A Wireless Sensor Node Supporting Various Powers Supply and Communication Methods

Problem statement: This study presents a wireless sensor node dedicated for in-tire pressure and temperature monitoring. Additional features set it apart from the many different systems available on the highly competitive market. State-of-the-art implementations are mounted on the rim of a tire. Here the sensor node will be mounted on the inner liner of the tire. By moving the sensor node from the rim to the inner liner, new challenges in the analog design arise. Approach: To implement this sensor node new power supply methods are investigated. Next, analog designs with the focus on low power are developed. Since the sensor node is operated in a harsh environment, robustness is a key issue. Results: The discussed sensor is capable of either active or passive communication. The passive communication is used in the field of Radio Frequency Identification (RFID), whereas active communication is used to transmit the sensor data. A combination of both is also possible. To supply the chip in the tire an RF energy harvesting interface is implemented. An input sensitivity of -19.7dBm for the harvesting interface and -12.5 dBm for the RFID interface is measured. The on-chip temperature sensor consumes 4μA including the analog to digital converter. Conclusion: Choosing the discussed sensor node for in-tire monitoring enables new fields of applications. With this sensor node sensing additional parameters like road condition is possible. Using passive communication improves warehouse management for tire manufactures. Also, tire type identification at the car is enabled.