The invention provides a dual-frequency phase-comparison
underwater acoustic
ranging method, which comprises the following steps that: step 1, a
sonar transmitter transmits a dual-frequency
continuous wave signal to a target, and a
sonar receiver receives a target echo; 2, for one frame of data of the target echo, two line spectrum peak values with the
maximum amplitude and the second
maximum amplitude in a power spectrum are searched, and a
frequency difference is obtained; according to the
frequency difference range and the amplitude threshold, carrying out availability confirmation on the two line spectrum peak values; and 3, comparing phases corresponding to peak points of the peak values of the two line spectrums, and determining a target distance of the current frame through a
phase difference. According to the method, the
continuous wave system sonar is matched with the multi-frequency phase comparison technology for target
distance measurement, the precision of phase measurement is higher than that of time
delay measurement, and the sensitivity of the
phase difference of double-frequency signals to
random noise is low, so that the influence of a multi-path effect and
noise can be effectively reduced, and the accuracy and reliability of
distance measurement are remarkably improved.