Abstract
Wireless surface acoustic wave (SAW) sensors have some unique features that make them promising for industrial metrology. Their decisive advantage lies in their purely passive operation and the wireless readout capability allowing the installation also at particularly inaccessible locations. Furthermore, they are small, low-cost and rugged components on highly stable substrate materials and thus particularly suited for harsh environments. Nevertheless, a sensor itself does not carry out any measurement but always requires a suitable excitation and interrogation circuit: a reader. A variety of different architectures have been presented and investigated up to now. This review paper gives a comprehensive survey of the present state of reader architectures such as time domain sampling (TDS), frequency domain sampling (FDS) and hybrid concepts for both SAW resonators and reflective SAW delay line sensors. Furthermore, critical performance parameters such as measurement accuracy, dynamic range, update rate, and hardware costs of the state of the art in science and industry are presented, compared and discussed.
Highlights
The first ideas of using surface acoustic wave (SAW) devices as sensors have already been developed around 40 years ago [1,2,3,4] with a continuous development since for a wide range of application fields
Compared to today’s booming and high-volume SAW and bulk acoustic wave (BAW) filters with an estimated more than 40 billion radio frequency (RF) acoustic filter functions implemented in mobile phones in 2015 [21], SAW-based wireless sensing is still a low-volume professional niche application
This review paper presented the state of the art for wireless SAW readers and provided a guide to choose the appropriate sensor and reader architecture for each application
Summary
The first ideas of using surface acoustic wave (SAW) devices as sensors have already been developed around 40 years ago [1,2,3,4] with a continuous development since for a wide range of application fields. Compared to today’s booming and high-volume SAW and bulk acoustic wave (BAW) filters with an estimated more than 40 billion radio frequency (RF) acoustic filter functions implemented in mobile phones in 2015 [21], SAW-based wireless sensing is still a low-volume professional niche application. This might change in the future: pushed by the fourth industrial revolution, sensor technology for professional metrology applications plays an increasingly important role. SAW sensors have some unique features that make them promising for such application scenarios: their decisive advantage lies in their purely passive operation and the wireless readout capability allowing the installation at inaccessible locations.
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