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Methods and systems for detecting noise in a position sensor using minor shifts in sensing frequency

  • US 7,031,886 B1
  • Filed: 12/14/2004
  • Issued: 04/18/2006
  • Est. Priority Date: 12/14/2004
  • Status: Active Grant
First Claim
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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:

  • 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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