Research On The RF System Of TPMS

With the continuous progress of national economy and the rapid development of modern technology, the demand for car safety is increasing. So it is more significant for us to develop the TPMS with excellent performance and reliability by ourselves. However, now the stability and reliability of TPMS developed by our country is very poor. There are many reasons for the poor performance of signal transmission, but the un-stability of wireless signal is important one.This paper is focusing on the RF system of TPMS, the content is as below:1)Modeling and simulation of transmitter antenna and receiver antenna of TPMS. For the transmitter antenna, a dynamic antenna concept is introduced, which consists of a wireless sensor antenna, four wheels, and car structure; for the receiver antenna, a model used, which considers the influence of car body. The model of dynamic antenna is presented. The simulation results show the radiation of the receiver antenna and transmitter antenna is not the same on all the directions. This means that the transmission power will vary along the time; there are many nulls on the radiation pattern of the receiver antenna and transmitter antenna and there are no radiation power on these nulls, so the TPMS can't receive the signal sometimes. At the same time, the resistance variation will introduce some difficulties for the matching between power amplifier and transmitter antenna.2)The circuit design of TPMS transmitter and receiver. The TPMS transmitter and receiver are designed by adopting special integrated circuit modules. we focus on the design of the matched circuit of transmitter dynamic antenna, a simple and practical matching case between power amplifier and transmitter antenna is presented to solve the problem due to the resistance variation of the dynamic antenna, that is, the resistance on the 240°is used to design the matched circuit. The simulation results show that the return loss of the antenna port varies between 12dB and 36dB. This proves that this case can be used for the matched circuit design.3)In order to test the system performance of new TPMS, three test methods are presented, that is, static power transmission test, dynamic data transmission test and real environments test. The test results show: for the new TPMS, the power of wireless signal transmission is increased about 20~30dB; the frame correct rate of receiving data is increased from 61.4% to 97.8%; the results of real environments test show that the frame correct rate of receiving data meets the requirement of the TPMS; these proved that the system performance of the new TPMS is improved greatly.