Signal separation by nonlinear projections: The fetal electrocardiogram
Thomas Schreiber, Daniel T. Kaplan · Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics · 1996
We apply a locally linear projection technique which has been developed for noise reduction in deterministically chaotic signals to extract the fetal component from scalar maternal electrocardiographic (ECG) recordings. Although we do not expect the maternal ECG to be deterministic chaotic, typical signals are effectively confined to a lower-dimensional manifold when embedded in delay space. The method is capable of extracting fetal heart rate even when the fetal component and the noise are of comparable amplitude. If the noise is small, more details of the fetal ECG, like $P$ and $T$ waves, can be recovered.