Capacitance measurement device with reduced noise
First Claim
1. A method for providing projective capacitive sensor detection with one or more capacitive sensors comprising a transmitting electrode and a receiving electrode, the method comprising:
- generating a stimulus signal by a signal generator and feeding the stimulus to the transmitting electrode, wherein the stimulus has a stimulus start and a stimulus end,while the stimulus signal is transmitted from the transmitting electrode to the receiving electrode, discharging the receiving electrode for a predetermined time interval before each rising edge of the stimulus and charging the receiving electrode for a predetermined time interval before each failing edge of the stimulus signal thereby generating pairs of modulated samples by a sampling circuit and converting the samples by an analog-to-digital converter;
demodulating the samples and forming data packets, each data packet comprising a plurality of digital samples generated during a sample period having a beginning time corresponding with the stimulus start and an ending time corresponding with the stimulus end;
for each data packet, applying a weighting factor to each of the plurality of digital samples in the respective data packet by providing less gain for digital samples near (a) the beginning time of the sample period and (b) the ending time of the sample period, as compared with digital samples near a center of the respective data packet; and
integrating the weighted digital samples to generate a single output value for each data packet.
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Abstract
A method or sensor arrangement for providing capacitive sensor detection with at least one capacitive sensor comprises a transmitting electrode and a receiving electrode. A stimulus at the transmitting electrode is generated and a signal is received from the receiving electrode and data packets are generated, each packet comprising a plurality of samples. The plurality of samples are weighted by providing less gain at a beginning and end of each packet with respect to a center of each packet; and the weighted samples are integrated to generate an output signal for each packet.
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Citations
28 Claims
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1. A method for providing projective capacitive sensor detection with one or more capacitive sensors comprising a transmitting electrode and a receiving electrode, the method comprising:
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generating a stimulus signal by a signal generator and feeding the stimulus to the transmitting electrode, wherein the stimulus has a stimulus start and a stimulus end, while the stimulus signal is transmitted from the transmitting electrode to the receiving electrode, discharging the receiving electrode for a predetermined time interval before each rising edge of the stimulus and charging the receiving electrode for a predetermined time interval before each failing edge of the stimulus signal thereby generating pairs of modulated samples by a sampling circuit and converting the samples by an analog-to-digital converter; demodulating the samples and forming data packets, each data packet comprising a plurality of digital samples generated during a sample period having a beginning time corresponding with the stimulus start and an ending time corresponding with the stimulus end; for each data packet, applying a weighting factor to each of the plurality of digital samples in the respective data packet by providing less gain for digital samples near (a) the beginning time of the sample period and (b) the ending time of the sample period, as compared with digital samples near a center of the respective data packet; and integrating the weighted digital samples to generate a single output value for each data packet. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A sensor arrangement with at least one capacitive sensor comprising:
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a generator configured to generate a stimulus signal having a stimulus start and a stimulus end; a transmitting electrode configured to receive the stimulus signal, a receiving electrode capacitively coupled with the transmitting electrode and configured to receive a signal from the transmitting electrode, a charge circuit coupled with the receiving electrode and configured to discharge the receiving electrode for a predetermined time interval before each rising edge of the stimulus and to charge the receiving electrode for a predetermining time interval before each falling edge of the stimulus signal to generate pairs of modulated samples by a sampling circuit; an analog-to-digital converter coupled with the sampling circuit and configured to convert the pairs of modulated samples to subsequent digital samples; and an post processing circuit coupled with the analog-to-digital converter and configured to demodulate a plurality of subsequent digital samples in a data packet, each data packet comprising a plurality of pairs of modulated digital samples generated during a sample period having a beginning time corresponding with stimulus start and an ending time corresponding with stimulus end, wherein the plurality of digital samples in each data packet are weighted by providing less gain for digital samples near (a) the beginning time of the sample period and (b) the ending time of the sample period, as compared with samples near a center of the respective data packet, and wherein the post-processing circuit is further configured to integrate the weighted digital samples to generate a single output signal for each data packet. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28)
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Specification