ASYNCHRONOUS INTERFERENCE DETECTION IN A CAPACITIVE SENSING SYSTEM
First Claim
1. A processing system for a capacitive sensing device, comprising:
- a sensor module comprising a receiver, coupled to a sensor electrode, configured to receive a capacitive sensing signal, the receiver including;
an in-phase channel configured to mix the capacitive sensing signal with a local oscillator signal substantially in phase with the capacitive sensing signal; and
a quadrature channel configured to mix the capacitive sensing signal with a phase-shifted signal near ninety degrees out of phase with the capacitive sensing signal; and
a determination module configured to measure a change in capacitance in response to a demodulated signal of the in-phase channel concurrently with measuring a non-coherent signal in response to a demodulated signal of the quadrature channel.
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Abstract
In an example, a processing system for a capacitive sensing device includes a sensor module and a determination module. The sensor module comprises a receiver, coupled to a sensor electrode, configured to receive a capacitive sensing signal. The receiver includes an in-phase channel and a quadrature channel. The in-phase channel is configured to mix the capacitive sensing signal with a local oscillator signal substantially in phase with the capacitive sensing signal. The quadrature channel is configured to mix the capacitive sensing signal with a phase-shifted signal near ninety degrees out of phase with the capacitive sensing signal. The determination module is configured to measure a change in capacitance in response to a demodulated signal of the in-phase channel concurrently with measuring a non-coherent signal in response to a demodulated signal of the quadrature channel.
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Citations
20 Claims
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1. A processing system for a capacitive sensing device, comprising:
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a sensor module comprising a receiver, coupled to a sensor electrode, configured to receive a capacitive sensing signal, the receiver including; an in-phase channel configured to mix the capacitive sensing signal with a local oscillator signal substantially in phase with the capacitive sensing signal; and a quadrature channel configured to mix the capacitive sensing signal with a phase-shifted signal near ninety degrees out of phase with the capacitive sensing signal; and a determination module configured to measure a change in capacitance in response to a demodulated signal of the in-phase channel concurrently with measuring a non-coherent signal in response to a demodulated signal of the quadrature channel. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. An input device, comprising:
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a plurality of sensor electrodes; a processing system, coupled to the plurality of sensor electrodes, the processing system configured to; receive capacitive sensing signals; mix the capacitive sensing signals with a local oscillator signal substantially in-phase with the capacitive sensing signal to generate in-phase demodulated signals; mix the capacitive sensing signals with a phase-shifted signal near ninety degrees out of phase with the capacitive sensing signals to generate quadrature demodulated signals; measure changes in capacitance in response to the in-phase demodulated signals; and measure non-coherent signals in response to the quadrature demodulated signals. - View Dependent Claims (13, 14, 15, 16)
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17. A method of operating a capacitive sensing device having a plurality of sensor electrodes, the method comprising:
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receiving capacitive sensing signals derived from the plurality of sensor electrodes; mixing the capacitive sensing signals with a local oscillator signal substantially in-phase with the capacitive sensing signals to generate in-phase demodulated signals; mixing the capacitive sensing signals with a phase-shifted signal near ninety degrees out of phase with the capacitive sensing signals to generate quadrature demodulated signals; measuring changes in capacitance in response to the in-phase demodulated signals; and measuring non-coherent signals in response to the quadrature demodulated signals. - View Dependent Claims (18, 19, 20)
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Specification