Time Reversed Electromagnetic Wave

Propagation as a Novel Method of Wireless Power Transfer

Frank Cangialosi, Tyler Grover, Patrick Healey, Tim Furman, Andrew Simon, Steven M. Anlage

1

Current State of Long-Range WPT

Microwave Beaming

Ubiquitous WPT requires greater range than provided by near-field technologies

Current State of Long-Range WPT

Microwave Beaming

XObstructionsPrecise Alignment

Ubiquitous WPT requires greater range than provided by near-field technologies

Current State of Long-Range WPT

Microwave Beaming

ObstructionsPrecise Alignment

Ubiquitous WPT requires greater range than provided by near-field technologies

Current State of Long-Range WPT

Microwave Beaming

ObstructionsSafety HazardPrecise Alignment

Ubiquitous WPT requires greater range than provided by near-field technologies

-15-10-5 0 5

10 15

0 2 4 6 8 10 12 14

Vo

ltage (

mV

)

Time(µs)

Time Reversal

S

T

1. Time Forward StepTarget requests power, source records sona

Target Device

Power Source

A signal-focusing technique

(Enclosed cavity with reflecting walls)

-15-10-5 0 5

10 15

0 2 4 6 8 10 12 14

Vo

ltage (

mV

)

Time(µs)

Time Reversal

S

T

1. Time Forward Step

“Sona"

Gaussian Pulse

(50 ns)

Target requests power, source records sona

Target Device

Power Source

A signal-focusing technique

(Enclosed cavity with reflecting walls)

-15-10-5 0 5

10 15

0 2 4 6 8 10 12 14

Vo

ltage (

mV

)

Time(µs)

Time Reversal

S

T

2. Time Reverse Step

-400-300-200-100

0 100 200 300 400

13.45 13.46 13.47 13.48 13.49 13.5 13.51

Volta

ge (

mV

)

Time(µs)

“Sona"

1. Time Forward StepTarget requests power, source records sona

Source reverses and broadcasts, sona reconstructs on target

Power Source

Target Device

A signal-focusing technique

(Enclosed cavity with reflecting walls)

-15-10-5 0 5

10 15

0 2 4 6 8 10 12 14

Vo

ltage (

mV

)

Time Reversal

S

T

2. Time Reverse Step

-15

-10

-5

0

5

10

15

0 2 4 6 8 10 12 14

Voltage (mV)

Time(µs)

-400-300-200-100

0 100 200 300 400

13.45 13.46 13.47 13.48 13.49 13.5 13.51

Volta

ge (

mV

)

Time(µs)

“Sona"

1. Time Forward StepTarget requests power, source records sona

Source reverses and broadcasts, sona reconstructs on target

Power Source

Target Device

A signal-focusing technique

(Enclosed cavity with reflecting walls)

-15-10-5 0 5

10 15

0 2 4 6 8 10 12 14

Vo

ltage (

mV

)

Time Reversal

S

T

2. Time Reverse Step

-15

-10

-5

0

5

10

15

0 2 4 6 8 10 12 14

Voltage (mV)

Time(µs)

-400-300-200-100

0 100 200 300 400

13.45 13.46 13.47 13.48 13.49 13.5 13.51

Volta

ge (

mV

)

Time(µs)“Reconstruction” pulse

“Sona"

1. Time Forward StepTarget requests power, source records sona

Source reverses and broadcasts, sona reconstructs on target

Power Source

Target Device

A signal-focusing technique

(Enclosed cavity with reflecting walls)

-15-10-5 0 5

10 15

0 2 4 6 8 10 12 14

Vo

ltage (

mV

)

Time Reversal

S

T

2. Time Reverse Step

-15

-10

-5

0

5

10

15

0 2 4 6 8 10 12 14

Voltage (mV)

Time(µs)

-400-300-200-100

0 100 200 300 400

13.45 13.46 13.47 13.48 13.49 13.5 13.51

Volta

ge (

mV

)

Time(µs)“Reconstruction” pulse

“Sona"

1. Time Forward StepTarget requests power, source records sona

Source reverses and broadcasts, sona reconstructs on target

Power Source

Target Device

A signal-focusing technique

(Enclosed cavity with reflecting walls)

Good for rectification

5

Time Reversal for WPT

1

Ray-chaotic environment

Requires… Provides…

2 Reflective surfaces

3

Spatial reciprocity of the wave equation

2 Resilience to obstructions

1 Range (not limited to free space drop-off)

3 Power concentrated at any given location

6

Experimental Setup

+35

0 (mm)

-35

Scattering panels ensure ray chaos

OscilloscopeAWGPSG

Device (on MikroMove)

Power Source (5Ghz, 3dBm)

Wave Generation (TX) Wave Analysis (RX)

MATLAB

7

Spatial Profiling of Reconstruction

+35

0 mm

-35

Target: 0

Constant Velocity0.2 mm/s

7

Spatial Profiling of Reconstruction

+35

0 mm

-35

Target: 0

Constant Velocity0.2 mm/s

7

Spatial Profiling of Reconstruction

+35

0 mm

-35

Target: 0

Constant Velocity0.2 mm/s

7

Spatial Profiling of Reconstruction

+35

0 mm

-35

Target: 0

Constant Velocity0.2 mm/s

8

Spatial Profiling of Reconstruction

V (x) = a ·����sinc

✓x+ c

b

◆����+ d

x

V (x)

8

Spatial Profiling of Reconstruction

V (x) = a ·����sinc

✓x+ c

b

◆����+ d

x

V (x)

8

Spatial Profiling of Reconstruction

Background noise

V (x) = a ·����sinc

✓x+ c

b

◆����+ d

x

V (x)

8

Spatial Profiling of Reconstruction

Background noise

V (x) = a ·����sinc

✓x+ c

b

◆����+ d

x

V (x)

9

Targeting a Moving Receiver

0

0.5

1

1.5

2

2.5

3

3.5

0 20 40 60 80 100 120 140

Peak-

To-P

eak

Volta

ge (

V)

Time (s)

V(t)

“Refresh” the sona before it gets stale

9

Targeting a Moving Receiver

0

0.5

1

1.5

2

2.5

3

3.5

0 20 40 60 80 100 120 140

Peak-

To-P

eak

Volta

ge (

V)

Time (s)

V(t)

“Refresh” the sona before it gets stale

9

Targeting a Moving Receiver

0

0.5

1

1.5

2

2.5

3

3.5

0 20 40 60 80 100 120 140

Peak-

To-P

eak

Volta

ge (

V)

Time (s)

V(t)

“Refresh” the sona before it gets stale

9

Targeting a Moving Receiver

0

0.5

1

1.5

2

2.5

3

3.5

0 20 40 60 80 100 120 140

Peak-

To-P

eak

Volta

ge (

V)

Time (s)

V(t)

“Refresh” the sona before it gets stale

9

Targeting a Moving Receiver

0

0.5

1

1.5

2

2.5

3

3.5

0 20 40 60 80 100 120 140

Peak-

To-P

eak

Volta

ge (

V)

Time (s)

V(t)

“Refresh” the sona before it gets stale

“Dead” time

9

Targeting a Moving Receiver

0

0.5

1

1.5

2

2.5

3

3.5

0 20 40 60 80 100 120 140

Peak-

To-P

eak

Volta

ge (

V)

Time (s)

V(t)

“Refresh” the sona before it gets stale

“Dead” time

10

Targeting a Moving Receiver

0

0.5

1

1.5

2

2.5

3

3.5

0 20 40 60 80 100 120 140

Peak-

To-P

eak

Volta

ge (

V)

Time (s)

V(t)

“Refresh” the sona before it gets stale

0

0.5

1

1.5

2

2.5

3

3.5

0 20 40 60 80 100 120 140

Peak-

To-P

eak

Volta

ge (

V)

Time (s)

V(t)

Experimental Results

Potential WPT System

Supplier searches for participating devices (which may or may not have charge)

Steady State

Initialization

Small fraction of power reflected by device, allowing supplier to find new location

Talk Session 5 Friday,17:45

(Selective Collapse of Nonlinear Time Reversed Electromagnetic Waves)

12

Limitations And Future Work

Transfer efficiencyUse multiple channels

Environmental lossesInvestigate and mitigate

Dead timeUse dedicated hardware TX and calculate new sona simultaneously

These limitations are dependent on our lab equipment, they are not fundamental limitations of the technique

13

Summary

TimeReversal

is a promising new basis for long-range WPTcan transmit energy to receivers in motiondoes not require the receiver to be powered

Talk Session 5 Friday,17:45

(Selective Collapse of Nonlinear Time Reversed Electromagnetic Waves)

Poster Session 2 Friday,14:40

(Time Reversed Wave Propagation as a Novel Method of WPT)

frank@cs.umd.eduanlage@umd.edu