Device for eliminating ringing in filtered ECG signals
First Claim
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.
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Abstract
A device for eliminating ringing in filtered ECG signals includes an analog-to-digital for converting the ECG input signals into a series of digital values, and a filter unit connected to the output of the analog-to digital converter. The filter unit includes a recursive IIR-filter and a subsequent allpass filter with a phase shift which is equal to twice the phase shift of the IIR filter. The allpass filtering is performed time-reversed with respect to the IIR filtering. In a method for producing an allpass filter, for use in the above device, having a phase shift which is equal to twice the phase shift of an IIR filter, the IIR filter having zero points situated on the unity circle in the Z-plane, the zero points of the IIR filter are replaced by new zero points obtained by reflecting the poles of the filter in the unity circle in the Z-plane.
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Citations
5 Claims
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1. A device for eliminating filter-produced ringing in filtered ECG signals comprising:
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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. - View Dependent Claims (3, 4)
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2. A device for eliminating filter-produced ringing in filtered EGG signals comprising:
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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.
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5. A method for producing an allpass filter having a phase shift which is equal to twice the phase shift of an IIR filter having poles and having zero points situated on a unity circle in the Z-plane, comprising the steps of:
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reflecting the poles of the IIR filter in the unity circle in the Z-plane to obtain new zero points; and replacing the zero points of said IIR filter with said new zero points.
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Specification