Super High Frequency Band Research Articles

Influence of a Tailored Oxide Interface on the Quality Factor of Microelectromechanical Resonators (Adv. Mater. Interfaces 9/2023)

Microelectromechanical Resonators The cover art illustrates an aluminum nitride transduced microelectromechanical resonators, as described by David D. Lynes and Hengky Chandrahalim in article number 2202446. By including a tailored oxide thin film in the resonator's body, the quality factor is increased by up to 400% for devices operating at very high frequency and super high frequency bands. The quality factor enhancement persists at operating temperatures as low as −200 °C up to +200 °C.

Investigations into the Effect of High-Ordering the Log-Distance Dependency of Path Loss Models for Indoor Wireless Channels

The massively available amounts of bandwidth that exist in the frequency regime beyond 6 GHz together with the inability of the previous frequencies below 6 GHz have attracted the attention of the research and industrial communities to consider new frequency bands such as Super-High Frequency (SHF), millimeter-wave (mmWave), and further high-frequency bands such as the Terahertz (THz) bands to be the promising solutions to cope with the explosive demand of higher mobile data rate traffic. As a result, many research studies have reported the main wireless channel’s characteristics, such as the path loss over wide ranges of the SHF, mmWave, and THz frequency bands. However, most of the path loss modeling research has adopted the well-known close-in (CI) free space reference distance model to describe propagation effects of the wireless channel leaving behind the improvement concept. It is vital to estimate the path loss accurately since these high-frequency bands significantly suffer from the wireless propagation effects because of their tiny wavelength. This study presents investigations on high-ordering the dependency of the standard CI path loss model on the distance between the transmitting and the receiving antennas in the logarithmic scale. Two improved models are provided and discussed in this work: second-order CI and third-order CI models. The validation of the models’ accuracy is based on measurement data collected in a typical indoor corridor environment at 14, 18, and 22 GHz frequency bands. The main results show that the proposed two models outperform the standard CI model. Moreover, the results reveal notable reductions in the shadow fading’s standard deviation values as the model’s order increases. This means that more precision is provided. Finally, a trade-off study between the model’s accuracy and simplicity is provided in this paper.

An Efficient Approach of Improving Path Loss Models for Future Mobile Networks in Enclosed Indoor Environments

Path loss is the primary factor that determines the overall coverage of networks. Designing reliable wireless communication systems requires accurate path loss prediction models. Future wireless mobile systems will rely mainly on the super-high frequency (SHF) and the millimeter-wave (mmWave) frequency bands due to the massive available bandwidths that will meet projected users’ demand, such as the needs of the fifth-generation ( $5G$ ) wireless systems and other high-speed multimedia services. However, these bands are more sensitive and exhibit a different propagation behavior compared to the frequency bands below $6~GHz$ . Hence, improving the existing models and developing new models are vital for characterizing the wireless communication channel in both indoor and outdoor environments for future SHF and mmWave services. This paper proposes an efficient improvement of the well-known close-in (CI) free space reference distance model and the floating-intercept (FI) model. Real measured data was taken for both line-of-sight (LOS) and non-line-of-sight (NLOS) communication scenarios in a typical indoor corridor environment at three selected frequencies within the SHF band, namely $14~GHz$ , $18~GHz$ , and $22~GHz$ . The research finding of this work reveals that the proposed models have better performance in terms of their accuracy of fitting real measured data collected from measurement campaigns. In addition, this work studies the impact of the angle of arrival and the antenna heights on the current and improved CI and FI models. The results show that the improved models provide better stability and sensitivity to the change of these parameters. Furthermore, the mean square error between the models and their improved versions were presented. Finally, this paper shows that shadow fading’s standard deviation can have a notable reduction in both the LOS and NLOS scenarios (especially in the NLOS), which means higher precision in predicting the path loss.

A Graphene Field-Effect Transistor Based Analogue Phase Shifter for High-Frequency Applications

We present a graphene-based phase shifter for radio-frequency (RF) phase-array applications. The core of the designed phase-shifting system consists of a graphene field-effect transistor (GFET) used in a common source amplifier configuration. The phase of the RF signal is controlled by exploiting the quantum capacitance of graphene and its dependence on the terminal transistor biases. In particular, by independently tuning the applied gate-to-source and drain-to-source biases, we observe that the phase of the signal, in the super-high frequency band, can be varied nearly 200 degrees with a constant gain of 2.5 dB. Additionally, if only the gate bias is used as control signal, and the drain is biased linearly dependent on the former (i.e., in a completely analogue operation), a phase shift of 85 degrees can be achieved making use of just one transistor and keeping a gain of 0 dB with a maximum variation of 1.3 dB. The latter design can be improved by applying a balanced branch-line configuration showing to be competitive against other state-of-the-art phase shifters. This work paves the way towards the exploitation of graphene technology to become the core of active analogue phase shifters for high-frequency operation.

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.

Sensitive Damage Detection of Reinforced Concrete Bridge Slab by “Time-Variant Deconvolution” of SHF-Band Radar Signal

In this paper, we focus on ground-penetrating radar (GPR) for infrastructural health monitoring, especially for the monitoring of reinforced concrete (RC) bridge slab. Due to the demand of noncontact and high-speed monitoring technique which can handle vast amounts of aging infrastructures, GPR is a promising tool. However, because radar images consist of many reflected waves, they are usually difficult to interpret. Furthermore, the spatial resolution of system is not enough considering the thickness of target damages, cracks, and segregation are millimeter-to-centimeter order while the wavelength of ordinary GPR ultrahigh-frequency band is over 10 cm. To address these problems, for the purpose of sensitive damage detection, we propose a new algorithm based on deconvolution utilizing a super high-frequency (SHF) band system. First, a distribution of reflection coefficient is inversely estimated by 1-D bridge slab model. Because concrete is found to be a lossy medium at SHF band, we consider the attenuation of signal in deconvolution. The algorithm is called “time-variant deconvolution” in this paper. After the validation by simulation, the effects of the algorithm and frequency band on damage detection accuracy are evaluated by a field experiment. Though the results show a 1-mm horizontal crack is not detected by measured waves, when it is filled with water, it is detected by time-variant deconvolution. Moreover, the 1-mm dried crack is detected only by time-variant deconvolution at SHF band, which greatly emphasizes the peaks of the reflection coefficient of the crack.

Analysis of nested design of plasma antenna based on the azimuthally symmetric surface waves: UHF and SHF bands

In this paper, a plasma antenna nested inside a plasma tube, called the nested model of the plasma antenna, as a suitable candidate to improve the conventional plasma antenna is theoretically investigated in ultra-high frequency (UHF) and super high frequency (SHF) ranges. Using the Fluid-Maxwell equations, the dispersion relations for both the nested model of plasma antenna and single plasma antenna and single plasma antenna are obtained to find their practical, vph≥0.85c, azimuthally symmetric surface modes. The numerical results for the single plasma antenna show that the number of practical modes is very limited in the UHF range, and in the SHF range, the phase velocities of the modes radiating over this range are mostly lower than the speed of light in vacuum. However, the results of the considered nested model indicate that in the UHF range, the number of practical modes greatly increases, and by optimizing the plasma tube parameters, the generated modes can extend over all this range, forming a mode line with the phase velocity very close to the speed of light. On the other hand, in the SHF range, employing the nested model leads to an additional mode line having higher phase velocity (coinciding with the light speed line under the optimum conditions) with respect to that of the single plasma antenna. Using the proposed nested model of the plasma antenna not only leads to clearly significant advances in the single plasma antenna but also is more controllable due to adding the plasma tube parameters.

A Low Complexity Iterative SLM-OFDM for SHF band applications

The transmitted Orthogonal Frequency Division Multiplexing signal in systems such as Wireless LAN,Mobile WiMAX, Digital Video Broadcasting (DVB) operating in the Super High Frequency (SHF) band suffers from high Peak to A verage P ower R atio .This is reduced in S elective L evel M apping  (SLM)  approach  b ut  at  the  expense  of  increased complexity.  In this paper,w e propose a iterative selective level mapping algorithm for PAPR reduction with reduced computation complexity . The performance of Iterative SLM is investigated for a new phase sequence set based on mutually orthogonal Golay complementary pairs and results are compared with Walsh-Hadamard sequence set. The iterative threshold is varied between 4-8 dB and candidate signal values of 4,8,16 and 32 are considered for a 64 subcarrier system. Computer simulation results show lesser  computational complexity  in terms  of candidate signal requirement in comparison to conventional SLM, while maintaining an almost identical PAPR.  The new phase sequence set achieves a 1.2 dB and 2.4 dB PAPR improvement over conventional SLM and OFDM respectively for maximum of 16 candidate signals at iterative threshold of 6 dB. The computational complexity reduction achieved is 59%.  Â

BEAM BROADENED RADIAL LINE SLOT ARRAY ANTENNA FOR FIFTH GENERATION (5G) MOBILE BROADBAND COMMUNICATION

Radial line slot array antenna with broad beam is easily realized at frequencies in the lower part of super high frequency band. But emerging broadband mobile communication systems like the fifth generation target frequencies in the upper part of the band and beyond. Therefore, this paper presents the design of beam broadened radial line slot array antenna at 28 GHz for fifth generation broadband mobile communication system. Surface slot distribution synthesis was carried on beam squinted standard single layer radial line slot array design to achieve the broad beam. Using computer simulation technology microwave studio 2014 software, 85 mm radius antenna having polypropylene (ɛr = 2.33) as cavity material was realized. Simulated results shows a gain of 15.8 dB, impedance bandwidth of 1.6 GHz, radiation efficiency of 96 % and 3 dB half power beamwidth of up to 32.3o.

RFID tag antenna for ultra and super high frequency band applications

A novel dual-band antenna for radio frequency identification tag is proposed for ultra high frequency (UHF: 915 MHz) and super high frequency (SHF: 2450 MHz) bands. The proposed tag antenna is a single sided dual-antenna structure, designed on the grounded (metallic) dielectric substrate. The proposed tag antenna can be used on any kind of surfaces including metals without severe performance degradation due to its metallic ground plane. At UHF band, proposed tag antenna works as dual-antenna structure. In the dual-antenna structure, one antenna works for receiving and another for backscattering. Due to separate backscatterer, the maximum differential radar cross section improved and results in the enhancement of the maximum read range. Whereas at SHF band, proposed antenna works as conventional single antenna structure and during operations it switches between receiving and backscattering modes. The proposed antenna consists of a meandered line antenna and a rectangular patch antenna loaded with an F-shaped and an inverted L-shaped slots. The S-parameters are measured by means of differential probe technique. Simulated and measured results are observed in good agreement. The read range is observed about 5 and 6 m at 915 and 2450 MHz, respectively. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:640–650, 2016.

Estimation of the Propagation Impairments of Satellite Systems Design in the SHF and EHF Bands in Subtropical Region

Super high frequency (SHF) to extremely high frequency (EHF) bands offer many advantages such as scalability, high asymmetrical traffics and the ability to permit highspeed digital communications due to larger bandwidths among others. However, frequencies greater than 10 GHz leadto signal fading due to physical phenomena related to the propagation of radio waves through the atmosphere. In order to ensure the necessary Quality of Service (QoS) against various transmissions and other impairments at these coverages, not only rain attenuation, which is recognized to be the most significant impairment must be considered. Extra fading due to tropospheric constituents, like snow, water vapour, clouds, gaseous and scintillations caused by air turbulence must also be considered. In this paper, the effects of rain attenuation A (dB) in a heavy rainfall sub-tropical regions for SHF and EHF bands at a given carrier frequency in an average year has been estimated by the synthetic storm technique (SST) and an associated formula that links A to frequency for fixed probabilities. Additional fading due to water vapor, clouds, oxygen and scintillations is estimated by applying the ITU-R formulae. The total attenuation (rain attenuation plus other propagation impairments) obtained is applied to Quadrature Phase Shift Keying (QPSK) modulation scheme en route Earth-satellite-Earth link, with regenerative transponders, in order to obtain a specify maximum bit error rate (BER) tolerated by the end users.

Synthesis and physicochemical properties of composites for electromagnetic shielding applications: a polymeric matrix impregnated with iron- or cobalt-containing nanoparticles

Magnetic, magnetic resonance, and structural properties of iron and cobalt nanoparticles embedded in a polyethylene matrix were studied. The materials were prepared by thermal decomposition of cobalt or iron formate in a polyethylene melt in mineral oil and contained from 2 to 40% wt. of metal. Transmission electron microscopy data indicate that the average diameter of particles is up to 8.0 nm. According to extended x-ray absorption fine structure and Mössbauer spectroscopy studies, the particles comprise a metallic core and nonmetallic shell which is chemically bound to the surrounding matrix. Electrophysical and magnetic properties of the materials prepared were studied along with their reflection and attenuation factors in the super high frequency band. The materials were found to be suitable for use in electromagnetic shielding.

A superhigh-frequency optoelectromechanical system based on a slotted photonic crystal cavity

We develop an all-integrated optoelectromechanical system that operates in the superhigh frequency band. This system is based on an ultrahigh-Q slotted photonic crystal (PhC) nanocavity formed by two PhC membranes, one of which is patterned with electrode and capacitively driven. The strong simultaneous electromechanical and optomechanical interactions yield efficient electrical excitation and sensitive optical transduction of the bulk acoustic modes of the PhC membrane. These modes are identified up to a frequency of 4.20 GHz, with their mechanical Q factors ranging from 240 to 1730. Directly linking signals in microwave and optical domains, such optoelectromechanical systems will find applications in microwave photonics in addition to those that utilize the electromechanical and optomechanical interactions separately.

3-D transponder antennas for future SHF RFID applications

Abstract. The radio frequency identification (RFID) technology is omnipresent since a few years. Some of the most popular fields of application are the use for security tasks, for logistics and for the consumer segment. For example, chip card or key ring sized RFID transponders can allow wireless access to secured rooms. The number of applications for wireless data transmission for the identification and tracking of objects increases every year. There is a large development need for highly functional and inexpensive RFID transponders due to the ever-increasing demand on improved reliability, higher data rates and read and write ranges of the RFID systems. Therefore, research was performed on new 3-D transponder antennas for the Super High Frequency Band around 5.8 GHz. Additionally, wave propagation effects and the influence of different dielectric environments were considered. Parallel to the design of the novel antenna structures, the printing process for inexpensive manufacturing was investigated. The gained results are the basis for prospective RFID applications.

Effects of metal buffer layer on characteristics of surface acoustic waves in ZnO/metal/diamond structures

The interdigital transducer (IDT)/ZnO/metal/diamond structure is investigated for use in the design surface acoustic wave (SAW) devices in the super-high-frequency (SHF) band. Simulation results indicate that adding a metal buffer layer with a finite thickness significantly increases the coupling coefficient. In the Sezawa mode, the coupling coefficient is 4.71% when an Al interlayer is applied. This coupling coefficient is 75% and 77% larger than those in the IDT/ZnO/diamond and IDT/ZnO/shorted surface/diamond structures, respectively. The results in this study are useful in designing SAW devices using diamond-based structures with a large coupling coefficient in the SHF band.

Effects of conducting layers on surface acoustic wave in AlN films on diamond

The interdigital transducer (IDT)/AlN/conducting layer/diamond structures are investigated in this study to design surface acoustic wave (SAW) devices in the super high frequency band. Simulation results using the finite element method show that a thin conducting layer can effectively increase the coupling coefficient and, thus, broaden the bandwidth of SAW devices. For the Sezawa mode, it is illustrated that using a Ti layer with a layer thickness-to-wavelength ratio of 0.02 the maximum coupling coefficient is 2.546% and the associated SAW phase velocity is 10657 m/s at the AlN films’ thickness-to-wavelength ratio of 0.14. This coupling coefficient is 105% higher than that in the IDT/AlN/diamond structure. The research results can be applied to design SAW devices using diamond based structures in the super high frequency band.

Исследование безэховости компактного антенного полигона в диапазоне сверхвысоких частот

Исследование безэховости компактного антенного полигона в диапазоне сверхвысоких частот

Modeling of the scattering of electromagnetic waves by a thin dielectric coating on a cylinder

Double-sided boundary conditions containing only tangential components of a diffracted field are used to model the interaction of electromagnetic waves with a cylinder of arbitrary cross section covered with a thin dielectric layer. The obtained boundary-value problem is reduced to a system of two singular integral equations of the second kind with kernels whose structure is similar to the kernels of integral equations of the first kind for a perfectly conducting scatterer. The numerical solution of the integral equations of the problem is obtained by the method of mechanical quadratures. The scattering properties of an elliptic cylinder with different dielectric coatings are studied in the superhigh-frequency band. It is shown that the coating strongly affects the diffraction properties of the cylinder.

The SIRIO satellite, 1968–1977: Between scientific engagement and managerial inexperience

ABSTRACT: The story of the first Italian communications satellite, SIRIO, started in 1968, after the failure of the European project for the vector ELDO-PAS. The story up to the launch in 1977 involved the encumbering legacy of the San Marco satellite's success in the 1960s, political uncertainty in Italy, international economic crises of the 1970s, an overtly complex management system, and an inexperienced aerospace industry. Despite these handicaps, SIRIO won the race with its nearest competitor, the European satellite OTS, which had a similar research aim in the super high frequency band. In addition to collecting a large amount of useful data, SIRIO catalyzed the process for developing an improved organizational structure for Italian space research.

Measurement of specimen permittivity using a waveguide bridge

The proposed method for measuring the permittivity of the medium in the superhigh frequency band makes use of the depolarizing effect of the electromagnetic field. Upon exposing a dielectric particle to an electromagnetic field having a definitely oriented electric-field intensity vector, En, the reflected electric-field intensity vector, E0, will not, in general, coincide in direction with the incident field (as a result of depolarization). This depolarization depends upon the form and dimensions of the particle, on its permittivity, and on the wavelength.