Ultrawideband Microwave Sensing and Imaging Using Time-Reversal Techniques: A Review

Mehmet Emre Yavuz,Fernando L Teixeira

doi:10.3390/rs1030466

Mehmet Emre Yavuz, Fernando L Teixeira

Open Access

https://doi.org/10.3390/rs1030466

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Abstract

This paper provides an overview of some time-reversal (TR) techniques for remote sensing and imaging using ultrawideband (UWB) electromagnetic signals in the microwave and millimeter wave range. The TR techniques explore the TR invariance of the wave equation in lossless and stationary media. They provide superresolution and statistical stability, and are therefore quite useful for a number of remote sensing applications. We first discuss the TR concept through a prototypal TR experiment with a discrete scatterer embedded in continuous random media. We then discuss a series of TR-based imaging algorithms employing UWB signals: DORT, space-frequency (SF) imaging and TR-MUSIC. Finally, we consider a dispersion/loss compensation approach for TR applications in dispersive/lossy media, where TR invariance is broken.

Highlights

Remote sensing systems in the microwave and millimeter wave frequency ranges provide unique capabilities for detection and imaging of obscured targets
We have provided a summary of some time-reversal techniques for UWB microwave remote sensing
We have focused most of the discussion on imaging scenarios consisting of obscured discrete targets in continuous random media, TR techniques are applicable to many other remote sensing scenarios, as surveyed in the Introduction

Summary

Introduction

Remote sensing systems in the microwave and millimeter wave (mm-wave) frequency ranges provide unique capabilities for detection and imaging of obscured targets. Recent results have shown that multipath can be exploited to improve detection and imaging capabilities in sensing scenarios (or, somewhat equivalently, channel capacity in wireless communication scenarios) [2, 3] One such technique is time-reversal (TR) [4,5,6,7], which exploits multipath components in the intervening media to achieve superresolution, i.e., resolution that beats the classical diffraction limit. As long as some of the diverging wave components are redirected toward the TRA, the effective aperture length increases (ae > a) resulting in a better focusing resolution than the homogeneous medium case (superresolution) [4].

Numerical Results

Time-Domain DORT

Space-Frequency TR Imaging

Results

TR-MUSIC

Conclusions