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EP0504702A2
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Echo ranging system
Assignee: Hydroacoustics Inc
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Filing: 1992-03-09
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Granted: —
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Expires: 2012-03-09
Abstract
Abstract An echo ranging system (FIG. 9) (sonar or radar) measures target velocity and range 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. (FIGS. 6, 7, 8) A distribution of outputs which has an ambiguity function-like character with intersecting pairs of ridge lines is provided by a matched filter processor 16. The intersecting points of said pairs characterize the range and velocity of the echo returns. This distribution is adjusted (18) so that the intersecting ridge lines of each pair have equal and opposite slopes with respect to the time axis. False targets, including clutter and reverberation, are suppressed (20) 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. A single correlator (38, 40) can be used for each segment, wherein returns from the target are correlated with replicas of each segment of the composite signal to separately transform the Doppler frequency shifts of the target return into outputs whose time relationship provides a frame of reference for high resolution measurement of the velocity of the target. The time relationship measurement is implemented by a set of tapped delay lines and summers (44) which output a coherent, correlation-like detection peak in a bin which corresponds to the target's velocity, thereby avoiding the need for an expensive bank of correlators (one for each velocity bin) and yielding significant economies.
Inventors
- 👤 David E. Nelson
- 👤 John Bouyoucos
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-28 19:31
CPC Classifications
G; G01; G01S; G01S13/00; G01S13/02; G01S13/50; G01S13/58; G01S13/583; G01S13/06; G01S13/08; G01S13/10; G01S13/26; G01S15/00; G01S15/02; G01S15/50; G01S15/58; G01S15/586
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
112 words
A method for detecting the velocity of a target which comprises the steps of generating a composite signal having a plurality of segments which define an ambiguity function in time and velocity having at least two intersecting ridge lines which have different time-velocity slopes, receiving a return signal from said target following incidence of said composite signal thereon, and correlating the return signal separately with replicas of each of said segments to transform the frequency shift of said return signal from said target due to the velocity thereof into coherently related outputs occurring in time relationship corresponding to the velocity of the target, and coherently combining said outputs to determine said velocity.
Claim 2
Independent Claim
112 words
A method for detecting the velocity of a target which comprises the steps of generating a composite signal having a plurality of segments which define an ambiguity function in time and velocity having at least two intersecting ridge lines which have different time-velocity slopes, receiving a return signal from said target following incidence of said composite signal thereon, and correlating the return signal separately with replicas of each of said segments to transform the frequency shift of said return signal from said target due to the velocity thereof into coherently related outputs occurring in time relationship corresponding to the velocity of the target, and coherently combining said outputs to determine said velocity.
Claim 3
Dependent Claim
76 words
The method according to Claim 1 wherein said outputs from said correlating step comprise a first output and a second output, and wherein said combining step is carried out by successively delaying each of said outputs and coherently summing each said successively delayed first output with each said successively delayed second output to produce a plurality of coherent sums, and detecting the velocity of said target in accordance with the maximum amplitude one of said sums.
Claim 4
Dependent Claim
61 words
The method according to Claim 2 wherein said step of successively delaying said outputs is carried out by propagating each of said outputs along different delay lines having successive taps, and said coherent summing step is carried out with the aid of a plurality of summers, each of said summers being connected to different taps of different ones of said lines.
Claim 5
Dependent Claim
91 words
The method according to Claim 1 wherein said outputs comprise at least a first output and second output, and said combining step is carried out by successively delaying said first and second outputs to provide a first succession of successively delayed first outputs and a second succession of successively delayed second outputs, and coherently summing said first and second successions of outputs in inverse time order to produce a plurality of coherent sums thereof, the one of said sums which is of maximum amplitude corresponding to the velocity of said target.
Claim 6
Dependent Claim
104 words
In an echo-ranging system, which illuminates an object with a composite signal transmission having first and second components which sweep in time in opposite directions with respect to frequency and which is returned as a return signal from said object, a system for detecting the velocity of said object which comprises means for correlating said return signal with replicas of said components to provide a pair of outputs corresponding to said first and second components, and means for coherently combining said pair of outputs for detecting the velocity of said object in accordance with the intersection in velocity-time space of said pair of outputs.
Claim 7
Dependent Claim
104 words
In an echo-ranging system, which illuminates an object with a composite signal transmission having first and second components which sweep in time in opposite directions with respect to frequency and which is returned as a return signal from said object, a system for detecting the velocity of said object which comprises means for correlating said return signal with replicas of said components to provide a pair of outputs corresponding to said first and second components, and means for coherently combining said pair of outputs for detecting the velocity of said object in accordance with the intersection in velocity-time space of said pair of outputs.
Claim 8
Dependent Claim
42 words
The velocity detecting system according to Claim 5 wherein said transmission is a composite Doppler invariant FM transmission, and said detecting means includes means for coherently combining said outputs to provide at least one combined output which is maximum, identifying said velocity.
Claim 9
Dependent Claim
60 words
The system according to Claim 5 wherein said coherent combining means includes means for relatively delaying said pair of outputs to provide a plurality of further outputs having different relative delays, and a plurality of means for summing said further delayed outputs to provide a plurality of summer outputs, and means responsive to said summer outputs for detecting said velocity.
Claim 10
Dependent Claim
26 words
The system according to Claim 6 further comprising means responsive to said combined maximum output for detecting the range of said object from a reference location.
Claim 11
Dependent Claim
224 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 having a time-bandwidth product greater than unity, and an ambiguity function that is distributed 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; 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 replica 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 12
Dependent Claim
224 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 having a time-bandwidth product greater than unity, and an ambiguity function that is distributed 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; 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 replica 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 13
Dependent Claim
34 words
The system according to Claim 9 wherein said receiving means includes means for adjusting said return signals so that the ambiguity function thereof is symmetrical about said time axis corresponding to said velocity v.
Claim 14
Dependent Claim
223 words
The system according to Claim 9 wherein said transmitted signal is 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; wherein said output distribution is an ambiguity function-like 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; further comprising 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; and wherein said replica is 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 at said velocity v.
Claim 15
Dependent Claim
56 words
The system according to Claim 9, 10 or 11 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 of outputs.
Claim 16
Dependent Claim
93 words
The system according to Claim 9, 10 or 11 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 17
Dependent Claim
60 words
The system according to Claim 9, 10 or 11 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 18
Dependent Claim
50 words
The system according to Claim 9, 10 or 11 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 19
Dependent Claim
53 words
The system according to Claim 14 or 15 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 20
Dependent Claim
74 words
The system according to Claim 12 or 13 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 21
Dependent Claim
62 words
The system according to Claim 12 or 13 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 22
Dependent Claim
52 words
The system according to Claim 12 or 13 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.
References Cited (Backward Citations)
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