Research

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20 pages, 3731 KiB

Open AccessArticle

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 - 07 Jul 2023

Cited by 22 | Viewed by 1661

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

Open AccessArticle

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 10 | Viewed by 1874

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

λ_{g - m i n} / 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

Open AccessArticle

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 8 | Viewed by 2705

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

Open AccessArticle

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 4 | Viewed by 3598

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

Open AccessArticle

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 2133

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

Open AccessEditor’s ChoiceArticle

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 26 | Viewed by 2967

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

Open AccessEditor’s ChoiceArticle

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 39 | Viewed by 3454

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

f_{res} = 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

f_{res} = 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

S_{11}

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

V^{5 +}

and fully discharged

V^{4 +}

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

Open AccessReview

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 43 | Viewed by 3866

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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