(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
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