bluuebunny/crossref_metadata_2025 huggingface dataset:
Genetic diversity and correlation of bean caffeine content with cup quality and green bean physical characteristics in coffee (Coffea arabica L.)
Authors: Dessalegn Yigzaw , Labuschagne Maryke T , Osthoff Gary , Herselman Liezel
Published: May 2008

BACKGROUND:Although people began to consume coffee for its stimulating effect, the demand for decaffeinated coffee is increasing and now accounts for 10% of the total amount of coffee consumed in the world. Forty‐two arabica coffee genotypes originating from Ethiopia were tested to assess caffeine content variability among them, and the correlation of caffeine content with cup quality and green bean physical characteristics.

RESULTS:Green bean caffeine content was measured using high‐performance liquid chromatography, while cup quality was determined by professional coffee tasters. Caffeine content ranged from 9.1 to 13.2 g kg−1 on dry mass basis (d.m.b.). Six genotypes—AD0291, AD0591, AD2491, AD2691, AD2791 and AD2891—had a caffeine content of less than 10.0 g kg−1. Caffeine content showed negative and statistically significant correlations with cup quality attributes. Correlations between caffeine content and green bean physical characteristics were non‐significant.

CONCLUSIONS:Simultaneous selection for low caffeine content and good cup quality is possible. Some accessions had low caffeine content, and may serve as a source of desirable genes for variety development of types with relatively low caffeine content. Copyright © 2008 Society of Chemical Industry
Extreme performance TEM horn
Authors: Malherbe J. A. G
Published: May 2008

Previously, a TEM horn with ultra wideband performance had been described. The horn made use of an elliptic plate separation profile, while the plate width was determined by an optimal impedance function and the characteristic impedance equations for microstrip. In this article, it is shown that if the impedance equations for parallel plate waveguide are employed in the calculation of the plate width, extreme bandwith of more than 70:1 for a VSWR of 2:1 can be achieved. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2121–2125, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23550
Smooth‐walled spline‐profile Ka‐band horn covering both the full commercial and military bands
Authors: Granet Christophe , James Graeme L.
Published: May 2008

As an alternative to the corrugated horn, a low‐cost smooth‐walled spline‐profile horn has been designed to cover the complete Ka‐band satellite bands. This new horn is used as a feed in a typical dual‐reflector antenna to demonstrate the overall antenna system meets the usual performance requirements. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2119–2121, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23551
Investigation on the interplay between dispersion and nonlinearity in subwavelength‐diameter silica fibers
Authors: Hu Juan Juan , Ping Shum Perry , Ren Guobin , Yu Xia , Wang Guanghui , Lu Chao
Published: May 2008

A theoretical study of optical properties of subwavelength‐diameter silica fibers is presented, with an emphasis on the interplay between dispersion and nonlinearity. The normalized dispersion and effective nonlinearity are used to analyze the diameter‐dependent relative strength at all wavelengths. The dispersion and nonlinearity length are calculated for guiding waveguide dimension design for possible applications. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2086–2090, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23552
A novel E‐shape radiation pattern reconfigurable microstrip antenna for broadband, wide‐beam, high‐gain applications
Authors: Ouyang Jun , Yang Feng , Yang Shiwen , Nie Zaiping
Published: May 2008

This article presents a novel broadband E‐shape radiation pattern reconfiguratable microstrip antenna. The MEMS switches are used to turn the two operations, a basis mode E‐shape microstrip antenna and a high‐order mode E‐shape microstrip antenna. It is important to make wide‐beam and high‐gain radiation patterns of microstrip antennas, which can be used in GPS, mobile terminal, or wide‐angle scanning phased array. The proposed reconfigurable structure is independent from the antenna types. Measured results of the proposed antennas are provided. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2052–2054, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23554
Fiber‐optical wavelength conversion based on double‐pass supercontinuum generation
Authors: Zhang Zuxing , Ye Zhiqing , Sang Minghuang , Nie Yiyou
Published: May 2008

We have proposed and demonstrated a fiber‐optical scheme of wavelength conversion based on double‐pass supercontinuum generation. An actively mode‐locked fiber laser is first constructed. Then the generation of enhanced supercontinuum with 120‐nm bandwidth is experimentally achieved using double‐pass configuration, which is 30% broader than that of 90 nm using single‐pass configuration. We ultimately attain the converted pulse train with the same repetition rate as that of the actively mode‐locked pulse after filtering of FBG. It is a potential technique for one‐to‐multiple wavelength conversion with series‐wound FBGs. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1987–1989, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23558
Cross polarization studies of rectangular patch antenna
Authors: Yang Shing Lung Steven , Fong Lee Kai , Kishk Ahmed K. , Man Luk Kwai
Published: May 2008

The cross polarization characteristic of rectangular patch antennas exciting the TM01 mode is studied. After reviewing and extending the results for the case of edge fed by a microstrip line, simulated and measured results are presented for the coaxial‐fed rectangular patch antenna. It is found that, while the aspect ratio of 1.5 yields the best cross polarization level in the edge‐fed case, it does not have special significance in the coaxial‐fed case. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2099–2103, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23561
Stacked patch excited horn antenna at 94 GHz
Authors: Shireen Rownak , Hwang T. , Shi Shouyuan , Prather Dennis W.
Published: May 2008

This article presents wideband transition from coplanar waveguide (CPW) to horn antenna (CPWHA) based on slot‐coupled stacked patch antenna technique. Multiple patches are used to excite the fundamental mode into the rectangular waveguide. The antenna provides an efficient solution to vertical integration with optoelectronic devices on lithium niobate (LN) for the applications of millimeter‐wave (mmW) to optical signal processing. The design is optimized using 3D finite element method (FEM) software HFSS. For −10 dB return loss, 30% bandwidth is achieved centered at 94 GHz. The return loss and far‐field radiation pattern of fabricated CPWHA are measured and has been found in very good agreement with the simulated results. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2071–2074, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23562
Impedance and quality factor of mutually coupled multiport antennas
Authors: Sten Johan C.‐E. , Hirvonen Mervi
Published: May 2008

In this study, expressions for the radiation quality factor Q and the input impedance seen at any terminal of a multiport antenna are derived. It is shown computationally that because of the possibility to adjust the antenna current distribution through suitable feeding/loading a multiport antenna can perform lower Qs than a similar single‐port antenna. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2034–2039, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23564
An impedance matching design approach for a dual‐band coplanar‐waveguide‐fed slot antenna
Authors: Joubert J. , Odendaal J. W.
Published: May 2008

In this study, it is shown how dual‐band performance can be achieved from a single coplanar‐waveguide‐fed slot by using an impedance matching design approach. The coplanar‐waveguide‐fed slot is connected to a high‐impedance coplanar‐waveguide transmission line stub terminated with a capacitor. The two elements (slot and terminated stub) forming the antenna can be designed such that the series slot impedance added to the input impedance of the terminated stub result in two distinct resonances at the desired center frequencies for a dual‐band application. A dual‐band 2.4/5.2 GHz antenna is designed, and simulations are validated by the measured reflection coefficient and radiation pattern results. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2031–2034, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23565
Electromagnetic scattering from perfectly conducting periodic surfaces by transforming into equivalent boundary condition
Authors: Serkan Tezel Necmi
Published: May 2008

In this study, electromagnetic scattering from perfectly conducting periodic surface have been solved by means of transformation of problem into equivalent problem, that is scattering from plane represented by high order inhomogeneous impedance boundary condition (IBC). High order impedance functions are determined by function of the roughness of the surface. Then, transformed equivalent problem is solved by means of series expansion method using Floquet modes. This transformation makes the problem simple formulation and computational effectively without involving calculation of slowly converging periodic Green's function. Results and computational times obtained by transform method and those obtained by Method of Moment (MoM) technique are compared. Good agreements are observed in results. It is also observed that transform method needs much less computational time than MoM method. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1997–2000, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23567
Long‐period fiber gratings mechanically induced by winding a string around a fiber/grooved tube set
Authors: Rego G.
Published: May 2008

In this article, we present detailed results on the fabrication and characterization of mechanically induced gratings produced by winding a string around a fiber/tube set. A comparison between the mechanical and arc‐induced gratings is made, which allowed us to draw some conclusions on the formation mechanisms of the latter. The usefulness of mechanical gratings in research labs is discussed and two typical applications are also presented. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2064–2068, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23572
Printed inset sleeve monopole antennas for dual‐band applications
Authors: Baik J.‐W. , Kim Y.‐S.
Published: May 2008

In this study, the simple printed monopole antennas with dual‐band operation are presented. The proposed antennas without any additional metal strips are consisted of the ground shorted inset sleeve for both microstrip and coplanar waveguide type ones. The omnidirectional radiation patterns of two models at two designed frequencies are almost similar to those of a conventional monopole. These printed monopole antennas are very suitable to various dual‐band applications for modern communications. Details of the proposed design and experimental results are demonstrated in this article. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1995–1997, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23574
A small RFID tag antenna with bandwidth‐enhanced characteristics and a simple feeding structure
Authors: Bae Su Won , Lee Woosung , Chang Kihun , Kwon Sewoong , Yoon Young Joong
Published: May 2008

A small RFID tag antenna in a UHF band is proposed in this article. Using dual resonance, the antenna has bandwidth‐enhanced characteristics without an additional matching circuit. The meander shape of the proposed antenna helps to reduce the antenna size. The bandwidth of the antenna is enhanced by two radiators that create dual resonance in adjacent frequencies. When the length and location of each radiator are adjusted, the antenna can make dual resonance at an arbitrary impedance point, thereby enabling the antenna to match an RFID tag chip in a wide frequency range. According to the simulated and measured results, the proposed antenna has almost double the bandwidth of a regular antenna. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2027–2031, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23576
A novel ring‐wide bandpass filter by using orthogonal feed structure
Authors: Weng Min‐Hang , Liu Shih‐Kun , Liu Yi‐Ting , Hung Cheng‐Yuan
Published: May 2008

In this article, a simple method to design a high‐performance ring‐wideband bandpass filter centered at 4 GHz without the perturbation element is presented. The coupling between the two orthogonal modes is accomplished by combining the resonant mode of the ring resonator and the resonant mode of the coupling line having a length about λg/4 with respect to 4 GHz. This fabricated filter at center frequency f0 of 4 GHz has showed very good measured characteristics, including a 3‐dB fractional bandwidth of 40%, a very low insertion loss of 0.3 ± 0.1 dB, a stopband from 6 to 10 GHz, and a very high selectivity. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2025–2027, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23577
Miniaturized dual‐mode bandpass filter using meander square‐ring resonator
Authors: Chen Chien‐Hung , Chen Hua‐Ming , Lin Yi‐Fang , Yang Cheng‐Fu
Published: May 2008

A dual‐mode bandpass filter (BPF) using the degenerate modes of a meander square‐ring structure printed on the high‐permittivity substrate is proposed. The dual‐mode resonator is based on a square‐ring loaded with two meander strips at the coupling sides. The filter is printed on the Al2O3 substrate with a permittivity of 9.8 and could be easily integrated with RF circuits. Besides its simple structure, the filter shows low insertion loss and small size, owing to the high‐permittivity substrate used. The proposed filter shows a 6.3% bandwidth at the central frequency 2406 MHz, and it also provides transmission zeros on both sides of the bandwidth. Experimental results are in good agreement with simulated values. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2117–2119, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23578
Folded shorted patch antenna with an offset feeding probe
Authors: Wong S. H. , Lau K. L. , Luk K. M.
Published: May 2008

This article presents the design and performance of a wideband folded shorted patch antenna. The proposed antenna consists of a folded trapezoidal patch that is shorted to the ground plane and is fed by a coaxial probe. By offsetting the probe feeding position from the midline of the patch, wide impedance bandwidth of 56.1% (1.59–2.83 GHz) is obtained for SWR < 2, which is nearly two times that of the antenna without offsetting the probe. The patch of this antenna is 0.071λ0 in height and 0.35λ0 in length, where λ0 is the free space wavelength at the center frequency of its operating bandwidth. Therefore, this antenna is suitable for the multiband indoor wireless communication systems nowadays. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2114–2117, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23579
Simulation of photonic crystal nanocavity using the FETI‐DPEM method
Authors: Li Yu‐Jia , Jin Jian‐Ming
Published: May 2008

The dual‐primal finite element tearing and interconnecting (FETI‐DPEM) method, as an application of a nonoverlapping domain decomposition method to the finite element analysis of electromagnetic problems, is applied to the three‐dimensional (3D) full‐wave simulation of a high quality (Q) factor photonic crystal (PhC) nanocavity in an optically thin dielectric slab. Curvilinear tetrahedral elements and higher‐order vector basis functions are employed in the FEM to accurately represent the field in the PhC nanocavity. Geometrical repetitions associated with PhCs nanocavities are fully exploited, which significantly reduces the computational complexity and memory requirement. Moreover, due to its domain decomposition nature, the FETI‐DPEM method is highly parallelizable, which further accelerates the computation using parallel computing techniques. As a result, such a method is ideally suited for the fullwave analysis of PhC nanocavities. Simulations of a high Q PhC nanocavity using the FETI‐DPEM method are carried out to demonstrate the efficiency of the method. The calculated Q factors are compared with previously published data. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2083–2086, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23580
Extinction ratio improvement using nonlinear four‐wave mixing in SOAs with assist beam
Authors: Dlubek Michal P. , Phillips Andrew J. , Larkins Eric C.
Published: May 2008

This letter presents a novel and simple scheme for all‐optical signal regeneration, based on four‐wave mixing (FWM) in semiconductor optical amplifiers (SOA). The nonlinear power transfer characteristic of the device is obtained by using the mixing product proportional to the squared power of the incoming signal. This nonlinear FWM scheme is further improved by using a strong assist beam, located close to the transparency point of the gain curve. This additional beam improves the nonlinear exponent of the transfer function; mainly by reducing gain saturation. Experimental results show that extinction ratio improvement by almost 3 dB at 4 Gb/s is obtained, accompanied by a wavelength shift of 3.3 nm. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2079–2083, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23581
A transformer‐loaded variable‐gain LNA for 24‐GHz vehicular short‐range radar
Authors: Ragonese Egidio , Scuderi Angelo , Palmisano Giuseppe
Published: May 2008

In this article, a 24‐GHz low‐noise amplifier for vehicular short‐range radar applications is presented. The circuit, fabricated in a 0.13‐μm SiGe:C BiCMOS process, consists of three fully differential transformer‐loaded cascode stages, including a gain‐control functionality. The amplifier exhibits a 35‐dB power gain and a noise figure of 3.4 dB, providing a reverse isolation better than −60 dB. By using a 1‐bit gain control, the LNA achieves an input 1‐dB compression point of −12 dBm. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2013–2016, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23584
Design of a multilayered dual‐band bandpass filter with transmission zeros
Authors: Weng Min‐Hang , Yang Ru‐Yuan , Chang Yu‐Chi , Wu Hung‐Wei , Shu Kevin
Published: May 2008

In this article, a dual‐band bandpass filter (BPF) using the multilayered structure is presented. The BPF consists of a pair of uniform impedance resonators on the top layer and a pair of step‐impedance resonators on the middle layer. By using the multilayered structure, the multitransmission zeros located near the passband edges, which is introduced by the crosscoupling effect, can be created to improve the filter selectivity. In addition, the bandwidths of the two passbands (2.4/5.2 GHz) can be tunable by adjusting the coupling gap distance between the resonators. The fabricated filter has a very compact size. Experimental results of the fabricated filter are well agreed with the simulation results. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2010–2013, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23585
Spherical vector wave functions solution to scattering of a plane wave by a spherical shell of uniaxial anisotropic left‐handed material
Authors: Geng You‐Lin , He Sailing
Published: May 2008

Based on the spherical vector wave function in uniaxial anisotropic left‐handed‐material (LHM), the electromagnetic fields in unbounded uniaxial anisotropic left‐handed material are expanded in terms of spherical vector wave functions in uniaxial anisotropic LHM. Applying the continuous boundary conditions of electromagnetic fields in tangential direction in the spherical shell of uniaxial anisotropic left‐handed material, the expansion coefficients of electromagnetic fields in the spherical shell of uniaxial anisotropic LHM can be derived, and then the radar cross sections (RCSs) can be obtained. Some numerical results have been given and the method in this article can be applied in the areas of antenna design and system optimization, wave propagation in complex media, and electromagnetic compatibility. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2142–2146, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23586
Millimeter wave conduct speech enhancement based on auditory masking properties
Authors: Li S. , Wang J. Q. , Niu M. , Liu T. , Jing X. J.
Published: May 2008

Besides air, the millimeter wave (MMW) provides another valuable medium to conduct speech, which may extend the traditional speech detecting method, and provides some exciting possibility for wide applications. However, the MMW conduct speech is in less intelligible and poor audibility since it is corrupted by additive combined noise. This article, therefore, proposed a simple and efficient way to take into account properties of the auditory system in the enhancement processes. The parameters of the spectral subtraction algorithm can be adaptive adjust in a perceptual sense based on a tradeoff between amount of noise reduction, the speech distortion, and the level of musical residual noise. The results from both simulation and listening evaluation suggest that the background noise can be reduced efficiently while the distortion of MMW radar speech remains acceptable, the enhanced speech also sounds more pleasant to human listeners, resulting in improved results over classical subtractive‐type algorithms. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2109–2114, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23588
A dual‐band RF switch using composite right/left‐handed transmission lines and PIN diodes
Authors: Shin Dong‐Ryul , Kim JeongPyo , Park ChangHyun , Seong Wonmo
Published: May 2008

A dual‐band RF switch that utilizes composite right/left handed (CRLH) transmissions‐lines(TLs) and PIN diodes is proposed. The design method of RF switch is based on the phase characteristic of the CRLH‐TL, which can be adjusted arbitrary, and employed conventional type‐II; filter structure. The use of multiple PIN diodes as switching element offers prominent performance such as low insertion loss, low power consumption, and high isolation. Theoretical performance of RF switch is verified through the circuit simulations and the measurement of a fabricated prototype at 0.8 GHz and 1.6 GHz. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2074–2077, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23591
Investigation of low‐profile Fresnel zone plate antennas
Authors: Stout‐Grandy S. M. , Petosa A. , Minin I. V. , Minin O. V. , Wight J. S.
Published: May 2008

This article presents low‐profile configurations of the Fresnel zone plate antenna at Ka‐band. The investigation involved progressively reducing the focal distance of the antenna through simulations and observing the effect on the directivity, radiation patterns, and aperture efficiency. The number of metal zones was also varied in the simulations. It was found that focal distances below 0.75λ yielded little more directivity than the feed itself. With a single zone, the 1.25λ focal distance achieved the highest overall aperture efficiency of 24%, which was a significant improvement over the larger focal distance cases. Measurements were performed to verify the simulated results. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2039–2043, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23593
Characterization of multimode fibers for use in millimeter wave radio‐over‐fiber systems
Authors: Khawaja Bilal A. , Cryan Martin J.
Published: May 2008

Millimeter wave radio‐over‐fiber links using both single mode and, for what is believed to be the first time, multimode fibers are demonstrated over a 0–50 GHz bandwidth using a external Mach‐ Zehnder modulator operating at 1550 nm. The multimode fiber links show the potential for use in low‐cost distributed antenna systems. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2005–2007, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23594
A 26–38 GHz millimeter‐wave band APDP sub‐harmonic mixer
Authors: Yu Shu‐Jenn , Huang Hui‐Min , Lee Ching‐Sung , Wu Chang‐Luen , Hsu Wei‐Chou
Published: May 2008

A 26–38 GHz millimeter‐wave (MMW) band sub‐harmonic mixer has been designed using a 0.15‐μm GaAs pseudomorphic high‐electron‐mobility transistor (pHEMT) technology. The anti‐parallel diode pair (APDP) configuration as the basic unit in this sub‐harmonic mixer design to suppress the fundamental frequency signals is used. The radio‐frequency (RF) and the local oscillator (LO) signals are imported by two Lange couplers in the proposed design, with four pairs of APDPs connected in a ring structure. Superior RF/LO‐to‐IF (intermediate‐frequency) and 2LO‐to‐RF/IF isolations have been achieved. The sub‐harmonic mixer circuit has also exhibited excellent conversion loss of 13.7 dB with LO power of 13 dBm. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2135–2138, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23595
Characterization of microstrip patch antennas on metamaterial substrates loaded with complementary split‐ring resonators
Authors: Lee Yoonjae , Hao Yang
Published: May 2008

We present characteristics of microstrip patch antennas on metamaterial substrates loaded with complementary split‐ring resonators (CSRRs). The proposed antenna utilizes CSRRs in the ground plane altering the effective medium parameters of the substrate. To characterize the performance of the CSRR loaded microstrip antenna, the metamaterial substrate has been modeled as an effective medium with extracted constitutive parameters. Simulation results were verified by experimental results. The experimental results confirm that the CSRR loaded patch antenna achieves size reduction as well as bandwidth improvement. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2131–2135, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23596
Fast multi‐frequency extraction of 3D impedance based on boundary element method
Authors: Yu Wenjian , Yan Changhao , Wang Zeyi
Published: May 2008

For the boundary element method used in an impedance extractor FastImp, a scheme to handle the boundary integrals is proposed to accelerate the computation for multiple frequencies. Several techniques are combined in the scheme. The near‐field integrals are calculated with a series expansion technique and an approximate formula, whereas the precorrected FFT algorithm is employed for the far‐field integrals. Numerical experiments show that the proposed method is several times faster than FastImp for multi‐frequency extraction, while preserving high accuracy. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2191–2197, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23597
A novel three‐port tunable optical filter and crosstalk analysis
Authors: Yu Kan , Liu Wen , Huang Dexiu , Chang Jin
Published: May 2008

According to the tilted incidence characteristics of thin film narrowband filter, a stack of 100‐GHz DWDM four cavities angle‐tuned narrowband thin‐film filter with low polarization dependent loss has been designed and optimized. Using the angle‐tuned filter, we developed a novel three‐port tunable optical filter. The crosstalk of the tunable filter is analyzed and calculated in detail, and the theoretical analysis result coincides with experimental result. The experiments show that the three‐port tunable filter with low polarization dependent loss has an effective tunable range of 26 nm, and it has a bright application opportunity for its flexibility and effective performance. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2163–2167, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23599
Bandpass shielding enclosure design for modern handheld communication devices with internal electric‐dipole and magnetic‐loop antennas
Authors: Chiu Cheng‐Nan , Kuo Yu‐Fan
Published: May 2008

This letter reveals a design approach for a bandpass shielding enclosure to be applied in modern handheld communication devices employing either an internal electric‐dipole antenna or an internal magnetic‐loop antenna. This enclosure features high transmittance at the wireless‐signal band and high shielding effectiveness outside this band, and has minimal influence on the radiation characteristics of the internal antennas used with these devices. A prototype was created and examined. The simulated and measured results demonstrate that the prototype can achieve the promised performance for either kind of internal antenna. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2223–2226, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23600
Dielectric resonator antenna element and subarray with unequal cross‐stub
Authors: Zhang Li‐Na , Zhong Shun‐Shi , Xu Sai‐qing
Published: May 2008

A novel dielectric resonator antenna element and its 2 × 2‐element subarray are introduced, where the element is fed by a microstrip line with an unequal crossstub to expand the impedance bandwidth. Both the simulated and experimental results are presented, showing a good agreement. The proposed subarray provides a measured impedance bandwidth of 4.2% for the dielectric constant of resonator εr1 = 38 and a measured gain of 9.8–10.8 dBi across the entire operating bandwidth. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2189–2191, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23602
Optical design and performance of a novel multifunction optical device
Authors: Chen Q. H. , Wu W. G. , Wang Z. Q , Yan G. Z. , Hao Y. L.
Published: May 2008

This letter presents a novel MEMS‐based multifunction‐integrated optical device capable of performing as variable optical power splitter (VOPS), optical switch (OS), and variable optical attenuator (VOA). The device manipulates the light with a binary‐slope mirror driven by compound electrostatic actuator. The optical models for splitting and attenuating are investigated, respectively. Ball‐lensed fibers are assembled with the device to achieve high coupling efficiency in this work. Measurements reveal that the excess loss of the device is less than 3 dB, and the controllable attenuation range is up to 39 dB. Moreover, polarization‐dependent loss is less than 0.7 dB. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2185–2189, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23603
Design of a miniature and harmonic control patch dual‐mode bandpass filter with transmission zeros
Authors: Su Yan‐Kuin , Chen Jau‐Rung , Weng Min‐Hang , Hung Cheng‐Yuan
Published: May 2008

A miniature and harmonic control patch dual‐mode bandpass filter (BPF) with transmission zeros for application of global positioning system (GPS) is proposed. The right crossed‐slots of the patch resonator are used to determine the main passband frequency of the BPF. In this study, by using a pair of square etched areas (SEAs) acted as perturbation elements, the dual mode filtering performance can be excited and two transmission zeros located on either side of the passband are clearly observed. It is found that two transmission zeros can improve the selectivity of the BPF as well as the stopband rejection effectively, thus avoiding the interference from other communication systems. The measured results of the fabricated BPF are in good agreement with full wave simulation. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2161–2163, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23604
A 24‐GHz active SPST MMIC switch with INGAP/GAAS HBTS
Authors: Yang Jong‐Ryul , Kim Dong‐Wook , Hong Songcheol
Published: May 2008

A 24‐GHz single‐pole, single‐throw (SPST) switch with high isolation is designed using InGaP/GaAs HBT process. To obtain high isolation in an off state, cascode structures are utilized and an additional shunt transistor is introduced in an output, which helps to reject a leakage signal. Dummy cascode structure is used as a current steering circuit for input matching and short rise/fall time. The fabricated SPST switch shows an effective isolation of ∼52 dB at 22.8 GHz and 41 dB at 24 GHz. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2155–2158, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23606
Effect on radio frequency human exposure of mobile phone inside an enclosed metallic elevator
Authors: Tang C. K. , Chan K. H. , Fung L. C. , Leung S. W.
Published: May 2008

The effects of the radio frequency human exposure to mobile phone, inside both partially and fully enclosed metallic elevators, have been analyzed. It has been found that the evaluated peak Specific Absorption Rate (SAR) and the whole body absorption power are increased only by a small percentage inside the partial enclosures as compared to the free space environment; whereas inside the full enclosure, the peak SAR and the whole body absorption power are significantly increased. The analysis suggest that the reason of such a high level of RF energy absorption inside a fully enclosed metallic elevator is mainly because of the resonance effect. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2207–2210, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23612
Investigation of broadband power amplifier with high power‐combining efficiency
Authors: Song Kaijun , Fan Yong , Zhou Xiaobing
Published: May 2008

A four‐device broadband solid‐state power amplifier, which is based on radial waveguide power‐dividing/combining circuit, has been investigated in this work. The fabricated power amplifier combining four monolithic microwave integrated circuit power amplifiers shows a 12–16.6 dB small‐signal gain over a broadband from 6 to 14 GHz. The measured maximum output power at 1 dB compression is 25.6 dBm at 10 GHz, with a high power‐combining efficiency of 96%. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2178–2181, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23614
Micro balun design and fabrication at 910 MHz and mobile RFID reader miniaturization thereby
Authors: Kim Jong‐Cheol , Jung Jin‐Woo , Roh Hyoung‐Hwan , Park Jun‐Seok
Published: May 2008

This article represents a microchip balun for UHF mobile RFID system at 910 MHz. This balun is designed by transforming coupled transmission lines into lumped‐element equivalent circuit, and thus monolithic elements that are fabricated by IPD technology replace it for entirely miniaturized size. The corresponding balun performs under 3 dB return loss, with nearly 176 (176.42) degree of phase difference characteristic; therefore, this meets the UHF mobile RFID reader system consideration. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2203–2206, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23617
Novel band‐notch UWB antenna design with slit ground plane
Authors: Sim Chow‐Yen‐Desmond , Chung Wen‐Tsan , Lee Ching‐Her
Published: May 2008

A newly designed microstrip feed, octagonal‐shaped ultra‐wideband printed antenna is proposed. The UWB operation within the required 3.1–10.6 GHz band is achieved by simply embedding in the ground plane a small rectangular slit, located below the feed line of an octagonal patch. With the dimensions (length and height) of the slit carefully tuned, a notched band of around 5.1–6.4 GHz can be achieved, without applying the commonly recommended techniques of loading the radiating patch with a slot or an open‐ended slit. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2229–2233, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23621
A positive/negative refractive index coplanar transmission line in CMOS for controlled insertion phase
Authors: Symon Podilchak , Brian Frank , Al Freundorfer , Yahia Antar
Published: May 2008

A positive/negative refractive index coplanar transmission line is presented and used for phase control in CMOS circuits. Good performance has been achieved. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2227–2230, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23622
Wideband bandpass filter using unpowered HEMT amplifiers
Authors: Kim Yong Kyu , Hwang Sung Woo
Published: May 2008

A wideband bandpass filter using unpowered, packaged HEMT amplifiers is proposed and implemented. The key idea is to utilize very small parasitic capacitances of the unpowered HEMT as a part of the feedback loop connecting LC resonators. At the input power of −10 dBm, the 3 dB bandwidth of the fabricated bandpass filter is 93.6% of the center frequency (1.536 GHz). Furthermore, our filter does not show appreciable spurious up to 12 GHz. These internal capacitances of the HEMT extracted from the equivalent circuit modeling are shown to be in the range of 10–500 fF. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2197–2200, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23623
Erratum: Neural network estimation of RF electromagnetic pollution near TV broadcast transmitters
Authors: Çolak İlhami , Kosalay İlhan
Published: May 2008

Originally published in Microwave Opt Technol Lett 50: 1004‐1010, 2008. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2233, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23624
Structural determination of two new triterpenoids from Potentilla discolor Bunge by NMR techniques
Authors: Yang Jie , Chen Xiao‐Qing , Liu Xiao‐Xiao , Cao Yuan , Lai Mao‐Xiang , Wang Qiang
Published: May 2008

Two new pentacyclic triterpenoids, 3α, 30‐dihydroxylup‐20(29)‐en‐27‐oic acid (1) and (20S)‐3α, 29‐dihydroxylupan‐27‐oic acid (2) were isolated from the whole herbs of Potentilla discolor Bunge. The structures of these two new compounds were elucidated, and complete assignments of the 1H and 13C NMR spectroscopic data were achieved by 1D and 2D NMR experiments (HSQC, HMBC, 1H1HCOSY and ROESY). Copyright © 2008 John Wiley & Sons, Ltd.
In vivo myocardial infarct area at risk assessment in the rat using manganese enhanced magnetic resonance imaging (MEMRI) at 1.5T
Authors: Daire J.L. , Hyacinthe J.N. , Tatar I. , Montet‐Abou K. , Ivancevic M.K. , Masterson K. , Jorge‐Costa M. , Morel D.R. , Vallée J.P.
Published: May 2008

The aim of this study was to measure the myocardial area at risk in rat, using MRI and manganese injection during a coronary occlusion/reperfusion model at 1.5T. A sequential protocol with occlusion and MnCl2 injection immediately followed by MRI was used with the assumption that MnCl2‐induced contrast persistence is enough to accurately image the area at risk 90 min after occlusion. A total of 15 adult rats underwent a single 30‐min episode of coronary occlusion followed by reperfusion. MnCl2 was injected (25 μmol/kg) at the beginning of the occlusion for 11 rats (group 1) and 6 h after reperfusion for four animals (group 2). A deficit of signal enhancement was observed in all rats. Hypoenhancement area in group 1 was correlated to the area at risk delineated by methylene blue (r = 0.96, P < 0.0001) whereas in group 2 it was correlated to the infarct area given by triphenyltetrazolium chloride (TTC) solution (r = 0.98, P = 0.003). The area at risk size was significantly correlated with left ventricle ejection fraction (LVEF), end‐systolic volume and anterolateral wall thickening. This work demonstrates that hypoenhanced zone obtained after manganese injection during occlusion represents the area at risk and not only the infarct zone. Magn Reson Med 59:1422–1430, 2008. © 2008 Wiley‐Liss, Inc.
Automated quality control protocol for MR spectra of brain tumors
Authors: Wright Alan J. , Arús Carles , Wijnen Jannie P. , Moreno‐Torres Angel , Griffiths John R. , Celda Bernardo , Howe Franklyn A.
Published: May 2008

eTUMOUR (http://www.etumour.net/) is acquiring a large database of brain tumor 1H MR spectra to develop automated pattern recognition methods and decision support system (DSS) for tumor diagnosis. Development of accurate pattern‐recognition algorithms requires spectra undistorted by artifacts, low signal‐to‐noise, or broad lines. eTUMOUR currently uses panels of expert spectroscopists to subjectively grade spectra as being acceptable or unacceptable. Automated quality control (QC) would be more satisfactory for several reasons: 1) to provide a reproducible objective classification of spectrum quality; 2) for use within the future DSS to prevent misdiagnosis due to poor spectrum quality; 3) to rapidly process the very large datasets of 1H spectra being accrued. An automated QC method using independent component analysis for feature extraction with a least‐squares support vector machine classifier is presented. Separate training (n = 144) and test sets (n = 98) of single‐voxel spectra from brain tumors and other lesions were acquired at multiple clinical centers with short and long echo times. Pairs of expert spectroscopists classified the test set an average of 85% the same. The automated QC classification agreed with an expert for 87% of test spectra, on average, suggesting the method classifies spectrum quality as accurately as expert spectroscopists. Magn Reson Med 59:1274–1281, 2008. © 2008 Wiley‐Liss, Inc.
Axcaliber: A method for measuring axon diameter distribution from diffusion MRI
Authors: Assaf Yaniv , Blumenfeld‐Katzir Tamar , Yovel Yossi , Basser Peter J.
Published: May 2008

The diameter of a myelinated nerve axon is directly proportional to its conduction velocity, so the axon diameter distribution helps determine the channel capacity of nervous transmission along fascicles in the central (CNS) and peripheral nervous systems (PNS). Previously, this histological information could only be obtained using invasive tissue biopsies. Here we propose a new NMR‐based approach that employs a model of water diffusion within “restricted” cylindrical axons to estimate their diameter distribution within a nerve bundle. This approach can be combined with MRI to furnish an estimate of the axon diameter distribution within each voxel. This method is validated by comparing the diameter distributions measured using the NMR and histological techniques on sciatic and optic nerve tissue specimens. The axon diameter distribution measured in each voxel of porcine spinal cord using MRI and using histological methods were similar. Applications are expected in longitudinal studies designed to follow nerve growth in normal and abnormal development, as well as in diagnosing disorders and diseases affecting specific populations of axons in the CNS and PNS. Magn Reson Med 59:1347–1354, 2008. © 2008 Wiley‐Liss, Inc.
Rapid and efficient mapping of regional ventilation in the rat lung using hyperpolarized 3He with Flip angle variation for offset of RF and relaxation (FAVOR)
Authors: Santyr Giles E. , Lam Wilfred W. , Ouriadov Alexei
Published: May 2008

A novel imaging method is presented, Flip Angle Variation for Offset of RF and Relaxation (FAVOR), for rapid and efficient measurement of rat lung ventilation using hyperpolarized helium‐3 (3He) gas. The FAVOR technique utilizes variable flip angles to remove the cumulative effect of RF pulses and T1 relaxation on the hyperpolarized gas signal and thereby eliminates the need for intervening air wash‐out breaths and multiple cycles of 3He wash‐in breaths before each image. The former allows an improvement in speed (by a factor of ≈30) while the latter reduces the cost of each measurement (by a factor of ≈5). The FAVOR and conventional ventilation methods were performed on six healthy male Brown Norway rats (190–270 g). Lobar measurements of ventilation, r, obtained with the FAVOR method were not significantly different from those obtained with the conventional method for the right middle and caudal and left lobes (P > 0.05 by a Wilcoxon matched pairs test). A methacholine challenge test was also administered to an animal and reduction and recovery of r was detected by the FAVOR method. The reduced 3He consumption and the improvement in speed provided by FAVOR suggest that it may allow measurement of ventilation in human subjects not previously possible. Magn Reson Med 59:1304–1310, 2008. © 2008 Wiley‐Liss, Inc.
Fast slice‐selective radio‐frequency excitation pulses for mitigating B inhomogeneity in the human brain at 7 Tesla
Authors: Zelinski Adam C. , Wald Lawrence L. , Setsompop Kawin , Alagappan Vijayanand , Gagoski Borjan A. , Goyal Vivek K. , Adalsteinsson Elfar
Published: May 2008

A novel radio‐frequency (RF) pulse design algorithm is presented that generates fast slice‐selective excitation pulses that mitigate B inhomogeneity present in the human brain at high field. The method is provided an estimate of the B field in an axial slice of the brain and then optimizes the placement of sinc‐like “spokes” in kz via an L1‐norm penalty on candidate (kx, ky) locations; an RF pulse and gradients are then designed based on these weighted points. Mitigation pulses are designed and demonstrated at 7T in a head‐shaped water phantom and the brain; in each case, the pulses mitigate a significantly nonuniform transmit profile and produce nearly uniform flip angles across the field of excitation (FOX). The main contribution of this work, the sparsity‐enforced spoke placement and pulse design algorithm, is derived for conventional single‐channel excitation systems and applied in the brain at 7T, but readily extends to lower field systems, nonbrain applications, and multichannel parallel excitation arrays. Magn Reson Med 59:1355–1364, 2008. © 2008 Wiley‐Liss, Inc.