Electromagnetic compatibility (EMC) is a key prerequisite for the future topics connectivity, autonomous driving, shared, and electric drivetrain. With the new test facility, Mercedes-Benz takes an important step in the digitization of the automotive industry.

The new reverberation chamber makes efficient and comprehensive EMC measurements possible. 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. Daimler invested about 50 million euros in the new building at the Mercedes Benz Technology Centre (MTC) in Sindelfingen.

The measurements taken there contribute to

• electromagnetic fields of vehicles not interfering with other receiver systems – including those in the own vehicle,
• minimizing the exposure of the passengers in the vehicle interior,
• the vehicle functions not being impaired by external (electromagnetic) fields and
• maximizing the reception quality and performance of the antennas.

The test facility at the Mercedes-Benz Technology Centre (MTC) 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.

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. The day-to-day operations with such tests in the EMC facility will start at this central location already tomorrow.

New building is protected against interferences

Over 200 employees work in the new EMC facility in part in multiple shifts. Construction started in late November 2016.

Another special feature of the antenna testing hall is the flooring: It has the same properties as a dry asphalt or concrete roadway and offers the possibility to be converted to a metal or absorbing floor and thus makes a wide range of realistic test set-ups possible.

EMC testing in the reverberation chamber

A highlight of the new test facility, a 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 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 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 the antenna specialists of Daimler, 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.

Thanks 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.