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Signal processing apparatus

  • US 8,126,528 B2
  • Filed: 03/24/2009
  • Issued: 02/28/2012
  • Est. Priority Date: 10/07/1994
  • Status: Expired due to Fees
First Claim
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1. In a signal processor, a method of determining a measurement value for a characteristic of arterial blood, the method comprising:

  • receiving a first time-domain signal that is indicative of light of a first wavelength that has been attenuated by body tissue carrying arterial blood;

    receiving a second time-domain signal that is indicative of light of a second wavelength that has been attenuated by the body tissue carrying arterial blood;

    electronically transforming the first and second time-domain signals into respective first and second frequency-domain signals;

    electronically determining a comparison value for each of a plurality of non-zero frequency components of the first and second frequency-domain signals, each comparison value comprising a comparison of the amount of a frequency component in the first frequency-domain signal versus the amount of that frequency component in the second frequency-domain signal;

    electronically selecting a frequency component that exhibits physiological characteristics of arterial blood using, at least in part, the corresponding comparison value; and

    electronically determining the measurement value for the characteristic of arterial blood using the selected frequency component.

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