System and method for cancellation of signal artifacts

• US 5,107,849 A
• Filed: 09/12/1990
• Issued: 04/28/1992
• Est. Priority Date: 09/12/1990
• Status: Expired due to Fees

• Current Assignee: Howard T. Bellin, Robert P. Dingwall
• Original Assignee: Cortec Corporation
• Inventors: Bellin, Howard T., Dingwall, Robert P.
• Primary Examiner(s): Kamm, William E.
• Application Number:
  US07/581,638
• Time in Patent Office: 594 Days
• Field of Search: 128/696, 128/702
• US Class Current: 600/508
• CPC Class Codes: A61B 5/30 Input circuits therefor
• CPC Class Codes: A61B 5/301 providing electrical separation, e.g. by using isolating transformers or optocouplers
• CPC Class Codes: A61B 5/308 for electrocardiography [ECG]

Abstract

A system for processing a repeating complex waveform that removes or reduces a significant portion of artifacts and other noise from the desired source signal. The system employs a phase detector for isolating artifacts from the source which are then used in processing the ECG waveform. The method and apparatus is especially useful in processing ECG signals reflective of heart conditions. The resulting clean signal makes accurate diagnosis of pending patient condition faster and more reliable.

Claims

1. In a system for removing artifacts from a repeating complex waveform comprising a signal input and divider means for receiving an electrical signal containing said complex waveform and dividing said input signal into plural signal paths;

signal delay means for time delaying said signal of at least one of said plural signal paths by an amount substantially equal to a period of one or a whole multiple of said complex waveform;

artifact isolation means for isolating an artifact containing component signals from said delayed signal path and a second path, wherein said component signal of second signal path is time displaced from said signal of said delayed signal path;

summing means for forming a combined signal by summing said signal from said delayed signal path with said signal of at least said second signal path;

artifact removal means for subtracting said isolated artifact containing component from said combined signal thereby forming an essentially artifact-free signal; and

output means for transmitting said artifact-free signal to an output device.

2. The system of claim 1 wherein said signal delay means is an analog delay circuit connected with a voltage controlled oscillator for phase feedback control.

3. The system of claim 2 wherein said voltage control oscillator received phasing signal input from a phase detector means of said delayed and second signals.

4. The system of claim 3 wherein said phase detector means comprising a low pass filter means and produces a phase controlling output when said delayed and second signals fall out of phase.

5. The system of claim 1 wherein said artifact isolation means comprises a high pass filter means between a phase detector means and a math amp negative terminal.

6. The system of claim 1 further comprising output means for display of artifact-free complex waveforms as received from said artifact removal means.

7. A method for removing artifacts from an electrocardiogram (ECG) comprising the steps of:

receiving and dividing an ECG input signal of at least one heartbeat into at least two signal paths;

delaying at least one of said signal paths by an amount substantially equal to the period of the ECG associated with one heartbeat;

isolating said artifacts from said delayed signal path and a second signal path time displaced from said delayed signal path;

combining said signal paths from which said artifacts have been isolated;

subtracting from said combined signal paths said isolated artifacts; and

outputting a signal representative of said ECG but essentially free from artifacts.

8. The method of claim 7 wherein said delaying step comprises maintaining phase between the delayed signal path and second signal path.

9. The method of claim 8 further comprising the step of outputting a delayed or stored signal representative of a frequency of the heartbeat.

10. In combination in an apparatus for the processing of an ECG signal comprising means for receiving a signal representative of a patient'"'"'s ECG;

means for storing a portion of said received signal representative of one heartbeat;

means for receiving and inputting a real time ECG signal;

means for isolating artifacts from a real time ECG signal and from said stored ECG signal;

means for maintaining phase between said real time ECG signal and said stored ECG signal;

summing means for combining said real time ECG signal and said stored ECG signal;

subtraction means for removing said isolated artifacts from said combined signals; and

output means for outputting an ECG signal essentially free of artifacts.

11. In the apparatus of claim 10 wherein the phase maintenance means includes a frequency detection means for determining a heart rate from said real time ECG signal.

12. In the apparatus of claim 11 wherein said phase maintenance means which includes a phase detector means, a low pass filter means and a voltage controlled oscillator is further connected to and controlling the output of said storing means.