Patent ID: 8908475

Claim:
An acoustic positioning system comprising: acoustic emission means (B 1 ); and acoustic reception means (B 2 ); wherein the acoustic emission means comprises an acoustic emitter (B 1 ) and an emitter clock, said acoustic emission means being configured so as to emit a sequence of at least one first acoustic signal S 1 and one second acoustic signal S 2 of same central acoustic frequency f, separated by a determined time interval T, said acoustic reception means comprising an acoustic receiver (B 2 ) and a receiver clock, said acoustic reception means being operable to receive and to measure the phase of arrival φ 1 of the first acoustic signal S 1 and the phase of arrival φ 2 of the second acoustic signal S 2 on said acoustic receiver (B 2 ), said phases of arrival φ 1 , φ 2 being measured with respect to a reference oscillator; and wherein: the emitter clock and the receiver clock are asynchronous, said system comprises means for measuring the relative radial displacement between said acoustic emitter (B 1 ) and said acoustic receiver (B 2 ), said measuring means comprising: auxiliary means for evaluating, with an accuracy of one half-wavelength, an estimation of the radial displacement (R 2 −R 1 ) AUX between, on the one hand, the distance R 1 traveled by the first acoustic signal S 1 between said acoustic emitter (B 1 ) and said acoustic receiver (B 2 ), and on the other hand, the distance R 2 traveled by the second acoustic signal S 2 between said acoustic emitter (B 1 ) and said acoustic receiver (B 2 ); and means for calculating the relative displacement (R 2 −R 1 ) between said acoustic emitter (B 1 ) and said acoustic receiver (B 2 ) as a function of the estimation of the radial displacement (R 2 −R 1 ) AUX , of the time interval T and of the phases of arrival φ 1 , φ 2 , respectively, of the first acoustic signal S 1 and of the second acoustic signal S 2 .