Modelling of the coverage range for modern vehicle access systems at low frequencies

The prediction of the system performance of the different automotive applications is one of the challenging tasks in the next future. For the Passive Start and Entry [1] system named PASE representing a wireless card or key based innovative car access system, placing antennas in and around the car to ensure a good coverage is the main topic of this publication. The main parts of the PASE system are the access card or key containing LF and RF antennas as well as transponder, the antennas positioned at different places within the vehicle responsible for the signal coverage of the interior and exterior area around the car and finally the control unit within the vehicle. As soon as the key owner approaches the vehicle and pulls the door handle, the car automatically detects and authenticates the access card or key within a few metres range from the car. For the uplink from the vehicle, the frequency of 125 kHz is used and for the downlink from the key to the controlling unit placed in the car the UHF frequency of 315 MHz corresponding to the U.S. regulations and 434 MHz for European countries. The magnetic field distribution generated by the LF antennas is of high importance as the identification cards require sufficiently strong magnetic field strength.