US5912822A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Frequency domain processing of Doppler signals in a traffic monitoring system
Assignee: Transcore LP
•
Filing: 1996-10-15
•
Granted: 1999-06-15
•
Expires: 2016-10-15
Abstract
Abstract Frequency domain processing is used to determine rapidly whether false signals are present, and to improve the accuracy of speed measurements by rejecting speed measurements that could be inaccurate due to the presence of false signals. A Doppler signal responsive to speed of a moving vehicle is generated by a Doppler radar transceiver. A digital computer transforms the Doppler signal into a frequency domain signal such as an energy spectrum, and the speed of the moving vehicle is computed from the weighted arithmetic mean of the energy spectrum. The mean value, however, is rejected as an indication of speed if the variance of the energy spectrum from the mean exceeds a threshold, or if a differential of the spectrum with respect to frequency exceeds a threshold. The frequency domain processing of the present invention can also be used to reject certain bands of frequencies in the Doppler signal, such as bands of frequencies that differ from the mean value by more than a threshold, and the mean value can then be recomputed to provide an even better indication of the speed of the moving vehicle. Moreover, speed samples computed from successive frames of spectrum can be averaged, and the average value can be rejected as an indication of speed if the variance of the speed samples about the average value exceeds a threshold, or if the difference between successive speed samples exceeds a threshold.
Inventors
- 👤 Clint A. Davis
- 👤 Gary L. Mee
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 12:54
CPC Classifications
G; G01; G01S; G01S7/00; G01S7/02; G01S7/41; G01S7/415; G01S11/00; G01S11/02; G01S11/10; G01S13/00; G01S13/02; G01S13/50; G01S13/58; G01S13/581; G01S13/88; G01S13/91; G01S13/92
Claims Analysis
Total Claims: 23
Claim 1
Independent Claim
87 words
A method of determining a speed of a moving vehicle, said method comprising the steps of: (a) operating a Doppler radar transceiver to generate a Doppler signal responsive to said speed of said moving vehicle; (b) operating a digital computer to transform said Doppler signal into a frequency domain signal, and to determine said speed of said moving vehicle by computing a statistic of said frequency domain signal, wherein the frequency domain signal indicates a distribution of energy of the Doppler signal as a function of frequency.
Claim 2
Independent Claim
87 words
A method of determining a speed of a moving vehicle, said method comprising the steps of: (a) operating a Doppler radar transceiver to generate a Doppler signal responsive to said speed of said moving vehicle; (b) operating a digital computer to transform said Doppler signal into a frequency domain signal, and to determine said speed of said moving vehicle by computing a statistic of said frequency domain signal, wherein the frequency domain signal indicates a distribution of energy of the Doppler signal as a function of frequency.
Claim 3
Dependent Claim
30 words
The method as claimed in claim 1, wherein said digital computer transforms said Doppler signal into a frequency domain signal by computing a fast Fourier transform of the Doppler signal.
Claim 4
Dependent Claim
52 words
The method as claimed in claim 1, further comprising the step of computing a differential of said frequency domain signal with respect to frequency, and comparing said differential to a threshold, and rejecting said mean value as a correct indication of said speed of said vehicle when said differential exceeds said threshold.
Claim 5
Dependent Claim
46 words
The method as claimed in claim 1, wherein said frequency domain signal indicates a distribution of energy of said Doppler signal as a function of frequency, and said statistic is a moment of said distribution of energy of said Doppler signal as a function of frequency.
Claim 6
Dependent Claim
29 words
The method as claimed in claim 4, wherein said moment is a weighted arithmetic mean of said distribution of energy of said Doppler signal as a function of frequency.
Claim 7
Dependent Claim
30 words
The method as claimed in claim 4, wherein said moment is a variance about a mean of said distribution of energy of said Doppler signal as a function of frequency.
Claim 8
Dependent Claim
29 words
The method as claimed in claim 1, wherein said statistic is a mean value of said frequency domain signal, and said mean value indicates said speed of said vehicle.
Claim 9
Dependent Claim
51 words
The method as claimed in claim 7, further comprising the steps of computing a variance of said frequency domain signal about said mean value, comparing said variance to a threshold, and rejecting said mean value as a correct indication of said speed of said vehicle when said variance exceeds said threshold.
Claim 10
Dependent Claim
63 words
The method as claimed in claim 7 further comprising the steps of identifying portions of said frequency-domain signal having frequencies that differ from said mean value by more than a threshold, and recomputing said mean value while excluding the identified portions of said frequency-domain signal, so that the recomputed mean value is an even better indication of the speed of said moving vehicle.
Claim 11
Independent Claim
179 words
A method of monitoring moving vehicles, said method comprising the steps of: (a) operating a Doppler radar transceiver to generate a Doppler signal responsive to speeds of said moving vehicles; and (b) operating a digital computer to transform said Doppler signal into a frequency domain signal, wherein the frequency domain signal indicates a distribution of energy of the Doppler signal as a function of frequency, and wherein the frequency domain signal has successive portions, and for each portion, (i) to compute a mean value of said each portion of said frequency domain signal, (ii) to compute a variance of said each portion of said frequency domain signal from said mean value, and (iii) to compare said variance to a threshhold, and when said variance is greater than said threshhold, to reject said each portion of said frequency domain signal as an indication of a speed of any of said vehicles, and when said variance is less than said threshhold, to compute from said each portion of said frequency domain signal a measurement of speed of one of said signals.
Claim 12
Independent Claim
179 words
A method of monitoring moving vehicles, said method comprising the steps of: (a) operating a Doppler radar transceiver to generate a Doppler signal responsive to speeds of said moving vehicles; and (b) operating a digital computer to transform said Doppler signal into a frequency domain signal, wherein the frequency domain signal indicates a distribution of energy of the Doppler signal as a function of frequency, and wherein the frequency domain signal has successive portions, and for each portion, (i) to compute a mean value of said each portion of said frequency domain signal, (ii) to compute a variance of said each portion of said frequency domain signal from said mean value, and (iii) to compare said variance to a threshhold, and when said variance is greater than said threshhold, to reject said each portion of said frequency domain signal as an indication of a speed of any of said vehicles, and when said variance is less than said threshhold, to compute from said each portion of said frequency domain signal a measurement of speed of one of said signals.
Claim 13
Dependent Claim
58 words
The method as claimed in claim 10, wherein said step of transforming is performed by converting said Doppler signal to digital samples, and performing a discrete Fourier transform on successive groups of said digital samples, each of said successive groups of digital samples being transformed to produce a corresponding one of said portions of said frequency domain signal.
Claim 14
Dependent Claim
25 words
The method as claimed in claim 11, wherein each portion of said frequency domain signal comprises a series of energy values for respective frequency intervals.
Claim 15
Dependent Claim
42 words
The method as claimed in claim 10, which includes the step of averaging a plurality of speed samples from a plurality of said successive portions of said Doppler signal in order to compute said measurement of speed of one of said vehicles.
Claim 16
Dependent Claim
54 words
The method as claimed in claim 13, further including the step of computing a variance of said speed samples from said measurement of speed of one of said vehicles, and comparing said variance of said speed samples to a threshold value in order to validate said measurement of speed of one of said vehicles.
Claim 17
Dependent Claim
38 words
The method as claimed in claim 13, further including the step of computing differences between successive speed samples, and comparing said differences to a threshold in order to validate said measurement of speed of one of said vehicles.
Claim 18
Dependent Claim
135 words
A traffic monitoring system comprising: (a) a Doppler radar transceiver for emitting a radar beam and generating a Doppler signal responsive to speed of a vehicle when said vehicle passes through said radar beam; (b) an analog-to-digital converter connected to said Doppler radar transceiver for converting said Doppler signal into a series of digital samples which are frequency domain signals that indicate a distribution of energy of the Doppler signl as a function of frequency; and (c) digital computer means connected to said analog-to-digital converter for computing a discrete Fourier transform of successive groups of said series of digital samples to produce a series of frames of spectrum, and from said series of frames of spectrum, to detect the presence of said vehicle in said radar beam and to compute te speed of said vehicle.
Claim 19
Dependent Claim
135 words
A traffic monitoring system comprising: (a) a Doppler radar transceiver for emitting a radar beam and generating a Doppler signal responsive to speed of a vehicle when said vehicle passes through said radar beam; (b) an analog-to-digital converter connected to said Doppler radar transceiver for converting said Doppler signal into a series of digital samples which are frequency domain signals that indicate a distribution of energy of the Doppler signl as a function of frequency; and (c) digital computer means connected to said analog-to-digital converter for computing a discrete Fourier transform of successive groups of said series of digital samples to produce a series of frames of spectrum, and from said series of frames of spectrum, to detect the presence of said vehicle in said radar beam and to compute te speed of said vehicle.
Claim 20
Dependent Claim
71 words
The traffic monitoring system as claimed in claim 16, wherein said digital computer means includes means for computing a mean frequency of said spectrum, means for computing a variance of said spectrum about said mean frequency, means for comparing said variance of said spectrum to a threshold, and means responsive to said variance being less than said threshold for verifying that said vehicle has a speed indicated by said mean frequency.
Claim 21
Dependent Claim
67 words
The traffic monitoring system as claimed in claim 16, wherein said digital computer means includes a first central processor connected to said analog-to-digital converter for computing said discrete Fourier transform, and a second central processor connected to said first central processor for detecting the presence of said vehicle in said radar beam and for computing the speed of said vehicle from said series of frames of spectrum.
Claim 22
Dependent Claim
63 words
The traffic monitoring system as claimed in claim 16, wherein said Doppler radar transceiver includes a pair of detector diodes for generating a pair of channels for said Doppler signal, and wherein said digital computer means includes means for computing discrete Fourier transforms for each channel and combining the discrete Fourier transforms for the channels to produce said series of frames of spectrum.
Claim 23
Dependent Claim
81 words
The traffic monitoring system as claimed in claim 16, wherein said digital computer means includes means for computing a speed sample for each frame of spectrum, means for computing an average of a series of said speed samples, means for computing a variance of said series of said speed samples about said average, and means for comparing said variance of said series of said speed samples to a threshold for verifying that said average represents the speed of said moving vehicle.
References Cited (Backward Citations)
US3122740A
Cited
US3195126A
Cited
US3088388A
Cited
GB945693A
Cited
DE1172066B
Cited
US3148015A
Cited
US3243806A
Cited
US3165373A
Cited
US3206748A
Cited
US3382785A
Cited
DE1597378A1
Cited
US3581647A
Cited
US3603227A
Cited
US3522611A
Cited
US3554102A
Cited
DE1574126A1
Cited
US3438031A
Cited
CH470674A
Cited
US3754253A
Cited
US3579236A
Cited
US3618084A
Cited
US3680043A
Cited
US3626413A
Cited
DE2211462A1
Cited
US3816841A
Cited
JPS4913730A
Cited
US3866165A
Cited
US3849784A
Cited
US3858223A
Cited
DE2356909A1
Cited
US4053909A
Cited
GB1494945A
Cited
GB1480981A
Cited
US3930735A
Cited
US4051499A
Cited
US4173010A
Cited
US4192595A
Cited
DE2802448A1
Cited
US4236140A
Cited
DE2817846A1
Cited
US4344685A
Cited
US4229726A
Cited
US4231039A
Cited
US4335383A
Cited
US4319245A
Cited
DE3034161A1
Cited
US4500868A
Cited
US4444479A
Cited
US4479704A
Cited
US4527894A
Cited
US4408857A
Cited
DE3220434A1
Cited
DE3306040A1
Cited
FR2549263A1
Cited
FR2549625A1
Cited
US4591823A
Cited
DE3422764A1
Cited
US4634254A
Cited
WO1986001615A1
Cited
EP0188694A2
Cited
US4717915A
Cited
US4884072A
Cited
DE3535588A1
Cited
US4664494A
Cited
US4761666A
Cited
US4809030A
Cited
US4789904A
Cited
US4949186A
Cited
US5005042A
Cited
US4866438A
Cited
US4887080A
Cited
US5041828A
Cited
US4988994A
Cited
US4890129A
Cited
US4922339A
Cited
US4984003A
Cited
US4942415A
Cited
US5250946A
Cited
US5082365A
Cited
US5224075A
Cited
US5177691A
Cited
US5239336A
Cited
US5291237A
Cited
EP0513628A2
Cited
US5257056A
Cited
US5221956A
Cited
US5239296A
Cited
US5481504A
Cited
EP0679051A2
Cited
US5525996A
Cited
US5528245A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2002-06-14 | 2002-12-14 | 2003-06-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2006-06-14 | 2006-12-14 | 2007-06-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2010-06-14 | 2010-12-14 | 2011-06-15 | $7700.00 | Window Closed / Lapsed |