bluuebunny/crossref_metadata_2025 huggingface dataset:
The Study of Cavitation in HDPE Using Time Resolved Synchrotron X‐ray Scattering During Tensile Deformation
Authors: Schneider K. , Trabelsi S. , Zafeiropoulos N.E. , Davies R. , Riekel Chr. , Stamm M.
Published: March 2006

Real time synchrotron Small‐Angle and Wide‐Angle X‐ray Scattering was performed during the tensile deformation of a high‐density polyethylene copolymer. The changes of the structure in the crystalline and in the amorphous domains were followed during the three characteristic stages of the load‐displacement curves: The elastic stage and the plastic range composed of the stage of the lowering load in the force‐displacement‐curve (yielding) and the strain hardening. Competitive phenomena like crystallite fragmentation and cavitation were found to occur simultaneously in the phase of lowering the load but at different length scale. We prove that the void formation occurs mainly during yielding. During strain hardening there was no further increase of the void volume fraction, only changes in void size.
Morphology Evolution in the Early Stages of Olefin Polymerization
Authors: Zheng Xuejing , Loos Joachim
Published: March 2006

The olefin polymerizations were carried out by using silica supported metallocene/MAO catalysts and MgCl2 supported Ziegler‐Natta catalysts under mild reaction conditions and stopped at very low yield. The surface and cross sectional morphology of the polymer particles were characterized by using scanning electron microscopy (SEM). A homogeneous distribution of (co)catalyst on the support material is a prerequisite condition to get a homogeneous fragmentation and uniform polymer particle morphology. In the present work the catalysts show two different fragmentation behaviors. They can gradually fragment from the outer to the inner surface of the catalyst particle, or instantaneously break up into a large amount of small sub‐particles at the beginning of the polymerization. The incorporation of comonomer does not change the general catalyst fragmentation scheme but delays the catalysts break‐up progress.
Novel Initiators for Thermally and UV‐Triggered ROMP
Authors: Zhang Yan , Wang Dongren , Lönnecke Peter , Scherzer Thomas , Buchmeiser Michael R.
Published: March 2006

Novel ruthenium‐based photoactive transition metal catalysts, i.e. [Ru(CF3CO2)2(p‐cymene)(IMes)] (2), [Ru(CF3CO2)2(PhNC)3(IMes)] (3), [Ru(CF3CO2)2(p‐cymene) (IMesH2)] (4), [Ru(CF3CO2)2(PhNC))3(IMesH2)] (5), have been prepared and investigated for their use as initiators for the thermally and photo‐initiated ring‐opening metathesis polymerization (photo‐ROMP). The polymerization behavior of the novel systems for both norborn‐2‐ene and functional monomers, such as norborn‐5‐ene‐ 2‐ylmethanol, has been investigated.
Single‐Site Organochromium Catalysts: Synthesis, Characterisation by Paramagnetic NMR and Olefin Polymerisation
Authors: Enders Markus
Published: March 2006

Chromium(III)‐complexes with monoanionic spectator ligands allow the preparation of highly active catalysts for ethylene polymerisation. We summarize the synthesis and NMR‐spectroscopic investigations of precatalysts with quinolyl‐functionalised Cp‐ligands. These complexes have advantageous properties. For spectroscopic investigations the rigidity of the ligand framework helps to identify the species present in solution as fewer conformers are possible. For the application as polymerisation catalysts the high stability of the activated catalyst is important. We obtained meaningful analytical data by paramagnetic NMR, combined with DFT‐calculation of the spin‐density. These and other investigations lead to the conclusion, that the active species is a cationic chromium(III)alkyl complex. However, at present we have not enough information about the exact structure of this species in the absence of coordinating solvent molecules.
Methylalumoxane (MAO)‐Derived MeMAO− Anions in Zirconocene‐Based Polymerization Catalyst Systems – A UV‐Vis Spectroscopic Study
Authors: Wieser Ulrich , Schaper Frank , Brintzinger Hans‐Herbert
Published: March 2006

Reaction of Me2Si(Ind)2ZrCl2 with excess methylalumoxane (MAO) gives rise to ion pairs containing zirconocenium cations of the type [Me2Si(Ind)2ZrMe]+ in contact with two types of anions, MeMAOA− and MeMAOB−, which differ in their coordinative strengths: More strongly coherent contact‐ion pairs [Me2Si(Ind)2 ZrMe+..MeMAOB−] are converted by a sufficiently high excess of MAO to more easily separable contact‐ion pairs [Me2Si(Ind)2ZrMe+..MeMAOA−], which react with AlMe3 to form the outer‐sphere ion pairs [Me2Si(Ind)2Zr(µ‐Me)2AlMe2]+ MeMAOA−, and are likely to be required also for the formation of the olefin‐containing reaction complexes responsible for catalytic activity.
Solvent‐Ligated Transition Metal Complexes as Initiators for the Polymerization of Isobutene
Authors: Nuyken Oskar , Vierle Mario , Kühn Fritz E. , Zhang Yanmei
Published: March 2006

After a brief introduction of the history of polyisobutene and the description of an interesting commercial process, this article is focused on the mechanism of the isobutene initiation and propagation. Furthermore, the INIFER technique will be briefly discussed. Finally, it will be shown that polyisobutene with a high content of terminal olefinic groups can be synthesized by using transition metal complexes in homogeneous solution at room temperature. Mechanisms of the isobutene polymerization initiated by this new class of initiators will be suggested.
Microkinetic Videomicroscopic Analysis of the Olefin‐Copolymerization with Heterogeneous Catalysts
Authors: Ferrari Daniela , Knoke Stefan , Tesche Bernd , Fink Gerhard
Published: March 2006

Videomicroscopy as a tool for investigating olefin gas phase co‐polymerization is presented in this paper. This technique enables the simultaneous detection of the individual growth of a large number of catalyst particles. The focus is to study the kinetic behaviour of different types of Ziegler‐ and metallocene catalysts and to demonstrate that videomicroscopy can help to assign a given catalyst system to the appropriate model. Further, the density problem, the estimation of activation energies of single grains, the particle volume enlargement of amorphous copolymers and the comonomer effect are adressed.
Metal Complexes for the Vinyl Addition Polymerization of Norbornene: New Compound Classes and Activation Mechanism with B(C6F5)3/AlEt3
Authors: Janiak Christoph , Lassahn Paul‐Gerhard , Lozan Vasile
Published: March 2006

Classes of mainly nickel(II) and palladium(II) complexes are comparatively presented in their norbornene polymerization activity to vinyl polynorbornene when activated with methylalumoxane, MAO, tris(pentafluorophenyl)borane/triethylaluminum, B(C6F5)3/AlEt3 or even B(C6F5)3 alone. Classes include Ni and Pd complexes with α‐dioxime ligands, salts with [PdCl4]2− and [Pd2Cl6]2− units, dinuclear Ni and Pd complexes with multidentate Schiff‐base ligands, polynuclear Ni‐ and Cr/Ni‐carboxylate cage complexes, and dihalo(bisphosphane) Ni and Pd complexes. The study of activation mechanism by 31P‐ and 19F‐NMR together with X‐ray structural data points to the formation of PdCl2 units and “naked” Pd2+ cations as highly active species.
Cover Picture: Macromol. Symp. 235/2006
Authors: Toshima Naoki
Published: March 2006

Cover: This volume provides a good coverage of the main topics discussed during the 11th Macromolecule‐Metal Complexes Symposium (MMC‐11) held in Tirrenia (Pisa) in Sptember 2005 with IUPAC Sponsorship (Macromolecular Division). The collected papers regard indeed: metal nanoparticles in macromolecular systems for information technology, optoelectronic and energy conversion, polymer supported and embedded metal complexes for catalysis, polyelectrolytes, metal containing membranes, systems for molecular recognition, and nanocomposites. Also environmental applications in heavy metal recovery and biopolymers‐metal systems for diagnostics and materials (leather tanning) are described. As an example, the picture shows schematic formation processes for Bi2Te3 nanoparticles stabilized by a macromolecular environment, taken from the contribution by N. Toshima.
Oral methylphenidate fails to elicit significant changes in extracellular putaminal dopamine levels in Parkinson's disease patients: Positron emission tomographic studies
Authors: Koochesfahani Kaveh M. , de la Fuente‐Fernández Raúl , Sossi Vesna , Schulzer Michael , Yatham Lakshmi N. , Ruth Thomas J. , Blinder Stephan , Stoessl A. Jon
Published: March 2006

In this study, we assessed the changes of endogenous dopamine (DA) levels in response to methylphenidate in 5 patients with idiopathic Parkinson's disease (PD) and 6 healthy controls. Three‐dimensional positron emission tomography was performed with the D2 receptor antagonist [11C]raclopride (RAC) at baseline and 1 hour following the administration of oral methylphenidate (0.8 mg/kg) to assess changes in dopamine levels indirectly. Oral methylphenidate produced no significant change in extracellular DA levels in the putamen, as estimated by comparing changes in RAC binding at baseline and 1 hour following its administration in PD subjects and healthy controls. However, there were small changes in RAC binding of opposite direction in caudate and ventral striatal regions compared between the two groups. Although there was no consistent improvement in motor function in the PD group, some patients did experience a subjective high in response to methylphenidate (MP). Failure of oral MP to alter extracellular DA levels in putamen could result from degeneration of presynaptic dopaminergic terminals, with consequent severe reductions in the levels of endogenous DA and dopamine transporter in PD subjects. Our data provide in vivo neurochemical support for the lack of clinical efficacy following MP in PD patients and are also in keeping with reduced DA release following amphetamine in PD subjects. © 2006 Movement Disorder Society
Bladder dysfunction in Parkinsonism: Mechanisms, prevalence, symptoms, and management
Authors: Winge Kristian , Fowler Clare J.
Published: March 2006

The advent of functional imaging methods has increased our understanding of the neural control of the bladder. This review examines current concepts of the role of brain function in urinary control with particular emphasis on the putative role of dopamine receptors. Dopaminergic mechanisms play a profound role in normal bladder control and the dysfunction of these may result in symptoms of overactive bladder in Parkinsonism. The importance of this nonmotor disorder has been overlooked. We address the problem of bladder dysfunction as it presents to patients and their neurologist. The prevalence of bladder symptoms in Parkinson's disease is high; the most common complaint is nocturia followed by frequency and urgency. In multiple‐system atrophy, the combination of urge and urge incontinence and poor emptying may result in a complex combination of complaints. The management of bladder dysfunction in Parkinsonism addresses treatment of overactive detrusor as well as incontinence. © 2006 Movement Disorder Society
Application of time modulation in the synthesis of sum and difference patterns by using linear arrays
Authors: Fondevila J. , Brégains J. C. , Ares F. , Moreno E.
Published: March 2006

In this paper, time modulation is applied to a small number of elements of a linear array that radiates either sum or difference patterns, in order to take control over their sidelobe levels. The simulated annealing (SA) technique helps to obtain the optimum time pulses applied to such elements in terms of sideband minimization. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 829–832, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21489
Envelope correlation in (N, N) MIMO antenna array from scattering parameters
Authors: Thaysen Jesper , Jakobsen Kaj B.
Published: March 2006

A simple closed‐form equation to calculate the envelope correlation between any two receiver or transmitter antennas in a multi‐input multi‐output (MIMO) system of an arbitrary number of elements is derived. The equation uses the scattering parameters obtained at the antenna feed point to calculate the envelope correlation coefficient. This approach has the advantage that it does not require knowledge of the antenna radiation pattern. Numerical data that include conductor and permittivity loss are shown to validate the approach. Using the scattering parameters for calculating the envelope correlation is less laborious and relatively cheaper, as compared to the radiation pattern approach. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 832–834, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21490
Ultra‐wideband Vivaldi antenna design for multisensor adaptive ground‐penetrating impulse radar
Authors: Turk Ahmet Serdar
Published: March 2006

This paper describes a partially dielectric‐loaded Vivaldi antenna (PDVA) structure that maintains ultra‐wideband antenna characteristics over a bandwidth ratio greater than 25:1 so as to improve the impulse radiation characteristics for multisensor adaptive ground‐penetrating Radar (GPR) operations. The PDVA is introduced for metal‐detector‐combined GPR head designs in order to avoid performance degradations based on the sensor interferences. It is shown that high gain, low input reflection, and signal‐ringing levels over the wide operational bands are attainable for a PDVA with proper dielectric and absorber loadings. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 834–839, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21491
An arbitrary dual‐band microstrip hybrid‐ring
Authors: Dwari Santanu , Sanyal Subrata
Published: March 2006

This paper presents the realization of a dual‐band hybrid‐ring and gives the design formulas. The simulated and measured results of a microstrip dual‐band hybrid‐ring operating at 900/1900 MHz are shown to have good agreement and exhibit good performance at both frequency bands. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 840–842, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21492
L‐band all‐optical gain‐clamped erbium‐doped fiber amplifier via ASE reflection technique
Authors: Zhang Hao , Dou Qingying , Jin Yanli , Guo Tuan , Liu Lihui , Liu Yange , Yuan Shuzhong , Dong Xiaoyi
Published: March 2006

We present an L‐band all‐optical gain‐clamped erbium‐doped fiber amplifier with a fiber‐loop mirror as the ASE reflector. By using the combination of a C/L‐band wavelength division multiplexer (WDM) and fiber‐loop mirror, the backward C‐band amplified spontaneous emission (ASE) is reflected back into the erbium‐doped fiber and works as the control light. The static gain level of this amplifier can be adjusted by changing the ASE feedback. The experimental results show that the EDFA gain can be effectively clamped via this ASE reflection technique. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 852–854, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21496
Compact dual‐band antenna for DCS/2.4 GHz WLAN applications
Authors: Joseph Manoj , Raj Rohith K. , Suma M. N. , Mohanan P.
Published: March 2006

A compact dual‐band antenna operating in the 1.8/2.4‐GHz bands with identical linear polarization suitable for DCS/2.4‐GHz WLAN applications is presented. The proposed configuration is a modified microstrip‐fed printed monopole with an additional strip and a proper truncated ground plane on the opposite side of the substrate. The proposed antenna of dimensions 35 × 47 × 1.6 mm offers 2:1 VSWR bandwidths of 10.8% and 9.8% in the DCS and 2.4‐GHz WLAN bands, respectively. Details of the antenna design and experimental results are discussed. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 856–859, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21498
A miniaturized antenna for surface‐to‐surface and surface‐to‐orbiter applications
Authors: Nessel James A. , Zaman Afroz J. , Miranda Félix A.
Published: March 2006

A folded Hilbert curve fractal antenna (fHCFA) which produces end‐fire radiation at the S‐band and broadside radiation at the Ku‐band without switches is presented. The measured gains/bandwidths were 1.2 dBi/10 MHz and 5.4 dBi/500 MHz at 2.3 GHz (S‐band) and 16.8 GHz (Ku‐band), respectively. This work offers a compact antenna design as a candidate for robotic applications in future NASA planetary exploration missions. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 859–862, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21499
Wideband dual‐polarized antenna array on finite conducting cylinder
Authors: Lai H. W. , Wong T. P. , Mak C. L. , Luk K. M.
Published: March 2006

A wideband dual‐polarized patch antenna array on a finite conducting cylinder is proposed for MIMO applications. By employing the L‐probe coupling method and the phase‐cancellation technique, a dual‐polarized antenna array with characteristics of wide bandwidth and high isolation (1.85–2.24 GHz,S12< −32 dB) was designed, fabricated, and tested. The proposed antenna is suitable for various wireless communication applications, including smart antenna and MIMO system designs. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 862–866, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21500
High gain Er3+‐doped fiber amplifier with double‐pass preamplification stage
Authors: Bouzid Belloui , Abdullah M. K. , Mahdi M. A.
Published: March 2006

A new architecture of dual‐stage erbium‐doped fiber amplifier with double‐pass preamplification is successfully demonstrated. A maximum gain of 52 dB is obtained at −50‐dBm signal power with 1550‐nm signal wavelength. An efficient filtering of amplified spontaneous emission improves gain at the signal wavelength up to 18 dB in the double‐pass amplifier section. The noise‐figure penalty is very minimal in the small‐signal range, compared to the dual‐stage amplifier without bandpass filters. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 866–868, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21501
Internal composite monopole antenna for WLAN/WiMAX operation in a laptop computer
Authors: Wong Kin‐Lu , Chou Liang‐Che
Published: March 2006

A novel composite monopole antenna suitable for 2.4/5.2/5.8‐GHz wireless local area network (WLAN) and 2.5/3.5/5‐GHz worldwide interoperability for microwave access (WiMAX) operation is presented. The composite monopole antenna comprises a ceramic chip radiating element as arm 1 of the antenna and a printed radiating element as arms 2 and 3 of the antenna. The three arms effectively control three excited wide resonant modes for WLAN/WiMAX operation, and the total area occupies by the composite monopole antenna is 8 × 19.5 mm2 only, which is much smaller than that of a corresponding printed monopole antenna. Due to the compact area occupied, the proposed antenna is promising to be embedded within the narrow spacing between the casing of the laptop computer and the supporting metal frame of the display as an internal antenna. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 868–871, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21502
A wideband printed monopole antenna for 2.4‐GHz WLAN applications
Authors: Suma M. N. , Bybi P. C. , Mohanan P.
Published: March 2006

A planar monopole antenna suitable for broadband wireless communication is designed and developed. With the use of a truncated ground plane, the proposed printed monopole antenna offers nearly 60% 2:1 VSWR bandwidth and good radiation characteristics for the frequencies across the operating band. A parametric study of the antenna is performed based on the optimized design, and a prototype of the antenna suitable for 2.4‐GHz WLAN application is presented. The antenna can be easily integrated into wireless circuitry and is convenient for application in laptop computers. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 871–873, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21503
A study of terminated hermite lossless nonuniform transmission lines using mathematica
Authors: Torrungrueng D. , Chou P. Y. , Krairiksh M.
Published: March 2006

The terminated Hermite lossless nonuniform transmission line (HLNUTL) in the steady state is studied in this paper. Due to the complicated equations associated with HLNUTLs, numerical simulations based on Mathematica software are convenient for understanding the propagation physics of HLNUTLs. It is found that HLNUTLs have distinct characteristics compared to other types of transmission lines. For example, it is necessary to match HLNUTLs with reactive loads. The results are verified through case studies by checking the power conservation. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 888–892, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21508
Scattering by a nihility sphere
Authors: Lakhtakia Akhlesh
Published: March 2006

On interrogation by a plane wave, the back‐scattering efficiency of a nihility sphere is identically zero, and its extinction and forward‐scattering efficiencies are higher than those of a perfectly conducting sphere. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 895–896, 2006; Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/mop.21510
Time‐slot interchanging using the crosspoint switch and a recirculating buffer
Authors: Geldenhuys R. , Wang Z. , Chi N. , Tafur Monroy I. , Koonen A. M. J. , Dorren H. J. S. , Leuschner F. W. , Khoe G. D. , Yu S.
Published: March 2006

Because of the low crosstalk of the CrossPoint switch, multiple recirculations are possible. This facilitates simplified time‐slot interchange configurations that depend on less fiber‐delay lines, and single time‐slot granularity to enable a short total‐delay time. Error‐free time‐slot interchange is demonstrated with a 10‐Gb/s payload. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 897–900, 2006; Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/mop.21511
A compact bandpass filter using open‐loop and C‐SCMRC resonators with harmonic suppression
Authors: Gu Jian‐Zhong , Wang Chuang , Sun Xiao‐Wei
Published: March 2006

A novel compact open‐loop resonator bandpass filter is proposed to suppress the spurious passband using a compensated spiral compact microstrip resonant cell (C‐SCMRC). Due to the inherently compact and stopband characteristics of the C‐SCMRC, the proposed filters shows a better spurious‐rejection performance than the only open‐loop resonator filter. The proposed bandpass filter improves the rejection level of 20 dB from 2.8 to 5 GHz. Furthermore, 40‐dB suppression improvement and better than 57‐dB rejection level at the 2nd‐harmonic passband from 3.3 to 3.85 GHz are achieved. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 906–909, 2006; Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/mop.21514
Modified Sierpinski fractal monopole antenna with Descartes circle theorem
Authors: Liu Ji‐Chyun , Wu Ching‐Yang , Chen Chen‐Hsiang , Chang Dau‐Chyrh , Chen Jong‐Yih
Published: March 2006

An innovative modified Sierpinski fractal monopole antenna with multiband performance is proposed in this paper. By using the Descartes circle theorem and a self‐similar iteration design, the antenna is constructed with circular fractal patterns. The resonances exhibit the log periodic characteristic, and the radiation field presents array patterns. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 909–911, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21515
Design of a weathercock‐shaped microstrip patch antenna with a T‐slot for the Hiper‐LAN band
Authors: Choi Sun‐Ho , Yoon Joong‐Han , Lee Hwa‐Choon , Kwak Kyung‐Sup
Published: March 2006

In this paper, a weathercock‐shaped microstrip patch antenna for application in a Hiper‐LAN is designed and fabricated. To obtain sufficient bandwidth when VSWR < 2, the T‐slot is inserted in the patch and a coaxial‐probe source is used. The measured result of the fabricated antenna is 350 MHz or about 7.62% bandwidth when VSWR < 2, referenced to the center frequency, with gain of 5.25–6.70 dBi. The experimental 3‐dB beam width is seen to be broad across the passband for the azimuth and the elevation at 80.32° and 83.88°, respectively. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 911–913, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21516
Microstrip bandpass filter using a triangular‐patch resonator with three transmission zeros
Authors: Li JiaLin , Chen JianXin , Xia Lei , Xue Quan , Xue LiangJin
Published: March 2006

A microstrip bandpass filter (BPF) using a triangular patch resonator is introduced in this paper. With one coupling gap between the input and output ports together with the patch configurations, the filter can realize DC block, lower insertion loss, and higher power‐handling capability. For demonstration purposes, a filter of this type is designed, fabricated, and tested and the measured results for the fabricated BPF show good consistency with the calculated results. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 914–915, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21517
Design of a new wideband microstrip‐fed circular slot antenna
Authors: Habib Mohamed A. , Denidni Tayeb A.
Published: March 2006

In this paper, a new ultra‐wideband slot antenna with a simplified feeding network is presented. This antenna is composed of a circular slot coupled to a circular patch fed with 50Ω microstrip line. A proper parametric investigation was carried out for optimization of the proposed structure. Simulations and measurements show that a large bandwidth from 2.13 to 11.11 GHz can be achieved, which represents a relative bandwidth of 136.4%. Furthermore, good agreement between simulated and experimental results is obtained. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 919–923, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21519
A double‐spiral resonator structure to realize left‐handed material with lower resonant frequency
Authors: Zhao Hui , Cui Tie Jun
Published: March 2006

A double‐spiral resonator (DSR) structure causing negative permeability is proposed in this paper, which combines the characteristics of split‐ring resonator (SRR) and spiral to reduce the resonant frequency. Hence, such a DSR structure has a small unit‐to‐wavelength ratio in realizing the left‐handed property, which behaves more like a material. A quasi‐static analysis is given to make an equivalence of the DSR structure to a left‐handed material (LHM). Simulation results show that such an LHM possesses a small loss. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 923–926, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21520
Reconfigurable printed‐dipole antenna with harmonic trap for wideband applications
Authors: Mirkamali Ali , Hall Peter S. , Soleimani Mohammad
Published: March 2006

This paper presents the concept of using a harmonic trap to design a wideband reconfigurable antenna. The reconfigurable antennas can be used to select one of a number of operating frequency bands. If these bands cover a very wide frequency range, then one of the higher‐frequency bands can be a harmonic of a lower band. When the antenna operates at the lower band, it can have a good match at the high frequency. This paper proposes a technique for designing a wideband reconfigurable printed dipole antenna so as to select only one of the operating frequency bands by using a harmonic trap. The antenna is designed, fabricated, and measured. It is shown that by using switches and harmonic traps, a reconfigurable printed dipole antenna can be designed over a frequency range of 3:1. The antenna is thus suitable for frequency switching in the FCC ultra‐wideband allocation. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 927–929, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21521
Printed collinear two‐antenna element for WLAN access points in a MIMO system
Authors: Wong Kin‐Lu , Chou Jui‐Hung
Published: March 2006

A printed collinear two‐antenna element suitable for application in a wireless local area network (WLAN) access point in a multi‐input multi‐output (MIMO) system is presented. The printed element comprises one dipole antenna and one monopole antenna, both printed in a collinear configuration on a narrow FR4 substrate of width 12 mm and length 120 mm and showing good omnidirectional radiation characteristics. It has been found that an antenna system formed by using two proposed elements spaced 75 mm or larger can have good isolation (better than −20 dB) between any two of the four antennas in the two proposed elements. With the comparison to the conventional antenna system formed by four discrete antennas, the antenna system with two proposed elements shows a much smaller lateral length. This characteristic makes the proposed collinear two‐antenna element advantageous for application in a MIMO system. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 930–933, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21522
Switchable patterned centre‐conductor CPW filter using RF MEMS
Authors: Mariani Michael A. , Roy Langis , Tait R. Niall
Published: March 2006

A novel switchable coplanar waveguide (CPW) notch filter is developed using a microelectromechanical system (MEMS) switch element to perturb a patterned CPW centre‐conductor line. The switch element is easily integrated with the CPW due to isolation of DC bias from RF signal paths. An equivalent lumped‐element model has been developed for simulation of the electrical response of the filter. The measured notch frequency was shifted from 24.75 to 22.25 GHz, with greater then 20‐dB rejection in both states. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 935–938, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21524
An oscillator with low phase noise and superior harmonic suppression characteristics based on uniplanar compact split ring resonators
Authors: Hwang Cheol Gyu , Myung Noh Hoon
Published: March 2006

In this paper, we describe a novel microwave oscillator incorporating a CPW‐based split‐ring resonator (SRR) as a resonant component of the circuit. The high quality (Q) factor and spurious‐free SRR contribute to phase noise reduction as well as the harmonic tuning of the oscillator circuit in a very small chip area. The fabricated 5.5‐GHz oscillator showed an output power of 2.774 dBm with a 2nd‐harmonic suppression of −43.04 dB and phase noise of −100.8 dBc/Hz at 100‐kHz offset. The proposed oscillator is believed to be the first application of a metamaterial to the performance enhancement of a microwave active device. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 938–940, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21525
Fabrication and measurement of a compact meander‐line‐type microstrip patch antenna with shorting pin for the 5‐GHz band
Authors: Yoon Joong Han
Published: March 2006

This paper investigates the characteristics of the modified meander‐line‐type patch antenna for the 5‐GHz band. Its design was based on a modified meander line width and shorting pin with coaxial feeding. Its maximum measured impedance bandwidth (−10 dB and below) reaches approximately 1.64 GHz (4.765–6.405 GHz). Radiation patterns at different frequencies are also discussed, and the measured gains are about 5.74 to 9.09 dBi. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 944–947, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21527
Design of an internal antenna with wide and multiband characteristic for mobile handset
Authors: Park Hoon , Kang Myoung il , Choi Jaehoon
Published: March 2006

The development of a small electrical antenna plays an important role in the rapidly growing mobile communication market. This paper presents the design of a novel small and wideband planar inverted F‐antenna that simultaneously covers the GSM900/GPS/DCS1800/DCS1900/IMT2000/WLAN/DMB service bands. A very wide impedance‐bandwidth characteristic was achieved by optimizing both the distance between the feed line and short strip and the width of a short strip. The commercial electromagnetic software CST Microwave Studio is used to design the structure. The maximum gains at the frequencies of 915, 1850, 2025, and 2450 MHz were 1.79, 3.56, 3.65, and 1.67 dBi, respectively. The overall radiation pattern is suitable for mobile application. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 947–950, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21528
Equivalent circuit modeling of broadband antennas using a rational function approximation
Authors: Kim Youngwook , Ling Hao
Published: March 2006

This paper describes a technique for synthesizing an equivalent circuit for a broadband antenna. A method is proposed for generating a rational function approximation with real coefficients in order to model the input impedance of the antenna in the frequency domain. An algorithm is then developed to find the best‐fit positive‐real rational function that is realizable by passive circuits. The technique is applied to a planar UWB antenna from 3 to 10 GHz. The results show that a modeling error of 0.59% can be achieved. The Brune's theorem is used to synthesize an equivalent circuit of the antenna. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 950–953, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21529
High‐linear‐power MESFET devices using source‐degeneration inductance and input‐impedance mismatch
Authors: Meng C. C. , Wang W.
Published: March 2006

Linearity can be improved drastically by sacrificing power gain with the same output power. GaAs MESFET devices with via‐hole ground and with bond‐wire ground are used to investigate the effect of source‐inductive feedback and input‐impedance mismatch on the effect of linearity. At 2.4 GHz, the device without bond‐wire ground and mismatched input impedance has the highest linearity OIP3= 50 dBm, gain = 13.5 dB gain, andP1dB= 29 dBm, while the device with via‐hole ground and matched input impedance has the lowest linearity OIP3= 40 dBm, 18.3 dB gain, andP1dB= 29 dBm. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 953–954, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21530
Surface plasmon resonance sensors using silica‐on‐silicon optical waveguides
Authors: Chu Yi‐Shin , Hsu Wen‐Hao , Lin Chii‐Wann , Wang Way‐Seen
Published: March 2006

Surface plasmon resonance (SPR) sensors made by multimode silica‐on‐silicon channel waveguides are investigated theoretically and experimentally. Promising sensing characteristics, with sensitivity up to 4547 nm/RIU, are observed over a wide detection range without a conventional tuning‐layer design. The Si‐based device‐fabrication process offers great potential for high‐level sensor integration. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 955–957, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21531
PML implementation in the ADI‐FDTD method using bilinear approximation
Authors: Wang Gang , Huang Binke , Liu Xiaolong
Published: March 2006

Bilinear approximation is employed to implement the perfectly matched layer (PML) absorbing boundary condition in the alternating direction implicit (ADI) finite‐difference time‐domain (FDTD) method. Numerical examples show that this implementation is effective and unconditionally stable. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 957–960, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21532
Piecewise travelling‐wave basis functions for wires
Authors: García‐Tuñón I. , Rodríguez J. L. , Taboada J. M. , Obelleiro F.
Published: March 2006

This paper presents a method of moments (MoM) formulation for large thin‐wire structures. In our approach, a modified version of the well‐known Rao–Wilton–Glisson (RWG) basis functions for wires including a linear phase term is considered. This additional term allows an efficient representation of the travelling‐wave modes on each wire, while it preserves the main advantages of RWG bases for arbitrarily complex wire topologies. The paper contains a detailed description of the algorithm used for the computation of the impedance matrix integrals. Finally, some results for scattering problems are presented to show the agreement with the conventional RWG‐MoM solution. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 960–966, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21533
Beam‐scanning improvement of reflectarrays by reducing the cell size at millimetre waves
Authors: Lanteri J. , Dauvignac J. Y. , Pichot Ch. , Migliaccio C.
Published: March 2006

Most reflectarrays use a half‐wavelength cell size. In this paper, we present a new reflector‐antenna configuration that provides beam scanning and gain improvements by reducing the size of the cells. Small reflectarrays with cell sizes λ/2 and λ/4, respectively, have been designed at 94 GHz. The measured λ/4 reflectarray at 94 GHz achieves a beam scanning angle of ±60° with a loss of gain of 1 dB, whereas the λ/2 one exhibits a loss of 3 dB. Numerical simulations show that the improvement does not appear significant below the limit of λ/6. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 966–968, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21534
A compact inverted double‐L antenna
Authors: Zhuang Zhiming , Shen Zhongxiang , Shum Ping
Published: March 2006

A compact inverted double‐L antenna (CDLA) fed by a microstrip line and operating at 2.45 GHz is presented in this paper. The linearly polarized CDLA can be constructed using conducting wires mounted on a small PCB board. This antenna maintains a simple structure, low profile, and compact size, which can be very useful for mobile communication systems such as Bluetooth and radio frequency identification (RFID) applications. Simulated and measured results are provided and good agreement between them is observed. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 968–969, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21535
CAD formulas of the capacitance to ground of square‐spiral inductors with one‐ or two‐layer substrate by synthetic asymptote
Authors: Tang Wanchun , Pan Tingshan , He Xiaoxiang , Chow Y. Leonard
Published: March 2006

This paper gives simple CAD formulas of the capacitance to ground of square‐spiral inductors on one‐ or two‐layer substrate by synthetic asymptote. From the derived formula, the equivalent capacitor is a fringe capacitor in parallel with an ideal parallel‐plate capacitor. The average error is less than 2%. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 972–977, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21537.
Wideband patch antenna fed by a modified L‐shaped probe
Authors: Lai Hau Wah , Luk Kwai Man
Published: March 2006

This paper presents a wideband patch antenna fed by a modified L probe. The antenna has impedance bandwidth of 21% (SWR < 2) and cross polarization level of less than −15 dB across the operating bandwidth. The antenna has a gain of 8.5 dBi. Both simulated and experimental results are provided, and they are in good agreement. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 977–979, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21538.
A single‐input single‐chain dual‐band power amplifier for CDMA mobile application
Authors: Kim Ki Young , Kim Ji Hoon , Park Chul Soon
Published: March 2006

We demonstrate a new structure of the single‐input single‐chain power amplifier for cellular (850 MHz)/PCS (1750 MHz) dual‐band operation. The single‐input structure seems adequate for the reconfigurable multiband transmitter and the single‐chain structure can achieve a small chip and module size, thus reducing manufacturing costs. This two‐stage amplifier has a maximum output power of 30 dBm (29 dBm), a power‐added efficiency (PAE) of 42% (37%), and an adjacent channel power ratio (ACPR) of −51 dBc (−48 dBc) at the output power of 28 dBm (28 dBm) under 3.4‐V operation voltage for cellular (PCS) band. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 981–983, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21540
Theoretical investigation of metallic elliptically periodic structures using Mathieu functions
Authors: Denidni T. A. , Boutayeb H.
Published: March 2006

In this paper, an analysis of elliptical periodic structures composed of metallic wires is presented. The transmission and reflection coefficients of elliptical frequency‐selective surfaces (FSSs) are calculated by expressing the scattered field via Mathieu functions and by using an elliptical‐wave multiple reflections model. It is shown that when the elliptical period and the focus are constant, elliptical periodic surfaces have the same transmission and reflection coefficients. This work has potential applications for designing directive antennas. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 988–992, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21543
All‐optical data format conversion from WDM to OTDM based on FWM
Authors: Verdurmen E.J.M. , Khoe G.D. , Koonen A.M.J. , de Waardt H.
Published: March 2006

Conversion from 2 × 10 Gb/s NRZ WDM signals to a 20‐Gb/s OTDM signal has been experimentally verified based on four‐wave mixing (FWM) in a highly nonlinear fiber (HNLF) without the need of an extra NRZ‐to‐RZ conversion step. 10‐GHz control pulses are generated by the means of super continuum (SC) generation and are therefore synchronized with each other in time. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 992–994, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21544
Optical correlator employing opto‐VLSI processing
Authors: Aljada Muhsen , Zheng Rong , Alameh Kamal , Al‐Begain Khalid
Published: March 2006

We propose a novel optical correlator employing an Opto‐VLSI processor in conjunction with an array of fibre Bragg gratings with different Bragg wavelengths for optical header recognition. The recognition of 5‐bit optical header patterns is experimentally demonstrated at 2.27 Gb/s. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 995–997, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21545
High‐dynamic‐range C+L band variable optical attenuator using a titled angle shutter
Authors: Liaw Shien‐Kuei , Lai Ying‐Tse , Chang Ming‐Hung , Lai Yi‐Gun
Published: March 2006

A high‐dynamic‐range variable optical attenuator (VOA) using a movable shutter, which moves in a tilted‐angle direction to the collimate fiber pair, is proposed. The VOA operates in the C+L band with the advantages low cost, high dynamic range of more than 50 dB, low insertion loss of 0.8 dB, low wavelength‐dependent loss (WDL), and low polarization‐dependent loss of ±0.4 dB and 0.4 dB, respectively, with attenuation of 50 dB. A compact size of 5.0 × 1.5 × 1.5 cm is obtained. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1000–1002, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21547
To extend delivery distance of the optical MM‐wave generated by DSB modulation and vestigial sideband filtering
Authors: Yu Jianguo , Yu Jianjun , Chang Gee Kung
Published: March 2006

Due to RF fading effect caused by fiber dispersion in standard single‐mode fiber (SSMF), the maximum delivery distance in SSMF for the optical millimeter (mm)‐wave signals generated by the double‐sideband modulation scheme is shorter than 2 km at a power penalty of 2 dB. We experimentally demonstrate that the maximum transmission distance can be largely extended after using vestigial sideband (VSB) filtering. When we use VSB filtering technique, the transmission distance for the mm‐wave signals is extended more than 40 km at a power penalty of 2 dB. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1003–1004, 2006; Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/mop.21548
Electron spin resonance study of radicals generated in cellulose/N‐methylmorpholine solutions after flash photolysis at 77 K
Authors: Konkin A. , Wendler F. , Roth H.‐K. , Schroedner M. , Bauer R.‐U. , Meister F. , Heinze T. , Aganov A. , Garipov R.
Published: March 2006

The processes of radical formation in N‐methylmorpholine‐N‐oxide monohydrate (NMMO) and cellulose/NMMO solutions were studied by ESR at 77 K under high‐power UV (λ = 248 nm) excimer laser flash photolysis. Radicals mainly generated were attributed to the nitroxide type radicals CH2NO•CH2and CH2NO•CH3 at the first step and methyl •CH3 and formyl •CHO radicals at the second step of the photoreaction. Kinetic studies of these radicals revealed that formation and recombination rates of the radicals depend on the cellulose concentration in cellulose/NMMO solutions and the concentration of additional ingredients, e.g. Fe(II) and propyl gallate. Even at frozen state temperature, acceleration or quenching of radical reaction processes was found. The proposed scheme of UV light‐induced NMMO degradation during irradiation based on ESR data correlates well with independently obtained results based on high‐performance liquid chromatography (HPLC). The analysis of degradation products by HPLC, e.g. aminoethanol and acetaldehyde, supports the assumption concerning a radical‐initiated ring opening of NMMO. Copyright © 2006 John Wiley & Sons, Ltd.
Influence of the spatial position of a trifluoromethyl group on the 13C chemical shifts in the cyclohexane series
Authors: Carcenac Yvan , Diter Patrick , Wakselman Claude , Tordeux Marc
Published: March 2006

The influence of the introduction of a trifluoromethyl group on the 13C chemical shifts in cyclohexane was examined. The two main effects observed are located at the α and γ positions relative to the carbon bearing the fluorine atoms. By comparison of the collected data it was possible to calculate the increments corresponding to the substitution of a hydrogen atom by a CF3 group at axial or equatorial positions on the cyclohexane ring. Copyright © 2006 John Wiley & Sons, Ltd.