COMPENSATION CIRCUIT FOR A TX-RX CAPACITIVE SENSOR
First Claim
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1. An apparatus, comprising:
- a capacitive sensor including a transmit electrode and a receive electrode, wherein the receive electrode is capacitively coupled with the transmit electrode;
a signal generator coupled with the transmit electrode and configured to generate an induced current waveform at the receive electrode by applying a transmit signal to the transmit electrode;
a demodulation circuit coupled with the receive electrode, wherein the demodulation circuit is configured to output a rectified current based on the induced current waveform; and
a compensation circuit coupled with the demodulation circuit, wherein the compensation circuit is configured to add a compensation current to the rectified current to generate a compensated current waveform.
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Abstract
A capacitive sensor may include a transmit electrode and a receive electrode capacitively coupled with the transmit electrode. A capacitance sensing circuit senses a capacitance between the transmit and receive electrodes by applying a signal to the transmit electrode and rectifying a current waveform induced at the receive electrode. A compensation circuit reduces the effect of a mutual and parasitic capacitances of the transmit and receive electrode pair by adding a compensation current to the rectified current.
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Citations
20 Claims
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1. An apparatus, comprising:
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a capacitive sensor including a transmit electrode and a receive electrode, wherein the receive electrode is capacitively coupled with the transmit electrode; a signal generator coupled with the transmit electrode and configured to generate an induced current waveform at the receive electrode by applying a transmit signal to the transmit electrode; a demodulation circuit coupled with the receive electrode, wherein the demodulation circuit is configured to output a rectified current based on the induced current waveform; and a compensation circuit coupled with the demodulation circuit, wherein the compensation circuit is configured to add a compensation current to the rectified current to generate a compensated current waveform. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method, comprising:
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applying a transmit signal to a transmit electrode capacitively coupled to a receive electrode to generate an induced current waveform at the receive electrode; rectifying the induced current waveform to generate a rectified current; and adding a compensation current to the rectified current to generate a compensated current waveform. - View Dependent Claims (13, 14, 15, 16, 17, 18)
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19. An apparatus, comprising:
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means for generating an induced current waveform based on a capacitance value of a capacitive sensor; means for generating a rectified current based on the induced current waveform; and means for generating a compensated current waveform by adding a compensation current to the rectified current. - View Dependent Claims (20)
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Specification