Surface Acoustic Wave Resonators for Wireless Sensor Network Applications in the 433.92 MHz ISM Band

Abstract

Surface acoustic wave (SAW) resonators are low cost devices that can operate wirelessly on a received radio frequency (RF) signal with no requirement for an additional power source. Multiple SAW resonators operating as transponders that form a wireless sensor network (WSN), often need to operate at tightly spaced, different frequencies inside the industrial, scientific and medical (ISM) bands. This requires nanometer precision in the design and fabrication processes. Here, we present results demonstrating a reliable and repeatable fabrication process that yields at least four arrays on a single 4-inch wafer. Each array consists of four single-port resonators with center frequencies allocated inside four different sub-bands that have less than 50 kHz bandwidth and quality factors exceeding 8000. We see promise of standard, low-cost photolithography techniques being used to fabricate multiple SAW resonators with different center resonances all inside the 433.05 MHz–434.79 MHz ISM band and a mere 100 kHz spacing. We achieved that by leveraging the intrinsic process variation of photolithography and the impact of the metallization ratio and metal thickness in rendering distinct resonant frequencies.

Influence of Structural Parameters on Performance of SAW Resonators Based on 128° YX LiNbO3 Single Crystal

“…The resonator presents the advantage of having a high Q value 1364.5, which is essential for fabricating a SAW load sensor with higher sensitivity and a larger sensing range. [23] 1910 659 LiNbO 3 [24] 150 1150 Quartz [25] 433.05-434.79 8000 ZnO/6H-SiC [26] 688 1080 128 • YX LiNbO 3 (this work) 224.85 1364.5…”

A review of piezoelectric MEMS sensors and actuators for gas detection application

“…In more detail, the Rayleigh SAW sensors are creating an out-of-plane elliptically polarized surface wave caused by the acoustic energy near the piezoelectric substrate surface [ 209 ]. The resonant frequency of the SAW devices [ 210 ] is calculated by Eq. ( 2 ): where v is the velocity of the wave for the certain substrate material, and the l is the wavelength.…”

Chemical Sensors Based on Graphene and 2D Graphene Analogs

“…Simultaneously, they have excellent compatibility with integrated circuits and have been widely employed in the field of simulated digital sensing and communication. [ 76 ] The SAW sensors concentrate the signal on the substrate surface. It features a high operating frequency and a high information‐sensitive accuracy.…”