# US 12,119,892 B2 · Determining initial transmission phase offset in an NFC device > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,119,892 B2 - Document ID: US12119892B2 - Status: Granted - Kind: B2 - Application number: 17/752,371 - Filed: 2022-05-24 - Published: 2022-12-22 - Granted: 2024-10-15 - Earliest claimed: 2021-06-21 - Assignees: NXP B.V. - Applicants: NXP B.V. - Inventors: Markus Wobak - Web page: https://patentgrep.com/patent/US12119892B2 ## CPC - H04B 5/45: Transponders - H04B 5/73: for taking measurements, e.g. using sensing coils - H04B 1/06: Receivers - H04B 5/70: specially adapted for specific purposes - H04B 5/72: for local intradevice communication - H04B 17/12: of transmit antennas, e.g. of the amplitude or phase - H04B 17/22: {for calibration of the receiver components} - H04B 17/29: Performance testing - G06K 7/10297: {arrangements for handling protocols designed for non-contact record carriers such as RFIDs NFCs, e.g. ISO/IEC 14443 and 18092 (cryptographic protocols H04L9/00; network security protocols H04L63/00; real-time communication protocols in data switching networks H04L65/00; network protocols for data switching network services H04L67/00)} - H02J 50/12: of the resonant type - H04B: TRANSMISSION - G06K: GRAPHICAL DATA READING (image or video recognition or understanding G06V); PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS - H02J: ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY ## 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. ## Claims ### Claim 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. ### Claim 2 (depends on 1) 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. ### Claim 3 (depends on 1) 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. ### Claim 4 (depends on 3) 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. ### Claim 5 (depends on 1) 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. ### Claim 6 (depends on 5) 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. ### Claim 7 (depends on 2) 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. ### Claim 8 (depends on 5) 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. ### Claim 9 (depends on 1) 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. ### Claim 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. ### Claim 11 (depends on 10) 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. ### Claim 12 (depends on 10) 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. ### Claim 13 (depends on 10) 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. ### Claim 14 (depends on 11) The device according to claim 11, wherein the NFC processing unit is configured to determine the corrected RF matching frequency by adding the initial RF matching frequency multiplied with the first correction factor, 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 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. ### Claim 15 (depends on 13) The device according to claim 13, wherein the NFC processing unit is configured to operate 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. ### Claim 16 (depends on 10) The device according to claim 10, wherein the correction data is determined and written into the non-volatile memory during a silicon production test procedure. ### Claim 17 A method of manufacturing an NFC device configured to operate in NFC card mode only, the method comprising: manufacturing an NFC chip, the NFC chip comprising an internal oscillator, a non-volatile memory, and an NFC processing unit; determining, during a silicon production test procedure, correction data indicative of a frequency offset of the internal oscillator relative to a nominal oscillator frequency; writing the determined correction data into the non-volatile memory; mounting the NFC chip in the NFC device and connecting the NFC chip to a matching circuit; determining an initial RF matching resonance frequency of the NFC device utilizing the internal oscillator of the NFC chip; reading the correction data from the non-volatile memory of the NFC chip; 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. ### Claim 18 (depends on 17) The method according to claim 17, wherein the correction data includes at least one parameter selected from the group comprising: a first correction factor indicative of a frequency offset associated with a silicon process used to manufacture the NFC chip, a second correction factor indicative of a frequency offset associated with an operating voltage of the NFC chip, a reference operating voltage of the NFC chip, a third correction factor indicative of a frequency offset associated with an operating temperature of the NFC chip, and a reference operating temperature of the NFC chip. ### Claim 19 (depends on 17) The method according to claim 17, further comprising measuring at least one of an actual operating voltage of the NFC chip and an actual operating temperature of the NFC chip.