Capacitive sensor filtering apparatus, method, and system
First Claim
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1. A method for operating a capacitive sensor, comprising:
- providing a sensor electrode;
periodically exciting the sensor electrode and thereby periodically generating an electric field about the sensor electrode and a capacitance between the sensor electrode and a reference potential;
periodically determining in the time domain values of capacitance between the sensor electrode and the reference potential;
continuously transforming a rolling sample of the periodically-determined values of capacitance from the time domain to a plurality of data signals in the frequency domain using a Fourier Transform, each of the data signals in a corresponding frequency bin resulting from the Fourier Transform and each of the data signals comprising values related to capacitance for corresponding samples of the rolling sample;
analyzing in the frequency domain at least one of the plurality of data signals in the corresponding frequency bin; and
determining whether a touch event has occurred based on the analysis in the frequency domain of the at least one of the plurality of data signals in the corresponding frequency bin;
wherein the rolling sample is an n-point rolling sample including a current sample and n−
1 samples immediately preceding the current sample, wherein the n−
1 samples include a last sample, wherein n=2x and x is an integer greater than or equal to 2, and wherein performance of the Fourier Transform yields n frequency bins numbered 0 through n−
1.
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Abstract
A transform is used to transform raw sensor data from the time domain to the frequency or sequency domain. The transformed data falls into several signal bins. The transformed data in at least one of the signal bins is analyzed to determine whether a touch event or release event has occurred.
65 Citations
17 Claims
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1. A method for operating a capacitive sensor, comprising:
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providing a sensor electrode; periodically exciting the sensor electrode and thereby periodically generating an electric field about the sensor electrode and a capacitance between the sensor electrode and a reference potential; periodically determining in the time domain values of capacitance between the sensor electrode and the reference potential; continuously transforming a rolling sample of the periodically-determined values of capacitance from the time domain to a plurality of data signals in the frequency domain using a Fourier Transform, each of the data signals in a corresponding frequency bin resulting from the Fourier Transform and each of the data signals comprising values related to capacitance for corresponding samples of the rolling sample; analyzing in the frequency domain at least one of the plurality of data signals in the corresponding frequency bin; and determining whether a touch event has occurred based on the analysis in the frequency domain of the at least one of the plurality of data signals in the corresponding frequency bin; wherein the rolling sample is an n-point rolling sample including a current sample and n−
1 samples immediately preceding the current sample, wherein the n−
1 samples include a last sample, wherein n=2x and x is an integer greater than or equal to 2, and wherein performance of the Fourier Transform yields n frequency bins numbered 0 through n−
1. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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Specification