Ultra High Frequency Band Research Articles

A Framework to Determine Secure Distances for Either Drones or Robots Based Inventory Management Systems

We propose a framework to determine a secure distance between a drone with an ultrahigh-frequency band radio frequency identification (UHF band RFID) reader and metallic objects affixed with RFID tags. The secure distance avoids order changes in received signal strength indicator (RSSI) values among the identified RFID tags in the field of view of the RFID reader. This distance enables a drone operator to securely operate the drone while identifying the RFID tag on the front of an object based on the measurements of RSSI values. An RFID tag located on the front of an object provides the maximum RSSI value. However, multipath propagation alters the RSSI values. Therefore, a framework is needed to determine a secure distance considering the multipath effects. Although inventory management systems based on drones and RFID systems have been proposed to date, this article establishes a framework to determine the secure distance. In the proposed framework, RFID tag and reader radiation patterns and multipath propagation effects were considered. The proposed framework was evaluated theoretically and experimentally. To evaluate and demonstrate the secure distance, we measured the RSSI values of two RFID tags attached to a metallic balcony. The height from the ground and spacing of the two RFID tags were 1.5 m and 1.3 m, respectively. In this environment, the secure distance was 3.8 m. The experimentally obtained distance that avoids order changes in RSSI values corresponded well with that obtained by this framework. The proposed secure distance is crucial when either drones or robots are introduced to inventory management systems.

Attenuating Broadband Electromagnetic Waves in Dielectric-Barrier Discharge Plasmas

Aircraft stealth by avoiding radar detection relies on shape and materials, but these are ineffective in attenuating electromagnetic (EM) waves in the ultrahigh frequency (UHF) band. This article investigates broadband EM wave attenuation in dielectric-barrier discharge (DBD) plasmas. We used a simplified collisional-radiative model to determine the electron density distribution using 2-D emission spectra and found that the gas pressure has a great effect on electron density. An empirical relationship between the gas pressure and electron density is given. We introduce a parameter optimizing method for multilayer plasmas that combines the attenuation characteristics of EM waves in plasma. We also establish an ideal multilayer plasma model to calculate the EM wave attenuation in the UHF band. The results show that multilayer plasmas can effectively enlarge the effective attenuating frequency range of EM waves and also attenuate UHF EM waves. On the basis of the calculation results, we propose a single-layer plasma generator. A large-area and homogenous plasma under medium-to-high gas pressure can also be created by discharge with argon or a mixture of argon and helium.

A miniaturized circularly polarized implantable RFID antenna for biomedical applications

A miniaturized circularly polarized implantable antenna operating at ultrahigh frequency band (902-928 MHz) for radio frequency identification biomedical monitoring is first presented and experimentally validated in this article. The proposed antenna features a compact volume with a dimension of π × (6)2 × 1.27 mm3 by employing an extended ring with meandered lines for size reduction. Moreover, adjusting the length of symmetrical meandered lines can introduce two orthogonal modes, which makes for good performance of circular polarization. Superb impedance matching between the chip and tag antenna is well implemented by applying a modified T-match stub. In the simulation, the antenna achieves a −10-dB impedance bandwidth of 42 MHz (902-944 MHz) and 3-dB axial-ratio bandwidth is 53 MHz (892-945 MHz). Finally, the specific absorption rate is also calculated for human safety and the measured reading range reaches the maximum distance of about 87 cm.

Design of a Tunable Absorber Based on Active Frequency-Selective Surface for UHF Applications.

An ultrathin tunable absorber for the ultrahigh frequency (UHF) band is presented in this paper. The absorber is a single-layer structure based on the topology of a Salisbury screen, in which the conventional resistive layer is replaced by an active frequency-selective surface (AFSS) loaded with resistors and varactors. The reflectivity response of the absorber can be controlled by adjusting the reverse bias voltage for the varactors, which is verified by both simulated and measured results. The experimental results show that the reflectivity response of the absorber can be modulated below −10 dB over a frequency band ranging from 415 to 822 MHz. The total thickness of the absorber, 10 mm, is equivalent to only λ/72 of the lower limit frequency. The absorbing mechanism for the designed absorber is illustrated by simulating the volume loss density distributions. A detailed analysis is also carried out on the basis of these parameters, such as the AFSS shape, resistor, thickness of the foam, thickness and permittivity of the dielectric substrate, and incident angles, which contribute to the reflectivity of the AFSS absorber.

Miniaturized UHF/UWB Tag Antenna for Indoor Positioning Systems

A miniaturized ultrahigh frequency (UHF)/ultra-wideband (UWB) dual-band tag antenna with a geometrical dimension of 34.6 mm × 21.5 mm × 6 mm is presented for indoor real-time positioning systems. A small patch is employed as the UWB radiator, and two U-shaped striplines are used for the UHF band. A quarter-wavelength metallic strip is introduced under the UWB patch to create an extra resonance to further expand the operation bandwidth. The antenna is backed by a ground plane to reduce the backside radiation and to improve the antenna gain in the UWB band. The measured bandwidth covers the frequency range from 919 to 931 MHz in the UHF band and 3.28 to 6.95 GHz in the UWB band with VSWR better than 2:1. The measured radiation patterns within the above-mentioned UHF and UWB frequency bands are very stable. The attractive features of compact size and wide bandwidth make it a very competitive candidate of tag antenna for indoor positioning systems.

MmWave UAV Networks With Multi-Cell Association: Performance Limit and Optimization

This paper aims to exploit the fundamental limits on the downlink coverage and spatial throughput performances of a cellular network comprised of a tier of unmanned aerial vehicle (UAV) base stations (BSs) using the millimeter wave (mmWave) band and a tier of ground BSs using the ultra high frequency (UHF) band. To reduce handover signaling overhead, the ground BSs take charge of control signaling delivery whereas the UAVs are in charge of payload data transmission so that users need to be simultaneously associated with a ground BS and a UAV in this network with a control-data plane-split architecture. We first propose a three-dimensional (3D) location distribution model of the UAVs using stochastic geometry which is able to generally characterize the positions of the UAVs in the sky. Using this 3D distribution model of UAVs, two performance metrics, i.e., multi-cell coverage probability and volume spectral efficiency, are proposed. Their explicit low-complexity expressions are derived and their upper limits are found when each of the UAVs and ground BSs is equipped with a massive antenna array. We further show that the multi-cell coverage probability and the volume spectral efficiency can be maximized by optimally deploying and positioning the UAVs in the sky and thereby their fundamental maximal limits are found. These important analytical findings are validated by numerical simulations.

Ham Radio and the Pony Express: Providing Communication in Remote Areas

The Pony Express provided mail service between Sacramento, California, and St. Joseph, Missouri, using relays of horse-mounted riders from 3 April 1860 to October 1861. The route, shown in Figure 1, was roughly 1,966 mi (3,164 km) long, through country inhabited mainly by Native Americans with a few scattered white settlements in the western United States. The Pony Express is reenacted annually, with riders galloping day and night to carry the mail across the country. Ham radio operators provide emergency communication for this event across the remotest sections of the route, using a variety of base and repeater stations, handheld and vehicle-supported radios; ultrahigh frequency (UHF), very HF (VHF), and HF bands; and an array of deployed antennas, described in this article.

Rectangular Loop UHF Antenna for utilization of TVWS for Cognitive Radio Application

To utilize the TV white space 470MHz to 806MHz, several wideband antennas are designed in ultra-high frequency (UHF) band. This paper presents the monopole antenna with resonant structures arranged in rectangular loop shape. The overall dimension of the antenna is 160mm x 100mm x 1.6mm. The performance of the antenna in the operating frequency band 596MHz to 733MHz is evaluated using HFSS software. The overall peak gain of the antenna is 1.653dB. In both elevation and azimuth plane, radiation pattern is omnidirectional and the radiation efficiency is 81.79%

Electrically Small Water-Based Hemispherical Dielectric Resonator Antenna

Recently, water has been proposed as an interesting candidate for use in applications such as tunable microwave metamaterials and dielectric resonator antennas due to its high and temperature-dependent permittivity. In the present work, we considered an electrically small water-based dielectric resonator antenna made of a short monopole encapsulated by a hemispherical water cavity. The fundamental dipole resonances supported by the water cavity were used to match the short monopole to its feed line as well as the surrounding free space. Specifically, a magnetic (electric) dipole resonance was exploited for antenna designs with a total efficiency of 29.5% (15.6%) and a reflection coefficient of −24.1 dB (−10.9 dB) at 300 MHz. The dipole resonances were effectively excited with different monopole lengths and positions as well as different cavity sizes or different frequencies in the same cavity. The overall size of the optimum design was 18 times smaller than the free-space wavelength, representing the smallest water-based antenna to date. A prototype antenna was characterized, with an excellent agreement achieved between the numerical and experimental results. The proposed water-based antennas may serve as cheap and easy-to-fabricate tunable alternatives for use in very high frequency (VHF) and the low end of ultrahigh frequency (UHF) bands for a great variety of applications.

Street‐Scale Mapping of Urban Radio Frequency Noise at Very High Frequency and Ultra High Frequency

AbstractModern measurement campaigns of man‐made radio frequency (RF) noise have reported results from fixed locations that are assumed to be representative of the surroundings. Models derived from these measurements include parameters to express the variability in time and in space over very large distances (i.e., differences between cities). Despite the rapidly evolving mixture of noise sources, especially in modern urban environments, spatial variation of RF noise power at the scale of streets and blocks is essentially unknown in the very high frequency and ultra high frequency bands. Using a portable calibrated noise measurement system of our design, RF noise was recorded over a 1‐MHz bandwidth for frequencies of 142.0, 246.5, and 972 MHz. Noise surveys were conducted during daytime working hours in two different neighborhoods within Boston, Massachusetts, USA, with each survey transiting a fixed, several kilometer long route, repeated twice to enable separation of temporal from spatial variability. Significant and spatially repeatable variations in median power, peak power, and voltage deviation were observed over distances of tens to hundreds of meters, dependent upon the measurement frequency. The observed spatial patterns of median and peak power appear to be repeatable on timescales of hours to weeks, and likely beyond, suggesting that these noise patterns are persistent features of the urban environment.

Efficiency‐based approach to quantifying ‘tuneability’ performance in frequency‐agile narrowband antennas

Many communications systems require reconfigurable band access in compact form factors. Contemporary literature routinely reports `tuneability' (or frequency agility) in input response terms ( S 11 ), yet repeatable efficiency data were reported in <;40% of cases surveyed. Despite the low efficiencies associated with many tuneable narrowband antennas, e.g. electrically small antennas (ESAs), reference methods to quantify tuneability in terms of a tuned range of realised antenna efficiency, average efficiency in the band and integrated efficiency-bandwidth product do not exist and thus have not been widely adopted. Here, these metrics have been formulated for general application to efficiency-based tuneability assessment of narrowband antennas. Application to a set of fixed-frequency/varactor-tuned ESAs ( ka = 0.19-0.31) in the ultra-high frequency band is demonstrated. Tuning range of 10% or 25% realised efficiency was found to be several times narrower than S 11 <; -6 dB tuning range for antennas in this study and in the literature, highlighting the need for a shift to efficiency-based tuneability reporting in support of RF system design analysis. The integrated efficiency-bandwidth product has been demonstrated for combined efficiency and reconfigurability comparison of tuneable antennas, providing a platform for future performance grading of a diverse range of antenna tuning technologies.

Long read range and flexible UHF RFID tag antenna made of high conductivity graphene‐based film

An antenna made of a graphene-based film with organic polyimide precursor of high conductivity 1.1 × 106 S m−1 and thickness 30 μm, operating in the ultrahigh frequency (UHF) band for radio frequency identification applications is presented in this article. The antenna is optimized to have a conjugate match to the impedance of the chip by tuning the design parameters. Tags are fabricated and tested using the designed antenna, which are shown to have realized gain above −1.5 dBi and radiation efficiency beyond 90% in the whole UHF band from 860 to 960 MHz. The read range of proposed tag is greater than 12.3 m over the entire UHF band with a maximum value of 14 m at 920 MHz. In addition, the flexibility of the tags is demonstrated. After 2000 cycles of bending and stretching, the read range only decreases by 4.5 m comparing to the initial state at 915 MHz.

Compact Wideband Internal Antenna Using Epsilon Negative Zeroth-Order Resonator With CPWG-Fed for UHD-TV Applications

A compact wideband internal antenna based on an epsilon negative (ENG) zeroth-order resonator (ZOR) is proposed to operate in the ultra-high frequency (UHF) band (470–771 MHz) for ultra-high-definition television (UHD-TV) applications. The antenna having a compact size of 9 × 220 mm2 is placed on the top edge of the 49-inch TV model. The bezel frame of the TV model is used as the substrate of the antenna. The antenna is fed by a coplanar waveguide with a ground plane (CPWG). A shorting plate was added to expand the ground plane of the CPWG structure to achieve resonance at lower frequencies. The ENG structure is formed by a meander line that generates zero-order resonances at higher frequencies in the UHF band. Based on analysis, the proposed antenna is fabricated and tested. The measurement results show that the reflection coefficient (S11) is under − 6 dB in a wide frequency range from 440 to 910 MHz covering the entire UHF band. The fractional bandwidth is extended up to 69% with a peak gain of 4.8 dBi, and the average radiation efficiency of the antenna is 75%.

Internal Reconfigurable Dipole–Loop Antenna Array for High Reception Rate of Wideband UHD-TV Applications

An internal reconfigurable Dipole–Loop antenna array, covering the entire ultra-high frequency (UHF) band for ultra-high definition television (UHD-TV) applications is presented. The internal antenna array is used to overcome the influence of electromagnetic interference when integrating the antenna element inside the TV model and to increase the gain and reception rate of receiving signals for television broadcasting. The antenna array is designed based on the Dipole–Loop antenna elements, placing on substrate material PC-ABS (polycarbonate-acrylonitrile butadiene styrene: er = 3.5, tan δ = 0.005) of the bezel frame in the TV model. By simultaneously switching PIN diodes with two ON/OFF states, the antenna array can be frequency reconfigured to achieve a wide operating bandwidth for UHF (470–771 MHz) band. The spacing between the antenna elements in the array at each mode is chosen as 0.5λ0 (λ0 represents the free space wavelength of the highest frequency in the operating band). The proposed antenna array is designed, fabricated, and tested for experimental verification. Measurement results show that the antenna array is good for high reception rate of UHD-TV applications, with a − 6 dB impedance bandwidth of 51.6% (460‒780 MHz), covering the whole UHF band. The 3 dB gain bandwidths of 42.5% and 54.6% are obtained with peak realized gains of 9.6 dBi and 8.5 dBi for the horizontal and vertical polarizations, respectively. In addition, the diversity performance parameters are obtained and evaluated using the mean effective gains of the elements, and the diversity gain using both simulation and measurement results. It shows that the proposed antenna array can receive multi-side signals, applied in diversity and MIMO systems.

Ultra‐high‐frequency wideband circularly polarized crossed‐dipole antenna with wide axial‐ratio beamwidths for SATCOM applications

AbstractIn this study, an ultra‐high‐frequency (UHF) wideband circularly polarized (CP) crossed‐dipole antenna with wide axial‐ratio beamwidth (ARBW) is proposed for SATCOM applications. The antenna is composed of two pairs of dipoles with umbrella‐shaped arms, and they are fed by a feeding network to generate CP radiation. Two pairs of parasitic patches are introduced symmetrically between the dipole arms and the ground plane. Due to coupling of the dipoles, currents can be induced on to the metal patches, which can not only decrease the antenna volume by increasing the current path of the dipole arms, but also additional radiation can be provided to enhance the ARBW. A prototype of proposed antenna was fabricated and measured. The measured results indicate that it operates at the UHF band ranging from 280 to 420 MHz, with a –10‐dB impedance bandwidth of 40.5% and a 3‐dB AR bandwidth of 42%. Furthermore, the antenna exhibits a 3‐dB ARBW of more than 190°within a wide operating band of 23.1%.

A Noise Reduction Based Wavelet Denoising System for Partial Discharge Signal

Partial Discharge (PD) checking is a standout amongst the best technique for insulation condition evaluation of HV power system. PD releases inside a power transformer energize electromagnetic transients that can be identified utilizing sensors working in the ultra-high frequency band. Despite, on-line PD estimations are influenced by elevated amounts of electromagnetic interference that makes delicate PD identification exceptionally troublesome. In our proposed research present an approach which can reduce the noise level. Increase the quality of the PD signal. Here using an approximation logic which can reduce the complexity in terms of time and able to improve the quality. The proposed Double DWT able to get batter result as compares to existing PD techniques.

Pattern Reconfigurable Metasurface Antenna for Electromagnetic Torso Imaging

A pattern reconfigurable metasurface antenna for an electromagnetic torso imaging system operating at the ultrahigh frequency (UHF) band is presented. To meet the requirements of electromagnetic torso imaging, the antenna can scan the human chest with steerable unidirectional radiation patterns. The designed antenna consists of three rectangular microstrip-fed slot radiators illuminating a metasurface layer with $7\times 5$ unit cells to cover the whole chest. Six p-i-n diodes are used to switch the radiating slots creating different beams. The unit cell dimensions are $0.125\lambda _{0}\times 0.125\lambda _{0}$ and the antenna has a low profile of $0.9\lambda _{0}\times 0.7\lambda _{0}\times 0.06\lambda _{0}$ ( $\lambda _{0}$ is the wavelength of the lowest operating frequency of the antenna). The antenna creates three distinct beams with a peak gain of 8 dBi at 1 GHz and 2 dBi gain variations across different beams over its measured wide operating frequency bandwidth of 27% at 0.8–1.05 GHz. A complete electromagnetic torso imaging system, which utilizes the designed antenna, is built and is successfully tested to detect 20 mL of fluid (water) inside the torso, thus differentiating between healthy and unhealthy cases.

WRC-19 and 5G Spectrum Planning

This paper predicts the likely outcome of spectrum planning work on fifth generation wireless (“5G”) services at the 2019 World Administrative Conference (“WRC-19”). It considers whether the United States delegation to the conference embraced old lessons about International Telecommunication Union (“ITU”) spectrum management and emerging ones generated by the new technologies and services 5G will offer, as well as growing national security and industrial policy concerns. Well before WRC-19, carriers in many nations have begun to offer wireless services using the 5G label. These carriers have acted in advance of finalized spectrum allocation decisions and risk rolling out services on frequencies that may not match a future global consensus. This paper identifies opportunities and benefits in an expedited, unilateral approach, but also notes the potential for significant threats and costs, particularly in light of known, but apparently ignored, or forgotten lessons about global and national spectrum planning. At WRC-15, the United States largely failed to secure consensus support for expanding global spectrum allocations to include more bandwidth near existing allocations in the Ultra High Frequency band and at extremely high, single and double digit GigaHertz frequencies. This paper considers whether changes in WRC-19 preparations by the United States delegation and in the attitudes of delegations from other nations will support expedited consideration of 5G frequency allocations throughout the usable radio spectrum. The paper concludes that determining whether the United States achieved success depends in large part on one’s understanding of the pace, nature, procedures and goals of the ITU spectrum planning process. Observers, including FCC commissioners of both political parties, have complained about flaws in the ITU administrative process that contributed to the absence of efforts to expedite rollout of 5G services and other national objectives. Proponents of the process support the ITU as methodical, thorough, consensus driven and conflict avoiding. WRC-19 will likely generate the same inconsistent evaluations.

Design, implementation, and test of an SDR for NVIS communications

SummaryAlthough many physical layer solutions have appeared for remote sensors and Internet of things during the recent years, none of them is suited to very remote sensors in areas away from any mobile operator coverage. In that case, a solution on the basis of near vertical incidence skywave (NVIS) with reflection in the ionosphere may be very attractive. Using NVIS, no line of sight is needed and the coverage is much bigger than any other system operating in either the very high frequency (VHF) or ultra high frequency (UHF) band. In this paper, we present a new transmission scheme for very remote sensors using the NVIS transmission technique.

Wideband UHF and SHF long-range channel characterization

This paper presents an outdoor long-range (from 315 m up to 5.3 km) fixed channel campaign for both ultra high frequency and super high frequency bands with co-polarized horizontal and vertical antenna configurations. It investigates the channel characteristics of device to device communication scenarios underlaying the 5th generation networks by providing detailed research. Both line of sight and non-line of sight measurements in 1.3 GHz and 5.8 GHz frequency bands with bandwidth up to 600 MHz were conducted. The path loss, root mean square delay spread, coherence bandwidth, and channel frequency response variation are characterized. We observed that the variation is negligible in microcell line of sight environment for both above mentioned frequencies, whereas it significantly increases with frequency in different macrocell non-line of sight environments. The distance dependency of path loss was also derived. It was observed that the root mean square delay spread decreases with frequency for both line of sight microcell and non-line of sight macrocell measurements. A dependency between the root mean square delay spread and transmitter-receiver distance in non-line of sight environments was also captured. The relation between the coherence bandwidth and the root mean square delay spread was depicted. It demonstrates an exponential function in all considered channel combinations.