Design of a surface acoustic wave resonator for sensing platforms

Acoustic wave devices are an attractive technology for use in sensors since acoustic waves present high sensibilities to external parameters in terms of phase velocity and damping. This technology is very interesting in environments such as Internet of Things, where low power consumption is a central requirement. The main drawback of this technology concerns the application and the reliability of the RF signal powering the sensor that makes necessary the use of virtual network analyser or spectrum analyser. Although in literature examples of acoustic wave devices used with external antennas have been discussed, to the best of our knowledge, at the state of the art acoustic devices integrated with an antenna have not been reported yet. This paper will discuss the possibility to realize a wearable, compact remote sensor, totally passive, fully integrated with the antenna. The wearable sensor is based on a Surface Acoustic Wave (SAW) resonator designed to operate at 800 MHz and realized on a flexible and biocompatible polymeric substrate, made of Polyethylene naphthalate (PEN). The SAW resonator consists of a pair of reflecting gratings, defining the acoustic cavity, and an interdigital transducer (IDT) placed at the centre of the cavity. The distributed feedback cavity shows a high Qfactor Q ≈ 2×105 when 200 reflectors are considered.