High Performance Lamb Wave Resonator Operating in the 900 MHz ISM Band for Wireless Sensing Applications

Abstract

Precision agriculture systems enabled by passive, wireless, subsurface soil sensors can provide high resolution data on soil conditions and increase crop yield. These frequency-coded sensor nodes are composed of an antenna, acoustic resonator and capacitive soil moisture sensor. Here, a high performance Al <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.7</inf> Sc <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.3</inf> N Lamb-wave resonator (LWR) for operation in the 902-928 MHz industrial, scientific, medical (ISM) band is fabricated. Its figure of merit is 37% larger than state-of-the-art LWR at similar frequency. The LWR is integrated with a capacitive moisture sensor and its frequency tuning capabilities are demonstrated. A sensitivity of 65 kHz at interrogation ranges of up to 150 m is determined.