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