Theoretical Analysis of Low Frequency Electromagnetic Signal Propagation in Shallow Seas

Acoustic waves methodologies for the purpose of underwater communication are inherently band limited and suffer from data corruption in shallow water. These shortcomings lead to the use of low frequency electromagnetic (EM) waves while it also suffer frequency dependent attenuation in electrically conductive seawater. An enhancement in range and data rate can be achieved by two physical configurations of transmitter and receiver in a communication system: 1) allow EM signals to cross seawater-to-air boundary and achieve long-range horizontal communication using air path, followed by air to water signal transmission, if needed, and 2) explore guided waves phenomenon at the water side of the seawater-air interface. In this paper, we perform theoretical/computational investigation of EM wave propagation characteristics in order to determine the antenna orientation dependent optimum frequencies and ranges on both sides of the interface, within a thin layer. It is shown that guided wave effect can be exploited to transmit electric field to a distance of 1 km at 10 KHz, with approximately 80 dB loss of signal strength.