High-overtone bulk acoustic resonator as passive ground penetrating RADAR cooperative targets

Abstract

RAdio-frequency Detection And Ranging instruments—RADARs—are widely used for applications aimed at measuring passive target velocity or ranging for various metrology applications such as ground position and localization. Within the context of using piezoelectric acoustic passive sensors as cooperative targets to RADARs probed through a radiofrequency link, this paper reports on investigating the compatibility of narrowband resonator architectures with the classical operation mode of wideband RADAR instruments. Since single mode resonators are hardly compatible due to the limited bandwidth of their spectrum, the investigation has been extended to High-overtone Bulk Acoustic Resonator (HBAR) whose comb of modes appears appropriate to the use with RADAR instruments. This analysis leads to consider HBARs as delay lines providing a comb of echos in the time domain rather than through the usual frequency comb considerations. Experimental measurements of HBAR responses are demonstrated using Ground Penetrating RADAR instruments fitted with a variety of antennas, and thus, operating in various frequency ranges, as well as the identification of the device temperature through the echo time delay computed as the cross correlation maximum position. Finally, the use of such cooperative targets for single reflector identification within a clutter of reflectors is theoretically considered with the proposal of a Finite-Difference Time-Domain-based simulation method encompassing both passive dielectric reflectors and the contribution of buried passive acoustic sensors.