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The most important variables to consider in the design of antennas for RFED applications and effective communications are low cost, low profile, and reduced size. The dipole antenna, often known as a dipole aerial, is the most basic and widely used type of antenna. Among other antennas, this is one of the most straightforward antenna layouts. It may be achieved by applying a sinusoidal voltage differential between two thin metallic rods. The dipole antenna is a particularly important type of RF antenna that is frequently used for radio transmission and reception. For many types of antennas, this antenna can be employed as a radiating or driving element. This Dipole antenna may be used in the radio frequency spectrum sections HF, VHF and UHF. The major advantage of a dipole antenna is that it can serve as both a broadcast transmitter and receiver. So, to obtain the most crucial factors, we'll design an antenna in COMSOL Multi Physics and display the results as Radiation patterns.

High packet losses when uplinking commands to small satellites have been reported in the UHF amateur band (430-440 MHz) since late 2013. Measurements of the uplink radio environment have shown high levels of in-band interference in previous works, but public measurement results are limited. Average interference levels are usually measured over some time to build heat maps. In this paper, the analysis is focused on sustained interference over a 24 ms time window using a maximum-minimum method. New heat maps and interference power distributions over Europe, Africa, the Middle East and the Americas were obtained using this method on measurements from the SERPENS satellite . One of the missions of SERPENS was to test an in orbit store-and-forward communication system to exchange short messages with ground sensors for disaster monitoring. The satellite operators had difficulties commanding the satellite due to interference, causing bit errors in uplink packets. Interference power of up to -70 dBm was detected during in-orbit measurements over Europe and North America, while expected received power from the ground stations was not more than -80 dBm. High power space-object tracking radars on the ground operating in the 420-450 MHz band could be the cause, but further measurements are required to verify this. Characterizing this interference can help develop mitigation techniques for future satellite communication systems.

Ultra-high frequency (UHF) radio frequency identification (RFID) tags with an antenna made of a highly flexible graphene assembly film (GAF) is presented. The superb electrical conductivity (∼1.6 × 106 S m−1) of the GAF results in the tag to reach reading range of ∼12 m, which is comparable to that of the commercially available metallic counterparts. The performance of the GAF-based RFID tags under mechanical bending and stretching is experimentally evaluated, which demonstrates excellent mechanical stability of the GAF tag than that of metallic tags. Additionally, substrate stability tests are also conducted. The GAF-based UHF RFID tags can thus lead to numerous applications in information exchange, tracking and tracing as well as the Internet of Things (IoT).

Regulatory approval of ultrahigh field (UHF) MR imaging scanners for clinical use has opened new opportunities for musculoskeletal imaging applications. UHF MR imaging has unique advantages in terms of signal-to-noise ratio, contrast-to-noise ratio, spectral resolution, and multinuclear applications, thus providing unique information not available at lower field strengths. But UHF also comes with a set of technical challenges that are yet to be resolved and may not be suitable for all imaging applications. This review focuses on the latest research in musculoskeletal MR imaging applications at UHF including morphologic imaging, T2, T2∗, and T1ρ mapping, chemical exchange saturation transfer, sodium imaging, and phosphorus spectroscopy imaging applications.

Especially after the launch of 7 T, the ultrahigh magnetic field (UHF) imaging community achieved critically important strides in our understanding of the physics of radiofrequency interactions in the human body, which in turn has led to solutions for the challenges posed by such UHFs. As a result, the originally obtained poor image quality has progressed to the high-quality and high-resolution images obtained at 7 T and now at 10.5 T in the human torso. Despite these tremendous advances, work still remains to further improve the image quality and fully capitalize on the potential advantages UHF has to offer.

This article presents a compact low frequency dual band Liquid crystal polymer (LCP) antenna for Very High Frequency (VHF) and Ultra High Frequency (UHF) band applications. The proposed antenna is having dimensions of 19 × 19 × 0.1 mm3, which is compact in size and designed on FR4, Rogers/ RT Duroid, Polyimide and LCP substrate materials with CPW (Coplanar Waveguide) feed having CSRR (Complementary Split Ring Resonator) structure placed on ground plane. Simulation results of the designed antennas are compared with each other and finally LCP substrate material exhibits better properties compared with all other substrate materials. The designed antenna on LCP operates in frequency ranges of VHF and UHF (0.085–0.29 GHz and 0.805–2.58 GHz) respectively. The designed antenna on LCP is resonating at 0.14 GHz and 1.425 GHz frequencies with reflection coefficient of −24.29 dB and –33.39 dB respectively. The designed antenna on LCP has the gain of 12. 82 dB at 0.14 GHz and 6.27 dB at 1.425 GHz respectively. The designed antenna on LCP is fabricated and analyzed by using combinational analyzer. Measured results of proposed antenna on LCP are in good agreement with simulated results.

This paper presents a novel 3D-printable polymer-based liquid antenna for radio frequency identification (RFID) in the ultrahigh-frequency (UHF) band. Fused deposition modelling, the most widespread and inexpensive 3D printing technique, is used for printing a substrate including polypropylene (PP) and acrylonitrile butadiene styrene (ABS). An ALN-9762-WRW type RFID tag containing a meander metal antenna is modified and printed with microfluidic channels in the substrate. As an ionic liquid, a saltwater dilution is injected into the microfluidic channels designed via a computer-aided design program. A fabricated hybrid liquid antenna is tested using a 200mW UHF RFID reader with the ISO 18000-6C EPC Gen2 protocol. The sensitivity to liquid antenna radiation is measured at distances of 20–900 mm by varying saltwater dilution’s salinity and conductivity between 0 and 12000 ppm and 0-20000μS, respectively. Besides saltwater, an essential oil, peppermint oil (C62H108O7), is also used for liquid antenna. The absorption, refraction, reflection, and scattering characteristics of the polymer substratum are explored in the estimation method. The essential oil produces a buffer area in the 3D layers, which can change the polarization of the antenna. The designed and fabricated 3D-printed hybrid liquid antenna can be utilized in embedded systems suitable for chemical or biological sensing within perpetual systems such as blood or oil circuits.

Partial discharge (PD) is not only the main cause of insulation fault for power equipment, but also an important sign of insulation defects. Using the PD detection system based on ultra-high frequency (UHF) antenna array, the PD localization can be realized in air-insulation substation. At present, the methods commonly used in PD detection system localization include time difference of arrival (TDOA) method and spatial spectrum estimation (SSE) method. This paper introduced the principles of these two methods, and proposed a simulation system for PD direction finding. Using this system, the direction finding performance of the TDOA method and the SSE method under different signal-to-noise ratio, incident azimuth angle, rising edge time and array element spacing are compared. The conclusion shows that when the SNR is less than 0 dB or the element spacing is less than 0.23 m, the SSE system has better direction finding performance. When the element spacing is greater than 0.23 m, the SSE system will be fuzzy in direction finding. At this time, the TDOA algorithm can achieve higher direction finding accuracy.

Purpose To investigate velocity encoded and velocity compensated variants of multi-spoke RF pulses that can be used for flip-angle homogenization at ultra-high fields (UHF). Attention is paid to the velocity encoding for each individual spoke pulse and to displacement artifacts that arise in Fourier transform imaging in the presence of flow. Theory and methods A gradient waveform design for multi-spoke excitation providing an algorithm for minimal TE was proposed that allows two different encodings. Such schemes were compared to an encoding approach that applies an established scheme to multi-spoke excitations. The impact on image quality and quantitative velocity maps was evaluated in phantoms using single- and two-spoke excitations. Additional validation measurements were obtained in-vivo at 7 T. Results Phantom experiments showed that keeping the first gradient moment constant for all k-space lines eliminates any displacements in phase-encoding and slice-selection direction for all spoke pulses but leads to artifacts for non-zero velocity components along readout direction. Introducing variable but well-defined first gradient moments in the phase-encoding direction creates displacements along the velocity vector and thus minimizes velocity-induced geometrical distortions. Phase-resolved mean volume flow in the ascending and descending aorta obtained from two-spoke excitation showed excellent agreement with single-spoke excitation over the cardiac cycle (mean difference 0.8 ± 16.2 ml/s). Conclusions The use of single- and multi-spoke RF pulses for flow quantification at 7 T with controlled displacement artifacts has been successfully demonstrated. The presented techniques form the basis for correct velocity quantification and compensation not only for conventional but also for multi-spoke RF pulses allowing in-plane B1+ homogenization using parallel transmission at UHF.

In this paper, we present an RFID based human and Unmanned Aerial Vehicle (UAV) Interaction system, termed RFHUI, to provide an intuitive and easy-to-operate method to navigate a UAV in an indoor environment. It relies on the passive Radio-Frequency IDentification (RFID) technology to precisely track the pose of a handheld controller, and then transfer the pose information to navigate the UAV. A prototype of the handheld controller is created by attaching three or more Ultra High Frequency (UHF) RFID tags to a board. A Commercial Off-The-Shelf (COTS) RFID reader with multiple antennas is deployed to collect the observations of the tags. First, the precise positions of all the tags can be obtained by our proposed method, which leverages a Bayesian filter and Channel State Information (CSI) phase measurements collected from the RFID reader. Second, we introduce a Singular Value Decomposition (SVD) based approach to obtain a 6-DoF (Degrees of Freedom) pose of the controller from estimated positions of the tags. Furthermore, the pose of the controller can be precisely tracked in a real-time manner, while the user moves the controller. Finally, control commands will be generated from the controller's pose and sent to the UAV for navigation. The performance of the RFHUI is evaluated by several experiments. The results show that it provides precise poses with 0.045 m mean error in position and 2.5∘ mean error in orientation for the controller, and enables the controller to precisely and intuitively navigate the UAV in an indoor environment. Keywords: Radio-Frequency Identification (RFID), Human Computer Interaction (HCI), Unmanned Aerial Vehicle (UAV), Singular Value Decomposition (SVD), Localization, Navigation

Detection of partial discharges (PD) is of great importance in the monitoring of high voltage devices and their early fault diagnosis. The ultrasonic sensing is one of the PD detection methods proposed in the literature. Normally, the partial discharge signals are mapped onto the voltage waveform to generate the phase resolved partial discharge or PRPD patterns for the fault type recognition. However, the travel time of ultrasonic signals hinders using a similar process in the ultrasonic PD method. In order to avoid this problem and to improve the ultrasonic PD detection by generating corresponding PRPD, this paper presents a novel method that utilizes ultra-high frequency (UHF) and ultrasonic signals of PD, simultaneously. To show the performance of this method, a circuit is built for ultrasonic PD detection first. In the next step, a wideband antenna is utilized, and its signals are compared with the ultrasonic sensor output to compensate for the PD travel time error. Finally, the PRPD patterns are generated and analyzed for five different configurations. The electrical PRPDs are measured for these cases and compared with the acoustic ones. The experimental results demonstrated in this paper prove the potential of the proposed idea to generate acoustic PRPD for the purpose of PD type recognition.

Today, the world is technology-driven and so of these technologies are driven using wireless systems. Signal coverage and quality of service are pertinent for network providers and path loss prediction is very important in the design and planning of these systems. However, the inefficiency of conventional propagation models, such as empirical, deterministic and theoretical models has been established in previous research works. The machine learning methods have recently been applied for prediction of path losses. The Adaptive Neuro-Fuzzy Inference System (ANFIS) technique is one of the machine learning techniques that has been successfully employed to predict path losses in different environments. However, the performance of the ANFIS-based models in terms of the computational complexity and accuracy depends on the selection of the appropriate system parameters. This paper, therefore, investigates the effect of number and shape of membership function (MF), and training data size on the performance of ANFIS model for predicting path losses in the VHF and UHF bands in built-up environments. Path loss propagation measurements were conducted in four cities of Nigeria over the cellular and broadcasting frequencies. A total of 17 broadcast transmission and cellular base stations were utilized for this study. From the results obtained, it can be concluded for the broadcasting bands that the generalized bell MF shows better performance with an average RMSE of 3.00 dB across all the routes, followed by gaussian, Pi, trapezoid and triangular MFs in that other with average RMSE values of 3.09 dB, 3.11 dB, 3.16 dB and 3.23 dB respectively. For the cellular systems, Triangular MF outperformed other MFs with the lowest average RMSE. The generalized bell MF was found to be suited for WCDMA band while triangular MF is most suited for GSM band. Furthermore, it can also be concluded that the higher the number of membership functions, the lower the RMSE, whereas, a decrease in the data size leads to a reduction in the RMSE values. The findings of this study would help researchers and network planners to make a more informed decision on choosing appropriate system parameters when modelling ANFIS models for path loss prediction.

Several works have been carried out in recent years aiming at improving the performance of RFID systems. Some proposals focus their attention on the communication protocol between the reader and passive tags, trying to avoid collisions or the capture effect during the identification process. Most of these works have a common factor: the required use of a pseudorandom number generator that has a great impact in the performance of the identification process. This paper analyzes the quality of the pseudorandom number generator in commercial passive UHF-RFID tags, to assess whether its outputs can be distinguished from truly random data. It then goes on to present a new mechanism that simplifies the generation of these numbers. A set of tests has been used to assess the randomness of the measured pseudorandom number sequences from commercial tags as well as the pseudorandom numbers obtained with the proposed method. This new method has then been implemented in a physical platform that emulates a real tag and its adequacy checked with commercial readers. The results thus obtained indicate that the proposed method generates valid pseudorandom number sequences while reducing the complexity and power consumption required for the tag.

The design, simulation, assembly and testing of a novel dedicated antisymmetric transmit/receive (Tx/Rx) coil array to demonstrate the feasibility of cardiac magnetic resonance imaging (cMRI) in pigs at 7 T was described. The novel antisymmetric array is composed of eight elements based on mirrored and reversed loop orientations to generate varying B 1 + field harmonics for RF shimming. The central four loop elements formed together a pair of antisymmetric L-shaped channels to allow good decoupling between all neighboring elements of the entire array. The antisymmetric array was compared to a standard symmetric rectilinear loop array with an identical housing dimension. Both arrays were driven in the parallel transmit (pTx) mode forming an 8-channel transmit and 16-channel receive (8Tx/16Rx) coil array, where the same posterior array was combined with both anterior arrays. The hardware and imaging performance of the dedicated cardiac arrays were validated and compared by means of electromagnetic (EM) simulations, bench-top measurements, phantom, and ex-vivo MRI experiments with 46 kg female pig. Combined signal-to-noise ratio (SNR), geometry factor (g-factor), noise correlation maps, and high resolution ex-vivo cardiac images were acquired with an in-plane resolution of 0.3 mm × 0.3 mm using both arrays. The novel antisymmetric array enhanced the SNR within the heart by about two times and demonstrated good decoupling and improved control of the B 1 + field distributions for RF shimming compared to the standard coil array. Parallel imaging with acceleration factor (R) up to 4 was possible using the novel antisymmetric coil array while maintaining the mean g-factor within the heart region of 1.13.

A novel and broadband non-directional coupler operating at 300–3200 MHz band is presented in this paper. The coupler was designed using extensive electromagnetic simulations and built on FR4 substrate using microstrip technology. The designed coupler is a three-port device; input, output, and coupled ports. It provides an almost flat coupled power at the coupled port throughout the UHF band. Measurements are provided in comparison with simulated S-parameters. Measured and simulated values are in very good agreement.

Surface acoustic wave (SAW) device, which integrates the generation, propagation and detection of acoustic waves into the same device, has been known to be an essential functional unit for sensors and electromechanical systems. However, high substrate cost and process complexity of traditional inorganic SAW devices have triggered extensive research efforts to seek for alternative low cost solution, especially for disposable application. Poly(vinylidenefluoride)[P(VDF)] and its co-polymer, despite being promising materials for acoustic transducer with inexpensive processing technique, have rarely been used in SAW device due to exhibiting extremely low operating frequency (few tens of MHz) compared to the traditional SAW device (few hundreds of MHz to GHz) based on inorganic piezoelectric material. Here we demonstrate SAW device, which is entirely based on Poly(vinylidenefluoride-trifluoroethylene) [P(VDF-TrFE)], as piezoelectric material, offering transduction and propagation of acoustic waves with a frequency around 450 MHz. The drawbacks of the previous attempts by the others are addressed and rectified systematically to obtain high operating frequency comparable to the traditional SAW. The influence of periodicity of interdigitated transducer and thickness of polymer film on device performance is thoroughly investigated. Temperature dependent variation of resonance frequency, which can be exploited as temperature sensor in integrated systems, is also demonstrated.

The present work is devoted to the miniaturization of a conventional three branch line coupler device in UHF band. The procedure for designing miniature structures based on replacing the microstrip transmission line segment with equivalent structures with the same phase shift is described. These structures are placed in free space inside the coupler. The proposed coupler operates at 1 GHz (UHF band), with good specifications. The area of the manufactured prototype of the three-branch line coupler with open-circuit conditions stubs is 909 mm2, which is 76% less than the size of the conventional device and relative bandwidth is 23.7%. The area of the manufactured prototype of the three-branch line coupler with high-resistance lines with a high-resistance segment in the form of U symbol is 1169.7 mm2, which is 69.1% less than the size of the conventional device and relative bandwidth is 34.1%.

We present simultaneous optical and radar observations of meteors observed over the Arecibo radar in Puerto Rico. These observations were obtained during ∼ 24 h of radar time over 3 different nights in May 2012. The radar was operating in a dual-frequency mode at 430 MHz (UHF) and 46.8 MHz (VHF). The optical observations were made at 41 frames per second with an Andor Electron Multiplying CCD camera with a field of view of ∼ 6°, enabling the determination of accurate horizontal meteor velocities and optical light curves. There are varying detection sensitivities of the 3 different techniques (2 radar, 1 optical). The UHF radar is the most sensitive, resulting in a total of 8710 detected meteors during that period, while the VHF radar is significantly less sensitive—resulting in only 278 detected meteors. The optical observations are the least sensitive, resulting in a total of 178 detections. Of all of these meteors, only 19 were simultaneously detected by the 3 instruments. This paper focuses on the analysis of these 19 common events. The meteoroid masses determined from the optical light curves were found to be in the range of 20 μg to 1.2 mg and did not correlate with the maximum Signal-to-Noise Ratio (SNR) of either radar. In addition, the UHF radar detected 5 out of these 19 meteors with far side-lobes, beyond the main-beam and first side-lobe. This indicates that a significant fraction of events detected by the UHF radar could be in far side lobes and therefore have significantly underestimated Radar Cross Sections (RCS), given the smaller backscattered powers received in the side lobes.

In the paper a drop-on-demand deposition system using ultra-high frequency induction heating technology is proposed for the aim of depositing metal materials with high melting point onto the substrate at a low thermal input. The numerical model coupled with electromagnetic field, thermal field and flow field was established to investigate the metal transfer and thermal characteristics of the deposition process. Results indicate that the metal droplet can be deposited onto the substrate at a low thermal input. The effects of current frequency and current density on the deposition temperature and time duration of the deposition were also numerically studied. Analysis of the electromagnetic force and temperature of the pendent molten metal during deposition demonstrates that the current frequency as well as current density influences the time duration by determining the electromagnetic force and the heating rate. The numerical model was verified by experiments, and the experimental results show good agreement with the calculated results. With the advantage of depositing high melting point material while limiting the thermal input for the substrate, the drop-on-demand deposition method using ultra-high frequency induction heating technology is expected to be applied in metal droplet-based applications where the thermal-sensitive materials are used.

A compact meandered cross-shaped slot circularly polarized antenna for ultra high frequency (UHF) band radio frequency identification (RFID) reader applications is presented. Circularly polarized radiation is realized by introducing a slot on the diagonal axis of a square patch. Four different slot shapes are entrenched on one of the diagonal axes of the square patch for circularly polarized radiation and compared to the fixed overall volume of the antenna. The overall size of the antenna is reduced by increasing the perimeter of a slot within one quadrant of the patch. The meandered cross-shaped slot circularly polarized antenna is compact when compared with circular-, square- and cross-shaped slot circularly polarized antennas. Diagonally symmetric two- and four-meandered cross-shaped slot antennas are studied for further size miniaturization. Measured 3 dB axial ratio bandwidth of around 6 MHz with more than 2 dBic boresight gain and 10-dB reflection coefficient of 22 MHz is obtained with circularly polarized meandered cross-shaped four slot antenna. Size of the antenna is 0.189 λ0 × 0.189 λ0, where λ0 is the operating wavelength at 915 MHz.

In this experimental study, localized electrodeposition of nickel pillars was performed to study the effect of pulse frequency, applied voltage, pulsed duty cycle, and the interelectrode gap, on the diameter of the deposit and the rate of deposition height. The effects of ultra-high frequency during the localized electrodeposition process, which have not been studied for micro electrochemical additive manufacturing purposes, are documented and further quantification of the effects of localization was conducted. It was found that the rate of deposition height increased with an increase in the pulse frequency, applied voltage, and duty cycle. As for deposition diameters, which is a measure of the localization, inter electrode gap was found to have no significant effect, while with pulse voltage and frequency, the average deposition diameter for certain parameters was substantially smaller than the tool electrode diameter, by approximate ratios of 2/3 and 1/5 respectively. These findings imply that modifying the electrical process parameters can allow for highly localized electrochemical deposition which is an important requirement for electrochemical additive manufacturing.

In order to quantitatively calibrate the characteristics of the UHF partial discharge(PD) detection technology in oil-immersed transformer, we built the common PD defects and completed the correlation experiment research in artificial imitating transformer. Meanwhile we extracted the apparent discharge magnitude and accumulated energy of PD signals as a calibration characteristic when the four defects in oil under different discharge voltage, and conducted a comparative analysis on their relationship. It is concluded that the accumulated signal energy has a linear relationship with the square of signal discharge, moreover, the goodness of fit of calibration regression curve can be influenced by the type of oil paper insulation defect and the amplitude of experiment voltage, and so the specific types and conditions of PD must be considered in UHF signal calibration. The results enrich the database of UHF detection in transformer oil and provide the favorable reference for a further study of calibrating UHF signal’s discharge quantity in oil.

During the movement of various types of transport (auto, rail) in forest, radio communications in the VHF / UHF bands are sharply disturbed, which is associated with attenuation and a change in the polarization plane (cross polarization effect) of radio waves in the forest. Therefore, this paper reviews the problem of the appearance of the cross-polarization effect appearance in the through propagation of VHF/UHF radio waves in forests. The parameters of cross-polarization are analyzed and the functional dependences XPD {f, ζF, rF}, XPR {f, ζF, rF} are evaluated on the operating frequency, forest vegetation properties and the distance traveled within the forest from the transmitting antenna to the receiving antenna. Rerouted by forward and backward vegetation elements, radio signals contain many cross-polarization components that can have levels comparable to the main (useful) component. An increase in cross-polarization components can be observed in the "forward" region, which can be formed by successively decreasing the useful component, ultimately causing a significant decrease in the XPD value. As a result, the relatively high cross-polarization component can consecutively reduce the level of the useful component, while the cross-polarization effect is random, and the XPD value with fluctuating distance between the transmitting and receiving stations begins to fluctuate relative to XPD = 0. Thus, the influence of forest vegetation on the propagation conditions in VHF/UHF ranges is not only manifested in a random variation of the attenuation coefficient, but also leads to a cross-polarization effect, which ultimately causes deep fading of the radio signal at the receiving point. This work can be used in assessing the fluctuations of received signals due to the occurrence of cross-polarization during transport traffic in the forest.

Oil-immersed Power transformers are considered to be one of the most essential parts of the electrical system and partial discharges (PD) are one of the dangerous problems that face transformer insulation. PD is localized dielectric breakdown of an insulation degradation or defect in an oil power transformer. Ultra-high frequency (UHF) detection technique can be utilized in PD detection inside oil-filled power transformers, by capturing the electromagnetic waves generated by PD using an antenna. This research presents a design for a compact double layer printed UHF antenna to detect and discriminate various types of PD activity in a power transformer. PD activity in the transformer has been proposed in this paper by using four different artificial insulation defects, metal protrusion defect in air medium, metal protrusion defect in an oil medium, surface discharge defect, and oil-paper void defect. The presented design guarantees a small-size wideband antenna for detection. The designed antenna has small/simple size and ultra-wide frequency passband from 1.4 to 1.85 GHz, 2.2 to 2.65 GHz, and 3.2 to 3.4 GHz. The normalized power frequency spectra of the captured UHF-PD signals of the four defective models showed that every PD type has its signature, and this could help in the discrimination among different types on site.

Today, the continuous growth of electronic commerce volume increases the importance of point-to-point shipment transportation. For this reason, it is extremely important that shipment management systems provide effective, efficient and fast service. A study of the literature shows that the improvements made in the field of transportation have been generally aimed at global logistics networks. In this study, unlike the existing literature, a blockchain-based solution is developed for local cargo networks. With this approach using Ultra High Radio Frequency (UHF-RFID), Internet of Things (IoT) sensors and blockchain-based smart contracts, a fast shipping management architecture that ensures security between the parties is provided. In this context, an automatic payment and approval mechanism is established between the parties using ethereum-based smart contracts. In addition, shipments equipped with RFID tags are automatically tracked and traceable using UHF-RFID antennas. The IoT data collected in the study are stored on a cloud-based server, which is a cost-effective solution. Smart contracts that enable communication between the parties are written in the Solidity language using the Ganache, Truffle and Metamask platforms. It was observed that the integration between the technologies is ensured and the communication between the parties works successfully in the test processes.

Bi-directional Brain–Computer Interfacing (BBCI) faces major challenges due to, in part, the difficulty of transmission of Electro-corticographical (ECoG) signals from the brain to external devices. For human subjects, safety and convenience would be greatly increased if we could replace the wired interface between the electrodes and the extra-cutaneous receiver with a wireless interface. All the technology that we have today using wires to connect the transmitter which setting on top of the electrodes with a reader located on the scalp which can create brain infection due to scar tissue and that might lead to serious brain injury. We have eliminated this risk by using passive transmitter setting on the electrode and transmit wirelessly to a reader sitting on the scalp using a back-scatter technique which shows a great potential in BCI Applications. This paper investigates the feasibility of passive Ultra High Frequency Radio Frequency Identification (UHF–RFID) for wireless communication between multiple transmitters inside the brain that collect vital data continuously and transmit them to an external controller located on the scalp outside the brain in order to design wireless communication channel inside the human brain considering network lifetime and minimize power consumption. Also, we emphasize the effect of increasing number of transmitters to maximize the throughput. Extensive literature survey shows that there is exists no model has been made for invasive BBCI applications based on UHF passive RFID. Results are presented with calculated Received Signal Strength (RSSI), Signal to Noise Ratio (SNR), Channel Capacity, Maximum number of the electrode, and Path Loss. These analyses are essential for building a brain–computer interface application. We showcase theoretical and experimental results based on a phantom model of the human brain using passive RFID as the implantable transmitter operating in UHF range. Based on these values we have concluded that UHF–RFID is a viable technology with multiple transmitters to a depth of 4 cm.

We develop a new procedure to estimate the indoor distance for passive UHF RFID tag, the estimation concept relies on the relationship between radar cross section RCS of the maximum effective reading distance and any measured distance at 928 MHz multiplied by received signal strength indicator RSSI ratio. It gives a high accuracy in two stages. In the first stage, the percentage accuracy of the estimated distance is trained, and a percentage polynomial curve is created; this curve is used to increase the accuracy in the second stage which ranges from 90.3% to 100.0% with root mean square error RMSE 0.02.

An original partial discharge generated in oil insulation identification methodology based on simultaneously conducted measurements using electrical method, ultra high frequency method and acoustic emission method is presented in the paper. Three different partial discharge model sources as well as measuring instruments commonly applied for partial discharge detection in electrical power transformers are yielded within a laboratory research. Total of 45 scenarios, including proposed spark gap configurations, selected supply voltage levels and UHF frequencies are analyzed during measurements series. Furthermore, form among total of 93 descriptors assigned for every applied partial discharge model source configuration there are 24 proposed as potentially useful for partial discharge identification applications with their 95% confidence bounds. Attempt of discriminative descriptors selection for partial discharge source analysis in on-site transformer applications as well as a proposal of unique descriptors according to every selected spark gap configuration that could be potentially useful for partial discharge identification purposes are the main purpose of the presented paper. The proposed methodology verification on a real life transformer with particular consideration of the selected descriptors potential utility in the fields of partial discharge detection and identification in electrical power industry applications confirmed a proposed methodology usefulness.

A High-temperature superconducting (HTS) bandpass filter system containing a lowpass filter, a highpass filter and an LNA has been fabricated to meet the demands of wideband wireless signal receiving system. The filter system has an ultimate fractional bandwidth over 108% with the passband from 820 MHz to 2750 MHz. Besides, the filter system showed good frequency selectivity and out-of-band rejection. The 40 dB to 3 dB rectangle coefficient of our filter system is 1.4, which is better than that of an 8-pole Chebyshev filter, and the out-of-band rejection is better than 40 dB. Through systematical optimization, a return loss of better than 9.8 dB was received in the filter system. This system also showed advantages in design and fabrication precision.

A vehicle to infrastructure (V2I) electromagnetic system is studied to estimate the lateral position of a vehicle in its lane. This system can be include in an advanced driving assistance system (ADAS) in order to provide the vehicle lateral positions to warn the driver in case of an involuntary road lane departure or to drive the car in case of autonomous driving. The developed system consists of passive electromagnetic transponders embedded in the lane markings, each one contains two surface acoustic wave (SAW) resonators that have two different center frequencies, and a hyperfrequency transceiver embedded in the lateral sides of the vehicle. The system operates in the ultrahigh frequency (UHF) band. The phase difference of arrival (PDoA) method for distance measurement is used to estimate the absolute lateral distance between the vehicle and the lane markings. A method is developed to recover the useful phases from the global response of the system using its frequency response, around the two resonance frequencies of the SAW resonators. The system is tested in outdoor environment and the results of the useful phases recovering method are accurate, where the absolute distance estimation gives an error lower than 3 cm.

A circularly polarized, broad bandwidth, square-ring patch antenna for radio-frequency identification (RFID) is proposed. The antenna has a dimension of 100 × 100 × 22.9 mm3. By using a Wilkinson power divider and a patch-antenna structure, a measured 3-dB axial-ratio bandwidth of approximately 140 MHz (16.47%), an impedance bandwidth of 136 MHz (15.81%), and a measured peak gain of approximately 6.8 dBic are being achieved. The operating band of the proposed antenna is suitable for China (840–846 MHz), Europe (865–868 MHz) and the United States (902–928 MHz) ultra-high frequency (UHF) RFID applications.

Radio frequency identification (RFID) sensor systems have unique advantages of identification, communication and sensing together. Previous researches on RFID based sensing investigate power based features, and face the challenges of low sensitivity and robustness due to environment RF field. In this paper, rather than using received signal strength indicator (RSSI), we present a method using features of transient responses from in-phase quadrature (IQ) signal to overcome the challenges of sensitivity and robustness in ultra-high frequency (UHF) RFID sensor systems. The transient responses of the IQ signal are analysed using skewness feature for different defects. The experimental results show that IQ based skewness features from IQ signal improve sensitivity and robustness for defect characterisation compared with previous RSSI and RCS methods.

In this article, we introduce an antenna printed on a flexible substrate. This prototype is intended for a flexible display device. The flexible screen has the advantage of being finer and more shock-resistant than the current slabs while allowing smart-phones to adapt to different uses due to its flexibility. The suggested antenna is a dipole with two symmetric frameworks printed on a Kapton polyimide substrate with a relative permittivity of 3.45 and a loss tangent of 0.002. The parametric study performed is based on the length and width of the proposed antenna; it shows that the proposed architecture is adapted to operate in the UHF band. The simulation and measurement results are in good similarity.

Automatic monitoring of animal feeding behaviour in commercial farms is desirable as it is an important indicator for the well-being and health of animals. Low-frequency and high-frequency radio frequency identification (RFID) systems have been tested for the detection of feeding visits of growing-finishing pigs, but the suitability of ultra-high frequency (UHF) RFID for this application has not yet been shown. Therefore, the objective of this study was the validation of a UHF-RFID system, consisting of a reader, antennas and passive transponder ear tags, for the monitoring of visits of growing-finishing pigs at a short trough for liquid feeding. Consequently, (1) two antenna variants (free-form and patch antennas) were tested at different levels of antenna output power, (2) two methods to determine a bout criterion for the creation of trough visits from the RFID registrations were compared, and (3) a comparison of the RFID data with reference data from video observation was carried out. The analysis showed that the reading area exceeded the trough especially in the variants with high output power. Thus, the evaluation of the first and second rate of change of the total daily number and total daily duration of visits led to higher values for the bout criterion (50 s for both antenna variants) than the evaluation of the mean absolute deviation between video and RFID data (20 s for the free-form antenna and 30 s for the patch antennas). The trough visits observed were detected best with the patch antennas at 25 dBm output power and a bout criterion of 30 s with regard to average precision (61.1%), and correlation between the video data and RFID visits (R 2 = 0.87 for total number and 0.80 for total duration of visits). The average sensitivity of this variant was 49.7%, specificity 99.0% and accuracy 97.9%. The highest average sensitivity (79.7%) and a good correlation between video data and RFID visits (R 2 = 0.78 for total number, 0.56 for total duration of visits with a bout criterion of 50 s) were measured with the free-form antenna at 26 dBm. In conclusion, UHF-RFID can be suitable for the monitoring of trough visits of growing-finishing pigs, but the effect of ear tissue on the performance of the UHF-RFID ear tags should be reduced by further development. In addition, further research should be carried out to evaluate the potential of this technology completely for animal behaviour monitoring.

Electrical dehydrators are often used to separate water from oil emulsions. However, the frequency and electric field strength are fixed during separation and cannot change with the flow rate and emulsion properties. To solve this problem, ultra-high frequency and self-adaptive voltage transformer was developed to enhance the separation efficiency and compared with ordinary high frequency transformer. To this end, a small-scale evaluation test system was designed to investigate the influence of electric fields and operating parameters on water dehydration of different emulsions. The results showed there are different optimal electric field strengths for emulsions of various properties. Higher frequency values required lower electric field strengths. Under high frequencies, the formed water chains attracted surrounding small water droplets to form larger droplets. During the separation process, the frequency was kept stable but the electric field strength adaptively changed and gradually decreased, resulting in declined power consumption. Ordinary high-frequency electric fields illustrated low dehydration efficiencies on heavy oil emulsions, high-water concentration emulsions, and water-containing polymer emulsions. By comparison, ultra-high-frequency self-adaptive electric field strengths transformer showed superior separation efficiencies, low energy consumptions, and more stability. Besides, the separated water was cleaner and exhibiting superior adaptability to adverse conditions. In sum, these findings look promising for optimizing the operation of existing electrical dehydrators and promoting the use of ultra-high-frequency and self-adaptive electric fields.

The performance of UHF partial discharge detector is important for the timely detection and diagnosis of insulation faults. However, the performance calibration method of UHF partial discharge detector under laboratory conditions is not yet fully mature. In this paper, on the basis of the related literature, a specific experimental research of the UHF partial discharge detector based on the gigahertz transverse electromagnetic wave (GTEM) cell about the effective height, amplitude linearity, detection sensitivity, dynamic scope was carried out. The validity of this method is verified by comparing the test equipment of three different manufacturers.

Sanitary and stormwater sewers are buried assets that play important roles in the prevention of diseases and the reduction of health risks for our societies. Due to their hidden nature, these assets are not frequently assessed and maintained to optimal conditions. The lack of maintenance can cause sewer blockages and overflows that result in the release of pathogens into the environment. For cities, monitoring sewer conditions on a large-scale can be costly, time-consuming, and labor-intensive if using current low-throughput technologies, such as dye testing or closed-circuit television. Alternatively, smart sensor systems can provide low-cost, high-throughput, and automatic data-driven features for real-time monitoring applications. In this study, we developed ultrahigh-frequency radio-frequency identification (UHF RFID)-based sensors that are flushable and suitable for sanitary and stormwater pipes quick surveys. 3D printed RFID sensors were designed to float at the water-air interface and minimize the water interference to RF signal communications. The optimal detection range was also determined to support the design and installation of the reader in various utility holes. Field trials demonstrated that the UHF RFID system is a low-cost, high-throughput, and robust solution for monitoring blockage, illicit-connection, and water flow in sewer networks.

Functional magnetic resonance imaging (fMRI) has become one of the most powerful tools for investigating the human brain. Ultrahigh magnetic field (UHF) of 7 Tesla has played a critical role in enabling higher resolution and more accurate (relative to the neuronal activity) functional maps. However, even with these gains, the fMRI approach is challenged relative to the spatial scale over which brain function is organized. Therefore, going forward, significant advances in fMRI are still needed. Such advances will predominantly come from magnetic fields significantly higher than 7 Tesla, which is the most commonly used UHF platform today, and additional technologies that will include developments in pulse sequences, image reconstruction, noise suppression, and image analysis in order to further enhance and augment the gains than can be realized by going to higher magnetic fields.

The introduction of dual-band RFIDs (Radio Frequency Identification Devices) in chip cards created new ESD risks with unconventional discharge paths. On a plastic foil, a more or less grounded coil antenna for radio frequency (RF) is aluminium-printed on one half of the card. On the other half, an electrical floating, but thus, highly electrostatic charged folded dipole for ultrahigh frequency (UHF) is arranged. When the chip is placed by a flip-chip assembly process, a strong discharge takes place through the RF-UHF-path of the chip. Usual ESD protective structures are only of limited use in these cases. Discharge paths and specific risks are described in this paper as well as useful countermeasures in foil and assembly processes.

Radio Frequency Identification is becoming more and more popular although unit price of RFID tags is still higher than price of barcodes. Further decrease in cost of using RFID techniques can be possible to achieve by recycling of tags. However, their multiple use causes that RFID tags are placed repeatedly on a surface of identified object and then, peeled off. Thus, tags have to withstand even long-term mechanical exposure in order to guarantee reliable work in a long period of time. In this paper, reliability of UHF tags under long-term mechanical cycling is reported. Two different RFID tags were used to perform investigations which revealed that mechanical properties of tested RFID tags are mostly dependent on their stackup, i.e. additional top and internal foil or paper layers may introduce significant growth of mechanical durability of the tested RFID tag samples.

In this paper, Coplanar Waveguide (CPW) elements are used to load UHF RFID meander-line antennas. Although, the insertion of these elements allow to design small antennas their gain decrease depending on the CPW structures are connected. In this sense, a new location to print CPW elements in the meander-line antenna is proposed aiming not to deteriorate the gain. A multi-objective optimization algorithm is applied in the meander-line antennas loaded with CPW elements in different positions and a comparison between their performances is done. To validate the computational model of the proposed antenna its input impedance is measured.

With a potential application to surface modification of oxide materials in mind, active species in RF and microwave (UHF) N 2 afterglows were analyzed in our newly designed flowing reactors. For both plasma systems, discharge of N 2 was generated in a long quartz tube with a small diameter (dia. 5–6 mm) and then was directly injected into a chamber with a large diameter of 15–20 cm. The discharge condition was set to be similar between the two systems; the gas pressure, flow rate and the applied power were 6 Torr, 0.6 slm and 100 W, respectively. Under this condition, the residence time at the chamber inlet was (1–3) x 10 −3 s. The RF and UHF afterglows were formed in the chamber with luminous jets from the end of the discharge tube. However, we found that the densities of active species were quite source-dependent; N and N 2 (A) densities were higher in UHF than in RF in spite of more O-atoms impurity. The origin of such difference is also attributed to the inherent difference in the nature of excitation between the two plasma sources; RF is more vibrational and is longer than UHF.

During the last few years, reclaiming TV spectrum for mobile broadband use has been a hotly debated topic in the telecommunications policy agenda. This paper evaluates two ways to improve spectrum efficiency to today's noise-limited single-transmitter broadcast television approach. One way is to increase the transmit power of each broadcaster's only transmitter. The other way is to replace that single transmitter with a multi-transmitter low-power low-tower (LPLT) single frequency network (SFN). In order to quantify their potential benefits, two different scenarios are considered. First, this paper presents the results obtained for a large region in which broadcasters are uniformly distributed, so that the number of TV broadcasts that can be received is roughly the same at any location. In this case, results suggest that increasing power of traditional single-transmitter broadcasters could reduce the amount of spectrum needed for TV by up to 30%, and would be cost-effective for population densities above 30 per square km. A switch to SFNs could reduce the amount of spectrum needed for TV by roughly 60%, but at a higher cost. Results suggest that the LPLT SFN approach could be cost-effective for regions with uniformly distributed broadcasters and population densities above 120 per square km. The study then quantifies spectrum efficiency gains in regions where broadcasters are not uniformly distributed. In particular, it considers the case where U.S. broadcasters in the UHF band continue to serve their coverage areas as of 2015. In this case, the amount of spectrum that can be freed from TV throughout the entire nation using these two approach is considerably smaller, but some additional bands can be freed from TV throughout much of the nation. Moreover, most of these spectrum gains can be obtained when only a minority of broadcasters change their technical approach.

This study examine the theoretical and empirical perspectives of the symmetric Hawkes model of the price tick structure. Combined with the maximum likelihood estimation, the model provides a proper method of volatility estimation specialized in ultra-high-frequency analysis. Empirical studies based on the model using the ultra-high-frequency data of stocks in the S\&P 500 are performed. The performance of the volatility measure, intraday estimation, and the dynamics of the parameters are discussed. A new approach of diffusion analogy to the symmetric Hawkes model is proposed with the distributional properties very close to the Hawkes model. As a diffusion process, the model provides more analytical simplicity when computing the variance formula, incorporating skewness and examining the probabilistic property. An estimation of the diffusion model is performed using the simulated maximum likelihood method and shows similar patterns to the Hawkes model.

A significant requirement of low-cost sensor systems for defect detection and characterization is to bridge the gap of nondestructive testing & evaluation (NDT&E) and structural health monitoring (SHM). This paper introduces an ultra-high frequency (UHF) passive RFID sensor system for crack detection and potential structural monitoring. The working principles and major research challenges are presented for the new concept of NDT&E sensor systems. One novel approach using 3D antenna and kernel principal component analysis (PCA) is investigated and validated in conjunction with two case studies for evaluation of open and closed cracks. This proposed method can partly alleviate the nonlinearity from wireless channel and demonstrate the feasibility of the in-situ motoring through amplitude and phase of tag’s backscattered signals.

This paper presents an empirical model to predict attenuation in forest environments considering parameters related to vegetation. Typically, environmental parameters are only included in theoretical models, but they are more difficult to apply. The developed model uses tree density, average tree canopy diameter and foliage density as input parameters. The foliage density is very difficult to determine since it depends on the characteristics of trees. A simple metric of this parameter was obtained by measuring the background light silhouetted by the canopy. The model was developed with measurements obtained in different forest environments for two frequencies within the UHF band (Ultra High Frequency). A procedure was also applied to extend the operating frequency range of the model.

Present framework is established to deal with the refractivity variations normally affected the radio waves propagation at different frequencies, ranges and different environments. To deal such kind of effects, many researchers proposed several methodologies. One method is to use the parameters from meteorology to investigate these effects of variations in refractivity on propagation. These variations are region specific and we have selected a region of one kilometer height over the English Channel. We have constructed different modified refractivity profiles based on the local meteorological data. We have recorded more than 48 million received signal strength from a communication links of 50 km operating at 2015 MHz in the Ultra High Frequency band giving path loss between transmitting and receiving stations of the experimental setup. We have used parabolic wave equation method to simulate an hourly value of signal strength and compared the obtained simulated loss to the experimental loss. The analysis is made to compute refractivity distribution of standard (STD) and ITU (International Telecommunication Union) refractivity profiles for various evaporation ducts. It is found that a standard refractivity profile is better than the ITU refractivity profiles for the region at 2015 MHz. Further, it is inferred from the analysis of results that 10 m evaporation duct height is the dominant among all evaporation duct heights considered in the research. Keywords: Refractive index, Refractivity, Parabolic wave equation, Propagation, UHF, Antennas

Maintenance costs for infrastructures, for example bridges, have been increasing especially in developed countries. The slabs are apparently important parts in bridges, however the structural condition evaluation requires lots of manpower and really time-consuming because dense hammering tests should be conducted in present inspection method. To overcome this difficulty, a non-contact inspection technique using radar is focused on in this research. Radar techniques have been utilized in the fields of mine-search, oil-source search, geographical archeology etc. However, those searches are done by just visually checking reflected-wave image and their evaluation strongly depends on the inspectors’ ability and expertise. To more effectively utilize those radar techniques in bridge slab condition evaluation, the analysis of the reflected wave signals should be made automatic, fast and objective because huge amount of bridges to be inspected exist. In this research, to detect the damage of slab, some signal processing techniques for the reflected wave signal measured by UHF-band fast scanning non-contact SF-CW type radar are proposed, and their validity are shown by applying them to the signals obtained in real field bridge decks and full-scale bridge deck models in which some ideal damages are embedded.