Design of RF tags attaching to buried pipes for enhanced detection by GPR

Ground Penetrating Radar (GPR) is a well-received non-destructive technique for the detection of underground utilities, such as water/gas pipes, sewers, power cables, and telecommunication ducts. However, radar signatures of non-metallic pipes are generally weak in certain conditions, for instance when the surrounding soils are attenuative and/or the pipe-soils interface is non-distinguishable from the electromagnetic standpoint. In order to increase the radar visibility of these pipes, attaching Radio-Frequency (RF) tags to them is a useful method. This paper will discuss Bowtie-Omega shaped RF tags. Finite Element Method is used in our modeling, where the electromagnetic characteristics of each tag candidate are computed. Then the tags are buried in a 4.5 m × 3.5 m × 1.5 m tank partly filled with dry sand. A pulsed GPR system is used to conduct B-scans on one side of the tank, and stronger radar signatures are observed when RF tags are buried. Furthermore, the corresponding enhanced frequency domain response of each trace is clearly seen at the designed resonant frequencies, which are not there when tags are not inserted. The resulting enhanced detection due to the existence of the tags is evident.