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Microwave Techniques for Spectroscopy and Imaging Applications
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Microwave Techniques for Spectroscopy and Imaging Applications

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

Deadline for manuscript submissions: closed (31 May 2024) | Viewed by 12201

Special Issue Editors

Dr. Romolo Marcelli

E-Mail Website
Guest Editor
CNR-IMM Roma, Via del Fosso del Cavaliere 100, 00133 Roma, Italy
Interests: metamaterials for high-frequency applications; microwave components with a focus on RF MEMS and NEMS; microwave and millimeter wave components for space and security; scanning microwave microscopy for magnetic, semiconducting, and dielectric materials
Special Issues, Collections and Topics in MDPI journals
Dr. Emanuela Proietti

E-Mail Website
Guest Editor
CNR-IMM Roma, Via del Fosso del Cavaliere 100, 00133 Roma, Italy
Interests: microwave measurements for cultural heritage applications; microwave tomography; RF MEMS
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Microwaves have been utilized for decades, mainly in systems for telecommunication applications. On the other hand, the penetration of microwaves, especially at frequencies not exceeding the C-Band, promoted additional fields of interest, encompassing material science, cultural heritage and biological imaging. Near field measurement techniques have been developed for local characterization of dielectric and magnetic properties of materials. Actually, spectroscopy and imaging of small areas with purposely shaped tips is now possible to detect sub-surface buried metallization and to observe dielectric inclusions by processing microwave reflected signals. Magnitude and phase of scattering parameters, the typical quantities recorded in microwave measurements, are useful for both image reconstruction and local properties determination. At a different scale, involving macroscopic samples, spectroscopy and 3D imaging is performed using a number of antennas placed around the structure to be measured, to get information about internal discontinuities generated again by the presence of metals or regions exhibiting different values of the dielectric constant. So far, general concepts can be shared among different fields, but actual solutions and physical modelling are quite different, comparing micro- and macro-setups necessary for the characterization. In this Special Issue, the basic concepts of spectroscopy and imaging based on microwave measurements will be discussed, together with the inverted reconstruction algorithms for post-processing raw data to generate the image.

Dr. Romolo Marcelli
Dr. Emanuela Proietti
Guest Editors

Manuscript Submission Information

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 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 spectroscopy and imaging
  • near field microscopy
  • dielectric constant measurement
  • image reconstruction algorithms

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Published Papers (5 papers)

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Research

11 pages, 3450 KiB  
Communication
Exposure Time Control Method for Higher Intermediate Frequency in Optical Heterodyne Imaging and Its Application to Electric-Field Imaging Based on Electro-Optic Effect
by Kiyotaka Sasagawa, Ryoma Okada, Yoshihiro Akamatsu, Maya Mizuno, Hironari Takehara, Makito Haruta, Hiroyuki Tashiro and Jun Ohta
Sensors 2024, 24(4), 1249; https://doi.org/10.3390/s24041249 - 15 Feb 2024
Cited by 1 | Viewed by 1138
Abstract
We propose and demonstrate a method for equivalent time sampling using image sensors to selectively detect only the target frequency. Shortening the exposure time of the image sensor and using equivalent time sampling allows for the detection of frequency components that are higher [...] Read more.
We propose and demonstrate a method for equivalent time sampling using image sensors to selectively detect only the target frequency. Shortening the exposure time of the image sensor and using equivalent time sampling allows for the detection of frequency components that are higher than the frame rate. However, the imaging system in our previous work was also sensitive to the frequency component at 1/4 of the frame rate. In this study, we control the phase relationship between the exposure time and observed signal by inserting an additional interval once every four frames to detect the target frequency selectively. With this technique, we conducted electric field imaging based on the electro-optic effect under high noise conditions in the low-frequency band to which the conventional method is sensitive. The results demonstrated that the proposed method improved the signal-to-noise ratio. Full article
(This article belongs to the Special Issue Microwave Techniques for Spectroscopy and Imaging Applications)
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17 pages, 20082 KiB  
Article
In-Wall Imaging for the Reconstruction of Obstacles by Reverse Time Migration
by M. Lütfi Yarar and Ali Yapar
Sensors 2023, 23(9), 4456; https://doi.org/10.3390/s23094456 - 3 May 2023
Cited by 1 | Viewed by 2017
Abstract
In this paper, the reverse time migration (RTM) method is applied to the single-frequency reconstruction of embedded obstacles in a wall to perform an introductory study for in-wall imaging. The aim is to determine the geometrical properties of an object embedded in a [...] Read more.
In this paper, the reverse time migration (RTM) method is applied to the single-frequency reconstruction of embedded obstacles in a wall to perform an introductory study for in-wall imaging. The aim is to determine the geometrical properties of an object embedded in a wall by the use of an information function provided via the RTM method. The method is based on the computation of that information function separately at each point on a reconstruction domain. It is defined as the correlation levels between the incident fields emitted from sources and the back-propagation of the scattered field. The problem is taken from a broader perspective in order to show and confirm the effectiveness of the method. For this purpose, numerical experiments within a fundamental scenario are determined in a particular order to perform an essential Monte Carlo simulation. The paper uses a comparative study to make an objective evaluation of the achievement level of the method in in-wall imaging. The results reveal that the method is at the applicable level of achievement. Full article
(This article belongs to the Special Issue Microwave Techniques for Spectroscopy and Imaging Applications)
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9 pages, 2100 KiB  
Article
Dynamic Analysis of the Coracohumeral Ligament Using Ultra-Sonography in Shoulder Contracture
by Tatsuo Kato, Atsuyuki Inui, Yutaka Mifune, Hanako Nishimoto, Tomoya Yoshikawa, Issei Shinohara, Takahiro Furukawa, Shuya Tanaka, Masaya Kusunose and Ryosuke Kuroda
Sensors 2023, 23(8), 4015; https://doi.org/10.3390/s23084015 - 15 Apr 2023
Cited by 1 | Viewed by 4222
Abstract
The coracohumeral ligament (CHL) is related to the range of motion of the shoulder joint. The evaluation of the CHL using ultrasonography (US) has been reported on the elastic modulus and thickness of the CHL, but no dynamic evaluation method has been established. [...] Read more.
The coracohumeral ligament (CHL) is related to the range of motion of the shoulder joint. The evaluation of the CHL using ultrasonography (US) has been reported on the elastic modulus and thickness of the CHL, but no dynamic evaluation method has been established. We aimed to quantify the movement of the CHL by applying Particle Image Velocimetry (PIV), a technique used in the field of fluid engineering, to cases of shoulder contracture using the US. The subjects were eight patients, with 16 shoulders. The coracoid process was identified from the body surface, and a long-axis US image of the CHL parallel to the subscapularis tendon was drawn. The shoulder joint was moved from 0 degrees of internal/external rotation to 60 degrees of internal rotation at a rhythm of one reciprocation every 2 s. The velocity of the CHL movement was quantified by the PIV method. The mean magnitude velocity of CHL was significantly faster on the healthy side. The maximum magnitude velocity was significantly faster on the healthy side. The results suggest that the PIV method is helpful as a dynamic evaluation method, and in patients with shoulder contracture, the CHL velocity was significantly decreased. Full article
(This article belongs to the Special Issue Microwave Techniques for Spectroscopy and Imaging Applications)
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17 pages, 43226 KiB  
Article
Fabrication of Ultra-Sharp Tips by Dynamic Chemical Etching Process for Scanning Near-Field Microwave Microscopy
by C. H. Joseph, Giovanni Capoccia, Andrea Lucibello, Emanuela Proietti, Giovanni Maria Sardi, Giancarlo Bartolucci and Romolo Marcelli
Sensors 2023, 23(6), 3360; https://doi.org/10.3390/s23063360 - 22 Mar 2023
Viewed by 1948
Abstract
This work details an effective dynamic chemical etching technique to fabricate ultra-sharp tips for Scanning Near-Field Microwave Microscopy (SNMM). The protruded cylindrical part of the inner conductor in a commercial SMA (Sub Miniature A) coaxial connector is tapered by a dynamic chemical etching [...] Read more.
This work details an effective dynamic chemical etching technique to fabricate ultra-sharp tips for Scanning Near-Field Microwave Microscopy (SNMM). The protruded cylindrical part of the inner conductor in a commercial SMA (Sub Miniature A) coaxial connector is tapered by a dynamic chemical etching process using ferric chloride. The technique is optimized to fabricate ultra-sharp probe tips with controllable shapes and tapered down to have a radius of tip apex around ∼1 μm. The detailed optimization facilitated the fabrication of reproducible high-quality probes suitable for non-contact SNMM operation. A simple analytical model is also presented to better describe the dynamics of the tip formation. The near-field characteristics of the tips are evaluated by finite element method (FEM) based electromagnetic simulations and the performance of the probes has been validated experimentally by means of imaging a metal-dielectric sample using the in-house scanning near-field microwave microscopy system. Full article
(This article belongs to the Special Issue Microwave Techniques for Spectroscopy and Imaging Applications)
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18 pages, 5041 KiB  
Article
A Simple Differential Microwave Imaging Approach for In-Line Inspection of Food Products
by Noemi Zeni, Lorenzo Crocco, Marta Cavagnaro and Gennaro Bellizzi
Sensors 2023, 23(2), 779; https://doi.org/10.3390/s23020779 - 10 Jan 2023
Cited by 6 | Viewed by 2014
Abstract
Microwave imaging has been recently proposed as alternative technology for in-line inspection of packaged products in the food industry, thanks to its non-invasiveness and the low-cost of the equipment. In this framework, simple and effective detection/imaging strategies, able to reveal the presence of [...] Read more.
Microwave imaging has been recently proposed as alternative technology for in-line inspection of packaged products in the food industry, thanks to its non-invasiveness and the low-cost of the equipment. In this framework, simple and effective detection/imaging strategies, able to reveal the presence of foreign bodies that may have contaminated the product during the packaging stage, are needed to allow real-time and reliable detection, thus avoiding delays along the production line and limiting occurrence of false detections (either negative or positive). In this work, a novel detection/imaging approach meeting these requirements is presented. The approach performs the detection/imaging of the contaminant by exploiting the symmetries usually characterizing the food items. Such symmetries are broken by the presence of foreign bodies, thereby determining a differential signal that can be processed to reveal their presence. In so doing, the approach does not require the prior measurement of a reference, defect-free, item. With respect to the quite common case of homogeneous food packaged in circular plastic/glass jars, numerical analyses are provided to show the effectiveness of the proposed approach. Full article
(This article belongs to the Special Issue Microwave Techniques for Spectroscopy and Imaging Applications)
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