Apparatus for measuring moving emitter elevation and azimuth direction from doppler change measurements
First Claim
1. Apparatus for measuring, from a moving observer, direction of arrival (DOA), including azimuth and elevation, of a continuous wave radar signal from a moving emitter using Doppler shift, comprising:
- an antenna for sensing the emitter radar signal,receiver means for measuring emitter carrier frequency over a predetermined dwell period,navigation signal means for measuring observer velocity, i.e., speed and heading during a dwell and providing corresponding output signals,observer control means for changing observer heading, speed or both between dwells or observer altitude during a dwell for establishing at least two linearally independent velocity vector differences,memory means for receiving outputs from said receiver means and said navigation signal means for storing three contiguous velocities measured during three contiguous dwells and the respective three measured emitter carrier frequencies,first computation means for taking the difference of the velocities and forming inverse coordinate basis vectors corresponding to these two unique velocity differences,first processor means for forming corresponding ratios of the carrier frequency measurements and forming basis set coefficients for two of said basis vectors,second processor means for deriving a normalizing coefficient for a third inverse coordinate basis vector so that the DOA unit vector is measured by equation 4 andsecond computation means for resolving the DOA unit vector in the system coordinates in which the emitter azimuth and elevation angles are defined and to compute the azimuth and elevation angle from the coefficients of the unit vector in those coordinates.
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Accused Products
Abstract
An electrical surveillance measures system for measuring direction of arrival (DOA), i.e., both azimuth and elevation, of a pulsed or continuous wave radar signal from a moving emitter. Either carrier frequency or pulse repetition interval (PARI) Doppler shift are used whereby the ratio of the Doppler shift is measured by a moving observer. The DOA is measured as a unit vector having basis vectors formed from a linearly independent set of observer'"'"'s velocity vectors. The DOA unit vector has a linear part where the coefficients of the basis vectors are derived directly from the ratios of frequency or PARI measurements taken in three contiguous dwells. The DOA unit vector has a nonlinear part formed from the requirement that the DOA vector have unit magnitude. The unit vector is resolved in the system coordinates in which emitter azimuth and elevation are defined to allow computation of the latter two values.
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Citations
4 Claims
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1. Apparatus for measuring, from a moving observer, direction of arrival (DOA), including azimuth and elevation, of a continuous wave radar signal from a moving emitter using Doppler shift, comprising:
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an antenna for sensing the emitter radar signal, receiver means for measuring emitter carrier frequency over a predetermined dwell period, navigation signal means for measuring observer velocity, i.e., speed and heading during a dwell and providing corresponding output signals, observer control means for changing observer heading, speed or both between dwells or observer altitude during a dwell for establishing at least two linearally independent velocity vector differences, memory means for receiving outputs from said receiver means and said navigation signal means for storing three contiguous velocities measured during three contiguous dwells and the respective three measured emitter carrier frequencies, first computation means for taking the difference of the velocities and forming inverse coordinate basis vectors corresponding to these two unique velocity differences, first processor means for forming corresponding ratios of the carrier frequency measurements and forming basis set coefficients for two of said basis vectors, second processor means for deriving a normalizing coefficient for a third inverse coordinate basis vector so that the DOA unit vector is measured by equation 4 and second computation means for resolving the DOA unit vector in the system coordinates in which the emitter azimuth and elevation angles are defined and to compute the azimuth and elevation angle from the coefficients of the unit vector in those coordinates. - View Dependent Claims (2, 3, 4)
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Specification