bluuebunny/crossref_metadata_2025_split huggingface dataset:
Compact tri‐band monopole antenna with hybrid strips for WLAN/WiMAX applications
Authors: Ren Xueshi , Gao Steven , Yin Yingzeng 
Published: November 2014

ABSTRACTA novel compact microstrip‐fed tri‐band monopole antenna for WLAN and WiMAX applications is presented in this letter. Hybrid Strips including an L‐shaped strip and a meandered strip are used to generate three resonances in the monopole antenna. Due to the use of a meandered line structure, the antenna size is reduced to 38 × 20 × 1 mm3 only. Compared to the existing designs, the proposed antenna has a size 30, 55, and 70% of the designs in [1–3], respectively. To investigate the performance of antenna versus key antenna design parameters, results of a parametric study are presented. Simulated surface current is also shown. To validate the concept, one antenna prototype is implemented and tested, and the measured results show that the antenna can achieve good performance for WLAN 2.4/5.8 GHz and WiMAX 3.5 GHz applications. The antenna has a compact size and is easy for fabrication, hence useful for practical applications. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:94–99, 2015
Experimental proof for pattern reconfigurability of 60‐GHz quasi‐Yagi antenna
Authors: Yang Yi , Chan King Yuk , Nikolic Nasiha , Ramer Rodica 
Published: November 2014

ABSTRACTThis article demonstrates the possibility of designing pattern reconfigurable quasi‐Yagi antenna without compromising antenna's realized gain or operating frequency band. By controlling the length of dipole driven arms and the transition delay line, the E‐plane beam direction of designed antennas are steered from −20° to +20°, in 10° steps. In this communication, five separate 60 GHz antennas with different radiation directions are simulated, fabricated and measured. The experimental results match well the predicted ones and demonstrate that the radiation beam direction of quasi‐Yagi antenna can be freely shifted. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:84–88, 2015
Compact dual‐antenna with π‐shape grounded strip for enhanced bandwidth and decreased coupling for LTE tablet computer application
Authors: Wong Kin‐Lu , Lin Po‐Wei 
Published: November 2014

ABSTRACTA compact dual‐antenna for the long term evolution (LTE) operation in its high band of 1710–2690 MHz is presented for the LTE tablet computer application. The dual‐antenna occupies a small volume of 10 × 45 × 0.8 mm3 and comprises two back‐to‐back folded loops separated by a π‐shape grounded strip. Each folded loop is directly fed to generate its half‐wavelength mode at about 2.6 GHz, and one arm of the π‐shape grounded strip is parasitically excited to provide a quarter‐wavelength resonant mode at about 1.9 GHz. The two resonant modes are formed into a wide operating band of about 1.7–2.7 GHz, which covers the desired LTE high band. Furthermore, the other arm of the π‐shape grounded strip provides a resonant path to direct the excited surface currents on the device ground plane. In this case, the surface currents flowing along the top edge of the device ground plane is greatly suppressed, thereby decreasing the coupling between the two feeding ports of the dual‐antenna. The dual‐antenna provides acceptable isolation better than about 10 dB and good antenna efficiency better than about 55% over a wide operating band of larger than 1 GHz. This leads to acceptable envelope correlation coefficient (<0.3 for the proposed dual‐antenna) obtained for the LTE high‐band (1710–2690 MHz) operation. Operating principle of enhanced bandwidth and decreased coupling of the dual‐antenna is described. Results of the fabricated dual‐antenna are presented, and the MIMO performance of the dual‐antenna is also discussed. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:104–111, 2015
High‐gain series‐fed aperture‐coupled microstrip antenna array
Authors: Mohamed Issa , Sebak Abdel R. 
Published: November 2014

ABSTRACTA 60 GHz high‐gain four‐element series‐fed microstrip patch array antenna is presented. Its feeding mechanism is accomplished through inclined aperture slots in the ground plane. Inclined slot angles were selected to ensure equal feeding to each antenna element. Both simulated and measured results present solid performance with a 4 GHz 2:1 VSWR impedance bandwidth with 87% overall efficiency. The array exhibits maximum realized gain of 12.5 dB, which makes it a good candidate for millimeter‐wave systems and imaging applications. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:91–94, 2015
Design of compact triple‐passband microwave filters based on stepped impedence resonators
Authors: Tsai Lin‐Chuan 
Published: November 2014

ABSTRACTIn this letter, a novel coupling configuration for a stepped impedance resonator (SIR) is proposed and used in the design of triple‐passband filters with a small circuit. The filter was designed to have higher selectivity by manipulating direct coupling, input, and output external quality factors of the SIR. The second and third resonant frequencies can be tuned by adjusting the structural parameters. To verify the proposed configuration, triple‐passband Chebyshev filters were designed and implemented using microstrip lines. The consistency between the measured results and full‐wave simulation prediction validated that the configuration of the proposed filters is feasible. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:124–127, 2015
Inverse scattering approach with measurement of only total electric field
Authors: Moriyama Toshifumi , Takenaka Takashi 
Published: November 2014

ABSTRACTAn inverse scattering approach using only total electric field data is developed for reconstructing electrical parameters of unknown scatterers. Two interior boundary value problems are set up whose solutions coincide with each other if and only if a medium inside the observation surface is the same as that of the original scattering problem. A cost functional of misfit between the two solutions is introduced to solve the inverse problem and its gradient is derived explicitly. Numerical examples are provided to assess the proposed inversion approach. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:137–141, 2015
Very‐low‐profile dual‐wideband loop antenna for LTE tablet computer
Authors: Wong Kin‐Lu , Chen Meng‐Ting 
Published: November 2014

ABSTRACTA very‐low‐profile (8 mm in height), small‐size (8 × 3 × 40 mm3), and dual‐wideband loop antenna suitable for applications in the LTE tablet device such as a tablet computer is presented. Dual‐wideband operation of the proposed loop antenna is achieved using a wideband feed structure formed by a coupling feed, a high‐pass matching circuit, and a tuning inductor. The coupling feed leads to successful excitation of a quarter‐wavelength loop mode in the desired lower band. The high‐pass matching circuit causes an additional resonance occurred near the excited quarter‐wavelength loop mode to widen the low‐band bandwidth to cover the 698–960 MHz band. The tuning inductor can adjust the frequency ratio of the first two higher‐order loop modes to form a wide higher band to cover the 1710–2690 MHz band. Dual‐wideband operation of the proposed loop antenna for the LTE operation is hence obtained. Details of the proposed loop antenna are addressed. Working principle of the antenna, especially the function of the wideband feed structure thereof, is described. Experimental results of the fabricated prototype are also presented. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:141–146, 2015
Slot meander spurline bandstop filter using integrated passive device technology
Authors: Shrestha Bhanu , Kim Nam‐Young 
Published: November 2014

ABSTRACTA slot meander spurline bandstop filter (BSF) is designed, fabricated, and characterized on a semi‐insulating‐GaAs substrate with a thickness of 625 µm and a dielectric constant of 12.85 using integrated passive device technology. The BSF is resonated at 5.44 GHz for wireless local area network applications. The purposed bandstop is built with slot meander spurlines and symmetrically folded T‐type slot lines that provide excellent S‐parameter responses. The measured insertion loss (S21) and return loss (S11) are −28.7 and 0.7 dB, respectively, with a 3‐dB fractional bandwidth of 11%. The experimental results nearly have a good agreement with the simulation results. The overall dimension of the proposed BSF is (1966 × 4984) µm2. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:168–172, 2015
Impact analysis on distance variation between patch antenna and metamaterial
Authors: Katiyar Pankaj , Liza Wan Mahadi Wan Nor 
Published: November 2014

ABSTRACTMetamaterials are artificially engineered material having negative permittivity and permeability. Due to their negative constitutive parameters, metamaterials are capable of focusing incident electromagnetic energy called as beam focusing property. We have made use of beam focusing property of metamaterial to enhance antenna far‐field gain. We have also conducted experimental study by varying the distance between patch antenna and metamaterial array to determine optimum distance. The distance is varied in seven steps of 35 mm. The far‐field gain of antenna is increased by 4 dB when metamaterial is placed at 95 mm. The beamwidth of antenna reduces when loaded with metamaterial indicating beam sharpening. At 155 mm from patch antenna, the beamwidth reduces to 33.95° and starts increasing as metamaterial is moved further away. The resonance frequency and bandwidth of antenna follows alternate increase and decrease pattern as the distance of metamaterial is increased, however, the impact is negligible. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:178–183, 2015
Compact wide‐stopband planar diplexer based on rectangular dual spiral resonator
Authors: Bukuru Denis , Song Kaijun , Xue  
Published: November 2014

ABSTRACTA Compact wide‐stopband planar diplexer based on rectangular dual spiral resonator (RDSR) is proposed. The proposed diplexer is composed of three parts: (1) two RDSR bandpass filters (BPFs) with right bend open‐circuited stubs coupling feed structure, (2) open‐circuited stub to reduce the second harmonic in upper stopband, and (3) T‐junction configuration to combine two BPFs circuits for one planar diplexer. Based on the structure, the fabricated wide‐stopband planar diplexer prototype with compact dimension is achieved to operate at the WLAN frequencies (i.e., 3.65/5.2 GHz). Both the simulated and measured results indicate that satisfactory impedance matching and high isolation between two channels are achieved. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:174–178, 2015
X‐band 100 W solid‐state power amplifier using a 0.25 μM GaN HEMT technology
Authors: Kang Dong Min , Lim Jong Won , Ahn Ho Kyun , Kim Sung Il , Kim Hae Cheon , Yoon Hyung Sup , Kwon Yong Hwan , Nam Eun Soo 
Published: November 2014

ABSTRACTThis article describes the successful development and the performance of X‐band 100 W pulsed SSPA using a 25 W GaN‐on‐SiC high electron mobility transistor (HEMT). The GaN HEMT with a gate length of 0.25 µm and a total gate width of 8 mm were fabricated. The GaN HEMT provide a linear gain of 8 dB with 25 W output power operated at 30 V drain voltage in continuous wave (CW)‐operation with a power added efficiency of 43% at X‐band. It also shows a maximum output power density of 3 W/mm. The X‐band pulsed SSPA exhibited an output power of 100 W (50 dBm) with a power gain of 53 dB in a frequency range of 9.2–9.5 GHz. This 25 W GaN HEMT and X‐band 100 W pulsed SSPA are suitable for the radar systems and related applications in X‐band. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:212–216, 2015
An alternative method to extract the parasitic capacitances of GaN FETs
Authors: Loo‐Yau J. R. , Tapia‐Sánchez I. , Moreno P. 
Published: November 2014

ABSTRACTThis work presents a method to determine the parasitic capacitances of GaN FETs, especially the Cpd. The proposed method is based on an idea used for GaAs FET that assumes that Cpd is directly proportional to Cds by a factor of 0.25. The contribution of this work lies in the adaptation of this technique to be suitable for GaN FETs by proposing a methodology to accurately compute the proportionality factor. The proposed procedure is based on the ratio of Im(Y11+Y12) to Im(Y22+Y12), which is related to the asymmetry of the depletion region of the GaN FET under pinched‐off Cold‐FET condition. To validate the proposed method, several GaN FETs were modeled using the extracted capacitances and the simulations results have a high correlation with experimental data. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:223–225, 2015
A conductive shielded compact antenna hat for inverted‐F antennas
Authors: Kim Sung‐Wan , Park Dong‐Chul 
Published: November 2014

ABSTRACTWe propose a conductive shielded compact antenna hat, which can be utilized as a low loss passive RF repeater or coupler, to perform the RF compatibility testing of the aircraft, rocket, and launch vehicle using inverted‐F type antennas. Although the onboard antenna is very closely enclosed by the proposed antenna hat without RF absorbers, the resonance of the antenna itself is hardly affected compared to the free space radiation. The antenna hat which is fabricated for the S‐band inverted‐F antenna with the size of 74 × 13 × 16 mm3 has the small enclosure of 88 × 35 × 44 mm3, the return loss of 25.6 dB, the insertion loss of 0.3 dB, and the leakage loss of 52.5 dB at 2.25 GHz. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:220–223, 2015
Bandwidth enhancement metamaterial antenna based on transmission line approach
Authors: Bala B. D. , Rahim M. K. A. , Murad N. A. 
Published: November 2014

ABSTRACTA composite right‐/left‐handed transmission line metamaterial antenna with enhanced bandwidth and efficiency is proposed. The antenna combines zeroth‐order resonant (ZOR) and positive‐order resonant (POR) modes for the bandwidth enhancement. An asymmetrical coplanar waveguide technique is used to feed the antenna and also to achieve certain degree of compactness. The overall size of the antenna is 0.32λ0 × 0.38λ0 × 0.012λ0 (40 × 48 × 1.52 mm) at 2.4 GHz. Simulation results show that a bandwidth enhancement of 41% is obtained with the radiation efficiencies of 95 and 97% for the ZOR and POR modes, respectively. The measured impedance bandwidth shows that the antenna has potential applications for WLAN (2.39–2.45 GHz) and WiMAX (2.5–2.69 GHz) operations. The simulated and measured antenna performances in terms of return loss and the radiation patterns are presented and compared. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:252–256, 2015
3D localization method for near‐field sources with virtual arrays in the ISM band
Authors: Mora‐Cuevas Jonathan , de Haro‐Ariet Leandro 
Published: November 2014

ABSTRACTThe problem of 3D near‐field source localization using virtual arrays is addressed. The proposed method is based on a spherical wave steering vector whose performance of 2D direction‐of‐arrival and range estimation is evaluated via MUSIC‐based algorithm. Experimental results in comparison with simulation ones are presented to validate its efficacy. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:238–242, 2015
Fabrication of gelatin/chitosan nanofibrous scaffold: process optimization and empirical modeling
Authors: Pezeshki‐Modaress Mohamad , Zandi Mojgan , Mirzadeh Hamid 
Published: November 2014

AbstractElectrospinning is a very useful technique for producing polymeric nanofibers by applying electrostatic forces. This study reports on the modeling and optimization of the electrospinning process of gelatin/chitosan, using response surface methodology. The individual and the interaction effects of the gelatin/chitosan blend ratio (50/50, 60/40 and 70/30), applied voltage (20, 25 and 30kV) and feeding rate (0.2, 0.4 and 0.6mLh−1) on the mean fiber diameter and standard deviation of the fiber diameter were investigated on optimization section, using scanning electron microscopy. To fabricate the nanofibrous gelatin/chitosan blend, trifluoroacetic acid/dichloromethane was selected as the solvent system. The model obtained for the mean fiber diameter has a quadratic relationship with applied voltage and feeding rate. The interaction between applied voltage and flow rate were found significant but the interactions of blend ratio and flow rate and also blend ratio and applied voltage were negligible. A quadratic relationship was obtained for applied voltage and flow rate with standard deviation of the fiber diameter and there was no interaction between the parameters in the model. The optimum condition for electrospinning of gelatin/chitosan was also introduced using the model obtained in this study. Scanning electron micrographs of human dermal fibroblast cells on the nanofibrous structures show good attachment and proliferation on the fabricated scaffold surface. Electrospun gelatin/chitosan nanofibrous mats have great potential for use as a scaffold for skin tissue engineering. © 2014 Society of Chemical Industry
Sequence–function relationships in folding upon binding
Authors: Eginton Christopher , Naganathan Saranga , Beckett Dorothy 
Published: November 2014

AbstractFolding coupled to binding is ubiquitous in biology. Nevertheless, the relationship of sequence to function for protein segments that undergo coupled binding and folding remains to be determined. Specifically, it is not known if the well‐established rules that govern protein folding and stability are relevant to ligand‐linked folding transitions. Upon small ligand biotinoyl‐5′‐AMP (bio‐5′‐AMP) binding the Escherichia coli protein BirA undergoes a disorder‐to‐order transition that results in formation of a network of packed hydrophobic side chains. Ligand binding is also allosterically coupled to protein association, with bio‐5′‐AMP binding enhancing the dimerization free energy by −4.0 kcal/mol. Previous studies indicated that single alanine replacements in a three residue hydrophobic cluster that contributes to the larger network disrupt cluster formation, ligand binding, and allosteric activation of protein association. In this work, combined equilibrium and kinetic measurements of BirA variants with alanine substitutions in the entire hydrophobic network reveal large functional perturbations resulting from any single substitution and highly non‐additive effects of multiple substitutions. These substitutions also disrupt ligand‐linked folding. The combined results suggest that, analogous to protein folding, functional disorder‐to‐order linked to binding requires optimal packing of the relevant hydrophobic side chains that contribute to the transition. The potential for many combinations of residues to satisfy this requirement implies that, although functionally important, segments of homologous proteins that undergo folding linked to binding can exhibit sequence divergence.
Growth and characterization of AlxGa1−xN lateral polarity structures
Authors: Hoffmann Marc Patrick , Kirste Ronny , Mita Seiji , Guo Wei , Tweedie James , Bobea Milena , Bryan Isaac , Bryan Zachary , Gerhold Michael , Collazo Ramon , Sitar Zlatko 
Published: November 2014

AbstractAlGaN lateral polarity structures (LPS) with varying Al composition, have been fabricated by metalorganic chemical vapour deposition on LPS templates containing µm size domains. III‐metal and N‐polar AlGaN domains have been grown on LT‐AlN and c‐sapphire domains, respectively. LPS characterization by SEM and AFM reveals two major effects when the Al composition has been varied: (a) A high Al content leads to columnar growth within N‐polar domains and (b) a height difference between the polar domains can be observed for low Al compositions towards III‐polarity. The surface quality of the III‐polar domains is not effected by the Al composition. The surface roughness of N‐polar domains decreases for lower Al compositions. The high periodicity of the polar domains and the high quality of the boundary between domains suggest a high potential of AlGaN LPS to be used as lateral wave guides for quasi phase matching.
Comparing the costs and detectability of bobcat using scat‐detecting dog and remote camera surveys in central Wisconsin
Authors: Clare John D. J. , Anderson Eric M. , MACfarland David M. , Sloss Brian L. 
Published: November 2014

ABSTRACTDetermining cost‐effective field methods for detecting carnivores is critical for effective survey and monitoring studies. As the bobcat (Lynx rufus) undergoes range expansion in the northern and eastern United States, field methods may be useful for informing revisions in population management. We paired 2 scat detection‐dog teams and 16 remote cameras at 4 survey sites within central Wisconsin, during summer 2011, and compared detection totals, detection probabilities, and costs between methods. Laboratory expenditures are an additional cost for scat collection, and we modeled the probability that a collected scat was genetically confirmed as bobcat as a function of dog, handler, site, and the strength of the dog's behavior. We estimated that detection‐dog surveys required only 2 days to achieve a 90% probability of detecting a bobcat in a 4‐km2 area, while a single camera station would require 7–8 weeks. But a month of detection‐dog surveys cost 33% more than a 4‐month camera survey, with projected cost differences increasing annually. There were dog‐specific differences in collection rate, and the probability that a collected scat was genetically confirmed as bobcat was best predicted by the individual dog associated with collection and the survey area, rather than the handler or the dog's observed response. We recommend cameras as a generally more cost‐efficient bobcat survey method, and we advise against relying on the strength of an individual dog's response as a means of screening samples for genetic analysis. However, the most appropriate survey method is likely to be goal‐dependent, and we recommend that detection‐dog contractors both advertise and match the strengths and weaknesses of specific dogs with the needs of clientele. © 2014 The Wildlife Society.
Firm's resilience to supply chain disruptions: Scale development and empirical examination
Authors: Ambulkar Saurabh , Blackhurst Jennifer , Grawe Scott 
Published: November 2014

AbstractThis paper expands our understanding of factors that contribute to development of firm resilience to supply chain disruptions. In doing so, we operationalize firm resilience to understand how supply chain disruption orientated firms can develop resilience to supply chain disruptions. We find that supply chain disruption orientation alone is not enough for a firm to develop resilience. Supply chain disruption oriented firms require the ability to reconfigure resources or have a risk management resource infrastructure to develop resilience. The way in which supply chain disruption oriented firms develop resilience through resource reconfiguration or risk management infrastructure depends on the context of the disruption as high impact or low impact. In a high impact disruption context, resource reconfiguration fully mediates the relationship between supply chain disruption orientation and firm resilience. In a low impact disruption context, supply chain disruption orientation and risk management infrastructure have a synergistic effect on developing firm resilience.