Experimental demonstration of forward scattering barrier for AUV intruder

The active detection of autonomous underwater vehicles (AUVs) is a challenging task because the echoes from targets are seriously weak under a monostatic configuration. In this work, a forward scattering detection scheme was developed for the active sensing of AUV intruders. A linear frequency modulation pulse was transmitted periodically for the acquisition of multipath propagation responses in a harbor environment. The least mean square algorithm after matched filtering was employed for direct blast suppression. A cumulative index was defined for detection on the basis of the error sequence of the adaptive filter. Sea experiments using an AUV as an intruder in crossing events were conducted to demonstrate the ability of the proposed scheme. The time of each crossing event was determined. The detection scheme was found to have a detection capability with a low source level. The performance was determined by the signal-to-direct blast ratio, which was correlated with the source–target–receiver geometry.