This article is geared toward engineers, who for various reasons, tend to stay away from modeling and simulation software and focus more on actual EMC measurements in order to show that their designs meet EMC regulatory compliance requirements.
If you fall into this category, you are doing the companies, customers and yourself a huge disservice. Proving a design is valid only after it’s already built often results in a costly and time-consuming test-analyze-fix-repeat process. Attempting to build a bullet-proof design that easily passes EMC requirements, when using previously established guidelines and outdated rules of thumb (and other brute-force methods), often results in unknowingly designing a product that is way over-designed (i.e. has a lot more design margin than it really needs). This one oversight ultimately results in a product that is too costly to manufacture and almost impossible to make a profit on. Alternatively, by using these same outdated guidelines and processes, you may unknowingly under-design the product and find out that too late that it fails mandatory EMC compliance testing requirements and yet another costly, time-consuming (and embarrassing) redesign effort is required. Redesign efforts that occur at the tail end of the product development process, just before the planned
production release date, are not good. This rework results in costlier and harder to implement fixes, not to mention increased pressure and anxiety placed on an already stressed product development team scrambling feverishly to find viable solutions in time to meet the already late and promised customer ship date.
Most of this churn could be avoided by getting a little savvier in using some of the various simulation and modeling tools now available. There is a plethora electromagnetic modeling codes, circuit solvers, rule checkers, analytical modeling tools, web-based calculators and apps that we should carefully consider using prior to any prototype PC boards ever being ordered. The good news is that we don’t need a lot of advanced training in electromagnetics in order to effectively use these tools. The bad news is that there is a ton of simulation and modeling tools available and understanding what to look for can be tricky. To ease your own research efforts, you may find the following helpful. It categorizes the modeling and simulation software tools that are currently available so that any engineer can more easily conduct further research and gain a better insight into the proper use and application of these tools. Note that you may already have access to some of these tools.
Numerical EM Modeling Tools and Techniques
Modeling and simulation tools of this type include 2D, 2.5D and 3D tools, static field solvers, time domain and frequency domain codes, boundary element codes and the method of moments (BEM/MoM), finite element codes (FEM), finite difference time domain codes (FDTD), transaction level modeling (TLM), generalized multipole technique (GMT), finite-element time domain (FETD) and Partial element equivalent circuit method (PEEC) codes, geometrical theory of diffraction (GTD), uniform geometrical theory of diffraction (UTD) and physical optics (PO) codes.
Analytical Modeling Tools
These tools include impedance calculators, interference and crosstalk estimators, and maximum emissions calculators.
EMC Rule Checkers
These tools organize and maintain rules for PCB layout and rules for system design.
Applications
The applications and uses for these modeling and simulation tools are many. For example, these tools can be used to model currents induced on cables, cords and wiring harnesses, model power inverter noise, specific radiated emissions tests, bulk current injection tests, high-frequency package parasitics and transient susceptibility. We can model an automotive infotainment system, and Gbps backplane connector, if so desired. Furthermore, these modeling and simulation tools can be used for EMC troubleshooting and educating engineering teams regarding the viability of solutions to the EMC design challenges faced in current product designs. This comes in handy when trying to prove to the rest of the product development team (often with conflicting requirements), that our solution to a problem is the best one to implement. This is an almost impossible task to accomplish if we wait until we have prototypes available to test and simply try to prove our point with test data. Simulation results backed by test data can be very powerful and almost impossible to argue against good data. On your own you can probably think of other valuable uses of these applications and may even find yourself tailoring some to fit you own particular needs.
Pitfalls
Modeling and simulation software should be considered as just another tool in our engineering bag of tricks and that it can and should be used to flush out issues in designs prior to making any substantial investments in tooling or prototypes. Keep in mind that modeling and simulation is not a magic bullet solution where we plug in everything we know about the problem into the system and it magically spits out the ideal solution. It takes the knowledge and experience of an engineer to break down problems into smaller chunks in order for our modeling and simulation efforts to be most effective. This may require a multi-stage model where the output of one model’s simulation acts as input to the next. In this way, each part of the problem, and associated model, is fully optimized, resulting in a much more accurate combined solution. Engineers must first understand what the problem is to be solved, how to break it down into smaller chunks, and what modeling technique will best help to solve that specific problem. This simplifying activity may take extra practice and effort at first, especially for
those of us who rather do things “old school” and are reluctant
to change.
Conclusion / Additional Resources
The main point of this article is to emphasize to engineers to not overlook modeling and simulation as an important and viable tool in developing products that have to meet EMC compliance requirements. It also points out that learning and using these tools isn’t necessarily reserved for only the advanced EMC practitioner. If you’re interested and desire further information and training on this important topic, Dr. Todd H. Hubing Professor Emeritus of Electrical and Computer Engineering at Clemson University and Director of the Clemson Vehicular Electronics Laboratory provides a one-day course covering much of what has briefly been mentioned in this article. Details on this course can be found here: https://learnemc.com/computer-modeling-tools-for-electromagnetic-compatibility.
Additionally, Bruce R. Archambeault, Omar M. Ramahi, and Colin Brench have written a book of this subject out titled “EMI/EMC Computational Modeling Handbook” which goes into much further detail than what can possibly be covered here.
Best of luck to you in utilizing simulation and modeling on your next big project!
References
- Archambeault, B.R., PCB Design for Real-World EMI Control, Kluwer Academic Publishers, 2002.
