# Estimation of SMPS' Conducted Emission According to CISPR Standards
## 4 Discussion  
Even though results obtained by the simulation are close to the real measurement, some differences can be observed. The source of those differences can come from:  
* Layout model has been simplified with respect to the original layout,
* Electrical simulation was simplified. When the proposed approach is implemented, the required level of simplification of the design should be considered in order to obtain the desired results. When the level of simplification will be too low, hence the analyzed model too complex, the computational requirements (RAM, CPUs, computing time) cannot meet actual resources available to the engineer. Due to this fact, before the implementation of the workflow, the right simplification strategy should be defined. This strategy should be carried out based on engineering judgment and should take into consideration:  
* \(\frac{\mathrm{d}\mathrm{j}}{\mathrm{d}}\) current loops, \begin{table}
\begin{tabular}{c c c} \hline \hline
**Parameter** & **10 kHz–150 kHz** & **150 kHz–30 MHz** \\ \hline RBW & 200 Hz & 9 kHz \\ FFT method & YES & YES \\ Dwell time & 50 ms & 50 ms \\ Detector & Peak and Average & Peak and Average \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Parameters of the measurement set in EMC32 Studio. Figure 24: Comparison of PK measurement (orange) and estimation (blue) for the HFSS approach. Frequency sweep 9 kHz to 30 MHz. Figure 25: Comparison of PK measurement (orange) and estimation (blue) for Q3D approach. Frequency sweep 9 kHz to 30 MHz. * \(\frac{\mathrm{d}\mathrm{V}}{\mathrm{d}\mathrm{I}}\) areas,
* Layout critical areas that can be the source of a concern. On the other hand, when the simplification will be too high (model will not be detailed enough) the results may not meet the requirements. Table 3 summarizes the simplification effects and areas of their impact. The engineer's goal should be to determine the point at which the model not too complex and still include all parts related to phenomena that are crucial for the final result. In general, complex and detailed models give more precise results but require a lot of resources while simplified models can be used for rough solution estimation when resources are not available. The results obtained by the authors, when compared with the measurement, show yields that in the proposed approach, from the accuracy standpoint, can be used for both:  
* New design optimization treating the result as comparable with laboratory measurements,
* Design optimization procedure by comparing two or more potential solutions and choosing the best performing one. As the conducted emission estimation using the proposed setup relates directly and only to the results obtained by the time-domain simulator, a few points need to be considered. Electrical models: the authors of this work prepared electrical models based on datasheet information. Neither of the active components were modeled using general library components. This part of the analysis is crucial for the final result and played a major part in the work. All details of the parameters not shown on the schematic can be found in Appendix A. Mesh size: during the work, the authors found that solution frequency (hence mesh size) has a big impact on the result. Due to this fact, for the layout models where HFSS and Q3D tools were used, the solution frequency was set to a relatively high value. If computational capabilities would be limited, the proper approach should be taken for proper mesh size definition. Complexity of the design: from the workflow perspective there is no direct limitation of the complexity of the device being studied. However, in the case where multiple component system analysis should be performed, the best approach is to divide the system into single components and analyze them separately. This approach will assure that each of the components fulfill the EMC criteria. Eventually the system is built from validated components using the proposed workflow.