Spatial Gain Analysis for Vertical Linear Array in the Direct-Arrival Zone

Abstract

The array gain is a key parameter to evaluate the detective performance of the vertical linear array. A method is developed in this paper to calculate the spatial gain of the vertical array when the plane-wave assumption is not applicable and the oceanic ambient noises are not incoherent. If applying correspond phase compensation to the received signals according to the output of the conventional beamformer, then we can achieve the optimal array gain based on the developed formula. The proposed optimal array gain can describe the vertical array’s performance and guide the deployment of it effectively. The spatial gains with different array locations are simulated and analyzed based on the sound propagation properties of the direct-arrival zone using the ray theory. In the direct-arrival zone, the acoustic field is mainly composed of the direct ray and the surface-reflected ray, and it is found that the optimal array gain is high in most space of the zone except the region near bottom or the locations where the destructive interference appears. The proposed method of gain analysis is well consistent with the physical properties of deep water. The theory and simulation are tested by experimental data.