US5269313A
Expired / Lapsed
US
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Filter and method for filtering baseline wander
Assignee: Sherwood Medical Co
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Filing: 1991-09-09
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Granted: 1993-12-14
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Expires: 2011-09-09
Abstract
Abstract A linear phase high pass filter having a linear phase low pass filter in parallel with an electronic delay means is disclosed to remove baseline wander from an ECG signal. The linear phase low pass filter is preferably a digital Infinite Impulse Response (IIR) filter. An input ECG signal is simultaneously presented to an IIR low pass filter and an electronic delay. The low pass filter passes the low frequency baseline signal while blocking the ECG signal comprised of higher frequency components than the cutoff frequency of the low pass filter. Thereafter, the outputs from the IIR low pass filter and delay are passed to a summer that subtracts the output of the low pass filter from the output of the delay to produce the output of the filter. The combination of the output of a low pass filter being subtracted from a delayed input signal produces a high pass filter. The resulting high pass filter has a -0.3 dB cutoff frequency of about 0.5 Hertz while providing a virtually constant group delay for the ECG signal passed through the filter.
Inventors
- 👤 Victor M. DePinto
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 11:15
CPC Classifications
A; A61; A61B; A61B5/00; A61B5/24; A61B5/30; A61B5/307; A61B5/308; H; H03; H03H; H03H17/00; H03H17/02
Claims Analysis
Total Claims: 24
Claim 1
Independent Claim
195 words
A device for removing low frequency signals, including baseline wander signals from an ECG signal comprising: a) an ECG input; b) means, connected to said ECG input, for attenuating the frequency components of an ECG signal above a preselected cutoff frequency and for passing the frequency components of an ECG signal below said preselected cutoff frequency through said means for attenuating and passing when an ECG signal is presented to said ECG input, said means for attenuating and passing having a linear phase response for those frequency components of an ECG signal passed through said means for attenuating and passing; c) means, connected to said ECG input, for delaying the ECG signal presented to said ECG input for a time approximately equal to the time said means for attenuating and passing requires to pass the frequency components of an ECG signal below said preselected cutoff frequency through said means for attenuating and passing; and d) means, connected to the output of said means for delaying and to the output of said means for attenuating and passing, for subtracting the output of said means for attenuating and passing from the output of said means for delaying.
Claim 2
Independent Claim
195 words
A device for removing low frequency signals, including baseline wander signals from an ECG signal comprising: a) an ECG input; b) means, connected to said ECG input, for attenuating the frequency components of an ECG signal above a preselected cutoff frequency and for passing the frequency components of an ECG signal below said preselected cutoff frequency through said means for attenuating and passing when an ECG signal is presented to said ECG input, said means for attenuating and passing having a linear phase response for those frequency components of an ECG signal passed through said means for attenuating and passing; c) means, connected to said ECG input, for delaying the ECG signal presented to said ECG input for a time approximately equal to the time said means for attenuating and passing requires to pass the frequency components of an ECG signal below said preselected cutoff frequency through said means for attenuating and passing; and d) means, connected to the output of said means for delaying and to the output of said means for attenuating and passing, for subtracting the output of said means for attenuating and passing from the output of said means for delaying.
Claim 3
Dependent Claim
19 words
The device of claim 1 wherein said means for attenuating and passing comprises a linear phase low pass filter.
Claim 4
Dependent Claim
14 words
The device of claim 2 wherein said low pass filter is a digital filter.
Claim 5
Dependent Claim
16 words
The device of claim 3 wherein said low pass filter is an infinite impulse response filter.
Claim 6
Dependent Claim
16 words
The filter of claim 4 wherein said infinite impulse response filter comprises a plurality of filters.
Claim 7
Dependent Claim
18 words
The device of claim 5 wherein the plurality of filters of said infinite impulse response filter is three.
Claim 8
Dependent Claim
16 words
The device of claim 6 wherein said infinite impulse response filter is a fifth order filter.
Claim 9
Dependent Claim
28 words
The device of claim 5 wherein each of said plurality of filters is selected from the group consisting of a first order filter and a second order filter.
Claim 10
Dependent Claim
12 words
The device of claim 8 wherein the plurality of filters is three.
Claim 11
Dependent Claim
15 words
The device of claim 9 wherein said three filters together are a fifth order filter.
Claim 12
Dependent Claim
15 words
The device of claim 10 wherein said electronic memory means are digital electronic memory means.
Claim 13
Dependent Claim
15 words
The filter of claim 4 wherein said low pass filter is a variable gain filter.
Claim 14
Dependent Claim
14 words
The device of claim 1 wherein said means for delaying includes electronic memory means.
Claim 15
Dependent Claim
13 words
The device of claim 1 wherein said means for subtracting includes a summer.
Claim 16
Independent Claim
223 words
A device for removing low frequency signals, including baseline wander signals from an ECG signal comprising: a) an ECG input; b) means, connected to said ECG input, for attenuating the frequency components of an ECG signal above a preselected cutoff frequency and for passing the frequency components of an ECG signal below said preselected cutoff frequency through said means for attenuating and passing when an ECG signal is presented to said ECG input, said means for attenuating and passing having a linear phase response for those frequency components of an ECG signal passed through said means for attenuating and passing, said means for attenuating and passing comprising a linear phase low pass filter; c) means, connected to said ECG input, for delaying the ECG signal presented to said ECG input for a time approximately equal to the time said means for attenuating and passing requires to pass the frequency components of an ECG signal below said preselected cutoff frequency through said means for attenuating and passing, said means for delaying including electronic memory means; and d) means, connected to the output of said means for delaying and to the output of said means for attenuating and passing, for subtracting the output of said means for attenuating and passing from the output of said means for delaying, said means for subtracting including a summer.
Claim 17
Independent Claim
223 words
A device for removing low frequency signals, including baseline wander signals from an ECG signal comprising: a) an ECG input; b) means, connected to said ECG input, for attenuating the frequency components of an ECG signal above a preselected cutoff frequency and for passing the frequency components of an ECG signal below said preselected cutoff frequency through said means for attenuating and passing when an ECG signal is presented to said ECG input, said means for attenuating and passing having a linear phase response for those frequency components of an ECG signal passed through said means for attenuating and passing, said means for attenuating and passing comprising a linear phase low pass filter; c) means, connected to said ECG input, for delaying the ECG signal presented to said ECG input for a time approximately equal to the time said means for attenuating and passing requires to pass the frequency components of an ECG signal below said preselected cutoff frequency through said means for attenuating and passing, said means for delaying including electronic memory means; and d) means, connected to the output of said means for delaying and to the output of said means for attenuating and passing, for subtracting the output of said means for attenuating and passing from the output of said means for delaying, said means for subtracting including a summer.
Claim 18
Independent Claim
228 words
A device for removing low frequency signals, including baseline wander signals from an ECG signal comprising: a) an ECG input; b) means, connected to said ECG input, for attenuating the frequency components of an ECG signal above a preselected cutoff frequency and for passing the frequency components of an ECG signal below said preselected cutoff frequency through said means for attenuating and passing when an ECG signal is presented to said ECG input, said means for attenuating and passing having a linear phase response for those frequency components of an ECG signal passed through said means for attenuating and passing, said means for attenuating and passing comprising a digital infinite impulse response linear phase low pass filter; c) means, connected to said ECG input, for delaying the ECG signal presented to said ECG input for a time approximately equal to the time said means for attenuating and passing requires to pass the frequency components of an ECG signal below said preselected cutoff frequency through said means for attenuating and passing, said means for delaying including digital electronic memory means; and d) means, connected to the output of said means for delaying and to the output of said means for attenuating and passing, for subtracting the output of said means for attenuating and passing from the output of said means for delaying, said means for subtracting including a summer.
Claim 19
Independent Claim
228 words
A device for removing low frequency signals, including baseline wander signals from an ECG signal comprising: a) an ECG input; b) means, connected to said ECG input, for attenuating the frequency components of an ECG signal above a preselected cutoff frequency and for passing the frequency components of an ECG signal below said preselected cutoff frequency through said means for attenuating and passing when an ECG signal is presented to said ECG input, said means for attenuating and passing having a linear phase response for those frequency components of an ECG signal passed through said means for attenuating and passing, said means for attenuating and passing comprising a digital infinite impulse response linear phase low pass filter; c) means, connected to said ECG input, for delaying the ECG signal presented to said ECG input for a time approximately equal to the time said means for attenuating and passing requires to pass the frequency components of an ECG signal below said preselected cutoff frequency through said means for attenuating and passing, said means for delaying including digital electronic memory means; and d) means, connected to the output of said means for delaying and to the output of said means for attenuating and passing, for subtracting the output of said means for attenuating and passing from the output of said means for delaying, said means for subtracting including a summer.
Claim 20
Dependent Claim
16 words
The filter of claim 16 wherein said infinite impulse response filter comprises a plurality of filters.
Claim 21
Dependent Claim
21 words
The device of claim 17 wherein said digital infinite impulse response linear phase low pass filter is a fifth order filter.
Claim 22
Dependent Claim
21 words
The device of claim 17 wherein said digital infinite impulse response linear phase low pass filter is a third order filter.
Claim 23
Independent Claim
110 words
A method for removing low frequency signals, including baseline wander signals from an ECG signal comprising the steps of: a) simultaneously presenting an ECG signal to a linear phase low pass filter and a delay means; b) attenuating the frequency components of the ECG signal above a predetermined cutoff frequency presented to said low pass filter; c) delaying the ECG signal presented to said delay means for a time approximately equal to the time required by said low pass filter to pass the ECG signal through said low pass filter; and d) subtracting the ECG signal passed through said low pass filter from the signal delayed by said delay means.
Claim 24
Independent Claim
110 words
A method for removing low frequency signals, including baseline wander signals from an ECG signal comprising the steps of: a) simultaneously presenting an ECG signal to a linear phase low pass filter and a delay means; b) attenuating the frequency components of the ECG signal above a predetermined cutoff frequency presented to said low pass filter; c) delaying the ECG signal presented to said delay means for a time approximately equal to the time required by said low pass filter to pass the ECG signal through said low pass filter; and d) subtracting the ECG signal passed through said low pass filter from the signal delayed by said delay means.
References Cited (Backward Citations)
DE210148C
Cited
US3569852A
Cited
US3822696A
Cited
US3923041A
Cited
US4170227A
Cited
US4192318A
Cited
US4563704A
Cited
US4492235A
Cited
US4458692A
Cited
US4458691A
Cited
US4537201A
Cited
US4812976A
Cited
US4664116A
Cited
US4658831A
Cited
US4931743A
Cited
US4802491A
Cited
US4793361A
Cited
US4908579A
Cited
JPH01227740A
Cited
US4914398A
Cited
US5025794A
Cited
US4947858A
Cited
US5107849A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1996-12-13 | 1997-06-14 | 1997-12-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2000-12-13 | 2001-06-14 | 2001-12-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2004-12-13 | 2005-06-14 | 2005-12-14 | $7700.00 | Window Closed / Lapsed |