Radio Frequency Range Research Articles

Link Budget Design for RF Line-of-Sight via Theoretical Propagation Prediction

Line-of-sight (LOS) link planning condition has been observed to have effects on the atmospheric factor which cause crucial signal loss. The main objective of the planning was to improve a set of a link using point to point condition to assist the performance in emerging its strategy for handling the fixed WLAN service. The purpose of this paper is to provide a quick description of various propagation loss mechanisms on Link Budget Tool (LBT). LBT is customized to create point to point link for local area network (LAN) through radio frequency range operating between 2.400 GHz and 5.800 GHz. This software is able to define the effect of signal loss and expected performances according to the distances between link propagation conditions based on a number of system parameters.

Conducted EMC testing reveals malfunctions in automated external defibrillators with patient leads connected

Previously we performed radiated electro-magnetic compatibility tests of automated external defibrillators (AEDs) for radiated immunity per the IEC 60601-1-2 and ANSI/AAMI/IEC 60601-2-4 standards, in the prescribed 80–2500 MHz radiofrequency range, with the patient leads connected. We observed malfunctions for several AEDs in the 30 to 45 MHz range. Our present study involves conducted (injected current) testing from 10 to 80 MHz using prescribed IEC methods. We now tested the same AEDs plus one. We injected 3 Vrms on the patient leads from 10 MHz–80 MHz and 6 Vrms at Industrial Scientific and Medical frequencies in this range. Ventricular fibrillation (V-Fib) signals and normal sinus rhythm (NSR) signals were delivered to the patient leads from an AED tester. We also performed radiated testing in the 70–90 MHz band with 10V/m and 20V/m to compare with conducted testing. For conducted tests three AEDs gave false diagnoses (failed to identify V-Fib signals) at some frequencies. For the radiated testing, only one AED gave a false diagnosis. Two of these AEDs are no longer produced but are still in use. Discrepancies between the radiated and conducted test results are due to basic differences in the test methods and mechanisms of interaction.

Investigation on Structural and Dielectric Properties of Silica Nanoparticles Incorporated Poly(Ethylene Oxide)/Poly(Vinyl Pyrrolidone) Blend Matrix Based Nanocomposites

Inorganic and organic materials based polymer nanocomposite (PNC) films, comprising silica (SiO2) nanoparticles as inorganic filler and the polymer blend of poly(ethylene oxide) (PEO) and poly(vinyl pyrrolidone) (PVP) as organic matrix (i.e., (PEO–PVP)-x wt% SiO2; x = 0, 1, 3 and 5) have been prepared by the solution-casting method. These PNC films are characterized by employing the scanning electron microscopy (SEM), X-ray diffractometer (XRD), Fourier transform infrared (FTIR) spectroscopy, and the dielectric relaxation spectroscopy (DRS). The effect of SiO2 nanofiller on the spherulite and porous morphology, miscibility of the polymers, PEO crystallite size, the degree of crystallinity, polymer–polymer and polymer-nanoparticle interactions, and from 20 Hz to 1 MHz range dielectric and electrical dispersion behaviour and also the structural dynamics of these PNC materials have been investigated. The porous morphology, structures of miscible phases, and the PEO crystallite length greatly alter with the incorporation of merely 1 wt% SiO2 in the polymer blend matrix which further changes with the increase of nanofiller concentration up to 5 wt%. The real part of complex permittivity over the radio frequency range (20 kHz–1 MHz) for these PNC films is found about 2 and their dielectric loss tangent values below 0.03, at the room temperature, which are significantly low. The contribution of interfacial polarization effect at lower audio frequencies enhances the complex permittivity of these materials linearly in the range 2 to 4 with the decrease of frequency from 1 kHz to 20 Hz confirming their frequency tunable dielectric behaviour. The dielectric study of 3 wt% SiO2 containing PNC film in the temperature range 30–60 °C reveals its thermally activated dielectric characteristics, and the temperature dependent values of dielectric relaxation time and dc electrical conductivity obey the Arrhenius behaviour with activation energies in the range 0.2–0.3 eV. The dielectric and electrical parameters ascertain the promising applications of these PNC films in the development of novel electroactive functional materials, and also their use as the dielectric substrate and electrical insulating polymeric nanodielectrics for the fabrication of flexible-type naturally degradable organoelectronic devices.

Simulator of Emission from Electric Propulsion Thrusters

Primary approaches are considered for the development of emission simulators from electric propulsion thrusters (EPTs) in the radio-frequency range, including both the use of the stored actual member functions for the processes characterizing the EPT emission in the specified frequency ranges and the processes that are formed on the basis of emission simulation models. Various approaches to emission simulation modeling from stationary plasma thrusters are discussed. A possibility to use the earlier-developed mathematical models and software packages to simulate the EPT emission is considered; these models describe the complex envelope of the emission processes from a stationary plasma thruster in the given frequency ranges. Primary principles for the development of the radio simulators of the wanted signals and interference are also discussed. The application of multichannel vector generators is substantiated in view of the growth in complexity of simulated signals and interference. In such generators, the quadrature components of the processes describing EPT emission are employed that were obtained by test or by the simulation modeling methods. As an example, the simulator for EPT emission in the radio-frequency range is studied. This simulator provides such an electromagnetic environment in the given spatial region that takes various combinations of valid signals, thermal noises, and EPT emission into consideration. Recommendations are proposed on the use of the emission simulator as a part of the ground modeling complexes for defining possible influence of EPTs on onboard spacecraft systems.

275–500-GHz Wideband Waveguide SIS Mixers

We have successfully demonstrated low-noise and wideband SIS mixers for the 275–500-GHz radio-frequency (RF) band, aiming to cover Atacama Large Millimeter/submillimeter Array band 7 (275–373 GHz) and band 8 (385–500 GHz) simultaneously. The waveguide SIS mixers integrate a multisection impedance transformer with a parallel-connected-twin-junction or single-junction circuits based on Nb/AlN/Nb trilayers with a critical current density of 31 kA/cm2. In order to achieve the targeted broadband performance, we designed an asymmetric one-side waveguide probe placed across a reduced height waveguide with dimensions 100 μm × 580 μm. The shape of the waveguide probe was optimized to have nearly constant impedance at around 35 Ω in the desired RF range. For evaluation of the receiver performance, we have established a dual-band noise temperature measurement system. The system implements a broadband corrugated horn antenna and a 15-dB RF/local oscillator (LO) waveguide coupler based on WR-2.3 (290 μm × 580 μm) waveguide size. The target bandwidth is too wide for typical LO sources at these high frequencies, and, therefore, we applied a dual-band LO injection system utilizing two different LO sources and an LO diplexer. The IF chain uses a cryogenic isolator and a low-noise amplifier with a typical noise temperature of 2.1 K over the 4–8-GHz range. The measured double sideband receiver noise temperature is two to three times the quantum noise at all LO frequencies for both the twin-junction and the single-junction circuits.

Outcomes from stereotactic surgery for essential tremor

There are several different surgical procedures that are used to treat essential tremor (ET), including deep brain stimulation (DBS) and thalamotomy procedures with radiofrequency (RF), radiosurgery (RS) and most recently,...

Low loading carbon nanotubes supported polypyrrole nano metacomposites with tailorable negative permittivity in radio frequency range

Abstract Metacomposites with conductive polymer matrix toward negative permittivity have promising applications in energy storage devices and electromagnetic shielding. In this paper, carbon nanotubes (CNTs)/polypyrrole (PPy) nanocomposites with different loadings of CNTs have been synthesized using a surface-initiated polymerization (SIP) method. Scanning electron microscopy (SEM) results indicate that conductive networks have constructed inside the nanocomposites by CNTs and PPy granules. A frequency switch of permittivity from positive to negative in pure PPy and CNTs/PPy nanocomposites with low CNTs loading (1 wt%) is observed, which can be analyzed by the Lorentz model. Besides, all negative permittivity behavior in the test frequency range (10–1000 MHz) is found in CNTs/PPy nanocomposites with higher CNTs content which can be easily tuned by adjusting the CNTs loading. Negative permittivity is considered arising from the plasma oscillation of delocalized electrons in conductive networks and could be fitted by Drude model. Furthermore, the equivalent circuit models, ac conductivity and dielectric loss are discussed.

The dispersion-brightness relation for fast radio bursts from a wide-field survey.

Despite considerable efforts over the past decade, only 34 fast radio bursts-intense bursts of radio emission from beyond our Galaxy-have been reported1,2. Attempts to understand the population as a whole have been hindered by the highly heterogeneous nature of the searches, which have been conducted with telescopes of different sensitivities, at a range of radio frequencies, and in environments corrupted by different levels of radio-frequency interference from human activity. Searches have been further complicated by uncertain burst positions and brightnesses-a consequence of the transient nature of the sources and the poor angular resolution of the detecting instruments. The discovery of repeating bursts from one source3, and its subsequent localization4 to a dwarf galaxy at a distance of 3.7 billion light years, confirmed that the population of fast radio bursts is located at cosmological distances. However, the nature of the emission remains elusive. Here we report a well controlled, wide-field radio survey for these bursts. We found 20, none of which repeated during follow-up observations between 185-1,097hours after the initial detections. The sample includes both the nearest and the most energetic bursts detected so far. The survey demonstrates that there is a relationship between burst dispersionand brightness and thatthe high-fluence bursts are the nearby analogues of the more distant events found in higher-sensitivity, narrower-field surveys5.

2.4 to 61 GHz Multiband Double-Directional Propagation Measurements in Indoor Office Environments

This paper presents the details and results of double-directional propagation measurements carried out in two indoor office environments: a semi-open, cubicle-type office space and a more traditional work environment with closed offices. The measurements cover seven frequency bands from 2.4 to 61 GHz, permitting the propagation characteristics to be compared over a wide range of candidate radio frequencies for next-generation mobile wireless systems, including ultra high frequency and millimeter-wave bands. A novel processing algorithm is introduced for the expansion of multiband measurement data into sets of discrete multipath components. Based on the resulting multipath parameter estimates, models are presented for frequency-dependent path loss, shadow fading, copolarization ratio, delay spread, and angular spreads, along with their interfrequency correlations. Our results indicate a remarkably strong consistency in multipath structure over the entire frequency range considered.

Cu2+substituted NiFe2O4 thin films via spray pyrolysis technique and their high-frequency devices application

In the present work, Ni1-xCuxFe2O4 thin films were fabricated with compositions of a wide range (0.0 ≤ x ≤ 1.0 in the steps of 0.2) using the spray pyrolysis technique. The prepared thin films were analyzed by using X-ray diffraction (XRD), Raman spectroscopy, field emission-scanning electronic microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM), contact angle, UV–visible photo spectrometer (UV) and vibrating sample magnetometer (VSM). XRD analysis show, that all thin films possess cubic spinel structure with Fd3¯m space group. The lattice parameter increased from 8.334 to 8.416 Å with increase in Cu2+ content obeying Vegard's law. The average crystallite size was found in the range of 10–21 nm. The formation of spinel ferrite phase is confirmed through active Raman mode of A1g+Eg+3T2g bands in all thin films using Raman spectroscopy. The grain size obtained from FE-SEM analysis was in the range of 16–26 nm. Using AFM images the average roughness; root mean square roughness skewness and kurtosis were calculated. The stoichiometric chemical composition were confirmed by EDAX analysis and it revealed the presence of O −2, Cu2+, Ni2+, and Fe3+ elements with desired atomic weight percentage of the films. The energy band gap (Eg) obtained from UV spectrum varies from 2.24 eV to 2.03 eV as a function of Cu2+. The M-H curves showed that, the saturation magnetization (Ms) linearly decreased and coercivity increases with increase in Cu2+ content which related can be to the large residual strain, which may induce an additional magnetic anisotropy. The specific electrical resistivity confirmed a good insulating character of the thin films. The dielectric constant decreased with increase in frequency. The present ferrite films can be well suitable for MLCIs operable in the radio frequency range and high frequency device application.

Tunable and weakly negative permittivity at radio frequency range based on titanium nitride/polyethylene terephthalate composites

Metacomposites have been induced widespread concern in the realization of negative permittivity. In this paper, composites with titanium nitride (TiN) particles homogeneously dispersed in polyethylene terephthalate (PET) resin were prepared by high energy ball-milling and adhesive hot-pressing method. The influences of TiN networks in composites on the electric and dielectric properties were investigated in detail. With the formation of conductive TiN networks, the conductance mechanism changed from hopping conduction to metal-like conduction. The tunable and weakly negative permittivity in the radio frequency range was obtained in TiN/PET composites by adjusting the frequency range and volume fraction (v) of TiN in composites. Negative permittivity behavior raises from the low-frequency plasma oscillation of free electrons in TiN networks, which could be analyzed by the Drude model. The impedance of TiN/PET composites were investigated by the equivalent circuit analysis, demonstrating the capacitive or inductive of the composites. This paper shows an effective way toward the tunable and weakly negative permittivity, which will promote practical applications of metacomposites in electromagnetic shielding and impedance matching fields.

Dielectrical and structural studies of composite matrix BiVO4–CaTiO3 and temperature effects by impedance spectroscopy

In this work, we have analysed the effects of adding CaTiO3 (CTO) and changing the temperature on the dielectric and electric properties of ceramic matrix BiVO4 (BVO) in the radiofrequency range. BVO was synthesized by a calcination process at 500 °C and ceramic composites were prepared by the addition of CTO (8, 16, 24, 28 and 32 wt%). These composites were moulded in ceramic pellets and sintered at 800 °C. The crystal structures of BVO and composites were analysed by X-ray diffraction and no spurious phase was detected in the synthesized BVO. Complex impedance spectroscopy observed the presence of a thermo-activated charge transfer process with activation energy increasing with CTO concentration in the samples. The dielectric constant (e) measured in radio frequency for ceramic composites presented high values that ranged from 26 to 9 k for BVO to BV32, respectively, at room temperature and a frequency of 1 Hz. The electrical response obtained by composites were fitted through an equivalent circuit composed of three associations in parallel with the resistance of a constant phase element, which showed minor deviations between the fitted and experimental data. The temperature coefficient of capacitance displayed negative and positive values in CTO-based composites and pure BVO, respectively; these characteristics are favourable for the application of composites in the radio frequency band.

Electromagnetic properties of the Great Pyramid: First multipole resonances and energy concentration

Resonant response of the Great Pyramid interacting with external electromagnetic waves of the radio frequency range (the wavelength range is 200–600 m) is theoretically investigated. With the help of numerical simulations and multipole decomposition, it is found that spectra of the extinction and scattering cross sections include resonant features associated with excitation of the Pyramid's electromagnetic dipole and quadrupole moments. Electromagnetic field distributions inside the Pyramid at the resonant conditions are demonstrated and discussed for two cases, when the Pyramid is located in a homogeneous space or on a substrate. It is revealed that the Pyramid's chambers can collect and concentrate electromagnetic energy for the both surrounding conditions. In the case of the Pyramid on the substrate, at the shorter wavelengths, the electromagnetic energy accumulates in the chambers providing local spectral maxima for electric and magnetic fields. It is shown that basically the Pyramid scatters the electromagnetic waves and focuses them into the substrate region. The spectral dependence of the focusing effect is discussed.

Avaliação e Gerenciamento de Riscos dos Campos Eletromagnéticos em Plataforma de Petróleo

Os equipamentos de telecomunicações operam na faixa de radiofrequência do espectro eletromagnético, portanto são considerados emissores de radiações não ionizantes (RNI). A exposição a campos eletromagnéticos pode causar impactos à saúde e ao meio ambiente. A pesquisa de campo revelou que na plataforma de petróleo avaliada as exposições a RNI encontram-se abaixo dos limites estabelecidos pela legislação. No entanto, os estudos que estabelecem tais limites não são conclusivos o suficiente para garantir ausência de malefícios tanto para o homem, quanto para o meio ambiente considerando os atuais valores de referência.

RF and Microwave Electrical Properties Study of the Magneto-Dielectric Resonator Antenna of the Matrix Composite [SrFe12O19 (SFO)1−x-BiFeO3(BFO)x

In this work, we prepared ceramic composites based on SrFe12O19 (SFO)-BiFeO3 (BFO) strontium hexaferrite. The SFO and BFO were synthesized by the solid-state reaction method, and we used both x-ray diffraction and infrared spectroscopy for structural characterization of the composite matrix. The electrical and dielectric properties were measured in the radiofrequency range by using Impedance Spectroscopy, and the Nyquist plots were fitted by equivalent circuits. For the microwave range, we used the Hakki–Coleman method, and we also studied the thermal stability of the composite. The resonator cylinders were fabricated using a mixture of SFO and BFO, with BFO concentrations of 20 wt.%, 40 wt.% and 60 wt.%, named SB20, SB40 and SB60, respectively. The insertion of BFO improved the thermal stability of the material and the composite permittivity. These composites were tested as dielectric resonator antenna, which presented reflection coefficients below − 10 dB, gain above 4.9 dBi and efficiency above 67%.

Constraining the halo size from possible density profiles of hydrogen gas of Milky Way Galaxy

Galactic magnetic field (GMF) and secondary cosmic rays (CRs) (e.g. 10beryllium, boron, antiproton) are important components to understand the propagation of CRs in the Milky Way Galaxy. Realistic modeling of GMF is based on the Faraday rotation measurements of various Galactic and extragalactic radio sources and synchrotron emission from CR leptons in the radio frequency range, thereby providing information of halo height. On the other hand, diffusion coefficient and halo height are also estimated from the 10Be/9Be and B/C ratios. Moreover, density distribution of gaseous components of interstellar medium (ISM) also plays an important role as secondary CRs are produced due to interaction of primary CRs with the gaseous components of ISM . We consider mainly molecular, atomic, and ionized components of hydrogen gas for our study. Recent observations and hydrodynamical simulations provide new forms of density profiles of hydrogen gas in Milky Way Galaxy. In the DRAGON code, we have implemented our chosen density profiles, based on realistic observations in radio, X-ray and γ-ray wavebands, and hydrodynamical simulations of interstellar hydrogen gas to study the variation in the height of the halo required to fit the observed CR spectra. Our results show the halo height (zt) varies in the range of 2 to 6 kpc for the density profiles considered in our work.

Numerical analysis of thermal deformation for constructive variants of mirror segments in a parabolic antenna

This work is devoted to the research of thermal deformation of segments in a parabolic reflector mirror in connection with the limitations determined by the radio frequency range of antenna operation. The thermal deformation analysis is performed based on the results of a numerical solution of the coupled problem of stationary thermal conductivity under conditions of radiation-convective heat transfer and thermoelasticity. A comparative analysis of five form factors of mirror segments was performed, which allowed choosing its preferred configuration.

Fault Detection Methods for Three-Level NPC Inverter Based on DC-Bus Electromagnetic Signatures

This paper proposes two new open-circuit fault detection methods suitable for the diagnosis of power electronics converters. The faulty semiconductor devices are identified using conducted and radiated electromagnetic signatures of the dc bus through nonintrusive measurements. The first method uses a low-cost electromagnetic interference filter to collect the common-mode emissions signature. The second one utilizes an external antenna to collect the emitted near-field signature. Both methods are tested on a three-level neutral point clamped inverter (NPC) inverter with the aim to identify the clamping diodes open-circuit faults. Indeed, each open-circuit fault affects the common-mode emission signature in the time-domain, while the fast Fourier transform of the emitted near-field showed substantial reduction of spectrum amplitude at a specific radio frequency range and the appearance of a new spectral rail. The effectiveness of these two methods has been tested through numerical simulations and validated by experimental results which confirmed its high performance in detecting single as well as multiple open-circuit faults for three-level NPC inverter.

Studies on the Dynamics of Two Mutually Coupled Colpitts Oscillators

In this paper, we have thoroughly examined the dynamics of a system of two mutually coupled Colpitts oscillators. Two bias-tuned Colpitts oscillators with identical structure are bilaterally coupled through direct coupling scheme.Numerically solving the system equations, it is observed that both the Colpitts oscillators oscillating in periodic mode become perfectly synchronized for some values of the coupling factors. For higher values of coupling factors, the system become chaotic.We have also studied the dynamics of two mutually coupled non-oscillatory Colpitts oscillators. With the increase of the coupling factors between two oscillators, birth of periodic oscillation observed. For increased value of coupling factors, system dynamics become chaotic.We develop conditions for periodic bifurcation in parameter space analytically and verified it through numerical solution of system equations. We also perform a simulation experiment using PSPICE circuit simulator in the radio frequency range with prototype Colpitts oscillator circuits and the experimental observations are in agreement with the numerical simulation results.

Innovative photonic system in radiofrequency and microwave range to determine chicken meat quality

Nowadays, one of the most important challenges of poultry industry is to determine individually the meat quality class (pale, soft and exudative, normal and dark, firm and dry meats) by non-invasive, accurate and fast technique. For this purpose, dielectric spectra in radiofrequency and microwave ranges were studied. In radiofrequency range, the permittivity was measured by a non-destructive sensor conformed by three points with blunt-ended electrodes connected to an Agilent 4294A impedance analyser, and in microwave range an Agilent 85070E open-ended coaxial probe connected to an Agilent E8362B Vector Network Analyser were used. This work demonstrates the direct relation between the pH evolution and the dielectric constant at α-dispersion, and also, that the main structural proteins degradation has direct relation with the dielectric constant at β-dispersion, being possible to segregate meat depending on the level of protein degradation. Finally, this paper ends with a classification model for quality poultry meat based on a photonic analysis at radiofrequency range by using the Traffano-Schiffo model.