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 signal responsive to said first input signal passing through a portion of said subject having blood therein, a second signal responsive to said second input signal passing through said portion of said subject, and a third 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 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, to obtain the second calibration data, said first signal source, said second signal source, and said third signal source are operated in pairs such that for a time interval each of pairs of signal sources are operated alternatingly one at a time.
2. 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 signal responsive to said first input signal passing through a portion of said subject having blood therein and which detects a second signal responsive to said second input signal passing through said portion of said subject, and a third signal responsive to said third input signal, said detector generating a detector output signal responsive to said first, second, and third signals; and
a signal processor which receives said detector output signal, said signal processor demodulating said detector output signal by applying a demodulation signal determined at least in part from a first dataset wherein each of said first, second, and third sources are activated one at a time and a second dataset wherein each of said first, second, and third sources are deactivated one at a time.
3. The apparatus of claim 2 , wherein at least a portion of said first dataset comprises turning off only one of said first, second, or third signal sources and measuring between one of parametric signals and non-corresponding output signals.
4. The apparatus of claim 2 , further comprising a fourth signal source and wherein at least a portion of said first dataset comprises a set of unique activation patterns wherein a plurality of said sources are active and a plurality of said sources are not active in each pattern.
5. The apparatus of claim 2 , further comprising a fourth signal source and a fifth signal source and wherein at least a portion of said first dataset is obtained using a set of activation patterns wherein a plurality of said sources are active and a plurality of said sources are not active in each pattern and where each activation pattern is different.