Signal processing apparatus and method
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Accused Products
Abstract
A method and an apparatus to analyze two measured signals that are modeled as containing desired and undesired portions such as noise, FM and AM modulation. Coefficients relate the two signals according to a model defined in accordance with the present invention. In one embodiment, a transformation is used to evaluate a ratio of the two measured signals in order to find appropriate coefficients. The measured signals are then fed into a signal scrubber which uses the coefficients to remove the unwanted portions. The signal scrubbing is performed in either the time domain or in the frequency domain. The method and apparatus are particularly advantageous to blood oximetry and pulserate measurements. In another embodiment, an estimate of the pulserate is obtained by applying a set of rules to a spectral transform of the scrubbed signal. In another embodiment, an estimate of the pulserate is obtained by transforming the scrubbed signal from a first spectral domain into a second spectral domain. The pulserate is found by identifying the largest spectral peak in the second spectral domain.
37 Citations
37 Claims
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1-30. -30. (canceled)
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31. In a signal processor for processing at least two measured signals M1 and M2, where said signal M1 comprises a combination of a signal portion S1 and a signal portion N1, and where said signal M2 comprises a combination of a signal portion S2 and a signal portion N2, where S1 is approximately proportional to S2 and where N1 is approximately proportional to N2, a method comprising:
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determining a value for a coefficient c, such that an error value e, given by the relation e=S1−
(cM1−
M2) is at least partially reduced; and
using said coefficient c to remove at least some of the signal portion N1 from the measured signal M1 and thereby producing an approximation A1 to said signal S1, where A1=cM1−
M2. - View Dependent Claims (32, 33, 34, 35, 36, 37)
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Specification