Design of wireless SAW humidity sensor node based on radio wake-up technique

Wireless sensor node based on wireless wake-up technique can not only reduce its power consumption, extend the battery´s life effectively but also guarantee the transmission distance and make it easy for detection. Wireless surface acoustic wave (SAW) sensor has got widely used in many fields due to its advantage of high sensitivity, small size and low cost. To overcome the shortage of passive SAW sensors, a radio wake-up method was proposed at first, based on which a wireless SAW humidity sensor and its detection system were designed. In experiment, a 5-level half-wave voltage doubler circuit was used to generate the wake-up signal. The result showed that it could exactly wake up the sensor node within a distance of 1m. In this distance, the system could detect the humidity information effectively. The resolution in low humidity range (10%-40%) was near to 200Hz/%RH and up to 1 kHz/%RH in high range (40%-100%).