Date of Award

Spring 1-1-2011

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Electrical, Computer & Energy Engineering

First Advisor

Zoya Popovic

Second Advisor

Dejan S. Filipovic

Third Advisor

Edward Kuester

Fourth Advisor

Regan Zane

Fifth Advisor

Richard Mihran

Abstract

This thesis focuses on a design methodology for low-power non-directional far-field wireless powering. The power receiver consists of one or more antennae which receive plane waves transmitted by the powering source, and deliver the RF power to a rectifying element. The resulting DC power is optimally transferred to the electronic application via a power management circuit. The powering is independent of the electronic application which can include wireless transmission of sensor data.

The design and implementation of an integrated rectifier-antenna at low incident power densities (from 25-200μW/cm2) is presented. Nonlinear source-pull measurements and harmonic balance simulations are used for finding the optimal rectifying device RF and DC impedances for efficient rectification. Experimental results show that an antenna design with a specific complex impedance reaches the highest rectification efficiency. Several examples of the design methodology are shown. In specific, characterization of a linearly polarized rectifying patch antenna at frequency of 1.96 GHz is detailed, with an optimal RF impedance of 137+j149Ω and an optimal DC load of 365Ω resulting in RF to DC conversion efficiency of 63% (simulated) for the rectifier alone and 54% (measured) for the total rectifying antenna. A compact design (eliminating SMA connector) of a dual-polarized rectifier antenna integrated with two rectifiers, one for each polarization is detailed. The complications and issues of combining the powers from the two polarizations are addressed. A analysis of required RF and DC isolation in multiple-rectifier integrated rectifier-antenna is developed and confirmed. Measurement results of a 2.45 GHz integrated rectifier antenna show conversion efficiency of 56% and very small dependance on rotation angle between powering polarization and receiving rectifier antenna (ratio of maximum to minimum power as the antenna is rotated of 1.09).

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