Improving impedance matching of BCI inductor in 50 Ohm system

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Hosszú Sándor
Department of Broadband Infocommunications and Electromagnetic Theory

The people of our age every day meet electronic devices, which have increasingly important part of our life. When we use these equipments, they generate electrical and radio-frequency disturbances over a wide frequency range with various electrical characteristics in different modes: conduction, radiation or both, which can affect the normal performance of electronic devices (especially considering safety critical functions in the cars, e.g. anti-blocking system, airbag, etc.) inside its vicinity. Because of this, it is necessary to consider the electrical and electromagnetic environment in which these devices operate and agree to the limits, which the nearby instruments can tolerate.

The science of ElectroMagnetic Compatibility (hereafter EMC) has the task to examine these questions, which ones are very important from the first phase of the development-process because later they can create considerable additional costs and delays. For example if the problem comes out at the costumers, it has a chance that the developers have to rethink everything from the basics, and maybe they have to change the plans, e.g. the used parts, layouts, wiring and housing.

In the aspect of EMC, one of the most important industries is the automotive industry where the devices have to comply with strict requirements. The number of electronic components in the automotive vehicles has been increasing steadily over the past years and they are performing more and more complex functions. One main problem resulting from the dramatically increasing motor industry is the growing difficulty of the electromagnetic compatibility tests. One of the many test methods applied to test the electromagnetic compatibility of a device, is the Bulk Current Injection (hereafter BCI) method, when a BCI coil induces current in the device’s harness, and the device operation is monitored.

My task was to design an impedance matching network for a BCI coil (which is used in EMC Lab of Robert Bosch Ltd in Budapest), to eliminate the effect of the wide range functions which appear in the high standing wave ratio at the amplifier in the 50 ohms system, with the help of the members of this EMC Lab. Hereby, increasing the effectiveness of the BCI measurement process.


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