Simulation Study On The Electromagnetic Characters Of PEPS LF Antenna

As long as the developing of automotive industry, the request for safety, comfort and functionality is ever increasing. The entering and starting method of the vehicle is changing from the mechanical measure to the remote control access and electronic ignition. Now it seems the trend is that PEPS (Passive entry & push start) system will gradually replace the remote control system.Depend on the principle of radio communication, PEPS system works to achieve the function of intelligent opening doors and starting engines. However, there are some problems as following.On the one hand, the complexity of the metal vehicle body will affect electromagnetic properties of the low-frequency helix antennas of the system, and multiple sets of antenna in the system will produce mutual interference between each other. On the other hand, Smart-key-tag entering the electromagnetic blind spot inside or outside the vehicle is the major failure reason for the car's PEPS system. A low-cost way to understand the environmental characteristics of the electromagnetic fields inside and outside the car body is urgent needed during the design phase of electronic assembly, so that we could ensure the reliability of such systems to run assembly later.Therefore, how to judge and predict these effects with a reasonable method and guide the PEPS system's assembly based on the results of forecast have now become a major problem for the car manufacturers. With numerical simulation method, we can identify potential problems through the simulation and propose improved scheme before deciding the design of the vehicle equipment system. So it has a high economic efficiency. With the technology of numerical simulation and considering the specific request of the car manufacturer, we made a research on some problems about the low-frequency helix antennas of the PEPS system. The main works we did is as following.(1)We introduce the network ports method to simulate and analyze the problem of mutual interference between the transmitting antennas in PEPS system. A clear reflection of the mutual interference between the antennas has been given by making graph of the network S parameters.(2)To understand whether the simulation model in HFSS is consistent with the electromagnetic theory's guidance, we model the transmitting antenna in some simple environment in advance, and analysis the characteristics of the transmitting antenna and the mutual interference in these simple cases. This provides a theoretical basis for car body modeling.(3) The real geometric detail characteristics of the car body are very complex. If we just completely make modeling according to these details, that will inevitably result in a very large data model, and an ordinary personal computer will be unable to simulation. Based on the principle of "grasping the main contradiction", we made the body structure a reasonable simplification. Relaying on electromagnetic theory, we ignore the details that have little impact on the PEPS, put many flat plane together to replace surfaces and use contour parts to replace the details of construction. According to the geometric ratio of 1:1, we establish a vehicle body electromagnetic model.(4)We made simulation analysis on the low frequency transmitting antenna of PEPS system, which has been pre-installed in the car, and specially emphasized on the electric field, generated by the transmitting antenna, inside and outside the car.(5)We proposed the actual measure scheme, selected model car with PEPS system in the open field and took actual measurements in the selected key areas. Cornering the electromagnetic field distribution inside and outside the car, the simulation results were compared with experimental results. This confirmed the validity of the simulation results.(6)Considering the simulated and measured results together, we analysis the characteristics of electromagnetic field distribution inside and outside the car, which is caused by low-frequency transmitting antenna of PEPS system. These findings provide automobile manufacturers an effective recommendation to ensure the PEPS system works in a normal and stable situation.