Dual-polarized RF Tags for Orientation Estimation of Underground Pipelines

Ground Penetrating Radar (GPR) is a non-destructive technique widely used to detect objects such as underground pipelines and cables. The hyperbolic features observed in radar images are commonly used to estimate cylindrical objects' depth and radius. However, generating standard hyperbola requires that the GPR scanning direction be perpendicular to the pipeline's orientation, which is challenging to guarantee in practical field measurements. In this study, we integrate GPR with radio frequency identification (RFID) to estimate the orientation of underground pipelines. We designed a dual-polarized flexible RF tag, with the resonant frequencies depending on the polarization of the incident electromagnetic wave. The tags were tested in both simulation and field experiments to show that they can generate strong resonance in horizontal and vertical polarizations. Subsequently, we analyzed the different structures of tags that affect the resonant frequencies in horizontal and vertical polarizations and thereby can effectively control the resonant frequencies in different polarizations. This innovative approach has potential for applications such as pipeline orientation estimation, offering new solutions in the realm of underground environmental monitoring.