Abstract
Passive sonar is widely used for target detection, identification and classification based on the target radiated acoustic signal. Under the influence of Doppler, generated by relative motion between the moving target and the sonar array, the received ship-radiated acoustic signals are non-stationary and time-varying, which has a negative effect on target detection and other fields. In order to reduce the influence of Doppler and improve the performance of target detection, a coherent integration method based on cross-power spectrum is proposed in this paper. It can be concluded that the frequency shift and phase change in the cross-power spectrum obtained by each pair of data segments can be corrected with the compensations of time scale (Doppler) factor and time delay. Moreover, the time scale factor and time delay can be estimated from the amplitude and phase of the original cross-power spectrum, respectively. Therefore, coherent integration can be implemented with the compensated cross-power spectra. Simulation and experimental data processing results show that the proposed method can provide sufficient processing gains and effectively extract the discrete spectra for the detection of moving targets.
Highlights
Sonar can be regarded as a kind of underwater radar, using sound to interrogate the surroundings
Time scale factor and b j2π f time delay estimated by any method can be used for the compensations of the cross‐power spectrum i source at f0 in the cross-power spectrum Pr12i ( f ) can be compensated by multiplying by e according to the operations illustrated in the dashed rectangles of Figure 2
The passive sonar array was deployed at a depth of 170 m and evaluations are based on the estimation outcomes
Summary
Sonar (sound navigation and ranging) can be regarded as a kind of underwater radar, using sound to interrogate the surroundings. Passive sonar only includes a receiver without a transmitter and is used to detect the sound emitted by the target, which has the advantages of high concealment and a long detection distance. In the common scenario of passive target detection shown, the Doppler phenomenon, caused by relative motion between the sonar array and the moving target, can give rise to the distortion of received signals. Under the influence of Doppler, the received acoustic signals become non-stationary and time-varying. If the detection or localization of the moving target is operated by methods based on stationary signal hypothesis, the estimated results will definitely deviate from the true values.
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