Harmonic UHF RFID Ranging with 50-Micron Accuracy and 1-kHz Sampling Rate

Abstract

Highly accurate indoor localization with unique item-level identification (ID) is a critical capability for Internet of Things (IoT), structure integrity monitoring and haptic robotic feedback. Current precision tracking approaches are limited by either accuracy or unique ID of multiple objects. The conventional ultra-high-frequency (UHF) RF identification (RFID) system attaches a passive transponder tag to each object of interest and modulates the backscattered signal with an item-level unique ID, which also serves as the signal isolation against ambient refection. However, the present RF frequency strategy introduced a high noise floor, and could achieve ranging accuracy only in the cm level. In this paper, we analyzed the noise and interference sources and formulated the corresponding countermeasures to achieve a harmonic UHF RFID system with the ranging accuracy around or less than 50 microns and the sampling rate up to 1 kHz. As UHF signals have reasonable penetration in many dielectric media, we also demonstrated our precision tracking scheme in water and construction sands.