Determining initial transmission phase offset in an NFC device

Patent metadata

Field	Value
Publication number	US-12119892-B2
Application number	US-202217752371-A
Country	US
Kind code	B2
Filing date	May 24, 2022
Priority date	Jun 21, 2021
Publication date	Oct 15, 2024
Grant date	Oct 15, 2024

Abstract

There is described a method of determining an initial transmission phase offset in an NFC device configured to operate in NFC card mode only, wherein the NFC device comprises an NFC chip and a matching circuit. The method comprises: determining an initial RF matching resonance frequency of the NFC device utilizing an internal oscillator of the NFC chip; reading correction data from a non-volatile memory of the NFC chip, the correction data being indicative of a frequency offset of the internal oscillator relative to a nominal oscillator frequency; determining a corrected RF matching resonance frequency of the NFC device based on the initial RF matching resonance frequency and the correction data; and determining the initial transmission phase offset based on the corrected RF matching resonance frequency. Furthermore, a device and a method of manufacturing an NFC device are described.

First claim

The invention claimed is:

1. A method of determining an initial transmission phase offset in an NFC device configured to operate in NFC card mode only, wherein the NFC device comprises an NFC chip and a matching circuit, the method comprising
determining an initial RF matching resonance frequency of the NFC device utilizing an internal oscillator of the NFC chip;
reading correction data from a non-volatile memory of the NFC chip, the correction data being indicative of a frequency offset of the internal oscillator relative to a nominal oscillator frequency;
determining a corrected RF matching resonance frequency of the NFC device based on the initial RF matching resonance frequency and the correction data; and
determining the initial transmission phase offset based on the corrected RF matching resonance frequency.

2. The method according to claim 1 , wherein the correction data comprises a first correction factor indicative of a frequency offset associated with a silicon process used to manufacture the NFC chip, and wherein determining the corrected RF matching frequency comprises applying the first correction factor to the initial RF matching frequency.

3. The method according to claim 1 , wherein the correction data comprises a second correction factor indicative of a frequency offset associated with an operating voltage of the NFC chip, and wherein determining the corrected RF matching frequency comprises applying the second correction factor to the initial RF matching frequency.

4. The method according to claim 3 , wherein
the correction data further comprises a reference operating voltage,
the method further comprises measuring an actual operating voltage of the NFC chip, and
determining the corrected RF matching frequency is further based on a difference between the measured actual operating voltage of the NFC chip and the reference operating voltage.

5. The method according to claim 1 , wherein the correction data comprises a third correction factor indicative of a frequency offset associated with an operating temperature of the NFC chip, and wherein determining the corrected RF matching frequency comprises applying the third correction factor to the initial RF matching frequency.

6. The method according to claim 5 , wherein
the correction data further comprises a reference operating temperature,
the method further comprises measuring an actual operating temperature of the NFC chip, and
determining the corrected RF matching frequency is further based on a difference between the measured actual operating temperature of the NFC chip and the reference operating temperature.

7. The method according to claim 2 ,
wherein the correction data further comprises a second correction factor indicative of a frequency offset associated with an operating voltage of the NFC chip, and wherein determining the corrected RF matching frequency comprises applying the second correction factor to the initial RF matching frequency, wherein the correction data further comprises a reference operating voltage, the method further comprises measuring an actual operating voltage of the NFC chip, and determining the corrected RF matching frequency is further based on a difference between the measured actual operating voltage of the NFC chip and the reference operating voltage,
wherein the correction data further comprises a third correction factor indicative of a frequency offset associated with an operating temperature of the NFC chip, and wherein determining the corrected RF matching frequency comprises applying the third correction factor to the initial RF matching frequency, wherein the correction data further comprises a reference operating temperature, the method further comprises measuring an actual operating temperature of the NFC chip, and determining the corrected RF matching frequency is further based on a difference between the measured actual operating temperature of the NFC chip and the reference operating temperature, and
wherein the corrected RF matching frequency is determined by adding
(i) the initial RF matching frequency multiplied with the first correction factor,
(ii) the initial RF matching frequency multiplied with the second correction factor and multiplied with the difference between the actual operating voltage of the NFC chip and the reference operating voltage, and
(iii) the initial RF matching frequency multiplied with the third correction factor and multiplied with the difference between the actual operating temperature of the NFC chip and the reference operating temperature.

8. The method according to claim 5 , further comprising operating the NFC chip for a predetermined period of time in order to provide a stable operating temperature prior to determining the initial RF matching resonance frequency and measuring the actual operating temperature.

9. The method according to claim 1 , wherein the correction data is determined and written into the non-volatile memory during a silicon production test procedure.

10. A device configured to operate in NFC card mode only, the device comprising:
a matching circuit; and
an NFC chip coupled to the matching circuit, the NCF chip comprising:
an internal oscillator;
a non-volatile memory storing correction data indicative of a frequency offset of the internal oscillator relative to a nominal oscillator frequency; and
an NFC processing unit,

wherein the NFC processing unit is configured to:
determine an initial RF matching resonance frequency of the NFC device utilizing the internal oscillator;
read correction data from the non-volatile memory;
determine a corrected RF matching resonance frequency of the NFC device based on the initial RF matching resonance frequency and the correction data; and
determine an initial transmission phase offset based on the corrected RF matching resonance frequency.

11. The device according to claim 10 , wherein the correction data comprises a first correction factor indicative of a frequency offset associated with a silicon process used to manufacture the NFC chip, and wherein the NFC processing unit is further configured to determine the corrected RF matching frequency by applying the first correction factor to the initial RF matching frequency.

12. The device according to claim 10 , wherein the correction data comprises at least one of
a second correction factor indicative of a frequency offset associated with an operating voltage of the NFC chip, and
a reference operating voltage,
the device further comprising a voltage sensor configured to measure an actual operating voltage of the NFC chip, and
wherein the NFC processing unit is further configured to determine the corrected RF matching frequency based on at least one of the second correction factor, the reference operating voltage and the actual operating voltage measured by the voltage sensor.

13. The device according to claim 10 ,
wherein the correction data comprises at least one of
a third correction factor indicative of a frequency offset associated with an operating temperature of the NFC chip, and
a reference operating temperature,

the device further comprising a temperature sensor configured to measure an actual operating temperature of the NFC chip, and
wherein the NFC processing unit is further configured to determine the corrected RF matching frequency based on at least one of the third correction factor, the reference operating temperature and the actual operating temperature measured by the voltage sensor.

14. The device according to claim 11 , wherein the NFC processing unit is configured to determine the corrected RF matching frequency by adding

Assignees

• Nxp Bv

Inventors

• Wobak Markus

Classifications

• H04B17/22

  for calibration of the receiver components · CPC title

• H04B17/29

  Performance testing · CPC title

• H04B5/70

  specially adapted for specific purposes · CPC title

• H04B5/72 Primary

  for local intradevice communication · CPC title

• H04B5/45 Primary

  Transponders · CPC title