document: Matched-filter template generation via spatial filtering : application to fetal biomagnetic recordings We have developed a two-step procedure for signal processing of fetal biomagnetic recordings that removes cardiac interference and noise . First , a modified matched filter -LRB- MF -RRB- is applied to remove maternal cardiac interference ; then , a simple signal space projection -LRB- SSP -RRB- is applied to remove noise . The key difference between our MF and a conventional one is that the interference template and the template scaling are derived from a signal that has been spatially filtered to isolate the interference , rather than from the raw signal . Unlike conventional MFs , ours is able to separate maternal and fetal cardiac complexes , even when they have similar morphology and overlap strongly . When followed by a SSP that preserves only the signal subspace , the noise is reduced to a low level
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