Research on Information Transmission Technology Through the Water–Air Interface Combining a Sonar and a Radar

To realize the information transmission across the water–air interface, the radar has been used to detect the tiny surface perturbations caused by the underwater low-frequency sound source. Due to the differences of medium properties at the water–air interface, it is difficult for underwater targets to communicate with airborne platforms directly. To solve this problem, we propose the finite element method to establish the minute vibration model on the water surface caused by the underwater low-frequency sound source, and analyze the influence of sound source parameters on the tiny surface perturbations at the surface of water. Then we design the frame structure and synchronization signal of the single-carrier communication system, and propose a robust information transmission method across the water–air interface. Finally, we experimentally verify the information transmission method combining a low-frequency sonar and a millimeter-wave radar in an anechoic water tank. The experimental results show that the method we proposed can realize the information transmission across the water–air interface up to 500 b/s.