Higher Sensitivity RF-DC Rectifier for Ultra-Low Power Semi-Active RFID Tags

Abstract

Radio frequency (RF) energy harvesting is the process where energy is captured from the radiated RF signals and converted it to electrical power to supply a very small amount of power to modern electronic devices. This paper presents a RF energy harvester for ultra-low power semi-active UHF radio frequency identification tag applications. The main objective is to solve the semi-active UHF RFID tag limited lifespan issues due to the need for batteries to power its circuitries.In this design, the energy from the radiated RF signals is converted to electrical power by a module known as RF-DC rectifier. The circuit is based on a cross-connected differential-drive CMOS rectifier topology which is implemented in 0.13 μm CMOS standard technology with the input RF power range from -20 dBm to -10 dBm operating in 915 MHz frequency band. To ensure a maximum output voltage is achieved, several simulations based on the optimized matching network components, the variation of transistor sizes and load resistance, and increases the number of rectifier stages are investigated. All the circuit designs and simulations are performed using Orcad Cadance software. The simulated results shown that the optimized impedance matching network and a six-stage cross-connected differential-drive CMOS rectifier circuit able to produces a 1.13 V DC output voltage with an input power of -10 dBm (100 μW) and 1 MΩ load resistance.The results obtained shows that the proposed design can extend the lifetime of semi-active UHF RFID tag, able to eliminate its dependency on battery and make it possible to achieve a batteryless tag. Therefore, can be used to supply electrical power continuously for RFID tag applications.