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Special Issue "Microwave Sensing and Imaging"

A special issue of Sensors (ISSN 1424-8220). This special issue belongs to the section "Physical Sensors".

Deadline for manuscript submissions: 30 November 2021.

Special Issue Editors

Prof. Dr. Andrea Randazzo
E-Mail Website
Guest Editor
Department of Electrical, Electronic, Telecommunications Engineering, and Naval Architecture University of Genoa, Genoa, Italy
Interests: microwave imaging; electromagnetic propagation; inverse scattering; inverse problems; antennas
Special Issues and Collections in MDPI journals
Dr. Cristina Ponti
E-Mail Website
Guest Editor
Department of Engineering, “Roma Tre” University, Italy
Interests: electromagnetic scattering, electromagnetic propagation, inverse scattering, antennas
Dr. Alessandro Fedeli
E-Mail Website
Guest Editor
Department of Electrical, Electronic, Telecommunications Engineering, and Naval Architecture, University of Genoa, 16145 Genoa, Italy
Interests: forward and inverse electromagnetic scattering; computational electromagnetics; microwave imaging
Special Issues and Collections in MDPI journals

Special Issue Information

In the last years, microwave sensing and imaging have acquired an ever-growing importance in several applicative fields, such as non-destructive evaluation in industry and civil engineering, subsurface prospection, security, and biomedical imaging.

In principle, microwave techniques can be used to retrieve information about some physical parameters of the inspected targets (e.g., dielectric properties, shape, etc.) by using safe electromagnetic radiations and cost-effective systems, since the frequency band of interest is the same as in several other commercial apparatuses. Despite the great technological advances attained in the last years in this field, there are still some topics that could be addressed to further improve imaging systems. First, even more efficient and reliable measurement systems need to be designed and validated on a case-by-case basis, especially in realistic scenarios. Second, great attention should be paid to the development of effective data processing algorithms, able to solve the underlying electromagnetic inverse scattering problem (which is generally nonlinear and ill-posed) in order to retrieve the required information about the inspected targets from the measured scattered-field samples. Finally, efficient forward solvers are also fundamental for modeling the electromagnetic interactions between the interrogating fields and the targets in a suitable way.

In such a framework, this Special Issue aims at providing some insights into recent microwave sensing and imaging systems and techniques. Topics of interest include, but are not limited to: computational methods for electromagnetic imaging and inverse scattering, analytical and numerical forward modeling techniques in complex scenarios, sensors and antenna design, as well as innovative applications of microwave sensing and imaging.

Prof. Andrea Randazzo
Dr. Cristina Ponti
Dr. Alessandro Fedeli
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Sensors is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2200 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Microwave imaging 
  • Electromagnetic scattering 
  • Inverse scattering 
  • Inverse problems 
  • Electromagnetic modelling and simulation
  • Microwave sensors

Published Papers (12 papers)

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Research

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Article
Experimental Validation of a Microwave Imaging Method for Shallow Buried Target Detection by Under-Sampled Data and a Non-Cooperative Source
Sensors 2021, 21(15), 5148; https://doi.org/10.3390/s21155148 - 29 Jul 2021
Viewed by 413
Abstract
In microwave imaging, it is often of interest to inspect electrically large spatial regions. In these cases, data must be collected over a great deal of measurement points which entails long measurement time and/or costly, and often unfeasible, measurement configurations. In order to [...] Read more.
In microwave imaging, it is often of interest to inspect electrically large spatial regions. In these cases, data must be collected over a great deal of measurement points which entails long measurement time and/or costly, and often unfeasible, measurement configurations. In order to counteract such drawbacks, we have recently introduced a microwave imaging algorithm that looks for the scattering targets in terms of equivalent surface currents supported over a given reference plane. While this method is suited to detect shallowly buried targets, it allows one to independently process all frequency data, and hence the source and the receivers do not need to be synchronized. Moreover, spatial data can be reduced to a large extent, without any aliasing artifacts, by properly combining single-frequency reconstructions. In this paper, we validate such an approach by experimental measurements. In particular, the experimental test site consists of a sand box in open air where metallic plate targets are shallowly buried a (few cm) under the air/soil interface. The investigated region is illuminated by a fixed transmitting horn antenna, whereas the scattered field is collected over a planar measurement aperture at a fixed height from the air-sand interface. The transmitter and the receiver share only the working frequency information. Experimental results confirm the feasibility of the method. Full article
(This article belongs to the Special Issue Microwave Sensing and Imaging)
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Article
Field Representation Microwave Thermography Utilizing Lossy Microwave Design Materials
Sensors 2021, 21(14), 4830; https://doi.org/10.3390/s21144830 - 15 Jul 2021
Viewed by 507
Abstract
In this contribution, we are investigating a technique for the representation of electromagnetic fields by recording their thermal footprints on an indicator material using a thermal camera. Fundamentals regarding the interaction of electromagnetic heating, thermodynamics, and fluid dynamics are derived which allow for [...] Read more.
In this contribution, we are investigating a technique for the representation of electromagnetic fields by recording their thermal footprints on an indicator material using a thermal camera. Fundamentals regarding the interaction of electromagnetic heating, thermodynamics, and fluid dynamics are derived which allow for a precise design of the field illustration method. The synthesis and description of high-loss dielectric materials is discussed and a technique for a simple estimation of the broadband material’s imaginary permittivity part is introduced. Finally, exemplifying investigations, comparing simulations and measurements on the fundamental TE10-mode in an X-band waveguide are presented, which prove the above introduced sensing theory. Full article
(This article belongs to the Special Issue Microwave Sensing and Imaging)
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Article
Model-Based Systems Engineering Applied to Trade-Off Analysis of Wireless Power Transfer Technologies for Implanted Biomedical Microdevices
Sensors 2021, 21(9), 3201; https://doi.org/10.3390/s21093201 - 05 May 2021
Cited by 2 | Viewed by 670
Abstract
Decision-making is an important part of human life and particularly in any engineering process related to a complex product. New sensors and actuators based on MEMS technologies are increasingly complex and quickly evolving into products. New biomedical implanted devices may benefit from system [...] Read more.
Decision-making is an important part of human life and particularly in any engineering process related to a complex product. New sensors and actuators based on MEMS technologies are increasingly complex and quickly evolving into products. New biomedical implanted devices may benefit from system engineering approaches, previously reserved to very large projects, and it is expected that this need will increase in the future. Here, we propose the application of Model Based Systems Engineering (MBSE) to systematize and optimize the trade-off analysis process. The criteria, their utility functions and the weighting factors are applied in a systematic way for the selection of the best alternative. Combining trade-off with MBSE allow us to identify the more suitable technology to be implemented to transfer energy to an implanted biomedical micro device. Full article
(This article belongs to the Special Issue Microwave Sensing and Imaging)
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Article
Three-Dimensional Microwave Imaging: Fast and Accurate Computations with Block Resolution Algorithms
Sensors 2020, 20(21), 6282; https://doi.org/10.3390/s20216282 - 04 Nov 2020
Viewed by 570
Abstract
This paper considers the microwave imaging reconstruction problem, based on additive penalization and gradient-based optimization. Each evaluation of the cost function and of its gradient requires the resolution of as many high-dimensional linear systems as the number of incident fields, which represents a [...] Read more.
This paper considers the microwave imaging reconstruction problem, based on additive penalization and gradient-based optimization. Each evaluation of the cost function and of its gradient requires the resolution of as many high-dimensional linear systems as the number of incident fields, which represents a large amount of computations. Since all such systems involve the same matrix, we propose a block inversion strategy, based on the block-biconjugate gradient stabilized (BiCGStab) algorithm, with efficient implementations specific to the microwave imaging context. Numerical experiments performed on synthetic data and on real measurements show that savings in computing time can reach a factor of two compared to the standard, sequential, BiCGStab implementation. Improvements brought by the block approach are even more important for the most difficult reconstruction problems, that is, with high-frequency illuminations and/or highly contrasted objects. The proposed reconstruction strategy is shown to achieve satisfactory estimates for objects of the Fresnel database, even on the most contrasted ones. Full article
(This article belongs to the Special Issue Microwave Sensing and Imaging)
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Article
Low Cost, High Performance, 16-Channel Microwave Measurement System for Tomographic Applications
Sensors 2020, 20(18), 5436; https://doi.org/10.3390/s20185436 - 22 Sep 2020
Cited by 1 | Viewed by 778
Abstract
We have developed a multichannel software defined radio-based transceiver measurement system for use in general microwave tomographic applications. The unit is compact enough to fit conveniently underneath the current illumination tank of the Dartmouth microwave breast imaging system. The system includes 16 channels [...] Read more.
We have developed a multichannel software defined radio-based transceiver measurement system for use in general microwave tomographic applications. The unit is compact enough to fit conveniently underneath the current illumination tank of the Dartmouth microwave breast imaging system. The system includes 16 channels that can both transmit and receive and it operates from 500 MHz to 2.5 GHz while measuring signals down to −140 dBm. As is the case with multichannel systems, cross-channel leakage is an important specification and must be lower than the noise floors for each receiver. This design exploits the isolation inherent when the individual receivers for each channel are physically separate; however, these challenging specifications require more involved signal isolation techniques at both the system design level and the individual, shielded component level. We describe the isolation design techniques for the critical system elements and demonstrate specification compliance at both the component and system level. Full article
(This article belongs to the Special Issue Microwave Sensing and Imaging)
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Article
Through-the-Wall Microwave Imaging: Forward and Inverse Scattering Modeling
Sensors 2020, 20(10), 2865; https://doi.org/10.3390/s20102865 - 18 May 2020
Cited by 6 | Viewed by 961
Abstract
The imaging of dielectric targets hidden behind a wall is addressed in this paper. An analytical solver for a fast and accurate computation of the forward scattered field by the targets is proposed, which takes into account all the interactions of the electromagnetic [...] Read more.
The imaging of dielectric targets hidden behind a wall is addressed in this paper. An analytical solver for a fast and accurate computation of the forward scattered field by the targets is proposed, which takes into account all the interactions of the electromagnetic field with the interfaces of the wall. Furthermore, an inversion procedure able to address the full underlying non-linear inverse scattering problem is introduced. This technique exploits a regularizing scheme in Lebesgue spaces in order to reconstruct an image of the hidden targets. Preliminary numerical results are provided in order to initially assess the capabilities of the developed solvers. Full article
(This article belongs to the Special Issue Microwave Sensing and Imaging)
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Article
A Prototype Microwave System for 3D Brain Stroke Imaging
Sensors 2020, 20(9), 2607; https://doi.org/10.3390/s20092607 - 03 May 2020
Cited by 24 | Viewed by 1576
Abstract
This work focuses on brain stroke imaging via microwave technology. In particular, the open issue of monitoring patients after stroke onset is addressed here in order to provide clinicians with a tool to control the effectiveness of administered therapies during the follow-up period. [...] Read more.
This work focuses on brain stroke imaging via microwave technology. In particular, the open issue of monitoring patients after stroke onset is addressed here in order to provide clinicians with a tool to control the effectiveness of administered therapies during the follow-up period. In this paper, a novel prototype is presented and characterized. The device is based on a low-complexity architecture which makes use of a minimum number of properly positioned and designed antennas placed on a helmet. It exploits a differential imaging approach and provides 3D images of the stroke. Preliminary experiments involving a 3D phantom filled with brain tissue-mimicking liquid confirm the potential of the technology in imaging a spherical target mimicking a stroke of a radius equal to 1.25 cm. Full article
(This article belongs to the Special Issue Microwave Sensing and Imaging)
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Article
On the Orbital Angular Momentum Incident Fields in Linearized Microwave Imaging
Sensors 2020, 20(7), 1905; https://doi.org/10.3390/s20071905 - 30 Mar 2020
Cited by 5 | Viewed by 865
Abstract
Orbital angular momentum (OAM) is gaining great attention in the physics and electromagnetic community owing to an intriguing debate concerning its suitability for widening channel capacity in next-generation wireless communications. While such a debate is still a matter of controversy, we exploit OAM [...] Read more.
Orbital angular momentum (OAM) is gaining great attention in the physics and electromagnetic community owing to an intriguing debate concerning its suitability for widening channel capacity in next-generation wireless communications. While such a debate is still a matter of controversy, we exploit OAM generation for microwave imaging within the classical first order linearized models, i.e., Born and Rytov approximation. Physical insights into different fields carrying -order OAM are conveniently exploited to propose possible alternative imaging approaches and paradigms in microwave imaging. Full article
(This article belongs to the Special Issue Microwave Sensing and Imaging)
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Article
Experimental Validation of Microwave Tomography with the DBIM-TwIST Algorithm for Brain Stroke Detection and Classification
Sensors 2020, 20(3), 840; https://doi.org/10.3390/s20030840 - 04 Feb 2020
Cited by 15 | Viewed by 1722
Abstract
We present an initial experimental validation of a microwave tomography (MWT) prototype for brain stroke detection and classification using the distorted Born iterative method, two-step iterative shrinkage thresholding (DBIM-TwIST) algorithm. The validation study consists of first preparing and characterizing gel phantoms which mimic [...] Read more.
We present an initial experimental validation of a microwave tomography (MWT) prototype for brain stroke detection and classification using the distorted Born iterative method, two-step iterative shrinkage thresholding (DBIM-TwIST) algorithm. The validation study consists of first preparing and characterizing gel phantoms which mimic the structure and the dielectric properties of a simplified brain model with a haemorrhagic or ischemic stroke target. Then, we measure the S-parameters of the phantoms in our experimental prototype and process the scattered signals from 0.5 to 2.5 GHz using the DBIM-TwIST algorithm to estimate the dielectric properties of the reconstruction domain. Our results demonstrate that we are able to detect the stroke target in scenarios where the initial guess of the inverse problem is only an approximation of the true experimental phantom. Moreover, the prototype can differentiate between haemorrhagic and ischemic strokes based on the estimation of their dielectric properties. Full article
(This article belongs to the Special Issue Microwave Sensing and Imaging)
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Article
An Imaging Plane Calibration Method for MIMO Radar Imaging
Sensors 2019, 19(23), 5261; https://doi.org/10.3390/s19235261 - 29 Nov 2019
Viewed by 798
Abstract
In two dimensional cross-range multiple-input multiple-output radar imaging for aerial targets, due to the non-cooperative movement of the targets, the estimated imaging plane parameters, namely the center and the posture angles of the imaging plane, may have deviations from true values, which defocus [...] Read more.
In two dimensional cross-range multiple-input multiple-output radar imaging for aerial targets, due to the non-cooperative movement of the targets, the estimated imaging plane parameters, namely the center and the posture angles of the imaging plane, may have deviations from true values, which defocus the final image. This problem is called imaging plane mismatch in this paper. Focusing on this problem, firstly the deviations of spatial spectrum fulfilling region caused by imaging plane mismatch is analyzed, as well as the errors of the corresponding spatial spectral values. Thereupon, the calibration operation is deduced when the imaging plane parameters are accurately obtained. Afterwards, an imaging plane calibration algorithm is proposed to utilize particle swarm optimization to search out the imaging plane parameters. Finally, it is demonstrated through simulations that the proposed algorithm can accurately estimate the imaging plane parameters and achieve good image focusing performance. Full article
(This article belongs to the Special Issue Microwave Sensing and Imaging)
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Article
Detecting Axial Ratio of Microwave Field with High Resolution Using NV Centers in Diamond
Sensors 2019, 19(10), 2347; https://doi.org/10.3390/s19102347 - 21 May 2019
Viewed by 1268
Abstract
Polarization property characterization of the microwave (MW) field with high speed and resolution is vitally beneficial as the circularly-polarized MW field plays an important role in the development of quantum technologies and satellite communication technologies. In this work, we propose a scheme to [...] Read more.
Polarization property characterization of the microwave (MW) field with high speed and resolution is vitally beneficial as the circularly-polarized MW field plays an important role in the development of quantum technologies and satellite communication technologies. In this work, we propose a scheme to detect the axial ratio of the MW field with optical diffraction limit resolution with a nitrogen vacancy (NV) center in diamond. Firstly, the idea of polarization selective detection of the MW magnetic field is carried out using a single NV center implanted in a type-IIa CVD diamond with a confocal microscope system achieving a sensitivity of 1.7 μT/Hz. Then, high speed wide-field characterization of the MW magnetic field at the submillimeter scale is realized by combining wide-field microscopy and ensemble NV centers inherent in a general CVD diamond. The precision axial ratio can be detected by measuring the magnitudes of two counter-rotating circularly-polarized MW magnetic fields. The wide-field detection of the axial ratio and strength parameters of microwave fields enables high speed testing of small-scale microwave devices. Full article
(This article belongs to the Special Issue Microwave Sensing and Imaging)
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Letter
Terahertz Frequency-Scaled Differential Imaging for Sub-6 GHz Vehicular Antenna Signature Analysis
Sensors 2020, 20(19), 5636; https://doi.org/10.3390/s20195636 - 02 Oct 2020
Cited by 1 | Viewed by 635
Abstract
The next generation of connected and autonomous vehicles will be equipped with high numbers of antennas operating in a wide frequency range for communications and environment sensing. The study of 3D spatial angular responses and the radiation patterns modified by vehicular structure will [...] Read more.
The next generation of connected and autonomous vehicles will be equipped with high numbers of antennas operating in a wide frequency range for communications and environment sensing. The study of 3D spatial angular responses and the radiation patterns modified by vehicular structure will allow for better integration of the associated communication and sensing antennas. The use of near-field monostatic focusing, applied with frequency-dimension scale translation and differential imaging, offers a novel imaging application. The objective of this paper is to theoretically and experimentally study the method of obtaining currents produced by an antenna radiating on top of a vehicular platform using differential imaging. The experimental part of the study focuses on measuring a scaled target using an imaging system operating in a terahertz band—from 220 to 330 GHz—that matches a 5G frequency band according to frequency-dimension scale translation. The results show that the induced currents are properly estimated using this methodology, and that the influence of the bandwidth is assessed. Full article
(This article belongs to the Special Issue Microwave Sensing and Imaging)
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