Acoustic wave processing and target detection

Sonar signal processing has significant and important contribution for intercepting, recognizing and clustering of active sonar in underwater environment. This paper describes an approach to real time detection and intercepting of underwater active sonar based on correlation and entropy. The use of correlation and entropy functions provide a good estimate of the location of target active sonar. For this purpose, we have used a surface array with four hydrophones. When the acoustic waves approach the sensors, at the first, they arrive to one or two of them and then arrive to the other sensors. Therefore there is a phase difference between received signals by sensors. Base on this, we have designed an algorithm based on correlation and entropy functions to detect the active targets. This method detects the frequency and the angle of the target active sonar. The angle is calculated in respect to positive direction of horizontal axis. This algorithm can compute other properties of received pings such as start time, end time and number of oscillations in a ping in each sensor.