SYSTEM AND METHOD FOR DETECTING INTERFERNCE IN A SENSOR DEVICE USING PHASE SHIFTING
First Claim
1. An apparatus configured to detect interference in an output signal of a capacitive sensor, wherein the capacitive sensor is configured to modulate a carrier signal in response to a stimulus provided in a sensing region, wherein the output signal is demodulated using a demodulation signal and wherein the output signal is filtered by a demodulation filter having a demodulation filter bandwidth, the apparatus comprising:
- a signal generator configured to apply a carrier signal to the capacitive sensor, the capacitive sensor producing sensor outputs in response to the applied carrier signal, wherein the carrier signal switches between a plurality of phases at a switching rate that is less than the demodulation filter bandwidth, and wherein the demodulation signal is synchronous with the carrier signal;
an interference detection filter configured to filter from the sensor outputs an effect produced by the stimulus to thereby produce at least one interference output; and
an interference measuring device configured to determine a first level of interference in the at least one interference output.
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Accused Products
Abstract
A capacitive sensor device and method is configured to respond a stimulus provided in a sensing region with an output signal. A signal generator is configured to apply a carrier signal to the capacitive sensor device. The carrier signal is switched between a plurality of phases at a switching rate, where the switching rate is less than a demodulation filter bandwidth. The result of the carrier phase shifting is that effects of interference in the output signal are frequency shifted away from the effects of user applied stimulus. An interference detection filter is configured to filter from the sensor outputs at least one effect produced by the stimulus. An interference measuring device is configured to determine a level of interference in the at least one interference output. Thus, the system can detect interference in the output of the capacitive sensor device.
37 Citations
21 Claims
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1. An apparatus configured to detect interference in an output signal of a capacitive sensor, wherein the capacitive sensor is configured to modulate a carrier signal in response to a stimulus provided in a sensing region, wherein the output signal is demodulated using a demodulation signal and wherein the output signal is filtered by a demodulation filter having a demodulation filter bandwidth, the apparatus comprising:
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a signal generator configured to apply a carrier signal to the capacitive sensor, the capacitive sensor producing sensor outputs in response to the applied carrier signal, wherein the carrier signal switches between a plurality of phases at a switching rate that is less than the demodulation filter bandwidth, and wherein the demodulation signal is synchronous with the carrier signal; an interference detection filter configured to filter from the sensor outputs an effect produced by the stimulus to thereby produce at least one interference output; and an interference measuring device configured to determine a first level of interference in the at least one interference output. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method of detecting interference in an output signal provided by a sensor configured to modulate a carrier signal in response to the proximity of a stimulus, wherein the output signal is synchronously demodulated with a demodulation signal and filtered by a demodulation filter having a demodulation filter bandwidth, the method comprising the steps of:
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applying the carrier signal to the sensor, the sensor producing sensor outputs in response to the applied carrier signal, wherein the carrier signal switches between a plurality of phases at a switching rate that is less than the demodulation filter bandwidth; filtering from the sensor outputs an effect produced by the stimulus to thereby produce at least one interference output; determining interference contained within the at least one interference output; and providing an indication of the determined interference. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20)
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21. An input device for detecting a user input, the input device comprising:
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a sensor configured for detecting a stimulus of the user input and for providing an output signal in response thereto; a processor in communication with the sensor, the processor is configured to; generate a carrier signal having a sensing frequency; demodulate the output signal of the sensor with the carrier signal; filter the demodulated output signal with a filter having a demodulation filter bandwidth; apply the carrier signal to the sensor, the applied carrier signal switching between at least a first phase and a second phase, the sensor producing at least a first output corresponding to the first phase and a second output corresponding to a the second phase in response to the applied carrier signal, and wherein the switching is performed at a frequency less than the demodulation filter bandwidth; filter at least some of an effect produced by the stimulus from at least the first and second outputs to thereby produce at least one filtered output; determine a measure of interference contained within the at least one filtered output; and shift the sensing frequency to an alternate sensing frequency if the measure of interference is determined to be beyond a threshold.
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Specification