1,721,147 research outputs found
A Simple Nondestructive Radio Frequency Measurement Technique for the Analysis of Liquids
No full textAbstract—Dielectric resonators (DRs) are widely used in microwave and millimeter-wave applications, including antennas and bandpass filters. In this study, we exploit the properties of these resonators in a different way, demonstrating how a common container filled with liquid can be assimilated to a DR. The typical properties of DRs are used to investigate the physical and chemical properties of the content and their evolution, providing a contactless, noninvasive, and nondestructive evaluation (NDE)
of its characteristics. The level of the liquid, its conductivity, and dielectric constant can be easily determined in real time, and used as parameters for in-line monitoring, quality control, and chemical composition assessment. Results are reported using a common wine bottle as a container, but are very easily transferable to other types of liquid containers, including plastic
bottles or larger containers
Automatic analysis of GPR images: A pattern-recognition approach
No full textIn this paper, we propose a novel pattern-recognition system to identify and classify buried objects from ground penetrating radar (GPR) imagery. The entire process is subdivided into four steps. After a preprocessing step, the GPR image is thresholded to put under light the regions containing potential objects. The third step of the system consists of automatically detecting the objects in the obtained binary image by means of a search of linear/hyperbolic patterns formulated within a genetic optimization framework. In the genetic optimizer, each chromosome models the apex position and the curvature associated with the candidate pattern, while the fitness function expresses the Hamming distance between that pattern and the binary image content. Finally, in the fourth step, the problem of the recognition of the material type of the identified objects is approached as a classification issue, which is solved by means of an opportune feature-extraction strategy and a support vector machine classifier. To illustrate the performances of the proposed system, we conducted a thorough experimental study based on GPR images generated by a GPR simulator based on the finite-difference timedomain method so as to construct different acquisition scenarios by varying the number of buried objects, their position, their size, their shape, and their material type. In general, the obtained experimental results show that the proposed system exhibits promising performances both in terms of object detection and material recognition
Gaussian process approach to buried object size estimation in GPR images
No full textRecently, a promising pattern-recognition system has been presented to deal with the extraction of buried-object characteristics in ground-penetrating-radar images. In particular, it allows the detecting of buried objects by means of a search method based on genetic algorithms and the recognizing of the material type of the identified objects through a classification approach based on support vector machines. In this letter, we propose to extend the processing capabilities of this system by addressing the issue of the detected buried-object size estimation. This problem is viewed as a regression issue where it is aimed at reproducing the relationship between a set of opportunely extracted features and the object size. For such purpose, it is formulated within a Gaussian process (GP) regression approach. A detailed experimental study is reported, showing encouraging object-size-estimation accuracies even when buried objects are close to each other
Chipless RFID Sensors for the Internet of Things: Challenges and Opportunities
Full text linkRadio-frequency identification (RFID) sensors are one of the fundamental components of the internet of things that aims at connecting every physical object to the cloud for the exchange of information. In this framework, chipless RFIDs are a breakthrough technology because they remove the cost associated with the chip, being at the same time printable, passive, low-power and suitable for harsh environments. After the important results achieved with multibit chipless tags, there is a clear motivation and interest to extend the chipless sensing functionality to physical, chemical, structural and environmental parameters. These potentialities triggered a strong interest in the scientific and industrial community towards this type of application. Temperature and humidity sensors, as well as localization, proximity, and structural health prototypes, have already been demonstrated, and many other sensing applications are foreseen soon. In this review, both the different architectural approaches available for this technology and the requirements related to the materials employed for sensing are summarized. Then, the state-of-the-art of categories of sensors and their applications are reported and discussed. Finally, an analysis of the current limitations and possible solution strategies for this technology are given, together with an overview of expected future developments
Optimizing the number of printed layers in a PET inkjet-printed chipless RFID sensor
No full textThis paper presents a preliminary optimization study of the performance of conductive resonators inkjet-printed on polyethylene terephthalate (PET) with an increasing number of printed layers in a range 1-20 layers. Samples were tested and the amplitude of the frequency response was demonstrated to follow a power function with the increasing number of layers. Results indicate that with only 2 printed layers the signal intensity approaches 70% of the maximum intensity obtained with the highest number of layers (20), and that with 5 printed layers the signal reaches 83%. This demonstrates that only few deposited layers can be considered a good compromise for the production of Radio-Frequency IDentification (RFID) resonators by inkjet-printing on PET. Finally, the selected sample was tested as a chipless humidity sensor in a configuration with a 150μm-thick Nafion 117 sensitive material
A COMPACT ULTRA-WIDE BAND PRINTED LOG-PERIODIC ANTENNA USING A BOW-TIE STRUCTURE
Full text linkIn this letter, an ultra-wideband compact printed log periodic dipole (LPD) array antenna is designed to operate between 500MHz and 6 GHz frequencies. The proposed LPD antenna structure consists of one bow-tie dipole and 15 regular dipole elements. The bow-tie element is introduced to improve the antenna's performance at the lowest frequencies below 1 GHz and at the same time to reduce the antenna size maintaining a good performance. An experimental antenna prototype has been designed, optimized, fabricated, numerically and experimentally assessed. The obtained results are very promising, and they demonstrated that the presented antenna prototype is able to operate in the range between 500MHz and 6 GHz with an average gain of 6 dBi and a very compact size
A Simple Frequency Domain-Based Chipless Radio Frequency Identifier (RFID) System
No full textThis paper proposes a chip-less RFID tag based on microstrip resonators that works in the microwave frequency bands. The chip-less tag proposed is low-cost, easy to fabricate, and can be read wirelessly at long distances. Two tag prototypes, one with a single and the other with multiple resonators, have been designed, fabricated, and experimentally assessed. In particular, microstrip square resonators slotted in the center and loaded with capacitive structures have been considered. Moreover, to improve the sensibility and the operative range and to avoid alignment problems, the tags have been mounted on the focus of a linear 2D parabolic mirror. The obtained results are quite satisfactory in terms of operative range, sensibility, and accuracy. The preliminary experimental assessment shows that the proposed chip-less configuration can be easily adapted to different application scenarios to improve the passive signal and wireless reading capability
A Preliminary Microwave Frequency Characterization of a Nafion-Based Chipless Sensor for Humidity Monitoring
No full textA low-profile humidity sensor based on a frequency-domain chipless sensing technology is proposed in this study. The chipless microwave sensor is composed by a microstrip resonator gap-coupled with a 50Ω microstrip transmission line and loaded with a Nafion 117 sensitive material layer. The response of the sensor at fixed temperature (25°C) and for a relative humidity (RH) variation in the range 0% - 90% has been simulated and tested in experimental conditions. The preliminary results are promising and pave the way for a future in-depth characterization of the sensor and an analysis of the performance under real-world conditions
Detection of buried objects by an electromagnetic method based on a differential evolution approach
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