Triet Tu Le

Efficient Far-Field Radio Frequency Energy Harvesting for Passively Powered Sensor Networks

An RF-DC power conversion system is designed to efficiently convert far-field RF energy to DC voltages at very low received power and voltages. Passive rectifier circuits are designed in a 0.25 mum CMOS technology using floating gate transistors as rectifying diodes. The 36-stage rectifier can rectify input voltages as low as 50 mV with a voltage gain of 6.4 and operates with received power as low as 5.5 muW(22.6 dBm). Optimized for far field, the circuit operates at a distance of 44 m from a 4 W EIRP source. The high voltage range achieved at low load current make it ideal for use in passively powered sensor networks.

Piezoelectric micro-power generation interface circuits

New power conversion circuits to interface to a piezoelectric micro-power generator have been fabricated and tested. Circuit designs and measurement results are presented for a half-wave synchronous rectifier with voltage doubler, a full-wave synchronous rectifier and a passive full-wave rectifier circuit connected to the piezoelectric micro-power generator. The measured power efficiency of the synchronous rectifier and voltage doubler circuit fabricated in a 0.35-/spl mu/m CMOS process is 88% and the output power exceeds 2.5 /spl mu/W with a 100-k/spl Omega/, 100-nF load. The two full-wave rectifiers (passive and synchronous) were fabricated in a 0.25-/spl mu/m CMOS process. The measured peak power efficiency for the passive full-wave rectifier circuit is 66% with a 220-k/spl Omega/ load and supplies a peak output power of 16 /spl mu/W with a 68-k/spl Omega/ load. Although the active full-wave synchronous rectifier requires quiescent current for operation, it has a higher peak efficiency of 86% with an 82-k/spl Omega/ load, and also exhibits a higher peak power of 22 /spl mu/W with a 68-k/spl Omega/ load which is 37% higher than the passive full-wave rectifier.

Novel power conditioning circuits for piezoelectric micropower generators

Low power devices promote the development of micropower generators (MPGs). This paper presents a novel power conditioning circuit (PCC) that enables maximum power extraction from a piezoelectric MPG. Synchronous rectification (SR) is employed to improve the PCC efficiency. A simplified model of the piezoelectric generator is developed for simulation. Performance of the proposed PCC is verified by PSpice simulation and experimental results. A maximum output power of 18.8 /spl mu/W has been extracted from a single piezoelectric MPG. Arbitrary waveform generator representation (AWGR) of the flexing piezoelectric membrane is also presented. The hardware AWGR enables research on the PCC without the need for the actual MPG heat engine or bulge tester used to flex the piezoelectric membrane, and also demonstrates the feasibility of cascading many MPGs to extract additional power.

Piezoelectric power generation interface circuits

New power conversion circuits are presented that interface to a piezoelectric power generator. Measured results are presented for a synchronous rectifier with voltage doubler connected to the piezoelectric membrane. The power efficiency is 88% and the output power is 2.5 /spl mu/W with a 100 k/spl Omega/, 100 nF load. An improved circuit based on the synchronous rectifier achieves 1.4 V, 20 /spl mu/W and more than 90% efficiency.

Efficient Far-Field Radio Frequency Power Conversion System for Passively Powered Sensor Networks

An RF-DC power conversion system is designed in a 0.25mum CMOS technology to efficiently convert RF energy to DC voltages. The rectifier has 60% efficiency and can rectify input voltages as low as 50mV by using floating gate transistors as rectifying diodes. For distances of 15 meters, 1 volt DC is measured with 0.3muA load current at 906MHz. The system operates with 5.5muW (-22.6 dBm) received power, corresponding to 42 meters operating distance with a 4W source