Acoustic positioning system and method

An acoustic positioning system comprising acoustic emission means (B1) and acoustic reception means (B2), the acoustic emission means comprising an acoustic emitter (B1) and an emitter clock, said acoustic emission means being configured so as to emit a sequence of at least one first acoustic signal S1 and one second acoustic signal S2 of same central acoustic frequency f, separated by a determined time interval T, said acoustic reception means comprising an acoustic receiver (B2) and a receiver clock, said acoustic reception means being operable to receive and to measure the phase of arrival φ1 of the first acoustic signal S1 and the phase of arrival φ2 of the second acoustic signal S2 on said acoustic receiver (B2), said phases of arrival φ1, φ2 being measured with respect to a reference oscillator,

• characterized in that:
• the emitter clock and the receiver clock are asynchronous,
• said system comprises means for measuring the relative radial displacement between said acoustic emitter (B1) and said acoustic receiver (B2), said measuring means comprising:
• auxiliary means for evaluating, with an accuracy of one half-wavelength, an estimation of the radial displacement (R2−R1)AUX between, on the one hand, the distance R1 travelled by the first acoustic signal S1 between said acoustic emitter (B1) and said acoustic receiver (B2), and on the other hand, the distance R2 travelled by the second acoustic signal S2 between said acoustic emitter (B1) and said acoustic receiver (B2),
• and means for calculating the relative displacement (R2−R1) between said acoustic emitter (B1) and said acoustic receiver (B2) as a function of the estimation of the radial displacement (R2−R1)AUX, of the time interval T and of the phases of arrival φ1, φ2, respectively, of the first acoustic signal S1 and of the second acoustic signal S2.