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EMC compliance issues identified before prototyping.

Radiated and conducted emissions from printed circuit boards (PCBs) can play a critical role in the EMC performance of devices: when a PCB includes a power plane that is near to signal traces or other power planes, there is a risk of energy transfer between parts of the system. Not only does this coupling lead to power switching noise being transferred into data signals, it also means that power supply systems may demonstrate additional resonances that are not seen in the individual components. This can affect the power integrity and may reduce speed or reliability. Simulation can be used to help reduce these effects.


Miniaturisation means that PCB manufacturers are now producing boards with high packing densities and as few layers as possible. In addition, modern PCBs often require several supply voltages, and therefore must include multiple power planes. This leads to circuit boards that include pairs of power planes which are not separated by ground layers. Such power planes can easily couple to each other, either on the same layer or on adjacent layers.

Each power plane will have certain resonances, and the coupling to other planes can change these resonant frequencies. Since the resonances affect the impedance of the power distribution network (PDN), it is very important for the designer to consider these resonances when laying out the board.

Modern complex circuit boards have many metal layers comprising thousands of signal traces, and can be very large compared to the wavelength. Simulating such a complex circuit board to identify resonances can be a challenging task, especially when taking into account all of the circuit board layers and all of the traces. Circuit simulation--representing the circuit board with R, L and C lumped elements, is not practical--and building an RLC circuit to represent such a complex board is almost impossible.

EM field simulators provide a better approach, offering more accurate results than classical techniques such ascircuit simulators like SPICE. However, fullwave simulation needs high computational resources, and to meet the time requirements of the development cycle, it is often only applied to simplified models. Often, these simplified models ignore neighbouring power nets and signal traces above or below the power plane.

Now, and shown for the first time at the end of January at the Santa Clara Expo DesignCon 2015, is CST EMC Studio, a product for electromagnetic compatibility (EMC) and electromagnetic interference (EMI) analysis.

CST EMC Studio contains a toolkit of solver technologies for the study of EMC effects--general purpose 3D modules for time and frequency domain simulation alongside more specialised solvers. In particular, it includes the 3D transmission line matrix (TLM) method solver, which simplifies numerical EMC analysis, such as compact models and octree meshing.

Targeted at users across a wide range of industries, including telecommunications, defence, automotive, electronics and healthcare, the electromagnetic simulation software is designed to identify potential compliance issues before an actual prototype is built, as well as to analyse products that fail compliance testing. Engineers can study effects such as radiated or conducted emissions in consumer electronics devices, or susceptibility to electrostatic discharge, lightning strike and high-intensity radiated fields (HIRF).

"Through the development of simulation tools and specialised workflows specifically for this segment, numerical EMC analysis can be integrated earlier in the design process," said Dr Bernhard Wagner, Managing Director, CST.

For analysing printed electronics, the import functionality is key. EDA import formats supported include those used in Cadence Allegro, Mentor Graphics, Xpedition, Zuken CR8000 and ODB++ databases. An EMC rule checker allows potential problems on PCBs to be detected--these can be then analysed in 3D by the full wave solvers.

* Analyzing Power Integrity Issues from Power Plane Interactions. Joachim Held EMC (Design Engineer Siemens AG Industry Sector Drive Technologies Division) and Richard Sjiariel (Senior Application Engineer) CST AG.
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Publication:Environmental Engineering
Date:Apr 1, 2015
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