Method and apparatus for calibration to reduce coupling between signals in a measurement system
A method and an apparatus for separating a composite signal into a plurality of signals is described. A signal processor receives a composite signal and separates a composite signal into separate output signals. Feedback from one or more of the output signals is provided to a configuration module that configures the signal processor to improve a quality of the output signals. In one embodiment, calibration data from multiple calibration data sets is used to configure the demodulation of the composite signal into separate output signals.
1. An apparatus for measuring one or more blood constituents in a subject, said apparatus comprising:
a first signal source which applies a first input signal during a first time interval;
a second signal source which applies a second input signal during a second time interval;
a third signal source which applies a third input signal during a third time interval;
a detector which detects a first parametric signal responsive to said first input signal passing through a portion of said subject having blood therein, a second parametric signal responsive to said second input signal passing through said portion of said subject, and a third parametric signal responsive to said third input signal passing through a portion of said subject having blood therein, said detector generating a detector output signal responsive to said first, second, and third parametric signals; and
a signal processor which receives said detector output signal, said signal processor configured to demodulate said detector output signal by applying a first demodulation signal to a signal responsive to said detector output signal to generate a first demodulator output signal, applying a second demodulation signal to said signal responsive to said detector output signal to generate a second demodulator output signal, and applying a third demodulation signal to said signal responsive to said detector output signal to generate a third demodulator output signal, said signal processor configured to select said first demodulation signal, said second demodulation signal and said third demodulation signal to reduce crosstalk between said first, second, and third demodulator signals using, at least in part, first and second calibration data, wherein said first calibration data comprises calibration data wherein said first signal source, said second signal source, and said third signal source are operated singly during a normal operation period, and wherein said second calibration data comprises calibration data wherein said first signal source, said second signal source, and said third signal source are not operated.
2. An apparatus for measuring one or more parameters in a subject, said apparatus comprising:
four or more sources;
at least one detector configured to sense electromagnetic radiation produced by said four or more sources, an output of said at least one detector comprising a detector signal; and
a signal processor which receives said detector output signal, said signal processor configured to demodulate said detector output signal by applying a first demodulation signal to a signal responsive to said detector output signal to generate a first demodulator output signal, applying a second demodulation signal to said signal responsive to said detector output signal to generate a second demodulator output signal, and applying a third demodulation signal to said signal responsive to said detector output signal to generate a third demodulator output signal, said signal processor configured to select said first demodulation signal, said second demodulation signal and said third demodulation signal to reduce crosstalk between said first, second, and third demodulator signals using, at least in part, calibration data, wherein said calibration data is obtained, at least in part, by activating said four or more sources according to a set of activation patterns, wherein the number of activation patterns is greater than the number of sources in said four or more sources.
3. The apparatus of claim 2 , wherein said activation patterns comprise a first set of patterns wherein each of said four or more sources is activated singly, and a second set of patterns wherein each of said four or more sources is deactivated singly.
4. The apparatus of claim 2 , wherein said activation patterns comprise patterns wherein each of said four or more sources is activated one at a time.
5. The apparatus of claim 2 , wherein said activation patterns comprise patterns wherein each of said four or more sources is de-activated one at a time.