Super short baseline navigation using phase-delay processing of spread-spectrum-coded reply signals
First Claim
1. A navigation system employing real-time estimation of the positions of multiple cooperative targets, comprising:
- transmitter means for transmitting an interrogation signal for detection by a plurality of transponders or responders each of which, responsive to detection of the interrogation signal, transmits a reply signal having at least one continuous wave frequency component;
first receiver means comprising a plurality of receiving elements spaced apart a distance in the range of 0.5 to 10 wavelengths of the lowest frequency component of the reply signals, said first receiver means comprising direction-of-arrival measurement means including means for measuring the phase difference of the received reply signal between each pair of receiving elements and producing direction-of-arrival estimates, whereby said first receiver means includes spectral and spatial means to resolve ambiguities;
second receiver means for the measurement of round-trip travel times providing distance-to-target estimates for each target; and
computer means for collecting the outputs to said first and second receiver means for determining the position of each target relative to said receiving elements.
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Abstract
A short baseline navigation system employs the real-time estimation of the positions of multiple cooperative targets. Each target replies with a unique stepped frequency sequence signal that covers the usable frequency band. A processor operates on reply signals received by elements on the tracking platform and develops a coarse time-difference-of-arrival estimate using an algorithm derived herein. The processor also estimates the Doppler shift of received signals, and determines a time-window (or gating) that eliminates the portions of the received signals corrupted by multipath interference. The relative phase differences between the received signals are then used in conjunction with the coarse time-difference-of-arrival estimates for a precise direction-of-arrival estimation.
52 Citations
13 Claims
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1. A navigation system employing real-time estimation of the positions of multiple cooperative targets, comprising:
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transmitter means for transmitting an interrogation signal for detection by a plurality of transponders or responders each of which, responsive to detection of the interrogation signal, transmits a reply signal having at least one continuous wave frequency component; first receiver means comprising a plurality of receiving elements spaced apart a distance in the range of 0.5 to 10 wavelengths of the lowest frequency component of the reply signals, said first receiver means comprising direction-of-arrival measurement means including means for measuring the phase difference of the received reply signal between each pair of receiving elements and producing direction-of-arrival estimates, whereby said first receiver means includes spectral and spatial means to resolve ambiguities; second receiver means for the measurement of round-trip travel times providing distance-to-target estimates for each target; and computer means for collecting the outputs to said first and second receiver means for determining the position of each target relative to said receiving elements. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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Specification