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4 pages, 149 KiB

Open AccessEditorial

RF, Microwave, and Millimeter Wave Devices and Circuits and Their Applications

by Reza K. Amineh

Electronics 2025, 14(14), 2844; https://doi.org/10.3390/electronics14142844 - 16 Jul 2025

Viewed by 295

The recent progress in the development of cost-effective, compact, and highly integrated high-frequency circuits in the RF, microwave, and millimeter-wave domains has significantly broadened the scope of these technologies across both traditional and emerging application areas [...] Full article

(This article belongs to the Special Issue RF, Microwave, and Millimeter Wave Devices and Circuits and Their Applications)

19 pages, 5086 KiB

Open AccessArticle

Expedited Near-Field Holographic Microwave Imaging with an Azimuthally Distributed Antenna Array

by Mona Heydari and Reza K. Amineh

Electronics 2025, 14(13), 2518; https://doi.org/10.3390/electronics14132518 - 20 Jun 2025

Viewed by 661

Abstract

In this article, we propose a novel near-field holographic microwave imaging technique designed to accelerate the data acquisition process. The system employs a novel electronic switching mechanism utilizing two switching networks that virtually rotate the transmitting and receiving antennas along the azimuthal direction [...] Read more.

In this article, we propose a novel near-field holographic microwave imaging technique designed to accelerate the data acquisition process. The system employs a novel electronic switching mechanism utilizing two switching networks that virtually rotate the transmitting and receiving antennas along the azimuthal direction for efficient data collection. This minimizes the need for mechanical scanning of the antennas which, in turn, leads to faster data acquisition. To enhance the quality of the imaging outcome, the number of samples can be increased by combining only a few mechanical scanning steps with the electronic scanning. This data acquisition scheme leverages the system’s space-invariant property to enable convolution-based near-field holographic microwave image reconstruction. By capturing and processing scattered fields over a cylindrical aperture, the system achieves high-resolution imaging of concealed objects across multiple range positions. Both simulation and experimental results validate the effectiveness of the proposed approach in delivering high-quality imaging results. Its ability to provide faster and enhanced imaging outcomes highlights its potential for a wide range of applications, including biomedical imaging, security screening, and non-destructive testing of the materials. Full article

(This article belongs to the Special Issue RF, Microwave, and Millimeter Wave Devices and Circuits and Their Applications)

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16 pages, 2037 KiB

Open AccessArticle

Elbow Gesture Recognition with an Array of Inductive Sensors and Machine Learning

by Alma Abbasnia, Maryam Ravan and Reza K. Amineh

Sensors 2024, 24(13), 4202; https://doi.org/10.3390/s24134202 - 28 Jun 2024

Cited by 4 | Viewed by 1393

Abstract

This work presents a novel approach for elbow gesture recognition using an array of inductive sensors and a machine learning algorithm (MLA). This paper describes the design of the inductive sensor array integrated into a flexible and wearable sleeve. The sensor array consists [...] Read more.

This work presents a novel approach for elbow gesture recognition using an array of inductive sensors and a machine learning algorithm (MLA). This paper describes the design of the inductive sensor array integrated into a flexible and wearable sleeve. The sensor array consists of coils sewn onto the sleeve, which form an LC tank circuit along with the externally connected inductors and capacitors. Changes in the elbow position modulate the inductance of these coils, allowing the sensor array to capture a range of elbow movements. The signal processing and random forest MLA to recognize 10 different elbow gestures are described. Rigorous evaluation on 8 subjects and data augmentation, which leveraged the dataset to 1270 trials per gesture, enabled the system to achieve remarkable accuracy of 98.3% and 98.5% using 5-fold cross-validation and leave-one-subject-out cross-validation, respectively. The test performance was then assessed using data collected from five new subjects. The high classification accuracy of 94% demonstrates the generalizability of the designed system. The proposed solution addresses the limitations of existing elbow gesture recognition designs and offers a practical and effective approach for intuitive human–machine interaction. Full article

(This article belongs to the Special Issue Combining Machine Learning and Sensors in Human Movement Biomechanics)

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19 pages, 5403 KiB

Open AccessArticle

Real-Time Nitrate Ion Monitoring with Poly(3,4-ethylenedioxythiophene) (PEDOT) Materials

by Michael C. Kohler, Fang Li, Ziqian Dong and Reza K. Amineh

Sensors 2023, 23(17), 7627; https://doi.org/10.3390/s23177627 - 3 Sep 2023

Cited by 3 | Viewed by 2157

Abstract

Nitrate (NO₃) pollution in groundwater, caused by various factors both natural and synthetic, contributes to the decline of human health and well-being. Current techniques used for nitrate detection include spectroscopic, electrochemical, chromatography, and capillary electrophoresis. It is highly desired to develop [...] Read more.

Nitrate (NO₃) pollution in groundwater, caused by various factors both natural and synthetic, contributes to the decline of human health and well-being. Current techniques used for nitrate detection include spectroscopic, electrochemical, chromatography, and capillary electrophoresis. It is highly desired to develop a simple cost-effective alternative to these complex methods for nitrate detection. Therefore, a real-time poly (3,4-ethylenedioxythiophene) (PEDOT)-based sensor for nitrate ion detection via electrical property change is introduced in this study. Vapor phase polymerization (VPP) is used to create a polymer thin film. Variations in specific parameters during the process are tested and compared to develop new insights into PEDOT sensitivity towards nitrate ions. Through this study, the optimal fabrication parameters that produce a sensor with the highest sensitivity toward nitrate ions are determined. With the optimized parameters, the electrical resistance response of the sensor to 1000 ppm nitrate solution is 41.79%. Furthermore, the sensors can detect nitrate ranging from 1 ppm to 1000 ppm. The proposed sensor demonstrates excellent potential to detect the overabundance of nitrate ions in aqueous solutions in real time. Full article

(This article belongs to the Special Issue Advances in Micro/Nanofabrication and Smart Biomaterials for HealthCare Systems)

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16 pages, 6093 KiB

Open AccessArticle

Near-Field Imaging of Dielectric Components Using an Array of Microwave Sensors

by Yuki Gao, Maryam Ravan and Reza K. Amineh

Electronics 2023, 12(6), 1507; https://doi.org/10.3390/electronics12061507 - 22 Mar 2023

Cited by 5 | Viewed by 2953

Abstract

Microwave imaging is a high-resolution, noninvasive, and noncontact method for detecting hidden defects, cracks, and objects with applications for testing nonmetallic components such as printed circuit boards, biomedical diagnosis, aerospace components inspection, etc. In this paper, an array of microwave sensors designed based [...] Read more.

Microwave imaging is a high-resolution, noninvasive, and noncontact method for detecting hidden defects, cracks, and objects with applications for testing nonmetallic components such as printed circuit boards, biomedical diagnosis, aerospace components inspection, etc. In this paper, an array of microwave sensors designed based on complementary split ring resonators (CSRR) are used to evaluate the hidden features in dielectric media with applications in nondestructive testing and biomedical diagnosis. In this array, each element resonates at a different frequency in the range of 1 GHz to 10 GHz. Even though the operating frequencies are not that high, the acquisition of evanescent waves in extreme proximity to the imaged object and processing them using near-field holographic imaging allows for obtaining high-resolution images. The performance of the proposed method is demonstrated through simulation and experimental results. Full article

(This article belongs to the Special Issue Applications of RF/Microwave/Millimeter-Wave/THz Imaging)

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16 pages, 10269 KiB

Open AccessArticle

Software Defined Radio-Based Wireless Sensing System

by Yihan Xu, Reza K. Amineh, Ziqian Dong, Fang Li, Kayla Kirton and Michael Kohler

Sensors 2022, 22(17), 6455; https://doi.org/10.3390/s22176455 - 26 Aug 2022

Cited by 9 | Viewed by 4509

Abstract

In this paper, we investigate the application of using software-defined radio (SDR) and surface acoustic wave (SAW) device for wireless measurement of the response of in situ sensors. SDR uses software to realize different communication functions. After collecting the magnitude and phase of [...] Read more.

In this paper, we investigate the application of using software-defined radio (SDR) and surface acoustic wave (SAW) device for wireless measurement of the response of in situ sensors. SDR uses software to realize different communication functions. After collecting the magnitude and phase of the response at discrete frequencies, we apply inverse Fourier transform to analyze the time domain responses which, in turn, allows for monitoring the changes of the response of the in situ sensor. We employ microwave signal flow graph concepts to improve the quality of the received signals. Comparing the normalized results obtained by SDR with those obtained from a commercial vector network analyzer (VNA), we demonstrate that the results are sufficiently close, and the SDR-based experiments can provide satisfactory measurement of the in-situ sensors. The objective is to eventually employ this wireless measurement system for soil nutrient sensing. Full article

(This article belongs to the Special Issue Electromagnetic Structures for Sensing Applications)

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16 pages, 3309 KiB

Open AccessArticle

Wearable Inductive Sensing of the Arm Joint: Comparison of Three Sensing Configurations

by Armanda Byberi, Reza K. Amineh and Maryam Ravan

Magnetism 2022, 2(3), 195-210; https://doi.org/10.3390/magnetism2030015 - 23 Jun 2022

Cited by 10 | Viewed by 2966

Abstract

Currently, there is a rapidly growing interest and demand for wearable textile sensors that can monitor human motions in a naturalistic environment. Some potential applications for this technology include research on measuring the motor skill performance of patients with motor disabilities such as [...] Read more.

Currently, there is a rapidly growing interest and demand for wearable textile sensors that can monitor human motions in a naturalistic environment. Some potential applications for this technology include research on measuring the motor skill performance of patients with motor disabilities such as autism spectrum disorder, Parkinson’s disease, cerebral palsy, and stroke and evaluating the efficacy of applied treatments. Among wearable sensors, inductive sensors that are made from highly conductive threads are attractive due to their easy development process, high reliability, and low cost. In this study, we analyzed and compared the performance of three inductive wearable sensor configurations—(1) single planar rectangular coil, (2) two separated coils connected in series, and (3) two helical coils connected in series—in terms of the change in the resonant frequency of the tank circuit they comprised as a result of the change in elbow joint angle through simulations. Three parameters of length, width, and the number of turns were considered to calculate sensor sensitivity to the joint angle. The coil with the highest sensitivity was then fabricated and measured, and its performance was compared with the simulation results. The proposed methodology can be extended to sensing other joints in the body such as the shoulders, fingers, and knees. Full article

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10 pages, 1828 KiB

Open AccessArticle

Fast and Robust Capacitive Imaging of Cylindrical Non-Metallic Media

by Noshin Raisa, Yuki Gao, Mahindra Ganesh, Maryam Ravan and Reza K. Amineh

Magnetism 2021, 1(1), 60-69; https://doi.org/10.3390/magnetism1010006 - 3 Dec 2021

Cited by 1 | Viewed by 3601

Abstract

In this paper, a unique approach to the imaging of non-metallic media using capacitive sensing is presented. By using customized sensor plates in single-ended and differential configurations, responses to hidden objects can be captured over a cylindrical aperture surrounding the inspected medium. Then, [...] Read more.

In this paper, a unique approach to the imaging of non-metallic media using capacitive sensing is presented. By using customized sensor plates in single-ended and differential configurations, responses to hidden objects can be captured over a cylindrical aperture surrounding the inspected medium. Then, by processing the acquired data using a novel imaging technique based on the convolution theory, Fourier and inverse Fourier transforms, and exact low resolution electromagnetic tomography (eLORETA), images are reconstructed over multiple radial depths using the acquired sensor data. Imaging hidden objects over multiple depths has wide range of applications, from biomedical imaging to nondestructive testing of the materials. Performance of the proposed imaging technique is demonstrated via experimental results. Full article

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15 pages, 6787 KiB

Open AccessArticle

Fast, Robust, and Low-Cost Microwave Imaging of Multiple Non-Metallic Pipes

by Yuki Gao, Maryam Ravan and Reza K. Amineh

Electronics 2021, 10(15), 1762; https://doi.org/10.3390/electronics10151762 - 23 Jul 2021

Cited by 12 | Viewed by 3573

Abstract

The use of non-metallic pipes and composite components that are low-cost, durable, light-weight, and resilient to corrosion is growing rapidly in various industrial sectors such as oil and gas industries in the form of non-metallic composite pipes. While these components are still prone [...] Read more.

The use of non-metallic pipes and composite components that are low-cost, durable, light-weight, and resilient to corrosion is growing rapidly in various industrial sectors such as oil and gas industries in the form of non-metallic composite pipes. While these components are still prone to damages, traditional non-destructive testing (NDT) techniques such as eddy current technique and magnetic flux leakage technique cannot be utilized for inspection of these components. Microwave imaging can fill this gap as a favorable technique to perform inspection of non-metallic pipes. Holographic microwave imaging techniques are fast and robust and have been successfully employed in applications such as airport security screening and underground imaging. Here, we extend the use of holographic microwave imaging to inspection of multiple concentric pipes. To increase the speed of data acquisition, we utilize antenna arrays along the azimuthal direction in a cylindrical setup. A parametric study and demonstration of the performance of the proposed imaging system will be provided. Full article

(This article belongs to the Special Issue Applications of Electromagnetic Waves, Volume II)

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4 pages, 166 KiB

Open AccessEditorial

Applications of Electromagnetic Waves: Present and Future

by Reza K. Amineh

Electronics 2020, 9(5), 808; https://doi.org/10.3390/electronics9050808 - 15 May 2020

Cited by 13 | Viewed by 16074

Abstract

Electromagnetic (EM) waves carry energy through propagation in space [...] Full article

(This article belongs to the Special Issue Applications of Electromagnetic Waves)

12 pages, 5844 KiB

Open AccessArticle

Material Identification Using a Microwave Sensor Array and Machine Learning

by Luke Harrsion, Maryam Ravan, Dhara Tandel, Kunyi Zhang, Tanvi Patel and Reza K. Amineh

Electronics 2020, 9(2), 288; https://doi.org/10.3390/electronics9020288 - 8 Feb 2020

Cited by 20 | Viewed by 5316

Abstract

In this paper, a novel methodology is proposed for material identification. It is based on the use of a microwave sensor array with the elements of the array resonating at various frequencies within a wide range and applying machine learning algorithms on the [...] Read more.

In this paper, a novel methodology is proposed for material identification. It is based on the use of a microwave sensor array with the elements of the array resonating at various frequencies within a wide range and applying machine learning algorithms on the collected data. Unlike the previous microwave sensing systems which are mainly based on a single resonating sensor, the proposed methodology allows for material characterization over a wide frequency range which, in turn, improves the accuracy of the material identification procedure. The performance of the proposed methodology is tested via the use of easily available materials such as woods, cardboards, and plastics. However, the proposed methodology can be extended to other applications such as industrial liquid identification and composite material identification, among others. Full article

(This article belongs to the Special Issue Applications of Electromagnetic Waves)

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20 pages, 9400 KiB

Open AccessFeature PaperArticle

A Low-Cost and Compact Three-Dimensional Microwave Holographic Imaging System

by Hailun Wu and Reza K. Amineh

Electronics 2019, 8(9), 1036; https://doi.org/10.3390/electronics8091036 - 15 Sep 2019

Cited by 18 | Viewed by 3965

Abstract

With the significant growth in the use of non-metallic composite materials, the demands for new and robust non-destructive testing methodologies is high. Microwave imaging has attracted a lot of attention recently for such applications. This is in addition to the biomedical imaging applications [...] Read more.

With the significant growth in the use of non-metallic composite materials, the demands for new and robust non-destructive testing methodologies is high. Microwave imaging has attracted a lot of attention recently for such applications. This is in addition to the biomedical imaging applications of microwave that are also being pursued actively. Among these efforts, in this paper, we propose a compact and cost-effective three-dimensional microwave imaging system based on a fast and robust holographic technique. For this purpose, we employ narrow-band microwave data, instead of wideband data used in previous three-dimensional cylindrical holographic imaging systems. Three-dimensional imaging is accomplished by using an array of receiver antennas surrounding the object and scanning that along with a transmitter antenna over a cylindrical aperture. To achieve low cost and compact size, we employ off-the-shelf components to build a data acquisition system replacing the costly and bulky vector network analyzers. The simulation and experimental results demonstrate the satisfactory performance of the proposed imaging system. We also show the effect of number of frequencies and size of the objects on the quality of reconstructed images. Full article

(This article belongs to the Special Issue Applications of Electromagnetic Waves)

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