Prof. Fernando L. Teixeira

Microwave Imaging of Obscured Objects in Random Inhomogeneous Media is of Interest in Numerous Applications. Time-reversal (TR) Imaging Techniques involve the Retransmission of Signals acquired by a Set of Transceivers in a Time-reversed Fashion to exploit the TR Invariance of the Wave Equation. TR yields Super-resolution & Statistical Stability Properties, which are not available in most Imaging Methods.

 

In this Presentation, we review TR-based Signal Techniques applied to Ultra-wideband (UWB) Microwave Imaging of Objects embedded in Random Inhomogeneous Media. We first considered “Signal-space” TR Methods that Multi-static Data Matrices obtained from Antenna Arrays. These methods employ an Eigenvector Decomposition of the TR Operator across the Available Bandwidth to provide the Required Time-domain Excitation Signals to be retransmitted by the Antenna Array for Selective Focusing of Multiple Targets. Next, we describe “Null-space” Methods that utilize the Eigenvectors associated with the (Approximate) Null Space of the TR Operator to obtain Desired Target Images.

 

We then discuss the Use of Compensation (Inverse) Filters as a means to Extend TR Techniques to Lossy Media, where the TR Invariance is broken. This is followed by a Discussion of the Relation between the Excitation Bandwidth of the Signal & the statistical stability of the Images in Random Media. Finally, we provide some Illustrative Applications including Ground Penetrating Radar, Medical Imaging & Through-wall Imaging.