Motion-compensated direction finding system
First Claim
1. A motion-compensated direction of source of electromagnetic radiation finding system, comprising:
- antenna means having a three-dimensional response pattern fixedly mounted to a platform body which undergoes motion, said antenna means defining a first three-dimensional frame of reference which undergoes the same motion as the platform body, said antenna means in response to presence of a radiation source providing a first signal representative of the apparent direction of arrival of radiation incident to the antenna means with respect to the first frame of reference;
three-axis inertial reference means which is carried by said platform body, said three-axis inertial reference means defining a second three-dimensional frame of reference which is at rest with respect to inertial space irrespective of the motion of the platform body, said three-axis inertial reference means being operative to provide a second signal representative of the orientation of the first frame of reference with respect to at rest inertial space; and
spatial angle estimator means coupled to the antenna means and to the three-axis inertial reference means, said spatial angle estimator means including a plurality of empirically pre-obtained reference models of the three-dimensional response pattern of said antenna means respectively due to radiation received along selected different three-dimensional angles of radiation incidence to the antenna means, said spatial angle estimator means being responsive to the plurality of reference models, the first signal, and second signal to provide a third signal representative of the true direction of arrival of said radiation incident to said antenna means with respect to at rest inertial space.
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Abstract
The improved direction finder of the instant invention has three orthogonal antenna elements or an array of antenna elements consisting of antennas in three dimensions. Amplitude and phase difference measurements are made on various combinations of antennas, and they are compared to a data base of antenna relationships that correspond to three dimensional angles. The spacial angle of arrival of electromagnetic signals are determined by the fit between the measured parameters and the stored relationships. This apparent direction of arrival is compensated for any motion of the antenna by an error signal representative of antenna motion with respect to inertial space. The apparent direction of arrival is thereby compensated to provide true direction of arrival determinations. The motion compensated direction finding system of the invention has especial utility for buoys released from undersea vessels released to sea surface.
6 Citations
13 Claims
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1. A motion-compensated direction of source of electromagnetic radiation finding system, comprising:
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antenna means having a three-dimensional response pattern fixedly mounted to a platform body which undergoes motion, said antenna means defining a first three-dimensional frame of reference which undergoes the same motion as the platform body, said antenna means in response to presence of a radiation source providing a first signal representative of the apparent direction of arrival of radiation incident to the antenna means with respect to the first frame of reference; three-axis inertial reference means which is carried by said platform body, said three-axis inertial reference means defining a second three-dimensional frame of reference which is at rest with respect to inertial space irrespective of the motion of the platform body, said three-axis inertial reference means being operative to provide a second signal representative of the orientation of the first frame of reference with respect to at rest inertial space; and spatial angle estimator means coupled to the antenna means and to the three-axis inertial reference means, said spatial angle estimator means including a plurality of empirically pre-obtained reference models of the three-dimensional response pattern of said antenna means respectively due to radiation received along selected different three-dimensional angles of radiation incidence to the antenna means, said spatial angle estimator means being responsive to the plurality of reference models, the first signal, and second signal to provide a third signal representative of the true direction of arrival of said radiation incident to said antenna means with respect to at rest inertial space. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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Specification