# Model-Based Analysis and Improvement of Vehicle Radiation Emissions at Low Frequency
## 5 Application and Analysis
### Problem Analysis and Improvement  
As shown in Figure 5, the electric field is out of the limit. To identify the main technical factor causing this emission problem. The importance analysis of each factor has been conducted using the method introduced in Section 4.1 and some analysis results of the contribution and improvement potential of technical factors are shown in Figure 11.  
Figure 10: Comparing result of electric field at left side.  
Figure 9: Parameters of networks: (**a**) S-parameter; (**b**) Z-parameter.  
The comprehensive evaluation score calculated by Equation (9) are visualized by the heatmap shown in Figure 12a, where _Si_ (_i_ = 1-3) denotes the interference sources, _Pi_ (_i_ = 1, 2, 3,... ) denotes the coupling paths. According to the evaluation score, the DC/DC converter (denoted by S3) is the main interference source technically. But other non-technical factors, such as application difficulty and cost, are also should be considered to determine the final solution. It is almost impossible to measure these non-technical factors quantitatively and accurately. With the technical evaluation score shown in Figure 12a, five experts are invited to conduct the hierarchical analysis to get the judgement matrices, \(J\)1 and \(J\)2, \(i\) = 1,..., 3. As shown by Figure 4, \(J\)1 is used to evaluate the relative importance among the three factors in the first layer, i.e., cost, application difficulty and technical contribution. The judgement matrices \(J\)2, \(i\) are for the evaluation of the factors in the third layer. For each factor, its importance is evaluated by compared with other factors in the same layer and measured from 0 to 9 (0 is the least important one and 9 is most important). With the judgement matrices, the evaluation score to determine the final solution can be calculated by Equation (11) and the results are shown in Figure 12b.  
According to the hierarchical analysis result, DC/DC (denoted by S3) and its coupling path with the measurement antenna (denoted by P6) lie in the top two. Their final evaluation scores are 0.1445 and 0.0823, respectively. The interference generated by DC/DC is preferred to be attenuated, and considering the frequency range where the electric field exceeds the limit, a single-phase DC power filter is selected finally.  
The radiated electric field with the selected filter is shown by Figure 13 which satisfies the requirement of SAE J551-5. Though the proposed strategy has been applied to diagnosis and improvement of the radiation problem of EV at the stage when the sample vehicle  
Figure 11: Technical analysis results: (**a**) Improvement potential; (**b**) Contribution.  
Figure 12: Problem analysis results: (**a**) Importance analysis results; (**b**) Hierarchical analysis for final solution.  
is ready, it can also be adopted at the early stage if the required model parameters are available.  
Summarizing the model based analysis and improvement process for vehicle radiation problems introduced in Sections 3 and 4, and the application results in this section, the advantages and disadvantages of the presented strategy are summarized in Table 1.