US 4,409,899 AGranted

Acoustic amplitude-doppler target ranging system

AssigneeThe United States of America as represented by the Secretary of the Air Force

InventorsThomas E. Owen, Sidney A. Suhler, Wendell R. Peters

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Abstract

An acoustic target sensor and ranging system automatically detects military targets and provides a munition firing signal at the appropriate target position and time. An amplitude-doppler circuit is utilized to predict the time of closest approach to a munition by a target by measuring the time interval between zero crossings of the second and third derivatives of the received acoustic wave amplitude function. The circuit produces a firing signal by logically ANDing the closest point of approach signal it develops with a signal that indicates when target range is within specified limits. The circuit is realized by means of conventional electronic zero crossing detectors, an up-down counter, dividers, sample and hold devices and voltage comparators. The acoustic target signal is obtained from an omni-directional microphone the output of which is amplified and rectified.

Claims7

Dependent claims

An acoustic amplitude-doppler system for determining the distance to the closest point of approach to a munition and the time of arrival thereat of a moving target, said acoustic amplitude-doppler system comprising

an acoustic sensor circuit for sensing moving target sound waves and generating an input amplitude function signal P in response thereto,
a differentiating circuit receiving said input signal and developing signals P, P and P, said developed signals representing respectively the first, second and third derivatives of said input signal,
a time determining circuit receiving said second and third derivative signals P and P and generating from the times t.sub.2, t.sub.3 of the zero crossings thereof and from a time interval ratio K, a response indicating the predicted time t.sub.c of target arrival at said closest point of approach, and
a distance determining circuit receiving (a) a signal having a frequency f.sub.o responsive to spectral lines in said moving target sound waves, (b) input amplitude function P and (c) first derivative signal P, and developing therefrom a response indicating the predicted distance d of the closest point of approach of said target to said munition.

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Dependencies are inferred from the claim text.