Super short baseline navigation using phase-delay processing of spread-spectrum-coded reply signals

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.