Electromagnetic Time Reversal

Contents

List of Contributors

Preface

About the Companion Website

1 Time Reversal: A Different Perspective

1.1 Introduction

1.2 What is Time?

1.3 Time Reversal or Going Back in Time

1.3.1 Approach 1: Recording of the State of the System Throughout Its Evolution

1.3.2 Approach 2: Use of Expressions that Describe the Evolution of the System as a Function of Time

1.3.3 Approach 3: System Regressing Through Its Own Natural Defining Equations

1.3.4 Time Reversal in the Strict Sense and in the Soft Sense

1.3.5 Schrödinger Equation

1.3.6 Maxwells Equations

1.3.7 Time-Reversal Process: Summary

1.4 Application of Time Reversal in Practice

1.5 Refocusing of Electromagnetic Waves Using Time Reversal

1.5.1 Time-Reversal Cavity

1.5.2 Use of a Limited Number of Sensors

1.5.3 Time Reversal and Matched Filtering

1.6 Applications of Time Reversal in Electrical Engineering

References

2 Time Reversal in Diffusive Media

2.1 Introduction

2.2 Fundamental Properties of Diffusive Media

2.2.1 Understanding and Describing Wave Propagation in Diffusive Media

2.2.2 Statistical Black-Box Modeling

2.3 Time-Reversal Transmissions in Diffusive Media

2.3.1 Self-Averaging and Spectral Coherence

2.3.2 Taking a Broader View: Spatial Speckle and Background Fluctuations

2.3.3 How Accurate are Time-Reversed Fields in Diffusive Media?

2.3.4 Polarization Selectivity

2.3.5 Conversion Efficiency and Power Gain

2.4 Time Reversal for the Generation of Wavefronts

2.4.1 Time-Reversal Dyadic Function

2.4.2 The Burden of a First Radiating Phase

2.4.3 Direct Wavefront Synthesis

2.4.4 Implementing GTR

2.4.5 Retrieving Free-Space Conditions: Experimental Results

2.4.6 An Original Application: Imaging Apertures in a Metallic Shield

2.5 Final Considerations

References

3 From Electromagnetic Time-Reversal Theoretical Accuracy to Practical Robustness for EMC Applications

3.1 On the Interest of Time Reversal in the EMC Context

3.2 TR in Transmission Line (TL) Networks

3.2.1 Transmission Line and Time Reversal

3.2.2 Defect or Fault Detection in Transmission Lines

3.2.3 Time-Reversal Wire Diagnosis

3.2.4 Time-Reversal Wire Diagnosis Examples

3.3 Selective EMC Radiated Immunity

3.3.1 From Open Area to Reverberating Environment for EMTR

3.3.2 Optimization of TR Parameters for the RC Numerical Experiment

3.3.3 EMC Immunity Testing in a Reverberation Chamber

3.4 Towards Realistic EMC Testing

3.4.1 Practical Limitations

3.4.2 Robustness and Statistics

3.5 Conclusion

References

4 Amplification of Electromagnetic Waves Using Time Reversal

4.1 Outline

4.2 Introduction

4.3 Measurements

4.3.1 Experimental Setup

4.3.2 Time Compression

4.3.3 Number of Antennas and Influence of the Bandwidth

4.3.4 Size of the Focal Spot

4.3.5 One-Bit Time Reversal

4.3.6 Aperture

4.4 Theoretical Model

4.4.1 Average Amplitude of the Transient Signal

4.4.2 Gain Obtained Using TR

4.5 Comparison with a Directive Antenna

4.5.1 Comparison with a Directive Antenna

4.5.2 Autosteering Properties of the System

4.6 Discussion

4.6.1 Focusing at Any Location

4.6.2 Obtaining High Resolution and High Q-Factor

4.6.3 Radar Imaging

4.7 Conclusion

References

5 Application of Time Reversal to Power Line Communications for the Mitigation of Electromagnetic Radiation

5.1 Introduction

5.2 Adaptation of Time Reversal to Power Line Communications

5.3 Experimental Study of Radiation Mitigation

5.3.1 Measurement Campaign

5.3.2 Data Processing

5.4 Results and Statistical Analysis

5.4.1 Measurement Example

5.4.2 Statistical Analysis

5.5 Conclusion

References

6 Application of Electromagnetic Time Reversal to Lightning Location

6.1 Introduction

6.2 Overview of Lightning Location Techniques

6.2.1 Cloud-to-Ground Lightning

6.2.2 Magnetic Direction Finding

6.2.3 Difference in Time of Arrival (DToA)

6.3 EMTR and Lightning Location

6.3.1 Description of the Method

6.3.2 Principle of Operation

6.3.3 Finite Ground Conductivity

6.3.4 Relation between EMTR and Other Lightning Location Techniques

6.4 Practical Implementation Issues

6.4.1 Modeling of Complex Dissipative Medium

6.4.2 Simulation Resources

6.4.3 Data Storage and Communication Resources

References

7 Electromagnetic Time Reversal Applied to Fault Location in Power Networks

7.1 Chapter Overview

7.2 Introduction

7.3 Summary of Existing Fault Location Methods

7.3.1 Impedance-Based Methods

7.3.2 Traveling Wave-Based Methods

7.3.3 Knowledge-Based Methods

7.4 Application of Electromagnetic Time Reversal (EMTR) for the Fault Location Problem

7.4.1 Basic Concepts and Time-Reversal Invariance of Telegraphers Equations

7.4.2 EMTR-Based Fault Location Method

7.5 The Issue of Losses: Back-Propagation Models

7.5.1 Inverted-Loss Back-Propagation

7.5.2 Lossless Back-Propagation

7.5.3 Lossy Back-Propagation

7.5.4 Comparison of the Back-Propagation Models

7.6 Experimental Validation

7.7 Case Studies and Performance Evaluation

7.7.1 Inhomogeneous Network Composed of Mixed Overhead Coaxial Cable Lines

7.7.2 Series-Compensated Overhead Transmission Lines

7.7.3 Radial Distribution Network: IEEE 34-Bus Test Distribution Feeder

7.7.4 Multiterminal HVDC Links

7.8 Conclusion

References

Index

EULA