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0021] A processor in accordance with one embodiment of the present invention removes the primary signal portions from the measured signals yielding a secondary reference which is a combination of the remaining secondary signal portions. The secondary reference is correlated to both of the secondary signal portions. The secondary reference and at least one of the measured signals are input to a correlation canceler, such as an adaptive noise canceler, which removes the random or erratic portion of the secondary signal. This yields a good approximation to a primary plethysmographic signal as measured at one of the measured signal wavelengths. As is known in the art, quantitative measurements of the amount of oxygenated arterial blood in the body ca
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In such cases, conventional filtering techniques are ineffective in extracting either the primary or secondary signal.
However, when fleshy portions of the f
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[0082] The present invention involves a system which utilizes first and second measured signals that each contain a primary signal portion and a secondary signal portion. In other words, given a first and second composite signals S.sub.1(t)=s.sub.1(t)+n.sub.1(t) and S.sub.2(t)=s.sub.2(t)+n.sub.2(t), the system of the present invention can be used to isolate either the primary signal portion s(t) or the secondary signal portion n(t). Following processing, the output of the system provides a good approximation n"(t) to the secondary signal portion n(t) or a good approximation s"(t) to the primary signal portion s(t).
[0083] The system of the present invention is particularly useful where the primary and / or secondary signal portion n(t) may contain one or more of a constant portion, a predictable portion, an erratic portion, a random portion, etc. The primary signal approximation s"(t) or secondary signal approximation n"(t) is derived by removing as many of the secondary signal portion...
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Abstract
The present invention involves method and apparatus for analyzing two measured signals that are modeled as containing primary and secondary portions. Coefficients relate the two signals according to a model defined in accordance with the present invention. In one embodiment, the present invention involves utilizing a transformation which evaluates a plurality of possible signal coefficients in order to find appropriate coefficients. Alternatively, the present invention involves using statistical functions or Fourier transform and windowing techniques to determine the coefficients relating to two measured signals. Use of this invention is described in particular detail with respect to blood oximetry measurements.
Description
REFERENCE TO PRIOR RELATED APPLICATION[0001] This application is a continuation of application Ser. No. 09 / 195,791, filed Nov. 17, 1998, which is a continuation of application Ser. No. 08 / 859,837, filed May 16, 1997 (now U.S. Pat. No. 6,157,850), which is a continuation of application Ser. No. 08 / 320,154, filed Oct. 7, 1994 (now U.S. Pat. No. 5,632,272 issued May 27, 1997), which is a continuation-in-part of application Ser. No. 08 / 132,812, filed Oct. 6, 1993 (now U.S. Pat. No. 5,490,505 issued Feb. 13, 1996), which is a continuation-in-part of application Ser. No. 08 / 249,690 filed May 26, 1994 (now U.S. Pat. No. 5,482,036), which is a continuation of application Ser. No. 07 / 666,060, filed Mar. 7, 1991 (now abandoned).BACKGROUND OF THE INVENTION[0002] 1. Field of the Invention[0003] The present invention relates to the field of signal processing. More specifically, the present invention relates to the processing of measured signals, containing a primary signal portion and a secondar...
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