Comparison of Real-time Implementation of Conventional and Adaptive Triplet Array Beamforming Algorithms for Pulsed Active Sources

A triplet array has the capability to reduce the port/starboard ambiguity that strongly affects detection and localization in the case of a linear array. When searching for a target near a high clutter area (e.g., a rocky shore near a cliff), this feature can be crucial for detection. The most computationally intensive part of the detection and localization process is the beamforming. This work describes three beamforming algorithms that have been implemented at NATO STO-CMRE for real-time signal processing on board an Autonomous Underwater Veicle (AUV) towing a triplet array: a conventional cardioid beamformer, a 3D cardioid beamformer and an adaptive beaformer. The three algorithms are compared in terms of run-time and memory usage, parameters that are particularly important as the array is intended to be used on an AUV with limited computational power. Other criteria for comparison evaluated in this work are the spatial resolution and the Port/Starboard Rejection. The algorithms are evaluated against a data set collected during the LCAS16 sea trial (off the coast of Taranto, Italy) and the LCAS18 sea trial (off the northern cost of Elba). The results, in term of accuracy, spatial resolution, Port/Starboard Amplitude Rejection (PSAR), computation time and memory usage, are given for the three algorithms.