Research On Apeture EMI For The Predication Of Automotive EMC Based On Antenna Theory

With the development of automotive industry and application of electronic technology on automotive, automotive is going into the electronic era from the traditional era of mechanization. How to solve the automotive electronic equipment electromagnetic compatibility problems, improve the reliability and security,ensure that the moving vehicle will not interfere with the normal operation of equipment around,and at the same time,it won't be interfered by the surrounding electromagnetic environment,this has become a very important and urgent research topic.This paper introduces the electromagnetic environment of automotive,and also describes vehicle's interference sources and external electromagnetic interference of vehicle;besides,it also introduces electromagnetic compatibility standards on the vehicle.Automotive electromagnetic interference ,wether internal or external,has great impact on electronic equipment of vehicles,particularly on vehicles'ECU (electronic control unit).These electromagnetic interference has serious implications on the work of automotive electronic equipment performance.Therefore,in order to prevent anomalies occuring and allow automotive electronic equipment to work normally in such circumstances,it need require to use anti-interference measures in modern cars to ensure the normal work of vehicles using electronic equipment.Eliminating interference source is the basic anti-interfering technology,and preventing string of signal interference is another way.The occurrence process of any electromagnetic interference (EMI) follows three elements of the principle of law and is a function of azimuth.Therefore,the process can be described by the mathematical model.The electromagnetic interference is affected by many factors.When building a mathematical model,we will often take an intermediate value,as a valve value.If the value of this interference is below intermediate value,the sensitive equipment will not be seriously disrupted and it is compatible with the situation.Because there are many apertures in automotives,in a certain extent,these apertures are the equivalent of the antenna.The field source in automotives interferes some of the equipment of the outside through the apertures,and the outside does the same.What we have to do is to calculate the outside interference of the main field source of cars through the aperture.We consider the apertures as antennas,that is the secondary source of transmission antennas.In a closed system,because of the shielding effect of electromagnetic waves of the metal shell,the electromagnetic radiation energy of outside interference sources rarely penetrates into the system.But the doors and windows in a closed shell,other openings discontinuous will have more serious leakage of electromagnetic waves,so it could cause the deterioration of local electromagnetic environment in the shell. This field through aperture leakage and wire inductively coupled comes into the equipment and causes harm.EMC forecast programming software using Matlab and VC++ hybrid programming achieve the required functionality.In the functional implementation ,it can be divided into several major modules.Matlab has wide applications in scientific experiments,mainly due to its simplicity and interpretative language,the source code's beeing modified and powerful graphics capabilities.Realization of the function of software modules depends on the exchange of Matlab and VC++ function. Calculation is mainly finished by Matlab.Interface structures are mainly completed by VC++.This provides a great deal of flexibility for the realization of programming. The main effects of shielding effectiveness are the thickness of shielding,magnetic conductivity,etc.This paper introduces the impact on the shielding effectiveness of thickness,permeability rate,and the rule aperture,and calculates the field through holes by mathematical modeling.We compare shielding effectiveness of the four rule aperture and aperture array.At last,we draw the best design.In actual measurement experiment,we build corresponding model for the typical source of tinder system of automotive and analyse the electromagnetic radiation of vehicles through apertures.We obtain experimental data through scanning the whole vehicles,have corresponding images and certificate conclusions correctness from the theory finally.In conclusion,the paper analyses and calculates the impact of automotive electromagnetic shielding effectiveness about aperture shapes,numbers and array,put forwards a specific proposal,certificates good shielding effectiveness through the experiment,and so it enhances the automotive's Electromagnetic Compatibility.