Application of the equivalence principle and the multi excitation approach to method of moments simulations for optimizations of smart entry systems in vehicles

Smart entry systems become more and more important and require a high level of security for the open door and start engine permission. The system consists of several antennas placed on the car and on the driver (remote key). Some antennas are oriented to outside coverage and some other to the operation inside vehicle. The characterization of the field behavior inside and outside the vehicle is of prime importance for the system evaluation and optimization. Measurements which are used for this purpose need a long time for the system evaluation. 3D filed simulation can be used to optimize the placement of the appropriate antennas. In addition, a reduction of the needed number of antennas, keeping an equivalent system performance might be achieved. There is in many cases still a need of such optimization in order to find out the best antenna positioning in the vehicle. Relevant for this present work are the radiating mode antennas, which are normally ferrite coils. These antennas are reliably modeled by the method presented in this article. Besides that, investigations based on simulations are presented for visualization of magnetic field radiated by smart entry coil antenna in vehicles.