The test facility at the Mercedes-Benz Technology Centre (MTC) in Sindelfingen is one of the most advanced in the automotive industry. Daimler invested about 50 million euros in the new building. With new measuring and testing methods, which have been developed together with the Technical University of Ilmenau and the Technical University of Munich, among others, it is intended to provide comprehensive protection for vehicles.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.
Protection against interferences
Over 200 employees work in the new EMC facility in part in multiple shifts. Construction started in late November 2016. More than 60 companies were involved in the design and construction of the building.
In addition to the administrative wing, the building houses three halls for EMC tests and one especially large hall that rises three storeys for RF antenna tests. These halls use metal to provide complete shielding against outside interferences.
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.
The halls are equipped with turntables and chassis dynamometers for the vehicles to be tested in order to investigate signal interferences from different directions in stationary or moving vehicles. Cameras monitor the test set-ups in the test facility during a test. The developers sit in the operator room and are able to control and observe the measurements on the test rigs from there on monitors.
Highlight: 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 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.
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 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.