Passive means for single site radio location
First Claim
1. A method of measuring the geographical location of a remote transmitter from a single receiver-site comprising the following steps:
- (a) providing an array of signal sensors wherein the sensors are spatially separated to obtain a finite intersensor propagation delay time for transmitted signals incident upon the array and transmitted from a remote transmitter;
(b) obtaining sampled signals from substantially simultaneous measurements of transmitted signals received at the sensory array;
(c) determining the discrete Fourier transform (DFT) for the sampled signal at each sensor;
(d) considering the sensors in pairs and computing a normalized cross power spectrum using DFT for the sample signal acquired at each individual sensor;
(e) identifying the frequency bins of the normalized cross power spectrum which have magnitudes near unity;
(f) using the frequency bins of the normalized cross power spectrum which have magnitudes near unity to compute a spectral cross correlation matrix;
(g) determining by matrix evaluation the rank of said spectrum cross correlation matrix, eliminating a number of columns from the leftmost portion of the matrix equal to the rank of the spectral cross correlation matrix with the remaining matrix being a matrix representative of nullspace;
(h) forming the eigen spectrum using the nullspace matrix and a sensor array steering vector;
(i) searching for the maximum of said eigen spectrum which will result in an estimate of the intersensor and interpath delay times; and
(j) computing the geographic location of the remote transmitter using the intersensor and interpath delay time.
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Abstract
The invention described herein relates generally to the field of direction finding and source location. The invention has broad application in areas requiring superresolution spectral analysis. The invention described in the context of any array processing problem in which the location of a transmitter is to be determined at a single receiving site based on passive measurements of the propagation waveform. The invention exploits the information received by a pair of sensors to extract intersensor delay and interpath delay times in the presence of multipath propagation. Two sensors are used in order to normalize the effects of signal modulation. Combining the sensor pairs in groups, the direction-of-arrival may be determined for each signal from the intersensor delay times thus derived. The invention additionally provides for the estimation of transmitter location by using the intersensor and interpath delay times. The invention is applicable in the context of array data processing to a number of areas including sonar, broadcast, communication, radar and satellite signal formats.
76 Citations
10 Claims
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1. A method of measuring the geographical location of a remote transmitter from a single receiver-site comprising the following steps:
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(a) providing an array of signal sensors wherein the sensors are spatially separated to obtain a finite intersensor propagation delay time for transmitted signals incident upon the array and transmitted from a remote transmitter; (b) obtaining sampled signals from substantially simultaneous measurements of transmitted signals received at the sensory array; (c) determining the discrete Fourier transform (DFT) for the sampled signal at each sensor; (d) considering the sensors in pairs and computing a normalized cross power spectrum using DFT for the sample signal acquired at each individual sensor; (e) identifying the frequency bins of the normalized cross power spectrum which have magnitudes near unity; (f) using the frequency bins of the normalized cross power spectrum which have magnitudes near unity to compute a spectral cross correlation matrix; (g) determining by matrix evaluation the rank of said spectrum cross correlation matrix, eliminating a number of columns from the leftmost portion of the matrix equal to the rank of the spectral cross correlation matrix with the remaining matrix being a matrix representative of nullspace; (h) forming the eigen spectrum using the nullspace matrix and a sensor array steering vector; (i) searching for the maximum of said eigen spectrum which will result in an estimate of the intersensor and interpath delay times; and (j) computing the geographic location of the remote transmitter using the intersensor and interpath delay time. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of determining the location of a remote transmitter as indicated by azimuth and range to said transmitter measured from a receiving antenna array site, which comprises the steps of:
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(a) determining at an antenna site the intersensor and interpath delay times of a signal transmitted from a remote transmitter; (b) computing the azimuth AOA from the ground wave signal path using the intersensor and interpath delay times; (c) computing the azimuth AOA of the skywave signal path using the intersensor and interpath delay times; (d) determining the skywave reflection height from an ionospheric sounding; (e) computing the ground range to the remote transmitter by combining said computed AOA of the skywave and said skywave reflection height; (f) computing the azimuth of the remote transmitter using said computed groundwave AOA, said groundwave signal path and said skywave signal path; and (g) determining the geographical location of the remote transmitter by combining the ground range and said azimuth of said remote transmitter.
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Specification