Voltage Multiplier Topologies Comparison for UHF RFID Applications

Due to the limited power that can be obtained from the RF field, UHF RFID systems need to be able to operate with few dozens of µW. Therefore, an efficient voltage multiplier is a key element to obtain tags able to operate at long ranges and with advanced functionalities. The objective of this work, is obtaining a topology able to provide the required operative voltage with the minimum RF input power. The highest possible sensitivity and efficiency will provide the longest range, which is a critical parameter in UHF RFID applications. Factors such as transistor and diode size and number of stages have been analyzed in order to obtain the maximum sensitivity and power conversion efficiency (PCE). In this paper, four voltage multipliers are developed and analysed, following the same methodology using a 180µm process. Sensitivities as high as -12dBm and PCEs up to 16% with a load of 7µA are obtained in the Schottky multiplier, during simulation of an input power range from - 15dBm to -8dBm.