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We consider the differential microwave imaging for continuous monitoring of hemorrhagic brain strokes where our aim is to determine the change of bleeding in sequential time frames. The scattered electromagnetic field is measured in two different time steps, and the difference in the scattered field is used as the data of the inversion scheme. The imaging is performed via contrast source inversion...
A hybrid technique using Digital Breast Tomosynthesis and Microwave Tomography shows promise for improved contrast recovery with respect to conventional breast imaging modalities. A healthy background field is modeled using a Finite Difference solver with prior breast tissue dielectric distribution given by Digital Breast Tomosynthesis. This background field is subtracted from the radar measurements...
The aim of this study is to compare the performance of different multiple-input multiple-output (MIMO) array topologies, intended to be used in ultra-wideband (UWB) near-field imaging applications, by using an analysis method that does not include the effects of image reconstruction algorithm. For this purpose, maximum projection method, previously proposed for the analysis of UWB arrays under far-field...
A geometrically simple circular array topology for two dimensional (2D) sparse multiple-input-multiple-output (MIMO) array is proposed. The focusing and imaging properties of the array in the millimeter-wave range with narrow-bandwidth are studied by simulation. The results for the focusing property show that the array has decent sidelobe levels over a wide field of view within near and far field...
Ultra-wideband (UWB) radar imaging has attracted attention for use in security and intelligent transportation system (ITS) applications. Conventional UWB Doppler interferometry is an effective way to obtain high-resolution images while using a simple radar system. However, this method produces ghost images when multiple closely-spaced human targets are present. To resolve this problem, we propose...
We have reconstructed microwave tomographic images of the Supelec breast phantom using our imaging fixture in combination with a multi-channel vector network analyzer. During this study we were able to recover images without the support of a priori information over a broad frequency range — 1100–1900 MHz. We then fitted the spectral values at each pixel within the field of view to a Cole-Cole curve...
This paper proposes a novel terahertz (THz) probe based on a pyramidal-shaped TE10 mode rectangular open ended waveguide (OEWG) integrated with a 45°-inclined linearly polarized (LP) element. The radiating element, deposited on top of the OEWG, is realized using standard printed-circuit and plated-through-hole technologies. The pyramidal fixture, situated beneath the substrate, is made of brass with...
THz impulse communications is a new system concept based on an imaging radar that we have been developing for biomedical imaging applications the past ten years. Its hybrid architecture combines the high-peak-power and spread-spectrum of photoconductive-switch transmitters with the high-responsivity and broad-bandwidth (RF and video) of Schottky-rectifier receivers. The data is impressed by simple...
Frequency-diverse imaging is an all-electronic method, capable of sampling the scene to be imaged without the need for a mechanical scan or active circuit components. In order to optimize the imaging characteristics, such as imaging resolution and fidelity of the reconstructed images, the antennas used within this scheme need to be optimized. It is demonstrated that using a Mills-Cross iris distribution,...
A near-field radar imaging technique is presented based on single-frequency measurements from a multiple-input multiple-output (MIMO) array. Such arrays are able to fully sample the κ-space of a region of interest. Advantageously, both range and cross-range information can be reconstructed, in contrast to conventional single-input multiple-output systems which require wideband frequency illumination...
Radar Cross Section analysis is the study of the scattering behavior of an object. The objective is to determine the main scatterers from measurements of the backscattered electric field. It is generally achieved by Radar Cross Section imaging. This leads to an ill-posed inverse problem because the system to solve is underdetermined. It is then necessary to regularize the problem by adding prior information...
A volume pixel subspace-based optimization method (SOM) is proposed to solve the electromagnetic imaging of the wave impenetrable objects/perfect electric conductor (PEC). In this proposed method, the PEC objects are approximated by highly lossy dielectric scatterers with pure imaginary permittivity and thus volume pixel SOM is successfully employed. There is no prior information such as the number...
In measurement scenarios with ground planes the boundary condition has to be included appropriately in the near-field to far-field transformation. For spherical near-field antenna measurements, techniques exist to include a ground plane in the xy-plane (z = 0m). In this paper, we will describe a transformation procedure including a translation of the transformation origin, so that the ground plane...
A new linear approach for support reconstruction of both penetrable and impenetrable objects from the measurements of the scattered fields is introduced and described. The approach takes advantage from the fact that for both high conductivity and dielectric scatterers, induced and ‘equivalent’ currents can be considered localized on the boundary. Starting from these considerations, an ad hoc compressive...
A new multistatic microwave imaging system containing specially designed antennas to avoid strong reflections at the interface to material samples with high dielectric constant is presented. The structure consists of a switched antenna array put in direct contact with the material in analysis and able, thanks to the antenna design, to minimize the interface impedance mismatch.
The localization of buried targets using Ground Penetrating Radar (GPR) is dealt with. The bi-static GPR is made of two identical Vivaldi antennas operating from 0.5 GHz to 3.5 GHz and installed in front of a sand box. The experimental data acquired in a controlled laboratory environment are validated by electromagnetic simulation. Then, both synthetic and experimental data are processed to detect...
This paper presents a novel high sensing capacity compressive imaging system, which is capable of imaging human-size targets. The system uses an array of Compressive Reflector Antennas (CRAs) in order to extend the imaging domain of a single CRA. Moreover, the multi-static electromagnetic cross-coupling of adjacent CRAs in the array is used as a mechanism to improve the imaging performance. A physical...
Turntable ISAR imaging systems generate radar images by rotating the radar target and performing measurements at various angles. The rotation leads to different perspectives onto the scattering centers of the target. This causes problems if polarimetric methods should be applied to the radar image. In this paper this problem is investigated and a correction technique suitable for two-dimensional imaging...
A novel processing algorithm for multiple elevation beam (MEB) synthetic aperture radar (SAR) systems is presented. MEB SAR is a promising technique to reduce the onboard data amount, and its key processing procedure is subpulse separation which is affected by the topography. In this paper, the echoes received by multiple elevation channels (MEC) are regarded as signals coming from different direction-of-arrive...
This contribution is based on an novel imaging system able to create real time radar images for personnel security screening recently presented. The imaging is performed as the person being screened continuously moves across a corridor populated with transmitters and receivers, and taking advantage of the person's movement to increase the number of observation angles. As part of a preliminary study...
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