NFC matching circuit debugging method, NFC matching circuit and electronic device

Abstract

Disclosed in the present application are an NFC matching circuit debugging method, an NFC matching circuit and an electronic device. The debugging method comprises: connecting a resonant circuit to two transmitting ends of an NFC controller, and connecting an impedance matching circuit to an NFC antenna; when the resonant circuit and the impedance matching circuit are in a disconnected state, debugging the resonant circuit, and when a measured resonant frequency of the resonant circuit is configured to be equal to a target resonant frequency, determining target element parameters of the resonant circuit, wherein the target resonant frequency is greater than or equal to an operating frequency of the NFC antenna; and when the resonant circuit and the impedance matching circuit are in the disconnected state, debugging a matching impedance of the impedance matching circuit from an input end to ground, and when the matching impedance of the impedance matching circuit meets both a first condition and a second condition, determining target element parameters of the impedance matching circuit. The costs of an NFC matching circuit debugged by means of the method are relatively low, and the efficiency and performance of signal transmission are ensured.

Claims

1. A method of debugging an NFC matching circuit, wherein, include: Connect the resonant circuit to the two transmitters of the NFC controller and the impedance matching circuit to the NFC antenna. When the resonant circuit and the impedance matching circuit are in the open state, the resonant circuit is debugged. When the measured resonant frequency of the resonant circuit is configured to be equal to the target resonant frequency, the target component parameters of the resonant circuit are determined. The target resonant frequency is greater than or equal to the operating frequency of the NFC antenna. When the resonant circuit and the impedance matching circuit are in the open state, the matching impedance from the input terminal of the impedance matching circuit to ground is adjusted. When the matching impedance of the impedance matching circuit simultaneously meets the first condition and the second condition, the target component parameters of the impedance matching circuit are determined. The first condition is that the impedance curve of the impedance matching circuit has a first resonant point, a second resonant point, and a third resonant point with successively increasing frequencies on the Smith chart. The impedances of the first resonant point and the third resonant point are the same, and the frequency of the second resonant point is the operating frequency of the NFC antenna. The second condition is that the matching impedance corresponding to the operating frequency of the NFC antenna is configured to be equal to the target impedance.

2. The method of claim 1, wherein, The resonant circuit includes a resonant inductor and a resonant capacitor; the first end of the resonant inductor is connected to one transmitting end of the NFC controller, and the second end of the resonant inductor is connected to the impedance matching circuit; the first end of the resonant capacitor is connected to the other transmitting end of the NFC controller, and the second end of the resonant capacitor is connected to the impedance matching circuit. When the resonant circuit and the impedance matching circuit are in an open state, the resonant circuit is adjusted, and when the measured resonant frequency of the resonant circuit is configured to be equal to the target resonant frequency, the target component parameters of the resonant circuit are determined, including: The resonant circuit and the impedance matching circuit are controlled to be in an open state, the resonant circuit is adjusted, and the measured resonant frequency of the series circuit formed by the resonant inductor and the resonant capacitor is obtained. If the measured resonant frequency is greater than the target resonant frequency, then the initial inductance value of the resonant inductor and / or the initial capacitance value of the resonant capacitor are increased. If the measured resonant frequency is less than the target resonant frequency, then the initial inductance value of the resonant inductor and / or the initial capacitance value of the resonant capacitor are reduced. If the measured resonant frequency is equal to the target resonant frequency, then the initial inductance value of the resonant inductor and the initial capacitance value of the resonant capacitor are respectively determined as the target inductance value of the resonant inductor and the target capacitance value of the resonant capacitor.

3. The method of claim 2, wherein, When the resonant circuit and the impedance matching circuit are in an open state, the matching impedance from the input terminal of the impedance matching circuit to ground is adjusted. When both the first and second conditions are met simultaneously, the target component parameters of the impedance matching circuit are determined, including: When the resonant circuit and the impedance matching circuit are in the open state, the matching impedance from the input terminal of the impedance matching circuit to ground is adjusted. When the first condition and the second condition are met at the same time, the standard component parameters of the impedance matching circuit are determined. When the resonant circuit and the impedance matching circuit are in a connected state, the performance of the NFC matching circuit is tested to obtain the first test result of the NFC matching circuit. Based on the first test results of the NFC matching circuit, the standard component parameters of the impedance matching circuit are adjusted to determine the target component parameters of the impedance matching circuit.

4. The method of claim 3, wherein, The impedance matching circuit includes an EMC filter and a matching unit. The first end of the EMC filter is used to connect to the resonant circuit, and the second end of the EMC filter is connected to the first end of the matching unit. The second end of the matching unit is used to connect to the NFC antenna. When the resonant circuit and the impedance matching circuit are in a connected state, the NFC matching circuit is subjected to performance testing to obtain a first test result of the NFC matching circuit, including: The first terminal of the receiving circuit is connected to the receiving terminal of the NFC controller, and the second terminal of the receiving circuit is connected to the NFC antenna or to the NFC antenna through the matching unit. When the resonant circuit and the EMC filter are in the connected state, the performance of the NFC matching circuit is tested to obtain the first test result of the NFC matching circuit. The first test result includes the measured transmitting magnetic field strength and the measured receiving load modulation amplitude. Based on the first test result of the NFC matching circuit, the standard component parameters of the impedance matching circuit are adjusted to determine the target component parameters of the impedance matching circuit, including: If the measured transmitted magnetic field strength is greater than a preset magnetic field strength threshold, and the measured received load modulation amplitude is greater than a preset load modulation amplitude threshold, then the standard component parameters of the EMC filter are determined as the target component parameters of the EMC filter, and the standard component parameters of the matching unit are determined as the target component parameters of the matching unit. If the measured transmitted magnetic field strength is not greater than a preset magnetic field strength threshold, or the measured received load modulation amplitude is not greater than a preset load modulation amplitude threshold, then the standard component parameters of the EMC filter are determined as the target component parameters of the EMC filter, and the standard component parameters of the matching unit are biased to determine the target component parameters of the matching unit.

5. The method of claim 4, wherein, The impedance matching circuit includes a first matching capacitor and a second matching capacitor; the first terminal of the first matching capacitor is connected to the EMC filter, and the second terminal of the first matching capacitor is connected to the NFC antenna; the first terminal of the second matching capacitor is connected to the connection node between the EMC filter and the NFC antenna, and the second terminal of the second matching capacitor is grounded. The step of performing a biasing process on the standard component parameters of the matching unit to determine the target component parameters of the matching unit includes: The standard capacitance value of the first matching capacitor is determined as the target capacitance value of the first matching capacitor, and the difference between the standard capacitance value of the second matching capacitor and the preset change amount is determined as the target capacitance value of the second matching capacitor.

6. The method of claim 5, wherein, The preset variation range is 0.025 to 0.25 times the standard capacitance value of the second matching capacitor.

7. The method of claim 4, wherein, The EMC filter includes a filter inductor and a filter capacitor; the first end of the filter inductor is connected to the resonant circuit, and the second end of the filter inductor is connected to the impedance matching circuit; the first end of the filter capacitor is connected to the connection node between the filter inductor and the impedance matching circuit, and the second end of the filter capacitor is grounded. The target impedance is configured to be positively correlated with the target inductance value of the filter inductor.

8. The method of claim 4, wherein, The debugging method for the NFC matching circuit also includes: When the resonant circuit and the impedance matching circuit are in a connected state, the first end of the receiving circuit is connected to the receiving end of the NFC controller, and the second end of the receiving circuit is connected to the connection node between the EMC filter and the matching unit. The performance of the NFC matching circuit is tested to obtain the first receiving load modulation amplitude. When the resonant circuit and the impedance matching circuit are in a connected state, the first end of the receiving circuit is connected to the receiving end of the NFC controller, and the second end of the receiving circuit is connected to the connection node between the matching unit and the NFC antenna. The performance of the NFC matching circuit is tested to obtain the second receiving load modulation amplitude. If the larger of the first received load modulation amplitude and the second received load modulation amplitude is greater than a preset load modulation amplitude threshold, then the target element parameters of the receiving circuit are determined, and the second end of the receiving circuit is determined to be connected to the connection node corresponding to the larger value.

9. The method of claim 1, wherein, The target resonant frequency is 15MHz.

10. The method of commissioning an NFC matching circuit according to any one of claims 1-9, wherein, The debugging method for the NFC matching circuit also includes: Obtain the target performance metrics corresponding to the target application scenario; The NFC matching circuit was subjected to performance testing to obtain the measured performance indicators of the NFC matching circuit. When the measured performance indicators of the NFC matching circuit do not meet the target performance indicators, the target component parameters of the resonant circuit are adjusted.

11. The method of claim 10, wherein, The acquisition of the target performance metrics corresponding to the target application scenario includes: Obtain the target transmit power corresponding to the target application scenario; The performance testing of the NFC matching circuit to obtain the measured performance indicators of the NFC matching circuit includes: The NFC matching circuit was subjected to performance testing to obtain the measured transmission power of the NFC matching circuit. When the measured performance indicators of the NFC matching circuit do not meet the target performance indicators, adjusting the target component parameters of the resonant circuit includes: When the measured transmission power of the NFC matching circuit is less than the target transmission power, the target inductance value of the resonant inductor and / or the target capacitance value of the resonant capacitor are increased.

12. The method of claim 10, wherein, The acquisition of the target performance metrics corresponding to the target application scenario includes: Obtain the target received load modulation amplitude corresponding to the target application scenario; The performance testing of the NFC matching circuit to obtain the measured performance indicators of the NFC matching circuit includes: The NFC matching circuit was subjected to performance testing to obtain the measured received load modulation amplitude of the NFC matching circuit. When the measured performance indicators of the NFC matching circuit do not meet the target performance indicators, adjusting the target component parameters of the resonant circuit includes: When the measured receive load modulation amplitude of the NFC matching circuit is less than the target receive load modulation amplitude, the target inductance value of the resonant inductor and / or the target capacitance value of the resonant capacitor are reduced.

13. An NFC matching circuit, wherein, Including resonant circuits and impedance matching circuits; The resonant circuit is connected to the two transmitters of the NFC controller and is used to resonate the differential output of the NFC controller to output a single-ended signal. The first terminal of the impedance matching circuit is connected to the resonant circuit, and the second terminal of the impedance matching circuit is used to connect to the NFC antenna. When the resonant circuit and the impedance matching circuit are in the open state, the measured resonant frequency of the resonant circuit is configured to be equal to the target resonant frequency, which is greater than or equal to the operating frequency of the NFC antenna. When the resonant circuit and the impedance matching circuit are in the open state, the matching impedance from the input terminal of the impedance matching circuit to ground simultaneously satisfies the first condition and the second condition. The first condition is that the impedance curve of the impedance matching circuit has a first resonant point, a second resonant point, and a third resonant point with successively increasing frequencies on the Smith chart. The impedances of the first resonant point and the third resonant point are the same, and the frequency of the second resonant point is the operating frequency of the NFC antenna. The second condition is that the matching impedance corresponding to the operating frequency of the NFC antenna is configured to be equal to the target impedance.

14. The NFC matching circuit of claim 13, wherein, The resonant circuit includes a resonant inductor and a resonant capacitor; the first end of the resonant inductor is connected to one transmitting end of the NFC controller, and the second end of the resonant inductor is connected to the impedance matching circuit; the first end of the resonant capacitor is connected to the other transmitting end of the NFC controller, and the second end of the resonant capacitor is connected to the impedance matching circuit. When the resonant circuit and the impedance matching circuit are in the open state, the measured resonant frequency of the series circuit formed by the resonant inductor and the resonant capacitor is configured to be equal to the target resonant frequency, which is 15MHz.

15. The NFC matching circuit of claim 13, wherein, The impedance matching circuit includes an EMC filter and a matching unit; The EMC filter includes a filter inductor and a filter capacitor; the first end of the filter inductor is connected to the resonant circuit, and the second end of the filter inductor is connected to the matching unit; the first end of the filter capacitor is connected to the connection node between the filter inductor and the matching unit, and the second end of the filter capacitor is grounded; the target impedance is configured to be positively correlated with the target inductance value of the filter inductor. The matching unit includes a first matching capacitor and a second matching capacitor; a first terminal of the first matching capacitor is connected to the EMC filter, and a second terminal of the first matching capacitor is connected to the NFC antenna; a first terminal of the second matching capacitor is connected to the connection node between the EMC filter and the NFC antenna, and a second terminal of the second matching capacitor is grounded. The target capacitance value of the second matching capacitor is configured to be equal to the difference between the standard capacitance value and a preset change. The standard capacitance value is the capacitance value of the second matching capacitor when the resonant circuit and the impedance matching circuit are in an open state, and the matching impedance from the input terminal of the impedance matching circuit to ground simultaneously satisfies the first condition and the second condition. The preset variation range is 0.025 to 0.25 times the standard capacitance value of the second matching capacitor.

16. The NFC matching circuit of claim 15, wherein, The NFC matching circuit further includes a receiving circuit. The first end of the receiving circuit is connected to the receiving end of the NFC controller, and the second end of the receiving circuit is connected to the connection node between the EMC filter and the matching unit, or the second end of the receiving circuit is connected to the connection node between the matching unit and the NFC antenna.

17. The NFC matching circuit according to claim 13, wherein, The NFC matching circuit also includes an impedance resistor, the first end of which is connected to the impedance matching circuit, and the second end of which is connected to the NFC antenna to reduce the Q value of the NFC antenna.

18. An electronic device, wherein, Includes an NFC controller, an NFC antenna, and an NFC matching circuit as described in any one of claims 13-17; The NFC matching circuit is connected to the NFC controller and the NFC antenna.

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