Saptarshi Mukherjee

Target Localization using Microwave Time Reversal Mirror in Reflection Mode

Time-reversal (TR) focusing is based on the fact that when a wave solution is reversed in time and back propagated, it focuses back at the source. TR techniques using microwave measurements have proved to be promising for radar detection and defect imaging in nondestructive evaluation of dielectric samples. This paper presents a TR technique for target detection and localization applications using far-field microwave measurements in reflection mode. Simulation results investigate the feasibility and robustness of this approach and determine the limits of this technique. Experimental results based on reflection mode measurements validate the approach for the detection of source and closely spaced multiple dielectric targets.

NDE of composite structures using microwave time reversal imaging

Composite materials are being increasingly used to replace metals, partially or completely, in aerospace, shipping and automotive industries because of their light weight, corrosion resistance, and mechanical strength. Integrity of these materials may be compromised during manufacturing or due to impact damage during usage, resulting in defects such as porosity, delamination, cracks and disbonds. Microwave NDE techniques have the ability to propagate through composite materials, without suffering much attenuation. The scattered fields depend on the dielectric properties of the medium, and hence provide information about the structural integrity of these materials. Time Reversal focusing is based on the fact that when a wave solution is reversed in time and back propagated it refocuses back at the source. This paper presents a model based parametric study of time reversal principles with microwave data in composite materials. A two dimensional FDTD model is developed to implement the forward and time rever...

Microwave time reversal mirror for breast tumor detection

Time reversal focusing is based on the reciprocity property of the wave solution. The time reversed fields back-propagate to focus back at the source. The transmitting and receiving antenna array utilized for time reversal are collectively termed as the time reversal mirror (TRM). This paper deals with the design of a microwave time reversal mirror for detection of breast tumors. Time reversal antennas are designed and used in a pulsed time domain system to obtain the scattered fields from targets. Time reversal of the processed fields can be back-propagated in a FDTD simulation model to obtain potential tumor locations.

Design of a microwave time reversal mirror for imaging applications

This paper presents a design of microstrip transmitting and receiving antennas to be used for time reversal ultra-wideband imaging applications. The transmitter and receiver arrays are together known as a time reversal mirror (TRM). Based on the properties of time reversal and its imaging applications, an antipodal Vivaldi antenna and a monopole antenna are proposed for the transmitter and receiver designs, respectively. Simulation and measurement results demonstrate the efficiency of the antennas for a time reversal mirror. The overall system is demonstrated for source and target imaging applications.

Differential Geometry Based Model for Eddy Current Inspection of U-Bend Sections in Steam Generator Tubes

The modeling of U-Bend segment in steam generator tubes for predicting eddy current probe signals from cracks, wear and pitting in this region poses challenges and is non-trivial. Meshing the geometry in the cartesian coordinate system might require a large number of elements to model the U-bend region. Also, since the lift-off distance between the probe and tube wall is usually very small, a very fine mesh is required near the probe region to accurately describe the eddy current field. This paper presents a U-bend model using differential geometry principles that exploit the result that Maxwell’s equations are covariant with respect to changes of coordinates and independent of metrics. The equations remain unaltered in their form, regardless of the choice of the coordinates system, provided the field quantities are represented in the proper covariant and contravariant form. The complex shapes are mapped into simple straight sections, while small lift-off is mapped to larger values, thus reducing the intr...