Apparatus and method for locating an emitter using RF carrier or PRF measurement ratios
First Claim
1. An apparatus for determining from a moving observer the location, including latitude, longitude, altitude, and velocity, of an emitter from the signal Doppler shift, comprising:
- a receiver for receiving one of a continuous wave or pulsed signal;
a frequency measuring device for measuring the emitter signal frequency over sequential dwell intervals;
a time measuring device for measuring the time between successive dwell intervals;
an observer velocity measuring device for measuring a change in observer velocity between successive dwell intervals;
first computing means for computing ratios of the frequency measurements from said frequency measuring device;
logic means for associating said frequency ratios with;
(a) the unknown emitter signal angle-of-arrival (AOA) if the moving observer is traveling in a straight path and the time between successive dwell intervals is sufficiently short such that any change in signal AOA is undetectable from said frequency ratios;
(b) the unknown emitter signal direction of arrival (DOA) if the moving observer is performing dogleg maneuvers and the time between successive dwell intervals is sufficiently short such that any change in signal DOA is undetectable from said frequency ratios;
(c) the unknown range to the emitter signal if the moving observer is performing maneuvers within a known envelope and the time between successive dwell intervals is sufficiently long such that any change in signal DOA is detectable from said frequency ratios;
second computing means for computing emitter location using the measurement ratios received from said first computing means and the association received from said logic means, and determining the angle of arrival if association (a) is used, emitter range if association (b) is used, or sequential changes in emitter range if association (c) is used.
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Abstract
A method and apparatus for determining from a moving observer the location, in terms of latitude, longitude, altitude, and velocity, of a stationary or moving radar emitting a pulsed or continuous-wave signal. The moving observer extracts from the radar signal significant electronic support measures (ESM) parameters, including frequency, pulse repetition interval, and pulse width, and determines from those parameters whether a radio frequency (RF) or pulse repetition frequency (PRF) measurement technique is appropriate, and whether the radar signal angle-of-arrival (AOA) must be computed. The emitter location is computed using a ratio of sequential frequency measurements, and the moving observer continues to collect frequency measurements until the location of the emitter can be established to within a predetermined degree of certainty.
74 Citations
16 Claims
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1. An apparatus for determining from a moving observer the location, including latitude, longitude, altitude, and velocity, of an emitter from the signal Doppler shift, comprising:
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a receiver for receiving one of a continuous wave or pulsed signal; a frequency measuring device for measuring the emitter signal frequency over sequential dwell intervals; a time measuring device for measuring the time between successive dwell intervals; an observer velocity measuring device for measuring a change in observer velocity between successive dwell intervals; first computing means for computing ratios of the frequency measurements from said frequency measuring device; logic means for associating said frequency ratios with; (a) the unknown emitter signal angle-of-arrival (AOA) if the moving observer is traveling in a straight path and the time between successive dwell intervals is sufficiently short such that any change in signal AOA is undetectable from said frequency ratios; (b) the unknown emitter signal direction of arrival (DOA) if the moving observer is performing dogleg maneuvers and the time between successive dwell intervals is sufficiently short such that any change in signal DOA is undetectable from said frequency ratios; (c) the unknown range to the emitter signal if the moving observer is performing maneuvers within a known envelope and the time between successive dwell intervals is sufficiently long such that any change in signal DOA is detectable from said frequency ratios; second computing means for computing emitter location using the measurement ratios received from said first computing means and the association received from said logic means, and determining the angle of arrival if association (a) is used, emitter range if association (b) is used, or sequential changes in emitter range if association (c) is used. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method for determining from a moving observer the location of a radar signal from an emitter, comprising the steps of:
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(a) receiving the signal from the emitter; (b) extracting electronic support measures (ESM) parameters from the signal, said parameters including frequency, pulse repetition interval (PRI), and pulse width; (c) flying a constant-velocity track with the moving observer; (d) measuring the signal frequency during said constant-velocity track; (e) generating a ratio of signal frequency measurements; (f) associating said ratio of signal frequency measurements with one of emitter signal angle-of-arrival or emitter location; (g) calculating an estimate of emitter location; (h) repeating steps (c) through (g) until said calculation of emitter location reaches a predetermined convergence. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14, 15, 16)
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Specification