Techniques for locally improving signal to noise in a capacitive touch sensor
First Claim
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1. A system comprising:
- a data processing apparatus;
a capacitive touch sensor configured to interact with the data processing apparatus; and
a liquid crystal display,the system is configured to;
determine a noise frequency in the capacitive touch sensor;
identify that the noise frequency is a function of a frequency of the liquid crystal display; and
determine an excitation frequency for the capacitive touch sensor as a function of the determined noise frequency, wherein when determining the excitation frequency the system is further configured to;
select an initial excitation frequency for the capacitive touch sensor;
compute a cross-correlation between the noise frequency and the initial excitation frequency over an integration period, wherein the computation of the cross-correlation is presentable in a sinc-like waveform with at least one peak and at least two nulls; and
select the excitation frequency for the capacitive touch sensor by selecting a frequency at one of the nulls in the sinc-like waveform and assigning the determined excitation frequency to be a same frequency as the frequency at the selected null, thereby selecting an excitation waveform corresponding to the selected excitation frequency.
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Abstract
Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for digital signal processing (DSP) techniques for generally improving a signal-to-noise ratio (SNR) of capacitive touch sensors.
63 Citations
8 Claims
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1. A system comprising:
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a data processing apparatus; a capacitive touch sensor configured to interact with the data processing apparatus; and a liquid crystal display, the system is configured to; determine a noise frequency in the capacitive touch sensor; identify that the noise frequency is a function of a frequency of the liquid crystal display; and determine an excitation frequency for the capacitive touch sensor as a function of the determined noise frequency, wherein when determining the excitation frequency the system is further configured to; select an initial excitation frequency for the capacitive touch sensor; compute a cross-correlation between the noise frequency and the initial excitation frequency over an integration period, wherein the computation of the cross-correlation is presentable in a sinc-like waveform with at least one peak and at least two nulls; and select the excitation frequency for the capacitive touch sensor by selecting a frequency at one of the nulls in the sinc-like waveform and assigning the determined excitation frequency to be a same frequency as the frequency at the selected null, thereby selecting an excitation waveform corresponding to the selected excitation frequency. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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Specification