Investigating cosite interference effects on an automobile

This article demonstrates how a full-wave simulation in CST MICROWAVE STUDIO (CST MWS) can be combined with RF cosite interference analysis in Delcross EMIT to identify and mitigate EMC/EMI problems. The causes of interference problems can be complex, and even when radio systems are operating on completely different frequency bands, there is still a risk of interference. Sources of EMI include broadband noise, ambient noise and harmonic & spurious emissions. Each of these has the potential to cause in-band and out-of-band interference in the victim receivers.

Installed antenna performance

The model being considered in this case represents a vehicle with two occupants. The vehicle is equipped with GPS satellite navigation, FM broadcast radio and two two-way radio systems in the VHF and UHF business bands. In addition, the passenger is holding a smartphone which includes a Wi-Fi transceiver.

The FM (port 1) and Wi-Fi (port 2) antennas were constructed in CST MWS, while the GPS (port 3), VHF (port 4) and UHF (port 5) antennas were imported from Antenna Magus, an antenna design tool with a database of parameterized antenna models. Antenna Magus can be used to find, synthesize and export an antenna design which fulfills the requirements. However, the car body will introduce additional effects such as reflection and coupling, which can affect the performance of the antennas and means that the synthesized design may no longer meet specifications once installed.

For this reason, a full-wave simulation can be carried out to calculate the installed performance and give a more accurate understanding of the properties of the antenna. The antenna models were exported from Antenna Magus into CST MWS and integrated into the car model. The model was simulated using the transient solver in CST MWS over the frequency range 0-2600MHz.