Drift suppression method, proximity sensor and wireless device
AssigneeSemtech Corporation
InventorChaouki Rouaissia
Life of this patent
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Abstract
A portable device including a capacitive proximity sensor can suppress a drift superimposed to the capacitive proximity signal and the corresponding method. A processor generates a baseline value by integrating a series of values that are derived from the slope of the proximity signal, when the slope is within stated limits, or a fixed value outside of the stated limits.
Claims16
A method of suppressing a drift superimposed to a proximity signal generated by a capacitive sensor, the method including:
- receiving a series of samples of the proximity signal,
- computing repeatedly an average slope of the proximity signal from the received samples
- comparing the average slope with a threshold,
- updating a baseline value by adding a value derived from the proximity signal when the average slope is below the threshold or a fixed value when the average slope is above the threshold,
- obtain a drift-suppressed proximity signal by subtracting the baseline value from the proximity signal.
A capacitive proximity sensor for a portable device, comprising a sense electrode and a readout circuit configured to read a self-capacitance of the sense electrode and provide a proximity signal including a series of capacitance values, the capacitive proximity sensor comprising a drift suppression unit configured to suppressing a drift superimposed on the proximity signals by the steps of:
- computing repeatedly an average slope of the proximity signal from the capacitance values
- comparing the average slope with a threshold,
- updating a baseline value by adding a value derived from the proximity signal when the average slope is below the threshold or a fixed value when the average slope is above the threshold,
- obtain a drift-suppressed proximity signal by subtracting the baseline value from the proximity signal.
A portable wireless device comprising a proximity sensor having sense electrode and a readout circuit configured to read a self-capacitance of the sense electrode and provide a proximity signal including a series of capacitance values, the capacitive proximity sensor comprising an electronic processor configured to suppressing a drift superimposed on the proximity signals by the steps of:
- computing repeatedly an average slope of the proximity signal from the capacitance values
- comparing the average slope with a threshold,
- updating a baseline value by adding a value derived from the proximity signal when the average slope is below the threshold or a fixed value when the average slope is above the threshold,
- obtain a drift-suppressed proximity signal by subtracting the baseline value from the proximity signal.
Dependencies are inferred from the claim text.