Directional bionic underwater communication method using a parametric acoustic array and recursive filtering

Abstract

This paper presents a bionic method for directional covert underwater communication using a parametric acoustic array. This technique can improve the concealment of communication and reduce the probability of its interception, combining the advantages of an underwater parametric acoustic array (low frequency, high directivity, and small size) and marine biological acoustics. Achieving appropriate pre-modulation of the excitation signal is the core of communication with a parametric array due to the nonlinear physical process of self-demodulation. To solve this problem, this the state equation and observation equation are constructed based on the Berktay equation of the parametric matrix, and a recursive Kalman filter modulation method is proposed to approach distortion-free transmission. The algorithm has low computational complexity and is conducive to real-time modulation. More importantly, it can suppress noise in the input signal and reduce its impact on the modulation effect. Using this method, a dolphin whistle signal is transmitted by the parametric array as the symbol for a pattern time delay difference system, which achieves the intended purpose of enhancing the concealment of the communication. The results from simulations and pool experiments show that the system is effective and feasible.