Patent ID: 7474915

Claim:
A method of estimating a fetal electrocardiogram signal comprising the steps of: measuring an abdominal electrocardiogram signal from the abdomen of a pregnant female; measuring a thoracic electrocardiogram signal from the thorax of said pregnant female; transforming the thoracic electrocardiogram signal using a polynomial network to provide a transformed thoracic electrocardiogram signal such that the difference between the transformed thoracic electrocardiogram signal and the abdominal electrocardiogram signal is minimised; and subtracting the transformed thoracic electrocardiogram signal from the abdominal electrocardiogram signal to provide an estimated fetal electrocardiogram signal, wherein the transforming step comprises the sub-steps of: partitioning the thoracic electrocardiogram signal into a plurality of frames comprising a plurality of signal samples; generating a time derivative vector sequence comprising a frame of the thoracic electrocardiogram signal and one or more time derivatives of said frame; generating a polynomial matrix for said frame said matrix comprising a vector sequence of polynomial basis terms in dependence upon said time derivative vector sequence; partitioning the abdominal electrocardiogram signal into a plurality of frames each frame corresponding in time with a frame of the thoracic electrocardiogram signal; generating a mapping vector in dependence upon said polynomial matrix for said frame and upon a corresponding frame of the abdominal electrocardiogram signal; and generating the transformed thoracic electrocardiogram signal in dependence upon said mapping vector and said polynomial matrix.