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US5212490A
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Echo ranging system for detecting velocity and range of targets using composite doppler invariant-like transmissions with suppression of false targets
Assignee: Hydroacoustics Inc
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Filing: 1992-03-13
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Granted: 1993-05-18
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Expires: 2012-03-13
Abstract
Abstract False target (reverberation, clutter, etc.) detection is suppressed in an echo ranging system (sonar or radar) in which target velocity and range are measured using a composite Doppler invariant-like signal having at least two segments, such as are present in a "rooftop" or "vee" HFM signal, such composite signal having an ambiguity function with two or more ridge lines of different slopes that intersect along the zero-velocity time axis. A bank of matched filters provides a distribution of outputs which has an ambiguity function-like character with intersecting pairs of ridge lines, the intersecting points of said pairs characterizing the range and velocity of the echo returns. This distribution is adjusted so that the intersecting ridge lines of each pair have equal and opposite slopes with respect to the time axis. In particular, fixed reverberators, which would have ridge lines intersecting on the zero-velocity time axis, would be symmetrical about this axis. A target with velocity v would present ridge lines intersecting along the v-velocity time axis and be symmetrical about that axis. Thus, the reverberation and the moving target would each have crossed ridge lines whose characteristic intersecting patterns would each exhibit symmetries, but about separate and distinct axes. False targets, including clutter and reverberation, are suppressed by subtracting from the adjusted output distribution, a replica thereof, folded (rotated) 180° about a time axis containing the intersection of the ridge line pair corresponding to the false target which is to be suppressed. The rotation and subtraction of the replica from the adjusted distribution provides a set of outputs from which the real target velocity and range can be determined. The rotation-subtraction process can be implemented on an on-going basis to suppress a plurality or continuum of false targets and to achieve a desired width of a Doppler notch covering an arbitrary range of velocities.
Inventors
- 👤 David E. Nelson
- 👤 John V. Bouyoucos
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 23:52
CPC Classifications
G; G01; G01S; G01S13/00; G01S13/02; G01S13/50; G01S13/58; G01S13/583; G01S13/584; G01S13/06; G01S13/08; G01S13/32; G01S13/34
Claims Analysis
Total Claims: 24
Claim 1
Independent Claim
333 words
An echo ranging system for determining simultaneously the range and velocity of moving targets and for suppressing unwanted returns including reverberation, clutter and returns from false targets, said system comprising: means for transmitting a composite signal comprised of at least two segments, each having Doppler invariant-like characteristics as well as a time-bandwidth product greater than unity, said composite signal also having an ambiguity function in velocity-time space, said space having velocity and time axes that are perpendicular, said ambiguity function having at least a first pair of ridge lines which intersect along the zero-velocity time axis, each ridge line of said at least first pair having a different slope with respect to said zero-velocity time axis; means for receiving echo returns from said transmitted signal; a bank of matched filters; means for passing said echo returns through said bank of matched filters to provide a distribution of outputs which characterize the range and velocity properties of said echo returns; detection means operative upon said outputs for providing an ambiguity function-like detected output distribution in velocity-time space, said output distribution being formed by intersecting second pairs of ridge lines, said intersections occurring uniquely in time and velocity to define individually the range and velocity of said echo returns; means for adjusting at least one ridge line of each said second, intersecting ridge line pair of said distribution to make the slopes of said ridge lines of said second, intersecting ridge line pairs equal and opposite with respect to the time axis to provide an adjusted output distribution; means for providing continuously a replica of said adjusted output distribution rotated 180° about the time-axis containing the intersection of a ridge line pair corresponding to an unwanted return; means for combining said rotated adjusted replica of said output distribution with said adjusted output distribution in time alignment to obtain a combined distribution in which said unwanted return is suppressed; and means responsive to said combined distribution for providing the range and velocity of said moving targets.
Claim 2
Dependent Claim
333 words
An echo ranging system for determining simultaneously the range and velocity of moving targets and for suppressing unwanted returns including reverberation, clutter and returns from false targets, said system comprising: means for transmitting a composite signal comprised of at least two segments, each having Doppler invariant-like characteristics as well as a time-bandwidth product greater than unity, said composite signal also having an ambiguity function in velocity-time space, said space having velocity and time axes that are perpendicular, said ambiguity function having at least a first pair of ridge lines which intersect along the zero-velocity time axis, each ridge line of said at least first pair having a different slope with respect to said zero-velocity time axis; means for receiving echo returns from said transmitted signal; a bank of matched filters; means for passing said echo returns through said bank of matched filters to provide a distribution of outputs which characterize the range and velocity properties of said echo returns; detection means operative upon said outputs for providing an ambiguity function-like detected output distribution in velocity-time space, said output distribution being formed by intersecting second pairs of ridge lines, said intersections occurring uniquely in time and velocity to define individually the range and velocity of said echo returns; means for adjusting at least one ridge line of each said second, intersecting ridge line pair of said distribution to make the slopes of said ridge lines of said second, intersecting ridge line pairs equal and opposite with respect to the time axis to provide an adjusted output distribution; means for providing continuously a replica of said adjusted output distribution rotated 180° about the time-axis containing the intersection of a ridge line pair corresponding to an unwanted return; means for combining said rotated adjusted replica of said output distribution with said adjusted output distribution in time alignment to obtain a combined distribution in which said unwanted return is suppressed; and means responsive to said combined distribution for providing the range and velocity of said moving targets.
Claim 3
Dependent Claim
52 words
The system according to claim 1 wherein said bank of matched filters comprises a bank of correlators whose individual replicas are a set of N of said composite signals whose individual time bases have been adjusted to match N velocities to be detected, the outputs of said correlators forming said distribution outputs.
Claim 4
Dependent Claim
90 words
The system according to claim 1 wherein said bank of matched filters includes a plurality of correlators, each correlator having, as a signal replica, a different one of the segments of said composite signal; said correlators transforming the frequency shift of said target returns due to the velocities thereof into outputs occurring in time delay relationships corresponding to the velocities and ranges of said targets; and means including a tapped delay and summer matrix through which said outputs of said correlators are coherently combined for providing said distribution of outputs.
Claim 5
Dependent Claim
30 words
The system according to claim 1 further comprising means operative upon said combined distribution for clamping said combined distribution to prevent the outputs thereof being other than the same polarity.
Claim 6
Dependent Claim
57 words
The system according to claim 1 wherein said means for providing said rotated replica includes means for providing a plurality of said rotated replicas each about a different time axis corresponding to a different velocity, and said combining means includes means for combining said plurality of replicas with said adjusted output distribution to obtain said combined distribution.
Claim 7
Dependent Claim
47 words
The system according to claim 1 further comprising means for obtaining said combined distribution by operating said rotated replica providing means and said combining means successively a plurality of times in each of which said rotation is about a different time axis corresponding to a different velocity.
Claim 8
Dependent Claim
51 words
The system according to claim 5 wherein said means for obtaining said combined distribution includes means for selecting said different axes to include the time axis at zero velocity and time axes at velocities above and below said zero velocity-time axis to provide a Doppler-notch of width containing said unwanted returns.
Claim 9
Dependent Claim
51 words
The system according to claim 6 wherein said means for obtaining said combined distribution includes means for selecting said different axes to include the time axis at zero velocity and time axes at velocities above and below said zero velocity-time axis to provide a Doppler-notch of width containing said unwanted returns.
Claim 10
Dependent Claim
72 words
The system according to claim 2 wherein said adjusting means comprises means for changing at least one of the duration and bandwidth of at least one segment of each pair of said composite signal segments to make at least one ridge line of each of said second pairs of ridge lines in said output distribution equal and opposite in slope to the other ridge line in said second pairs of ridge lines.
Claim 11
Dependent Claim
60 words
The system according to claim 2 wherein said adjusting means comprises adjustable delays for outputs of said output distribution from said matched filters which make at least one ridge line of each of said second pairs of ridge lines in said output distribution equal and opposite in slope to the other ridge line in said second pairs of ridge lines.
Claim 12
Dependent Claim
72 words
The system according to claim 3 wherein said adjusting means comprises means for changing at least one of the duration and bandwidth of at least one segment of each pair of said composite signal segments to make at least one ridge line of each of said second pairs of ridge lines in said output distribution equal and opposite in slope to the other ridge line in said second pairs of ridge lines.
Claim 13
Dependent Claim
67 words
The system according to claim 3 wherein said adjusting means comprises means for incrementally adjusting delays for the outputs of said output distribution from said tapped delay and summer matrix to make at least one ridge line of each of said second pairs of ridge lines in said output distribution equal and opposite in slope to the other ridge line in said second pairs of ridge lines.
Claim 14
Dependent Claim
61 words
The system according to claim 12 wherein said tapped delay includes a plurality of sections which are connected to summers of said summer matrix, and said means for incrementally adjusting delays comprises means for delaying the outputs from each of said summers to make each of said second pairs of ridge lines in said output distribution equal and opposite in slope.
Claim 15
Dependent Claim
50 words
The system according to claim 3 further comprising means responsive to the one of said outputs of said combined distribution of outputs which is of greater amplitude than the others of said outputs of said combined distribution of outputs for providing the velocity and range of one of said targets.
Claim 16
Dependent Claim
244 words
An echo ranging system for determining the range and velocity of moving targets, and for suppressing unwanted returns as from reverberation, clutter, or false targets, including reverberation or false targets appearing with a velocity v, where v may be zero or nonzero, said system comprising: means for transmitting a signal of total duration T having a time-bandwidth product greater than unity and an ambiguity function that is distributed symmetrically about the time axis corresponding to zero velocity in time-velocity space; means for receiving echo return signals from moving targets as well as unwanted echo return signals from said reverberation, clutter, or false targets appearing with said velocity v, said unwanted return signals having an ambiguity function that is symmetrical about the time axis corresponding to said velocity v in time-velocity space; a bank of matched filters, each filter of said bank having a signal replica corresponding to a different target velocity; means for passing said echo return signals through said bank of matched filters to provide a distribution of outputs which characterize the range and velocity of said echo returns; means for providing continuously a replication of said output distribution rotated 180° about the time axis corresponding to said velocity v; means for combining said rotated output distribution with said distribution of outputs in time alignment to obtain a combined distribution in which said unwanted returns are suppressed; and means responsive to said distribution for providing the range and velocity of said moving targets.
Claim 17
Dependent Claim
244 words
An echo ranging system for determining the range and velocity of moving targets, and for suppressing unwanted returns as from reverberation, clutter, or false targets, including reverberation or false targets appearing with a velocity v, where v may be zero or nonzero, said system comprising: means for transmitting a signal of total duration T having a time-bandwidth product greater than unity and an ambiguity function that is distributed symmetrically about the time axis corresponding to zero velocity in time-velocity space; means for receiving echo return signals from moving targets as well as unwanted echo return signals from said reverberation, clutter, or false targets appearing with said velocity v, said unwanted return signals having an ambiguity function that is symmetrical about the time axis corresponding to said velocity v in time-velocity space; a bank of matched filters, each filter of said bank having a signal replica corresponding to a different target velocity; means for passing said echo return signals through said bank of matched filters to provide a distribution of outputs which characterize the range and velocity of said echo returns; means for providing continuously a replication of said output distribution rotated 180° about the time axis corresponding to said velocity v; means for combining said rotated output distribution with said distribution of outputs in time alignment to obtain a combined distribution in which said unwanted returns are suppressed; and means responsive to said distribution for providing the range and velocity of said moving targets.
Claim 18
Dependent Claim
34 words
The system according to claim 15 wherein said receiving means includes means for adjusting said return signals to provide the symmetry of said ambiguity function about said time axis corresponding to said velocity v.
Claim 19
Dependent Claim
42 words
The system according to claim 15 wherein said means for providing said replication of said output distribution is operative to repeat said rotation sequentially or simultaneously about neighboring time axes whereby said combining means forms in said combined distribution a Doppler notch.
Claim 20
Dependent Claim
30 words
The system according to claim 15 further comprising means operative upon said combined distribution for clamping said combined distribution to prevent the outputs thereof being other than the same polarity.
Claim 21
Dependent Claim
44 words
The system according to claim 15 wherein said transmitting means includes means for adjusting the signal which is transmitted to provide said unwanted return signals with said ambiguity function that is symmetrical about the time axis corresponding to said velocity v in time-velocity space.
Claim 22
Dependent Claim
94 words
The system, according to claim 15, further comprising means for adjusting at least one of the signal which is transmitted and said distribution of outputs to make said distribution symmetrical with respect to the time axis corresponding to said velocity v in velocity-time space, wherein said output distribution provided by said replication means is the adjusted output distribution provided by said adjusting means, and wherein said combining means operates to combine said adjusted output distribution with the replication of said adjusted output distribution rotated 180° about said time axis corresponding to said velocity v.
Claim 23
Dependent Claim
14 words
The system according to claim 15 wherein said transmitted signal has Doppler invariant-like characteristics.
Claim 24
Dependent Claim
36 words
The system according to claim 15 wherein said means for passing said echo return signals includes means for providing each output of said distribution of outputs as an output coherently processed over said total duration T.
References Cited (Backward Citations)
US3225349A
Cited
US3905033A
Cited
US3798590A
Cited
US3866223A
Cited
US3883871A
Cited
US4697186A
Cited
US4035800A
Cited
US4398274A
Cited
US4933914A
Cited
US5077702A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1996-05-17 | 1996-11-16 | 1997-05-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2000-05-17 | 2000-11-16 | 2001-05-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2004-05-17 | 2004-11-16 | 2005-05-18 | $7700.00 | Window Closed / Lapsed |