Interference free FM reception in the car with ungrounded antenna base

It is preferred having FM antennas integrated in the vehicle instead of mounted on the roof. Another favoured option is the application of a Personal Navigation Device (PND) in the vehicle. Vehicle integrated antennas and PNDs don´t have a `large´ ground plane and generally don´t have a proper grounding connection near the antenna feeding point as roof mounted antennas have. It is therefore more difficult to achieve interference free radio reception in the vehicle. Antennas for PNDs don´t have a `short´ ground connection between the bodywork of the car and the antenna feeding point. The PND is grounded to the vehicle ground via the `long´ power supply cable only. This means that FM antenna concepts for PNDs are more complex to design than car integrated antennas. The presented principles for PND antenna design can be applied to car integrated antennas as well. This will result in better and cheaper vehicle integrated antenna concepts and gives more design flexibility for the car designer.