Auto-tuning in passive UHF RFID tags

This paper presents a matching system which enhances compatibility of UHF RFID tags. It provides constant performance in every frequency band used in different countries. The bases of automatic tuning are presented here as well as a system architecture based on two PMOS capacitors. Simulations results from a prototype designed in a 0.18μm CMOS technology show that input power for all the bandwidth (860MHZ-960MHZ) is up to 3dB better with an auto-tuning system.