Recovering one irregular signal in the presence of another stronger one--_in utero_ pulse ox

[Phil Hobbs]

(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

[Phil Hobbs]

Post by Phil Hobbs
(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.)

Crap. Sorry!

Cheers

Phil Hobbs

[boB]

On Sun, 6 Jun 2021 14:45:11 -0400, Phil Hobbs

Post by Phil Hobbs

Post by Phil Hobbs
(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.)

Crap. Sorry!
Cheers
Phil Hobbs

Sorry about what ?

It's an interesting project but my digital PLL skills are a bit
lacking. At least in software which is where I would like to be
better at.

I do know about acquiring ECGs but only using diff amps.

Might be a good question for the "dsprelated" forum along with
embeddedrelated and all that stuff.

boB

[Phil Hobbs]

Post by boB
On Sun, 6 Jun 2021 14:45:11 -0400, Phil Hobbs

Post by Phil Hobbs

Post by Phil Hobbs
(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.)

Crap. Sorry!

Sorry about what ?

Posting the same thing here twice, when I intended the second one to go
to sci.electronics.design.

Post by boB
It's an interesting project but my digital PLL skills are a bit
lacking. At least in software which is where I would like to be
better at.
I do know about acquiring ECGs but only using diff amps.
Might be a good question for the "dsprelated" forum along with
embeddedrelated and all that stuff.

Thanks. I pretty well keep to Usenet.

Cheers

Phil Hobbs