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US 5,212,489 AGranted
Echo ranging system for detecting velocity of targets using composite doppler invariant transmissions
AssigneeHydroacoustics Inc.
InventorDavid E. Nelson
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AssigneeHydroacoustics Inc.
InventorDavid E. Nelson
Estimating the term…
Target velocity and range are measured with high resolution in an echo ranging system (sonar or radar) using composite Doppler invariant signals consisting of at least two segments, such as "rooftop" or "vee" HFM signals, such composite signals having ambiguity functions that intersect along the zero-velocity time axis with ridge lines slanted in different directions. A single correlator is 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 coherent summers which output a coherent correlation-like detection peak in a bin which corresponds to the target's velocity. Thus, one correlator for each transmission segment together with a tapped delay line and summer network may be used for velocity detection, with high precision range detection, based upon the timing of the detection peak with respect to the transmitted signal, also being implemented at the same time, thereby avoiding the classical need for an expensive bank of correlators (one for each velocity bin) and yielding significant economies for the simultaneous high resolution measurement of range and velocity for a target by means of echo ranging.
Apparatus for measuring simultaneously the velocity and range of a target which comprises means for generating a composite signal having a plurality of segments which define an ambiguity function in time and velocity having at least two ridge lines which have different time-velocity slopes and which intersect along the zero-velocity time axis of said ambiguity function, means for transmitting at a transmit time said composite signal in the direction of a target, means for receiving a composite return signal from said target following incidence of said composite signals thereon, means for correlating the composite return signal with replicas of each of said segments to transform the frequency shift of said target return due to the velocity thereof into outputs occurring in time-delayed relationships corresponding to the velocity and range of the target, and means for coherently summing said outputs in time-delayed relationship to produce a plurality of coherent sums from which target velocity and range are determinable.
A method for detecting simultaneously the velocity and range 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 ridge lines which have different time-velocity slopes and which intersect along the zero-velocity time axis of said ambiguity function, transmitting said composite signal at a certain time in the direction of a target, receiving a composite return signal from said target following incidence of said composite signal thereon, correlating the composite return signal with replicas of each of said segments to transform the frequency shift of said target return due to the velocity thereof into outputs occurring in time-delayed relationships corresponding to the velocity and range of the target, and said outputs coherently said outputs summing them in time-delayed relationship to produce a plurality of sums from which target velocity and range are determinable.
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-delayed relationship corresponding to the velocity of the target, and coherently summing said outputs in amplitude and phase in time-delayed relationship to provide a plurality of sums to determine said velocity.
In an echo-ranging system, which illuminates an object with a composite signal transmission having first and second components which sweep in time and 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 delaying and coherently summing said outputs to produce a plurality of coherent sums, and means for detecting the velocity of said object from said plurality of sums.
Apparatus for detecting the velocity of a target which comprises means for 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, means for receiving a return signal from said target upon incidence of said composite signal thereon, means for correlating the return signal 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-delayed relationship corresponding to the velocity of said target, and summing said outputs to provide a plurality of coherent sums to detect said velocity.
The apparatus according to claim, 26 wherein said outputs comprise a first output and a second output, and wherein said summing means comprises means for successively delaying said outputs and coherently summing each said successively delayed first output with each said successively delayed second output to produce said plurality of coherent sums, and means for detecting the velocity of said target in accordance with the maximum amplitude one of said sums.
The apparatus according to claim, 26 wherein said outputs comprise at least a first output and a second output, and said summing means comprises means for 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 means for coherently summing said first and second successions of outputs in inverse time order to produce said plurality of coherent sums thereof, the one of said sums which is of maximum amplitude corresponding to the velocity of said target.
Dependencies are inferred from the claim text.