Methods and systems for detecting noise in a position sensor using minor shifts in sensing frequency
First Claim
1. A method of detecting noise in an output provided by a sensing region configured to modulate a carrier signal in response to the proximity of a stimulus, wherein the output is synchronously demodulated with the carrier signal and filtered by a demodulation filter having a demodulation filter bandwidth, the method comprising the steps of:
- applying the carrier signal at a first frequency and at a second frequency to thereby produce a first output and a second output, respectively, wherein the first and second frequencies are distinct from each other and wherein a difference between the first and second frequencies is less than the demodulation filter bandwidth;
removing at least some of an effect produced by the stimulus from the first and second outputs to thereby produce a first and a second filtered output, respectively; and
processing the first and second filtered outputs to detect noise contained therein.
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Abstract
Methods, systems and devices are described for detecting noise in a touchpad or other sensor that produces an output in response to a stimulus that is applied at or near a sensing region. According to various embodiments, a carrier signal is applied to the sensing region at two or more frequencies to thereby produce an output from the sensing region at each frequency. Each of the outputs is demodulated and filtered by a demodulation filter having a demodulation filter bandwidth. The various frequencies applied to the carrier signal are selected such that a difference between the frequencies is less than the demodulation filter bandwidth. At least some of the effects of the stimulus are removed from the outputs produced by the various carrier frequencies to produce two or more filtered outputs. The filtered outputs are then added, combined or otherwise processed to detect noise contained therein. If noise contained in one or more of the filtered outputs reaches an unacceptable level, the carrier signal may be shifted to a new sensing frequency for subsequent operation of the sensor.
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Citations
36 Claims
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1. A method of detecting noise in an output provided by a sensing region configured to modulate a carrier signal in response to the proximity of a stimulus, wherein the output is synchronously demodulated with the carrier 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 at a first frequency and at a second frequency to thereby produce a first output and a second output, respectively, wherein the first and second frequencies are distinct from each other and wherein a difference between the first and second frequencies is less than the demodulation filter bandwidth; removing at least some of an effect produced by the stimulus from the first and second outputs to thereby produce a first and a second filtered output, respectively; and processing the first and second filtered outputs to detect noise contained therein. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A method of operating a sensor configured for detecting a user input in proximity to a sensing region demodulated by a carrier signal having a sensing frequency and filtered by a demodulation filter having a demodulation filter bandwidth, the method comprising the steps of:
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applying a plurality of carrier signals to the sensing region to produce a plurality of noise measurement signals, wherein each of the plurality of carrier signals has a distinct frequency, and wherein a total difference in the distinct frequencies is less than the demodulation filter bandwidth; filtering each of the plurality of noise measurement signals to substantially remove at least some of an effect produced by the user input, thereby producing a plurality of filtered outputs; determining an amount of noise identified in at least one of the plurality of filtered outputs; and shifting the sensing frequency to an alternate sensing frequency if the amount of noise exceeds a predetermined threshold. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25)
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26. A software application configured to detect noise in an output provided by a sensing region configured to modulate a carrier signal in response to the proximity of a stimulus, wherein the output is synchronously demodulated with the carrier signal and filtered by a demodulation filter having a demodulation filter bandwidth, the software application comprising:
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a first code module configured to direct the application of a carrier signal at a first frequency and at a second frequency to the sensing region to thereby produce a first output and a second output, respectively, wherein the first and second frequencies are distinct from each other and wherein a difference between the first and second frequencies is less than the demodulation filter bandwidth; a second code module configured to remove at least some of an effect produced by the stimulus from the first and second outputs to thereby produce a first and a second filtered output, respectively; and a third code module configured to process the first and second filtered outputs to detect noise contained therein. - View Dependent Claims (27, 28)
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29. An input device for detecting a user input, the input device comprising:
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a sensing region configured for detecting the user input and for providing an output in response thereto; a signal generator configured to produce a carrier signal having a sensing frequency; a demodulator coupled to the sensing region and configured for demodulating the output of the sensing region with the carrier signal; a demodulation filter associated with the demodulator and having a demodulation filter bandwidth; and a processor in communication with the signal generator and the demodulation filter, wherein the processor is configured; to communicate with the signal generator to direct the application of the carrier signal at a first frequency and at a second frequency to the sensing region, wherein the first and second frequencies are distinct from each other and wherein a difference between the first and second frequencies is less than the demodulation filter bandwidth; to receive a first and a second noise measurement signal from the demodulation filter in response to the first and second frequencies, respectively; to substantially remove any effects of the user input from the first and second noise measurement signals to thereby produce a first and a second filtered output, respectively; and to determine an amount of noise identified in at least one of the first and second filtered output and to communicate with the signal generator to shift the sensing frequency to an alternate sensing frequency if the amount of noise exceeds a predetermined threshold. - View Dependent Claims (30, 31, 32)
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33. An apparatus configured to detect noise in an output of a capacitive sensor that is configured to respond to a stimulus provided in proximity to the sensing region, wherein the output is filtered by a demodulation filter having a demodulation filter bandwidth, the apparatus comprising:
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means for directing the application of a carrier signal at a first frequency and at a second frequency to the sensing region to thereby produce a first output and a second output, respectively, wherein the first and second frequencies are distinct from each other and wherein a difference between the first and second frequencies is less than the demodulation filter bandwidth; means for removing effects of the stimulus from the first and second outputs to thereby produce a first and a second filtered output, respectively; and means for processing the first and second filtered outputs to detect noise contained therein.
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34. A sensor configured for detecting a user input in proximity to a sensing region demodulated by a carrier signal having a sensing frequency and filtered by a demodulation filter having a demodulation filter bandwidth, the sensor comprising:
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means for applying a plurality of carrier signals to the sensing region to produce a plurality of noise measurement signals, wherein each of the plurality of carrier signals has a distinct frequency, and wherein a total difference in the distinct frequencies is less than the demodulation filter bandwidth; means for filtering each of the plurality of noise measurement signals to substantially remove any effects of the user input, thereby producing a plurality of filtered outputs; means for determining an amount of noise identified in at least one of the plurality of filtered outputs; and means for shifting the sensing frequency to an alternate sensing frequency if the amount of noise exceeds a predetermined threshold. - View Dependent Claims (35, 36)
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Specification