Method and apparatus for removing baseline wander from an ECG signal
First Claim
1. An improved ECG monitor comprising:
- a plurality of electrodes to be affixed to a patient'"'"'s body to pick up ECG signals in an ECG signal band, the electrodes electrically coupled to a plurality of input amplifiers;
at least one analog to digital converter (“
ADC”
), the ADC electrically coupled to the input amplifiers to digitize the ECG signals;
a digital baseline wander filter electrically coupled to the at least one ADC to receive the digitized ECG signals, the baseline wander filter having an internal finite impulse response (“
FIR”
) low pass filter characterized by a substantially trapezoidal impulse response, the baseline wander filter to substantially remove a baseline wander signal component having a range of frequency components below the ECG signal band; and
an ECG waveform output signal, the ECG waveform output signal being a baseline filtered ECG waveform representing the one or more of the ECG signals, wherein the ECG waveform output signal from the improved ECG monitor is delayed less than 2 seconds from the ECG signals.
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Abstract
According to one aspect of the invention, an improved ECG monitor includes a plurality of electrodes to be affixed to a patient'"'"'s body to pick up ECG signals in an ECG signal band. The electrodes are electrically coupled to a plurality of input amplifiers. At least one analog to digital converter (“ADC”) is electrically coupled to the input amplifiers to digitize the ECG signals. A digital baseline wander filter has an internal finite impulse response (“FIR”) low pass filter characterized by a substantially trapezoidal impulse response. The baseline wander filter substantially removes a baseline wander signal component having a range of frequency components below the ECG signal band. The ECG waveform output signal is a baseline filtered ECG waveform representing the one or more of the ECG signals. The ECG waveform output signal from the improved ECG monitor is delayed less than 2 seconds from the ECG signals.
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Citations
24 Claims
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1. An improved ECG monitor comprising:
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a plurality of electrodes to be affixed to a patient'"'"'s body to pick up ECG signals in an ECG signal band, the electrodes electrically coupled to a plurality of input amplifiers;
at least one analog to digital converter (“
ADC”
), the ADC electrically coupled to the input amplifiers to digitize the ECG signals;
a digital baseline wander filter electrically coupled to the at least one ADC to receive the digitized ECG signals, the baseline wander filter having an internal finite impulse response (“
FIR”
) low pass filter characterized by a substantially trapezoidal impulse response, the baseline wander filter to substantially remove a baseline wander signal component having a range of frequency components below the ECG signal band; and
an ECG waveform output signal, the ECG waveform output signal being a baseline filtered ECG waveform representing the one or more of the ECG signals, wherein the ECG waveform output signal from the improved ECG monitor is delayed less than 2 seconds from the ECG signals. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method to design an ECG baseline wander filter having near optimum minimal delay while meeting industry requirements for ECG monitors comprising the steps of:
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providing a set of relevant parameters from an ECG monitor performance specification;
converting the relevant parameters to impulse response constraints on a set of discrete signal equations for a finite impulse response filter;
providing a transfer function for a filter architecture; and
reducing the impulse response constraints to a final set of equations for the filter architecture, to determine the parameters defining a finite impulse response of the ECG baseline wander filter. - View Dependent Claims (16, 17, 18, 19, 20)
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21. An improved digital baseline wander (restoration) filter comprising:
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a low pass filter to high pass filter digital architecture having a first signal path and a second signal path, the first signal path comprising a gain and delay element (all pass filter) and the second signal path comprising a cascade of two or more FIR low pass filters wherein the improvement is to the impulse response of the low pass filter in the form of a finite impulse response (“
FIR”
) that is substantially trapezoidal in shape; and
a digital input signal coupled to the first and second signal paths, the digital input signal having a signal band of interest of frequencies above a frequency fc and a baseline wander including frequencies below fc, the baseline wander filter to substantially remove a baseline wander signal component having a frequency components below fc and to pass the signal band of frequencies above fc to generate a baseline wander filtered output signal having only a signal band of frequencies substantially above fc. - View Dependent Claims (22, 23, 24)
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Specification