Effects of receiver antenna height and polarization on received signal levels at road level from transmitter antennas set in manhole

We aim to establish a wireless link system employing RFID tags and sensors set in underground facilities that are to be inspected such as manholes. The sensor data, which are contained in the RFID tags or the sensor register, are retrieved from a car that is driven along a road. Outdoor measurements were conducted to design wireless sensor systems. The results show that approximately 10 and 12 dB higher received signal levels are obtained for receiver antenna heights 1.7 m or higher above ground for vertical and horizontal polarization at distances far from the manhole cover (MC), respectively. The received signal levels for vertical polarization are from 7 to 9 dB higher than those for horizontal polarization both near and far from the MC.