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Method and apparatus for demodulating signals in a pulse oximetry system

  • US 8,718,737 B2
  • Filed: 04/02/2012
  • Issued: 05/06/2014
  • Est. Priority Date: 04/14/1997
  • Status: Expired due to Fees
First Claim
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1. A method of determining an indication of a physiological parameter by demodulating a composite output signal from a detector of a noninvasive optical sensor, the method comprising:

  • activating at least one light source to cause a first emission at a first wavelength;

    activating the at least one light source to cause a second emission at a second wavelength at least once before a reactivation of the at least one light source;

    detecting the composite output signal indicative of an attenuation by said body tissue of said first and second emissions;

    selectively demodulating only certain harmonics of desired components of the detected composite signal into a first intensity signal responsive to said attenuation of said first emission and a second intensity signal responsive to said attenuation of said second emission; and

    determining an indication of a physiological parameter of said body tissue based on one or more of said first and second intensity signals.

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