Distribution by Scientific Domains

Selected Abstracts

Enzyme-mediated sulfide production for the reconstitution of [2Fe,2S] clusters into apo-biotin synthase of Escherichia coli

FEBS JOURNAL, Issue 9 2000
Sulfide transfer from cysteine to biotin
We previously showed that biotin synthase in which the (Fe,S) cluster was labelled with 34S by reconstitution donates 34S to biotin [B. Tse Sum Bui, D. Florentin, F. Fournier, O. Ploux, A. Mjean & A. Marquet (1998) FEBS Lett. 440, 226,230]. We therefore proposed that the source of sulfur was very likely the (Fe,S) centre. This depletion of sulfur from the cluster during enzymatic reaction could explain the absence of turnover of the enzyme which means that to restore a catalytic activity, the clusters have to be regenerated. In this report, we show that the NifS protein from Azotobacter vinelandii and C-DES from Synechocystis as well as rhodanese from bovine liver can mobilize the sulfur, respectively, from cysteine and thiosulfate for the formation of a [2Fe,2S] cluster in the apoprotein of Escherichia coli biotin synthase. The reconstituted enzymes were as active as the native enzyme. When [35S]cysteine was used during the reconstitution experiments in the presence of NifS, labelled (Fe35S) biotin synthase was obtained. This enzyme produced [35S]biotin, confirming the results obtained with the 34S-reconstituted enzyme. NifS was also effective in mobilizing selenium from selenocystine to produce an (Fe,Se) cluster. However, though NifS could efficiently reconstitute holobiotin synthase from the apoform, starting from cysteine, these two effectors had no significant effect on the turnover of the enzyme in the in vitro assay. [source]

Comprehensive Modeling of Ion Conduction of Nanosized CaF2/BaF2 Multilayer Heterostructures

Xiangxin Guo
Abstract Molecular beam epitaxy-grown CaF2/BaF2 heterolayers are a demonstration of the potential of nanoionics. It has been shown that ion conductivities both parallel and perpendicular to the interfaces increase with decrease in interfacial spacing. This size effect was attributed to the thermodynamically necessary redistribution of the mobile fluoride ions (N. Sata, K. Eberl, K. Eberman, J. Maier, Nature 2000, 408, 946; X. X. Guo, I. Matei, J.-S. Lee, J. Maier, Appl. Phys. Lett. 2007, 91, 103102). On this basis, the striking phenomenon of an upward bending in the effective parallel conductivity as a function of inverse interfacial spacing for low temperatures (T,,,593,K) has been satisfactorily explained by application of a modified Mott,Schottky model for BaF2 (X.X. Guo, I. Matei, J. Jamnik, J.-S. Lee, J. Maier, Phys. Rev. B 2007, 76, 125429). This model was further confirmed by measurements perpendicular to the interfaces that offer complementary information on the more resistive parts. Here a successful comprehensive modeling of parallel and perpendicular conductivities for the whole parameter range, namely for interfacial spacings ranging from 6 to 200,nm and investigated temperatures ranging from 455 to 833,K, is presented. The model is based on literature data for carrier mobilities and Frenkel reaction constants and the assumption of a pronounced F, redistribution. Given the fact that an impurity content that was experimentally supported is taken into account and apart from minor assumptions concerning profile homogeneity, the only fit parameter is the space charge potential. In particular, it is worth mentioning that in BaF2 the low temperature Mott,Schottky space charge zone which is determined by impurities changes over, at high temperatures, into a Gouy,Chapman situation owing to increased thermal disorder. (The situation in CaF2 is of Gouy,Chapman type at all temperatures.) [source]

Kinetic isotope effects for the H2 + C2H , C2H2 + H reaction based on the ab initio calculations and a global potential energy surface

Liping Ju
In the present paper, kinetic isotope effects of the title reaction are studied with canonical variational transition state theory on the modified Wang Bowman (MWB) potential energy surface (PES) (Chem Phys Lett 2005, 409, 249) and the ab initio calculations at the quadratic configuration interaction (QCISD (T, full))/aug-cc-pVTZ//QCISD (full)/cc-pVTZ level. The calculated rate constants for the isotopic variants of this title reaction on the MWB PES have good agreement with those of the present ab initio calculations over the temperature range of 20,5000 K for the forward reactions and 800,5000 K for the reverse reactions, respectively. In particular, the forward rate constants for the title reaction and its isotopically substituted reactions have negative temperature dependences at about 40 K. Rate expressions are presented for all the studied reactions. 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 289,298, 2010 [source]

Circuits, computers, and beyond Boolean logic,

Tams Roska
Abstract Historically, the invention of the stored programmable computer architecture, introduced by John Von Neumann, was also influenced by electrical circuit implementation aspects, as well as tied to fundamental insight of logic reasoning. It can also be considered as a mind-inspired machine. Since then, the implementation of logic gates, control and memories has developed independently of the architecture. The Cellular Wave Computer architecture (IEEE Trans. Circuits Syst. II 1993; 40:163,173; Electron. Lett. 2007; 43:427,449; J. Circuits Syst. Comput. 2003; 5(2):539,562) as a spatial,temporal universal machine on flows has also been influenced by circuit aspects of very large-scale integration (VLSI) technology, as well as some motivating living neural circuits, via the cellular nonlinear (neural) network (CNN). It might be considered as a brain-inspired machine. In this paper, after summarizing the main properties of the Cellular Wave Computer, we highlight a few basic properties of this new kind of computer and computing. In particular, phenomena related to (i) the one-pass solution of a set of implicit equations due to real-time spatial array feedback, (ii) the true random signal array generation via the insertion of the continuous physical noise signals, (iii) the finite synchrony radius due to the functional delay of wires, as well as to (iv) biology relevance. We also show that the Cellular Wave Computer is performing spatial,temporal inference that goes beyond Boolean logic, a characteristic of living neural circuits. Copyright 2007 John Wiley & Sons, Ltd. [source]

Modelling of wireless TCP for short-lived flows,

Sangheon Pack
Abstract The transmission control protocol (TCP) is one of the most important Internet protocols. It provides reliable transport services between two end-hosts. Since TCP performance affects overall network performance, many studies have been done to model TCP performance in the steady state. However, recent researches have shown that most TCP flows are short-lived. Therefore, it is more meaningful to model TCP performance in relation to the initial stage of short-lived flows. In addition, the next-generation Internet will be an unified all-IP network that includes both wireless and wired networks integrated together. In short, modelling short-lived TCP flows in wireless networks constitutes an important axis of research. In this paper, we propose simple wireless TCP models for short-lived flows that extend the existing analytical model proposed in [IEEE Commun. Lett. 2002; 6(2):85,88]. In terms of wireless TCP, we categorized wireless TCP schemes into three types: end-to-end scheme, split connection scheme, and local retransmission scheme, which is similar to the classification proposed in [IEEE/ACM Trans. Networking 1997; 756,769]. To validate the proposed models, we performed ns-2 simulations. The average differences between the session completion time calculated using the proposed model and the simulation result for three schemes are less than 9, 16, and 7 ms, respectively. Consequently, the proposed model provides a satisfactory means of modelling the TCP performance of short-lived wireless TCP flows. Copyright 2005 John Wiley & Sons, Ltd. [source]

Interaction of atoms with graphenic-type surfaces for the chemistry of the interstellar medium: New properties of H dimers on the surface

D. Teillet-Billy
Abstract Following the works of Rougeau et al. (Chem Phys Lett 2006, 431,135) and Ferro et al. (Phys Rev B 2008, 78, 085417) on the one-sided double chemisorption of H atoms on graphenic platelets, we investigate the two-sided double chemisorption using DFT-GGA PW91 calculations. Equilibrium characteristics and potential energy curves for chemisorption are reported for the ortho, meta, para, and bottom positions. Contrary to the one-sided case, the two-sided ortho chemisorption, as well as the bottom position, is barrier-less, whereas the two-sided para chemisorption exhibits an activation barrier. The highest occupied Kohn-Sham orbital (HOKSO) of the H-graphene radical is shown to signal the privileged barrier-less double chemisorption sites. 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 [source]

Observer design for nonlinear discrete-time systems: Immersion and dynamic observer error linearization techniques

Jian Zhang
Abstract This paper focuses on the observer design for nonlinear discrete-time systems by means of nonlinear observer canonical form. At first, sufficient and necessary conditions are obtained for a class of autonomous nonlinear discrete-time systems to be immersible into higher dimensional observer canonical form. Then a method called dynamic observer error linearization is developed. By introducing a dynamic auxiliary system, the augmented system is shown to be locally equivalent to the generalized observer form, whose nonlinear terms contain auxiliary states and output of the system. A constructive algorithm is also provided to obtain the state coordinate transformation. These results are an extension of their counterparts of nonlinear continuous-time systems to nonlinear discrete-time systems (Syst. Control Lett. 1986; 7:133,142; SIAM. J. Control Optim. 2003; 41:1756,1778; Int. J. Control 2004; 77:723,734; Automatica 2006; 42:321,328; IEEE Trans. Automat. Control 2007; 52:83,88; IEEE Trans. Automat. Control 2004; 49:1746,1750; Automatica 2006; 42:2195,2200; IEEE Trans. Automat. Control 1996; 41:598,603; Syst. Control Lett. 1997; 31:115,128). Copyright 2009 John Wiley & Sons, Ltd. [source]

Design of nonlinear observers with approximately linear error dynamics using multivariable Legendre polynomials

Joachim Deutscher
Abstract This paper presents a numerical approach to the design of nonlinear observers by approximate error linearization. By using a Galerkin approach on the basis of multivariable Legendre polynomials an approximate solution to the singular PDE of the observer design technique proposed by Kazantzis and Krener (see (Syst. Control Lett. 1998; 34:241,247; SIAM J. Control Optim. 2002; 41:932,953)) is determined. It is shown that the L2 -norm of the remaining nonlinearity in the resulting error dynamics can be made small on a specified multivariable interval in the state space. Furthermore, a linear matrix equation is derived for determining the corresponding change of co-ordinates and output injection such that the proposed design procedure can easily be implemented in a numerical software package. A simple example demonstrates the properties of the new numerical observer design. Copyright 2006 John Wiley & Sons, Ltd. [source]

On the tetragonality of the room-temperature ferroelectric phase of barium titanate, BaTiO3

Dean S. Keeble
The room-temperature phase of the important ferroelectric material barium titanate, BaTiO3, was re-investigated by single-crystal X-ray diffraction on a sample grown by the top-seeded solution growth method, with the intention of demonstrating once again that the structure has tetragonal symmetry consistent with the space-group assignment P4mm and thus resolving recent controversy in the scientific community and literature [Yoshimura, Kojima, Tokunaga, Tozaki & Koganezawa (2006). Phys. Lett. A, 353, 250,254; Yoshimura, Morioka, Kojima, Tokunaga, Koganezawa & Tozaki (2007). Phys. Lett. A, 367, 394,401]. To this end, the X-ray diffraction pattern of a small (341,m3) sample of top-seeded solution-grown BaTiO3 was measured using an Oxford Diffraction Gemini CCD diffractometer employing Mo,K, radiation and an extended 120,mm sample-to-detector distance. More than 104 individual diffraction maxima observed out to a maximum resolution of 0.4, were indexed on two tetragonal lattices. These were identical to within the standard deviations on the lattice parameters and were related to each other by a single rotation of 119.7 about the [11] direction of the first tetragonal lattice (the major twin component), although the actual twinning operation that explains the observed diffraction pattern both qualitatively and quantitatively is shown to be conventional 90 twinning by the m[101] operation. Importantly, it is not necessary to invoke either monoclinic symmetry or a coexistence of tetragonal and monoclinic phases to explain the observed diffraction data. [source]

A dual-level state-specific time-dependent density-functional theory

Seiken Tokura
Abstract A highly efficient new algorithm for time-dependent density-functional theory (TDDFT) calculations is presented. In this algorithm, a dual-level approach to speed up DFT calculations (Nakajima and Hirao, J Chem Phys 2006, 124, 184108) is combined with a state-specific (SS) algorithm for TDDFT (Chiba et al., Chem Phys Lett 2006, 420, 391). The dual-level SS-TDDFT algorithm was applied to excitation energy calculations of typical small molecules, the Q bands of the chlorophyll A molecule, the charge-transfer energy of the zincbacteriochlorin,bacteriochlorin model system, and the lowest-lying excitation of the circumcoronene molecule. As a result, it was found that the dual-level SS-TDDFT gave correct excitation energies with errors of 0.2,0.3 eV from the standard TDDFT approach, with much lower CPU times for various types of excitation energies of large-scale molecules. 2007 Wiley Periodicals, Inc. J Comput Chem, 2008 [source]

Dispersion in non-ideal packed beds

AICHE JOURNAL, Issue 2 2010
U. M. Scheven
Abstract This work reanalyzes published time series dispersion traces (Han et al., AIChE J. 1985;31:277,288) from step input tracer passages recorded at different locations along the length of a packed bed filled with monodisperse solid spheres. The intrinsic dispersivity and sample dependent dispersion are separated by imposing a heuristic model where coarse grained axial advection velocities vary in a plane perpendicular to the flow but not along the direction of flow. The derived intrinsic dispersivity agrees with the predicted value (Scheven et al., Phys Rev Lett. 2007;99:054502-1,054502-4). It serves as a bench mark for different implementations of simulations coupling Stokes flow and diffusion in random geometries, and for experimental tests of injection and packing methods. Conceptually, a well defined and fittable effective dispersivity is introduced in an analytical framework describing dispersion data obtained in non-ideal packed beds, where elution profiles cannot be fitted to the solution of the one dimensional advection diffusion equation. 2009 American Institute of Chemical Engineers AIChE J, 2010 [source]

HCV-RNA In Sural Nerve From Hcv Infected Patients With Peripheral Neuropathy

L De Martino
Objective: Evaluation of hepatitis C virus (HCV) by reverse transcription-polymerase chain reaction (RT-PCR) in peripheral nerve tissues from HCV infected patients with peripheral neuropathy. METHODS: RT-PCR was performed on homogenates of nerve biopsies from 17 consecutive HCV-positive patients with peripheral neuropathy, with or without mixed cryoglobulinemia, hospitalised from 1996 to 2000. Sural nerve specimens were frozen in iso-pentane pre-cooled in liquid nitrogen and stored at ,80C until use. RNA was extracted from ten 7-,m thick cryostatic sections or from a nerve trunk specimen of about 3 mm length, collected from each biopsy. Three different protocols of RNA extraction were tested (1,3). Complementary DNAs (cDNAs) were obtained without or with RNasin (Promega, Madison, WI) addition in the reaction mixture to inhibit residual RNase activity. Two sets of commercially available PCR primers for the outer and the nested reaction were used. PCR products were analysed by agarose gel electrophoresis and ethidium bromide staining. Serum samples and liver specimens from proven HCV positive patients served as positive controls, whereas sera from healthy subjects were negative controls. RESULTS: Sufficient amount of RNA could be obtained either by cryostatic sections or by in toto nerve specimens. Extraction by Trizol (Gibco-BRL) allowed the best concentration and purity of RNA as assessed by biophotometry. The presence of RNasin didn't improve the cDNA synthesis. The resulting amplification product of the nested PCR was 187 bp long. We have always observed this product in our positive controls and never in the negative. Six samples from patients either with or without cryoglobulinemia resulted positive; 7 were negative. Four samples gave variable results. CONCLUSIONS: While 40% of the nerves in our series were undoubtedly HCV positive, the cause(s) of negative and variable results in the remaining samples is likely more complex than variations in the detection protocols and deserve further investigations. REFERENCES: 1) Chomczynski P, Sacchi N (1987). Anal Biochem 162:156. 2) Marquardt O et al. (1996). Med Microbiol Lett 5:55. 3) Chomczynski P (1993). Bio/Techniques 15:532. [source]

Global stability and the Hopf bifurcation for some class of delay differential equation

Marek Bodnar
Abstract In this paper, we present an analysis for the class of delay differential equations with one discrete delay and the right-hand side depending only on the past. We extend the results from paper by U. Fory, (Appl. Math. Lett. 2004; 17(5):581,584), where the right-hand side is a unimodal function. In the performed analysis, we state more general conditions for global stability of the positive steady state and propose some conditions for the stable Hopf bifurcation occurring when this steady state looses stability. We illustrate the analysis by biological examples coming from the population dynamics. Copyright 2007 John Wiley & Sons, Ltd. [source]

A flexible RF transmitter module based on flexible printed circuit board by using micro-machining fabrication process

Seong-Sik Myoung
Abstract This article presents a flexible RF transmitter module based on flexible printed circuit board (FPCB). The polyimide with micro-machining fabrication technique is employed for realization of FPCB to achieve the high flexibility as well as low loss at microwave frequency band. The active devices in the proposed flexible RF transmitter are design with InGaP/GaAs hetero-junction bipolar transistor monolithic microwave integrated circuit process, and the passive devices such as the filter and interconnection lines are fully integrated on the FPCB board to avoid use of external off-chip components for maximized flexibility. The FPCB transmitter module is designed for a short-distance sensor network based on OFDM communication system, and the measured conversion gain and error vector magnitude of the fabricated flexible transmitter are 27 dB and ,32 dB, respectively. 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2636,2639, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25572 [source]

An optimum superconducting ultra-wideband bandpass filter at VHF band

Wei Chen
Abstract A highly selective superconducting ultra-wideband filter with a passband from 125 to 260 MHz is designed and demonstrated using a microstrip structure. The filter is designed according to a circuit model for an optimum short-circuited stub transmission-line filter and consists of 10 shunt short-circuited stubs separated by connecting lines. The short-circuited stubs are quarter-wavelength long, and the connecting lines are half-wavelength long. The filter is realized on two 3-inch YBCO/LaAlO3 substrates, which are connected by two bonding wires. The short-circuited stubs are grounded via two grounding pads that are attached to the box wall by a number of SiAl bonding wires. The measured results exhibit a selective filtering characteristic equivalent to a 19-pole Chebyshev filter and a low insertion loss of less than 0.1 dB at center frequency without tuning. Furthermore, the experimental results of the filter are in good agreement with the simulated ones. 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2639,2641, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25571 [source]

A low-phase-noise CMOS quadrature VCO with PMOS back-gate coupling

Mei-Ling Yeh
Abstract A new PMOS backgate quadrature voltage controlled oscillator (QVCO) is designed and implemented using TSMC 0.18 ,m 1P6M CMOS technology. The phase noise of the PMOS back-gate coupled QVCO operating at 1.5 V is measured to be ,100 dBc/Hz and ,125.08 dBc/Hz at 100 KHz and 1 MHz offset, respectively, for a low power consumption of 15 mW. The backgate QVCO demonstrates a wide frequency tuning range, a low phase noise, and a low power consumption. The corresponding figure-of-merit of the QVCO is ,186 dBc/Hz. 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2682,2685, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25564 [source]

Single elements for low cost planar antenna arrays for consumer applications beyond 100 GHz

Pablo Herrero
Abstract Single planar element designs working at frequencies around 122 GHz are presented. The structures are designed keeping in mind future commercial applications that might arise in mm-wave bands. Therefore, structures are explored with different radiation patterns. The antennas are implemented using commercial substrate and common photolithography to meet low cost requirements of consumer applications. Matching and radiation pattern was measured showing very good agreement simulations. 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2685,2688, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25563 [source]

A 60-GHz CMOS receiver front-end with integrated 180 out-of-phase Wilkinson power divider

Jen-How Lee
Abstract A 60-GHz receiver front-end with an integrated 180 out-of-phase Wilkinson power divider using standard 0.13 ,m CMOS technology is reported. The receiver front-end comprises a wideband low-noise amplifier (LNA) with 12.4-dB gain, a current-reused bleeding mixer, a baseband amplifier, and a 180 out-of-phase Wilkinson power divider. The receiver front-end consumed 50.2 mW and achieved input return loss at RF port better than ,10 dB for frequencies from 52.3 to 62.3 GHz. At IF of 20 MHz, the receiver front-end achieved maximum conversion gain of 18.7 dB at RF of 56 GHz. The corresponding 3-dB bandwidth (,3 dB) of RF is 9.8 GHz (50.8,60.6 GHz). The measured minimum noise figure (NF) was 9 dB at 58 GHz, an excellent result for a 60-GHz-band CMOS receiver front-end. In addition, the measured input 1-dB compression point (P1 dB) and input third-order inter-modulation point (IIP3) are ,20.8 dBm and ,12 dBm, respectively, at 60 GHz. These results demonstrate the adopted receiver front-end architecture is very promising for high-performance 60-GHz-band RFIC applications. 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2688,2694, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25559 [source]

High-gain, short-circuited six-monopole-antenna system for concurrent, dual-band WLAN access points

Saou-Wen Su
Abstract A high-gain, short-circuited multimonopole antenna system for wireless access points in the concurrent 2.4 and 5 GHz WLAN bands is presented. The antenna system mainly comprises a circular antenna ground and six short-circuited, single-band monopole antennas, among which the three antennas are designated for 2.4 and 5 GHz operation respectively. The monopole antennas are set in a sequential, rotating arrangement on the antenna ground, and the 2.4 and 5 GHz antennas are facing each other one by one. Experimental results show that well port isolation can be obtained between the antenna ports with high-gain properties over the 2.4 and 5 GHz bands. A design prototype is elaborated and discussed in the article. 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2728,2732, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25588 [source]

Coherent detection for spectral amplitude-coded optical label switching systems

Alexey V. Osadchiy
Abstract Coherent detection for spectrally encoded optical labels is proposed and experimentally demonstrated for three label tones spectrally spaced at 1 GHz. The proposed method utilizes a frequency swept local oscillator in a coherent receiver supported by digital signal processing for improved flexibility and upgradeability while reducing label detection subsystem complexity as compared with the conventional optical autocorrelation based approaches. 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2732,2735, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25585 [source]

Cavity backed dual slot antenna for gain improvement

Jin Xin Li
Abstract A simple method of gain improvement for the cavity backed slot antenna based on the substrate integrated waveguide technique has been presented in this article. By using dual slot at the cavity edges to substitute a single slot at the cavity center as the radiating element, gain of the cavity backed slot antenna has been improved about 1.7 dB whereas its total size is little reduced. The proposed antenna has high radiation performance and keeps the advantages low profile, easy integration, and low cost fabrication. 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2767,2769, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25582 [source]

A novel miniature monopole tag antenna for passive UHF RFID applications

Hsien-Wen Liu
Abstract A novel miniature monopole tag antenna for passive Ultra-High Frequency (UHF) radio frequency identification (RFID) operation is presented. The antenna possesses a two-sided structure that is printed on an FR4 substrate and fed by a 50-, microstrip line. By properly using helical strips and vias, the antenna size can be reduced to a small volume of 10 (L) 9.5 (W) 0.8 (H) mm3 to be easily integrated within various portable devices. A miniaturized quasi-lumped circuit is also designed to attain a good impedance matching between the antenna and the chip. Experimental results demonstrate that the antenna has a suitable operating band about 914,939 MHz and also quite omnidirectional radiation pattern with appreciable gain. Moreover, the proposed compact tag antenna, capable of achieving a maximum readable range of about 5.6 m with an EIRP equal to 4 W, is well suited for RFID applications. 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2770,2772, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25596 [source]

Extension of the exhaustive Gaussian approach for BER estimation in experimental direct-detection OFDM setups

Tiago M. F. Alves
Abstract An extension of the exhaustive Gaussian approach to estimate the bit error ratio from a set of experimental runs in direct-detection orthogonal frequency division multiplexing optical communication systems is proposed. The approach provides fast and accurate bit error ratio estimates avoiding the high amount of data required by direct error counting. 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2772,2775, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25595 [source]

Compact dual-band multiple input multiple output antenna with high isolation performance

Insu Yeom
Abstract A compact dual-band (WLAN 11b; 2.4 GHz , 2.5 GHz, 11a; 5.15 GHz , 5.825 GHz) 2-channel Multiple Input Multiple Output (MIMO) antenna for portable media player (PMP) applications is presented. The proposed antenna is composed of a planar inverted F-shape antenna (PIFA) operating at 2 GHz band and a loop antenna operating at 5-GHz band. The antenna made up of the composite loop and PIFA antenna (CLPA) with connecting line face to the feed point and is orthogonally arranged at the edge of the ground plane for reducing mutual coupling. The antenna shows polarization and pattern diversities with excellent isolation characteristics. The two antennas were connected with each other in the bottom side to improve the isolation at 5-GHz band. The proposed antenna has a sufficient gain in WLAN service band and is compact sized for the PMP applications. 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2808,2811, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25614 [source]

Efficient high gain with low sidelobe level antenna structures using circular array of square parasitic patches on a superstrate layer

R. K. Gupta
Abstract This article proposes efficient high gain with low sidelobe level (SLL) antenna structures using circular array of square parasitic patches (CASPPs) for wireless applications. The antenna structure consists of a microstrip antenna that feeds a CASPP fabricated on a low cost FR4 superstrate. The patches on superstrate are suspended in air at about ,o/2. The structure with 19-element CASPPs is designed, fabricated, and tested. The measured VSWR is <2 over 5.725,5.875 GHz frequency band. The antenna with a single square patch provides a gain of 12.6 dB; whereas, the antenna with 19-element CASPPs provides a gain of 18.3 dB with 93.4% efficiency, SLL of ,26.1 dB, and front to back lobe ratio of >20 dB. Antenna with CASPPs on finite ground requires 25% less ground plane size as compared to planar array. The proposed structure can be packaged inside an application platform. 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2812,2817, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25613 [source]

Erratum: Single-shot all-optical sampling oscilloscope using a polarization-maintaining resonator for pulse replication

j Komanec
Originally published Microwave Opt Technol Lett 52: 2452,2456, 2010. 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 2853, 2010; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/mop.25620 (Original article DOI 10.1002/mop.25509) [source]

Ultra-wideband pulse waveform generation based on combining subnanosecond Gaussian pulses

Pavel Protiva
Abstract A technique for generating ultra-wideband pulse waveforms is described in this article. It consists in combining subnanosecond Gaussian pulses from multiple sources. This method enables us to form complex pulse waveforms without the need to use transmission line pulse forming networks and delay lines. Two designs for an experimental generator utilizing the pulse combining principle are presented. The first generator is composed of two positive Gaussian pulsers and one negative Gaussian pulser. Analog time shifters were used to control the timing of each pulser. The circuit can be used as the generator of a Gaussian doublet. The second generator is composed of four identical Gaussian pulsers. Programmable ECL logic delay chips were employed to adjust the timing in this case. The measurements demonstrate the wide capability of the pulse combining scheme for controlling the spectral properties of the pulse waveform that is generated. 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2401,2405, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25498 [source]

Novel planar triple band monopole antenna for WiMAX/WLAN applications

Hsien-Wen Liu
Abstract A coplanar waveguide (CPW)-fed planar monopole antenna with triple band operation for worldwide interoperability for microwave access (WiMAX) and wireless local area network (WLAN) applications is presented. The antenna, which occupies a small size of 25 (L) 25 (W) 0.8 (H) mm3, is simply composed of a pentagonal radiating patch with two bent slots. By carefully selecting the positions and lengths of these slots, good dual stopband rejection characteristic of the antenna can be obtained, so that three operating bands covering 2.14,2.85, 3.29,4.08, and 5.02,6.09 GHz can be achieved. The measured results also demonstrate that the proposed antenna has good omnidirectional radiation patterns with appreciable gain across the operating bands, and is thus suitable to be integrated within the portable devices for WiMAX/WLAN applications. 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2405,2408, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25497 [source]

X-band low phase noise in-phase and out-of-phase injection-locked push,push DRO

Zhou Cao
Abstract An X-band push,push dielectric resonator (DR) oscillator with injection locking capability has been developed. Two injection locking methods, i.e., the in-phase method and the out-of-phase method, are studied. It is found that the out-of-phase method has wider locking range and much less effects on fundamental suppression than that of the in-phase method. The oscillator generates an output power of 9.5 dBm at 12.4 GHz and has a fundamental suppression of 32.5 dBc. Despite using a high quality (Q) factor DR, wide locking range has been obtained. SiGe HBTs with good flicker noise performance were chosen for low phase noise design. The phase noise values of the free running oscillator are ,104.4 dBc/Hz, ,120.2 dBc/Hz, and ,142.6 dBc/Hz at 10 kHz, 100 kHz, and 1 MHz offsets from the carrier frequency, respectively. The phase noise performance is superior or comparable to the reported designs. 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2448,2452, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25510 [source]

Single-shot all-optical sampling oscilloscope using a polarization-maintaining resonator for pulse replication

j Komanec
Abstract An all-optical single-shot sampling oscilloscope with a picosecond resolution is developed. An innovative approach for data pulse replication using a polarization-maintaining resonator is used. Pulses are sampled in a highly nonlinear fiber. Acquired data are used for pulse shape reconstruction. Proposed setup eliminates the need of a delay line. 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2452,2456, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25509 [source]