A low cost approach to acoustic filters acting as GPR cooperative targets for passive sensing

Ground Penetrating RADAR (GPR) is a classical sub-surface analysis tool widely used in civil engineering and environmental investigations. Currently limited to monitoring passive buried dielectric and conductivity interfaces, the instrument is perfectly suited to probe cooperative targets made of piezoelectric substrates designed to convert the incoming electromagnetic wave to an acoustic wave. The surface acoustic wave (SAW) velocity is strongly dependent on the physical environment of the transducer, allowing for sensing such quantities as temperature, stress or the presence of chemical compounds. In order to demonstrate the compatibility of SAW sensors acting as cooperative targets probed by GPR, we investigate the use of widely available commercial SAW filters for sensing purposes. Dedicated software for recording the Malå ProEx GPR signal and digital signal processing algorithms for extracting the physical quantity are demonstrated.