A Practical Approach to Underground UHF Channel Characterization

Abstract

Radio frequency identification systems (RFID) are widely used for monitoring and localization of underground infrastructure objects: pipelines, power, and communication networks. Wireless underground sensor networks (WUSN) are the promising application areas that cover a number of fields: agriculture, mining, environmental control, etc. A progress in semiconductor technologies has opened up new opportunities for developing cheap and compact monolithic ultra-high frequency (UHF) receiver and transmitter integrated circuits - basic building blocks of RFID and WUSN systems. Read range (RR), the path loss (PL) and the bit error rate (BER) are the main characteristics of RFID and WUSN communication channel. The dielectric properties of the soil, determined by the composition and moisture, affect the electromagnetic wave (EMW) propagation that leads to significant PL and limits RR. In this work, a practical approach to UHF underground channel characterization, based on the modified Friis model and the vector network measurements is proposed. The modeling and measurements issues are discussed, that are important for the path loss prediction in the soil with different composition and moisture.