Measured Antenna Response of a Proposed Microwave Tomography System Using an Efficient 3-D FDTD Model

Abstract

This letter presents a detailed study of a microwave tomography system using 3-D finite-difference time-domain methods (FDTDs). The algorithm, which uses a subcell model in form of the thin-wire approximation to model wire antennas, has been validated numerically using published numerical electromagnetic code (NEC) data for dipole antennas, and experimentally by comparing with measurements obtained for a monopole antenna array. The agreement between calculated and measured performances of the monopoles is close. In order to understand the fabrication tolerance, a parametric study was performed with regards to position of ground plane and grid size. It is found that the ground plane plays an important role in the performance of the monopole antennas. The excellent agreement is very promising for future deployment of the algorithm in 3-D microwave tomography applications.Index Terms-Finite difference time domain method, resistive voltage source, microwave imaging, microwave measurements, transient analysis.

Experimental performances of antennas for a proposed microwave tomography system using the time-domain approach

“…The FDTD domain is truncated by suitable CPML (Convolutional Perfectly Matched Layers) to minimize the reflections from edges. The details of FDTD formulation for this problem have been described elsewhere in [11].…”

On the use of different polarization measurements in microwave imaging of breast cancer tumors

“…Another problem is that small spherical tumors or inclusions are not modeled well in a 2D algorithm where these objects effectively are described as cylindrical objects. We have also developed a 3D algorithm that we have used with this measurement setup, [9]. In this algorithm we can make accurate models of the antennas but since we have no antennas outside the plane we still can get no information about the objects in the z-direction and therefore still only image 2D objects.…”

On the Calibration of a Multistatic Scattering Matrix Measured by a Fixed Circular Array of Antennas

“…This is what has been done in a free space environment [3][4][5], in a liquid environment [6,7] or above a buried target [8,9] for example. Another possibility is to construct it electronically with a fixed array of antennas, each pair of emitter/receiver being selected thanks to hyperfrequency switches or any kind of multiplexer/demultiplexer devices, e.g., [10][11][12][13][14][15]. It is even possible to combine the two approaches as done for example in [16] where an array of modulated receivers is kept fixed and the multiple illuminations are created by rotating the target on itself.…”

“…One possibility would be to directly calibrate each antenna using a two-port calibration technique as it is done in [15], but due to our low-cost multiplexer, we are faced with too many losses which prevent us from applying this technique. Moreover, this two-port calibration technique is not sufficient to take care of the antennas diversity and the scattering phenomena.…”