Research And Implementation Of The PKE Vehicle System Based On RSSI

The Passive Keyless Entry System is currently the most advanced car access system. This system uses bilateral authentication to ensure the security and users need not to press the button of the keyfob when unlocking or locking the door as usual. With the two advantages, it brings the high-grade car owners excellent customer experiences, and become popular aroud the low-end cars gradually. The related research in this field of China is at starting stage presently, and mainly depends on importing the technology aboad. Only several institutional units have been doing related research dependently. Therefore, author started the research in the theory and realization method of PKE.Firstly, author analyzed the principle of low frequency (LF) communication of PKE and how the system realizes positioning by 3D antenna, analyzed the method to realize this technology based on Ata5790 and the significance of successive sampling average and error compensation. Secondly, author designed an effective strategy for the PKE which is equipped with two antennas to locate the keyfob inside or outside the car according to the region detection. Thirdly, the paper analyzed the principle of the series resonant circuit of LF transmitting antenna and the parallel resonnat circuit of LF receiving antenna, analyzed the impedance matching principle of UHF transmitting and receiving antenna, and the operation principle of the vehicle electric lock. Then made a type selection plan of the chips, antenna, and complete the impendence matching of the antenna, lastly designed the schematic and PCB diagram. On the software aspact, aiming at realizing the positioning function, author made up a protocol of the LF and UHF communication, and designed the communication program, RSSI-Measurement program, keyfob location program and the ctrolling program of the electric lock.After completing the realization of the prototyping system, author tested the dissipation feature of the 125KHz signal, tested the effect of the coupling of the antenna on the RSSI. Then recorded the data of RSSI corresponding to distance by the coordinate paper and gained the threshold value in defining the effective detection area. Finally, we tested the positioning function of the system in K3, and the system could successfully locate the keyfob’s position. The results fit with the prefer anticipation...