A fully-integrated CMOS wireless power harvesting system for biomedical applications is reported in this thesis. This system harvests power at 3 to 5-GHz wirelessly and converts the power from RF to DC voltage, enabling the chip to be self-powered. The system consists of an on-chip antenna to capture ambient RF energy, a rectifier that converts RF power to DC, and a digital ring oscillator to demonstrate wireless power harvesting capability....[ Read more ]

A fully-integrated CMOS wireless power harvesting system for biomedical applications is reported in this thesis. This system harvests power at 3 to 5-GHz wirelessly and converts the power from RF to DC voltage, enabling the chip to be self-powered. The system consists of an on-chip antenna to capture ambient RF energy, a rectifier that converts RF power to DC, and a digital ring oscillator to demonstrate wireless power harvesting capability.

The thesis commences with the definition of the system link budget, together with the study of the near/far field antenna operation. Next, the design of the interface impedance between the on-chip antenna and the rectifier is discussed, concluding with the optimal design for antenna radiation gain, antenna impedance, rectifier topologies and number of rectification stages. Two loop antenna structures, a 3-mm x 3-mm chip edge antenna and a 0.90-mm x 0.65-mm inductor based antenna, are designed for chip area efficiency, and their design trade-off and performance are compared. The system is implemented in a 0.13-um UMC CMOS technology.

From the measurement, the power harvesting system is able to power up a 3.2-MHz ring oscillator, an equivalent harvest power of 10+-uW at a distance of 1-cm in air. The short-coming of existing measurement method is discussed, and a novel and accurate measurement technique for self-powering system is proposed. The 3-D radiation pattern of the harvesting system is captured, and the measured result shows good agreement with simulation, demonstrating the capability of the wireless harvesting system and the effectiveness of the proposed measurement technique.