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  • Recovering one irregular signal in the presence of another stronger one

    From Phil Hobbs@21:1/5 to All on Tue May 18 18:31:28 2021
    Hi, all,

    Hoping there are still some DSP folks round here despite the evil Google
    ban. (But I repeat myself.)

    I'm working on a completely noninvasive sensor for fetal blood oxygen,
    using optical sensing through the mom's abdomen. It's a very low SNR measurement on account of all the attenuation.

    The mom's heartbeat modulates her pulse-ox signal, which is much
    stronger than the fetus's on account of the scattering and absorption in maternal tissue.

    The data are several time series. The main issue is the variability of
    both pulses, which smear out the spectra and therefore knock the peak
    heights way down towards the noise. There are weak multiplicative
    effects between maternal and fetal signals, as you'd expect.

    What I'm looking to do is something like:

    1. Use a digital PLL to find the time-dependent maternal pulse rate.

    2. Resample the data accordingly, and notch out the first 5 or so mom harmonics.

    3. Do the PLL thing on the fetal pulse, and signal average to pull out
    the average fetal pulse ox signal.

    Extra credit: sometimes the baby's pulse can cross the first or second
    harmonic of the mom's, and it would be good to preserve both pulse
    shapes accurately.

    Resampling a noisy signal isn't necessarily the most well-conditioned operation, so I'd welcome suggestions for just how to do this.

    Thanks

    Phil Hobbs

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Phil Hobbs@21:1/5 to All on Sun Jun 6 14:38:03 2021
    (I posted this in comp.dsp a couple of weeks ago, but most of the actual
    DSP people seem to have disappeared, so the discussion petered out
    fairly fast. Trying again here.)

    Hi, all,

    Hoping there are still some DSP folks round here despite the evil Google
    ban. (But I repeat myself.)

    I'm working on a completely noninvasive sensor for fetal blood oxygen,
    using optical sensing through the mom's abdomen. It's a very low SNR measurement on account of all the attenuation.

    The mom's heartbeat modulates her pulse-ox signal, which is much
    stronger than the fetus's on account of the scattering and absorption in maternal tissue.

    The data are several time series. The main issue is the variability of
    both pulses, which smear out the spectra and therefore knock the peak
    heights way down towards the noise. There are weak multiplicative
    effects between maternal and fetal signals, as you'd expect.

    What I'm looking to do is something like:

    1. Use a digital PLL to find the time-dependent maternal pulse rate.

    2. Resample the data accordingly, and notch out the first 5 or so mom harmonics.

    3. Do the PLL thing on the fetal pulse, and signal average to pull out
    the average fetal pulse ox signal.

    Extra credit: sometimes the baby's pulse can cross the first or second
    harmonic of the mom's, and it would be good to preserve both pulse
    shapes accurately.

    Resampling a noisy signal isn't necessarily the most well-conditioned operation, so I'd welcome suggestions for just how to do this.

    Thanks

    Phil Hobbs

    --
    Dr Philip C D Hobbs
    Principal Consultant
    ElectroOptical Innovations LLC / Hobbs ElectroOptics
    Optics, Electro-optics, Photonics, Analog Electronics
    Briarcliff Manor NY 10510

    http://electrooptical.net
    http://hobbs-eo.com

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)