0 Preface
With the continuous development of electronic technology, more and more new technologies are applied to the automotive field, so each electronic device and electronic control system must adapt to each other, which is the electromagnetic compatibility (EMC) requirements. To ensure automotive reliability, designers must analyze electromagnetic compatibility issues at an early design stage. At present, some electromagnetic compatibility analysis software has been launched on the market, which can help engineers complete the electromagnetic compatibility design of automobiles.
According to the applicability of the software, the electromagnetic compatibility analysis software launched on the market can be divided into two categories: board-level electromagnetic compatibility analysis software and system-level electromagnetic compatibility analysis software.
Automotive electronics belongs to the system-level electromagnetic compatibility analysis. The applicable software is: EMC studio, HFSS, FEKO, EMC2000, FLO / EMC, PAM-CEM.
Electromagnetic compatibility analysis of automotive electronics refers to the determination of the interference path and coupling method from the analysis of the characteristics and technical parameters of various interference sources according to the specific technical parameters of the vehicle and the actual applicable environment of the vehicle during the overall design of the automotive electrical circuit. , And then take various measures to suppress the interference, eliminate the coupling of the interference, and enhance the anti-interference ability of the interfered object, so that the automotive electronic products and equipment work normally. In most cases, EMC in automobiles depends mainly on: metal car body, connecting cable, electronic control unit (ECU) and electronic components, antenna.
By accurately simulating the points listed above and selecting appropriate calculation methods, it is possible to make accurate predictions for EMC.
1 Necessary tools for calculating auto parts
The necessary tools for calculating auto parts are: (1) a program for calculating the 3D electromagnetic field: solving the Maxwell equations, considering the body structure / testing device; (2) a transmission line calculation program: the solution for the transmission line equation, considering that the external field affects the interior of the system (3) Circuit calculation program: calculation of circuit equations, considering the influence of complex loads.
2Comparison of calculation methods
(1) The advantages of the electromagnetic field calculation program MOM are: the scattering of the field takes into account the true three-dimensional geometry; the limitations are: it cannot be used to calculate customized cable packages, it is impossible to consider complex currents with nonlinear end junction devices, It is difficult to handle insulating and magnetic materials; accuracy depends on the quality of the grid.
(2) The advantages of the transmission line calculation program MTL are: frequency depends on the cable parameters considered, three independent components: source, cable and load, and high calculation speed; the limitation is: the transmission line calculation cannot consider any three-dimensional geometric structure, It is only close to the real three-dimensional situation; the accuracy depends on the calculation of LC parameters and the longitudinal segmentation accuracy along the direction of the metal line.
(3) The advantages of the circuit calculation program (SPICE) are: complex circuits, time-domain calculations, and simple nonlinear descriptions; the defects are: the program cannot guide EMC problems, the dilemma of electromagnetic fields, and the stability of large systems; accuracy: use When the model is accurate, the accuracy is very high, and there are very few accurate models.
(4) Hybrid method
Combination of different methods: concentrate advantages and discard defects.
â‘ The 3D EM program + transmission line calculation program directly calculates the electromagnetic field with a three-dimensional electromagnetic solver when there is no metal wire, and the field uses a transmission line excitation source.
â‘¡ Transmission line calculation program + circuit calculation program The transmission line system is subdivided into small segments, and each line segment is a current model with lumped parameters.
Under such a method, a circuit analysis tool (SPICE) can be used for the load device (including non-linear).
3 build the model
Establishing the correct model is the key to solving the problem of automobile electromagnetic compatibility. In order to accurately calculate the problems of radiation, conducted emissions and anti-interference, it is necessary to define in detail the situation where the body and the connection cable have been terminated. First import the body file, the software will usually automatically mesh. Then define the connection cable, antenna structure, equipment, etc. Define the device can use the schematic diagram or SPICE file, as shown in Figure 1 model. 
4 Automotive electromagnetic compatibility analysis process
(1) Adjust the component requirements according to the desired ECU function;
(2) Adjust component requirements according to specified car functions;
(3) Define the necessary specifications of components;
(4) Design and optimize components;
(5) Check whether the cable layout meets the electromagnetic compatibility requirements;
(6) Automotive EMC calculation;
(7) Adjust the components and cable layout according to the problem and re-analyze.
5 Comparison of analysis results
Use the TriD (moment method) in EMC studio and FEKO software to calculate the field shielding effectiveness (θ = 80 °, η = 90 °, φ = 45 °), as shown in Figures 2 and 3.
Different algorithms are used to calculate the voltage and current coupling the incident field into the cable (TriD-Moment Method, FEKO-Moment Method, TriD / MTL Moment Method and Transmission Line Method Hybrid Algorithm), as shown in Figures 4 and 5. 
Using different algorithms of FEKO and EMC studio software to analyze the shielding effectiveness, field-to-cable coupling, cable line radiation, and cable-to-antenna coupling, it was found that the calculation results of different software and different algorithms are in good agreement with the actual test results. It's just that the software calculation speed is different in the same hardware environment, and EMC studio calculation is faster. Figure 6 shows the time required to solve the same number of grid problems using the same configuration computer.
6 Conclusion
Choosing the design and analysis software for the electromagnetic compatibility of automotive systems requires different tools and algorithms for different problems according to the needs of users. Each algorithm is mature, and the calculation results of different algorithms are basically consistent based on the correct establishment of the model. With the help of analysis software, you can find and solve electromagnetic compatibility problems in automotive systems sooner or later.
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