Method and apparatus for measuring the distance between two stations

Apparatus for measuring the distance between two continuous data link stations at least one of which is movable, comprising:

• a. a first carrier wave generator at said first station and including an input terminal for receiving the data to be transferred, and first and second output terminals,
• b. a first modulator having first and second input terminals and an output terminal, said first input terminal being connected with said first output terminal of said first carrier wave generator,
• c. a first antenna at said first station,
• d. first circulator means connected with said first antenna and including an input terminal connected with the output terminal of said first modulator, and an output terminal,
• e. a first mixer having a first input terminal connected with the output terminal of the first circulator means, a second input terminal connected with the second output terminal of the first carrier wave generator, and an output terminal,
• f. an IF amplifier including an input terminal connected with the output terminal of said first mixer, and first, second and third output terminals,
• g. detector and threshold circuit means including an input terminal connected with the first output terminal of said IF amplifier, and an output terminal,
• h. characteristic generator and timing circuit means including a first input terminal connected with the output terminal of said detector and threshold circuit means, a second input terminal connected with the second output terminal of said IF amplifier, and a first output terminal connected with the second input terminal of said first modulator,
• i. counter means having a first input terminal connected with the second output terminal of said characteristic generator and timing circuit, and second input terminal,
• j. time base generator means connected with the second input terminal of said counter means,
• k. a second carrier wave generator at said second station and including a data input terminal and first and second output terminals,
• l. a second modulator having a first input terminal connected with the first output terminal of said carrier wave generator, a second input terminal, and an output terminal,
• m. a second antenna at said second station,
• n. second circulator means connecting the output terminal of said second modulator with said second antenna, said second circulator means including an output terminal,
• o. a second mixer including a first input terminal connected with the output terminal of said second circulator means, a second input terminal connected with the second output terminal of said second carrier wave generator, and an output terminal,
• p. a second IF amplifier having an input terminal connected with the output terminal of said second mixer, and first and second output terminals,
• q. a second detector and threshold circuit having a first input terminal connected with the first output terminal of said second IF amplifier, a second input terminal, and first and second output terminals,
• r. characteristic decoder means including an input terminal connected with the first output terminal of said second detector and threshold circuit, a first output terminal connected with the second input terminal of said detector and threshold circuit, and a second output terminal, and
• s. gating means including first and second input terminals connected with the second output terminals of said detector and threshold circuit and said characteristic decoder means, respectively, and an output terminal connected with the second input terminal of said second modulator,
• t. said first modulator being operable to produce an interruption in the carrier wave generated by said first carrier wave generator and also a characteristic signal which occurs prior to the interruption, and
• u. the characteristic decoder and said second detector and threshold circuit being operable to detect said interruption and to introduce a corresponding interruption in the carrier wave of said second carrier wave generator, which second interruption is detected in said first detector and threshold circuit to afford a measure of the distance between said stations.