RFID tag load impedance measurement using backscattered signal

Radio frequency identification is a pervasive technology used for many different purposes. This paper presents a unique technique to evaluate tag's loads impedance without modifying its electronics. In this in-situ technique, no external measuring equipment such as vector network analyzer was directly connected with the tag. The complex back scattered signal together with simulated tag antenna's impedance and gain were used to extract its load impedance. The evaluated load impedance showed unified effect of the tag electronics and board parasitics.