An Improved CLEAN Direct-Wave Suppression Algorithm in Integrated System of Underwater Detection and Communication

In this article, the direct-wave suppression problem is investigated based on the bistatic integrated system of underwater detection and communication (ISUDC). The bistatic ISUDC system has the advantages of saving space and reducing energy consumption. However, in the system, the direct wave and strong multipath are much stronger than the target echo signal, which brings difficulties in echo extraction and subsequent signal processing. Through system modeling, the received signal model of ISUDC signal after underwater multipath and channel fading is considered. An improved algorithm double window CLEAN (DW-CLEAN) algorithm is proposed based on the CLEAN algorithm. The algorithm utilizes the first layer of window shift to achieve the purpose of eliminating the effect of underwater multipath and the second layer of the window is used to achieve the signal frequency and time correlation reduction. In order to achieve almost constant amplitude and time delay for each signal segment, the effect of time variation of direct wave on direct-wave reconstruction is minimized. Finally, the windowed ISUDC signal is reconstructed by the CLEAN algorithm on the direct-wave signal to obtain the echo signal. The experimental analysis shows that the algorithm has convergence and stability, can effectively suppress the direct wave and strong multipath interference, and eliminates the influence of the time-varying instantaneous frequency of the ISUDC waveform on the direct-wave estimation. Thus, a more complete echo signal and better processing performance are obtained.

I. Introduction

The bistatic-related problem has been an active research direction for many years and has a wide range of applications in the fields of navigation, radar, and sonar [1], [2], [3], [4], [5], [6]. At the same time, in existing underwater systems, communication and detection systems are generally built independently. This can result in system platforms that are large and easy to detect [7]. If the integrated system of underwater detection and communication (ISUDC) technology is applied to a bistatic sonar system, ISUDC enables the bistatic to have both detection and communication functions, which can reduce the required volume of the node. This reduces the platform energy consumption and reflective area, increases concealment performance, and improves the safety of underwater bistatic platforms [8]. Because communication and underwater detection have certain similarities in the working principle, system structure, signal frequency, hardware system, and so on. Therefore, it is feasible to combine the two and apply them in a bistatic system to form a bistatic ISUDC system [8], [9], [10].