Design of Energy Harvester Module with a Low RF Power Input for UHF RFID Tag

Abstract

An UHF RFID system is required to be able to operate at long range coverage, typically at 1-4 m. As a result, the RF signal power received at RFID Tag is very low, typically at -10 dBm. Moreover, practically most of commercially used RFID Tag is passive, which means that it solely relies on the RF signal transmitted from the RFID reader as the power source. Therefore, it is mandatory and critical to design an efficient and low input power RFID Tag system. In this paper, an energy harvester module for UHF RFID Tag, which is able to work at low RF input signal power and generate a stable DC voltage output, is designed. The module is able to operate at a very low RF input power as low as -10 dBm or equal to 100 mVpeak of induced voltage. To obtain such performance, a modified and optimized rectifier-using a Dynamic Vth Cancellation technique, is designed. By using this technique, the rectifier is able to produce an efficient and a high output voltage. Additionally, bandgap reference and voltage regulator circuits are designed to be independent of power supply and temperature variation. As the result, a stable DC power supply output is able to be generated. All the circuits are designed on Silterra 130nm CMOS technology. This technology allows us to design the transistor to operate at a low threshold voltage of 0.1 V, which is very suitable for the application of low input power UHF RFID Tag system.