Piezoelectric radiofrequency transducers as passive buried sensors

S Alzuaga,J.-P Simonnet,T Laroche,S Ballandras,M Griselin,T Baron,G Martin,J.-M Friedt,T Rétornaz,É Lebrasseur

doi:10.1080/10589759.2012.674524

Abstract

We demonstrate that single-piezoelectric substrate-based acoustic transducers act as ideal sensors for probing with various RADAR strategies. Because these sensors are intrinsically passive devices working in the radiofrequency range, they exhibit improved interrogation range and robustness with respect to silicon-based radio frequency identification tags. Both wideband (acoustic delay lines) and narrowband (acoustic resonators) transducers are shown to be compatible with pulse-mode and frequency-modulated continuous-wave RADAR strategies, respectively. We particularly focus on the ground-penetrating RADAR (GPR) application in which the lack of local energy source makes these sensors suitable candidates for buried applications in roads, building or civil engineering monitoring. A novel acoustic sensor concept – high-overtone bulk acoustic resonator – is especially suited as sensor interrogated by a wide range of antenna set, as demonstrated with GPR units working in the 100 and 200 MHz range.

Highlights

Ground-penetrating RADAR (GPR) is a classical tool for nondestructive observation of buried structures and interfaces, both for geophysical purposes or civil engineering [1] and road-ageing assessment [2 –4]
We focus on the ground-penetrating RADAR (GPR) application in which the lack of local energy source makes these sensors suitable candidates for buried applications in roads, building or civil engineering monitoring
Since such devices will only work in a given restricted frequency range compatible with a given RADAR geometry, we extend the demonstration from Surface acoustic wave (SAW) to a novel bulk acoustic wave resonator configuration operating in a wide frequency range and compatible with multiple RADAR antenna geometries

Summary

Introduction

Ground-penetrating RADAR (GPR) is a classical tool for nondestructive observation of buried structures and interfaces, both for geophysical purposes or civil engineering [1] and road-ageing assessment [2 –4]. Various RADAR strategies are used for monitoring liquid and granular media level [5,6] or target velocities In such uses, the measurement is limited to electromagnetic wave reflection by dielectric permittivity or conductivity interfaces. Surface acoustic wave (SAW) [9] sensors have been demonstrated as transducers for temperature [10,11,12,13,14,15], stress [16], torque [17], pressure [18,19,20] and chemisorption monitoring [21,22,23], as well as for tagging (identification only) applications [24,25,26].

GPR basic principle

SAW delay line basic principle and interrogation strategies

Probing resonators with GPR

Novel resonator design for use with GPR

Conclusion