Design of Voltage Multipliers for Maximized DC Generation in Inductively Coupled RFID Tags

This paper presents models, circuit solutions and design procedures for maximized DC generation in inductively coupled RFID tags. An analytical model for the DC generation is derived, and relationships between the received signal in the tag coil antenna and the generated DC supply voltage using a voltage multiplier, based on both passive and active diodes, are presented. Derived from the trade-off between voltage gain in the multiplier and the tag coil at resonance, an equation for the optimum number of multiplier stages to achieve maximized DC generation is presented. Based on the derived equation, design examples are included with two typical tag coil antennas given a specification of the DC supply voltage and current. Also included in this paper is the design of a voltage multiplier based on active diodes implemented and manufactured in AMS 0.35 μm CMOS process. The active diodes are based on a concept of threshold cancellation of MOS diodes and make use of reverse leakage control to achieve full threshold cancellation.