A High-Gain Power-Matching Technique for Efficient Radio-Frequency Power Harvest of Passive Wireless Microsystems

This paper proposes a transformer power-matching and gain-boosting technique to improve the efficiency of power harvesting of passive wireless microsystems. The proposed method utilizes a step-up transformer inserted between the antenna and voltage multiplier of passive wireless microsystems to perform both impedance transformation for power matching and voltage amplification prior to rectification. The series resistance of the primary winding is minimized using multiple metal layers connected using vias, while the width of the spiral of the secondary winding is made much smaller as compared with that of the primary winding to maximize the turn ratio and minimize its shunt capacitive losses. The detailed analysis of the proposed method and simulation results from Spectre of Cadence Design Systems are presented. The proposed power-matching and gain-boosting network, together with voltage multipliers, has been implemented in TSMC 0.18-m 1.8-V six-metal CMOS technology with thick-metal options. For the purpose of comparison, an LC-power-matching and gain-boosting network with the identical voltage multiplier has also been implemented on the same chip. Measurement results demonstrate that the proposed transformer power-matching and gain-boosting technique greatly improves the power sensitivity and efficiency as compared with widely used LC matching approaches.