Tire Pressure Monitoring System (TPMS) has become a popular system due to regulation in many countries. TPMS consists of sensors that measure air pressure and temperature in the tires. Each sensor transmits tire information to TPMS central unit for display purpose via RF. Commercial trailers having bodies longer than 7 m require RF repeaters to increase the data transmission range. Located near to rear wheels, RF repeater receives sensor signal in the rear wheels and transmits the signal to TPMS central unit.
In this paper, we discuss RF repeater which transmits at multiple frequencies in order to increase signal reception. On TPMS central unit, RF receiver is able to tune to receive frequencies used in sensors and RF repeater. Other method for improving reception is to transmit same payload multiple times at same frequency as that of sensor.
In the paper, other important specifications are discussed as RF repeater design is concerned. A user’s case of RF repeater is implemented. Time required for a complete transmission or reception is measured in the user’s case. As each TPMS sensor transmits periodically (e.g. 30 s) to the RF repeater, short time is required to change between receive and transmit modes for RF repeater. So the switching time between receive and transmit modes is measured in RF repeater. In the receive mode, RF repeater measures the Received Signal Strength Indication (RSSI). This RSSI can be used to indicate if location of RF repeater is optimum for receiving sensors in the rear wheels.