SAW devices as wireless passive sensors

Acoustic Wave Based MEMS Devices, Development and Applications

“…The explosive growth of the telecommunications industry in the recent decades has created a demand for high quality, compact and mobile radio frequency (RF) modules (Reindl et al, 1996). These mobile terminals typically consist of RF integrated circuits (RFICs) and a multitude of passive components.…”

“…These mobile terminals typically consist of RF integrated circuits (RFICs) and a multitude of passive components. Driven by the success of the wireless technology business and marked progress in the submicron semiconductor fabrication techniques, acoustic wave technology has progressed to GHz range in recent years (Reindl et al, 1996). Acoustic wave devices in telecommunications are typically named according their acoustic wave propagation modes; bulk and surface.…”

“…This ingenious idea allowed a method of controlling electronic signals by transforming them into acoustic waves and manipulating the waves using patterns on piezoelectric substrates (Campbell, 1998;Morgan, 1985). Using the basic theoretical description of surface acoustic wave propagation presented by Lord Raleigh and the photolithographic techniques of microelectronics which are capable of fabricating small-size IDTs, a proliferation of radio-frequency (RF) SAW devices have been designed with innovative applications in wireless communications, radar and broadcasting systems (Hunter et al, 2002;Reindl et al, 1996;Weigel et al, 2002). Among examples of fabricated SAW devices are as components in satellite receivers, remote control units, keyless entry systems, television sets to identification tags (Campbell, 1998;Hikita et al, 2000;Springer et al, 1998).…”

“…Other emerging applications of SAW resonators include gas sensors (Sadek et al, 2006), biosensors (Z. Xu, 2009), chemical (Nomura et al, 1998), temperature and pressure sensors (Buff et al, 1997). The significance of these devices in this industry can be measured in numbers by the worldwide production of these devices, where approximately 3 billion acoustic wave filters are used annually, primarily in mobile cell phones and stations (Reindl et al, 1996). One of the most important applications of SAW resonators in telecommunication systems are as oscillators.…”

“…14) is composed of a piezoelectric substrate with thinfilm metallic structures such as IDTs and reflectors deposited on top of the substrate's surface (Reindl et al, 1996). The operating principle of a SAW device is based on the piezoelectric effect where an applied microwave voltage input at the transmitting (input) IDT generates a propagating acoustic wave on the surface of the substrate (Campbell, 1998;Morgan, 1985;Reindl et al, 1996). This propagating acoustic wave in turn produces an electric field localized at the surface which can be detected and translated back into an electrical signal at the output IDT port (Morgan, 1985).…”