Improving Power Efficiency and Reliability in RF Tire Pressure Monitoring Modules

The paper deals with RF Tire Pressure and temperature Monitoring (TPM) systems for automotive. Currently, most systems are characterized by an unidirectional link from the RF TPM sensors on the wheels´ rim to the receiving/processing unit on the vehicle chassis. This way the battery-powered transmitter is always active wasting power also in parking mode, when TPM is not required. Without a feedback channel, the TPM transmitters cannot be forced in power-on or off depending on the vehicle status; moreover there isn´t an acknowledgment that the receiver has correctly interpreted the data and retransmission of erroneous packets can not be requested. We overcome such problems by inserting a low-complexity RF wake up circuitry on each TPM module, now acting as slave, whose power-state is driven by the processing unit on the chassis through UHF transmission. Power consumption in idle mode can be reduced in average by a factor 30. To increase system reliability a proper encoding of the wake up RF pulses is introduced. Collision between data transmitted by different TPM units is avoided through a time division policy by the vehicle processing unit now acting as master.