bluuebunny/crossref_metadata_2025 huggingface dataset:
Low voltage‐low power full‐band UWB receiver front‐end
Authors: Lee Ji‐Young , Yun Tae‐Yeoul
Published: December 2012

This article proposes a low‐voltage, low‐power, low‐noise, wideband receiver front‐end consisting of a low‐noise amplifier (LNA) and a mixer. The LNA stage uses a current‐reuse technique for low‐power consumption and high gain. A switched biasing technique is then used to reduce the flicker noise of the mixer. A bulk injection structure is adopted for low‐voltage operation of the mixer. The proposed receiver front‐end achieves input impedance matching of less than −10 dB from 3.1 to 10.6 GHz, a minimum noise figure of 4.9 dB, and a maximum power gain of 17.7 dB while consuming 8.25 mW from 6.87 mA and 1.2 V. This receiver front‐end is fabricated using a 0.18‐μm CMOS process. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:278–281, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27299
Compact single‐feed circular slot antenna with asymmetrical C‐shaped strips for WLAN/WiMAX triband and circular/elliptical polarizations
Authors: Wei Chia‐Yen , Liu Ji‐Chyun , Bor Sheau‐Shong , Hung Tian‐Fu , Chen Chi Chiang
Published: December 2012

This article presents a novel triband circular/elliptical polarized single‐feed circular slot antenna for wireless local area network and worldwide interoperability for microwave access systems. The proposed antenna is constructed with two asymmetrical C‐shaped strips facing in opposite directions and embedded in the circular slot and the enhanced feed strip of coplanar waveguide. By way of adjusting the relevant parameters, we can obtain the triband responses at 2.4, 3.5 and 5.25 GHz, respectively. The circular/elliptical polarizations (CP/EP) of each band are presented. The measured −10 dB return loss impedance bandwidth are 270 MHz (11.1%) for 2.4 GHz band, 380 MHz (11.0%) for 3.5 GHz band, and 290 MHz (5.6%) for 5.25 GHz band. The −3 dB axial ratio bandwidth for each band are 10.4, 5.7, and 2.9%, the polarization of radiation patterns are right‐hand CP, right‐hand EP, and left‐hand CP and the antenna gain are 3.2, 4.3, and 5.2 dBic, respectively. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:272–278, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27300
Measurement accuracy enhancement using an optical probe system for electrically small MIMO antennas
Authors: Chung Jae‐Young , Hong Wonbin
Published: December 2012

Well‐known measurement inaccuracy issues for electrically small multiple‐input–multiple‐output (MIMO) antennas incurred by conventional metallic cable and feed effects are mitigated by adopting an optical probe based measurement method.To demonstrate this, a closely packed MIMO antenna consisting of a pair of spirally wound antenna elements is designed and characterized using both the metallic cable feeding and the optical probe feeding methods. The measured MIMO antenna parameters, such as envelope correlation, radiation efficiency, and diversity gain, ascertain significantly improved agreement with simulation, when the optical probe feeding method is used. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:238–241, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27302
User effect comparison between metal bezel antenna and planar inverted F‐antenna for mobile terminal
Authors: Sonkki M. , Berg M. , Antonino‐Daviu E. , Cabedo‐Fabrés M. , Ferrando‐Bataller M. , Salonen E. T.
Published: December 2012

This article presents a novel metal bezel antenna structure and its performance in user vicinity. The antenna is designed by keeping in mind the insensitivity in usage environments. In the antenna structure, a mobile chassis and a bezel are combined as one antenna element. Symmetrical feeding is used to excite the antenna. The characteristics of the metal bezel are compared with those of a conventional planar inverted‐F antenna in terms of user effect at E‐GSM band (880–960 MHz). Both antennas are measured and compared with four different hand phantom grips representing a browsing mode. The grips are designed so that the chassis is under the hand phantom in different variable usage conditions. Results are compared in terms of S11, total efficiency, total body loss, radiation efficiency, reflection loss, and in Smith chart presentation. Finally, antenna structures are compared with hand and head phantom measurements representing a calling mode. The comparison is done in terms of average total body loss. The used hand grips are the same as in the case of the hand phantom measurements. © 2012 Wiley Periodicals,v Inc. Microwave Opt Technol Lett 55:316–322, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27306
Dual‐band low‐profile stripline‐fed Z‐antenna
Authors: Othman Mohamed A. , Abuelfadl Tamer M. , Safwat Amr M. E.
Published: December 2012

This letter proposes a new interpretation for the Z‐antenna.It describes the Z‐antenna as an asymmetrically‐fed bent and meandered inductively‐loaded dipole antenna. This explanation provides a simple methodology to design a dual‐band stripline‐fed Z‐based antenna that operates at 1.8 and 2.45 GHz. Measurements and EM simulations validate the proposed theory. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:286–290, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27307
Ge‐doped microstrutured fiber design by genetic algorithm for directional coupling
Authors: da Silva José Patrocínio
Published: December 2012

A new design of a microstructured optical fiber using cylindrical perfectly matched layers is proposed and analyzed through the vectorial beam propagation method (VBPM) in conjunction with genetic algorithm (GA). The fiber is made up from silica doped with germanium and it contains two and three identical horizontals cores surrounded by air holes. First, the signal power launched in the left core is completely transferred to the neighbor core with 100% of the coupling ratio. Next, the signal power launched in the central core is equally divided between the two neighboring cores with 50% of the coupling ratio. Through numerical simulations, it is demonstrated that the optical power can be completely transferred for a propagation distance around 6000 μm to the first application and 4000 μm to the second application. The behavior of the resulting geometry has been optimized by a genetic algorithm in conjunction with an efficient vectorial finite element formulation (GE‐VBPM). © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:281–285, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27308
A low‐voltage varactorless LC‐VCO in 65‐NM CMOS technology
Authors: Lee Hui Dong , Jung Jong Ho , Lee Kwang Chun
Published: December 2012

A varactorless LC‐voltage‐controlled oscillator (VCO) topology is proposed.To exploit a frequency tuning, LC‐VCO adopts a variable capacitance block composed with a transistor and a capacitor. The prototype LC‐VCO is implemented in a 65‐nm CMOS technology. The measurement results show a tuning range of 4.31–4.45 GHz and a phase noise of −115.8 dBc/Hz at 1 MHz offset frequency. Power consumption is 2.44 mA from a 0.5 V supply. The die area is only 0.126 mm2. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:245–247, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27310
A simple and efficient method to design electromagnetic band gap grids
Authors: Sartori Eduardo Jose , Hernández‐Figueroa H.E.
Published: December 2012

This paper presents a simple design method for behavior of metamaterials of metallic rods. Numerial and experimental results are given. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:421–425, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27311
A dual‐band dual‐element compact MIMO antenna system for mobile 4G terminals
Authors: Sharawi M. S.
Published: December 2012

A novel dual‐band four‐shaped printed multiple‐input‐multiple‐output (MIMO) antenna system for long‐term evolution portable terminals is proposed. The low‐frequency band covered is 780–840MHz and the high‐frequency band covered is 2642–2858MHz. The overall size of the printed MIMO antenna system was 50 × 67 × 1.56 mm3. The maximum measured gain for the low and high bands was ∼0 dBi. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:325–329, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27313
Isosceles triangular unequal power divider
Authors: Ray Sudhabindu , Kumar Girish
Published: December 2012

A three‐port two‐way isosceles triangular microstrip unequal power divider configuration has been proposed for broadband and direct coupled applications. An isosceles triangular microstrip patch is fed at the vertex of one of its equal angles and unequal power division has been obtained at the other two vertices. Unequal power division from –6.2 to –15.9 dB has been achieved by varying the height of the triangular patch. This configuration has been analyzed using transmission line model and commercially available ie3d software, followed by experimental verifications. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:254–258, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27314
Indoor wireless power transfer using asymmetric directly‐strong‐coupling mechanism
Authors: Sun Tianjia , Xie Xiang , Li Guolin , Gu Yingke , Wang Zhihua
Published: December 2012

This letter proposes a new wireless power transfer mechanism named the directly‐strong‐coupling.It adopts only two resonators and it achieves strong‐coupling performances. Asymmetric sizes of antennas are designed to reduce the receiver's size for indoor applications. The mechanism remains a power efficiency of 35.6% over a distance of 1 m. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:250–253, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27315
Design of pentagonal circular fractal antenna with and without notched‐band characteristics
Authors: Kumar Raj , Choubey P.N.
Published: December 2012

An ultrawideband (UWB) pentagonal circular fractal antenna with notched band is proposed in this article. The antenna is excited using CPW‐feed. The notched band from 5.15 to 5.85 GHz is achieved to avoid interference with the WLAN systems using ring resonator slot on feedline. The experimental result exihibits the UWB from 2.5 to 15.0 GHz except the notched band. A parametric study of antenna has been carried out with respect to length and width of the rectangular ring resonator to adjust the notched band and center frequency. The measured radiation pattern of this antenna is omnidirectional in H‐plane and bidirectional in E‐plane. This antenna is useful for UWB communication system, medical imaging, and vehicular radar. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:430–434, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27316
Compact PCB‐embedded GPS antennas loaded with a coupling strip and lumped elements for mobile phones
Authors: Ahn Jungho , Kim Seunghwan , Byun Joonho , Kim Austin S. , Kim Youngsik
Published: December 2012

This article presents compact global positioning system antennas loaded with a coupling strip and lumped elements for mobile phones. The first antenna proposed (Antenna 1) has a one chip capacitor, whereas the second (Antenna 2) uses both a one chip capacitor and an inductor. The size of Antenna 1 is 5 × 10 mm2, whereas Antenna 2 is 5 × 8 mm2. The radiation patterns are almost omni‐directional and the measured peak gain is 0.5 dBi at 1575 MHz. Both antennas are designed and examined via simulation and experiment. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:363–366, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27317
Miniature stubs‐loaded square open‐loop bandpass filter with asymmetrical feeders
Authors: Maharjan Ram Krishna , Kim Nam‐Young
Published: December 2012

A miniaturized microstrip stubs‐loaded square open‐loop bandpass filter (BPF) with asymmetrical feeder lines is proposed.Using this filter structure, the improved out‐of‐band rejection characteristics and higher transmission zero can be possible. The filter is based on a combination of electric and magnetic couplings in the central open‐gaps of the square loop resonators. Hence, the combined couplings generate an electromagnetic (EM) flux between the two square open‐loop resonators. The maximum coupling can be obtained by adjusting the open‐loop gap, mounting the two open‐loop resonators spacing, and the orientation of loaded‐stubs inside the loop resonators. The asymmetrical port terminals also help to couple EM energy by maintaining 50 Ω impedance matching with input/output devices. The open‐gap between the two loops of the filter structure strongly prohibit to flow DC current and out band signals. In this article, the presented BPF generates 5.85 GHz resonant frequency. The insertion loss (S21) was measured as −1.6 dB, and the return loss (S11) was −24.8 dB. The simulated predictions are quite agreed with the measurement results. The proposed filter can be implemented in the RFID systems. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:329–332, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27318
A narrow‐band high‐temperature superconducting filter with wide upper stopband
Authors: Gong Liming , Wei Bin , Cao Bisong , Dong Shiwei , Dong Yazhou , Yu Hongxi , Jun Li
Published: December 2012

This article presents a novel interdigital capacitor resonator (ICR), which has a high spurious frequency and compact size. A six‐pole high‐temperature superconducting (HTS) bandpass filter (BPF) has been designed and fabricated with this ICR on a double‐sided MgO‐based YBCO thin film. Measurement at cryogenic temperature shows a fractional bandwidth of 0.4%, and an ultra high spurious passband at about 4.1 f0. Moreover, the measurement shows a good agreement with simulation in wideband response. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:443–447, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27324
Modified broadband quasi‐Yagi antenna with enhanced gain and bandwidth
Authors: Lee Jong‐Ig , Yeo Junho
Published: December 2012

This article presents a method for improving the gain and bandwidth of a microstrip‐fed broadband planar quasi‐Yagi (QY) antenna.To obtain a better and more stable gain with little variation over a broad frequency band, we used a planar QY antenna with strip‐type elements (a driver dipole and two directors) that had unequal widths and unequal spacing between them. First, to achieve a broad bandwidth of over 50%, a wide strip is used as a nearby director placed very close to the driver dipole. Then, to enhance and stabilize gain over a required frequency band, a narrow strip director and a ground reflector are appended to the driver with a nearby parasitic director. We systematically explain the effect of each element on the input impedance and the realized gain. To validate this proposed design, a QY antenna with a frequency band from 1.75 to 2.7 GHz and a gain of over 5 dBi was designed, then fabricated on an FR4 substrate, and tested. The results show that the fabricated antenna performs well, with a broad bandwidth of 60.4% (1.53–2.85 GHz), a stable gain between 5.38 and 6.41 dBi, and a front‐to‐back ratio of over 10 dB. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:406–409, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27325
Compact composite right‐ and left‐handed bandpass filter with interlocked gap coupling
Authors: Jang Geonho , Kahng Sungtek
Published: December 2012

We propose a novel compact bandpass filter having a mushroom with interlocked gap coupling on FR4 as a composite right‐ and left‐handed structure. The physical size reduction is made possible by the zeroth‐order resonance of the geometry. The stopband suppression >40 dB is obtained by creating transmission zeros implemented with open stubs at ports. The passband has insertion loss < 1.5 dB and return loss < −15 dB at WiMAX‐band. The simulation and measurement validate the design. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:403–405, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27326
Compact microstrip stepped‐impedance resonator (SIR) using localized substrate integrated artificial dielectric (L‐SIAD)
Authors: Wang Xiaoke , Tang Wanchun , Chow Y.Leonard
Published: December 2012

This article presents a stepped‐impedance resonator (SIR) using microstrip line on localized substrate integrated artificial dielectric (L‐SIAD) structure. In L‐SIAD, the metal posts are periodically embedded in the lower substrate right under the microstrip line and connected to the ground plane, which results in the increasing of the effective permittivity and reduction of the SIR size, especially in the length of the SIR. The resonant frequencies of this SIR are analyzed for different post diameter, post height, and post period. Furthermore, the electromagnetic bandgap property due to the periodical posts is also studied, especially the influences on the resonant frequencies of the SIR. In final, this SIR is used to design an ultra‐wideband bandpass filter and the measured results demonstrated that the filter has broad upper stopband, low insertion loss in passband, and compact size. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:371–375, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27327
Compact ultra‐wideband CPW‐fed fan‐shaped antenna with dual band‐notched characteristics using ARC‐shaped slots
Authors: Wang Chen , Yan Ze‐Hong , Li Sheng
Published: December 2012

In this article, a compact coplanar waveguide‐fed fan‐shaped monopole antenna for ultra‐wideband applications with dual band‐notched characteristics is proposed and studied. The antenna with fan‐shaped structure occupies a small size of 35 × 30 mm2. With a pair of arc‐shaped slots introduced on the radiating patch, two frequency‐notched responses at 3.5/5.5 GHz are obtained. The antenna structure is designed, fabricated, and tested. The band‐notched characteristics, VSWR, radiation patterns, gains within the operating band have been observed. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:368–371, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27328
Miniaturized frequency selective surface with a bionical structure
Authors: Jiang Wen , Hong Tao , Gong Shu‐xi , Li Cheng‐kai
Published: December 2012

A novel miniaturized frequency selective surface (FSS) is proposed.The size reduction is achieved by using the model of leaf arrangement. Compared with conventional cross FSS, the operation frequency of this novel bionic FSS is changed from 10.4 to 4.74 GHz at the same size. Both theoretical and experimental investigations are carried out. It is observed that the miniaturized FSS presents excellent frequency stability with the increase of the incident angle. The proposed FSS can be a candidate for FSS whose miniaturization is required. Method of applying bionics to FSS design will serve as a good candidate for the future FSS design. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:335–337, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27329
DC‐50 GHz RF‐MEMS SPDT switch for high‐reliability applications
Authors: Matabosch Nuria Torres , Coccetti Fabio , Reig Bruno , Deborgies François , Diepppedale Christel , Sibuet Henri , Cazaux Jean Louis
Published: December 2012

A large band SPDT (single‐pole double‐throw) switch based on a very advanced RF‐MEMS switch technology for redundancy schemes are presented. This device allowed to reach state‐of‐the‐art working bandwidth (DC‐50 GHz) and RF performances (IL (Insection loss) < 0.8 dB, isolation > 25 dB, and RL > 20 dB). The 200 mm MEMS technology process has demonstrated a very good stability with very low dispersion (deviations < 0.05 dB for the IL and < 0.6 dB for the isolation over the entire wafer and frequency range). An accurate electrical equivalent circuit, modeling the SPDT in the DC‐65 GHz frequency band, has allowed to extract a contact resistance which is as low as 1.4 Ω. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:333–335, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27330
A compact wideband strip antenna for wireless USB dongle application
Authors: Liu Wen‐Chung , Chen Yung‐Lun , Wu Chao‐Ming
Published: December 2012

A wideband strip antenna easy for integration with the printed circuit board of a wireless universal serial bus dongle is presented.By simply inserting slots into a rectangular patch, dual resonances with a wide continuous bandwidth of 1.98 GHz (2.9–4.88 GHz) are obtained. The antenna comprising dual‐folded strips and fed by a short microstrip line is simple and has a compact size of only 9.5 × 10 mm2. Prototypes of this design have been constructed and verified to show good agreement between the simulated and measured results. In addition, design evolution of the presented antenna is performed to provide insights into the antenna‐operating mechanism. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:302–304, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27331
Radiofrequency resonance heating near medical devices in magnetic resonance imaging
Authors: Brown James E. , Lee Choon S.
Published: December 2012

Magnetic resonance imaging (MRI) is a desirable diagnostic modality because of its excellence soft‐tissue imaging capability. Patients with implanted medical devices are presently denied access to this modality due to adverse interaction of the device with the electromagnetic fields of the MRI system. These adverse interactions include heating near the tissue–electrode interface due to the radiofrequency (RF) field. The purpose of this work is to develop a basic model of the resonance to further explain the mechanism of RF heating in MRI near implanted medical devices. The work will concentrate on simplified structures that can be well understood from an analytical approach. The relationships shown in the simplification can then be extended to the more complex geometry of an implanted lead. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:299–302, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27332
An improved full scanning antenna using left‐handed materials
Authors: Upadhyay Dileep Kumar , Pal Srikanta
Published: December 2012

An improved version of full scanning antenna using left‐handed metamaterial is reported in this article. The antenna profile is designed based on microstrip technology using balanced composite right left handed transmission lines (CRLH TL) approach. Conventional LC network representation of the CRLH TL uses cascaded combination of interdigital capacitor (IDC) in series and vias to the ground plane at the stub ends in shunt, whereas in this article, the design of full scanning antenna using wire‐bonded IDC is reported and its performance is compared with conventional IDC based full scanning antenna. Dispersion diagram of the balanced CRLH TL based dominant mode leaky wave antenna shows the capability of backfire (−90° < θ < 0°) to broadside (θ = 0°) and to endfire (0° < θ < 90°) scanning. Radiation patterns confirm the full scanability of the antenna and it also shows the designed structure has reduced sidelobes in the endfire radiations. Simulated and measured return loss characteristics of the reported antenna structure show an increase in the antenna's operational bandwidth. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:261–265, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27333
Wideband planar microstrip crossover with high power handling capability and low distortion
Authors: Henin Bassem , Abbosh Amin
Published: December 2012

The design of a planar four‐port microstrip crossover is presented. The design starts by using a half‐wavelength square patch and two sets of orthogonal feeding lines. To achieve a wideband performance, four circular slots are introduced in the square patch. A parametric analysis is used to investigate the effect of the utilized slots. Full‐wave simulations and measurements are used to validate the proposed design. The simulated and measured data show less than 1 dB insertion loss, more than 10 dB return loss, more than 19 dB isolation, and about 0.2 ns group delay deviation across the band from 2.1 to 2.75 GHz. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:439–443, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27335
Nine‐element frequency independent dielectric resonator array for X‐band applications
Authors: Kumari Runa , Behera Santanu Kumar
Published: December 2012

A frequency independent dielectric resonator array (FIDRA) is designed and investigated experimentally for X‐band applications.In this proposed array, nine rectangular shaped dielectric resonators are arranged in log periodic fashion to attain electrical characteristics which will vary insignificantly with frequency over the entire desired bandwidth. The resulted frequency independent array offers up to 56% wider impedance bandwidth with a VSWR less than two. The bandwidth achieved by proposed FIDRA covers a frequency range 6.3–11.2 GHz which is the desired frequency range for X‐band applications in communication engineering. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:400–403, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27337
Aperture‐coupled pentagon shape dielectric resonator antennas providing wideband and multiband performance
Authors: Sharma Satish K. , Brar Manveer K.
Published: December 2012

The aperture‐coupled regular and irregular pentagon‐shaped dielectric resonator antennas (DRAs) are presented providing wideband and multiband performances. The regular and irregular pentagon shape DRAs show wideband impedance matching (S11 = −10 dB) bandwidth of 42% (from 2.55 to 3.9 GHz) and 45.8% (from 2.57 to 4.1 GHz), respectively. Further, the irregular pentagon shape DRA also shows triple bands: 2.42–2.61 GHz (Band 1), 3.15–4.05 GHz (Band 2) and 5–5.65 GHz (Band 3) with a percentage matching bandwidths of 7.55, 23.77, and 12.2%, respectively. These DRAs offer acceptable directional radiation patterns for both wideband and multiband performances. Prototype of the regular pentagon shape DRA has been fabricated and experimentally verified for both the matching bandwidth and radiation performance. The simulated and measured results are in very good agreement. These DRAs can find applications in wireless communications devices such as base stations. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:395–400, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27338
Embodiment of high impedance surface using artificial magnetic conductor with periodically rectangular lattices
Authors: Lee Seungwoo , Kim Nam , Rhee Seungwoo
Published: December 2012

We designed a new transformed symmetrical mushroom‐like surface structure that possesses high impedance surface characteristics by using periodically arrayed artificial magnetic conductors (AMCs) without via holes.The slots that play a key role in the proposed structure were controlled and optimized by simulation for obtaining the desired frequency band. To evaluate the performance, we used the proposed AMC structure as a reflector of λ/4 dipole antenna, whose resulting characteristics were proven that the distance between the antenna and the proposed AMC reflector is about 12 mm at 2.4 GHz, less than one tenth of a wavelength, without deteriorating the antenna performance. The designed reflector has a broader bandwidth (12.6%) and smaller size (0.16 λ) compared to conventional energy band gap (EBG) structures. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:366–368, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27339
The use of exchangeable nuclei to observe enantiomers through deuterium NMR in chiral liquid crystalline solvents
Authors: Palomino Martina , Khudr Hussein , Courtieu Jacques , Merlet Denis , Meddour Abdelkrim
Published: December 2012

It is demonstrated that 2H NMR in chiral liquid crystalline solvents can be used to measure enantiomeric excesses using exchangeable deuterons in alcohols. This is performed in a trivial way at low temperature (260–270 K) where a slow exchange regime was reached. Among the various alcohols used to explore the possibilities of this technique, an unusually large isotopic effect on molecular orientation between two isotopomers has been observed. Copyright © 2012 John Wiley & Sons, Ltd.
Influence of solvent and salt concentration on the alignment properties of acrylamide copolymer gels for the measurement of RDC
Authors: Trigo‐Mouriño Pablo , Navarro‐Vázquez Armando , Sánchez‐Pedregal Víctor M.
Published: December 2012

The dependence of molecular alignment with solvent nature and salt concentration has been investigated for mechanically stretched polyacrylamide copolymer gels. Residual dipolar couplings (RDCs) were recorded for D2O, DMSO‐d6, and DMSO‐d6/D2O solutions containing different proportions of the solvents and different sodium chloride concentrations. Alignment tensors were determined by fitting the experimental RDCs to the DFT‐computed structure of N‐methylcodeinium ion. Analysis of the tensors shows that the degree of alignment decreases with the proportion of DMSO‐d6 as well as with the concentration of sodium chloride, most likely due to enhanced ion‐pair aggregation. Furthermore, rotation of the alignment tensor is observed when increasing the salt concentration. Copyright © 2012 John Wiley & Sons, Ltd.
Phenylalanine‐based polyarylacetylenes as enantiomer‐differentiating alignment media
Authors: Krupp Alexis , Reggelin Michael
Published: December 2012

Lyotropic liquid crystalline phases of a phenylalanine‐based polyacetylene are introduced as new enantiodifferentiating alignment media. Based on the unusual temperature dependence of the quadrupolar splitting of the 2H‐signal of the solvent (CDCl3), three distinct states of the phase with different orientational properties can be identified. This offers the opportunity to measure multiple alignment data sets without changing the sample. Unexpectedly, the largest difference in the orientation of the enantiomers of isopinocampheol was found in the high temperature domain of the phase. This is even more astonishing because the helical structure of the polymer backbone seems to break down at temperatures above approximately 10°C, leaving the stereogenic centers of the amino acid moieties in the repeating units as the only reason for the enantiodifferentiation. Copyright © 2012 John Wiley & Sons, Ltd.
New strategy for RDC‐assisted diastereotopic proton assignment using a combination of J‐scaled BIRD HSQC and J‐scaled BIRD HMQC/HSQC
Authors: Snider Jonathan D. , Troche‐Pesqueira Eduardo , Woodruff Shannon R. , Gayathri Chakicherla , Tsarevsky Nicolay V. , Gil Roberto R.
Published: December 2012

A new strategy to assign diastereotopic protons was developed on the basis of residual dipolar couplings (RDCs) collected in compressed poly(methyl methacrylate) (PMMA) gels. A combination of 2D J‐scaled BIRD HSQC and J‐scaled BIRD HMQC/HSQC NMR experiments was used to collect the RDC data. In the proposed strategy, the first experiment is used to measure 1DCH for methine groups, the sum of 1DCHa + 1DCHb for methylene groups and the average 1DCH3 value for methyl groups. In turn, the small molecule alignment tensor is calculated using these D values without the a priori assignment of CH2 diastereotopic protons. The D values of each individual CH bond (CHa and CHb) of each methylene group in the molecule are then predicted using the calculated alignment tensor and these values compared with the results from the HMQC/HSQC experiment, leading to their unambiguous assignment. This strategy is demonstrated with the alkaloid strychnine that contains five methylene groups with diastereotopic protons, and our results fully agree with the previously reported assignment using combinations of permutated assignments. Copyright © 2012 John Wiley & Sons, Ltd.
Configuration verification via RDCs on the example of a tetra‐substituted pyrrolidine ring
Authors: Tzvetkova Pavleta , Luy Burkhard , Simova Svetlana
Published: December 2012

The configurational analysis of organic compounds is an important application for high resolution NMR spectroscopy. In the present study, a tetra‐substituted pyrrolidine with four chiral carbon atoms is analyzed using classical methods based on 3J and NOE data in solution and compared and verified with recently introduced alternative approaches via residual dipolar couplings (RDCs) in two weak anisotropic alignment media. The molecule shows sufficient rigidity in the five‐membered ring for the configurational characterization with the various techniques. However, the flexibility caused by the many freely rotating bonds potentially poses problems for the interpretation of data. It is shown that RDCs measured in poly‐γ‐benzyl‐l‐glutamate and a stretched polydimethylsiloxane gel provide useful information for the distinction of diastereomers, but the success varies with the data interpretation strategy used. Although a general improvement of corresponding correlation factors is observed when limiting data to a subset of dipolar couplings directly connected to the central ring, the distinction power is reduced because of the smaller number of RDCs available for potential model falsification. Singular value decomposition for fitting experimental RDCs is able to distinguish in most cases the correct from incorrect configurations, but the differences in correlation factors can be relatively small. Surprisingly, predicting RDCs using the rod model as implemented in PALES gives best results in distinguishing the eight possible diastereomers. It is also found that the use of proton–phosphorus and carbon–phosphorus RDCs helps with the configurational analysis of the model compound. Copyright © 2012 John Wiley & Sons, Ltd.
Chemical shifts of phenolic monomers in solution and implications for addition and self‐condensation
Authors: Haupt Robert A. , Renneckar Scott
Published: December 2012

Alkali metal counter‐cations alter the electron density of phenolates in solution by electrostatic interactions. This change in electron density affects their reactivity toward formaldehyde, hydroxymethylphenols, and isocyanates during polymerization. The electronic perturbation of phenolic model compounds in the presence of alkali metal hydroxides was investigated with 13C and 1H nuclear magnetic resonance in polar solvents relative to non‐ionic controls, altering the chemical shifts of the model compounds, thus indicating changes in electron density using the chemical shift as a proxy. These shifts were attributed to Coulombic electrostatic interactions of the counter‐cation with the phenolate anion that correlated to hydrated ionic radius and solvent dielectric constants. The predicted relative reaction rates for formaldehyde addition based on electron density ranking from 13C nuclear magnetic resonance of the phenolic models was compared with the literature values. Predictions for condensation reactions of 2‐ and 4‐hydroxymethylphenol from chemical shifts were consistent with published results. The results permit predictions for the reaction of phenolic compounds for the formation of thermosetting polymeric materials. Copyright © 2012 John Wiley & Sons, Ltd.
Quality Indicators for Physiotherapy Care in Hip and Knee Osteoarthritis: Development and Clinimetric Properties
Authors: Peter W. F. , van der Wees P. J. , Hendriks E. J. M. , de Bie R. A. , Verhoef J. , de Jong Z. , van Bodegom‐Vos L. , Hilberdink W. K. H. A. , Vliet Vlieland T. P. M.
Published: December 2012

Objective

The aim of the present study was to develop process quality indicators for physiotherapy care based on key recommendations of the Dutch physiotherapy guideline on hip and knee osteoarthritis (OA).

Methods

Guideline recommendations were rated for their relevance by an expert panel, transformed into potential indicators and incorporated into a questionnaire, the Quality Indicators for Physiotherapy in Hip and Knee Osteoarthritis (QIP‐HKOA). Adherence with each indicator was rated on a Likert scale (0 = never to 4 = always). The QIP‐HKOA was administered to groups of expert (n = 51) and general (n = 134) physiotherapists (PTs) to test its discriminative power. Reliability was tested in a subgroup of 118 PTs by computing the intraclass correlation coefficient (ICC). QIP‐HKOA items were included if they were considered to be related to the cornerstones of physiotherapy in hip and knee OA (exercises and education), had discriminative power and/or if they were followed by <75% of PTs in both groups.

Results

Nineteen indicators were derived from 41 recommendations. Twelve indicators were considered to be the cornerstones of physiotherapy care; six indicators had discriminative power and/or were followed by <75% PTs in both groups, resulting in an 18‐item QIP‐ HKOA. The QIP‐HKOA score was significantly higher with expert [60.73; standard deviation (SD) 5.67] than with general PTs (54.65; SD 6.17) (p < 0.001). The ICC of the QIP‐HKOA among 46/118 PTs was 0.89.

Conclusion

The QIP‐HKOA, based on 18 process indicators derived from a physiotherapy guideline on hip and knee OA was found to be reliable and discriminated between expert and general PTs. Its ability to measure improvement in the quality of the process of physiotherapy care needs to be further examined. Copyright © 2012 John Wiley & Sons, Ltd.
New bounding techniques for goal‐oriented error estimation applied to linear problems
Authors: Ladevèze P. , Pled F. , Chamoin L.
Published: December 2012

The paper deals with the accuracy of guaranteed error bounds on outputs of interest computed from approximate methods such as the finite element method. A considerable improvement is introduced for linear problems, thanks to new bounding techniques based on Saint‐Venant's principle. The main breakthrough of these optimized bounding techniques is the use of properties of homothetic domains that enables to cleverly derive guaranteed and accurate bounding of contributions to the global error estimate over a local region of the domain. Performances of these techniques are illustrated through several numerical experiments. Copyright © 2012 John Wiley & Sons, Ltd.
Surface morphology and raman analysis of the polyimide film aged under bipolar pulse voltage
Authors: Yang Yang , Yin Di , Zhong Chuyu , Xiong Rui , Shi Jing , Liu Zhengyou , Wang Xuan , Lei Qingquan
Published: December 2012

Polyimide film has the weakness of high processing temperature and low corona resistance, which restrain its further development. Kapton 100 HN polyimide films with a thickness of 50 μm were aged by needle‐plane electrode under 4 kV bipolar pulse voltages for 4 h at different frequencies (300—900 Hz). The surface morphologies of the pristine and aged polyimide films were analyzed using an atomic force microscope, and the changes in chemical bonds during corona aging were analyzed by Raman spectra. Different surface morphologies are observed using AFM, and the parameters all have sharp increases, which reveal that the surface morphology is obviously influenced by the corona aging under the bipolar pulse voltage. Raman results show that there are peak shifts and changes of the relative band intensities, which demonstrate that the chemical bonds in the polymer chains are reoriented by the electric field. Moreover, the corona aging of the polyimide film became severe at high frequency. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers
Fabrication of polystyrene/multiwalled carbon nanotube composite films synthesized by in situ microemulsion polymerization
Authors: Patole Archana S. , Patole Shashikant P. , Yoo Ji‐Beom , An Jeong‐Ho , Kim Tae‐Ho
Published: December 2012

A microemulsion polymerization method was used to achieve better compatibility between polystyrene (PS)/multiwalled carbon nanotubes (MWCNTs) nanocomposites and the host PS matrix to form films with excellent electrical and thermal properties. The films were prepared by embedding the PS/MWCNTs nanocomposite into the PS matrix. The MWCNTs were functionalized with PS nanoparticles to avoid the phase separation problem between the filler and host matrix and to enhance the good dispersibility of MWCNTs in the PS host matrix. The confirmation of the synthesis was analyzed by Fourier transform infrared spectroscopy, nuclear magnetic resonance, and Raman spectroscopy. The variation effect of the PS‐linking density on the MWCNT was revealed by scanning electron microscopy and transmission electron microscopy. An enhancement of the thermal and mechanical properties was revealed by thermal gravimetric analysis, differential scanning colorimetric analysis, and dynamic mechanical analysis. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers
Pretreatment of pine needles/wood particles and their composites with isocyanate prepolymer adhesive
Authors: Chauhan Monika , Gupta M. , Singh B. , Bhattacharyya S.K. , Singh A.K. , Gupta V.K.
Published: December 2012

Pine needles and eucalyptus wood particles were treated with 4, 4′ diphenyl methane diisocyanate. The efficacy of treatment was assessed in terms of lowering in the contact angle, the assignment of new absorption peaks and the penetration inside the surfaces. Results indicate that needles were less wettable than the wood particles and also heterogeneitically retained isocyanate on their surfaces. A positive effect in the properties of composites was observed when pine needles were used with the composite adhesive system: monomeric isocyanate for pretreatment and isocyanate prepolymer for particle–particle bonding. Pine needles and wood particles in 50:50 ratio in the panels were optimized. It was found that composites containing both pine needles and wood particles exhibited superior mechanical properties to the composites made solely with the pine needles. During hydrothermal aging, the pine needle composites retained more internal bond strength than those made with the blended fibers. Improved resistance against natural decay was noticed with the sodium pentachlorophenate treatment and exhibiting <10% weight loss in the composites. Toxicity index based on gases emitted during the burning of composites was found in the range of 2.2–3.7 which is considered to be safe in comparison with the other similar materials. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers
Estimation of tensile strength of inorganic plate‐like particulate reinforced polymer composites
Authors: Liang Ji‐Zhao
Published: December 2012

The reinforcing mechanisms of inorganic plate‐like particulate reinforced polymer composites were discussed based on the micro‐mechanical model in this article, and a new expression of tensile strength was derived by introducing an interfacial strength factor. This equation was applied to estimate the tensile strength of inorganic plate‐like particulate reinforced polymer composites. The results showed that the relative tensile strength increased nonlinearly with increasing filler volume fraction. Finally, the equation was verified preliminarily using the measured tensile strength of the mica reinforced poly (aryl ether ketone) composites and mica reinforced polydimethylsiloxane networks reported from literature, good agreement was found between the predictions of the relative tensile strength and the experimental data. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers
Reuse of cured epoxy as a reinforcement in an epoxy composite
Authors: Mohan T.P. , Kanny K.
Published: December 2012

This article discusses the reuse of a thermoset‐based epoxy polymer. In this method, cured epoxy polymer is ground to powder of particle size ranging from 1 to 30 μm. The ground epoxy is then filled in an epoxy polymer to form an epoxy–epoxy composite system using both room and high temperature processing. The amount of filler material was varied from 1 to 10 wt% in the epoxy matrix. Rheology and tensile properties test were then performed. The result shows that the room temperature‐processed epoxy composites (above 5 wt% of powders) resulted in the formation of voids, agglomeration of particles, and reduced degree of cure leading to a decrease in tensile properties. These drawbacks (voids, agglomeration, and low degree of cure) were correspondingly absent in composites processed at high temperature. Results from this work suggest that the thermoset polymer can be reused effectively with minimal changes to the unfilled resin properties. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers
Experimental studies for stability of ferroelectric phase in potassium nitrate composite films
Authors: Kumar Neeraj , Nath Rabinder
Published: December 2012

This article describes the experimental results for the stability of ferroelectric phase III of potassium nitrate (KNO3) at room temperature. To ensure the stability of ferroelectric phase III of potassium nitrate, we have prepared the composite films of potassium nitrate with polyvinyl fluoride (PVF) in the relative amount of 50–50 wt% using melt‐pressing. The structural and electrical properties have been carried out. X‐ray diffraction (XRD) has been used to identify the crystalline phases. The ferroelectric polarization hysteresis loops also show that the value of remanent polarization (Pr) is 5.5 μC cm−2 at room temperature. The switching current transient behavior was also investigated and indicates the presence of ferroelectric phase in the composite films. Capacitance versus temperature (C‐T) measurements have been used to identify the phase transition temperature during heating and cooling, which supports the Curie–Weiss behavior. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers
Recent progress in smart polymer composite particles in electric and magnetic fields
Authors: Liu Ying Dan , Choi Hyoung Jin
Published: December 2012

Electrorheological (ER) and magnetorheological (MR) fluids based on electro‐ and magneto‐responsive particles, respectively, are smart suspensions with the ability to undergo phase transitions from a liquid‐like to a solid‐like state as a result of stimuli of an electric or magnetic field. The application of polymer composite materials rather than pure polymeric or inorganic materials is aiming to solve the problems in the use of both ER and MR materials, such as low activity, physical and chemical stability, and production cost. Various fabrication methods of polymer composite materials with electro‐activity or magneto‐activity developed and effectively applied in this field to boost the wide commercialization of both ER and MR fluids are briefly reviewed in this perspective. © 2012 Society of Chemical Industry
Solar cell efficiency tables (version 41)
Authors: Green Martin A. , Emery Keith , Hishikawa Yoshihiro , Warta Wilhelm , Dunlop Ewan D.
Published: December 2012

Consolidated tables showing an extensive listing of the highest independently confirmed efficiencies for solar cells and modules are presented. Guidelines for inclusion of results into these tables are outlined, and new entries since June 2012 are reviewed. Copyright © 2012 John Wiley & Sons, Ltd.
Modeling of InP Etching Under ICP Cl2/Ar/N2 Plasma Mixture: Effect of N2 on the Etch Anisotropy Evolution
Authors: Chanson Romain , Rhallabi Ahmed , Fernandez Marie Claude , Cardinaud Christophe
Published: December 2012

A 2D Monte‐Carlo etching model of InP by a Cl2/Ar/N2 plasma discharge coupled to our kinetic plasma model and sheath model have been developed. It allows prediction of geometrical and chemical profile of etched trenches versus the operating conditions. The plasma kinetic model is performed to quantify reactive species densities and fluxes of Cl, N, and positive ions. The latter are introduced as input parameters in the etching model. Under Cl2/Ar plasma mixture, the mechanism of bowing development is attributed to chemical desorption of InClx sites. The addition of nitrogen into Cl2/Ar gas mixture outline the role of nitrogen in the formation of a passivated layer on the side wall.

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