the device is an near field communication (NFC)-enabled device operating in one of the following modes:

reader/writer mode,

card mode with active load modulation,

peer-to-peer mode.

7. The device of claim 1,

wherein the Tx unit is comprised of:

a Tx supply and a Tx driver, the Tx supply to provide a voltage to the Tx driver and the Tx driver to receive Tx data and the voltage as inputs and transmit the Tx data as an output, and

wherein the at least one setting comprises a changed voltage setting of the Tx supply.

8. The device of claim 1,

wherein the Tx unit is comprised of:

a Tx supply and a Tx driver, and

wherein the at least one setting comprises a changed pulse modulation setting of the Tx driver.

9. The device of claim 1, wherein

the Tx control unit is further configured to output another control signal to control at least one setting of the matching network, wherein the at least one setting comprises a changed impedance setting of the matching network.

10. The device of claim 1, wherein the target Tx output comprises one of the following:

a Tx power that is radiated from the antenna,

a Tx field strength that is radiated from the antenna,

a Tx output voltage that is fed to the matching network,

a voltage on any node in the matching network,

an antenna voltage, and

a receiver (Rx) input voltage that is provided by the matching network to an Rx unit of the device.

11. The device of claim 1, wherein each calibration data set comprises one or more of the following settings:

a supply voltage setting of the Tx unit,

a pulse modulation setting of the Tx unit,

an impedance setting of the Tx unit,

a control setting that indicates a number of drivers turned on, wherein the Tx unit includes a Tx driver comprising one or more drivers configured to be turned off and on by the control setting,

an impedance setting of the matching network, and

a variable capacitor setting of the matching network, wherein the matching network comprises a variable capacitor.

12. The device of claim 1,

wherein the Tx unit is comprised of:

a Tx supply and a Tx driver,

wherein the Tx driver comprises a plurality of transistors, and

wherein the at least one setting comprises a changed impedance setting of the plurality of transistors of the Tx driver.

13. The device of claim 1,

wherein the Tx unit is comprised of:

a Tx supply and a Tx driver,

wherein the Tx driver comprises a plurality of transistors, and

wherein the at least one setting comprises a changed bias setting of the plurality of transistors of the Tx driver.

14. The device of claim 13,

wherein the changed bias setting comprises one or more of a changed voltage setting or a changed current setting to change an operating point of the plurality of transistors of the Tx driver.

15. The device of claim 1,

wherein the Tx unit is comprised of:

a Tx supply and a Tx driver,

wherein the Tx driver comprises a set of one or more drivers, each driver configured to receive a respective control setting to be turned off and on, and

wherein the at least one setting comprises at least one changed control setting of the one or more drivers of the Tx driver.

16. The device of claim 1, wherein

the Tx control unit is further configured to output another control signal to control at least one setting of the matching network, wherein the at least one setting comprises a changed variable capacitor setting of a capacitor within the matching network.

17. A method for operating a device that communicates via inductive coupling, the method comprising:

generating, by a transmitter (Tx) unit of the device, a transmit signal, the Tx unit including a radio frequency Tx;

receiving, by a Tx control unit of the device, an indication of a target Tx output, the Tx control unit including circuitry that stores a look-up table having a plurality of calibration data sets,

determining a first calibration data set associated with the target Tx output from the look-up table and based on the indication of the target Tx output, wherein the plurality of calibration data sets is generated during testing at a device level, and each of the plurality of calibration data sets is associated with a different target Tx output and a plurality of settings of a component of the Tx unit associated with the different target Tx output, and

outputting at least one control signal based on the first calibration data set to control at least one setting of the component of the Tx unit of the plurality of settings of the component, wherein the at least one setting is configured to tune the Tx unit to generate the target Tx output;

wherein the target Tx output is associated with a target Tx output power level, and the plurality of settings of components of the Tx unit, for each of the plurality of calibration data sets, includes one of or a combination from among;

a supply voltage setting of the Tx unit, a pulse modulation setting of the Tx unit, and a control setting that indicates a number of drivers of a Tx driver of the Tx unit to use.

18. The method of claim 17, wherein the target Tx output is one of the following:

a target Tx output power level,

a target Tx output voltage level,

a target Tx output current level.

19. The method of claim 17,

wherein the Tx unit is comprised of:

a Tx supply and a Tx driver, and

wherein the at least one setting comprises a changed voltage setting of the Tx supply.

20. The method of claim 17,

wherein the Tx unit is comprised of:

a Tx supply and a Tx driver, and

wherein the at least one setting comprises a changed pulse modulation setting of the Tx driver.