STATISTIC PROPERTIES OF THE NOISE FIELD OF MOVING SOURCE IN SHALLOW WATER AND ITS EFFECTS ON SIGNAL ROCESSING FOR THE NOISE RANGING SONAR

In this paper the properties of space-time correlation function of the noise field of moving source in layered statistic inhomogeneous medium are studied and the effects of random fluctuating boundary are considered as well.
It has been shown, theoretically and experimentally multi-path propagating effects cause the dispersion of the correlation function and fluctuations of the medium refraction index and the boundary cause the fluctuation of it.
The effect of the movement of the noise source on the output of real-time correlator is equivalent to a low-pass filter added the drift of space-time correlation function.
These properties of the correlation function cause grave degradation of the signal processing gain of noise ranging sonar system.
The fluctuation and the distortion of correlation function made it difficult to realize the noise ranging. So, in this paper, a method of space correlation ranging by a linear array of four points with short separation and long span and a technique of dual-correlation signal processing are presented by this, the influences of preveiously mentioned factors are greatly overcomed.
Futhermore, for the long period and large delay fluctuation of the dualcrrelation function output caused by internal wave, a method of limited memory quasi-Kalman filtering is developed and the effective accurate ranging and tracing of noise ranging sonar are able to be realized finally.