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State-of-the-Art Technologies in Microwave Sensors

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

Deadline for manuscript submissions: closed (10 May 2023) | Viewed by 28663

Special Issue Editors


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Guest Editor
Department of Electrical and Computer Engineering, University of Toronto, Toronto, Canada
Interests: Active Microwave Sensors; Machine Learning; Biochemical Sensing; RF Circuits and Wireless power transmission

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Guest Editor
School of Advanced Technology, Iran University of Science and Technology, Tehran, Iran
Interests: Material Characterization; Microwave Circuits; Artificial Intelligence
Special Issues, Collections and Topics in MDPI journals

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Guest Editor
CIMITEC, Departament d'Enginyeria Electrònica, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain
Interests: microwave sensors; microwave circuits; metamaterials; RFID
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

It’s been a while that microwave sensors have been employed in various applications, from agriculture and environmental monitoring to the biomedical industry. The basis of their operation is benefited from the nature of electromagnetic wave interaction with different media, namely, non-destructive sensing, thereby enabling sensing and measuring various targets.

Development in microwave sensing techniques includes novel deployment of planar passive resonant elements (e.g. SRR/CSRR), substrate integrated waveguide, antenna, active component, imprinted polymer, doppler radar sensor, whispering gallery mode, lab-on-chip platform, and more recently, intriguing application of artificial neural network in pursuit of smart sensors. Ever-growing investigations on these methodologies are tied with additional challenges in modern industry, whereas low cost and flexibility in design urge delving into more sophisticated and efficient architectures.

This special issue of State-of-Art Technologies in Microwave Sensors focuses on the latest updates in developing microwave sensors and sensing systems that aim to resolve the problems associated with emerging sensing techniques, possibly its integration with sensing network at a higher system level, and enabling demanding and impactful applications.

Dr. Mohammad Abdolrazzaghi
Prof. Dr. Vahid Nayyeri
Prof. Dr. Ferran Martín
Guest Editors

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Keywords

  • Microwave Sensor
  • Novel Techniques for Impriving Sensor Performance
  • Material Characterization
  • Sensor Networks
  • Sub-surface Detection
  • Crack Detection
  • Biosensors
  • Sensors for IoT
  • Sensors for motion control applications
  • Sensors for agriculture and food industry
  • RFID-based sensors
  • Machine Learning and Deep Learning
  • Active and Passive Sensors
  • Remote/Non-invasive Interrogation

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Published Papers (8 papers)

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Research

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20 pages, 3731 KiB  
Article
AI-Assisted Ultra-High-Sensitivity/Resolution Active-Coupled CSRR-Based Sensor with Embedded Selectivity
by Mohammad Abdolrazzaghi, Nazli Kazemi, Vahid Nayyeri and Ferran Martin
Sensors 2023, 23(13), 6236; https://doi.org/10.3390/s23136236 - 7 Jul 2023
Cited by 40 | Viewed by 2414
Abstract
This research explores the application of an artificial intelligence (AI)-assisted approach to enhance the selectivity of microwave sensors used for liquid mixture sensing. We utilized a planar microwave sensor comprising two coupled rectangular complementary split-ring resonators operating at 2.45 GHz to establish a [...] Read more.
This research explores the application of an artificial intelligence (AI)-assisted approach to enhance the selectivity of microwave sensors used for liquid mixture sensing. We utilized a planar microwave sensor comprising two coupled rectangular complementary split-ring resonators operating at 2.45 GHz to establish a highly sensitive capacitive region. The sensor’s quality factor was markedly improved from 70 to approximately 2700 through the incorporation of a regenerative amplifier to compensate for losses. A deep neural network (DNN) technique is employed to characterize mixtures of methanol, ethanol, and water, using the frequency, amplitude, and quality factor as inputs. However, the DNN approach is found to be effective solely for binary mixtures, with a maximum concentration error of 4.3%. To improve selectivity for ternary mixtures, we employed a more sophisticated machine learning algorithm, the convolutional neural network (CNN), using the entire transmission response as the 1-D input. This resulted in a significant improvement in selectivity, limiting the maximum percentage error to just 0.7% (≈6-fold accuracy enhancement). Full article
(This article belongs to the Special Issue State-of-the-Art Technologies in Microwave Sensors)
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20 pages, 9685 KiB  
Article
Selective Microwave Zeroth-Order Resonator Sensor Aided by Machine Learning
by Nazli Kazemi, Nastaran Gholizadeh and Petr Musilek
Sensors 2022, 22(14), 5362; https://doi.org/10.3390/s22145362 - 18 Jul 2022
Cited by 13 | Viewed by 2267
Abstract
Microwave sensors are principally sensitive to effective permittivity, and hence not selective to a specific material under test (MUT). In this work, a highly compact microwave planar sensor based on zeroth-order resonance is designed to operate at three distant frequencies of 3.5, 4.3, [...] Read more.
Microwave sensors are principally sensitive to effective permittivity, and hence not selective to a specific material under test (MUT). In this work, a highly compact microwave planar sensor based on zeroth-order resonance is designed to operate at three distant frequencies of 3.5, 4.3, and 5 GHz, with the size of only λgmin/8 per resonator. This resonator is deployed to characterize liquid mixtures with one desired MUT (here water) combined with an interfering material (e.g., methanol, ethanol, or acetone) with various concentrations (0%:10%:100%). To achieve a sensor with selectivity to water, a convolutional neural network (CNN) is used to recognize different concentrations of water regardless of the host medium. To obtain a high accuracy of this classification, Style-GAN is utilized to generate a reliable sensor response for concentrations between water and the host medium (methanol, ethanol, and acetone). A high accuracy of 90.7% is achieved using CNN for selectively discriminating water concentrations. Full article
(This article belongs to the Special Issue State-of-the-Art Technologies in Microwave Sensors)
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17 pages, 1003 KiB  
Article
A Novel Coupling Mechanism for CSRRs as Near-Field Dielectric Sensors
by Ali M. Albishi
Sensors 2022, 22(9), 3313; https://doi.org/10.3390/s22093313 - 26 Apr 2022
Cited by 9 | Viewed by 3187
Abstract
This work proposes a novel coupling mechanism for a complementary split-ring resonator as a planar near-field microwave sensor for dielectric materials. The resonator is etched into the ground plane of a microstrip line. This mechanism is based on the inductive coupling synthesized by [...] Read more.
This work proposes a novel coupling mechanism for a complementary split-ring resonator as a planar near-field microwave sensor for dielectric materials. The resonator is etched into the ground plane of a microstrip line. This mechanism is based on the inductive coupling synthesized by utilizing a via that connects the power plane of the microstrip line to the central island of the resonator. The proposed coupling makes the coupling capacitance between the transmission line and the resonator relatively small and insignificant compared to the capacitance of the resonator, making it more sensitive to changes in the dielectric constant of the materials under test. In addition, the coupling is no longer dependent solely on the capacitive coupling, which significantly reduces the coupling degradation caused by loading the resonator with dielectric materials, so the inductive coupling plays an important role in the proposed design. Therefore, the proposed coupling mechanism improves the sensitivity and enhances the coupling between the transmission line and the resonator. The sensor is evaluated for sensitivity, normalized resonance shift, and coupling factor using a full-wave numerical simulation. The sensitivity of the proposed sensor is 12% and 5.6% when detecting dielectric constants of 2 and 10, respectively. Compared to recent studies, the sensitivity improvement when detecting similar permittivity is 20% (1.32 times) and 9.8% (1.1 times). For verification, the proposed sensor is manufactured using PCB technology and is used to detect the presence of two dielectric laminates. Full article
(This article belongs to the Special Issue State-of-the-Art Technologies in Microwave Sensors)
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13 pages, 1723 KiB  
Article
Batteryless, Miniaturized Implantable Glucose Sensor Using a Fluorescent Hydrogel
by Hyeonkeon Lee, Jongheon Lee, Honghyeon Park, Mi Song Nam, Yun Jung Heo and Sanghoek Kim
Sensors 2021, 21(24), 8464; https://doi.org/10.3390/s21248464 - 18 Dec 2021
Cited by 6 | Viewed by 4152
Abstract
We propose a biomedical sensor system for continuous monitoring of glucose concentration. Despite recent advances in implantable biomedical devices, mm sized devices have yet to be developed due to the power limitation of the device in a tissue. We here present a mm [...] Read more.
We propose a biomedical sensor system for continuous monitoring of glucose concentration. Despite recent advances in implantable biomedical devices, mm sized devices have yet to be developed due to the power limitation of the device in a tissue. We here present a mm sized wireless system with backscattered frequency-modulation communication that enables a low-power operation to read the glucose level from a fluorescent hydrogel sensor. The configuration of the reader structure is optimized for an efficient wireless power transfer and data communication, miniaturizing the entire implantable device to 3 × 6 mm 2 size. The operation distance between the reader and the implantable device reaches 2 mm with a transmission power of 33 dBm. We demonstrate that the frequency of backscattered signals changes according to the light intensity of the fluorescent glucose sensor. We envision that the present wireless interface can be applied to other fluorescence-based biosensors to make them highly comfortable, biocompatible, and stable within a body. Full article
(This article belongs to the Special Issue State-of-the-Art Technologies in Microwave Sensors)
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27 pages, 15851 KiB  
Article
Hardware Implementation and RF High-Fidelity Modeling and Simulation of Compressive Sensing Based 2D Angle-of-Arrival Measurement System for 2–18 GHz Radar Electronic Support Measures
by Chen Wu, Denesh Krishnasamy and Janaka Elangage
Sensors 2021, 21(20), 6823; https://doi.org/10.3390/s21206823 - 14 Oct 2021
Cited by 1 | Viewed by 2485
Abstract
This article presents the hardware implementation and a behavioral model-based RF system modeling and simulation (M&S) study of compressive sensing (CS) based 2D angle-of-arrival (AoA) measurement system for 2–18 GHz radar electronic support measures (RESM). A 6-channel ultra-wideband RF digital receiver was first [...] Read more.
This article presents the hardware implementation and a behavioral model-based RF system modeling and simulation (M&S) study of compressive sensing (CS) based 2D angle-of-arrival (AoA) measurement system for 2–18 GHz radar electronic support measures (RESM). A 6-channel ultra-wideband RF digital receiver was first developed using a PXIe-based multi-channel digital receiver paired with a 6-element random-spaced 2D cavity-backed-spiral-antenna array. Then the system was tested in an open lab environment. The measurement results showed that the system can measure AoA of impinging signals from 2–18 (GHz) with overall RMSE of estimation at 3.60, 2.74, 1.16, 0.67 and 0.56 (deg) in L, S, C, X and Ku bands, respectively. After that, using the RF high-fidelity M&S (RF HF-M&S) approach, a 6-channel AoA measurement system behavioral model was also developed and studied using a radar electronic warfare (REW) engagement scenario. The simulation result showed that the airborne AoA measurement system could successfully measure an S-band ground-based target acquisition radar signal in the dynamic REW environment. Using the RF HF-M&S model, the applicability of the system in other frequencies within 2–18 (GHz) was also studied. The simulation results demonstrated that the airborne AoA measurement system can be used for 2–18 GHz RESM applications. Full article
(This article belongs to the Special Issue State-of-the-Art Technologies in Microwave Sensors)
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13 pages, 1482 KiB  
Article
Extremely Sensitive Microwave Microfluidic Dielectric Sensor Using a Transmission Line Loaded with Shunt LC Resonators
by Haneen Abdelwahab, Amir Ebrahimi, Francisco J. Tovar-Lopez, Grzegorz Beziuk and Kamran Ghorbani
Sensors 2021, 21(20), 6811; https://doi.org/10.3390/s21206811 - 13 Oct 2021
Cited by 29 | Viewed by 3389
Abstract
In this paper, a very high sensitivity microwave-based planar microfluidic sensor is presented. Sensitivity enhancement is achieved and described theoretically and experimentally by eliminating any extra parasitic capacitance not contributing to the sensing mechanism. The sensor consists of a microstrip transmission line loaded [...] Read more.
In this paper, a very high sensitivity microwave-based planar microfluidic sensor is presented. Sensitivity enhancement is achieved and described theoretically and experimentally by eliminating any extra parasitic capacitance not contributing to the sensing mechanism. The sensor consists of a microstrip transmission line loaded with a series connected shunt LC resonator. A microfluidic channel is attached to the area of the highest electric field concentration. The electric field distribution and, therefore, the resonance characteristics are modified by applying microfluidic dielectric samples to the sensing area. The sensor performance and working principle are described through a circuit model analysis. A device prototype is fabricated, and experimental measurements using water/ethanol and water/methanol solutions are presented for validation of the sensing mathematical model. Full article
(This article belongs to the Special Issue State-of-the-Art Technologies in Microwave Sensors)
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14 pages, 6066 KiB  
Article
A High-Resolution Reflective Microwave Planar Sensor for Sensing of Vanadium Electrolyte
by Nazli Kazemi, Kalvin Schofield and Petr Musilek
Sensors 2021, 21(11), 3759; https://doi.org/10.3390/s21113759 - 28 May 2021
Cited by 40 | Viewed by 3883
Abstract
Microwave planar sensors employ conventional passive complementary split ring resonators (CSRR) as their sensitive region. In this work, a novel planar reflective sensor is introduced that deploys CSRRs as the front-end sensing element at fres=6 GHz with an extra loss-compensating [...] Read more.
Microwave planar sensors employ conventional passive complementary split ring resonators (CSRR) as their sensitive region. In this work, a novel planar reflective sensor is introduced that deploys CSRRs as the front-end sensing element at fres=6 GHz with an extra loss-compensating negative resistance that restores the dissipated power in the sensor that is used in dielectric material characterization. It is shown that the S11 notch of −15 dB can be improved down to −40 dB without loss of sensitivity. An application of this design is shown in discriminating different states of vanadium redox solutions with highly lossy conditions of fully charged V5+ and fully discharged V4+ electrolytes. Full article
(This article belongs to the Special Issue State-of-the-Art Technologies in Microwave Sensors)
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Review

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57 pages, 60380 KiB  
Review
Techniques to Improve the Performance of Planar Microwave Sensors: A Review and Recent Developments
by Mohammad Abdolrazzaghi, Vahid Nayyeri and Ferran Martin
Sensors 2022, 22(18), 6946; https://doi.org/10.3390/s22186946 - 14 Sep 2022
Cited by 59 | Viewed by 4760
Abstract
Planar microwave sensors have become increasing developed in recent decades, especially in material characterization (solid/liquid) as they provide regions highly sensitive to the surrounding medium. However, when it comes to deciphering the content of practical biological analytes or chemical components inside a host [...] Read more.
Planar microwave sensors have become increasing developed in recent decades, especially in material characterization (solid/liquid) as they provide regions highly sensitive to the surrounding medium. However, when it comes to deciphering the content of practical biological analytes or chemical components inside a host medium, even higher sensitivities are required due to their minute concentrations. This review article presents a comprehensive outlook on various methodologies to enhance sensitivity (e.g., coupling resonators, channel embedding, analyte immobilization, resonator pattern recognition, use of phase variation, using coupled line section, and intermodulation products), resolution (active sensors, differential measurements), and robustness (using machine learning) of arbitrary sensors of interest. Some of the most practical approaches are presented with prototype examples, and the main applications of incorporating such procedures are reported. Sensors with which the proposed techniques are implemented exhibit higher performance for high-end and real-life use. Full article
(This article belongs to the Special Issue State-of-the-Art Technologies in Microwave Sensors)
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