Special Issue "Microwave Imaging and Its Application"

A special issue of Electronics (ISSN 2079-9292). This special issue belongs to the section "Microwave and Wireless Communications".

Deadline for manuscript submissions: closed (30 September 2019).

Special Issue Editor

Dr. Raffaele Solimene
E-Mail Website
Guest Editor
Dipartimento di Ingegneria, Università degli Studi della Campania, 81031 Aversa, Italy
Interests: electromagnetic inverse source and inverse scattering problems, electromagnetic field information content, GPR prospecting, TWI imaging, breast cancer detection by microwaves, vital sign detection, random array antennas

Special Issue Information

Dear Colleagues,

Microwave imaging refers to all the methods and techniques that exploit the scattering of electromagnetic waves to obtain information about a spatial region under investigation. The research in this field is rich and has progressed from detection and location to the more ambitious objective of reconstructing the scene in terms of the object shapes and material composition. The application contexts are countless, both for long- and short-range configurations, which range from classical radar imaging to subsurface prospecting, from through-the-wall imaging to medical diagnostics, to name just a few. In any case, to be successful, microwave imaging requires different ingredients, such as electromagnetic modeling, math and numerical math, signal processing, electronics, etc. The aim of this Special Issue is to collect contributions from scientists working in this field and in all the pertinent applicative contexts that provide recent advances in microwave imaging, including hardware design, image reconstruction methods, computational methods and experimental verification under realistic conditions.

Topics of interest for this Special Issue include, but are not limited to:

  • Novel electromagnetic scattering models
  • Linear and non-linear inversion methods and achievable performance
  • Passive and/or non-cooperative source microwave imaging
  • Information theoretic approaches for data selection and performance computation
  • Numerically efficient inversion algorithms
  • Hardware and antenna design
  • Experimental in situ verification
  • Antenna deconvolution and clutter rejection for near- and very near-zone configuration
  • Phase only data microwave imaging

Prof. Raffaele Solimene
Guest Editor

Manuscript Submission Information

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Keywords

  • Electromagnetic Inverse Problems
  • Microwave Imaging
  • Experimental Investigations

Published Papers (12 papers)

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Research

Open AccessFeature PaperArticle
On the Introduction of Canny Operator in an Advanced Imaging Algorithm for Real-Time Detection of Hyperbolas in Ground-Penetrating Radar Data
Electronics 2020, 9(3), 541; https://doi.org/10.3390/electronics9030541 - 24 Mar 2020
Abstract
This paper focuses on the use of the Canny edge detector as the first step of an advanced imaging algorithm for automated detection of hyperbolic reflections in ground-penetrating radar (GPR) data. Since the imaging algorithm aims to work in real time; particular attention [...] Read more.
This paper focuses on the use of the Canny edge detector as the first step of an advanced imaging algorithm for automated detection of hyperbolic reflections in ground-penetrating radar (GPR) data. Since the imaging algorithm aims to work in real time; particular attention is paid to its computational efficiency. Various alternative criteria are designed and examined, to fasten the procedure by eliminating unnecessary edge pixels from Canny-processed data, before such data go through the subsequent steps of the detection algorithm. The effectiveness and reliability of the proposed methodology are tested on a wide set of synthetic and experimental radargrams with promising results. The finite-difference time-domain simulator gprMax is used to generate synthetic radargrams for the tests, while the real radargrams come from GPR surveys carried out by the authors in urban areas. The imaging algorithm is implemented in MATLAB. Full article
(This article belongs to the Special Issue Microwave Imaging and Its Application)
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Open AccessFeature PaperArticle
Performance Evaluation of Group Sparse Reconstruction and Total Variation Minimization for Target Imaging in Stratified Subsurface Media
Electronics 2019, 8(11), 1245; https://doi.org/10.3390/electronics8111245 - 30 Oct 2019
Abstract
Sparse reconstruction methods have been successfully applied for efficient radar imaging of targets embedded in stratified dielectric subsurface media. Recently, a total variation minimization (TVM) based approach was shown to provide superior image reconstruction performance over standard L1-norm minimization-based method, especially in case [...] Read more.
Sparse reconstruction methods have been successfully applied for efficient radar imaging of targets embedded in stratified dielectric subsurface media. Recently, a total variation minimization (TVM) based approach was shown to provide superior image reconstruction performance over standard L1-norm minimization-based method, especially in case of non-point-like targets. Alternatively, group sparse reconstruction (GSR) schemes can also be employed to account for embedded target extent. In this paper, we provide qualitative and quantitative performance evaluations of TVM and GSR schemes for efficient and reliable target imaging in stratified subsurface media. Using numerical electromagnetic data of targets buried in the ground, we demonstrate that GSR and TVM provide comparable reconstruction performance qualitatively, with GSR exhibiting a slight superiority over TVM quantitatively, albeit at the expense of less flexibility in regularization parameters. Full article
(This article belongs to the Special Issue Microwave Imaging and Its Application)
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Open AccessFeature PaperArticle
Fast Imaging of Short Perfectly Conducting Cracks in Limited-Aperture Inverse Scattering Problem
Electronics 2019, 8(9), 1050; https://doi.org/10.3390/electronics8091050 - 18 Sep 2019
Abstract
In this paper, we consider the application and analysis of subspace migration technique for a fast imaging of a set of perfectly conducting cracks with small length in two-dimensional limited-aperture inverse scattering problem. In particular, an imaging function of subspace migration with asymmetric [...] Read more.
In this paper, we consider the application and analysis of subspace migration technique for a fast imaging of a set of perfectly conducting cracks with small length in two-dimensional limited-aperture inverse scattering problem. In particular, an imaging function of subspace migration with asymmetric multistatic response matrix is designed, and its new mathematical structure is constructed in terms of an infinite series of Bessel functions and the range of incident and observation directions. This is based on the structure of left and right singular vectors linked to the nonzero singular values of MSR matrix and asymptotic expansion formula due to the existence of cracks. Investigated structure of imaging function indicates that imaging performance of subspace migration is highly related to the range of incident and observation directions. The simulation results with synthetic data polluted by random noise are exhibited to support investigated structure. Full article
(This article belongs to the Special Issue Microwave Imaging and Its Application)
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Open AccessFeature PaperArticle
Microwave Imaging by Means of Lebesgue-Space Inversion: An Overview
Electronics 2019, 8(9), 945; https://doi.org/10.3390/electronics8090945 - 27 Aug 2019
Cited by 1
Abstract
An overview of the recent advancements in the development of microwave imaging procedures based on the exploitation of the regularization theory in Lebesgue spaces is reported in this paper. Such inversion schemes have been found to provide accurate results in several microwave imaging [...] Read more.
An overview of the recent advancements in the development of microwave imaging procedures based on the exploitation of the regularization theory in Lebesgue spaces is reported in this paper. Such inversion schemes have been found to provide accurate results in several microwave imaging scenarios, thanks to the different geometrical properties that Lebesgue spaces can exhibit with respect to the more classical Hilbert ones. Moreover, the recent extension to the more general case of variable-exponent Lebesgue spaces is also addressed. Experimental results involving reference data are shown for supporting the theoretical description of the approaches. Full article
(This article belongs to the Special Issue Microwave Imaging and Its Application)
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Open AccessFeature PaperArticle
Second Harmonic Beam Shaping and Sensing in Dielectric Bow-Tie Antenna via Convex Optimization Array Synthesis Approach
Electronics 2019, 8(8), 901; https://doi.org/10.3390/electronics8080901 - 15 Aug 2019
Abstract
We propose a convex optimization approach for an array synthesis pattern to enhance the electromagnetic field in the gap region of a dielectric bow-tie antenna. This method allows the induction of the desired antenna modes by exploiting the concurrent excitation of the structure [...] Read more.
We propose a convex optimization approach for an array synthesis pattern to enhance the electromagnetic field in the gap region of a dielectric bow-tie antenna. This method allows the induction of the desired antenna modes by exploiting the concurrent excitation of the structure with plane waves with different propagation directions and complex amplitudes. By engineering the excitation coefficients of the array, different modes are excited in the bow-tie antenna and the radiation pattern of the generated second harmonic (SH) field is modified accordingly. Using our approach, we demonstrate both the feasibility of performing synthesis of the SH radiation pattern in dielectric antennas and the possibility of developing innovative sensing applications in photonics. Full article
(This article belongs to the Special Issue Microwave Imaging and Its Application)
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Open AccessArticle
Radiation Properties of Conformal Antennas: The Elliptical Source
Electronics 2019, 8(5), 531; https://doi.org/10.3390/electronics8050531 - 11 May 2019
Cited by 1
Abstract
The solution of inverse source problems by numerical procedures requires the investigation of the number of independent pieces of information that can be reconstructed stably. To this end, the mathematical properties of the relevant operators are to be examined in connection with the [...] Read more.
The solution of inverse source problems by numerical procedures requires the investigation of the number of independent pieces of information that can be reconstructed stably. To this end, the mathematical properties of the relevant operators are to be examined in connection with the source shape. The aim of this work is to investigate the effect of the source shape on the eigendecomposition of the radiation operator in a 2D geometry, when the radiated field is observed over a semi-circumference in the far zone. We examine both the behavior of the eigenvalues and the effect of the choice of the representation variables on the point spread function (PSF). In particular, the effect of the choice of the representation variables is considered since operator properties may depend on it. We analyze different source shapes evolving from a line to a semi-ellipse and, finally, to a semi-circumference, in order to understand how the increase of the source aspect ratio affects the results. The main conclusions concern an estimate of the number of degrees of freedom in connection with the source geometry and the fact that the PSF exhibits the same variant behavior along the considered domain, independently of the observation variable. The practical relevance of the result is illustrated by two numerical examples. The first one deals with the conformal array diagnostics for the reliable reconstruction of the excitation of the array elements. The second one concerns the array synthesis problem, and a comparison between the radiating performances of the source geometries is presented. Full article
(This article belongs to the Special Issue Microwave Imaging and Its Application)
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Open AccessArticle
Localization and Frequency Identification of Large-Range Wide-Band Electromagnetic Interference Sources in Electromagnetic Imaging System
Electronics 2019, 8(5), 499; https://doi.org/10.3390/electronics8050499 - 05 May 2019
Cited by 3
Abstract
The identification and localization of large-range, wide-band electromagnetic interference (EMI) sources have always been both costly and time-consuming. The measurements at different times and places are often required before a typical system can locate a target. In this paper, we proposed a 2D [...] Read more.
The identification and localization of large-range, wide-band electromagnetic interference (EMI) sources have always been both costly and time-consuming. The measurements at different times and places are often required before a typical system can locate a target. In this paper, we proposed a 2D electromagnetic imaging system to localize interference sources and identify the EMI frequency in real time. In this system, an offset paraboloid with a diameter of three meters is designed for large-range EMI imaging, while a multi-channel digital signal acquisition system is developed for wide-band EMI localization. The located interference source is segmented by the maximum entropy method based on particle swarm optimization, and the modified generalized regression neural network (MGRNN) is applied to identify the EMI frequency effectively by excluding misleading effects of outliers. The experiment which has been completed on our dataset indicates that our approach not only increases accuracy by 5% compared with the standard generalized regression neural network approaches for identification, but also exerts a large-range wide-band localization of the EMI source detection method. Full article
(This article belongs to the Special Issue Microwave Imaging and Its Application)
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Open AccessArticle
A Parasitic Resonator-Based Diamond-Shaped Microstrip Antenna for Microwave Imaging Applications
Electronics 2019, 8(4), 434; https://doi.org/10.3390/electronics8040434 - 16 Apr 2019
Cited by 2
Abstract
This study proposes a new parasitic resonator-based diamond-shaped microstrip patch antenna for ultra-wideband microwave imaging applications. The antenna consists of a diamond-shaped radiating patch, partial ground plane, and four-star shape parasitic elements. The use of parasitic elements improves the antenna performance in terms [...] Read more.
This study proposes a new parasitic resonator-based diamond-shaped microstrip patch antenna for ultra-wideband microwave imaging applications. The antenna consists of a diamond-shaped radiating patch, partial ground plane, and four-star shape parasitic elements. The use of parasitic elements improves the antenna performance in terms of the bandwidth and gain. The proposed prototype has a compact dimension of 30 × 25 × 1.6 mm3. The antenna achieves an overall bandwidth (S11<-10dB) of 7.6 GHz (2.7–10.3 GHz) with more than 4 dBi realized gain and 80% efficiency across the radiating bandwidth. The modified structures of the design extended the usable upper frequency from 9.7 GHz to 10.3 GHz, and the lower frequency is decreased from 3.4 GHz to 2.7 GHz with maintaining the omnidirectional radiation pattern. The design and simulation of the antenna are performed in the 3D electromagnetic simulator CST Microwave Studio. The proposed antenna is used for breast phantom measurement system to analyze the variation of backscattering signal and transmit-received pulses. The observation during the analysis of the numerical and measured data reveals that the designed antenna is a suitable candidate for ultra-wideband (UWB)-based microwave imaging applications. Full article
(This article belongs to the Special Issue Microwave Imaging and Its Application)
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Open AccessArticle
Inverse Scattering Analysis from Measurement Data of Total Electric and Magnetic Fields by Means of Cylindrical-Wave Expansion
Electronics 2019, 8(4), 417; https://doi.org/10.3390/electronics8040417 - 10 Apr 2019
Cited by 2
Abstract
Microwave tomography is an effective technique to estimate material distribution, where inverse scattering analysis is performed on the assumption that accurate information on the incident field is known for a measurement curve as well as in the target region. In reality, however, the [...] Read more.
Microwave tomography is an effective technique to estimate material distribution, where inverse scattering analysis is performed on the assumption that accurate information on the incident field is known for a measurement curve as well as in the target region. In reality, however, the information may often be unobtainable due to multiple scattering between the transmitting antenna and the target object, or existence of unwanted waves and obstacles. In this paper, a method to extract information on incident fields from measured total field data is proposed. The validity of the proposed method is verified on 2D TMz problems, where a cylindrical, a square, and an L-shape homogeneous object are employed as a target object. Furthermore, it is shown that the method is available even when there are unwanted obstacles outside the measurement curve. Full article
(This article belongs to the Special Issue Microwave Imaging and Its Application)
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Open AccessFeature PaperArticle
Multiresolution Virtual Experiments for Microwave Imaging of Complex Scenarios
Electronics 2019, 8(2), 153; https://doi.org/10.3390/electronics8020153 - 01 Feb 2019
Abstract
In this paper, a multiresolution approach for the quantitative microwave imaging of complex scenarios is introduced. The proposed strategy takes advantage of the combined use of a recently introduced iterative method known as distorted iterated virtual experiments (DIVE), based on the paradigm of [...] Read more.
In this paper, a multiresolution approach for the quantitative microwave imaging of complex scenarios is introduced. The proposed strategy takes advantage of the combined use of a recently introduced iterative method known as distorted iterated virtual experiments (DIVE), based on the paradigm of “virtual experiments”, and a wavelet-based projection scheme. This strategy allows the unknown profiles to be represented at different resolution scales and, as such, it is particularly suitable for the imaging of highly heterogeneous targets. Moreover, the developed algorithm blends together the intrinsic multiresolution feature of the wavelet projection with the one gained by means of a frequency hopping technique. The method was tested against realistic heterogeneous scenarios of practical interest, such as breast and tree trunk phantoms, which are of interest in non-invasive medical diagnostics and the health monitoring of standing trees. Full article
(This article belongs to the Special Issue Microwave Imaging and Its Application)
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Open AccessArticle
The Role of Diversity on Linear Scattering Operator: The Case of Strip Scatterers Observed under the Fresnel Approximation
Electronics 2019, 8(1), 113; https://doi.org/10.3390/electronics8010113 - 20 Jan 2019
Cited by 1
Abstract
The aim of this paper is to investigate the role of multiple views and multiple frequencies in linear inverse scattering problems. The study was performed assuming the Fresnel-zone approximation on the scattering operator. Due to the crucial role played by singular values into [...] Read more.
The aim of this paper is to investigate the role of multiple views and multiple frequencies in linear inverse scattering problems. The study was performed assuming the Fresnel-zone approximation on the scattering operator. Due to the crucial role played by singular values into analysing the linear inverse scattering problems, the impact of view and frequency diversities on singular values behaviour was established. In fact, the singular values were related to the most common metrics used to quantify the achievable performances in inverse scattering problems, such as the number of degrees of freedom (NDF), the information content and the resolution. Full article
(This article belongs to the Special Issue Microwave Imaging and Its Application)
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Open AccessArticle
Free-Space Materials Characterization by Reflection and Transmission Measurements using Frequency-by-Frequency and Multi-Frequency Algorithms
Electronics 2018, 7(10), 260; https://doi.org/10.3390/electronics7100260 - 18 Oct 2018
Cited by 1
Abstract
The knowledge of the electromagnetic constitutive properties of materials is crucial in many applications. Free-space methods are widely used for this purpose, despite their inherent practical difficulties. This paper describes an affordable free-space experimental setup for the characterization of flat samples in 1–6 [...] Read more.
The knowledge of the electromagnetic constitutive properties of materials is crucial in many applications. Free-space methods are widely used for this purpose, despite their inherent practical difficulties. This paper describes an affordable free-space experimental setup for the characterization of flat samples in 1–6 GHz in a non-anechoic environment. The extracted properties are obtained from the calibrated Scattering Parameters, using a frequency-by-frequency solution or a multi-frequency reconstruction. For the first, we describe how the Time-Domain Gating can be implemented and used for filtering the signals. For the latter, a weighting factor is introduced to balance the reflection and transmission data, allowing one to have a more favorable configuration. The different role of transmission and reflection measurements on the achievable results is analyzed with regard to experimental uncertainties and different noise scenarios. Results from the two strategies are analyzed and compared. Good agreement between simulation, measurement and literature is obtained. According to the reported results for dielectric materials, there is no need of filtering the data by a Time-Domain Gating in case of the multi-frequency approach. Experimental results for Polymethylmethacrylate (PMMA) and Polytetrafluorethylene (PTFE) samples validate both the setup and the processing. Full article
(This article belongs to the Special Issue Microwave Imaging and Its Application)
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