GHz

Distribution by Scientific Domains

Terms modified by GHz

  • ghz band
  • ghz frequency
  • ghz frequency band

  • Selected Abstracts


    Temperature Dependence of the Dielectric Properties and Dynamics of Ionic Liquids

    CHEMPHYSCHEM, Issue 4 2009
    Johannes Hunger
    Abstract No solo dancers: The temperature dependence of dielectric spectra suggests that the lower-frequency relaxation dominating the dynamics of imidazolium-based room temperature ionic liquids cannot be solely due to independent rotational diffusion of the cations (see picture), but must also include cooperative motions of the surrounding particles. Dielectric spectra were measured for eight, mostly imidazolium-based, room temperature ionic liquids (RTILs) over a wide range of frequencies (0.2,,/GHz,89) and temperatures (5,,/C, 65). Detailed analysis of the spectra shows that the dominant low frequency process centred at ca. 0.06 to 10 GHz (depending on the salt and the temperature) is better described using a symmetrically broadened Cole,Cole model rather than the asymmetric Cole,Davidson models used previously. Evaluation of the temperature dependence of the static permittivities, effective dipole moments, volumes of rotation, activation energies, and relaxation times derived from the dielectric data indicates that the low frequency process cannot be solely due to rotational diffusion of the dipolar imidazolium cations, as has been thought, but must also include other contributions, probably from cooperative motions. Analysis of the Debye process observed at higher frequencies for these RTILs is not undertaken because it overlaps with even faster processes that lie outside the range of the present instrumentation. [source]


    Generation of three-qubit entangled states using coupled multi-quantum dots

    LASER PHYSICS LETTERS, Issue 5 2007
    M. Abdel-Aty
    Abstract We discuss a mechanism for generating a maximum entangled state (Greenberger,Horne,Zeilinger (GHZ)) in a coupled quantum dots system, based on analytical techniques. The reliable generation of such states is crucial for implementing solid-state based quantum information schemes. The signature originates from a remarkably weak field pulse or a far offresonance effects which could be implemented using technology that is currently being developed. The results are illustrated with an application to a specific wide-gap semiconductor quantum dots system, like Zinc Selenide (ZnSe) based quantum dots. ( 2007 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source]


    Spin-lattice relaxation of spin- nuclei in solids containing diluted paramagnetic impurity centers.

    CONCEPTS IN MAGNETIC RESONANCE, Issue 1 2003

    Abstract Dynamic nuclear polarization of nuclei by means of paramagnetic electron spin locking (Hartmann-Hahn cross-polarization between paramagnetic electrons and nuclei, or NOVEL) is discussed. The theory is demonstrated by experiments executed at 2.4 and 9.6 GHz on a natural type Ib diamond. It is shown that the 13C polarization rate is independent of the microwave frequency, in agreement with theory. NOVEL polarization takes place only while the spin-locking pulse is on. The rate at which the nuclei are polarized is proportional to the electron polarization in the rotating frame. Therefore, the length of the spin-locking pulse is limited by the value of T1,(e), and because T1,(e) , T1(e) for diamond the effective NOVEL polarization rate of 13C nuclei is usually relatively low. A comparison between the relative effectiveness of 13C polarization rates between NOVEL and the solid-state effect is made for high and low paramagnetic impurity concentrations. The dependence of the 13C polarization rate on the paramagnetic impurity concentration has been determined for a suite of natural diamonds. 2003 Wiley Periodicals, Inc. Concepts Magn Reson 19A: 44,49, 2003. [source]


    Experimental Study and Modelling of Formation and Decay of Active Species in an Oxygen Discharge

    CONTRIBUTIONS TO PLASMA PHYSICS, Issue 1 2005
    A.-M. Diamy
    Abstract A microwave (2.45 GHz) oxygen discharge (3 hPa, 150 W, 50 mL.min,1) is studied by optical emission spectroscopy of O(5P) (line 777.4 nm) and of the atmospheric system of O2(head-line 759.4 nm). Calibration of the spectral response of the optical setup is used to determine the concentrations of O(5P) and O2(b). The concentration of the O(5P) atoms is in the range 108,109 cm,3 and the concentration of the O2(b) molecules is in the range 1014 , 2 1014 cm,3 along the discharge tube. An attempt is made to simulate the experimental results by using coupling the Boltzmann equation, homogeneous energy transfer V-V and V-T, heterogeneous reactions on the walls (energy transfer and recombination of atoms) and a kinetic scheme (electronic transfer and chemical reactions). The Boltzmann equation includes momentum transfer, inelastic and superelastic processes and e-e collisions. V-V and V-T transfer equations are obtained from the SSH theory and the kinetic scheme includes 65 reactions with 17 species [electrons e, ions O, and O2,, fundamental electronic neutral species O(3P), O2, O2(X,v), O3 and excited neutral species O2(a), O2(b), O2(A), O(1D), O(1S), O(5P), O(4d 5Do), O(5s 5So), O(3d 5Do) and O(4s 5So)]. A fair agreement between experimental results and modelling is obtained with the following set of fitting values: , heterogeneous deactivation coefficient for O2(b) , = 2.6 10,2; , rate constant of reaction [O(1D) + O(3P) , 2 O(3P)] k34 = 1.4 10,11 cm3.s,1; , electron concentration in the range 1010 , 1011 cm,3. Modelling shows that the recombination coefficient for oxygen atoms on the silica wall (range 1.4 10,3 , 0.2 10,3) is of the same order as the values obtained in a previous paper and that the ratio ([O] / 2 [O2]initial) is about 33,50%. ( 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Suppression of electromagnetic radiation noise from wireless modules in the millimeter-wave band by means of alumina containing carbon black

    ELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 10 2010
    Yasuharu Takase
    Abstract Unwanted electromagnetic (EM) radiation generated from wireless modules in the millimeter-wave band used for car radar creates errors and results in performance degradation of electronic equipment. In this paper, to reduce these unwanted EM waves, an optimal design to add the function of EM wave absorption to the lid for the module is examined. Alumina-containing carbon black is used as a wave absorption material for the lid. Absorption of 20 dB or more is obtained as a measured result with the cover added for EM wave absorption at 60 GHz. The wireless module was also analyzed in the millimeter-wave band with the designed material used for the lid. The radiation and the reflection of electric power were greatly reduced by the loss electric power from the lid. Therefore, effective data for suppressing unwanted EM radiation noise from wireless modules in the millimeter-wave band can be provided. 2010 Wiley Periodicals, Inc. Electron Comm Jpn, 93(10): 25,33, 2010; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ecj.10216 3 [source]


    Understanding the partial discharge activity of conducting particles in GIS under DC voltages using the UHF technique

    EUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 5 2010
    R. Sarathi
    Abstract The major cause of failure of DC-GIS is due to presence of foreign particles causing partial discharges in the insulation structure. The particle movement in gas insulated system (GIS) radiates electromagnetic waves and the bandwidth of the signal lies in the range 1,2,GHz. Increase in applied DC voltage/pressure has not altered the frequency content of the ultra high frequency (UHF) signal generated due to partial discharge formed by particle movement. The UHF sensor could recognize the breakdown of sulfur-hexa-fluoride (SF6) gas under DC and Lightning impulse voltages and the frequency content of the signal captured by the UHF sensor lies up to 500,MHz. Mounting UHF sensor in GIS could allow one to classify internal partial discharges from breakdown, at the time of testing/during operation. Copyright 2009 John Wiley & Sons, Ltd. [source]


    High-resolution estimation for time-variant MIMO channel sounding,

    EUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 7 2008
    Sofia Martinez Lopez
    A wideband vector channel sounder with 16 parallel RF chains is proposed for parameter estimation in an indoor channel. Low-cost and high-resolution are obtained by using a chirp probe signal, five-port receivers and the MUSIC algorithm. The system covers up to 500,MHz centred at 2.45,GHz. Experimental results show errors inferior to 1,ns in the time domain and of few degrees in the angular domain. Accurate results are found in static as well as in time-variant scenarios. Copyright 2008 John Wiley & Sons, Ltd. [source]


    A Multiscale Description of the Electronic Transport within the Hierarchical Architecture of a Composite Electrode for Lithium Batteries

    ADVANCED FUNCTIONAL MATERIALS, Issue 17 2009
    Jean-Claude Badot
    Abstract The broadband dielectric spectroscopy technique is applied, for the first time, to a composite material used as an electrode for lithium battery. The electrical properties (permittivity and conductivity) are measured from low (a few Hz) to microwave (a few GHz) frequencies. The results demonstrate that the broadband dielectric spectroscopy technique is very sensitive to the different scales of the electrode architecture involved in electronic transport, from interatomic distances to macroscopic sizes, as well as to the morphology at these scales, coarse or fine distribution of the constituents. This work opens up new prospects for a more fundamental understanding and more rational optimization of the electronic transport in composite electrodes for lithium batteries and other electrochemical energy storage technologies (including other batteries, supercapacitors, low- and medium-temperature fuel cells), electrochemical sensors and conductor,insulator composite materials. [source]


    An electromagnetic modelling tool for the detection of hydrocarbons in the subsoil

    GEOPHYSICAL PROSPECTING, Issue 2 2000
    Carcione
    Electromagnetic geophysical methods, such as ground-penetrating radar (GPR), have proved to be optimal tools for detecting and mapping near-surface contaminants. GPR has the capability of mapping the location of hydrocarbon pools on the basis of contrasts in the effective permittivity and conductivity of the subsoil. At radar frequencies (50 MHz to 1 GHz), hydrocarbons have a relative permittivity ranging from 2 to 30, compared with a permittivity for water of 80. Moreover, their conductivity ranges from zero to 10 mS/m, against values of 200 mS/m and more for salt water. These differences indicate that water/hydrocarbon interfaces in a porous medium are electromagnetically ,visible'. In order to quantify the hydrocarbon saturation we developed a model for the electromagnetic properties of a subsoil composed of sand and clay/silt, and partially saturated with air, water and hydrocarbon. A self-similar theory is used for the sandy component and a transversely isotropic constitutive equation for the shaly component, which is assumed to possess a laminated structure. The model is first verified with experimental data and then used to obtain the properties of soils partially saturated with methanol and aviation gasoline. Finally, a GPR forward-modelling method computes the radargrams of a typical hydrocarbon spill, illustrating the sensitivity of the technique to the type of pore-fluid. The model and the simulation algorithm provide an interpretation methodology to distinguish different pore-fluids and to quantify their degree of saturation. [source]


    Numerical analysis of microwave heating of a dielectric

    HEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 3 2003
    Yuichi Funawatashi
    Abstract Microwave heating of a dielectric in a cavity was analyzed numerically with the FDTD method with the aim of devising new methods for reducing uneven heating typical of microwaving. The dielectric was assumed to be water and the frequency of a microwave was taken to be 1 GHz. It was found that the electric field is highly dependent on the position of the dielectric in a cavity. The temperature distribution reflects the profile of the RMS value of the electric field in the dielectric, although there appears to be no effect of the short wavelength typical of the electric field. The heating rate depends on the position of the dielectric. In the case of a higher effective loss factor a microwave decays immediately after entering the dielectric, and the temperature of the interior remains low. These results indicate that the uneven heating is due to at least two causes: standing wave and rapid decay of a microwave. 2003 Wiley Periodicals, Inc. Heat Trans Asian Res, 32(3): 227,236, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.10087 [source]


    Giant Electric Field Tuning of Magnetism in Novel Multiferroic FeGaB/Lead Zinc Niobate,Lead Titanate (PZN-PT) Heterostructures

    ADVANCED MATERIALS, Issue 46 2009
    Jing Lou
    A novel multiferroic heterostructure consisting of a FeGaB thin film and a PZN-PT single crystal slab shows giant tunability of the ferromagnetic resonance (FMR) frequency of the heterostructure by electric field (see figure). The overall electric-field-induced FMR frequency change of 5.82 GHz is the largest reported so far. FeGaB/PZN-PT multiferroic heterostructures are promising candidates for wide-band electrostatically tunable microwave devices. [source]


    Measurement of atmospheric water vapour on the ground's surface by radio waves

    HYDROLOGICAL PROCESSES, Issue 11 2001
    Tokuo Kishii
    Abstract Water vapour in the atmosphere and various meteorological phenomena are essential to the understanding of the mechanism of the water cycle. However, it is very difficult to observe water vapour in the atmosphere because the quantities are usually observed at a single point not over long intervals or in a specific plane or volume. Accordingly, the use of radio waves is considered to be necessary to observe water vapour. Radio waves can be transmitted over long intervals and across large areas, and generally speaking, the characteristics of radio waves change due to material in the atmosphere, especially water vapour. Usually absorption is used to observe the quantity of water vapour. But the relationship between absorption and the quantity of water vapour is not linear, so we try to utilize the phase difference between two radio waves as an alternative method. First, the relationship between the phase delay and the water vapour was induced by a physical equation and the resulting phase delay was found to be proportional to the quantity of water vapour. Furthermore, the phase difference between two separate points was observed by use of two radio waves in the field, specifically 84 GHz and 245 GHz. For reference and comparison, water vapour density in the atmosphere was simultaneously observed by meteorological observation. As a result, the density of the water vapour was found to be proportional to the phase difference between the two radio waves. The result also shows that this method is able to measure the diurnal changes in water vapour density in each season. Copyright 2001 John Wiley & Sons, Ltd. [source]


    Influence of water absorption on high-frequency characteristics of insulation layers of printed circuit boards

    IEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 6 2007
    Kaori Fukunaga Member
    Abstract The influence of water absorption on complex permittivities of various insulating materials used for printed circuit boards was investigated in the frequency range of K-band (18,26 GHz). Experimental results revealed that the influence of water absorption on complex permittivity, the dielectric loss factor tan,, in particular, was considerably high. For example, the dielectric loss of polyimide film at 85C, 85% RH became 10 times larger than that at room temperature and humidity. Since the complex permittivities, however, retained the initial values when the specimens are dried, the water in the specimen should exist freely at the internal interfaces of the materials. The increase of permittivity directly affects the performance of printed circuit boards at high frequencies, so that it is important to clarify the influence of water on dielectric properties of insulations. Copyright 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source]


    Microwave Dielectric Properties of SrO,2CeO2,nTiO2 (n=4 and 5) Ceramics

    INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 2010
    Ramachandran Satheesh
    SrO,2CeO2,nTiO2 ceramics with n=4 and 5 have been prepared through conventional solid-state ceramic route. Structural and microstructural characterizations of the sintered ceramics were carried out using X-ray diffraction, laser Raman, and scanning electron microscopic studies. Microwave dielectric properties have been measured using postresonator and resonant cavity techniques. SrO,2CeO2,4TiO2 and SrO,2CeO2,5TiO2 ceramics showed dielectric constants of 71.3 and 71.7, respectively, around 4 GHz together with a relatively high unloaded quality factor. [source]


    Effect of A-Site Ionic Radius on the Structure and Microwave Dielectric Characteristics of Sr1+xSm1,xAl1,xTixO4 Ceramics

    INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 2010
    Min Min Mao
    SrSmAlO4 microwave dielectric ceramics were modified by Sr/Ti cosubstitution for Sm/Al. The effects of radius difference of A-site ions on the microwave dielectric characteristics were investigated together with the structure. Sr1+xSm1,xAl1,xTixO4 (x=0, 0.05, 0.10, and 0.15) ceramics were prepared by a solid-state reaction approach. X-ray diffraction studies revealed a single-phase K2NiF4 -type solid solution with corresponding peaks shifting to lower 2, as x increased. Minor inhomogeneous grain morphology for x=0.05 and a trace amount of second phases for x=0.10, 0.15 were detected by backscattered-electron microscopy and energy-dispersive X-ray analysis. With increasing Sr/Ti cosubstitution, the dielectric constant ,r increased from 18.4 to 20.4, and the temperature coefficient of resonant frequency ,f was adjusted from ,1.8 to 7.4 ppm/C almost linearly. However, the Qf value decreased from 74,500 GHz at x=0,53,000 GHz at x=0.15. The internal stresses caused by the decreased tolerance factor and the large ionic radii difference between Sr2+ and Sm3+ should be the predominant reasons for such a decrease in the Qf value. The high-resolution transmission electron microscopic results revealed an increase in the lattice distortion with increasing Sr/Ti cosubstitution, and subsequently supported the above conclusion upon the increased internal stresses. [source]


    A Novel Temperature-Compensated Microwave Dielectric (1,x)(Mg0.95Ni0.05)TiO3,xCa0.6La0.8/3TiO3 Ceramics System

    INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 5 2009
    Chun-Hsu Shen
    The microstructure and microwave dielectric properties of a (1,x)(Mg0.95Ni0.05)TiO3,xCa0.6La0.8/3TiO3 ceramics system have been investigated. The system was prepared using a conventional solid-state ceramic route. In order to produce a temperature-stable material, Ca0.6La0.8/3TiO3 was added for a near-zero temperature coefficient (,f). With partial replacement of Mg2+ by Ni2+, the dielectric properties of the (1,x)(Mg0.95Ni0.05)TiO3,xCa0.6La0.8/3TiO3 ceramics can be promoted. The microwave dielectric properties are strongly correlated with the sintering temperature and the composition. An excellent Q f value of 118,000 GHz can be obtained for the system with x=0.9 at 1325C. For practical application, a dielectric constant (,r) of 24.61, a Q f value of 102,000 GHz, and a temperature coefficient of resonant frequency (,f) of ,3.6 ppm/C for 0.85(Mg0.95Ni0.05)TiO3,0.15Ca0.6La0.8/3TiO3 at 1325C are proposed. A parallel-coupled line band-pass filter is designed and simulated using the proposed dielectric to study its performance. [source]


    The Effect of Dopants on the Dielectric Properties of Ba(B,1/2Ta1/2)O3 (B,=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Y, Yb, and In) Microwave Ceramics

    INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 5 2009
    Lamrat Abdul Khalam
    Low-loss dielectric ceramics based on Ba(B,1/2Ta1/2)O3 (B,=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Y, Yb, and In) complex perovskites have been prepared by the solid-state ceramic route. The dielectric properties (,r, Qu, and ,f) of the ceramics have been measured in the frequency range 4,6 GHz by the resonance method. The resonators have a relatively high dielectric constant and high quality factor. Most of the compounds have a low coefficient of temperature variation of the resonant frequencies. The microwave dielectric properties have been improved by the addition of dopants and by solid solution formation. The solid solution Ba[(Y1,xPrx)1/2Ta1/2]O3 has x=0.15, with ,r=33.2, Quf=51,500 GHz, and ,f,0. The microwave dielectric properties of Ba(B,1/2Ta1/2)O3 ceramics are found to depend on the tolerance factor (t), ionic radius, and ionization energy. [source]


    A Chemical Route to BiNbO4 Ceramics

    INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 2 2009
    Oleg A. Shlyakhtin
    The liquid phase sintering of fine BiNbO4 powders allows to obtain dense ceramics with excellent microwave dielectric properties (,=44,46; Qf=16,500,21,600 GHz) at T,700C. The thermal decomposition of freeze-dried precursors results in the crystallization of a metastable ,,-BiNbO4 polymorph that transforms into a stable orthorhombic ,-modification at T,700C. The dependence of sinterability on the powder synthesis temperature shows the maximum at 600C, corresponding to the formation of crystalline BiNbO4 powders with a grain size 80,100 nm. Sintering temperature reduction to 700C prevents the deterioration of silver contacts during co-firing with BiNbO4 ceramics. In situ scanning electron microscopy observation of the morphological evolution during sintering shows that the intense shrinkage soon after the appearance of a CuO,V2O5 eutectics-based liquid phase is accompanied by complete transformation of the ensemble of primary BiNbO4 particles. [source]


    Phase Transformation and Densification Behavior of Microwave-Sintered Si3N4,Y2O3,MgO,ZrO2 System

    INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 1 2009
    Sreekumar Chockalingam
    A 2.45 GHz microwave-sintered Si3N4,Y2O3,MgO system containing various amounts of ZrO2 secondary additives have been studied with respect to phase transformation and densification behavior. The temperature dependent dielectric properties were measured from 25C to 1400C using a conventional cavity perturbation technique. Phase transformation behavior was studied using X-ray diffractometry. Microwave sintered results were compared with those of conventional sintered results. It has been found that , to , phase transformation was completed at a lower temperature in microwave-sintered samples than those of the conventionally sintered samples. Density of the microwave-sintered samples increased up to 2.5 wt% of ZrO2 addition and thereafter it showed a tendency to decrease or remain constant. The decrease in density is attributed to the pore generation caused by decomposition due to the localized over heating. [source]


    Study of Cation Ordering in Ba(Yb1/2Ta1/2)O3 by X-Ray Diffraction and Raman Spectroscopy

    INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 5 2008
    Dibyaranjan Rout
    The complex perovskite Ba(Yb1/2Ta1/2)O3 has been prepared by the two-stage solid-state reaction method. Rietveld' refinement analysis indicates cubic perovskite phase with space group . The 1:1 cation ordering at the B-site is revealed by the presence of (111) superlattice reflection in the X-ray diffraction pattern and further evidenced by the presence of A1g and F2g vibrational modes in the Raman spectra. The dielectric constant is measured to be 29.1, the product of quality factor and resonant frequency (Qf) is found to be 32,000 GHz and the temperature coefficient of resonant frequency (,f) is 135 (ppm/C) in the temperature range 30,70C. [source]


    Effect of Bismuth Borate/LiF on the Sintering, Thermal, and Microwave Dielectric Properties of Ba6,3xSm8+2xTi18O54 (x=2/3) Solid Solution

    INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 4 2008
    Narayana Iyer Santha
    Ba6,3xSm8+2xTi18O54 (x=2/3) (BST) was prepared by the solid-state method and the effect of bismuth borate (BB)/LiF on the sinterability, microstructure, and thermal and microwave dielectric properties were studied. BST+3.5 wt% BB+0.5 wt% LiF composite sintered at 1050C has Qf=4500 GHz, ,=52, and ,f=+6 ppm/C. Raman spectrum of the composite was compared with that of BST and the structural changes were investigated. [source]


    Low-Temperature Firing and Microwave Dielectric Properties of Ca[(Li1/3Nb2/3)0.8Ti0.2]O3,, Ceramics with ZnB2O4 Glass Addition

    INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 4 2008
    Li-Xia Pang
    Low-temperature sintered Ca[(Li1/3Nb2/3)0.8Ti0.2]O3,, microwave dielectric ceramics with ZnB2O4 glass (ZBG) addition were prepared by the conventional solid state reaction method. The sintering behavior, microstructure, and microwave dielectric properties of Ca[(Li1/3Nb2/3)0.8Ti0.2]O3,, ceramics with ZBG addition were investigated. The ZBG addition lowered the densified temperature of Ca[(Li1/3Nb2/3)0.8Ti0.2]O3,, ceramics from 1150C to 940C. The dielectric constants of Ca[(Li1/3Nb2/3)0.8Ti0.2]O3,, ceramics decreased from 40 to 34 and the temperature coefficient of resonant frequency (,f) changed gradually from +12.7 to ,25.7 ppm/C as ZBG addition increased from 0 to 8 wt%. The Qf values increased greatly from 20,500 GHz of pure Ca[(Li1/3Nb2/3)0.8Ti0.2]O3,, to 26,900 GHz when 5 wt% ZBG was added. Ca[(Li1/3Nb2/3)0.8Ti0.2]O3,, ceramics with 8 wt% ZBG addition sintered at 940C show good microwave dielectric properties with ,r,32.5, Qf,20,600 GHz, and ,f,,25.7 ppm/C. The relationship between dielectric properties and microstructure was also discussed. [source]


    LC-active VCO for CMOS RF transceivers

    INTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS, Issue 1 2010
    Domenico Zito
    Abstract A novel fully integrated CMOS LC tank VCO is presented. The LC tanks are implemented by exploiting the active circuit ,boot-strapped inductor' (BSI), which behaves like a high-quality factor inductor. Particularly, the LC tanks have been implemented by introducing a new version of the CMOS BSI circuit, which provides better versatility and design reliability. In order to verify the effectiveness of such an approach, a case study for 5,6,GHz direct-conversion multi-standard WLAN transceivers is presented. The VCO has been designed in a 0.35m standard CMOS technology. The new BSI exhibits a high-quality factor (higher than 25 over the all frequency range) and provides a high selectivity without introducing a relevant excess of noise, for a better spectral purity and a lower phase noise (PN) of the VCO. The overall VCO circuit consumes 9,mW. The VCO produces an oscillation in the tuning range from 4.91 to 5.93,GHz (nearly equal to 19%). The circuit exhibits a PN of ,129dBc/Hz at 1,MHz of frequency offset from the central frequency (5.4,GHz) and a FOM equal to 189.5,dBc/Hz at 100,kHz and 194.1,dBc/Hz at 1,MHz of frequency offset, respectively. Copyright 2009 John Wiley & Sons, Ltd. [source]


    The electromagnetic effect of cooling fins

    INTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 4 2006
    S. B. Chiu
    Abstract The electromagnetic effect of cooling fins is studied by solving Maxwell equations numerically using a FDTD method under high-frequency operating conditions. The fin is attached to a square IC chip to form a package. The overall size of the package is 25 mm 25 mm 17.5 mm. A smooth compact pulse with a reference frequency of either 1 or 2.5 GHz is used as the excitation source of EM waves. Six fin configurations are investigated. Computational results indicate that a fin can act as an antenna. For the present type of excitation source, resonance could occur roughly at frequencies of 2.5, 5 and 7.5 GHz, depending on the source reference frequency and fin geometries. Thus, fin effects should be considered in the electrical design phase since noises could be induced in the circuit due to the presence of fins. Copyright 2006 John Wiley & Sons, Ltd. [source]


    Accurate substrate modelling of RF CMOS

    INTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 3 2006
    M. S. Alam
    Abstract The losses within the substrate of an RF IC can have significant effect on performance in a mixed signal application. In order to model substrate coupling accurately, it is represented by an RC network to account for both resistive and dielectric losses at high frequency (> 1 GHz). A small-signal equivalent circuit model of an RF IC inclusive of substrate parasitic effect is analysed in terms of its y -parameters and an extraction procedure for substrate parameters has been developed. By coupling the extracted substrate parameters along with extrinsic resistances associated with gate, source and drain, a standard BSIM3 model has been extended for RF applications. The new model exhibits a significant improvement in prediction of output reflection coefficient S22 in the frequency range from 1 to 10 GHz in device mode of operation and for a low noise amplifier (LNA) at 2.4 GHz. Copyright 2006 John Wiley & Sons, Ltd. [source]


    Study of parallel numerical methods for semiconductor device simulation

    INTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 1 2006
    Natalia Seoane
    Abstract Simulators of semiconductor devices have to solve systems of equations generated by the discretization of partial differential equations, which are the most time-consuming part of the simulation process. Therefore, the use of an effective method to solve these linear systems is essential. In this work we have evaluated the efficiency of different parallel direct and iterative solvers used for the solution of the drift,diffusion equations in semiconductor device simulation. Several preconditioning techniques have been applied in order to minimize the execution times. We have found that FGMRES and BCGSTAB solvers preconditioned with Additive Schwarz are the most suitable for these types of problems. The results were obtained in an HP Superdome cluster with 128 Itanium2 1.5 GHz. Copyright 2005 John Wiley & Sons, Ltd. [source]


    Active measurements of antenna diversity performances using a specific test-bed, in several environments

    INTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 3 2010
    Moctar Mouhamadou
    Abstract The diversity performances of the wireless devices operating in a multipath propagation environment are usually presented in terms of correlation coefficient, diversity gain and effective diversity gain. These parameters can be measured in reverberation chamber. This paper presents some active measurements of antenna diversity performances on a small wireless terminal in several realistic environments. The measurements were performed in the WiMax band, i.e. at 3.5 GHz, in a reverberation chamber where the channel is statistically uniform, in a real indoor propagation channel, and in an outdoor-to-indoor environment. The diversity performances are evaluated by using a specific test-bed constituted by an arbitrary signal generator and two radio-frequency digitizers. The effectiveness of diversity is presented in terms of effective diversity gain, signal to noise ratio, bit error rate and frame error rate. 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2010. [source]


    Accurate closed-form model for computation of conductor loss of coplanar waveguide

    INTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 1 2010
    Payal Majumdar
    Abstract This study estimates the accuracy of HFSS and Sonnet and other models against the experimental results from three sources. A closed-form model for experiment based stopping distance is developed to calculate accurately conductor loss of CPW. The present improved Holloway and Kuester (IHK) model has an average accuracy of 3.7% against the experimental results from different sources in the frequency range 1,120 GHz with conductor thickness of 0.25,1.58 ,m. The original Holloway and Kuester model has an average accuracy of 13.7% and model of Ponchak et al. 17.1 % against same set of experimental results. HFSS and Sonnet have average accuracy of 7.86% and 10.33% against same set of experimental data. The accuracy of IHK model is also examined against HFSS and Sonnet for the conductor thickness up to 9 ,m and substrate relative permittivity in the range of 3.8,20. 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2010. [source]


    Frequency reconfigurable RF circuits using photoconducting switches

    INTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 1 2010
    D. Draskovic
    Abstract Designs for a frequency switchable dual-band branch-line coupler and a reconfigurable S-band power amplifier input matching network with photoconducting switches are presented. Frequency switching is achieved by increasing the power of the laser applied to the highly resistive silicon wafer and changing the properties of silicon under optical illumination. The advantages of this approach are high-speed switching, electromagnetic transparency (no interference), and thermal and electrical isolation between the device and the control circuit. A branch-line coupler frequency shift of 35% and 10% has been achieved from all switches off to all switches on in lower (900 MHz) and upper (1800 MHz) frequency bands, respectively. Frequency switchable class AB power amplifier with silicon switch in the input matching circuit has obtained the frequency tuning range of 2.5,3.5 GHz with no significant loss in efficiency and linearity. 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2010. [source]


    Design of coplanar waveguide elliptic low pass filters

    INTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 5 2009
    Amjad A. Omar
    Abstract This article proposes three design topologies of coplanar waveguide elliptic low pass filters. The design procedure is simple and explained in detail for the first topology. Numerical results are provided using the commercially available simulation softwares IE3D and HFSS to show the validity of the design with very good agreement. The proposed filters yield less than 0.1 dB attenuation in the passband (0,2 GHz), with a controllable slope of the transition between passband and stopband. The width of the rejection band is increased by simple filter cascading resulting in a passband to stopband ratio of up to 1:6. 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2009. [source]