A multistatic network of autonomous active sonar transmitters and receivers, such as the DUSS (Deployable Underwater Surveillance Systems) currently being studied at the NATO SACLANT Center, often provides multiple contacts of the same target. The present paper examines the effects of receiver diversity ("spatial diversity") on a multistatic system, where three independent, spatially separated sonar receivers detect the same target, insonified by the same FM or CW pulse, and the contacts are merged together after detection.Real data collected South-East of the island of Elba (Italy), during "DUSS'97" tests with SACLANTCEN's experimental system are analyzed. The statistical characteristics of measured background noise and reverberation are estimated. Signal to Noise Ratio(SN R) series of echoes from a towed Echo Repeater are analyzed and decomposed into slowly varying and rapidly varying components. The degree of inter-receiver cross-correlation is estimated and related to the corresponding overall detection performanceof the multistatic system. Experimental distributions of detections and false contacts are computed, and experimental Pd -Pfa (Probability of detection Probability of false alarm) curves are extracted. Receiver Operating Characteristic (ROC) curves areproduced with Monte Carlo simulations of a classical statistical model and adopted as a reference.
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