Study Of The Emc Of A Transmitter Antenna And A Radio Tactical Vehicle

In the recent years,the advance in the telecommunication systems in the automotive,aviation,space,and maritime sectors and the increase of the awareness of the electromagnetic interference and compatibility(EMI/EMC)lead to an extraordinary focus on developing numerical methods in computational electromagnetics(CEM)that can accurately model a wide range of electromagnetic systems with taking into account the variety of environments in which they operate.Thus,a number of methods have been developed,such as the Method of Moments(MoM),the Finite Element Method(FEM),and the Finite-Difference-Time-Domain(FDTD),each of which exhibits their own advantages and disadvantages.In particular,the FDTD has become a widely used tool for modeling electromagnetic systems,and since it solves Maxwell's equations directly and it experiences little difficulties when handling complex inhomogeneous media.In addition,the FDTD is more adapted for the parallel computing;hence,it can model large systems using supercomputing clusters.However,the FDTD presents its inconveniences used for the simulation of problems for which the domain size is extremely large in terms of the operating wavelengths,whereas many of the studied objects have fine features.The FDTD requires the entire meshing of the computational space,then the presence of fine features increases the needed computational resources.This served as the motivation of the effectuated works in this thesis to developed multi-scale method that can overcome these computational problems.As an example of the multi-scale electromagnetic problem,we consider in this thesis the case of a radio-transmission military vehicle.A large antenna fed with high power is installed upon the vehicle.Two scenarios are considered:(1)the study of the interference between the mounted antenna and the onboard subsystems;(2)the effects of the quantification of the undesired effects of the electromagnetic radiation of the human bodies of the crew inside the vehicle,with the aim of complying with the international standards for the Control of Electromagnetic Interference Characteristics of Subsystems and Equipment and the health protection regarding personnel exposure to the electromagnetic radiation in the military workspaces.Many multi-scale problems have been investigated in this thesis including:(1)The coupling between the two antennas on the complex platform.One is a bulky antenna installed upon the vehicle and the second is a small antenna that needs fine resolution to be modeled;(2)The undesired effects of the antennas radiations on the existent human bodies in the working area,through the rigorous modeling of these human bodies;(3)Taking into consideration the dispersive characteristic of the human tissue regarding the frequency band of interest;(4)The efficient modeling of fine features in the FDTD method and the introduction of a new multi-scale method;A Four-Pole Debye model is used to model the human tissues.And a new high order staggered FDTD is developed.The proposed method falls within the Auxiliary Differential Equation FDTD methods.It is based on the use of the high order backward finite differentiation for the approximation of the time auxiliary derivatives and the use of high order central finite difference for the approximation of the spatial derivatives.The proposed method proves its efficiency regarding the precision in the for low-resolution meshes.The stability of the proposed method is analyzed for the free space,non-dispersive,and dispersive media.A new Double Grid FDTD is proposed in this thesis.The method is based on using a coarse grid for modeling large elements and a fine grid to model the fine features.The coupling between the two grids is insured by means of the Huygens equivalent currents.The proposed technique is independent on the FDTD scheme.Therefore,the hybridization of deferent methods is possible.A hybrid FDTD is used for the simulation of the scenario of the interference between two antennas,and the scenario of the exposure of the human body to radiation from a large antenna.Finally,for the purpose of validation,the developed dispersive FDTD method is compared with the electromagnetic analytic solution of well-known problems.For the Double-Grid method,a full wave simulation by using a fine grid all over the computational space used as a reference.The results of the proposed techniques are compared the those of the already existing methods.