Auto-centering of sensor frequency of a resonant sensor
A system may include a resistive-inductive-capacitive sensor, a driver configured to drive the resistive-inductive-capacitive sensor at a driving frequency, and a measurement circuit communicatively coupled to the resistive-inductive-capacitive sensor and configured to determine a measured change in a resonant frequency of the resistive-inductive-capacitive sensor and based on the measured change, modify the driving frequency.
1. A system comprising:
a resistive-inductive-capacitive sensor;
a driver configured to drive the resistive-inductive-capacitive sensor at a driving frequency; and
a measurement circuit communicatively coupled to the resistive-inductive-capacitive sensor and configured to:
determine a measured change in a resonant frequency of the resistive-inductive-capacitive sensor; and
based on the measured change, modify the driving frequency when the measured change exceeds a threshold value.
2. The system of claim 1 , wherein the threshold value is based on a quality factor of the resistive-inductive-capacitive sensor.
3. The system of claim 1 , wherein the measurement circuit further comprises a quality factor estimator configured to estimate a quality factor of the resistive-inductive-capacitive sensor.
4. The system of claim 3 , wherein the quality factor estimator is configured to estimate the quality factor based on at least one of phase information associated with the resistive-inductive-capacitive sensor and amplitude information associated with the resistive-inductive-capacitive sensor.
5. The system of claim 3 , wherein the measurement circuit is further configured to modify the driving frequency based on the quality factor.
6. The system of claim 1 , wherein the measurement circuit is configured to modify the driving frequency by:
determining a change in phase information associated with the resistive-inductive-capacitive sensor; and
adjusting the driving frequency by a frequency change based on the phase information and a slope of a phase-versus-frequency curve of the resistive-inductive-capacitive sensor.
7. The system of claim 6 , wherein the measurement circuit is configured to calculate the frequency change to be equal to the change in phase information divided by the slope.
8. The system of claim 7 , wherein:
the measurement circuit further comprises a quality factor estimator configured to estimate a quality factor of the resistive-inductive-capacitive sensor; and
the measurement circuit is configured to calculate the slope based on the quality factor.
9. The system of claim 1 , wherein the measurement circuit is configured to modify the driving frequency to match a resonance frequency of the resistive-inductive-capacitive sensor.
10. The system of claim 1 , wherein the measurement circuit is configured to verify that modification of the drive frequency results in the drive frequency matching a resonance frequency of the resistive-inductive-capacitive sensor.
11. The system of claim 1 , wherein the measurement circuit is configured to modify the driving frequency such that the system operates in a linear region of a phase-versus-frequency curve of the resistive-inductive-capacitive sensor.
12. The system of claim 1 , wherein the measurement circuit is configured to:
blank measurement of phase information of the resistive-inductive-capacitive sensor for a measurement cycle following modification of the driving frequency; and
ensure that the phase information change caused by the modification of the driving frequency is not communicated to downstream processing.
13. The system of claim 1 , wherein the measurement circuit is configured to:
measure phase information associated with the resistive-inductive-capacitive sensor; and
based on the phase information, determine a displacement of a mechanical member relative to the resonant sensor, wherein the displacement of the mechanical member causes a change in an impedance of the resonant sensor.
14. A method comprising, in a system comprising a resistive-inductive-capacitive sensor and a driver configured to drive the resistive-inductive-capacitive sensor at a driving frequency:
determining a measured change in a resonant frequency of the resistive-inductive-capacitive sensor; and
based on the measured change, modifying the driving frequency when the measured change exceeds a threshold value.
15. The method of claim 14 , wherein the threshold value is based on a quality factor of the resistive-inductive-capacitive sensor.
16. The method of claim 14 , further comprising estimating a quality factor of the resistive-inductive-capacitive sensor.
17. The method of claim 16 , further comprising estimating the quality factor based on at least one of phase information associated with the resistive-inductive-capacitive sensor and amplitude information associated with the resistive-inductive-capacitive sensor.
18. The method of claim 16 , further comprising modifying the driving frequency based on the quality factor.
19. The method of claim 14 , further comprising modifying the driving frequency by:
determining a change in phase information associated with the resistive-inductive-capacitive sensor; and
adjusting the driving frequency by a frequency change based on the phase information and a slope of a phase-versus-frequency curve of the resistive-inductive-capacitive sensor.
20. The method of claim 19 , further comprising calculating the frequency change to be equal to the change in phase information divided by the slope.
21. The method of claim 20 , further comprising:
estimating a quality factor of the resistive-inductive-capacitive sensor; and
calculating the slope based on the quality factor.
22. The method of claim 14 , further comprising modifying the driving frequency to match a resonance frequency of the resistive-inductive-capacitive sensor.
23. The method of claim 14 , further comprising verifying that modification of the drive frequency results in the drive frequency matching a resonance frequency of the resistive-inductive-capacitive sensor.
24. The method of claim 14 , further comprising modifying the driving frequency such that the system operates in a linear region of a phase-versus-frequency curve of the resistive-inductive-capacitive sensor.
25. The method of claim 14 , further comprising:
blanking measurement of phase information of the resistive-inductive-capacitive sensor for a measurement cycle following modification of the driving frequency; and
ensuring that the phase information change caused by the modification of the driving frequency is not communicated to downstream processing.
26. The method of claim 14 , further comprising:
measuring phase information associated with the resistive-inductive-capacitive sensor; and
based on the phase information, determining a displacement of a mechanical member relative to the resonant sensor, wherein the displacement of the mechanical member causes a change in an impedance of the resonant sensor.
27. An integrated circuit comprising:
a measurement circuit configured to communicatively couple to a resistive-inductive-capacitive sensor driven at a driving frequency, the measurement circuit further configured to:
determine a measured change in a resonant frequency of the resistive-inductive-capacitive sensor; and
based on the measured change, modify the driving frequency when the measured change exceeds a threshold value.