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Altres ajuts: ICREA award A microfluidic sensor based on a microstrip line loaded with a composite resonator is reported in this paper. The composite resonator combines a shunt connected step impedance resonator (SIR) and a complementary split ring resonator CSRR) etched in the ground plane. By etching the CSRR beneath the patch of the SIR, the composite CSRR-loaded SIR resonator exhibits two transmission zeros and a pole in between. The operating principle of the sensor is the variation of the transmission coefficient at the pole frequency of the bare resonator, when a material or liquid under test (LUT) is in contact with the CSRR (the sensitive element). By designing the CSRR-loaded SIR resonator with closely spaced pole and transmission zeros, highly sensitive sensors are obtained. Despite the fact that the proposed sensor can also operate as a frequency variation sensor, using it as a single-frequency sensor based on the variation of the transmission coefficient (caused by the LUT) at a specific frequency reduces sensor costs. The reason is that a harmonic signal injected to the input port of the microstrip-based sensor plus a simple amplitude modulation (AM) detector (connected to the output port) suffices for measuring purposes. The proposed microfluidic sensor is applied to the characterization of volume fraction of solutions of isopropanol in deionized (DI) water. The sensor is able to resolve volume fractions as small as 5%, and the maximum measured sensitivity is as good as 4 mV/%.

A novel W-band sensor for complex permittivity measurements of rod shaped samples based on reflectometer method is described. Characterization of dielectric materials around 100 GHz is quite a challenge. The main limitation is the requirements for the accuracy of the dimensions of the test sample and ensuring good contact with conductive surfaces. From this point of view, it seems interesting to use a cylindrical waveguide with the TE01 mode. The four linearly-polarized H10 fields of rectangular waveguides with equal amplitude and phase circumnavigate the cylindrical waveguide to jointly excite its TEnm circular modes with four-fold symmetry. This precludes the excitation of lower-order modes of the metallic cylindrical waveguide. TE01 mode is unique in that its field leads to zero on the surface of the walls of a metallic cylindrical waveguide. The main field interaction takes place on the sample surface. The calibration method uses calibration curves obtained by simulation for known values of complex permittivity of the samples. This eliminates the requirement for a precision calibration standards, which is the problematic to realize at millimeter wavelengths. Moreover, the complex field structure in the sensor makes it impossible to apply a standard calibration method. Simulation and measurements using these method have been performed in W-band (70–114 GHz). Measurement results demonstrate the robustness of this new sensor for characterizing rod shaped dielectric samples.

The detection of chemical samples having close dielectric response is a big challenge as the detection principle is driven by the variations in the dielectric parameters of the investigated samples. In the current work, a new metamaterial-based sensor is designed and fabricated in order to be used for the detection of liquid chemicals in the frequency range from 8 to 12 GHz. Several designs were tested using genetic algorithm, which is embedded in the CST microwave studio, in order to optimize the desired dimensions of the resonator. The simulation and experimental results showed that the proposed sensor is working well to detect various liquids, including (i) clean and waste transformer oils, (ii) corn, cotton and olive oils, (iii) branded and unbranded diesels and (iv) aniline doped ethyl-alcohol and benzene doped carbon tetrachloride. This was made possible through the occurrence of a shift in the resonant frequency of about 250 MHz, 200 MHz, 250 MHz, 150 MHz and 50 MHz for the aforementioned samples, respectively. The sensing mechanism was interpreted through the surface current and electric field distributions. We believe that the proposed sensor is viable to be used in various applications including liquid chemicals detection and industrial applications. © 2020 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

This paper presents an overview of the use of additive manufacturing (AM) technologies for the implementation of microwave components. Two major technological solutions, based on the AM of plastic materials, are discussed: in the former case, the AM plastic is used as a dielectric material that constitutes the component. Conversely, in the latter case, the plastic material is a mere support of the metallization, thus avoiding the contact of the AM plastic with the electromagnetic field and reducing losses. Several examples are illustrated and discussed, to highlight benefits and limitations of AM techniques in the current scenario of microwave applications.

In this work, a new design for a real-time noninvasive metamaterial sensor, based on a corona-shaped resonator, is proposed. The sensor was designed numerically and fabricated experimentally in order to be utilized for efficient detection of glucose in aqueous solutions such as water and blood. The sensor was inspired by a corona in-plane-shaped design with the presumption that its circular structure might produce a broader interaction of the electromagnetic waves with the glucose samples. A clear shift in the resonance frequency was observed for various glucose samples, which implies that the proposed sensor has a good sensitivity and can be easily utilized to distinguish any glucose concentration, even though their dielectric coefficients are close. Results showed a superior performance in terms of resonance frequency shift (1.51 GHz) and quality factor (246) compared to those reported in the literature. The transmission variation level ∆|S21| was investigated for glucose concentration in both water and blood. The sensing mechanism was elaborated through the surface current, electric field and magnetic field distributions on the corona resonator. The proposed metamaterials sensor is considered to be a promising candidate for biosensor and medicine applications in human glycaemia monitoring.

Linear discriminant analysis (LDA) is a mathematically robust multivariate data analysis approach that is sometimes used for surface oil slick signature classification. Our goal is to rank the effectiveness of LDAs to differentiate oil spills from look-alike slicks. We explored multiple combinations of (i) variables (size information, Meteorological-Oceanographic (metoc), geo-location parameters) and (ii) data transformations (non-transformed, cube root, log10). Active and passive satellite-based measurements of RADARSAT, QuikSCAT, AVHRR, SeaWiFS, and MODIS were used. Results from two experiments are reported and discussed: (i) an investigation of 60 combinations of several attributes subjected to the same data transformation and (ii) a survey of 54 other data combinations of three selected variables subjected to different data transformations. In Experiment 1, the best discrimination was reached using ten cube-transformed attributes: ~85% overall accuracy using six pieces of size information, three metoc variables, and one geo-location parameter. In Experiment 2, two combinations of three variables tied as the most effective: ~81% of overall accuracy using area (log transformed), length-to-width ratio (log- or cube-transformed), and number of feature parts (non-transformed). After verifying the classification accuracy of 114 algorithms by comparing with expert interpretations, we concluded that applying different data transformations and accounting for metoc and geo-location attributes optimizes the accuracies of binary classifiers (oil spill vs. look-alike slicks) using the simple LDA technique.

Sensing motion and distinguishing its source as human or nonhuman, with high precision, has tremendous applications in a variety of areas from health monitoring to energy efficiency. One strategy to achieve this goal is to detect the small motion of breathing, which is a consistent indicator of human presence. Among the many smart sensing schemes proposed, microwave and RF sensors have shown great promise due to their simplicity, privacy, and effective range. In this paper, we propose the use of a dynamic metasurface antenna (DMAs) as an alternative hardware platform for sensing motion inside a residential setting using microwave signals. The proposed device is a single-port planar cavity that excites an array of electronically-tunable metamaterial elements. The DMA can generate spatially diverse patterns at a single frequency, avoiding complexities related to wideband operation or high hardware costs of antenna arrays. We demonstrate that it is capable of detecting minute movements, such as breathing emulated by a mannequin, to distinguish human presence. This motion can be detected whether the target is in the the sensor's direct line of sight or out of the direct line of sight. Furthermore, we show that the DMA sensing platform requires a single noise-floor calibration and can operate in different room geometries or configurations (e.g. when furniture is displaced). The proposed DMA-sensor with its single frequency operation and simple hardware is an appealing alternative hardware for intruder detection, human presence detection/activity recognition in smart homes, or seamless health monitoring.

Metamaterials are engineered periodic structures designed to have unique properties not encountered in naturally occurring materials. One such unusual property of metamaterials is the ability to exhibit negative refractive index over a prescribed range of frequencies. A lens made of negative refractive index metamaterials can achieve resolution beyond the diffraction limit. This paper presents the design of a metamaterial lens and its use in far-field microwave imaging for subwavelength defect detection in nondestructive evaluation (NDE). Theoretical formulation and numerical studies of the metamaterial lens design are presented followed by experimental demonstration and characterization of metamaterial behavior. Finally, a microwave homodyne receiver-based system is used in conjunction with the metamaterial lens to develop a far-field microwave NDE sensor system. A subwavelength focal spot of size 0.82λ was obtained. The system is shown to be sensitive to a defect of size 0.17λ × 0.06λ in a Teflon sample. Consecutive positions of the defect with a separation of 0.23λ was resolvable using the proposed system.

Planar microwave angular displacement and angular velocity sensors implemented in microstrip technology are proposed. The transducer element is a circularly shaped divider/combiner, whereas the sensing element is an electric-LC resonator, attached to the rotating object and magnetically coupled to the circular (active) region of the transducer. The angular variables are measured by inspection of the transmission characteristics, which are modulated by the magnetic coupling between the resonator and the divider/combiner. The degree of coupling is hence sensitive to the angular position of the resonator. As compared with coplanar waveguide angular displacement and velocity sensors, the proposed microstrip sensors do not require air bridges, and the ground plane provides backside isolation.

In this work, a triple hexagonal split ring resonator incorporated metamaterial sensor is proposed for the improved detection of fuel adulteration. The proposed metamaterial structure is made of three resonators, acting to gather the effective capacitive and inductive properties whereby any trivial variations in the dielectric properties of the system can be readily correlated with the shift in the resonance frequency. The advanced design system and computer simulation technology software were used to measure the transmission coefficient, followed by numerical and experimental investigations. The proposed sensor was validated on petrol, kerosene and grease samples having different contents and humidity levels. Results showed a noticeable shift in the resonance frequency of the samples upon changing their concentration and humidity. The sensor was able to provide an improved sensitivity and a high-quality factor of 291. The proposed design can be used for the real time applications in the frequency range from 1 to 20 GHz.

This article is focused on the analysis and modeling of coplanar waveguide (CPW) transmission lines loaded with multisection stepped impedance resonators (MS-SIRs), transversely etched on the back substrate side. The considered structure consists of a CPW loaded with a 5-section SIR (5S-SIR) with wide (capacitive) central and external sections cascaded with narrow (inductive) sections. The general case of a 5S-SIR with arbitrary lengths and widths of the different sections is considered. The structure is described by a pair of inductively coupled grounded series resonators coupled to the line through the capacitance of the central 5S-SIR section. If the structure is symmetric, the transmission coefficient exhibits a single transmission zero. Hence, these structures can be used as notch filters exhibiting wide bandwidths, provided the inductance of the 5S-SIR can be made small, and the capacitance can be enhanced by virtue of the broadside coupling. However, if symmetry is broken, two notches separated a distance that depends on the level of asymmetry and inductive coupling appear. Therefore, these structures are also useful for the implementation of differential sensors and comparators. The proposed model is validated through parameter extraction and experiment, and a proof-of-concept of a comparator is reported.

This work presents, for the first time, an in-situ self-aligned fluidic-integrated microwave sensor for characterizing NaCl contents in NaCl-aqueous solution based on a 16-GHz bandpass combline cavity resonator. The discrimination of the NaCl concentration is achievable by determining amplitude differences and resonant frequency translations between the incident and reflected microwave signals at the input terminal of the cavity resonator based on the capacitive loading effects of the comb structure inside the cavity introduced by the NaCl solution under test. Twelve NaCl-aqueous liquid mixture samples with different NaCl concentrations ranging from 0% to 20% (0 - 200 mg/mL), which are generally exploited in most industrial and biomedical applications, were prepared and encapsulated inside a Teflon tube performing as a fluidic channel. The Teflon tube is subsequently inserted into the cavity resonator through two small holes, fabricated through the sidewalls of the cavity, which can be used to automatically align the fluidic subsystem inside the combline resonator considerably easing the sensor setup. Based on at least five repeated measurements, the NaCl sensor can discriminate the NaCl content of as low as 1% with the measurement accuracy of higher than 96% and the maximum standard deviation of only 0.0578. There are several significant advantages achieved by the novel NaCl sensors, e.g. high accuracy, traceability and repeatability; ease of sensor setup and integration to actual industrial and biomedical systems enabling in-situ and real-time measurements; noninvasive and noncontaminative liquid solution characterization as well as superior sensor reusability due to a complete physical separation between the fluidic and microwave subsystems.

This article presents a new approach to determining liquid concentration using a new microwave sensor and polarity correlator. The sensor design incorporates an annular ring resonator having inside three parallel lines, a trapezoid ground plane and a co-planar waveguide (CPW) tapered feeder, which altogether achieve multiple frequency bands. Multiple bands of interest are obtained at the lower end of the microwave spectrum, i.e., from 1&ndash, 6 GHz, as this region is widely accepted in analyzing various liquid samples. The sensor size is 71 &times, 40 &times, 1.6 mm3 with material selection based on an economically available FR4 substrate. The sensor is realized and experimentally validated for its sensitivity by utilizing in-lab prepared aqueous solution samples. Further, liquid concentration is determined by adopting a polarity correlator, which is applied to the sensor&rsquo, s responses obtained at different values.

Fine-grained water quality data can facilitate the optimized management of water resources, which have become increasingly scarce due to population growth, increased demand for safe sources of water, and environmental pollutions. There is a pressing need for cost-effective, reliable, re-usable, and autonomous water sensing technologies that can provide accurate real-time water quality measurements. In this paper, we present a microwave sensor array with sensing elements operating at different frequencies in the wide frequency band of 1 GHz to 10 GHz. The use of array allows for collecting more information compared with a single sensor system. The sensor array can be fabricated in a cost-effective way through standard printed circuit board (PCB) technology. Here, it is tested with water solutions of various contaminants and parameter values. The dielectric properties of the water sample with different contaminants and parameter values are measured and provided as well.

A differential planar microwave resonator permittivity sensor for material characterization is proposed in this paper. The sensor is based on asymmetric terminated cross-shaped resonator (TCSR) to provide multi-band notch frequency characteristics, allowing permittivity measurement of a small dielectric material under test (MUT) with a single resonator. Differential sensing is robust against varying ambient factors that cause frequency variations in the measurements. The dielectric properties of the MUT can be measured from the difference in notch frequencies with the reference material. To illustrate the technique, a tri-band sensor is prototyped using the proposed resonator configuration to measure the permittivity of both solid and liquid samples. The empirical equations for the determination of the MUT permittivity in relation to the notch frequencies have been derived. The sensor operates at 0.97, 1.69, and 2.91 GHz with an average sensitivity of 1.18, 4.45, and 1.22 MHz, respectively. The measured results are in a good agreement with the theoretical analysis.

Electromagnetically induced absorption (EIA) is a quantum phenomenon which occurs when detuned resonant laser fields interfere via atomic transition pathways. The transmission spectrum of a material experiencing EIA consists of an enhanced narrowband absorption line in between the two laser resonances. In this paper, we implement near-field interference of two microstrip radiators to produce a similar absorption mechanism. We propose a practical sensing application to detect foliage moisture by detecting the resonance shifts when sample leaves are made to perturb the near-field radiations. For the sensing, we exploit the anomalous phase signature that accompanies the EIA effect, instead of the amplitude signatures traditionally used in contemporary microwave sensors. The sensing using phase spectrum performs better than the amplitude-based sensing in harsh environments affected by noise and external interferences. Since the proposed EIA-based detector exploits multiple antenna interference in the near field, resonant sensing over distance is also possible. We demonstrate practical moisture detection using actual foliage samples with different moisture levels. We also develop a numerical dielectric model to estimate foliage moisture using full-wave electromagnetic simulations. We anticipate, from this paper, a way to produce low-cost and non-invasive microwave sensors that have reasonable sensitivity and which can be used in remote areas subjected to extreme weather environments.

Microwave sensor technology is widely accepted as a non-destructive and hygienic means for food evaluation and analysis. However, its applications concentrate on in-lab investigations, which are not widely applied for on-line measurement in food industry. Motivated by the rapid progress of microwave technologies and the lack of on-line measurement systems in industry, this paper aims to provide a comprehensive overview of microwave sensors for food measurement, define the technological gap, and suggest the potential solutions. With a brief introduction to the fundamentals, classification and analysis of the traditional methods and technologies are presented, followed by a discussion of calibration and decision-making methods. Based on the analysis of the cutting-edge microwave sensing technologies, the limitations and challenges facing the present studies are identified. Then, focusing on some new emerging technologies including Monolithic Microwave Integrated Circuits (MMIC), antenna array, and System on Chip (SoC) Ultra-Wide Band (UWB) pulse-based time domain systems, the feasibility and prospective of potential solutions in this particular area are suggested. In addition, integration of emerging Information and Communication Technologies (ICT) and new design concepts of the sensor system concerning the practical use for smart manufacturing are also illustrated. The potentiality of the suggested new emerging technologies and integration of ICT to satisfy future digitised industry will be inspirational and of interest to researchers of both microwave engineering and food sectors.

In this paper, reflective-mode phase-variation sensors based on open-ended stepped-impedance transmission lines with optimized sensitivity for their use as defect detectors and dielectric constant sensors are reported. The sensitive part of the sensors consists of either a 90° high-impedance or a 180° low-impedance open-ended sensing line. To optimize the sensitivity, such a sensing line is cascaded to a 90° transmission line section with either low or high characteristic impedance, resulting in a stepped-impedance transmission line configuration. For validation purposes, two different sensors are designed and fabricated. One of the sensors is implemented by means of a 90° high impedance (85 Ω) open-ended sensing line cascaded to a 90° low impedance (15 Ω) transmission line section. The other sensor consists of a 180° 15-Ω open-ended sensing line cascaded to a 90° 85-Ω line. Sensitivity optimization for the measurement of dielectric constants in the vicinity of that corresponding to the Rogers RO4003C substrate (i.e., with dielectric constant 3.55) is carried out. The functionality as a defect detector is demonstrated by measuring the phase-variation in samples consisting of the uncoated Rogers RO4003C substrate (the reference sample) with arrays of holes of different densities.

International audience; This paper presents a sensitive comparator/sensor useful to detect small differences between a reference sample and a sample under test (SUT). The device, a four-port structure, is based on a pair of identical microstrip lines each one loaded with an open split ring resonator (OSRR), the sensitive part of the device. The working principle of the comparator/sensor is mode conversion, caused when the OSRRs are asymmetrically loaded, and the output variable is the cross-mode transmission coefficient. The structure is very sensitive to changes in the complex dielectric constant between the reference sample and the SUT, and it is useful as comparator and sensor in applications such as defect detection, dielectric characterization of solids and liquids, and solute concentration measurements in liquids. The application examples reported in the paper confirm the high sensitivity of the structure to the complex dielectric constant of the SUT, caused by the specific shape of the OSRRs.

Microfluidic devices bring new opportunities in vast applications, in which the temperature control of nanoliter droplets is often required. Due to the inherit size of employed miniature volumes, several challenges exist related to temperature measurements. In this work, we present a non-contact and label-free dielectric-based temperature measurement technique. A capacitive sensor transduces the temperature-dependent dielectric properties into a capacitive value. With a post-processing tuned matching network, the reflection coefficient of the capacitive sensor is minimized at a specific frequency that is directly related to the sample temperature. The system was calibrated with a water-only calibration method using two calibration values. A measurement accuracy of ±0.24°C was achieved with an offset of -0.19°C in a temperature range from 20°C to 55°C. The possibility to use the proposed sensor as a microwave heater at the same time, can lead to a dual-purpose device that minimizes the footprint of the chip and thus its cost, while also reducing the amount of electrical connections to the chip.

WOS: 000502747400002, In this study, a high sensitive metamaterial sensor has been designed to detect quality of water for water treatment centre. The water samples have been obtained and electrical properties have been measured in microwave range to design the proposed sensor. These electrical properties have been assigned in microwave simulator. Water quality has been investigated by using parametric study and genetic algorithm approach to realize high sensitivity in terms of resonance frequency shift. Around 130 MHz frequency shift has been observed between the water samples. This shift is sufficient to detect instantaneously to the quality of water. This is the first study that metamaterial approach has been used to detect water quality in literature., Scientific and Technological Research Council of TurkeyTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [117M855], The authors received financial support from the Scientific and Technological Research Council of Turkey (117M855).

Microwave far-field imaging techniques are well suited to image source, scatterers, and anomalies in dielectric or composite materials. However, the diffraction limits restrict the resolution of far-field imaging. This contribution focuses on the feasibility of designing a metamaterial lens based sensor for enhancing the resolution of microwave far-field imaging. Metamaterials have been increasingly used in the past few decades for the designing of novel microwave circuits and sensor systems. The unique properties of metamterials offer several advantages, such as sub-wavelength nature, compact design, and super-resolution, which is not found in the conventional materials. The feasibility of enhancing imaging resolution using a metamaterial lens along with time reversal processing of far-field microwave data is studied in this paper. Specifically, the super-resolution capability of the lens for detection of sub wavelength defects inside the composite materials is presented.

WOS: 000464099100001, In this study, the labyrinth resonator based chemical liquid and transformer oil condition sensor are presented in a microwave frequency range both numerically and experimentally. The transmission coefficient is observed by the magnetic coupling between the transmission line and resonator which also contain a sensing layer. The sensor structure is tested with the ethanol-water mixtures, methanol-water mixtures and different kind of pure chemical fluidics. In addition, the proposed sensor is used for distinguishing the waste and clean transformer oil sensitively. In the chemical liquids sensing study, linear response characteristics of the sensor have been investigated by the resonance frequency shifts for ethanol-water and methanol-water mixtures. The frequency shifts for each 10% steps of ethanol and methanol content have been monitored as about 25 MHz and 15 MHz, respectively. In the transformer oil condition sensing study, non-destructive methods have been used for providing the long term stability of the sensor structure. In addition, the measured response time between the signal applied from the input port and observation of the transmitted signal from the output port is around 5ns. This value is consistent with the period of the applied signal and the length of the receiver/transmitter cables and the sensor circuit. (c) 2019 The Electrochemical Society., Scientific Project Unit of Cukurova University [FDK-2018-10488], The authors acknowledge the Scientific Project Unit of Cukurova University (FDK-2018-10488)

A chipless radio-frequency identification (chipless-RFID) and sensing system, where tags are read by proximity (near-field) through a switch, is presented. The tags consist of a set of identical resonant elements (split-ring resonators or SRRs), printed or etched at predefined and equidistant positions, forming a linear chain, each SRR providing a bit of information. The logic state (‘1’ or ‘0’) associated with each resonator depends on whether it is present or not in the predefined position. The reader is an array of power splitters used to feed a set of SRR-loaded transmission lines (in equal number to the number of resonant elements, or bits, of the tag). The feeding (interrogation) signal is a harmonic (single-tone) signal tuned to a frequency in the vicinity of the fundamental resonance of the SRRs. The set of SRR-loaded lines must be designed so that the corresponding SRRs are in perfect alignment with the SRRs of the tag, provided the tag is positioned on top of the reader. Thus, in a reading operation, as long as the tag is very close to the reader, the SRRs of the tag modify (decrease) the transmission coefficient of the corresponding reader line (through electromagnetic coupling between both SRRs), and the amplitude of the output signal is severely reduced. Therefore, the identification (ID) code of the tag is contained in the amplitudes of the output signals of the SRR-loaded lines, which can be inferred sequentially by means of a switching system. Unlike previous chipless-RFID systems based on near-field and sequential bit reading, the tags in the proposed system can be merely positioned on top of the reader, conveniently aligned, without the need to mechanically place them across the reader. Since tag reading is only possible if the tag is very close to the reader, this system can be also used as a proximity sensor with applications such as target identification. The proposed chipless-RFID and sensing approach is validated by reading a designed 4-bit tag. For identification purposes, this system is of special interest in applications where a low number of bits suffice, and tag reading by proximity is acceptable (or even convenient). Applications mostly related to secure paper, particularly involving a limited number of items (e.g., exams, ballots, etc.), in order to provide authenticity and avoid counterfeiting, are envisaged. As a proximity sensor, the system may be of use in detecting and distinguishing different targets in applications such as smart packaging.

WOS: 000371012400009, In this study, the frequency selective surface (FSS), absorbance and sensing applications of new unit cells comprised of single, double and quad U-shaped metallic elements are numerically and experimentally investigated. The numerical results are realised by using finite integration technique-based electromagnetic simulation software, CST Microwave Studio. Experimental results are obtained by means of Agilent N5234A PNA-L vector network analyser. The simulated and measured results of U-shaped FSSs are carried out by using two different ways; periodic unit cell and waveguide boundary conditions. The single and quad U-shaped FSS elements show a single band-stop filter property, whereas the double U-shaped FSS shows a dual-frequency band-stop filter behaviour. Absorber and sensor applications of the proposed U-shaped FSSs are illustrated both numerically and experimentally. The three types of U-shaped FSS structures show a narrowband absorbance which has potential in biomedical and sensing applications. Single and dual absorber characteristics are observed with a 90% absorbance. For the sensor configuration, 800 MHz bandwidth is obtained for sensing different materials showing that it is possible to realise different microwave sensor studies in industries of food and agriculture. Simulated and measured results are compared for FSS, absorber and sensor configurations, and the results show a good agreement with each other., Kilis 7 Aralik University [2014/01/MAP/02], This work was financially supported by Kilis 7 Aralik University with the Project number 2014/01/MAP/02.

WOS: 000443021000068, A metamaterial-based permittivity and thickness sensor structure for dielectric substrate material has been proposed at the X band frequency regime. The sensor structure is designed by using a split meander line type resonator and examining it both numerically and experimentally. Various types of dielectric substrate samples have been used to verify the precise sensing characteristics of the proposed sensor. The sensor layer has been chosen as the back side of the sensor structure, and the reflection frequency of the incident signal has been examined The sensor layer thickness has been varied from 0.4 mm to 1.6 mm for the thickness sensing study with two different types of dielectric substrate having the same electromagnetic characteristics. The permittivity sensing study has been carried out by several dielectric materials which have permittivity values between 10.20 and 1.96. The proposed sensor structure can be effectively used in many application areas such as microwave material design, the defense industry and in medical devices., Scientific Project Unit of Cukurova University [FDK-2018-10488], The authors would like to acknowledge the Scientific Project Unit of Cukurova University (FDK-2018-10488).

A $\pmb{0.14-\mu \mathrm{m}}$ CMOS 2-D permittivity imaging matrix prototype operating at microwave frequencies is presented. It comprises 25 permittivity-sensing pixels, each consisting of a sensing patch connected to a dedicated RF bridge. A trans-conduct-ance stage converts the imbalance voltage to a current signal, subsequently down-converted to an intermediate frequency and sampled. The implemented sensor matrix shows precise permittivity measurements over a range of 0.1-10 GHz, and successfully demonstrates permittivity contrast with a resolution of 0.1 – 2.3 from 0.1 to 10 GHz when the matrix is interfaced with various dielectrics. Owing to the matrix implementation a sub-mm, permittivity discontinuity is easily resolved by the presented sensor device.

In this paper is reported the development of microstrip resonators working in the frequency range of 3–6 GHz and their employment in the investigation of the sensing properties of nanostructured materials towards gas. The materials are deposited as films on the gap of the resonators by drop coating aqueous solutions of Ag@α-Fe2O3 nanocomposite having a core–shell structure. Here are reported sensing data about humidity monitoring in the range from 0 to 70%. The increase of humidity value brings to a large frequency shift of the resonance one. The good characteristics of the fabricated device suggest its promising use as humidity sensor.

International audience; This paper is focused on the modeling and analysis of a pair of open complementary split ring resonators (OCSRR) for sensing purposes. Since the capacitance of the OCSRR is very sensitive to dielectric loading, it follows that the OCSRR pair is very useful for differential permittivity measurements. The proposed sensing approach is based on the measurement of the cross-mode S-parameters, particularly the cross-mode insertion loss, very sensitive to asymmetric loading. On the basis of the circuit model of the OCSRR, analytical expressions for the cross-mode insertion loss under small perturbations (asymmetries) are derived. Such expressions, of interest for sensor design, are validated through circuit and electromagnetic simulations.

A planar microstrip ring resonator structure on alumina was developed. It was covered with a zeolite film. The device was successfully operated at around 8.5 GHz at room temperature as a humidity sensor. In the next step, an additional planar heater will be included on the reverse side of the resonator structure to allow for testing of gas sensitive materials under sensor conditions.

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&rsquo, 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.

Non-contact wireless sensing approaches have emerged in recent years, in order to enable novel enhanced developments in the framework of healthcare and biomedical scenarios. One of these technologically advanced solutions is given by software-defined radar platforms, a low-cost radar implementation, where all operations are implemented and easily changed via software. In the present paper, a software-defined radar implementation with Doppler elaboration features is presented, to be applied for the non-contact monitoring of human respiration signals. A quadrature receiver I/Q (In-phase/Quadrature) architecture is adopted in order to overcome the critical issues related to the occurrences of null detection points, while the phase-locked loop components included in the software defined radio transceiver are successfully exploited to guarantee the phase correlation between I/Q signal components. The proposed approach leads to a compact, low-cost, and flexible radar solution, whose application abilities may be simply changed via software, with no need for hardware modifications. Experimental results on a human target are discussed so as to demonstrate the feasibility of the proposed approach for vital signs detection.

This paper will present the project RAPIDMAP. The project is part of CONCERT-Japan, an ERA-NET initiative funded through the FP7 INCO project frame for enhancing research cooperation between European countries and Japan on two topics, one of which is Resilience Against Disasters. The project started in June 2013 and has a duration of 2 years. In the paper, we will outline the aims of the project, methodologies and techniques to be developed and some test data. Remote Sensing (RS) and Geographic Information System (GIS) are powerful technologies for collecting useful information on the damages of disasters in short time. However, since many different types of RS data are available (satellite, aerial, UAV, terrestrial), data co-registration, information integration and feature extraction need reliable and advanced methodologies. In the RAPIDMAP project, we will develop practical ways to integrate RS data processing tools in near-real-time and allow users to use this data soon after the disasters by means of WebGIS tools. This will help not only decision makers but also end-users in the disaster area. The key components of this project are: (1) Near-real-time monitoring: the procedure of near-real-time monitoring with satellites as well as Unmanned Airborne Vehicles (UAV) will be set up and demonstrated. (2) Data co-registration: in disasters, various images as well as maps come from different sources. The co-registration of multiple images is a key technology for information integration. In this project, a system to co-register multiple images in near-real-time will be developed. (3) Data fusion and change detection: one of the advantages of RS is to collect information with multiple sensors. Various methods for fusing optical with active microwave (SAR) sensor data for information extraction and change detection will be developed. (4) Decision Support System (DSS) based on WebGIS technologies: the collected and integrated information has to be easily accessible and visible by decision makers and end-users in near-real-time and worldwide. By using WebGIS technologies, wireless networks and portable terminals, a DSS will allow easy access, retrieval and visualization of all information (fused data, images, maps, etc.) in very short time after data collection and processing. The project will be practically tested and demonstrated at the Tohoku area in Japan and another test site, which were recently affected by large disasters.

WOS: 000416751700010, A metamaterial absorber (MA) based sensor is designed and analysed for various important applications including pressure, temperature, density, and humidity sensing. Material parameters, as well as equivalent circuit model have been extracted and explained. After obtaining a perfect absorption (PA) at around 6.46 GHz and 7.68 GHz, surface current distributions at resonance points have been explained. Since bandwidth and applicability to different sensor applications are important for metamaterial sensor applications, we have realized distinctive sensor demonstrations for pressure, temperature, moisture content and density and the obtained results have been compared with the current literature. The proposed structure uses the changes on the overall system resonance frequency which is caused by the sensor layer's dielectric constant that varies depending on the electromagnetic behaviour of the sample placed in. This model can be adapted to be used in sensor applications including industrial, medical and agricultural products. (C) 2017 Association of Polish Electrical Engineers (SEP). Published by Elsevier B.V. All rights reserved., TUBITAK under the Turkish Academy of Sciences [114E295], O. Akgol, of the author acknowledges the support of TUBITAK under the Projects No. 114E295 partial support of the Turkish Academy of Sciences. The authors would like to thank Olcay Altintas for his help during the preparation of the paper. Additionally, the authors thank the anonymous reviewers for their constructive comments and suggestions to improve the paper.

The potential of a coherent microwave sensor to monitor the vibration characteristics of civil structures has been investigated in the past decade, and successful case studies have been published by different research teams. This remote sensing technique is based on the interferometric processing of real aperture radar acquisitions. Its capability to estimate, simultaneously and remotely, the displacement of different parts of the investigated structures, with high accuracy and repeatability, is its main advantage with respect to conventional sensors. A considerable amount of literature on this technique is available, including various case studies aimed at testing the ambient vibration of bridges, buildings, and towers. In the last years, this technique has been used in Spain for civil structures monitoring. In this paper, three examples of such case studies are described: the monitoring of the suspended bridge crossing the Ebro River at Amposta, the communications tower of Collserola in Barcelona, and an urban building located in Vilafranca del Penedès, a small town close to Barcelona. This paper summarizes the main outcomes of these case studies, underlining the advantages and limitations of the sensors currently available, and concluding with the possible improvements expected from the next generation of sensors.

In this paper, several configurations of splitter/combiner microstrip sections loaded with stepped impedance resonators (SIRs) are analyzed. Such structures are useful as sensors and comparators, and the main aim of the paper is to show that the proposed configurations are useful for the optimization of sensitivity and discrimination. Specifically, for comparison purposes, i.e., to determine anomalies, abnormalities or defects of a sample under test (SUT) in comparison to a reference sample, it is shown that up to three samples can be simultaneously tested. Simple models of the proposed structures are presented, and these models are validated through electromagnetic simulation and experiment. Finally, the principle of operation is validated through a proof-of-concept demonstrator.

This paper introduces the theory of fire detection in moving vehicles by microwave radiometers. The system analysis is discussed and a feasibility study is illustrated on the basis of two implementation hypotheses. The basic idea is to have a fixed radiometer and to look inside the glass windows of the wagon when it passes in front of the instrument antenna. The proposed sensor uses a three-pixel multi-beam configuration that allows an image to be formed by the movement of the train itself. Each pixel is constituted by a direct amplification microwave receiver operating at 31.4 GHz. At this frequency, the antenna can be a 34 cm offset parabolic dish, whereas a 1 K brightness temperature resolution is achievable with an overall system noise figure of 6 dB, an observation bandwidth of 2 GHz and an integration time of 1 ms. The effect of the detector noise is also investigated and several implementation hypotheses are discussed. The presented study is important since it could be applied to the automatic fire alarm in trains and moving vehicles with dielectric wall/windows.

A novel monitoring approach that allows real-time identification of the vegetable oil types is reported. Unlike other available detection methods, which are only lab based, this developed technique exploits a low-power microwave sensing principle and provides for cost-effective, portable, on-the-spot verification of the cooking oil type, which is vital not only for compliance with Food Information Regulation, but for consumer safety, food quality monitoring and customs control.

The current security monitoring system for transformer substation has several disadvantages, such as wiring issues, high cost of installation and maintenance and poor mobility. In order to solve these problems, this article proposes a solution that is intelligent inductive security system based on wireless sensor networks. Among this system the microwave sensors act as inductive terminals and form a multi-hop, self-organizing network through wireless communication. It will integrate data collection, alarm and remote control with characteristics of real-time, safe and reliable quality.

A novel antenna calibration method is presented for near-field problems, such as material characterization or inverse scattering. The procedure accurately accounts for differences between simulations of objects close to antennas and the equivalent experimental measurements. It is based on the method of moments (MoM) solution to surface integral scattering equations. An efficient choice of macrobasis functions (MBFs) is applied to the antenna, which reduces the computational costs by several orders of magnitude. The calibration involves scanning a target of known constitution through the antenna near field, assigning a tuning parameter to each MBF and optimizing said parameters, so as to reduce the error between antenna simulations and measurements. This adjusts the antenna’s simulated surface currents, so as to more accurately represent the currents on the experimental apparatus. Thus, an efficient antenna model is obtained, which more accurately represents the real-world antenna. The calibration technique is verified by applying it to the characterization of dielectric objects of known but arbitrary shape.

This paper focuses on the analysis of splitter/ combiner microstrip sections where each branch is loaded with a complementary split ring resonator (CSRR). The distance between CSRRs is high, and hence, their coupling can be neglected. If the structure exhibits perfect symmetry with regard to the axial plane, a single transmission zero (notch) at the fundamental resonance of the CSRR, arises. Conversely, two notches (i.e., frequency splitting) appear if symmetry is disrupted, and their positions are determined not only by the characteristics of the CSRRs but also by the length of the splitter/combiner sections. A model that includes lumped elements (accounting for the CSRR-loaded line sections) and distributed components (corresponding to the transmission lines) is proposed and used to infer the position of the transmission zeros. Frequency splitting is useful for the implementation of differential sensors and comparators based on symmetry disruption. Using the model, the length of the splitter/combiner sections necessary to optimize the sensitivity of the structures as sensing elements is determined. Parameter extraction and comparison with electromagnetic simulations and measurements in several symmetric and asymmetric structures is used to validate the model. Finally, a prototype device sensor/comparator based on the proposed CSRR-loaded splitter/combiner microstrip sections is presented.

This paper reviews the recent progress in the analysis and applications of the symmetry-related electromagnetic properties of transmission lines loaded with symmetric configurations of resonant elements. It will be shown that the transmission characteristics of these reactively loaded lines can be controlled by the relative orientation between the line and the resonant elements. Two main types of loaded lines are considered: (i) resonance-based structures; and (ii) frequency-splitting structures. In resonance-based transmission lines, a line is loaded with a single resonant (and symmetric) element. For a perfectly symmetric structure, the line is transparent if the line and resonator exhibit symmetry planes of different electromagnetic nature (electric or magnetic wall), whereas the line exhibits a notch (resonance) in the transmission coefficient if the symmetry planes behave as either electric or magnetic walls (symmetric configuration), or if symmetry is broken. In frequency-splitting lines, paired resonators are typically loaded to the transmission line; the structure exhibits a single notch for the symmetric configuration, whereas generally two split notches appear when symmetry is disrupted. Applications of these structures include microwave sensors (e.g., contactless sensors of spatial variables), selective mode suppressors (of application in common-mode suppressed differential lines, for instance) and spectral signature barcodes, among others.

This review paper is focused on the design of microwave sensors using symmetry properties of transmission lines loaded with symmetric resonators. The operating principle of these sensors is presented and then several prototype devices are reported, including linear and angular displacement sensors and rotation speed sensors. The main advantage of the proposed sensors is the robustness against changing environmental conditions.

The paper presents an automatic wireless sensor platform that allows precision soil investigations in order to verify punctual seasonal variations in soil water content. In this way, it is possible to keep the plants nourishment cycle under precise control, correlating it to temperature, humidity and rain variations. The sensing unit is constructed by means of couples of microwave radiators, and the water content percentage is evaluated thanks to a continuous measurement of the received power. The design procedure is carried out by identifying the most suitable solution, in terms of operational frequency, dimensions of radiators and their relative distance, balancing the decreased mismatching effect with the increased propagation attenuation caused by the presence of the water. Experiments carried out in collaboration with the Case Basse winery in Montalcino are presented and discussed.

In June 2013, we started a joint research project MICROPHOTON, 'Measurement and Control of Single-Photon Microwave Radiation on a Chip', as a part of the European Metrology Research Programme (EMRP). The objectives of the project include the development of novel microwave detectors and sources that would ultimately operate at the single-photon level, and the improvement in the performance of cryoelectronic quantum devices by understanding and eliminating the detrimental effects caused by microwave radiation coming from the electromagnetic environment. This paper describes the goals and plans of the project.

International audience; A microwave resonator is presented as a microfabricated sensor dedicated to liquid characterization with perspectives for chemistry and biology. The nanolitter range aqueous solution under investigation is located on top of the planar resonator thanks to a microfluidic channel compatible with a future lab-on-a-chip integration. The interaction between the electric field and the liquid translates into a predictable relationship between electrical characteristics of the resonator (resonant frequency and associated insertion loss) and the complex permittivity of the fluid (real and imaginary parts). A prototype of the resonator has been fabricated and evaluated with de-ionized water/ethanol mixtures, with ethanol volume fraction ranging from 0 to 20 %. Good agreement has been reached between theoretical and measured electrical parameters of the resonator. The discrepancy on the resonant frequency is estimated to 0.5 %, whereas the one on the associated transmission coefficient is lower than 1 %. This translates into a maximum relative error on the real and imaginary part of the predicted relative permittivity of less than 6.5 % and 4 % respectively, validating the principle of this accurate permittivity characterization methodology.

A microwave sensor system has been developed for monitoring adhesive curing processes. The system provides continuous, real-time information about the curing progress without interfering with the reaction. An open-coaxial resonator is used as the sensor head, and measurements of its resonance frequency and quality factor are performed during cure to follow the reaction progress. Additionally, the system provides other interesting parameters such as reaction rate or cure time. The adhesive dielectric properties can also be computed off-line, which gives additional information about the process. The results given by the system correlate very well with conventional measurement techniques such as differential scanning calorimetry, combining accuracy and rate with simplicity and an affordable cost. © 2012 IOP Publishing Ltd., The authors thank Rut Benavente Martinez for her assistance in the DSC experiments. The contract of BG-B is financed by the Ministry of Science and Innovation of Spain, through the 'Torres Quevedo' Sub-programme, which is also co-financed by the European Social Fund (ESF). This work has been financed by the Ministry of Science and Innovation of Spain through the project MONIDIEL (TEC2008-04109).

Material parameter characteristics of a photonic multi-band-gap structure, relying on strip-line technology, is presented. Two layers of dielectric fill the space between two metallic planes and surround a periodic 2D lattice of rectangular metallic patches connected to the ground plane through metallic vias. The variations of the dispersion diagrams with the dielectric constant of one of the layers as parameters are calculated by electromagnetic simulation. Due to the large number of band-gaps the structure presents in the microwave range, it may find applications in multifrequency filter design and enhanced sensibility sensor construction.

A microwave sensor system for the noninvasive monitoring of the curing process of a thermoset material placed inside a metallic mold is described. The microwave sensor is designed as an open-ended coaxial resonator with a curved surface adapted to the mold inner shape. The analysis of the microwave resonator comprises a recently developed method for deembedding the effect of coupling network in overcoupled resonators, so the range of permitted measurements encompass both low and high dielectric losses of polymeric materials. Results show that noninvasive, continuous monitoring of the microwave dielectric properties of the thermoset material can be performed in real time, allowing one to check initial conditions and to verify the evolution of the cure process. © 2006 IEEE., The work of B. Garcia-Banos was supported by a contract from the Ministry of Science and Innovation of Spain, through the "Torres Quevedo" Sub-programme, which is also cofinanced by the European Social Fund (ESF). This work was supported in part by the Comunitat Valenciana Government (IMPIVA - FEDER). The associate editor coordinating the review of this manuscript and approving it for publication was Prof. Evgeny Katz.

A microwave planar resonant sensor, its equivalent circuit, and the driving electronics for the measurement of the complex permittivity in compact areas of the material under test are presented. Compared to transmission or reflection sensors, the adoption of a scalar two-port measurement procedure reduces the cost of the system and improves its robustness. The measuring system requires only the calculation of two parameters, namely, the resonant frequency and the 3 dB bandwidth, thus achieving a substantial reduction of cost and computation time. Such a sensor can be adopted in moisture measurement systems, and its low cost is such as to allow its use even in a disposable manner.