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The present study proposes an L-shaped coplanar strip dipole antenna for sensing the presence of adulterants in liquid food samples. The proposed antenna dimensions are optimized using ANSYS HFSS, and a prototype is fabricated and validated. The sensing region is optimized based on the current distribution and measured reflection coefficients. Adulterant detection is performed by monitoring the variation in the reflection coefficient and resonance frequency of the antenna sensor. To verify the effectiveness of the proposed planar dipole as a sensor, an adulterant, which is hydrogen peroxide, is added to various liquid samples – milk, pineapple juice, and mango juice. The reflection coefficient of the antenna sensor is found to vary with various concentrations of the samples in the study. The sensitivity analysis of the antenna sensor and the repeatability of the results is also analyzed in the work. The experimental analysis assures the use of the proposed antenna as a sensor for the detection of adulterants in liquid food samples. [ABSTRACT FROM AUTHOR]

This paper reviews microwave sensors and their applications in permittivity measurement. The detection, diagnosis, classification, and monitoring without contact and invasion have been the subject of numerous studies based on permittivity characteristics tracking. This review illustrates many new types of research in recent years. Firstly, the application background is briefly introduced, and several main measurement methods are presented. An overview of measurement technology in various applications is compiled and summarized based on numerous typical examples. Exciting applications are compared and presented separately, combining resonator sensors with strong electric fields. Furthermore, differential signals represent trends for future applications with strong environmental immunity, an alternative option to expensive measuring equipment. With the alternation of metamaterials, microfluidics technologies, cross-technology, algorithms, and so on, sensors play an exceptionally prominent role in practical and low-cost applications. [ABSTRACT FROM AUTHOR]

In the paper, the concept of symmetry is utilized to detect internal defects in Carbon fiber reinforced polymer (CFRP), that is, the reconstruction and localization methods for internal defects in CFRP are symmetrical. CFRP is widely used in industrial, biological and other fields. When there are defects inside the composite materials, its dielectric constant, magnetic permeability, etc. change. Therefore, metamaterial sensors are widely used in non-destructive testing of CFRP Defects. This paper proposes a defect identification and location method based on principal component analysis (PCA) and support vector machine (SVM). The trained model is used to classify the dimensionally reduced data, and the reconstructed defect binary image is obtained. Simulation and physical experiment results show that the method used in this article can effectively identify and locate defects in carbon fiber composite materials. [ABSTRACT FROM AUTHOR]

This paper proposes a single-port interdigital capacitor (IDC) resonator based on asymmetric branch feed line with high stability performance for permittivity detection of solid materials with a permittivity range of 1 - 6.15. The microwave sensor is designed using a single-port resonator operating at two different resonant frequencies $f_{r1} = 1.61$ GHz and $f_{r2} = 2.52$ GHz. Dual band frequency was proposed using asymmetric branch feed line. In addition, to confine the electric field concentration of the resonator, an interdigital capacitor (IDC) structure is proposed as a solution. Furthermore, a copper shield was proposed as conducting material to evaluate performance stability of the sensor from disturbance effect with range of $d = 1$ cm – 2.5 cm. Based on the measurement results, the sensor has high stability both without and with disturbance with an a Frequency Detection Resolution (FDR) of 0.009 - 0.4 GHz/ $\Delta \varepsilon _{\mathrm {r}}$ , a Normalized Sensitivity (NS) of 0.4% - 4.4%, and an average accuracy of 90% - 95% for both resonance frequencies, respectively. Therefore, this sensor can be recommended for several applications such as biomedical industry, pharmaceuticals and material quality control especially for outdoor measurements that are potentially affected by electromagnetic interference and disturbance.

Accurate determination of sodium chloride (NaCl) density in water is vital for assessing environmental impact, preventing soil salinization in agriculture, ensuring quality and consistency in industrial processes, facilitating medical treatments, and maintaining taste and preservation standards in the food and beverage industry. This paper introduces a novel microwave sensor design specifically tailored to accurately assess NaCl density in aqueous solutions. Starting with a standard solution of 10 g of salt dissolved in 100 ml of water, resulting in a molarity of approximately 1.71 M, five distinct samples are meticulously prepared. These samples cover a range of NaCl concentrations, with different ratios of salt solution and drinking water, including pure water, 10 ml of salt solution with 90 ml of water, 20 ml of salt solution with 80 ml of water, 30 ml of salt solution with 70 ml of water, and 40 ml of salt solution with 60 ml of water. Each sample undergoes analysis using the developed microwave sensor to determine its transmission coefficient. The magnitude of the transmission coefficient is closely tied to the density of the salt solution based on molarity. Through a detailed regression analysis, a strong quantitative relationship between the transmission coefficient and salt solution density is revealed. This correlation can be accurately represented by a third-order polynomial equation. This research is significant as it advances microwave sensor technology, allowing for accurate and efficient measurement of NaCl density in water.

The accurate measurement of pulverized coal concentration (PCC) is crucial for optimizing the production efficiency and safety of coal-fired power plants. Traditional microwave attenuation methods typically rely on a single frequency for analysis while neglecting valuable information in the frequency domain, making them susceptible to the varying sensitivity of the signal at different frequencies. To address this issue, we proposed an innovative frequency selection method based on principal component analysis (PCA) and orthogonal matching pursuit (OMP) algorithms and implemented a multi-frequency microwave sensing system for PCC measurement. This method transcended the constraints of single-frequency analysis by employing a developed hardware system to control multiple working frequencies and signal paths. It measured insertion loss data across the sensor cross-section at various frequencies and utilized PCA to reduce the dimensionality of high-dimensional full-path insertion loss data. Subsequently, the OMP algorithm was applied to select the optimal frequency signal combination based on the contribution rates of the eigenvectors, enhancing the measurement accuracy through multi-dimensional fusion. The experimental results demonstrated that the multi-frequency microwave sensing system effectively extracted features from the high-dimensional PCC samples and selected the optimal frequency combination. Filed experiments conducted on five coal mills showed that, within a common PCC range of 0–0.5 kg/kg, the system achieved a minimum mean absolute error (MAE) of 1.41% and a correlation coefficient of 0.85. These results indicate that the system could quantitatively predict PCC and promptly detect PCC fluctuations, highlighting its immediacy and reliability. [ABSTRACT FROM AUTHOR]

In this paper, an inductively coupled capacitively loaded ring resonator (IC-CLRR)-based microwave resonant sensor has been proposed for the accurate identification of any unknown liquid sample and its permittivity estimation. The key element of this work is the sensor's wide range capability towards the non-invasive testing of liquids covering a wide dielectric range of liquid samples, i.e., εr = 2 to 80. The proposed microwave sensor is etched over the FR-4 substrate and is excited by the microstrip line through inductive coupling. The placement of an unknown liquid sample in close proximity to the sensor alters its natural resonant frequency due to a change in effective inductance and capacitance as per the dielectric property of the liquid sample. Further, a mathematical formulation using curve fitting has also been derived. The measurement results show a good accuracy in estimating the permittivity and, thus, the unknown liquid identification capability of the designed sensor with a very low error (nearly 5%). This sensor design is simple to fabricate, cost-friendly, and small in size. [ABSTRACT FROM AUTHOR]

In this paper, we present for the first time a highly sensitive, dual-functional antenna sensor functionalized with molybdenum disulfide/oxide heterostructures (MoS2/MoOx NFs) for selective detection of methanol gas and wireless communications, simultaneously. The proposed antenna sensor uniquely features optimized deposition of the sensing material and structure, allowing sensitive, selective gas detection without interrupting communication. The sensing materials were synthesized via a simple hydrothermal method and characterized using scanning electron microscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy (XPS). XRD and XPS analysis confirmed the formation of MoS2/MoOx heterostructure and indicated the presence of oxide states within the structure. First, the gas sensing ability and electrical properties of MoS2 NF were investigated using chemiresistive transducers. Integrating this with a wideband monopole antenna, a highly sensitive, dual-functional antenna sensor was developed. We optimized the sensing material for sensitivity and tested against volatile organic compounds. Chemiresistive sensors exhibit linear detection but suffer initial fluctuations and baseline shifts at room temperature, which can be mitigated using antenna sensors with RF signals. The sensor demonstrated high selectivity, with methanol producing the strongest response among equal concentrations of methanol, ethanol, isopropanol, and acetone. The developed antenna sensor exhibited high sensitivity of approximately 1 MHz/1000 ppm against methanol. In addition, the calculated detection limit (DL) of the antenna sensor was 52 ppm, which is significantly lower than that of the chemiresistive sensor (799 ppm). The results indicated that with a lower DL than the safety threshold for methanol (200 ppm), the proposed antenna sensor is ideal for monitoring methanol gas in risky indoor environments. Moreover, the sensor's gas sensing capability does not affect the antenna's communication performance, indicating its potential for seamless integration into wireless sensor networks. [ABSTRACT FROM AUTHOR]

Copyright of Electronic Components & Materials is the property of Electronic Components & Materials and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The microstrip devices based on multimode resonators represent a class of electromagnetic microwave devices, promising use in tropospheric communication, radar, and navigation systems. The design of wideband bandpass filters, diplexers, and multiplexers with required frequency-selective properties, i.e., bandpass filters, is a complex problem, as electrodynamic modeling is a time-consuming and computationally intensive process. Various planar microstrip resonator topologies can be developed, differing in their topology type, and the search for high-quality structures with unique frequency-selective properties is an important research direction. In this study, we propose an approach for performing an automated search for multimode resonators' conductor topology parameters using a combination of evolutionary computation approach and surrogate modeling. In particular, a variant of differential evolution optimizer is applied, and the model of the target function landscape is built using Gaussian processes. At every iteration of the algorithm, the model is used to search for new high-quality solutions. In addition, a general approach for target function formulation is presented and applied in the proposed approach. The experiments with two microwave filters have demonstrated that the proposed algorithm is capable of solving the problem of tuning two types of topologies, namely three-mode resonators and six-mode resonators, to the required parameters, and the application of surrogated-assisted algorithm has significantly improved overall performance. [ABSTRACT FROM AUTHOR]

A high-precision multiple parameter measurement sensor based on constitutive parameters nearzero (CPNZ) media has been proposed, which can effectively and accurately predict changes in temperature and relative humidity simultaneously and independently. The dual-channel microwave sensor is composed of a double doping CPNZ substrate integrated waveguide (SIW) cavity, which has the capability to predict different parameters independently. A multi-input and multi-output model is constructed to improve the measurement accuracy by training back propagation (BP) neural network. The relative error of the predicted temperature is smaller than 1.3%, with mean square error (MSE) of ±0.15. The relative error of the predicted relative humidity is smaller than 8.74%, with MSE of ±0.1. The multiple parameter sensor based on CPNZ materials offers a promising platform for multiple parameter sensing research, providing essential technical support and infrastructure for the development of fields like the Internet of Things, intelligent manufacturing, and smart cities. [ABSTRACT FROM AUTHOR]

Glyphosate‐based herbicides are the most used worldwide despite the fact that studies have shown their possible adverse effects on human health and the environment. Since the residues of these herbicides reach water bodies, their detection is considered an emergent research topic. In this work, the use of the intrinsic resonance of a microwave interdigitated capacitor fabricated on microstrip technology, is proposed for detecting the presence of glyphosate‐based herbicide in water. In addition, a sample holder is proposed to avoid the possible oxidation of the metal electrodes due to the direct contact with liquids. The proposed structure was designed to present its first intrinsic resonance at 1.95 GHz so that this resonance is shifted to 1.58 GHz when pure deionized water is used as sample. The sensor device was tested against 18 mixtures prepared with concentrations between 0% and 100% v/v of herbicide diluted in deionized water. Experimental measurements confirm that by using the intrinsic resonance parameters of the proposed structure, is possible to detect the presence of a glyphosate‐based herbicide. Finally, the results confirm the potential of the proposal as an alternative for real‐time, label‐free, and sensitive detection of glyphosate in water and they open the possibility of exploiting its use for the detection of other contaminants. [ABSTRACT FROM AUTHOR]

In this paper, a biosensor utilizing metamaterials is designed and simulated to detect blood glucose concentration. The proposed sensor comprised of a microstrip patch antenna designed on a Rogers RT5880 substrate. A circular-shaped complementary split ring resonator (CSRR) cell is integrated onto the patch of the antenna which acts as the sensing region. The sensor is analyzed in order to ascertain the blood glucose concentration ranging from 50-300 mg/dL in a human finger model. The sensing parameter is amplitude of reflection coefficient, which exhibits variation in response to alterations in the dielectric characteristics of the sample being tested. The Cole-Cole relaxation model is employed to predict the dielectric properties of different finger tissues. An analysis of the characteristics of the CSRR was conducted to illustrate its significance in the realm of glucose detection. The glucose level is determined through the utilization of a linear regression model that describes the relationship between the reflection coefficient of the sensor and glucose level. The sensor demonstrates an impressive sensitivity of 1.792 dB per (mgdL-1) and has the ability of determining glucose levels with a good accuracy, as verified by the application of Clarke error grid. This sensor exhibits enhanced performance compared to some other recent glucose sensors. [ABSTRACT FROM AUTHOR]

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In recent years, several efforts have been dedicated to the development of portable and versatile microwave technologies for contact‐less liquid sensing and characterization. With respect to existing electrochemical and optical approaches, microwave liquid sensors enable high‐sensitivity and label‐free sensing with increased operation stability and robustness, and in relatively simple and inexpensive device formats. Nonetheless, current microwave solution sensing systems are still limited by either their reliance on wired connections to external electronics or by their widespread implementation on conventional rigid substrates. These limitations hinder the seamless integration of such sensors within conventional (micro)fluidic systems for real‐time solution monitoring, particularly when near‐field coupling between the sensors and the liquid under test needs to be established for operation. By leveraging the versatile material deposition capabilities granted by solution‐phase processing, a fully printed and mechanically flexible microwave resonator design is introduced that allows untethered solution sensing whether immersed in or in proximity to the liquid under test. The mechanical properties of this device facilitate the noninvasive/nondestructive integration of the device on commercial tubing. These characteristics, along with its cost‐effectiveness and its ease of fabrication, favor the seamless integration of this device into fluidic and microfluidic systems, for real‐life applications. [ABSTRACT FROM AUTHOR]

In this study, a two-port network-based microwave sensor for liquid characterization is presented. The suggested sensor is built as a miniature microwave resonator using the third iteration of Hilbert's fractal architecture. The suggested structure is used with the T-resonator to raise the sensor quality factor. The suggested sensor is printed on a FR4 substrate and has a footprint of 40 × 60 × 1.6 mm 3 . Analytically, a theoretical investigation is made to clarify how the suggested sensor might function. The suggested sensor is created and put to the test in an experiment. Later, two pans to contain the urine Sample Under Test (SUT) are printed on the sensor. Before loading the SUT, it is discovered that the suggested structure's frequency resonance is 0.46 GHz. An 18 MHz frequency shift is added to the initial resonance after the pans are printed. They monitor the S-parameters in terms of S12 regarding the change in water content in the urine samples, allowing for the sensing component to be completed. As a result, 10 different samples with varying urine percentages are added to the suggested sensor to evaluate its ability to detect the presence of urine. Finally, it is discovered that the suggested process' measurements and corresponding simulated outcomes agreed quite well. [ABSTRACT FROM AUTHOR]

Packaging solutions have recently evolved to become smart and intelligent thanks to technologies such as RFID tracking and communication systems, but the integration of sensing functionality in these systems is still under active development. In this paper, chipless RFID humidity sensors suitable for smart packaging are proposed together with a novel strategy to tune their performances and their operating range. The sensors are flexible, fast, low-cost and easy to fabricate and can be read wirelessly. The sensitivity and the humidity range where they can be used are adjustable by changing one of the sensor's structural parameters. Moreover, these sensors are proposed as double parameter sensors, using both the frequency shift and the intensity variation of the resonance peak for the measure of the relative humidity. The results show that the sensitivity can vary remarkably among the sensors proposed, together with the operative range. The sensor suitability in two specific smart packaging applications is discussed. In the first case, a threshold sensor in the low-humidity range for package integrity verification is analyzed, and in the second case, a more complex measurement of humidity in non-hermetic packages is investigated. The discussion shows that the sensor configuration can easily be adapted to the different application needs. [ABSTRACT FROM AUTHOR]

In this paper, a microwave sensor with a meandered microstrip structure is introduced to measure the permittivity of the various liquids. The performance of the sensor is based on the change of operating resonance frequency during the absence and presence of materials in the sensing area. In this study, liquids including ethanol, methanol, aqueous glucose solution, and deionized water have been selected as samples under test. The proposed sensor has been implemented on RO4003 substrate with dimensions of 35 × 20 × 0.508 mm3 and operating frequency of 6.21 GHz in a free load state with a Q-factor of 506. When the samples are present in the sensing area, the frequency of the sensor shifts from 5.42 to 3.27 GHz. The sensitivity of 0.64% is obtained for the presented sensor. Compact size, linearity of changes, and low cost are the most important advantages of the sensor. The introduced sensor can be used in various fields of industrial, medical, and diagnostic due to its performance. [ABSTRACT FROM AUTHOR]

Dedicated to synchronously acquiring large-area, high-precision, and multi-scale ocean wind and wave information, a novel concept of a spaceborne ocean microwave dual-function integrated sensor is proposed in this paper. It integrates the functions of a scatterometer and SAR by sharing a single phased-array antenna. An overview of the scientific requirements and motivations for the sensor are outlined firstly. In order to fulfill the observation requirements of both the functions, the constraints on the system parameters such as frequency, antenna size, and incidence angle are analyzed. Then, the selection principles of these parameters are discussed within the limitations of antenna area, bandwidth, available time, and cost. Additionally, the constraints on the time sequence of transmitting and receiving pulses are derived to ensure that there is no conflict when the two functions operate simultaneously. Subsequently, a method for jointly designing the pulse repetition frequency (PRF) of both the functions is introduced, along with zebra maps to verify its effectiveness. At the end of the paper, the system and performance parameters of the sensor are given for further insight into it. [ABSTRACT FROM AUTHOR]

A microwave sensor with an inter-digitated structure is proposed to estimate non-invasive blood glucose sensing. The proposed sensor is designed, fabricated and measured for the required specifications. The transmission electromagnetic response is investigated to predict the blood-glucose level. Initially, the effectiveness of the fabricated sensor is demonstrated with the help of controlled experiments, performed in fetal-bovine serum sample solutions. A novel multi-parameter-based sensitivity factor is determined to estimate the blood glucose level. The proposed work showed that a multi-parameter approach may be effectively utilized to determine the blood-glucose level non-invasively. [ABSTRACT FROM AUTHOR]

This paper presents high-sensitivity sensors based on an open complementary square split-ring resonator and a modified open complementary split-ring resonator operating at 4.5 GHz and 3.4 GHz, respectively. The sensors are designed for the detection of multiple liquid materials, including distilled water, methanol, and ethanol. The liquid under test is filled in a glass container loaded using a pipette. Compared to the conventional OCSSRR, the modified OCSSRR with multiple rings exhibits a higher frequency shift of 1200 MHz, 1270 MHz, and 1520 MHz for ethanol, methanol, and distilled water, respectively. The modified sensor also demonstrates a high sensitivity of 308 MHz/RIU for ethanol concentration which is the highest among the existing microwave sensors. The sensors in this manuscript are suitable for multiple liquid-material-sensing applications. [ABSTRACT FROM AUTHOR]

This paper proposed a compact, high-sensitive S-band microwave sensor for low permittivity characterization. The proposed microwave sensor is inspired by a metamaterials-based maze-shaped split-ring resonator (MS-SRR) configuration, and its overall dimensions are 25 mm × 20 mm × 0.79 mm. The unloaded state of the proposed sensor achieved two robust band-stop notches in its transmission response at 2.77 GHz and 3.08 GHz, respectively. These distinctive features enable the real-time measurement of permittivity in low-permittivity materials. The MS-SRR configuration accomplished strong electric-field intensity, which increased the interaction between the field and testing material, resulting in a highly sensitive measurement. A sensitivity of 11.91% is observed for the first resonance peak and 12.01% for the second peak within the permittivity range from 1 to 2.0. Moreover, the proposed sensor is also competent in measuring the permittivity range between 3 and 10 with a sensitivity of 9.47%–4.93% for the first peak and 9.57%–4.83% for the second peak. The resonance frequency shifting by the influence of material under test (MUT) is presented as a function of permittivity using a regression model. The simulated, measured and formulated results agree well. Finally, the proposed compact and high-sensitive microwave sensor holds promise for low permittivity characterization applications.

Maintaining engine oil quality is critical for industrial machinery and transformers to ensure efficient operation and reduce the risk of failure. This paper presents a novel application of an X-band microwave sensor, using a third-order electroformed iris waveguide filter, for real-time, non-invasive engine oil quality monitoring. By detecting shifts in the dielectric properties of engine oil, the sensor accurately tracks oil degradation as it ages. Unlike traditional methods that require oil extraction and laboratory analysis, this sensor enables continuous, in-situ monitoring, providing immediate feedback without disrupting system operations. Any change in oil quality causes a frequency shift, as variations in its dielectric properties affect the waveguide’s resonance. This shift can be measured in real time, enabling accurate monitoring of oil degradation. Additional measurements were conducted using the coaxial probe technique to analyze the changes in the oil’s electrical behavior during various heating periods. Experimental results demonstrate the sensor’s sensitivity, with measurable frequency shifts of up to 10 MHz observed in the most aged oil samples. These shifts clearly correlate with the oil’s aging process, confirming the sensor’s potential for practical use in predictive maintenance. This system, utilizing an electroformed waveguide, offers a cost-effective and efficient solution for enhancing machinery longevity and optimizing maintenance schedules in industrial applications.

Abnormal fluid buildup in the lungs, termed pulmonary edema (PE), is a result of congestive heart failure. It is a life-threatening condition, and early detection and prompt treatment can help save lives. In this article, we demonstrate the feasibility of using a microwave sensor to monitor changes in lung water content and hence detect PE. The research paper utilizes a combination of the Debye and Maxwell models, along with the Cole–Cole equation, to evaluate alterations in the dielectric properties and conductivity of lung tissue. By incorporating elements such as air and water found within the tissue, this dielectric model has been employed to foresee how lung tissues behave when subjected to different levels of hydration and inflation. A printed antenna resonating at 2.4 GHz was designed to work as a sensor. The static dielectric parameters of lung tissue at various water volume fractions were calculated at 2.4 GHz using the Debye–Maxwell model. These parameters were substituted in the Cole–Cole equation to calculate the dielectric constant of lung tissue for different levels of water in the lungs. These values were then substituted in the simulation environment, where the sensor is placed on blocks modeling the human thorax. This work is a first of its kind where the dielectric parameters at different levels of hydration have been previously estimated using mathematical models and substituted accordingly in the modeling environment to test the possibility of detection of PE with high precision. It was observed that the magnitude of the reflection coefficient values changes with increasing water volume fraction, making the microwave method of detection of PE feasible and a reliable technique.

This paper presents a state-of-the-art planar microwave sensor designed for highly precise alcohol characterization in aqueous solutions, with a primary focus on its application in COVID-19 disinfectants. Modified from the Jerusalem patch, the sensor operates at 5.58 GHz, achieving a unique balance between heightened sensitivity and cost-effectiveness. A tailor-made 3D-printed case minimizes errors, securely housing the sensor and feeding tube. The sensor effectively discriminates between ethanol and methanol, revealing a notable 16 MHz frequency gap. In COVID-19 applications, it maintains alcohol percentages at 65–75%, with 1% increments. The paper outlines a mathematical model extracting concentrations with the maximum error of only smaller than 1.81%, affirming the sensor’s precision. Beyond technical prowess, the sensor’s non-destructive nature, real-time monitoring applicability, and freedom from life-cycle limitations mark it as an innovative tool for checking the percentage of alcohol and types of alcohol before using it to kill the virus, contributing significantly to global efforts on disinfectant measurements with noninvasive nature and high precision. This modified Jerusalem sensor stands as a transformative solution, offering unprecedented advantages in design, operational capacity, and broader support for virus-killing applications.

This paper proposes dual functional microwave sensor for displacement and angular detection of liquid material based on electric coupled (ELC) resonator. The proposed resonator uses a two-port band stop filter operating at a resonant frequency of 2.72 GHz. Polystyrene-mm pipe channels are used to accommodate water samples placed in the sensing area of the sensor in the center of the ELC resonator. Displacement and angular detection were observed based on the shift in the resonant frequency of the resonator. Based on the measurement results, the proposed sensor has a sensitivity for displacement detection of 31.5 MHz/cm with a distance range of d =1 – 4 cm while for angular detection it is 0.33 MHz/o with a rotation angle of 0 – 90° for polystyrene-mm pipe channel filled with water content. This paper makes a significant contribution by proposed a dual functional microwave sensor for displacement and angular detection that can be recommended for the automotive, robotics and aerospace industries.

This article proposed a labyrinth shape circular split ring resonator (LC-SRR) based microwave sensor for material permittivity characterization at L to S-band applications. The proposed sensor achieved miniaturized dimensions of only 25 × 20 mm2 by utilizing fractal technology. This new design strategy adopts a unique and compact structure and high electromagnetic (EM) field intensity, contributing to a more precise sensing mechanism in the microwave frequency range. The design geometry achieved resonant frequency at 2.57 GHz with a notch depth of −29.5 dB. The design evolution, metamaterial characteristics, equivalent circuit model, and electric (E) and magnetic (H) fields are presented to understand the stopband characteristics at the resonant frequency. A high sensitivity of 10.50 % is achieved for the proposed sensor for the permittivity range from 1 to 2. The reflection and transmission characteristics of the proposed LC-SRR based sensor are validated by fabricating and measuring the prototype. Moreover, the sensor performance is validated using different dielectric materials (Roger RT5880, Roger RO4350B, and FR-4) The measurement results show consistency with simulation results. Finally, the miniaturized low-profile sensor structure and high sensitivity to characterize the permittivity of the material makes the proposed sensor suitable for low-permittivity sensing applications.

Abstract This study proposes a highly sensitive portable device that utilizes electromagnetic waves and data analytics for instantaneous Severe Acute Respiratory Syndrome CoronaVirus 2 (SARS‐CoV‐2) detection. The device consists of a Radio Frequency (RF) circuit that interprets reflected and transmitted electromagnetic waves to identify virus signatures in physiologically significant matrices, including human saliva and diluted nasopharyngeal swabs. The sensor's accuracy is validated in both pre‐clinical and clinical settings, where clinical measurements demonstrate an instantaneous detection accuracy of 94%, sensitivity of 95%, and specificity of 97.5% between the sensor's physical parameters and SARS‐CoV‐2 detection. The sensor's accurate real‐time response is due to its unique design and precise modeling techniques. In addition, the same sensing system is tested across different viruses and its ability to differentiate between influenza A, respiratory syncytial, and SARS‐CoV‐2 viruses is proven. Hence this work presents a holistic system that can predict the viral concentration of SARS‐CoV‐2, as well as differentiate between different viruses instantaneously and without adding any amplifying agent.

Micro direct methanol fuel cells (μDMFCs) are a promising power source for microelectronic devices and systems. As the operating state and performance of a μDMFC is generally determined by both electrochemical polarization and methanol crossover, it is important to monitor the methanol concentration in μDMFCs. Here, we design and fabricate a microwave sensor and integrate it with a μDMFC for the online detection of methanol concentration in a nonintrusive way. The sensing area is set at the bottom of the anode chamber of a μDMFC which exhibits a maximum output power density of 28.8 mW cm−2 at 30 °C. With a square ring structure, the dual-mode microwave sensor shows a sensitivity of 9.5 MHz mol−1 L. Furthermore, the importance of methanol concentration monitoring is demonstrated in the long term. A relatively smooth methanol decline curve was obtained, which indicated a normal and stable operating status of the μDMFC. Derived from real-time recording data, fuel utilization was additionally calculated as 28.5%. [ABSTRACT FROM AUTHOR]

In this work, a real-time label-free microwave sensing mechanism for glucose concentration monitoring using a planar biosensor configured with an inset fed microstrip patch antenna has been demonstrated. A microstrip patch antenna with the resonating frequency of 1.45 GHz has been designed and is fabricated on the Flame Retardant (FR-4) substrate. Due to the intense electromagnetic field at the edges of the patch antenna, edge length has been used as the detecting area where the sample under test (SUT) interacts with the electromagnetic field. The Poly-Dimethyl-Siloxane (PDMS) with the trench in the centre has been employed as the sample holder. Here, the SUT is the glucose dissolved in DI (de-ionized) water with the concentration range of 0.2 to 0.6 g/mL. The dielectric constant dependency on the glucose concentration has been used as the distinguishing factor which results in a shift in the S-parameter. The experimentally measured RF parameters were observed closely which showed the shift in S11 magnitude from –40 to –15 dB and resonant frequency from 1.27 to 1.3 GHz w.r.t the SUT solution of 0.2 to 0.6 g/mL with linear regression coefficient of 0.881, and 0.983 respectively.

This article reports a microstrip spurline sensor for glucose concentration monitoring. The microstrip spurline sensor is a low-cost and easy-to-fabricate device that uses printed circuit board (PCB) technology. It consists of a combination of four spurlines and transmission lines. The four spurlines are used to reject unwanted frequencies, while the transmission lines allow the desired frequencies to pass through. The resonance frequency (Fr) and reflection coefficient (S11) were recorded through meticulous simulations and experiments over a frequency range from 1.5 GHz to 4 GHz. In addition, the sensor was used to detect changes in glucose concentration, ranging from 0 mg/dL to 150 mg/dL. The findings of this study show that the antenna-based sensor proposed in this research can effectively measure glucose levels across the diabetes range, from hypoglycemia to normoglycemia to hyperglycemia, with a high degree of sensitivity of 7.82 x 10−3 dB/(mg/dL) and 233.33 kHz/(mg/dL).

A chipless RFID humidity sensor suitable for smart packaging is proposed in this work. The sensor is flexible, fast, low-cost, easy to fabricate and can be read wirelessly. The results show a very high sensitivity in the low-humidity range (1–10%), making it especially suited to monitor and establish package integrity. [ABSTRACT FROM AUTHOR]

We investigate the response bandwidth of a superheterodyne Rydberg receiver at a room-temperature vapor cell, and present an architecture of multi-channel lasers excitation to increase the response bandwidth and keep sensitivity, simultaneously. Two microwave fields, denoted as a local oscillator (LO) E LO and a signal field E SIG , couple two Rydberg states transition of | 52 D 5 / 2 〉 → | 53 P 3 / 2 〉 . In the presence of the LO field, the frequency difference between two fields can be read out as an intermediate frequency (IF) signal using Rydberg electromagnetically induced transparency (EIT) spectroscopy. The bandwidth of the Rydberg receiver is obtained by measuring the output power of IF signal versus the frequency difference between two fields. The bandwidth dependence on the Rabi frequency of excitation lasers is presented, which shows the bandwidth decrease with the probe Rabi frequency, while it is quadratic dependence on the coupling Rabi frequency. Meanwhile, we investigate the effect of probe laser waist on the bandwidth, showing that the bandwidth is inversely proportional to the laser waist. We achieve a maximum response bandwidth of the receiver about 6.8 MHz. Finally, we design an architecture of multi-channel lasers excitation for increasing the response and keeping the sensitivity, simultaneously. Our work has the potential to extend the applications of Rydberg atoms in communications. [ABSTRACT FROM AUTHOR]