This work addresses the problem of Port-Starboard (PS) beamforming for low-frequency active sonar (LFAS) with a triplet receiver array.

The work presents a new algorithm for sub-bands beam-space adaptive beamforming with twist compensation and evaluates its performance with experimental data collected at sea.

The results show that the algorithm provides the ability to solve the PS ambiguity with a strong PS rejection even at end-fire where ordinary triplet beamformers have poor performance, allowing to unmask targets in the presence of strong coastal reverberation and/or traffic noise.