Wireless Power Transmission

Resonating into the Future

Tony Xiao, Chris Jereza, Javier Pinedo

Advisor: Dr. Sakhrat KhizroevWinter/Spring 2008

Concept and Application

Intended as a proof-of-concept for remotely powered electrical devices

Uses RF Transmitter and Receiver Operates using Ferromagnetic Resonance (FMR) Boasts many advantages over alternate

implementations of wireless power. Many times the range of inductive charge

platforms, mechanically simpler than evanescent wave coupling, safer than direct transmission.

Has great potential for future applications Over $2 Billion USD Projected Annual Earnings

(from PowerCast Estimate)

Ferromagnetic Resonance

Ferromagnetic Materials such as Iron, Nickel and Cobalt have aligned magnetic dipole moments

Flipping of electrons from high and low moments absorbs EM energy when in an external magnetic field

Far more powerful than NMR (3000 times)

Technical design objectives

Primary Goal: Detect notable power absorption in a FM sample

At least 10-20 dBm power absorption Sufficient SNR for practical detection Frequency of RF: 0.5 to 3.0 GHz Cutoff Frequency: Under 100 khz Magnetic Field Strength: Under 1 Tesla

(10,000 Gauss)

Test Assembly High Level Design

CurrentSource

Voltmeter

Ferromagnetic Sample Core

Source Coil Region

Sample Center

Detector Coil Region

Coil Center

Reference Signal

Thermocouple

Sample Offset

SpectrumAnalyzer

SpectrumAnalyzer

Signal Generator

Voltmeter

Noise-Elimination Connector

RG-8/u Coaxial Cable

N-type (Male) connector Modified N-

type (Female) connector

Connection to Test Assembly

Grounding Line

Faraday Caging

Modified N-type Connector for noise elimination: Over 90% decreased

noise compared to direct connection

Technical challenges

Accurately modeling/predicting FMR Determining ideal test assembly

specifications, resonance parameters. Eliminating Noise in Transmission Line Adequately shielding main test assembly Designing compatible low-noise connector

for assembly and cables Eliminating the need for resonant cavity

Project Roles

Tony Xiao: Theoretical High-Level Design Manager and Inter-university Liaison System Testing and Analysis Chris Jereza: RF Connector Design, Construction Interference Reduction Design Component Procurement Javier Pinedo: Test Assembly Construction and Calibration Webmaster and Documentation System Testing

Design Considerations and Future Experiments

This was a Proof of Concept Cost is relatively low per-unit Implementing a voltage converter Implementing Advanced Detection Methods:

Giant/Tunneling Magnetoresistive elements Testing more Materials: Permalloy,

Samarium-Nickel Alloys. Feasibility studies for system Nanoscaling

Test Results

Peak absorption resonance detected at Freq: 1064MHz

Absorption: Approx from -34 to -47 dbm. (398nw -> 20nw. 3780nw absorbed). Approx 95% efficiency.

Estimated SNR: Approx 2.51 x 10^10 Peak absorption at 3800 Gauss external field Optimal test assembly coil specifications: 70 turn

end regions, 57 turn detection region, with 10.76mm diameter.

Material: Magnetic Iron, 10mm Diameter

Baseline Readings

NoExternal Field

Iron Sample

Non-Magnetic Sample Baseline

Baseline Readings

3800 GaussExternal Field

Iron Sample

5000 GaussExternal Field

Iron Sample

Data Analysis

5000 GaussVs

No Field

3800 GaussVs

No Field

Data Analysis

Area of interest, 3800 Gauss Maximum absorption at 1064

MHz Approx from -34 to -47 dbm.

(398nw -> 20nw. 3780nw absorbed).

Matches precisely with calculation: f = (У/2π)*β

У = 1.758 * 10^10 (1/s*T) (Gyromagnetic Ratio of Iron)

B = 3800 Gauss = 0.38T (Field) Result: f = 1063.2mHz

Summary

Achieved excellent results with a simple test assembly, further strengthening results

Confirmed 95% absorption at 1065 mHz and optimal conditions in agreement with theory

Verified feasibility of overall system scheme Potential for continuing study with more

advanced detection and conversion methods A successful test of a new approach to an

emergent technology field