Sensors

Editorial

Jump to: Research

7 pages, 216 KiB

Open AccessEditorial

Microwave Sensors Based on Resonant Elements

by Ferran Martín, Paris Vélez and Marta Gil

Sensors 2020, 20(12), 3375; https://0-doi-org.brum.beds.ac.uk/10.3390/s20123375 - 15 Jun 2020

Cited by 18 | Viewed by 3694

Abstract

This paper highlights interest in the implementation of microwave sensors based on resonant elements, the subject of a special issue in the journal. A classification of these sensors on the basis of the operating principle is presented, and the advantages and limitations of [...] Read more.

This paper highlights interest in the implementation of microwave sensors based on resonant elements, the subject of a special issue in the journal. A classification of these sensors on the basis of the operating principle is presented, and the advantages and limitations of the different sensor types are pointed out. Finally, the paper summarizes the different contributions to the special issue. Full article

(This article belongs to the Special Issue Microwave Sensors Based on Resonant Elements)

Research

Jump to: Editorial

15 pages, 4032 KiB

Open AccessArticle

Simplified Approach to Detect Dielectric Constant Using a Low-Cost Microfluidic Quarter Mode Substrate-Integrated Waveguide

by Ahmed Salim, Muhammad Usman Memon, Heijun Jeong and Sungjoon Lim

Sensors 2020, 20(17), 4985; https://0-doi-org.brum.beds.ac.uk/10.3390/s20174985 - 02 Sep 2020

Cited by 6 | Viewed by 2817

Abstract

Liquid materials’ characterization using commercial probes and radio frequency techniques is expensive and complex. This study proposes a compact and cost-effective radio frequency sensor system to measure the dielectric constant using a three-material calibration. The simplified approach measures reflection coefficient magnitudes for all [...] Read more.

Liquid materials’ characterization using commercial probes and radio frequency techniques is expensive and complex. This study proposes a compact and cost-effective radio frequency sensor system to measure the dielectric constant using a three-material calibration. The simplified approach measures reflection coefficient magnitudes for all four materials rather than the complex values in conventional permittivity detection systems. We employ a sensor module based on a circular substrate-integrated waveguide with measured unloaded quality factor = 910 to ensure measurement reliability. Miniaturized quarter-mode substrate-integrated waveguide resonators are integrated with four microfluidic channels containing three known materials and one unknown analyte. Step-wise measurement and linearity ensures maximum 4% error for the dielectric constant compared with results obtained using a high-performance commercial product. Full article

(This article belongs to the Special Issue Microwave Sensors Based on Resonant Elements)

► Show Figures

Figure 1

11 pages, 3296 KiB

Open AccessArticle

Microwave Differential Frequency Splitting Sensor Using Magnetic-LC Resonators

by Amir Ebrahimi, Grzegorz Beziuk, James Scott and Kamran Ghorbani

Sensors 2020, 20(4), 1066; https://0-doi-org.brum.beds.ac.uk/10.3390/s20041066 - 15 Feb 2020

Cited by 58 | Viewed by 3691

Abstract

A differential microwave permittivity sensor and comparator is designed using a microstrip transmission line loaded with a magnetic-LC resonator. The microstrip transmission line is aligned with the electric wall of the resonator. The sensor shows a single transmission zero, when it is unloaded [...] Read more.

A differential microwave permittivity sensor and comparator is designed using a microstrip transmission line loaded with a magnetic-LC resonator. The microstrip transmission line is aligned with the electric wall of the resonator. The sensor shows a single transmission zero, when it is unloaded or loaded symmetrically on both halves. A second notch appears in the transmission response by asymmetrical dielectric loading on the two halves of the device. The frequency splitting is used to characterize the dielectric properties of the samples under test. The sensitivity of the sensor is enhanced by removing the mutual coupling between the two halves of the magnetic-LC resonator using a metallic wall. The sensors’ operation principle is explained through a circuit model analysis. A prototype of the designed sensor is fabricated and measurements are used for validation of the sensing concept. The sensor can be used for determination of the dielectric properties in solid materials or detecting defects and impurities in solid materials through a comparative measurement with a reference sample. Full article

(This article belongs to the Special Issue Microwave Sensors Based on Resonant Elements)

► Show Figures

Figure 1

13 pages, 6110 KiB

Open AccessArticle

Development of a Resonant Microwave Sensor for Sediment Density Characterization

by R. Mansour, S. Rioual, B. Lescop, P. Talbot, M. Abboud, W. Farah and G. Tanné

Sensors 2020, 20(4), 1058; https://doi.org/10.3390/s20041058 - 15 Feb 2020

Cited by 6 | Viewed by 2332

Abstract

In this study, a sensor based on the development of a planar antenna immersed in sediments dedicated to water content monitoring in this type of material is proposed and experimentally validated. It is produced by a conventional Printed Circuit Board (PCB) manufacturing process [...] Read more.

In this study, a sensor based on the development of a planar antenna immersed in sediments dedicated to water content monitoring in this type of material is proposed and experimentally validated. It is produced by a conventional Printed Circuit Board (PCB) manufacturing process on a double-sided metalized FR4 substrate. The sensitivity of the sensor is ensured by the variation of the real part of the complex dielectric permittivity of sediments with water content at around 1 GHz. As shown, in this frequency range, electrode polarization and Maxwell–Wagner polarization effects become negligible, leading to only a bulk water polarization sensitivity. The sensor operates in the reflection mode by monitoring the variation of the resonant frequency as a function of the sediment density through the S₁₁ reflection measurements. An experimental sensitivity of

820 MHz . g^{- 1} . {cm}^{3}

was achieved. Despite the simplification of data interpretation at the considered frequency, the influence of ionic species such as NaCl in sediments on the real part of the relative complex dielectric permittivity is highlighted. This demonstrates the importance of considering a second parameter such as the S₁₁ level at low frequency or the electrical conductivity to extract the density from the frequency measurements. Full article

(This article belongs to the Special Issue Microwave Sensors Based on Resonant Elements)

► Show Figures

Figure 1

13 pages, 6009 KiB

Open AccessArticle

Design of Substrate-Integrated Waveguide Loading Multiple Complementary Open Resonant Rings (CSRRs) for Dielectric Constant Measurement

by Honggang Hao, Dexu Wang and Zhu Wang

Sensors 2020, 20(3), 857; https://0-doi-org.brum.beds.ac.uk/10.3390/s20030857 - 06 Feb 2020

Cited by 11 | Viewed by 3644

Abstract

In order to solve the low-sensitivity problem of the dielectric constant with the resonant cavity method, a sensor based on a substrate-integrated waveguide structure loaded with a multi-complementary open resonant ring is proposed. With the enhanced resonance characteristics of the sensor, this design [...] Read more.

In order to solve the low-sensitivity problem of the dielectric constant with the resonant cavity method, a sensor based on a substrate-integrated waveguide structure loaded with a multi-complementary open resonant ring is proposed. With the enhanced resonance characteristics of the sensor, this design realized the measurement of complex dielectric constants in a wide range. The frequency selectivity of the sensor is improved by the high-quality factor of the substrate-integrated waveguide. By loading three complementary resonant rings with different opening directions in the ground plane, a deeper notch and better out-of-band suppression are achieved. The effect of the complex dielectric constant on both resonant frequency and quality factor is discussed by calculating the material under test with a known dielectric constant. Simulation and experimental results show that a resonance frequency offset of 102 MHz for the per unit dielectric constant is achieved. A wide frequency offset is the prerequisite for accurate measurement. The measurement results of four plates match well with the standard values, with a relative error of the real part of the dielectric constant of less than 2% and an error of less than 0.0099 for the imaginary part. Full article

(This article belongs to the Special Issue Microwave Sensors Based on Resonant Elements)

► Show Figures

Figure 1

16 pages, 5266 KiB

Open AccessArticle

CSRR-Based Microwave Sensor for Dielectric Materials Characterization Applied to Soil Water Content Determination

by João G. D. Oliveira, Erica N. M. G. Pinto, Valdemir P. Silva Neto and Adaildo G. D’Assunção

Sensors 2020, 20(1), 255; https://0-doi-org.brum.beds.ac.uk/10.3390/s20010255 - 01 Jan 2020

Cited by 45 | Viewed by 6434

Abstract

A new and compact sensor based on the complementary split-ring resonator (CSRR) structure is proposed to characterize the relative permittivity of various dielectric materials, enabling the determination of soil water content (SWC). The proposed sensor consists of a circular microstrip patch antenna supporting [...] Read more.

A new and compact sensor based on the complementary split-ring resonator (CSRR) structure is proposed to characterize the relative permittivity of various dielectric materials, enabling the determination of soil water content (SWC). The proposed sensor consists of a circular microstrip patch antenna supporting a 3D-printed small cylindrical container made out of Acrylonitrile-Butadiene-Styrene (ABS) filament. The principle of operation is based on the shifting of two of the antenna resonant frequencies caused by changing the relative permittivity of the material under test (MUT). Simulations are performed enabling the development of an empirical model of analysis. The sensitivity of the sensor is investigated and its effectiveness is analyzed by characterizing typical dielectric materials. The proposed sensor, which can be applied to characterize different types of dielectric materials, is used to determine the percentage of water contained in different soil types. Prototypes are fabricated and measured and the obtained results are compared with results from other research works, to validate the proposed sensor effectiveness. Moreover, the sensor was used to determine the percentage of water concentration in quartz sand and red clay samples. Full article

(This article belongs to the Special Issue Microwave Sensors Based on Resonant Elements)

► Show Figures

Figure 1

12 pages, 4088 KiB

Open AccessArticle

A Compact Double-Folded Substrate Integrated Waveguide Re-Entrant Cavity for Highly Sensitive Humidity Sensing

by Zhihua Wei, Jie Huang, Jing Li, Junshan Li, Xuyang Liu and Xingsheng Ni

Sensors 2019, 19(15), 3308; https://0-doi-org.brum.beds.ac.uk/10.3390/s19153308 - 27 Jul 2019

Cited by 15 | Viewed by 3549

Abstract

In this study, an ultra-compact humidity sensor based on a double-folded substrate integrated waveguide (SIW) re-entrant cavity was proposed and analyzed. By folding a circular re-entrant cavity twice along its two orthogonally symmetric planes, the designed structure achieved a remarkable size reduction (up [...] Read more.

In this study, an ultra-compact humidity sensor based on a double-folded substrate integrated waveguide (SIW) re-entrant cavity was proposed and analyzed. By folding a circular re-entrant cavity twice along its two orthogonally symmetric planes, the designed structure achieved a remarkable size reduction (up to 85.9%) in comparison with a conventional TM₀₁₀-mode circular SIW cavity. The operating principle of the humidity sensor is based on the resonant method, in other words, it utilizes the resonant properties of the sensor as signatures to detect the humidity condition of the ambient environment. To this end, a mathematical model quantitatively relating the resonant frequency of the sensor and the relative humidity (RH) level was established according to the cavity perturbation theory. The sensing performance of the sensor was experimentally validated in a RH range of 30%–80% by using a humidity chamber. The measured absolute sensitivity of the sensor was calculated to be 135.6 kHz/%RH, and the corresponding normalized sensitivity was 0.00627%/%RH. It was demonstrated that our proposed sensor not only has the merits of compact size and high sensitivity, but also benefits from a high Q-factor and ease of fabrication and integration. These advantages make it an excellent candidate for humidity sensing applications in various fields such as the agricultural, pharmaceutical, and food industries. Full article

(This article belongs to the Special Issue Microwave Sensors Based on Resonant Elements)

► Show Figures

Figure 1

18 pages, 3350 KiB

Open AccessArticle

Differential Microfluidic Sensors Based on Dumbbell-Shaped Defect Ground Structures in Microstrip Technology: Analysis, Optimization, and Applications

by Paris Vélez, Jonathan Muñoz-Enano, Marta Gil, Javier Mata-Contreras and Ferran Martín

Sensors 2019, 19(14), 3189; https://0-doi-org.brum.beds.ac.uk/10.3390/s19143189 - 19 Jul 2019

Cited by 50 | Viewed by 3730

Abstract

A microstrip defect ground structure (DGS) based on a pair of dumbbell-shaped slots is used for sensing. The device is a differential sensor consisting of a pair of mirrored lines loaded with a dumbbell-shaped DGS, and the output variable is the cross-mode transmission [...] Read more.

A microstrip defect ground structure (DGS) based on a pair of dumbbell-shaped slots is used for sensing. The device is a differential sensor consisting of a pair of mirrored lines loaded with a dumbbell-shaped DGS, and the output variable is the cross-mode transmission coefficient. Such a variable is very sensitive to asymmetries in the line pair, e.g., caused by an asymmetric dielectric load in the dumbbell-shaped DGSs. Therefore, the sensor is of special interest for the dielectric characterization of solids and liquids, or for the measurement of variables related to complex permittivity changes. It is shown in this work that by adding fluidic channels on top of the dumbbell-shaped DGSs, the device is useful for liquid characterization, particularly for the measurement of solute concentration in very diluted solutions. A sensitivity analysis useful for sensor design is carried out in this paper. Full article

(This article belongs to the Special Issue Microwave Sensors Based on Resonant Elements)

► Show Figures

Figure 1

Journal Menu

Journal Browser

Microwave Sensors Based on Resonant Elements

Share This Special Issue

Special Issue Editors

Special Issue Information

Keywords

Published Papers (8 papers)

Editorial

Research

Further Information

Guidelines

MDPI Initiatives

Follow MDPI