Whitepapers

Despite the fact that meeting these standards can require a significant amount of time and effort, some PCB engineers continue to rely solely on experience and traditional design practices. The incorporation of simulation to assist in designing against EMI may be considered not necessary, accurate, or feasible for those who don't understand the risks associated with testing a product that has not been validated. Given that many PCB manufacturers who have turned to Rand Simulation seem to share these misconceptions, we dug into this reluctance a little deeper. We found the majority of those who initially would not consider using simulation software to test their design reconsidered when they were reminded of several facts: 1. 50 percent of all new designs fail FCC Part 15 EMI compliance testing or pre-testing 2. A single FCC compliance test costs an average of $30,000 3. A typical board spin costs an average of $10,000 4. Supply chain disruptions during the COVID-19 pandemic have created a 50-week lead time for certain electrical components that is expected to last until at least 2024 Common Misconceptions Surrounding Simulation for PCB Designers From interviewing hardware engineers, systems engineers, and project managers at companies of all sizes and maturity levels, we found that many who had been through the FCC compliance testing process understood the risks and worked to mitigate design issues with simulation software. It was engineers new to bringing products to market that were hesitant to leverage simulation in the design phase. Here are a few of the common misconceptions we hear from less experienced designers regarding EMI compliance testing: 1. Passing the FCC compliance test is not difficult 2. If you use pre-certified components, you won't have a problem 3. Lab pre-testing is not necessary 4. Simulation cannot be leveraged to understand EMI 5. Layout best practices are sufficient with the latest communication protocols 6. Signal integrity is not a concern if a device passes compliance testing As with many misconceptions, each of these may have had a basis in truth at some point in time. However, advancements in software and innovative simulation approaches have changed the game. Now, the right simulations done at the right time can reduce the design/build/test/repeat cycle and give companies confidence that their designs can pass compliance testing the first time. When EMI Simulations Make Sense While the technology needed is available—and continually improving—to simulate a complete model of a product, the resources required may be cost or time prohibitive, and in many cases, not necessary. We have had great success working with customers on the problems of EMI to break their products into a collection of the most EMI-sensitive sections, so that the simulations test the most important pieces. This approach delivers the most critical information in less time and for less money. Here are a few examples of simulations we have performed for customers looking to verify the effectiveness of specific EMI-sensitive sections of their PCB designs: ► Determining the radiated emissions impact from changing switch-mode power supply components on an existing design ► Evaluating near-fields radiating off DDR bus ► Determining whether shielding over components are necessary

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