Distribution of the refracted electromagnetic field in air produced by the antenna in sea

Distribution characteristics of the refracted electromagnetic (EM) field in the air produced by the radiating source in the seawater play an important role in communication between seawater and air. In order to determine the distribution patterns, the EM wave propagation across the sea-to-air interface is investigated. Ray tube consisting of countless EM rays is modelled to analyse the power transmission across the interface. The distribution pattern in the vertical plane is obtained on the basis of energy conservation in the tube. The simulation results show that the field in air has obvious directivity. Moreover, without considering the attenuation of EM wave in seawater, the field intensity in air synchronously increases with frequency. In addition, the electric component in the far field presents the distribution of cosine which is not affected by the depth of the radiating source. Hence, it is concluded that the receiving location in air should be oriented right above the underwater radiating source to obtain optimum reception.