Gain and efficiency measurement of antennas for an advanced Tire monitoring system

Advanced tire monitoring systems (ATMSs) belong to the most promising future developments in vehicle safety. ATMS expands the possibilities of classical tire pressure monitoring systems (TPMSs) by additionally acquiring sensor data (e.g., tire temperature, contact area, vertical load, slip angle, and street conditions). These systems are composed of wheel units (WUs) mounted in each tire and an on-board unit (OU) located in the car body. Each WU contains sensors and a microchip which is connected to an antenna. The measured tire and road attributes are transmitted to the OU. One of the hardest challenges in developing an ATMS system is the design of an efficient antenna for the WU. In conventional TPMS the WU and its antenna are integrated into the valve [1] or are mounted on the rim of the wheel [2, 3]. To enable the measurement of additional sensor data, the WU in ATMS has to be moved to the tire itself. Thus, knowledge about the tire structure and the dielectric properties of the rubber material are mandatory. Exploration of these parameters can be found for example in [4] and [5]. In this contribution WU antennas - a dipole and a loop - directly attached to the tire rubber are investigated. Significant effects of the tire environment on antenna gain and radiation efficiency, as well as on the radiation pattern have been observed.