Against that noise: EMC simulation and design for automotive interior

Contributor: Amir Geranmayeh
Posted: 04/27/2015

Dr. Geranmayeh you work as EMC-Design/Hardware-Engineer at the interior division of Continental Automotive, could you tell us a bit more about your personal background and experience with Electromagnetic Compatibility (EMC) simulation and design?

Every new product development in Continental Automotive GmbH, particularly in our Business Unit Instrumentation and Driver HMI should undergo initial EMC-simulation check and layout review. An EMC engineer principally should prevent large return current loops to suppress the induction of unwanted noise in electrical systems.

This can be ensured through layout routing optimization, proper decoupling capacitor measures, component placement, optimum ground plane connections, shielding enclosure, usage of ESD pro-tection diodes, common mode rejection choke or ferrite to define high impedance on the way of high-frequency propagating noise etc.

What is the main challenge that every hardware engineer for automotive interior faces when it comes to EMC simulation and design?

For the operation of different electronic blocks, different levels of voltages are needed. Nowadays, for the sake of efficient power
consumption, the switching mode power supplies (in buck/boost convertor forms) are frequently used in every PCB. Also, for driv-ing LED lighting or back light illumination pulse width modulations are used.

These transient periodic pulses and high-speed signaling of graphic processor or pixel clocking of display excite higher harmonics of the switching currents in the frequency spectrum which radiates extensively. Additionally, these ringing tones may also travel through the different conductive PCB layers or cable harnesses and generate conducted emission or immunity problems. If due to any discontinuity, the current does not find its return path to the source via the GND plane beneath the signal trace, it may raise extra common mode distortions in RF bands.

In you opinion how could EMC simulation contribute to reduce the product development costs?

For example in mobile phone antenna nearby tests, thousands of orientation with respect to the product has to be checked. With exact near field modeling, one can follow in ad-vance which orientation would cause the most susceptible (worst) case or by knowing the resonance frequencies of the metallic shielding enclosure one can prognosticate whether the cooling slots can cause radiation in the frequency bands of interest or not.

In the field of EMC simulation and design for automotive inte-rior, does it make any difference for you, if you are working with a high voltage system for EVs and HEVs, dual voltage system 12V/ 48V for micro hybrid applications or convention-al 12V systems?

No, from the EMC point of view, they follow same physical rules. For example, in some free-programmable instrument cluster with large display size the supply voltage is also boosted up to 36V. Car drivers are demanding more connectivity in vehicles the usage of Ethernet as a backbone for the architecture is in-creasing and cars will have more data boosters and video display signals.

How are you planning to fulfil consumer’s needs and at the same time keep the EMI immunity of the sys-tem?

Ethernet cables are cheap but unshielded and this makes them more susceptible to interfering noise. The broad-band impedance matching on both sender and receiver sides of bus systems is the main precaution to avoid energy bouncing and reflection.

How do you see the EMC standardization landscape for the automotive market today, and do you see any need for new standards?

The uncertainty in EMC measurements especially in the near-field zone of receiving or transmitting antennas normally may reach to 3dB, i.e. 50% deviation from a concrete statement. As the modern measurement equipment is now supporting illustration of statistical characteristics of the test data, future standards may also ask for the expected value range, instead of absolute peak detection.

In your opinion, how important is it to involve industry part-ners (e.g. Semiconductors) in the early stages of EMC simula-tion and design of the hardware architecture?

Normally due to the intellectual property rights, the chip producers avoid to deliver a realistic simplified spice model for the non-linear functionality of their IC. Also, OEMs may not voluntarily give ter-minating loads information in their active product datasheets. As the IBIS model provide a common frame work which reflects mu-tually ECU development demands and semiconductor company possibilities, close ties with semiconductor companies can end up with the provision of a complete IBIS version 5 model for their chip. Also direct power injections to the IC pins as well as 1 Ohm or 150 Ohm emission testing can ensure the compliance of their products at the IC level before it is integrated in the system level.

The automotive market is keeping the eyes open on the target of having fully automated driving vehicles with complex C2C and C2X communication technologies by 2025. What do you imagine to be the main challenge for EMC simulation and de-sign experts in 2025?

For the expanding wireless communication traffics, e.g. in car to infrastructure (C2I) technology, manufacturers have to use higher and broader frequency bands. This automatically extends the spectral range that has to be kept immune from distortion and crosstalk effects.

Dr. Geranmayeh, thank you for your time.

Related Stories:

EMC Technology Report: The effect of split-voltage 12V/48V in modern cars

EMC Technology Report: EMI challenges in connected vehicles

EMC Technology Report: Collaboration and standardization

Contributor: Amir Geranmayeh
Posted: 04/27/2015

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