US5353233A
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Method and apparatus for time varying spectrum analysis
Assignee: National Instruments Corp
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Filing: 1992-03-17
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Granted: 1994-10-04
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Expires: 2012-03-17
Abstract
Abstract A signal analyzer generates a time varying spectrum for input signals characterized by frequency components which change in time. The signal analyzer includes a converter generating a sequence of digital signals representative of an input signal. The sequence of digital signals is supplied to a digital signal processor which computes orthogonal-like discrete Gabor transform coefficients C m ,n in response to the sequence, and a time varying spectrum of the input signal energy in response to the coefficients. Finally, a data processor processes the spectrum for further analysis or display. One particular analysis step for which the time varying spectrum is useful is in partitioning the input signal into separate components. The orthogonal-like discrete Gabor transform coefficients are computed using a non-periodic, localized discrete window function h and a discrete auxiliary function γ, similar to h. The time varying spectrum is computed utilizing a cross-term deleted Wigner-Ville distribution.
Inventors
- 👤 Shie Oian
- 👤 Dapang Chen
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 08:43
CPC Classifications
G; G01; G01R; G01R23/00; G01R23/16
Claims Analysis
Total Claims: 55
Claim 1
Independent Claim
64 words
A signal analyzer, comprising: a source of a sequence of digital signals representative of an input signal; and a processor coupled to the source for computing orthogonal-like discrete Gabor transform coefficients C m ,n in response to the sequence, wherein the processor uses the coefficients to compute a time-varying spectrum of input signal energy; wherein said spectrum is used in analyzing said input signal.
Claim 2
Dependent Claim
64 words
A signal analyzer, comprising: a source of a sequence of digital signals representative of an input signal; and a processor coupled to the source for computing orthogonal-like discrete Gabor transform coefficients C m ,n in response to the sequence, wherein the processor uses the coefficients to compute a time-varying spectrum of input signal energy; wherein said spectrum is used in analyzing said input signal.
Claim 3
Dependent Claim
26 words
The signal analyzer of claim 1, wherein the first processor comprises a first means for generating the coefficients and a second means for computing the spectrum.
Claim 4
Dependent Claim
25 words
The signal analyzer of claim 2, wherein the second means includes storage means for storing a table of factors used in computation of the spectrum.
Claim 5
Dependent Claim
15 words
The signal analyzer of claim 1, wherein the processor computes a cross-term deleted Wigner-Ville distribution.
Claim 6
Dependent Claim
99 words
The signal analyzer of claim 1, wherein the processor includes a computation engine for computing an orthogonal-like discrete Gabor transform resulting in coefficients C m ,n based upon a non-periodic, localized discrete window function h, and a discrete auxiliary function γ similar to h, and wherein the processor further includes a computation engine for computing an energy distribution function for each of the coefficients C m ,n, the energy distribution function including a first factor based upon the magnitude of the Gabor coefficient, and a second factor varying according to the localized discrete window function of the Gabor transform.
Claim 7
Dependent Claim
57 words
The signal analyzer of claim 5, wherein the processor includes storage means for storing a precomputed table of values used for the second factors of the energy distribution function for a particular coefficient C m ,n accessible in response to coordinates i,k of factors of the localized discrete window function near coordinates m,n of the particular coefficient.
Claim 8
Dependent Claim
38 words
The signal analyzer of claim 5, wherein the processor determines an update region for each coefficient C m ,n in response to the first factor, and the distribution for each coefficient is computed within the determined update region.
Claim 9
Dependent Claim
35 words
The signal analyzer of claim 1, further including an input buffer memory system connected to receive the sequence supplied by the source and supply the sequence to the processor in a set of overlapping frames.
Claim 10
Dependent Claim
65 words
A signal analyzer, comprising: a source of a sequence of digital signals representative of an input signal; a first processor, coupled to the source, for computing orthogonal-like discrete Gabor transform coefficients C m ,n in response to the sequence, and a time-varying spectrum of input signal energy in response to the coefficients; and a second processor, coupled to the first processor, which processes the spectrum.
Claim 11
Dependent Claim
65 words
A signal analyzer, comprising: a source of a sequence of digital signals representative of an input signal; a first processor, coupled to the source, for computing orthogonal-like discrete Gabor transform coefficients C m ,n in response to the sequence, and a time-varying spectrum of input signal energy in response to the coefficients; and a second processor, coupled to the first processor, which processes the spectrum.
Claim 12
Dependent Claim
21 words
The signal analyzer of claim 9, wherein the second processor includes: means, responsive to the spectrum, for partitioning the input signal.
Claim 13
Dependent Claim
32 words
The signal analyzer of claim 9, wherein the second processor includes: means, responsive to the spectrum, for displaying a graphic representation of the spectrum for use in analysis of the input signal.
Claim 14
Dependent Claim
26 words
The signal analyzer of claim 9, wherein the first processor comprises a first means for generating the coefficients and a second means for computing the spectrum.
Claim 15
Dependent Claim
25 words
The signal analyzer of claim 12, wherein the second means includes storage means for storing a table of factors used in computation of the spectrum.
Claim 16
Dependent Claim
21 words
The signal analyzer of claim 12, wherein the second means comprises a computation engine for computing a cross-term deleted Wigner-Ville distribution.
Claim 17
Dependent Claim
100 words
The signal analyzer of claim 12, wherein the first means includes a computation engine for computing an orthogonal-like discrete Gabor transform resulting in coefficients C m ,n based upon a non-periodic, localized discrete window function h, and a discrete auxiliary function γ similar to h, and wherein the second means includes a computation engine for computing an energy distribution function for each of the coefficients C m ,n, the energy distribution function including a first factor based upon the magnitude of the Gabor coefficient, and a second factor varying according to the localized discrete window function of the Gabor transform.
Claim 18
Dependent Claim
63 words
The signal analyzer of claim 15, wherein the second means includes storage means for storing a precomputed table of values used for the second factor of the energy distribution function for a particular coefficient C m ,n computed by the first means, accessible in response to coordinates i,k of factors of the localized discrete window function near coordinates m,n of the particular coefficient.
Claim 19
Dependent Claim
42 words
The signal analyzer of claim 15, wherein the second means includes means for determining an update region for each coefficient C m ,n in response to the first factor, and the distribution for each coefficient is computed within the determined update region.
Claim 20
Dependent Claim
36 words
The signal analyzer of claim 9, further including an input buffer memory system connected to receive the sequence supplied by the source and supply the sequence to the first processor in a set of overlapping frames.
Claim 21
Dependent Claim
32 words
The signal analyzer of claim 9, further including an output buffer memory system connected to receive the time-varying spectrum from the first processor and supply the time-varying spectrum to the second processor.
Claim 22
Dependent Claim
15 words
The signal analyzer of claim 9, wherein the source comprises an analog to digital converter.
Claim 23
Dependent Claim
13 words
The signal analyzer of claim 20, wherein the source includes an anti-aliasing filter.
Claim 24
Independent Claim
132 words
A method for computing a time-varying spectrum of an input signal, comprising: acquiring a sequence of digital signals representative of the input signal; sampling the sequence of digital signals to define a plurality of windows of length L, each window in the plurality including a plurality of digital signals and each window shifted by length ΔM digital signals relative to an adjacent window; computing orthogonal-like discrete Gabor transform coefficients C m ,n in sampling intervals ΔN and ΔM, for n=0 through N-1 for each window m, and for the plurality of windows m=0 through M-1, such that ΔN ΔM is less than L; computing the time-varying spectrum of energy of the input signal in response to the coefficients C m ,n, and analyzing the input signal in response to the time-varying spectrum.
Claim 25
Independent Claim
132 words
A method for computing a time-varying spectrum of an input signal, comprising: acquiring a sequence of digital signals representative of the input signal; sampling the sequence of digital signals to define a plurality of windows of length L, each window in the plurality including a plurality of digital signals and each window shifted by length ΔM digital signals relative to an adjacent window; computing orthogonal-like discrete Gabor transform coefficients C m ,n in sampling intervals ΔN and ΔM, for n=0 through N-1 for each window m, and for the plurality of windows m=0 through M-1, such that ΔN ΔM is less than L; computing the time-varying spectrum of energy of the input signal in response to the coefficients C m ,n, and analyzing the input signal in response to the time-varying spectrum.
Claim 26
Dependent Claim
19 words
The method of claim 22, wherein the step of computing a spectrum includes computing a cross-term deleted Wigner-Ville Distribution.
Claim 27
Dependent Claim
41 words
The method of claim 22, wherein the step of computing orthogonal-like discrete Gabor transform coefficients C m ,n includes performing a discrete Gabor transform with a non-periodic, localized discrete window function h, and a discrete auxiliary function γ similar to h.
Claim 28
Dependent Claim
11 words
The method of claim 24, wherein h and γ are non-overlapping.
Claim 29
Dependent Claim
11 words
The method of claim 24, wherein h is a gaussian function.
Claim 30
Dependent Claim
33 words
The method of claim 26, wherein the gaussian function h has a variance σ 2 less than or equal to about 0.5(L/12) 2 , wherein L is a window length of window m.
Claim 31
Dependent Claim
18 words
The method of claim 24, wherein γ is similar to h in the sense of least squares error.
Claim 32
Dependent Claim
58 words
The method of claim 22, wherein the step of computing the time-varying spectrum includes providing a lookup table having an entry for each point i,k in the spectrum within a region around points mΔM,nΔN, the entries storing precomputed values for use in calculating the time-varying spectrum; and computing the time-varying spectrum using the values in the lookup table.
Claim 33
Dependent Claim
48 words
The method of claim 22, wherein the step of computing the time-varying spectrum includes: for each coefficient C m ,n, determining an update region around the coefficient in response to the magnitude of the coefficient; and computing the time-varying spectrum within the respective update regions for each coefficient.
Claim 34
Dependent Claim
106 words
The method of claim 22, wherein the step of computing the time-varying spectrum includes for each coefficient C m ,n, determining an update region around the coefficient in response to the magnitude of the coefficient; and providing a lookup table having an entry for each point i,k in the time-varying spectrum within a region around points mΔM,nΔN, the entries storing precomputed values for use in a cross terms deleted Wigner-Ville distribution, wherein the lookup table includes enough factors to compute the cross terms deleted Wigner-Ville distribution for the coefficient having the largest update region; and computing the time-varying spectrum using the values in the lookup table.
Claim 35
Dependent Claim
18 words
The method of claim 22, wherein the step of analyzing includes generating a graphic representation of the spectrum.
Claim 36
Dependent Claim
24 words
The method of claim 22, wherein the step of analyzing includes partitioning the sequence of digital signals in time in response to the spectrum.
Claim 37
Dependent Claim
12 words
The method of claim 22, wherein the input signal comprises acoustic energy.
Claim 38
Dependent Claim
12 words
The method of claim 22, wherein the input signal comprises electromagnetic energy.
Claim 39
Dependent Claim
11 words
The method of claim 22, wherein the input signal comprises speech.
Claim 40
Dependent Claim
12 words
The method of claim 22, wherein the input signal comprises radar signals.
Claim 41
Dependent Claim
12 words
The method of claim 22, wherein the input signal comprises sonar signals.
Claim 42
Dependent Claim
15 words
The method of claim 22, wherein the step of acquiring includes filtering the input signal.
Claim 43
Dependent Claim
136 words
A signal analyzer, comprising: a converter, having an input, which generates a sequence of digital signals representative of an input signal supplied to the input; input memory means, connected to receive the sequence generated by the converter, for supplying the sequence in a set of overlapping frames; first means, coupled to the input memory means, for computing orthogonal-like discrete Gabor transform coefficients C m ,n in response to the set of overlapping frames, by performing a discrete Gabor transform with a localized, gaussian discrete window function h, and a discrete auxiliary function γ similar to h; second means, coupled with the first means, for generating a time-varying spectrum of input signal energy in response to the coefficients by computing a cross-terms deleted Wigner-Ville distribution; and analysis means, coupled to the second means, for processing the spectrum.
Claim 44
Dependent Claim
136 words
A signal analyzer, comprising: a converter, having an input, which generates a sequence of digital signals representative of an input signal supplied to the input; input memory means, connected to receive the sequence generated by the converter, for supplying the sequence in a set of overlapping frames; first means, coupled to the input memory means, for computing orthogonal-like discrete Gabor transform coefficients C m ,n in response to the set of overlapping frames, by performing a discrete Gabor transform with a localized, gaussian discrete window function h, and a discrete auxiliary function γ similar to h; second means, coupled with the first means, for generating a time-varying spectrum of input signal energy in response to the coefficients by computing a cross-terms deleted Wigner-Ville distribution; and analysis means, coupled to the second means, for processing the spectrum.
Claim 45
Dependent Claim
35 words
The signal analyzer of claim 40, wherein h is a gaussian function having a variance σ 2 less than or equal to about 0.5(L/12) 2 , wherein L is a window length of window m.
Claim 46
Dependent Claim
98 words
The signal analyzer of claim 40, wherein a contribution to the distribution of a particular Gabor transform coefficient computed by the first means is computed as a function of a first factor based upon the magnitude of the particular Gabor transform coefficient, and a second factor varying according to the localized window function of the Gabor transform, and the second means includes storage means for storing a precomputed table of values used for the second factor, accessible in response to coordinates i,k of factors of the localized window function near coordinates m,n of the particular Gabor transform coefficient.
Claim 47
Dependent Claim
43 words
The signal analyzer of claim 42, wherein the second means includes means for determining an update region for each coefficient C m ,n in response to the first factor, and the distribution for each coefficient is computed only within the determined update region.
Claim 48
Dependent Claim
32 words
The signal analyzer of claim 40, further including an output buffer memory system connected to receive the distribution data from the first processor and supply the distribution data to the second processor.
Claim 49
Dependent Claim
13 words
The signal analyzer of claim 40, wherein the converter includes an anti-aliasing filter.
Claim 50
Dependent Claim
191 words
A signal analyzer, comprising: a source of a sequence of digital signals representative of an input signal; a first processor, coupled to the source, wherein said first processor comprises: a first means including a computation engine for computing an orthogonal-like discrete Gabor transform resulting in coefficients C m ,n based upon a non-periodic, localized discrete window function h, and a discrete auxiliary function γ similar to h; and a second means comprising: a computation engine for computing an energy distribution function for each of the coefficients C m ,n, the energy distribution function including a first factor based upon the magnitude of the Gabor coefficient, and a second factor varying according to the localized discrete window function of the Gabor transform; and storage means for storing a precomputed table of values used for the second factor of the energy distribution function for a particular coefficient C m ,n computed by the first means, accessible in response to coordinates i, k of factors of the localized discrete window function near coordinates m, n of the particular coefficient; and a second processor, coupled to the first processor, which processes the energy distribution function.
Claim 51
Dependent Claim
191 words
A signal analyzer, comprising: a source of a sequence of digital signals representative of an input signal; a first processor, coupled to the source, wherein said first processor comprises: a first means including a computation engine for computing an orthogonal-like discrete Gabor transform resulting in coefficients C m ,n based upon a non-periodic, localized discrete window function h, and a discrete auxiliary function γ similar to h; and a second means comprising: a computation engine for computing an energy distribution function for each of the coefficients C m ,n, the energy distribution function including a first factor based upon the magnitude of the Gabor coefficient, and a second factor varying according to the localized discrete window function of the Gabor transform; and storage means for storing a precomputed table of values used for the second factor of the energy distribution function for a particular coefficient C m ,n computed by the first means, accessible in response to coordinates i, k of factors of the localized discrete window function near coordinates m, n of the particular coefficient; and a second processor, coupled to the first processor, which processes the energy distribution function.
Claim 52
Dependent Claim
168 words
A signal analyzer, comprising: a source of a sequence of digital signals representative of an input signal; a first processor, coupled to the source, wherein said first processor comprises: a first means including a computation engine for computing an orthogonal-like discrete Gabor transform resulting in coefficients C m ,n based upon a non-periodic, localized discrete window function h, and a discrete auxiliary function γ similar to h; and a second means comprising: a computation engine for computing an energy distribution function for each of the coefficients C m ,n, the energy distribution function including a first factor based upon the magnitude of the Gabor coefficient, and a second factor varying according to the localized discrete window function of the Gabor transform; and means for determining an update region for each coefficient C m ,n in response to the first factor, wherein the distribution for each coefficient is computed within the determined update region; and a second processor, coupled to the first processor, which processes the energy distribution function.
Claim 53
Dependent Claim
168 words
A signal analyzer, comprising: a source of a sequence of digital signals representative of an input signal; a first processor, coupled to the source, wherein said first processor comprises: a first means including a computation engine for computing an orthogonal-like discrete Gabor transform resulting in coefficients C m ,n based upon a non-periodic, localized discrete window function h, and a discrete auxiliary function γ similar to h; and a second means comprising: a computation engine for computing an energy distribution function for each of the coefficients C m ,n, the energy distribution function including a first factor based upon the magnitude of the Gabor coefficient, and a second factor varying according to the localized discrete window function of the Gabor transform; and means for determining an update region for each coefficient C m ,n in response to the first factor, wherein the distribution for each coefficient is computed within the determined update region; and a second processor, coupled to the first processor, which processes the energy distribution function.
Claim 54
Dependent Claim
107 words
A signal analyzer, comprising: a source of a sequence of digital signals representative of an input signal; an input buffer system connected to receive the sequence supplied by the source; a first processor, coupled to the input buffer which receives the sequence from the input buffer, wherein the input buffer supplies the sequence to the first processor in a set of overlapping frames, wherein the first processor computes orthogonal-like discrete Gabor transform coefficients C m ,n in response to the sequence, and a time-varying spectrum of input signal energy in response to the coefficients; and a second processor, coupled to the first processor, which processes the spectrum.
Claim 55
Dependent Claim
107 words
A signal analyzer, comprising: a source of a sequence of digital signals representative of an input signal; an input buffer system connected to receive the sequence supplied by the source; a first processor, coupled to the input buffer which receives the sequence from the input buffer, wherein the input buffer supplies the sequence to the first processor in a set of overlapping frames, wherein the first processor computes orthogonal-like discrete Gabor transform coefficients C m ,n in response to the sequence, and a time-varying spectrum of input signal energy in response to the coefficients; and a second processor, coupled to the first processor, which processes the spectrum.
References Cited (Backward Citations)
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| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1997-10-03 | 1998-04-04 | 1998-10-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2001-10-03 | 2002-04-04 | 2002-10-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2005-10-03 | 2006-04-04 | 2006-10-04 | $7700.00 | Window Closed / Lapsed |