Study On Electromagnetic Characters Of Ship Under HEMP Radiations

High altitude electromagnetic pulse contains high energy in large areas of thousands ofkilometers which can couple into the electronic systems through various channels.It is aserious threat to electronic systems.Modern ships equiped various electric systems andequipments,therefore,it is essential to research on the electromagnetic characters of ship underHEMP radiation.Firstly,this paper first introduced the generation mechanism and the main features ofHEMP.It gave several waveform representation standards.Then studied the equivalent methodof HEMP source.This paper used a frequency domain method,which is to change the timedomain waveform into frequency domain by fourier transform,and analyzed in frequencydomain.This paper designed an pyramidal horn antenna as an equivalent HEMP source toradiate to the ship.By comparing with several computing methods of electromagnetic,we got the bestmethod to compute the electromagnetic environment of ship whose electric size is muchlarger.The method was to combinate the physical optics and physical theory ofdiffraction.When researching by the software of Ship EDF,we used the equivalent HEMPsource to radiate on the ship.Then we studyed the electromagnetic characters of the shipradiated under HEMP by the methods introduced above.In oder to study the impacts of thespecific structures of ship to the electromagnetic characters of the ship,this paper reasearchedthree cases respectively which are the ship without the mast,the ship neither have the mast norpart of superstructure and the whole ship.To study the impacts of the radiation direction to theelectromagnetic characters of ship,this paper selected two representation radiation directionswhich are the vertical direction and the oblique direction of45degree.It can be seen from the simulation results that with the increasing of the ship structureslayer by layer,the complexity of the ship structure increases.Meanwhile the electromagneticenvironment surrounding the ship also will be more and more complex.It due to scatteredfields,such as the reflection and diffraction fields.The electric fields are more strength near themast and the superstructure of the ship,and its distribution is uneven.While in the mordenship,the complex and diverse electric equipments are often concentrated in the mast andsuperstructure.Therefor,the reaserch has a certain reference value for HEMP protection.