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US5584295A
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System for measuring the period of a quasi-periodic signal
Assignee: Analogic Corp
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Filing: 1995-09-01
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Granted: 1996-12-17
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Expires: 2015-09-01
Abstract
Abstract The disclosed system for measuring the periodic content of an input signal includes an autocorrelation function generator for generating a sequence of autocorrelation functions. Each of the autocorrelation functions is representative of an autocorrelation function of a portion of the input signal. The system further includes a temporal filter for filtering the autocorrelation functions and thereby generating a lag histogram. In other forms the system may comprise a fetal heart rate monitor for measuring the heart rate of a fetus in vivo. The monitor generates a lag histogram and uses the lag histogram for stabilizing the determination of the fetal heart rate.
Inventors
- 👤 Jeremy L. Muller
- 👤 Robert G. Hohlfeld
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 08:03
CPC Classifications
A; A61; A61B; A61B8/00; A61B8/08; A61B8/0866; A61B8/02; G; G01; G01R; G01R23/00; G01R23/16; G01R23/165; G01S; G01S15/00; G01S15/02; G01S15/50; G01S15/58
Claims Analysis
Total Claims: 29
Claim 1
Independent Claim
64 words
A system for measuring the periodic content of an input signal, comprising: (A) autocorrelation means, responsive to the input signal, for generating a sequence of autocorrelation functions, each of the autocorrelation functions in the sequence being representative of an autocorrelation function of a portion of the input signal; and (B) temporal filter means for temporally filtering the autocorrelation functions to generate a lag histogram.
Claim 2
Independent Claim
64 words
A system for measuring the periodic content of an input signal, comprising: (A) autocorrelation means, responsive to the input signal, for generating a sequence of autocorrelation functions, each of the autocorrelation functions in the sequence being representative of an autocorrelation function of a portion of the input signal; and (B) temporal filter means for temporally filtering the autocorrelation functions to generate a lag histogram.
Claim 3
Dependent Claim
16 words
A system according to claim 1, wherein the temporal filter means comprises a single pole filter.
Claim 4
Dependent Claim
19 words
A system according to claim 1, wherein the temporal filter includes means for generating a sequence of lag histograms.
Claim 5
Dependent Claim
30 words
A system according to claim 1, wherein the temporal filter means includes means for generating a scaled correlation signal by multiplying one of the autocorrelation functions by a filter coefficient.
Claim 6
Dependent Claim
30 words
A system according to claim 4, wherein the temporal filter means includes means for generating a scaled lag signal by multiplying the lag histogram by one minus the filter coefficient.
Claim 7
Dependent Claim
26 words
A system according to claim 5, wherein the temporal filter means generates the lag histogram by summing the scaled correlation signal and the scaled lag signal.
Claim 8
Dependent Claim
15 words
A system according to claim 6, further including means for adaptively varying the filter coefficient.
Claim 9
Dependent Claim
37 words
A system according to claim 6, wherein each of the autocorrelation functions is characterized by a zero lag peak, and further including means for adaptively varying the filter coefficient as a function of the zero lag peaks.
Claim 10
Dependent Claim
18 words
A system according to claim 1, further including means for locating a main peak in the lag histogram.
Claim 11
Dependent Claim
33 words
A system according to claim 9, further including means for locating a peak in one of the autocorrelation functions that is within a threshold distance of the main peak in the lag histogram.
Claim 12
Dependent Claim
102 words
A fetal heart rate monitor for measuring the heart rate of a fetus, comprising: (A) means for generating an ultrasound signal that propagates into the fetus; (B) means for receiving an ultrasound reflection signal reflected by the fetus and means for converting the ultrasound reflection signal to an electrical signal; (C) autocorrelation means, responsive to the electric signal, for generating a sequence of autocorrelation functions, each of the autocorrelation functions in the sequence being representative of an autocorrelation function of a portion of the electric signal; and (D) temporal filter means for temporally filtering the autocorrelation functions to generate a lag histogram.
Claim 13
Dependent Claim
102 words
A fetal heart rate monitor for measuring the heart rate of a fetus, comprising: (A) means for generating an ultrasound signal that propagates into the fetus; (B) means for receiving an ultrasound reflection signal reflected by the fetus and means for converting the ultrasound reflection signal to an electrical signal; (C) autocorrelation means, responsive to the electric signal, for generating a sequence of autocorrelation functions, each of the autocorrelation functions in the sequence being representative of an autocorrelation function of a portion of the electric signal; and (D) temporal filter means for temporally filtering the autocorrelation functions to generate a lag histogram.
Claim 14
Dependent Claim
27 words
A fetal heart rate monitor according to claim 11, further including means for sampling the electrical signal at a sampling frequency and thereby generating a sampled signal.
Claim 15
Dependent Claim
25 words
A fetal heart monitor according to claim 12, further including band pass filter means for filtering the sampled signal and thereby generating a filtered signal.
Claim 16
Dependent Claim
45 words
A fetal heart monitor according to claim 13, wherein the autocorrelation means includes means for receiving the filtered signal and generating therefrom a rectified signal, each portion of the rectified signal being equal to an absolute value of a corresponding portion of the filtered signal.
Claim 17
Dependent Claim
29 words
A fetal heart monitor according to claim 14, wherein the autocorrelation means further includes means for generating a transform signal representative of a Fourier transform of the rectified signal.
Claim 18
Dependent Claim
27 words
A fetal heart monitor according to claim 15, further including means for multiplying the transform signal by a conjugate signal and thereby generating a frequency correlation signal.
Claim 19
Dependent Claim
24 words
A fetal heart monitor according to claim 16, further including means for filtering the frequency correlation signal and thereby generating a filtered frequency signal.
Claim 20
Dependent Claim
33 words
A fetal heart monitor according to claim 17, further including means for generating one of the autocorrelation functions by generating a signal representative of an inverse Fourier transform of the filtered frequency signal.
Claim 21
Dependent Claim
20 words
A fetal heart monitor according to claim 11, further including means for locating a main peak in the lag histogram.
Claim 22
Dependent Claim
33 words
A system according to claim 19, further including means for locating a peak in one of the autocorrelation functions that is within a threshold distance of the main peak in the lag histogram.
Claim 23
Dependent Claim
31 words
A fetal heart rate monitor according to claim 11, further including means for sampling the electrical signal at a plurality of sampling frequencies and thereby generating a plurality of sampled signals.
Claim 24
Dependent Claim
32 words
A fetal heart monitor according to claim 11, further including means for sampling the electrical signal at first, second, and third sampling frequencies and thereby generating first, second, and third sampled signals.
Claim 25
Dependent Claim
33 words
A fetal heart monitor according to claim 22, further including band pass filter means for filtering the first, second, and third sampled signals, and thereby generating first, second, and third filtered signals, respectively.
Claim 26
Independent Claim
114 words
A system for measuring the periodic content of an input signal, comprising: (A) autocorrelation means, responsive to the input signal, for generating an autocorrelation function, at any point in time the autocorrelation function being representative of an autocorrelation function of a portion of the input signal; and (B) lag histogram means for generating a lag histogram from the autocorrelation function, the lag histogram means including means for suppressing transitory features in the autocorrelation function so that said transitory features make a relatively small contribution to the lag histogram and means for emphasizing temporally consistent features of the autocorrelation function so that said temporally consistent features make a relatively large contribution to the lag histogram.
Claim 27
Independent Claim
114 words
A system for measuring the periodic content of an input signal, comprising: (A) autocorrelation means, responsive to the input signal, for generating an autocorrelation function, at any point in time the autocorrelation function being representative of an autocorrelation function of a portion of the input signal; and (B) lag histogram means for generating a lag histogram from the autocorrelation function, the lag histogram means including means for suppressing transitory features in the autocorrelation function so that said transitory features make a relatively small contribution to the lag histogram and means for emphasizing temporally consistent features of the autocorrelation function so that said temporally consistent features make a relatively large contribution to the lag histogram.
Claim 28
Independent Claim
64 words
A system for measuring the periodic content of an input signal, comprising: (A) autocorrelation means, responsive to the input signal, for generating an autocorrelation function, at any point in time the autocorrelation function being representative of an autocorrelation function of a portion of the input signal; and (B) temporal filter means for temporally filtering portions of the autocorrelation function to generate a lag histogram.
Claim 29
Independent Claim
64 words
A system for measuring the periodic content of an input signal, comprising: (A) autocorrelation means, responsive to the input signal, for generating an autocorrelation function, at any point in time the autocorrelation function being representative of an autocorrelation function of a portion of the input signal; and (B) temporal filter means for temporally filtering portions of the autocorrelation function to generate a lag histogram.
References Cited (Backward Citations)
US4453550A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1999-12-17 | 2000-06-17 | 2000-12-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2003-12-17 | 2004-06-17 | 2004-12-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2007-12-17 | 2008-06-17 | 2008-12-17 | $7700.00 | Window Closed / Lapsed |