Remote control of SAW resonators using a frequency-modulation-based interrogation strategy

Within the context of probing acoustic wave resonators acting as wireless, passive sensors, we present a strategy for wireless monitoring of surface acoustic wave (SAW) resonators using a frequency modulation based interrogation method. The basic principle is the conversion of frequency modulation to amplitude modulation by the resonator through its S
₁₁
transfer function. An ARM-7 based central processing unit synchronizes the narrow-band probing pulse emission, emission to reception switching, data sampling and data processing. A closed loop control keeps the emitted carrier frequency at the resonance frequency of the sensor: we demonstrate a resolution of 2 Hz on the resonance frequency identification at 1 s integration time, limited by this proportional feedback loop.