Friedt J-M, Droit C, Martin G, Ballandras S
SENSeOR, 32 Avenue de l'Observatoire, 25044 Besançon, France.
Rev Sci Instrum. 2010 Jan;81(1):014701. doi: 10.1063/1.3267311.
Monitoring physical quantities using acoustic wave devices can be advantageously achieved using the wave characteristic dependence to various parametric perturbations (temperature, stress, and pressure). Surface acoustic wave (SAW) resonators are particularly well suited to such applications as their resonance frequency is directly influenced by these perturbations, modifying both the phase velocity and resonance conditions. Moreover, the intrinsic radio frequency (rf) nature of these devices makes them ideal for wireless applications, mainly exploiting antennas reciprocity and piezoelectric reversibility. In this paper, we present a wireless SAW sensor interrogation unit operating in the 434 MHz centered ISM band--selected as a tradeoff between antenna dimensions and electromagnetic wave penetration in dielectric media--based on the principles of a frequency sweep network analyzer. We particularly focus on the compliance with the ISM standard which reveals complicated by the need for switching from emission to reception modes similarly to radar operation. In this matter, we propose a fully digital rf synthesis chain to develop various interrogation strategies to overcome the corresponding difficulties and comply with the above-mentioned standard. We finally assess the reader interrogation range, accuracy, and dynamics.
利用声波装置监测物理量，可以通过利用波特性对各种参数扰动（温度、应力和压力）的依赖性来有利地实现。表面声波（SAW）谐振器特别适合此类应用，因为其谐振频率直接受这些扰动影响，从而改变相速度和谐振条件。此外，这些装置固有的射频（rf）特性使其成为无线应用的理想选择，主要利用天线互易性和压电可逆性。在本文中，我们基于扫频网络分析仪的原理，展示了一种工作在以434 MHz为中心的ISM频段的无线SAW传感器询问单元，该频段是在天线尺寸和电磁波在介质中的穿透性之间进行权衡后选定的。我们特别关注符合ISM标准的情况，由于需要像雷达操作一样从发射模式切换到接收模式，这一过程显得很复杂。在这个问题上，我们提出了一个全数字射频合成链，以开发各种询问策略来克服相应困难并符合上述标准。我们最终评估了读取器的询问范围、精度和动态性能。
