| 摘要 |
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 DEG 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. |
