分布式无源无线声表面波传感器阵列研究

As the velocity of electric-magnetic waves is much greater than that of the surface wave, while a SAW device transforms the electric energy into mechanical energy, it actually slows down and delays the energy flow of electric-magnetic wave. This is obviously reflected in the physical phenomenon that even an excitation to a SAW device ends there still exists a transient output. This energy-storage trait along with the RF frequency operation property provides the physical base for SAW devices being used as wireless interrogational passive sensors. The wireless sensing signal of a passive SAW sensor is responses of the SAW device in a passive circuit to wireless RF (radio frequency) interrogations. It is transient and presents in a proximity after the switching off of the interrogation. As there is no energy amplification at the sensing site, the sensing response is considerably weak. It is difficult to directly evaluate the signal without processing. The instrument for wireless and passive SAW sensors is distinct from the instrument for other type of sensors. It must contain wireless interrogating, receiving and signal processing functionalities.In this program, we have intensively researched on the principles and schemes of wireless and passive SAW sensing including the implementation of the passive sensor array. We have analyzed the forming and characterizing of the sensing signal and designed the signal processing. All the research contributes to the design and the development of wireless and passive SAW sensor arrays and the digital instrument in a virtual instrument fashion. The sensor array is implemented either by using SAW resonators identified by frequency-division codes or exploiting SAW resonators accompanied with delay lines identified by mixed codes of frequency-division and time delay. Based on the analysis of the time-domain responses of SAW resonators to the wireless interrogation, the digital signal processing techniques for passive SAW sensing signal with considerably low signal-to-noise ratio are designed and built in the virtual instrument. The instrument may interrogate 15 passive SAW resonator sensors with a wireless detection distance greater than while the interrogating power is at 30 or with a wireless detection distance greater than while the interrogating power is at 20 . When detecting temperature, the measurement error is within . The instrument can also be applied for the sensing array consisting of SAW resonators and delay-lines without any further hardware modification. In this case, the number of sensing elements in an array system is not restricted.

将声表面波元件本身具有的电、声信号处理功能，结合进声表面波传感器，使其能被激励信号选择激励产生传感输出；同时激励源经天线发射激励信号，传感器的天线接收并耦合进换能器产生声表面波而得到传感输出，输出同样由天线发射。用这样的传感器可构成传感元之间无连线，不需要电源，非接触读取输出的阵列传感器。它可以不受限制地在空间分布，适用于各种工程结构和应用环境，也可植入工程材料中形成智能敏感材料。这种技术适用于各种声表面波传感器用以构成分布式和集成化传感阵列，是一种全新的分布传感技术、多传感器系统技术实现方法。