Application to biomedical signals - Practical Biomedical Signal Analysis Using MATLAB - page 194

the signals in the 4-20 Hz band the parabolic fitting technique was used to detect ma-
ternal R-peaks. In order to determine maternal fiducial points a phase space thresh-
olding method based on Poincare maps was used. The axis in 3-D phase space were
constructed from: signal, its first and second derivative. The obtained 3-D space plot
is shown in Figure 4.42.
FIGURE 4.42: (a) Three-dimensional phase-space map and (b) ellipsoid used in
the maternal QRS-points detection. From [Karvounis et al., 2009].
The thresholding method used for identification of QRS complex was based on
observation that in the 3-D plot the points in the center correspond mainly to P and
T waves and low frequency noise, while the points in the surrounding torus cor-