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It is important to know which parts of an inspection domain could be suitably reconstructed in through the wall imaging (TWI). It is also of interest to find a frequency range for which a reconstruction algorithm is efficient. For these purposes, a quantitative investigation of the coverage area and frequency bandwidth of the imaging setup is introduced. The imaging process is based on the linear...
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...
Quantitative microwave holography is a recently proposed imaging method that offers quantitative reconstruction in a quasi-real time. Since it is a direct inversion method, its utility is limited to weak-scattering problems. The feasibility of microwave holography in tissue reconstruction is studied here. The reconstruction results are promising, suggesting microwave holography is suitable as a linear...
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 new feature extraction method for synthetic aperture radar (SAR) images with application to automatic target recognition (ATR). The original SAR image is first represented by a sparse image containing only a few dominant scattering centers (SCs). According to the theory of 2D compressive sensing (CS), a sparse image can be reconstructed from a low dimensional matrix with little...
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,...
We demonstrate a frequency-diverse imaging system using an air-filled cavity-backed antenna as a transceiver (cavity-to-cavity system layout) for the K-band (17.5–26.5 GHz) frequency regime. Leveraging the computational imaging concept, the frequency-diversity enables imaging in an all-electronic manner, without the need for mechanical raster scanning or active circuit components, minimizing the data...
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...
The paper proposes a fast and interpolation-free method for near-field 3-D radar imaging. The scattered data are measured on 2-D planar antenna array with wideband stepped frequency signal. The near-field 3-D imaging procedure is indeed a nonuniform summation problem. Different from the conventional interpolation fast Fourier transform (FFT) method, the proposed method regards the imaging procedure...
This work presents some preliminary results from applying our previously developed microwave imaging algorithm based on two-step iterative shrinkage/thresholding (TwIST) to data measured from an experimental microwave imaging system. Combining the distorted Born iterative method (DBIM) with the TwIST linear solver, our two-dimensional (2-D) algorithm is applied to reconstruct 2-D slices of the complex...
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 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...
This paper deals with the polarization aspect in 3D inverse scattering. The vectorial information contained in the scattering matrix is often under-exploited in quantitative inverse scattering problems even if it has been expensively studied in radar processing. In this work, we present a study of the influence of the polarization state of the electromagnetic wave on the reconstructed permittivity...
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...
In this paper, we describe a novel unmixing algorithm for detecting breast cancer. In this approach, the breast tissue is separated into three components, low water content (LWC), high water content (HWC), and cancerous tissues, and the goal of the optimization procedure is to recover the mixture proportions for each component. By utilizing this approach in a hybrid DBT / NRI system, the unmixing...
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