Study On The Passive Wireless SAW Sensor Hardware System

In many special situations it is necessary to use passive wireless sensors to measure temperature, pressure, stress variation and acceleration in rotors, moving automobile tyres, some high temperature and high voltage situations and so on. Therefore, passive wireless sensing mode has more extensive applications. This paper analyses the operating principle of SAW resonant sensor, builds a passive wireless SAW sensing measurement system applied to temperature detection, and studies on the practicability of the system. Aiming at the complex hardware and the shortcoming that the signal processing unduly depend on hardware, this paper offers a kind of simple and practical transmitter which is cheaper and more adaptive for using in industry. Dimension of the antenna is always limited in non-contact measurement, so designing a high performance small antenna is very important. This paper chooses a normal mode helical antenna to replace the short dipole antenna to improve efficiency. Improving the service efficiency of an antenna and the matching between a small antenna and a SAW sensor is very important for remote measurement. The resonant frequency of the sensor changes obviously when the temperature of the environment changes greatly; the frequency band of the small antenna connected with the sensor changes with the environmental condition, such as the varying distance between the antenna and the ground or between the antenna and the surrounding metal objects. So broadband matching between the antenna and the sensor is adopted to reduce the influence of the resonant frequency of the antenna—sensor due to the change of both the resonant frequency of the sensor and the frequency band of the antenna. Practicability of the passive wireless SAW sensor system is proved by the experiment. The obvious effect of the broadband matching to improve the adaptability to environment of the measurement system is also verified.