Title: Acoustic transponder navigation system

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Abstract: 1. In combination in an acoustic obstacle detection and navigating system; A transmitting station comprising a variable frequency oscillator, a sawth generator coupled to said oscillator for sweeping the frequency of oscillations through the range of frequencies from f.sub.1 to f.sub.2, a submersible projection transducer coupled to said oscillator for continuously ensonifying a sector of water about said transducer with sonic energy varying between f.sub.1 and f.sub.2, A fixed frequency oscillator of frequency f.sub.3 at said station, A sonar receiver at said station including a mixer for combining the frequencies f.sub.1 to f.sub.2 of said oscillator with the echo frequencies reflected from a passive target, so that the difference at any instant between the reflected frequency and the transmitted frequency is a frequency proportional to the rate of change of said variable frequency and target range, A remote transponder station including a receiving hydrophone coupled to a transmitting transducer, a mixer coupled between said hydrophone and transmitting transducer, a local oscillator of fixed frequency, f.sub.3, coupled to said mixer for shifting received frequencies from the range of f .sub.1 to f.sub.2, to the range of f.sub.1 + f.sub.3 to f.sub.2 + f.sub.3, and A second receiver at said transmitting station including a mixer for combining signals repeated from said remote transponder with the frequencies, f.sub.1 to f.sub.2 of said variable oscillator displaced by the frequency f.sub.3, of said fixed frequency oscillator, and a common display for both mentioned receivers.


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