Device for eliminating ringing in filtered ECG signals

DETAILED DESCRIPTION We claim as our invention: 1.
A device for eliminating filter-produced ringing in filtered ECG signals comprising: an analog-to-digital converter to which analog ECG signals are supplied, said converter converting said analog ECG signals into a series of digital values; a recursive IIR filter to which said digital values are supplied, said recursive IIR filter filtering said digital values and generating an output signal exhibiting a phase shift and simultaneously introducing ringing into said output signal; and an allpass filter supplied with said output signal of said recursive IIR filter, said allpass filter filtering at least a portion of said output signal from said IR filter time-reversed in comparison to said IIR filter and with a phase shift equal to twice the phase shift exhibited by the output signal from the IIR filter to eliminate said ringing.
2.
A device for eliminating filter-produced ringing in filtered EGG signals comprising: an analog-to-digital converter to which analog EGG signals are supplied, said ECG signals each containing a QRS complex; an averager supplied with said digital values, said averager forming a signal average over a number of said QRS complexes; a recursive IIR filter to which said signal average is supplied, said recursive IIR filter filtering said signal average and generating an output signal exhibiting a phase shift and simultaneously introducing ringing into said output signal; and an allpass filter supplied with said output signal of said recursive IIR filter, said allpass filter filtering at least a portion of said output signal from said IIR filter time-reversed in comparison to said IIR filter and with a phase shift equal to twice the phase shift exhibited by the output signal from the IIR filter to eliminate said ringing.
3.
A device as claimed in claim 1 wherein each of said ECG signals contains a QRS complex, and wherein said allpass filter comprises means for only filtering a latter part of each QRS complex.
4.
A device as claimed in claim 1 wherein said ECG signals each contain a QRS complex, and wherein said allpass filter comprises means for only filtering an earlier part of each QRS complex