The Research Of Loop Antenna In Underwater Close Range RF Communication

Underwater wireless communication is very important for autonomous underwatervehicle(AUV) communication, underwater data collection, underwater informationexchange and underwater sensor networks. With the development of socity, offshoredevelopment also put the underwater wireless communication forward a higherrequirement. Because of the signal-to-noise ratio is small, low communication rate, largetime delay and multipath effect, underwater acoustic communication technology cannotachieve the ideal effect in the muddy, noisy neritic environments; The lasercommunication has also been restricted due to water high turbidity and the requirement ofperfect alignment.However, the transmission of electromagnetic wave is very smooth in the severeshort distance underwater environment. So, in this paper, we study the underwater RFcommunition in order to achieve a high speed and smooth communication in the closeunderwater environment.Firstly, this paper studies the transmission characteristics of plane electromagneticwave in the sea. We summarizes the relationship between the propagation velocity ofelectromagnetic field with wavelength and frequency with electrical conductivity throughtheoretical derivation. Moreover, electromagnetic field attenuation law and energycomposition is studied in the process of transmission.Secondly, the underwater electric dipole and magnetic dipole is fully analysised bothin theory and simulation. As the characteristics of the underwater is high conductivity andloss, underwater electric dipole and magnetic dipole’s radiation field was deduced. Also, itis concluded that the magnetic dipole is more suitable for underwater wireless RFcommunication through the radiation energy simulation of the two kinds of dipole.At last, we studied the wire diameter, number of turns, loop radius’ effect on theperformance of the loop antenna. Also, suitable antenna structure parameters is obtainedthrough optimizing the small loop antenna. On the basis of the antenna impedancematching, we used a digital signal generator and a oscillograph to conduct an underwaterradio frequency transmission experiment with the designed antenna, meanwhile, the electromagnetic decay was measured within2meter’s distance.