Electromagnetic compatibility (EMC) is a key prerequisite for the automotive megatrends of connectivity, autonomous driving, shared, and electric drivetrain (CASE). Yesterday, Daimler inaugurated a new test facility for electromagnetic compatibility (EMC) and radio-frequency (RF) antenna systems at the Mercedes-Benz Technology Centre (MTC) in Sindelfingen, Germany. Daimler has invested about 50 million euros in setting up the brand-new facility.

The new reverberation chamber makes efficient and comprehensive EMC measurements possible, where new measuring methods allow vehicle antennas to be measured quickly and realistically. The complex simulation of the global mobile communication services in the new antenna testing hall makes system development in terms of maximum data protection possible.

The measurements taken there contribute to:
- Electromagnetic fields of vehicles not interfering with other receiver systems – including those in the own vehicle,
- Minimising the exposure of the passengers in the vehicle interior,
- The vehicle functions not being impaired by external (electromagnetic) fields and
- Maximising the reception quality and performance of the antennas.

The test facility at the Mercedes-Benz Technology Centre (MTC) is claimed to be one of the most advanced in the automotive industry. It sets standards for the comprehensive protection of the vehicles with new measuring and testing methods, which were developed together with the Technical University Ilmenau (Thuringia), the TU München and others.

"We are a pioneer in the digitisation of the automotive industry. The new test facility for EMC and antennas is an important step to ensure we remain a pioneer," says Sajjad Khan, Member of the Divisional Board of Mercedes-Benz Cars responsible for CASE. "Because all four CASE fields of our corporate strategy – connectivity (Connected), autonomous driving (Autonomous), flexible use (Shared & Services) and electric powertrains (Electric) – require the transmission of data. In physical terms, all these data streams use electromagnetic waves as a means of transport“.

A Mercedes-Benz passenger car can have more than 200 control units; an S-Class vehicle has over five kilometres of wires. On one hand, the electromagnetic compatibility therefore must ensure that the electronics installed in the vehicle do not cause any interference that could disturb other vehicles or devices. On the other, there are a myriad of electromagnetic waves that reach a vehicle from the outside. The cars therefore must be designed in a way that ensures that their electronics along with particularly important functions such as engine control and driving assistance systems are not impaired. For this reason, a vehicle from Mercedes-Benz undergoes many EMC tests before it gets an approval.

EMC testing in the reverberation chamber
A highlight of the new test facility is a unique reverb (short for reverberation chamber). It allows interference immunity measurements to be conducted there in an especially efficient manner and in particular self-driving vehicles to be tested comprehensively for their immunity to electromagnetic interference.

The 'reverb' houses three large mechanical 'stirrers'. These spiral reflector structures rotate at speeds of ten or 120rpm, which constantly distributes the electromagnetic waves in the room.

The reverb houses three large mechanical 'stirrers'. These spiral reflector structures rotate at speeds of ten or 120 revolutions per minute, which constantly distributes the electromagnetic waves in the room. It is possible to demonstrate that this electromagnetic field distribution is locally equivalent to irradiation with an antenna from all directions.

A major efficiency gain, because in the past the vehicle was bombarded sequentially with antennas from different directions and with different polarisations. This is now done in the reverb very quickly as part of a single test step. Daimler designed the stirrer system in-house.

Realistic scenarios for antenna testing
Modern vehicles have more than just the classic radio antenna; they are also equipped with antennas for radio broadcasts, mobile communications, navigation, WLAN, Bluetooth, rf central locking system. They all need to be developed to achieve an optimal reception quality. Furthermore, the antennas may not interfere with each other.

The new 5G mobile communications standard creates additional requirements. One antenna is no longer enough to physically achieve the future data rates. That is why two or four antennas are usually used simultaneously in order to make the high data throughput possible. In addition to the individual radiation patterns, this requires analysing both the array of the various antennas – the experts refer to it as MIMO: multiple input, multiple output – as well as the receiver in the measurement technology.

Apart from classic antenna measurements, the antenna hall also allows conducting tests of such complex receiver systems as measurements of the data throughput. An important test set-up, because the reception in the moving car depends on many factors, e.g. the number of users in a cell or the location and the density of the transmission towers in a region. Trucks passing by and the buildings as well as the vegetation also can influence the data throughput.

That is why according to Daimler, its antenna specialists, together with experts of the Technical University Ilmenau, developed a method that for the first time allows simulating such scenarios for a vehicle in a reproducible way, and measuring them. All globally available and future frequency bands and services can be emitted in the hall, which is crucial for mobile communications, navigation and for automated driving.

Due to the shielding of the hall, there is no interference with the actual radio, TV and mobile communications transmitters in Sindelfingen and the surrounding areas.