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RF Technology for Sensor Applications

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

Deadline for manuscript submissions: closed (28 February 2019) | Viewed by 64340

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Special Issue Editor

Prof. Dr. Sungjoon Lim

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Guest Editor

School of Electrical and Electronics Engineering, Chung-Ang University, Seoul 156-756, Korea
Interests: metamaterial; antenna; electromagnetic sensor; RF origami electroncis
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Microwave/RF sensors have been extensively utilized in diverse applications, such as chemical sensors for homeland security, industry, academia, and, recently, implantable biosensors. For critical applications, such as biomedical, aerospace, security, etc., there is a great need to innovate “selectivity” in RF bio-chemical sensors, so that they exhibit unresponsive behavior toward interfering particles. RF physical sensors (e.g., tactile sensors, strain sensors and crack detection sensors) find useful applications and they have gained widespread popularity because of their integration with laptops, tablets, eBook readers, etc. A continuous progress in RF sensors has been witnessed, thanks to advanced materials, and sophisticated electronics, which have facilitated to realize small sizes and sensitive sensors. Despite several attractive features of RF sensors (for instance, non-invasive, low cost and easily built), there is a need to minimize the gap between research ideas and a marketable product, which is the final goal of a sensor. RF Antennas find ubiquitous applications such as in mobiles, laptops, radio-frequency-identification (RFID), global-positioning-system (GPS) applications, etc., to name a few. Emerging applications have opened new avenues and set new trends for RF antennas, such as reconfigurable, foldable, and low-cost antennas for airborne, machine to machine, internet-of-things (IoT), 5G, vehicle-to-everything (V2X), etc.

The aim of this Special Issue is to surpass the challenges of practical RF components (antennas, and sensors), as well as to contrive antennas and sensing schemes for advanced applications, such as: 1) antennas and sensors for the Internet of things (IoT); 2) 4D printed RF designs; 3) self-calibrated and portable sensors; 4) implantable biosensors; and 5) reconfigurable and low-cost antennas (e.g., origami).

Prof. Sungjoon Lim
Guest Editor

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Keywords

Electromagnetic physical/chemical/bio sensor
Radar sensor
Antenna and RFID for IoT
3D/4D-Printed RF electronics
MEMS

Published Papers (12 papers)

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Research

12 pages, 2682 KiB

Open AccessArticle

Sugar Concentration Measurement System Using Radiofrequency Sensor

by Gerardo Aguila Rodriguez, Nayda Patricia Arias Duque, Blanca Estela Gonzalez Sanchez, Oscar Osvaldo Sandoval Gonzalez, Oscar Hernan Giraldo Osorio, Citlalli Jessica Trujillo Romero, Miriam Andrea Wilches Torres and Jose de Jesus Agustin Flores Cuautle

Sensors 2019, 19(10), 2354; https://doi.org/10.3390/s19102354 - 22 May 2019

Cited by 5 | Viewed by 5557

Abstract

A sugar solution measurement system was developed based on the dielectric properties of the sucrose molecule. An ac conductivity and tan δ study as a function of the frequency was performed to find the suitable frequency range for the measuring system. The results indicate that it is possible to obtain a better response of the sensor using the frequencies as the maxima peak in tan δ appears. Developed setup for sucrose solution was appropriate to measure in a 0.15 to 1 g/mL range with an experimental error of about 3%. The proposed system improves the measurement time over some other methods. Full article

(This article belongs to the Special Issue RF Technology for Sensor Applications)

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10 pages, 3772 KiB

Open AccessArticle

Switchable Bandpass/Bandstop Filter Using Liquid Metal Alloy as Fluidic Switch

by Eiyong Park, Minjae Lee and Sungjoon Lim

Sensors 2019, 19(5), 1081; https://doi.org/10.3390/s19051081 - 03 Mar 2019

Cited by 14 | Viewed by 4075

Abstract

In this paper, we propose a switchable band-pass/band-stop filter using liquid metal alloy as a fluidic switch. The filter is designed based on the Chebyshev response and implemented using a three-stage quarter-wavelength resonant structure. The fluidic switch is realized by injecting eutectic gallium–indium (EGaIn) in the microfluidic stubs, engraved in the polydimethylsiloxane (PDMS) material. When the fluidic switch selects the short stub using a micro-pump and microprocessor for switching, the filter acts as a bandpass filter (BPF) with the short stubs. When the fluidic switch selects the open stub, the filter acts as the bandstop filter (BSF) with the open stubs. At the BPF mode, the center frequency is 2.5 GHz and the 1-dB bandwidth is 1.75–3.07 GHz. The insertion loss is 0.5-dB ± 0.4-dB. At the BSF mode, the 15-dB bandstop bandwidth is 2.4–2.65 GHz with 2.5 GHz center frequency. Full article

(This article belongs to the Special Issue RF Technology for Sensor Applications)

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12 pages, 17892 KiB

Open AccessEditor’s ChoiceArticle

Embedded Smart Antenna for Non-Destructive Testing and Evaluation (NDT&E) of Moisture Content and Deterioration in Concrete

by Kah Hou Teng, Patryk Kot, Magomed Muradov, Andy Shaw, Khalid Hashim, Michaela Gkantou and Ahmed Al-Shamma’a

Sensors 2019, 19(3), 547; https://doi.org/10.3390/s19030547 - 28 Jan 2019

Cited by 67 | Viewed by 6728

Abstract

Concrete failure will lead to serious safety concerns in the performance of a building structure. It is one of the biggest challenges for engineers to inspect and maintain the quality of concrete throughout the service years in order to prevent structural deterioration. To date, a lot of research is ongoing to develop different instruments to inspect concrete quality. Detection of moisture ingress is important in the structural monitoring of concrete. This paper presents a novel sensing technique using a smart antenna for the non-destructive evaluation of moisture content and deterioration inspection in concrete blocks. Two different standard concrete samples (United Kingdom and Malaysia) were investigated in this research. An electromagnetic (EM) sensor was designed and embedded inside the concrete to detect the moisture content within the structure. In addition, CST microwave studio was used to validate the theoretical model of the EM sensor against the test data. The results demonstrated that the EM sensor at 2.45 GHz is capable of detecting the moisture content in the concrete with linear regression of R² = 0.9752. Furthermore, identification of different mix ratios of concrete were successfully demonstrated in this paper. In conclusion, the EM sensor is capable of detecting moisture content non-destructively and could be a potential technique for maintenance and quality control of the building performance. Full article

(This article belongs to the Special Issue RF Technology for Sensor Applications)

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Graphical abstract

16 pages, 4877 KiB

Open AccessCommunication

Design and Analysis of a Quasi-Yagi Antenna for an Indoor Location Tracking System

by Sun-Woong Kim, Sun-Kuk Noh, Ho-Gyun Yu and Dong-You Choi

Sensors 2018, 18(12), 4246; https://doi.org/10.3390/s18124246 - 03 Dec 2018

Cited by 10 | Viewed by 4492

Abstract

In this paper, a quasi-Yagi antenna for an indoor location tracking system is proposed. The performance of the proposed antenna was verified by testing it using an indoor location tracking system. To improve the bandwidth and gain, two parasitic directors were added near the dipole. The performance verification of the proposed antenna is explained, along with a performance comparison of the VSWR (voltage standing wave ratio) radiation pattern and the realized gain. The proposed antenna was connected to an NVA-R661 module of Xethru Inc. for indoor location tracking. The proposed antenna exhibited a wide bandwidth of 4.36 GHz by satisfying a VSWR ≤ 2 from 5.03 to 9.39 GHz, the maximum gain was 6.46 dBi in the 8 GHz band. The radiation pattern exhibited a good directivity characteristic within the proposed band. The location tracking result of a moving target clearly describes the route of the target along a moving line. Full article

(This article belongs to the Special Issue RF Technology for Sensor Applications)

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17 pages, 6072 KiB

Open AccessArticle

A High-Sensitivity Microfluidic Sensor Based on a Substrate Integrated Waveguide Re-Entrant Cavity for Complex Permittivity Measurement of Liquids

by Zhihua Wei, Jie Huang, Jing Li, Guoqing Xu, Zongde Ju, Xuyang Liu and Xingsheng Ni

Sensors 2018, 18(11), 4005; https://doi.org/10.3390/s18114005 - 16 Nov 2018

Cited by 74 | Viewed by 6478

Abstract

In this study, a novel non-invasive and contactless microwave sensor using a square substrate integrated waveguide (SIW) re-entrant cavity is proposed for complex permittivity measurement of chemical solutions. The working principle of this sensor is based on cavity perturbation technique, in which the resonant properties of cavity are utilized as signatures to extract the dielectric information of liquid under test (LUT). A winding microfluidic channel is designed and embedded in the gap region of the cavity to obtain a strong interaction between the induced electric field and LUT, thus achieving a high sensitivity. Also, a mathematical predictive model which quantitatively associates the resonant properties of the sensor with the dielectric constant of LUT is developed through numerical analysis. Using this predictive model, quick and accurate extraction of the complex permittivity of LUT can be easily realized. The performance of this sensor is then experimentally validated by four pure chemicals (hexane, ethyl acetate, DMSO and water) together with a set of acetone/water mixtures in various concentrations. Experimental results demonstrate that the designed sensor is capable of characterizing the complex permittivities of various liquids with an accuracy of higher than 96.76% (compared with the theoretical values obtained by Debye relaxation equations), and it is also available for quantifying the concentration ratio of a given binary mixture. Full article

(This article belongs to the Special Issue RF Technology for Sensor Applications)

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12 pages, 876 KiB

Open AccessArticle

Temperature-Corrected Fluidic Glucose Sensor Based on Microwave Resonator

by Chorom Jang, Jin-Kwan Park, Hee-Jo Lee, Gi-Ho Yun and Jong-Gwan Yook

Sensors 2018, 18(11), 3850; https://doi.org/10.3390/s18113850 - 09 Nov 2018

Cited by 58 | Viewed by 4825

Abstract

In this paper, a fluidic glucose sensor that is based on a complementary split-ring resonator (CSRR) is proposed for the microwave frequency region. The detection of glucose with different concentrations from 0 mg/dL to 400 mg/dL in a non-invasive manner is possible by [...] Read more.

S_{21}

as a sensing parameter. The variation tendency in

S_{21}

by the glucose concentration is analyzed with equivalent circuit model. In addition, to eradicate the systematic error due to temperature variation, the sensor is tested in two temperature conditions: the constant temperature condition and the time-dependent varying temperature condition. For the varying temperature condition, the temperature correction function was derived between the temperature and the variation in

S_{21}

for DI water. By applying the fitting function to glucose solution, the subsidiary results due to temperature can be completely eliminated. As a result, the

S_{21}

varies by 0.03 dB as the glucose concentration increases from 0 mg/dL to 400 mg/dL. Full article

(This article belongs to the Special Issue RF Technology for Sensor Applications)

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11 pages, 5018 KiB

Open AccessArticle

Thermal Frequency Reconfigurable Electromagnetic Absorber Using Phase Change Material

by Heijun Jeong, Jeong-Heum Park, You-Hwan Moon, Chang-Wook Baek and Sungjoon Lim

Sensors 2018, 18(10), 3506; https://doi.org/10.3390/s18103506 - 17 Oct 2018

Cited by 28 | Viewed by 3500

Abstract

In this study, we propose a thermal frequency reconfigurable electromagnetic absorber using germanium telluride (GeTe) phase change material. Thermally-induced phase transition of GeTe from an amorphous high-resistive state to a crystalline low-resistive state by heating is used to change the resonant frequency of the absorber. For full-wave simulation, the electromagnetic properties of GeTe at 25 °C and 250 °C are characterized at 10 GHz under normal incidence for electromagnetic waves. The proposed absorber is designed based on the characterized electromagnetic parameters of GeTe. A circular unit cell is designed and GeTe is placed at a gap in the circle to maximize the switching range. The performance of the proposed electromagnetic absorber is numerically and experimentally demonstrated. Measurement results indicate that the absorption frequency changes from 10.23 GHz to 9.6 GHz when the GeTe film is altered from an amorphous state at room temperature to a crystalline state by heating the sample to 250 °C. The absorptivity in these states is determined to be 91% and 92%, respectively. Full article

(This article belongs to the Special Issue RF Technology for Sensor Applications)

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12 pages, 3467 KiB

Open AccessArticle

Low-Cost and Lightweight 3D-Printed Split-Ring Resonator for Chemical Sensing Applications

by Ahmed Salim, Saptarshi Ghosh and Sungjoon Lim

Sensors 2018, 18(9), 3049; https://doi.org/10.3390/s18093049 - 12 Sep 2018

Cited by 31 | Viewed by 6491

Abstract

In this paper, a microwave cavity resonator is presented for chemical sensing applications. The proposed resonator is comprised of a three dimensional (3D) split-ring resonator (SRR) residing in an external cavity and capacitively coupled by a pair of coaxial probes. 3D-printing technology with polylactic acid (PLA) filament is used to build the 3D SRR and cavity. Then, the surfaces of the SRR and the inside walls of cavity are silver-coated. The novelty of our proposed structure is its light weight and inexpensive design, owing to the utilization of low density and low-cost PLA. A Teflon tube is passed through the split-gap of the SRR so that it is parallel to the applied electric field. With an empty tube, the resonance frequency of the structure is measured at 2.56 GHz with an insertion loss of 13.6 dB and quality factor (Q) of 75. A frequency shift of 205 MHz with respect to the empty channel was measured when deionized water (DIW) was injected into the tube. Using volume occupied by the structure, the weight of the proposed microwave resonator is estimated as 22.8 g which is significantly lighter than any metallic structure of comparable size. Full article

(This article belongs to the Special Issue RF Technology for Sensor Applications)

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9 pages, 2383 KiB

Open AccessArticle

Microfluidically Frequency-Reconfigurable Quasi-Yagi Dipole Antenna

by Syed Imran Hussain Shah and Sungjoon Lim

Sensors 2018, 18(9), 2935; https://doi.org/10.3390/s18092935 - 04 Sep 2018

Cited by 11 | Viewed by 4005

Abstract

In this paper, a frequency reconfigurable quasi-Yagi dipole antenna is proposed by leveraging the properties of microfluidic technology. The proposed antenna comprises a metal-printed driven dipole element and three directors. To tune resonant frequencies, microfluidic channels are integrated into the driven element. To maintain a high gain for all the tuned frequencies, microfluidic channels are also integrated into the directors. Therefore, the length of the driven-element as well as directors can be controlled by injecting liquid metal in the microfluidic channels. The proposed antenna has the capability of tuning the frequency by varying the length of the metal-filled channels, while maintaining a high gain for all the tuned frequencies. The proposed antenna’s performance is experimentally demonstrated after fabrication. The injected amount of liquid metal into the microfluidic channels is controlled using programmable pneumatic micropumps. The prototype exhibits continuous tuning of the resonant frequencies from 1.8 GHz to 2.4 GHz; the measured peak gain of the proposed antenna is varied in the range of 8 dBi to 8.5 dBi. Therefore, continuous tuning with high gain is successfully demonstrated using liquid-metal-filled microfluidic channels. Full article

(This article belongs to the Special Issue RF Technology for Sensor Applications)

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7 pages, 3809 KiB

Open AccessArticle

An Antenna Proximity Sensor for Mobile Terminals Using Reflection Coefficient

by Wonsub Lim, Dongil Yang and Youngoo Yang

Sensors 2018, 18(7), 2103; https://doi.org/10.3390/s18072103 - 30 Jun 2018

Cited by 4 | Viewed by 4507

Abstract

This paper presents a new antenna proximity sensor for mobile terminals based on the measured reflection coefficient using a bidirectional coupler which is positioned between the main antenna and the front-end module. Using the coupled forward and reverse long-term evolution signals by the bidirectional coupler, the reflection coefficient looking into the antenna was calculated in the base-band processor. The measured reflection coefficients showed clear differences for both the types of objects, and the distances between the terminal and the objects. The proposed antenna proximity sensor showed a recognition distance that was approximately 5 mm longer than that of a conventional capacitive proximity sensor. Full article

(This article belongs to the Special Issue RF Technology for Sensor Applications)

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18 pages, 5634 KiB

Open AccessArticle

TM₀₂ Quarter-Mode Substrate-Integrated Waveguide Resonator for Dual Detection of Chemicals

by Ahmed Salim and Sungjoon Lim

Sensors 2018, 18(6), 1964; https://doi.org/10.3390/s18061964 - 18 Jun 2018

Cited by 21 | Viewed by 4473

Abstract

The detection of multiple fluids using a single chip has been attracting attention recently. A TM₀₂ quarter-mode substrate-integrated waveguide resonator designed at 5.81 GHz on RT/duroid 6010LM with a return loss of 13 dB and an unloaded quality factor of Q ≈ 13 generates two distinct strong electric fields that can be manipulated to simultaneously detect two chemicals. Two asymmetric channels engraved in a polydimethylsiloxane sheet are loaded with analyte to produce a unique resonance frequency in each case, regardless of the dielectric constants of the liquids. Keeping in view the nature of lossy liquids such as ethanol, the initial structure and channels are optimized to ensure a reasonable return loss even in the case of loading lossy liquids. After loading the empty channels, Q is evaluated as 43. Ethanol (E) and deionized water (DI) are simultaneously loaded to demonstrate the detection of all possible combinations: [Air, Air], [E, DI], [DI, E], [E, E], and [DI, DI]. The proposed structure is miniaturized while exhibiting a performance comparable to that of existing multichannel microwave chemical sensors. Full article

(This article belongs to the Special Issue RF Technology for Sensor Applications)

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11 pages, 4026 KiB

Open AccessArticle

Design of Inkjet-Printed RFID-Based Sensor on Paper: Single- and Dual-Tag Sensor Topologies

by Sangkil Kim, Apostolos Georgiadis and Manos M. Tentzeris

Sensors 2018, 18(6), 1958; https://doi.org/10.3390/s18061958 - 17 Jun 2018

Cited by 26 | Viewed by 5827

Abstract

The detailed design considerations for the printed RFID-based sensor system is presented in this paper. Starting from material selection and metallization method, this paper discusses types of RFID-based sensors (single- & dual-tag sensor topologies), design procedures, and performance evaluation methods for the wireless sensor system. The electrical properties of the paper substrates (cellulose-based and synthetic papers) and the silver nano-particle-based conductive film are thoroughly characterized for RF applications up to 8 GHz. The reported technology could potentially set the foundation for truly “green”, low-cost, scalable wireless topologies for autonomous Internet-of-Things (IoT), bio-monitoring, and “smart skin” applications. Full article

(This article belongs to the Special Issue RF Technology for Sensor Applications)

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