System and method for removing narrowband noise
First Claim
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1. A system for removing narrowband noise from a received signal comprising:
- one or more notch filters for removing the narrowband noise from the signal with the filters having notch frequencies corresponding to frequency components of the narrowband noise;
means for detecting a noise spectrum of the received signal; and
, means for updating filter coefficients of the notch filters so that the notch frequencies correspond to the detected noise spectrum.
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Abstract
A system and method for removing narrowband noise from an input signal in which notch filters having notch frequencies corresponding to the noise are dynamically adjusted in accordance with a detected noise spectrum. The method may be applied to telemetry systems for implantable medical devices such as cardiac pacemakers to result in improved noise immunity.
66 Citations
30 Claims
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1. A system for removing narrowband noise from a received signal comprising:
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one or more notch filters for removing the narrowband noise from the signal with the filters having notch frequencies corresponding to frequency components of the narrowband noise;
means for detecting a noise spectrum of the received signal; and
,means for updating filter coefficients of the notch filters so that the notch frequencies correspond to the detected noise spectrum. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method for removing narrowband noise from a received signal comprising:
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filtering the received signal with one or more notch filters, the notch filters having notch frequencies corresponding to frequency components of the narrowband noise;
detecting a noise spectrum of the received signal and, updating filter coefficients of the notch filters so that the notch frequencies correspond to the detected noise spectrum of the received signal. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. A system for receiving data in the form of transmit pulses from an implantable medical device, comprising:
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an antenna for receiving a transmitted signal from an implantable device;
an analog-to-digital converter for digitizing the received signal into input signal samples;
one or more notch filters for removing narrowband noise from the received signal with the filters having notch frequencies corresponding to frequency components of the narrowband noise;
means for detecting a noise spectrum of the received signal; and
,means for updating filter coefficients of the notch filters so that the notch frequencies correspond to the detected noise spectrum. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30)
a matched filter with filter coefficients corresponding to a transmit pulse; and
,a pulse detector for detecting transmit pulses within the input signal samples by comparing output values of the matched filter with a pulse threshold value wherein the pulse threshold value is adjusted in accordance with measured peak values of noise and the transmitted signal.
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27. The system of claim 26 wherein noise peak values are measured at a time when the implantable device is known not to be transmitting in accordance with a telemetry protocol.
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28. The system of claim 27 wherein the pulse threshold value is computed as a fraction of a weighted moving average of measured signal peak values that exceed a specified minimum pulse threshold value.
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29. The system of claim 28 wherein the minimum pulse threshold value is adjusted in accordance with measured noise peak values.
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30. The system of claim 29 wherein the minimum pulse threshold is adjusted by comparing a current minimum pulse threshold value with a measured noise peak value, setting the minimum pulse threshold value equal to the measured noise peak value if the measured noise peak value is greater than the current minimum pulse threshold value, and setting the minimum pulse threshold value equal to a weighted moving average of measured noise peak values if the measured noise peak value is less than the current minimum pulse threshold value.
Specification