Optimizing the Layout of Passenger Car Glass Antennas

Integrating antennas in windscreens has become popular due to the enhanced aesthetics and the increased antenna surface area that enables improved reception. However, the design of such antennas is a complex procedure. In the frequency range of FM-, DAB- RKE- and TV-antennas, the vehicle body forms part of the antenna. This leads to the glass antennas often having to be adapted or redesigned for each car line and variant. Different glass types also have an influence on the antenna performance, and different configurations can change the impedances of the multiport antennas. Additionally, different antenna concepts are needed for different vehicle types.

Antenna systems contain different antennas with mutual coupling, making it very inefficient and time consuming to optimize the FM-, DAB-, RKE- and TV antennas independently. Wanting to make the optimization process of its multi-port antenna more efficient, Daimler turned to Altair for assistance.

Altair ProductDesign suggested that these issues could be addressed with a jointly developed windscreen antenna analysis method within HyperWorks’ electromagnetic suite, FEKO.

The solution would have to represent the dielectric properties of multiple layers analytically, enabling a very efficient simulation of windscreen antennas. In addition, the complete system must be considered for the evaluation of the different antennas. To do this efficiently, Altair ProductDesign implemented multi-port post-processing, which allowed different port configurations to be re-evaluated without re-running the solver. The method would be extremely helpful when considering amplifier configurations for different variants.

The antenna optimization procedure developed by Altair ProductDesign, using FEKO's Windscreen Analysis Tool, has become a standard process for all windscreen antenna layouts of new car lines. The process ensures a highly mature antenna layout and also allows for the evaluation of the electromagnetic noise at the antenna port for different emission scenarios, which helps to identify worst case EMC scenarios. Since the number of vehicle variants is ever increasing for Daimler – and simultaneously the number of hardware prototypes is reduced – this variety can only be managed efficiently with the use of simulation technology.

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