Wireless Power Transmission to a Buried Sensor in Concrete

The feasibility of sending wireless power to a buried sensor antenna within concrete was studied. A receive patch rectenna with 75.8% conversion efficiency was designed for operation at 5.7 GHz. The received DC power at the rectenna was measured within dry and wet concrete samples with various cover thicknesses and air-gaps. For the rectenna buried within 30 mm of the concrete, the received DC power was 10.37 mW, which was about 70% of the received DC power in free-space.

I. Introduction

Routine evaluation and prediction of the health of civil infrastructures, such as bridges, overpasses, and buildings is crucial to ensure public safety. Currently, the health monitoring of infrastructures is done by expensive and labor-intensive procedures such as spot checking [1] and ground penetrating radar (GPR) [2]. An alternative is to use distributed wireless sensors to perform structural health monitoring [3]–[5]. Researchers have also proposed the use of wireless embeddable sensors for infrastructure health monitoring [6], [7]. Such sensors must be installed within the structure itself during the construction phase of the infrastructure. Wireless embedded sensors are low cost and are more reliable than conventional wired sensors since the presence of wires within an infrastructure creates the possibility of loss of connection due to crack and corrosion. Power to the sensor may be supplied using inductive near-field technique [8] or radiated far-field technique [9]. For low data rate, RFID tag type sensors energizing the sensor using inductive coupling is a cheap and attractive option [10], [11]. A reader or interrogator is generally used to energize and interrogate the sensor. A passive tag type sensor does not collect or transmit any data unless energized and queried by an interrogator.