Real-time back-projection of fetal ECG sources in OL-JADE for the optimization of blind electrodes positioning

Fetal ECG (FECG) extraction from non-invasive biopotential recordings is strongly affected by the intensity of the FECG contribution to the input signals. The higher the FECG contribution the higher the SNR and consequently the quality of the separation. The definition of a subject-specific good electrodes positioning is an open issue. In this paper we present a technique based on the fetal ECG extraction algorithm OL-JADE, which tries to invert the whole blind extraction process only for the FECG estimated sources in order to estimate the FECG power at the electrodes. Due to the recursive sample-by-sample nature of the whitening stage of OL-JADE, an approximated Least Squares solution has been introduced in the back-projection scheme revealing adequate performance. An optimized version of the proposed method has been integrated with OL-JADE on a floating point DSP, guaranteeing the respect of the real-time bound.