bluuebunny/crossref_metadata_2025 huggingface dataset:
On the use of Standardized Precipitation Index (SPI) for drought intensity assessment
Authors: Naresh Kumar M. , Murthy C. S. , Sesha Sai M. V. R. , Roy P. S.
Published: April 2009

Monthly rainfall data from June to October for 39 years were used to compute Standardized Precipitation Index (SPI) values based on two parameter gamma distribution for a low rainfall and a high rainfall districts of Andhra Pradesh state, India. Comparison of SPI with actual rainfall and rainfall deviation from the mean indicated that SPI values under‐estimate the intensity of dryness/wetness when the rainfall is very low/very high, respectively. As a result, the SPI in the worst drought years of 2002 and 2006 in the low rainfall district indicated only moderate dryness instead of extreme dryness. SPI values of the high rainfall district showed slightly better stretching in both positive and negative directions, compared to that of the low rainfall district. Further, the SPI values of longer time scales (2, 3 and 4 months) showed an extended range compared to that of 1 month, but the sensitivity in drought years has not improved significantly.

Normality tests were conducted based on Shapiro‐Wilk statistic, p‐values and absolute value of the median to ascertain whether non‐normality of SPI is a possible reason. Although the results confirmed normal distribution, the scatter plot indicated deviation of the cumulative probability distribution of SPI from normal probability in the lower and upper ranges.

Therefore, it is suggested that SPI as a stand alone indicator needs to be interpreted with caution to assess the intensity of drought. Further investigations should include sensitivity of SPI to the estimated shape and scale at lower and upper bounds of the gamma distribution and use of other distributions, such as Pearson III, to standardize the computational procedures, before using SPI as a substitute to the rainfall deviations from normal, for drought intensity assessment. Copyright © 2009 Royal Meteorological Society
A comparison of the rainfall patterns between stations on the East and the West coasts of Peninsular Malaysia using the smoothing model of rainfall amounts
Authors: Suhaila Jamaludin , Jemain Abdul Aziz
Published: April 2009

The aim of this study is to model rainfall amounts on a daily basis by fitting a smooth curve to the mean rainfallperrainy day. The rainfall amounts are described as gamma distributions with smoothing parameters. The smoothing technique used is the approach of the Fourier series. Six rain gauge stations with the daily rainfall series covering the same period (1975–2004) are examined. Different rainfall patterns are observed among the stations, particularly between the east and the west. The stations in the western area have a bimodal pattern of rainfall and are best described with two harmonics, while four harmonics are required for the stations in the eastern area which exhibit a unimodal pattern of rainfall. The resulting curves with fitted smoothing parameters provide a good summary of statistics and useful information for describing the rainfall patterns and climate of the studied stations. Copyright © 2009 Royal Meteorological Society
Regional daily maximum rainfall estimation for Cekerek Watershed by L‐moments
Authors: Yurekli Kadri , Modarres Reza , Ozturk Fazli
Published: April 2009

The estimation of maximum daily rainfall (PDmax) is usually required for the estimation of design flood (the maximum flood that any hydraulic structure can safely pass). However, PDmax estimation is usually required for watersheds where rainfall data are either not available or only available in short periods from various sites and so are unsuitable for maximum daily rainfall estimation. In this study, the regional PDmax of the Cekerek watershed in Turkey is estimated using the method of l‐moments using 17 rainfall stations in the region. The discordant test for outlier stations showed no discordant station in the region. Applying the homogeneity measure, Hi, the homogeneous region was identified. To find the best regional distribution, the ZDIST goodness‐of‐fit test was applied. This test introduced two distributions as the candidates for regional parent distributions; Generalized Extreme Values (GEV) and 3‐parameter Log Normal (LOGN3) distributions. The LOGN3 distribution was selected as the best regional distribution as it has the smaller absolute value of the statistics (ZDIST) based on the goodness‐of‐fit‐test. Copyright © 2009 Royal Meteorological Society
Regional scale spatio‐temporal consistency of precipitation variables related to water resource management and planning
Authors: Paynter Shayne , Nachabe Mahmood
Published: April 2009

The focus of this research was to determine the extent of spatio‐temporal changes in precipitation patterns using methods that can be regionalized and applied to various water resources such as lakes, streams, reservoirs or other water bodies. Many water resources throughout the world have demonstrated changes in historic water levels. As precipitation is the major input to these water bodies, it is important to investigate any changes in rainfall in both time and space. To investigate these patterns regionally, appropriate distributions, either gamma or generalized extreme value (GEV), were fitted to variables at a number of rainfall gauges within 40 km of a particular lake using maximum likelihood estimation. The variables included total annual rainfall, rainfall days per year, maximum annual event rainfall and maximum annual interevent days. Once the distribution parameters were estimated, an average, representative, distribution for each variable with 99% confidence limits was developed to determine if the fits for all gauges and variables were contained by these limits. To examine the temporal variation, distribution parameters were allowed to vary with time and then compared to constant parameter fits via likelihood ratio tests to determine if the varying parameter model significantly improved the fit. The spatial distribution of rainfall variables was found to be quite homogenous within the given confidence limits with some exceptions at high and low percentiles. Furthermore, the temporal distribution of rainfall variables was found to be stationary with only one gauge showing a significant trend. The average distribution for each precipitation variable developed can be applied at water resources within the region without rainfall gauges in proximity due to the spatial homogeneity and temporal stationarity identified. The methodology can be adapted to water resource management and planning in other regions. Copyright © 2009 Royal Meteorological Society
Vascularized free fibular bone graft in the management of congenital tibial pseudarthrosis
Authors: Korompilias Anastasios V. , Lykissas Marios G. , Soucacos Panayiotis N. , Kostas Ioannis , Beris Alexandros E.
Published: April 2009

Congenital pseudarthrosis of the tibia (CPT) remains one of the most challenging problems confronting the orthopaedic surgeon. The operative results are frequently less than successful; many cases require several surgical procedures, and a significant number of them ending in amputation. The purpose of this study was to access the surgical results, complications, secondary procedures, and long‐term results of free vascularized fibular graft (FVFG) in the treatment of congenital pseudarthrosis of the tibia. Between 1992 and 2007, nine patients with CPT were treated consecutively at our clinic with free fibula transfer. There were six females and three males. The mean age at the time of operation was 6.5 years (range, 1–12 years). Stability, after reconstruction with FVFG, was maintained with internal fixation in five patients, unilateral frame external fixation in three patients, and intramedullary pin in one patient. Average postoperative follow‐up time was 9 years (range, 2–15 years). In seven patients, both ends of the graft healed primarily within 3.7 months (range, 1.5–6 months). In one patient, the distal end of the graft did not unit. This patient required three subsequent operations to achieve union. Stress fracture occurred in the middle of the grafted fibula in one patient, who underwent four additional operations before union, was achieved. Despite the relatively high‐complication rate, FVFG remains a valid method for the treatment of CPT. However, even achieving union of pseudarthrosis is not enough for the resolution of the disease. This is only half of the problem; the other half is to maintain union. Long‐term follow‐up beyond skeletal maturity, if possible, is necessary to evaluate surgical results. © 2009 Wiley‐Liss, Inc. Microsurgery, 2009.
The use of vascularized fibular grafts for the reconstruction of spinal and sacral defects
Authors: Moran Steven L. , Bakri Karim , Mardini Samir , Shin Alexander Y. , Bishop Allen T.
Published: April 2009

Background: Large segmental defects of the spine may result from tumor resection as well as infection. The surrounding soft tissue in these situations is often compromised due to radiation exposure or infection. In these situations, in which conventional bone grafting has often failed, we have found vascularized fibular grafts an effective method of achieving bony union. The purpose of this study was to review the results of vascularized bone grafting for complex spinal reconstruction using free fibular transfer. Methods: We performed a retrospective chart review of all patients who underwent multisegmental spinal reconstruction and pelvic reconstruction using posterior instrumentation and free fibula vascularized bone transfer. Results: Twelve patients underwent 14 free fibula transfers (7 anterior and 5 posteriorly placed) for reconstruction of lumbosacral spinal defects. Preoperative diagnoses included tumor, osteomyelitis, and nonunion. Average number of vertebral body resections was four and posterior instrumentation was used for all arthrodeses. Average duration of follow up was 45 months. Two flaps failed (14%), one resulting in nonunion and the other required salvage with an external hemipelvectomy. All remaining flaps healed at a mean time of 4.5 months (range, 3–10 months). Conclusion: Free fibula transfer for complex spinal reconstruction is a reliable means of obtaining bony union for complex lumbar or sacral resections where traditional bone grafting techniques may not be technically feasible. © 2009 Wiley‐Liss, Inc. Microsurgery, 2009.
Correlation of three sciatic functional indices with histomorphometric findings in a rat sciatic nerve allograft repair model
Authors: Rustemeyer Jan , Dicke Ursula
Published: April 2009

Walking track analysis was used to measure global functional recovery following sciatic nerve injury. The correlation of morphologic outcome and different sciatic functional indices (SFIs) depends on different variables. The objective of this study was to compare three different SFIs and their correlation with histomorphometric findings in a sciatic nerve allograft repair model in the rat without (group I,n= 8) or with (group II,n= 8) daily intramuscular administration of 0.1 mg/kg FK 506. The correlation of SFIs with each other and with the myelin basic protein (MBP) density of nerve sections proximal, median, and distal to sciatic nerve grafts (1.5 cm) at 4, 8, 12, and 16 weeks postoperation (p.o.) was calculated, and unoperated animals served as controls (n= 8). Significant differences between SFIs calculated for experimental groups I and II at 12 and 16 weeks p.o. suggested that superior functional nerve recovery occurred in group II. However, there were significant differences between all SFIs at 16 weeks p.o. in group II, whereas only differences between SFI 1 and SFI 2 + 3 occurred in group I. SFIs of group II did not reach the values of the unoperated group. There were significant differences between the histomorphometric outcomes of groups I and II. There was no significant difference of MBP density between group II and the unoperated group, suggesting complete morphologic recovery. In conclusion, we found significant correlation between the MBP densities of groups I and II and all SFIs, suggesting a close relationship between histomorphometric and functional findings. © 2009 Wiley‐Liss, Inc. Microsurgery, 2009.
Global weak solution to the flow of liquid crystals system
Authors: Jiang Fei , Tan Zhong
Published: April 2009

In this paper, we study a simplified system for the flow of nematic liquid crystals in a bounded domain in the three‐dimensional space. We derive the basic energy law which enables us to prove the global existence of the weak solutions under the condition that the initial density belongs to Lγ(Ω) for any \documentclass{article}\footskip=0pc\pagestyle{empty}\begin{document}$\gamma >\frac{3}{2}$\end{document}. Especially, we also obtain that the weak solutions satisfy the energy inequality in integral or differential form. Copyright © 2009 John Wiley & Sons, Ltd.
DOP‐tunable semiconductor fiber ring laser
Authors: Fang Nian , Wang Lu‐Tang , Huang Zhao‐Ming
Published: April 2009

A novel laser with tunable and stable degree of polarization (DOP) is introduced. It consists of a polarization beam splitter (PBS) and a bidirectional semiconductor fiber ring, which is composed of a semiconductor optical amplifier (SOA), a polarization controller (PC) and a 2 × 2 wideband fiber coupler. By adjusting the PC or the injected current of the SOA, the time averaged DOP of the laser output varies optionally from 0.16 to 99%. Employing the bidirectional ring structure and PBS polarization combination method, DOP of the laser can be kept stable at any level in that range. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1669–1671, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24403
Ultra‐wideband bandpass filter using half‐mode T‐septum substrate integrated waveguide with electromagnetic bandgap structures
Authors: Wu Lin‐Sheng , Zhou Xi‐Lang , Yin Wen‐Yan
Published: April 2009

A novel ultra‐wideband (UWB) bandpass filter (BPF) is presented using a half‐mode T‐septum substrate integrated waveguide combined with electromagnetic bandgap structures. When compared with conventional substrate integrated waveguide filters, its width is very small and can work in monomode over the UWB frequency range. The filter performance is demonstrated by our measured S‐parameters and group delay, which agree with the simulated results very well. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1751–1755, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24404
Novel complementary split ring resonantor DGS for low‐pass filter design
Authors: Chen XiaoQun , Weng LiHong , Shi Xiaowei
Published: April 2009

This article has investigated a novel complementary split‐ring resonator (CSRR) defected ground structure (DGS) theoretically and experimentally. The proposed CSRR DGS provides excellent performances including double resonant property, ripple in the passband, sharp selectivity at the cut‐off frequency, and spurious free wide stopband. The equivalent circuit model of the CSRR is also presented. Low‐pass filters using DGS units are fabricated to obtain wide reject band. The measured results show a good agreement with the theoretical analysis. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1748–1751, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24405
Wideband circularly polarized cavity‐backed crossed loop antenna
Authors: Qu Shi‐Wei , Chan Chi Hou , Xue Quan
Published: April 2009

A circularly polarized cavity‐backed crossed loop antenna is proposed in this article. The optimized overall dimensions of the antenna are 1.13λo in diameter and 0.267λo in height (λo is the free‐space wavelength at the center frequency), and the circumference of one loop is 1.1λo. Measurements show that the proposed antenna features an 81% impedance bandwidth for SWR ≤2, a 40% bandwidth for axial ratio ≤3 dB, an average gain of 10 dBi, and stable radiation patterns over the whole band from 1.42 to 2.13 GHz. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1714–1718, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24406
Hollow core photonic band gap fiber for THz applications
Authors: Vincetti Luca
Published: April 2009

In this article, a hollow core photonic band gap fiber is numerically investigated to obtain low‐loss waveguiding in the terahertz region (0.1–10 THz) of the electromagnetic spectrum. Waveguide design in this spectral region is an arduous challenge due to the high‐conductivity losses of metals and high‐absorption of the dielectrics. Numerical results show the possibility to reach propagation loss two decades lower than the bulk absorption losses of the material used to fabricate the fiber, and low dispersion over a wide range of wavelength. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1711–1714, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24407
Millimeter‐wave signal generation utilizing optical‐phase modulation and Brillouin spectral lines suppression
Authors: Jiang Yang , Yu Jinlong , Han Bingcheng , Zhang Li , Zhang Litai , Wang Wenrui , Yang Enze
Published: April 2009

A novel photonic technique to generate millimeter‐wave signal is presented. By utilizing an optical phase modulator driven by a 10 GHz electrical signal, high‐order modulation sidebands are generated on an optical carrier. In addition, a multiwavelength Brillouin fiber laser (BFL) configuration, acted as multitap notch filter, is used to eliminate unwanted modulation sidebands and keep desired harmonic components. Unlike conventional Brillouin selective sideband amplification or other filtering technology, this technique require neither more external light sources to provide Stokes waves nor wavelength matching between light source and filters. The output of the system is dominated by two high‐order sidebands in the optical domain, separated by desired harmonic of the modulation frequency. Signal multiplication is simulated and experimentally demonstrated. The operation range is only limited by the amount of phase shift achieved in the phase modulator. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1683–1685, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24408
Design of time delay lines with periodic microstrip line and composite right/left‐handed transmission line
Authors: Zhang Jun , Zhu Qi , Jiang Qi , Xu Shanjia
Published: April 2009

Time delay lines based on periodic microstrip lines (PMLs) and composite right/left‐handed transmission lines (CRLH‐TLs) are proposed. Compared with ordinary microstrip lines, PMLs are more suitable to realize tiny time delays because of their slow‐wave characteristics. Meanwhile, CRLH‐TLs are chosen to realize large time delays due to their large and easy designable phase constant. Finally, a 9‐bit time delay module is designed and fabricated as an example. It is shown that the present time delay module possesses the advantages of compactness, low‐loss, precise, and easy fabrication. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1679–1682, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24409
Dual‐band bandpass filter based on a hole resonator
Authors: Girbau D. , Lázaro A. , Pérez A. , Pradell L.
Published: April 2009

This article proposes a new dual‐band microstrip resonator, addressed as hole resonator, to be integrated in dual‐band bandpass filters. The main advantage of this structure is that it can be easily coupled in parallel to other resonators since its profile is constant, in contrast with nonconstant profile resonators, such as the stepped‐impedance resonator. Thus, the design process is simpler and less time‐consuming. The hole resonator is characterized by theoretical analysis and validated through electromagnetic simulation and measurements. Finally it is integrated in a bandpass filter to demonstrate its suitability. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1649–1652, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24410
A waveguide cavity 180° hybrid coupler with coaxial ports
Authors: Navarrini Alessandro , Pisanu Tonino , Nesti Renzo
Published: April 2009

We describe the design, construction, and performance of a 180° hybrid coupler for the frequency band 1.3–1.8 GHz (L‐band). The hybrid utilizes a WR650 rectangular waveguide cavity and has three 50 Ω coaxial ports. The signals are coupled in and out of the cavity through broadband coaxial probes attached to 7/16‐type connectors. The measured performances are in excellent agreement with the electromagnetic simulations. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1646–1649, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24411
Substrate‐integrated‐waveguide feed network for microstrip antenna arrays
Authors: Yousefbeigi Mohsen , Shahabadi Mahmoud
Published: April 2009

In this article, a low‐loss parallel‐series feed structure using substrate integrated waveguide (SIW) technology for a single‐layer microstrip antenna array is presented. In addition to reduction of feed radiation, the feed network benefits from typical advantages of planar structures such as compactness, low cost, integrability, and mass‐producibility. A 2 × 8 microstrip antenna array of size 109 mm × 34 mm fed by the proposed SIW feed system is designed and fabricated. Measurements on the fabricated array verify a minimum gain of 17.5 dBi in the frequency range of 17.4 to 18 GHz. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1619–1621, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24412
Terahertz generation and detection setup based on pump‐probe scheme
Authors: Zhou Zhen , Chen An‐Tao , Feng Li‐Shuang , Xin Xiang‐Jun , Yu Chong‐Xiu
Published: April 2009

A terahertz (THz) generation and detection setup based on pump‐probe scheme is presented. THz pulses are generated and detected successfully using nonlinear optical rectification of high power femtosecond laser pulses and electro‐optic sampling. 3 THz available spectrum range is obtained for the setup. The use of THz pulses for spectroscopy is tested by measuring the absorption spectrums of water in air and dry nitrogen, respectively. The measurement results show the setup has a high potential of THz spectroscopy. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1617–1619, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24413
Bandwidth enhancement of multiband handset antennas by opening a slot on mobile chassis
Authors: Zhang Xingyu , Zhao Anping
Published: April 2009

To overcome the shortcoming of narrow bandwidth for traditional planar inverted‐F antenna (PIFA), a novel bandwidth enhancement technique for internal multiband mobile handset antennas is proposed in this article. In particular, a rectangular slot with an appropriate location and a proper size is introduced into the ground plane of the system printed circuit board to improve the bandwidths of handset antennas in both the low‐ (GSM850 and GSM900) and high‐ (DCS1800 and PCS1900) bands. A prototype that can cover the frequency bands of GSM850, GSM900, DCS1800, and PCS1900 simultaneously was fabricated and measured. Good agreement between the measurement and simulation results is achieved. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1702–1706, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24414
A small printed dual‐band antenna for mobile phones
Authors: Kim Jae Hee , Cho Won Woo , Park Wee Sang
Published: April 2009

A small printed antenna is proposed for dual‐band applications. The antenna is patterned on the front of an 0.8‐mm FR4 substrate to obtain a low‐frequency resonance and a stub is patterned on the back of the substrate to obtain a high‐frequency resonance. The antenna without ground plane is small (8 × 35 mm), and it is suitable to operate as an internal antenna. For S11 less than −6 dB, the antenna operates at 900 MHz with a bandwidth of 66 MHz, and at 1.8 GHz with a bandwidth of 130 MHz. Maximum radiation efficiencies were 52% at both 900 MHz and 1805 MHz. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1699–1702, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24415
On the sources reconstruction method application for array and aperture antennas diagnostics
Authors: Las‐Heras Fernando , Galocha Belén , Alvarez Yuri
Published: April 2009

This article presents two practical applications of the Sources Reconstruction Method for antenna diagnostics and antenna manufacturing errors detection. The goal is to show the SRM capabilities to determine defective elements in antenna arrays as well as to detect irregularities in the surface of reflector antennas from the analysis of the aperture fields. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1664–1668, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24416
Compact multilayer dual‐band filter using slot coupled stepped‐impedance‐resonators structure
Authors: Djaiz A. , Nedil M. , Habib A. M. , Denidni T. A.
Published: April 2009

In this article, a new miniaturized configuration of single‐input‐single‐output dual‐band bandpass filter operating at ISM 2.45 GHz and UNII 5.8 GHz frequency bands using a multilayer structure with stepped‐impedance resonators is presented. A coupling aperture is introduced in a common ground to ensure the coupling between the two resonators located in the upper layer and the lower one. The use of stepped‐impedance resonators allows tuning the two bands at desired frequencies. Finally, a design prototype was fabricated to validate the proposed concept. The insertion loss and return loss at the central frequency are −1.35 dB and −17 dB for 2.45 GHz band, and −0.98 dB and −13 dB for the 5.8 GHz band, respectively. There is a good agreement between experimental and full‐wave electromagnetic simulation results. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1635–1638, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24417
In‐line fiber‐optical polarizer with high‐extinction ratios and low‐insertion loss
Authors: Wang Xinyue , Chaojun Wu , Wang Ziyu
Published: April 2009

This letter demonstrated a novel strategy to optimize the extinction ratio and the insertion loss of side‐polished fiber‐optical polarizers. The polarizer has a portion of the cladding polished away and replaced with only a single layer of thin aluminium film. Extinction ratios up to over 22.6 dB/cm and the insertion loss down to 1–2 dB/cm have been realized. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1763–1765, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24418
An experimental investigation of a novel dual‐wavelength single‐longitudinal‐mode fiber laser
Authors: Zhou Yating , Liu Shenchun , Tu Xinghua , Yin Zuowei , Chen Xiangfei
Published: April 2009

A novel continuous‐wave fiber laser is proposed and experimentally studied. Due to its unique configuration, the output of the fiber laser is dual‐wavelength single‐longitude‐mode under relative low‐gain. The wavelength spacing between the two wavelengths can be tunable slightly, which will benefit some applications of the laser. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1760–1763, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24419
Propagation delay matched CMOS 0.18 μm frequency doubler for L‐band application
Authors: Choi Heungjae , Song Kyungju , Jeong Yongchae , Kenney J. S. , Kim Chul Dong
Published: April 2009

In this article, propagation delay matched CMOS frequency doubler for L‐band application is proposed. Schmitt trigger and voltage controlled delay line compensates duty cycle error and propagation delay mismatching that are induced as the frequency of operation is increased. As a consequence, unwanted harmonic components suppression is greatly improved for higher frequency of operation. CMOS frequency doubler is designed at the input fundamental frequency (f0) of 1.15 GHz and fabricated with TSMC 0.18 μm CMOS process. Measured output power at the doubled frequency (2f0) is 2.67 dBm for the input power of 0 dBm. The amount of harmonic suppression for f0, 3f0, and 4f0are 43.65, 38.65, and 35.59 dB, respectively. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1729–1732, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24420
Realization of dual‐dipole‐antenna system for concurrent dual‐radio operation using polarization diversity
Authors: Su Saou‐Wen , Chou Jui‐Hung , Liu Yung‐Tao
Published: April 2009

The study of the mutual coupling between the two simple strip dipole antennas is first carried out and investigated. The results show that the coupling or the antenna port isolation is almost separation distance independent when the two dipole antennas are arranged to be of orthogonal polarization. Following this characteristic, a novel dual‐dipole‐antenna system aimed for concurrent 2.4 and 5 GHz band operation and at the same time, to achieve very compact integration of two individual antennas with separate feeds is proposed. The two dipole antennas are etched on a two‐layered dielectric substrate with dimensions 30 mm × 30 mm. On the front layer is put the 2.4 GHz dipole, which is perpendicular to the 5 GHz dipole located on the bottom layer. Though the two dipoles are stacked up with a distance of 0.8 mm only, port isolation can still be below −15 dB. The proposed dual‐dipole‐antenna system is a promising candidate for the antenna solution that enables simultaneous dual‐radio operation. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1725–1729, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24421
A high‐SFDR direct digital frequency synthesizer with embedded error‐compensation CMOS OTP ROM for wireless receivers
Authors: Huang Chi‐Chun , Jhuang Guo‐Lin , Wang Chua‐Chin
Published: April 2009

A direct digital frequency synthesizer (DDFS) using on‐chip CMOS one‐time programmable read‐only memory (OTP ROM) is presented. A straight‐line approximation algorithm for sinusoid with compensation is adopted such that the accuracy could be maintained and the cost is reduced. Most important of all, a CMOS OTP ROM is used as a look‐up ROM table, which is implemented by a typical logic CMOS process. Therefore, the proposed DDFS can be integrated in any CMOS‐based front‐end circuit for wireless communication systems. The proposed DDFS design is fully implemented using a typical 1P6M 0.18 μm CMOS process. It has a 12‐bit amplitude resolution with 86.89 dB spurious free dynamic range using a small ROM size of 256 bits. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1695–1699, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24422
Broadband patch antenna design using differential evolution algorithm
Authors: Zhang Li , Cui Zhen , Jiao Yong‐Chang , Zhang Fu‐Shun
Published: April 2009

A novel evolutionary algorithm for broadband patch antenna design is presented. The differential evolution algorithm (DE) and the method of moments (MOM) are combined to achieve the optimum antenna satisfying a certain design criterion. The antenna geometric parameters are extracted to be optimized by DE, and a fitness function is evaluated by MOM simulations to represent the performance of each candidate design. A broadband patch antenna is designed using the optimizer. The optimized patch antenna is fabricated and measured to validate the robustness of the algorithm. The measured 38.6% bandwidth exhibits the prospect of the DE/MOM algorithm in practical patch antenna design. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1692–1695, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24423
A novel compact ultrawideband (UWB) bandpass filter using multiple‐mode resonator
Authors: Chen D. , Huang X. D. , Cheng C. H.
Published: April 2009

In this letter, a novel compact ultrawideband (UWB) bandpasss filter (BPF) using the proposed multiple‐mode resonator (MMR) is presented. The MMR is composed of a conventional microstrip hairpin resonator of which the two arms are connected by a section of microstrip line and a short‐circuited point located in the middle of the hairpin resonator. Its first three resonant modes can be utilized to construct the UWB band. The tapped feeding structure has been used to realize desired tight couplings for designing the UWB BPF. The filter has been investigated numerically and experimentally. Both the simulated and measured results show that the filter has good performance, such as compact size, low‐insertion loss, small group delay variation, and improved out‐of‐band performances. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1662–1664, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24424
Material dispersion interplay with spectral filtering on plastic optical fiber (POF) links
Authors: Ribeiro Ricardo M. , Silva Vinicius N. H. , Barbero Andrés P. L.
Published: April 2009

This article reports on the material dispersion interplay with spectral filtering that shifts the bandwidth of Poly‐Methyl‐Metacrylate plastic optical fiber links. Calculations were carried out on fiber lengths up to 500 m and 100 m in length for <600 and 650 nm visible wavelength channels, respectively. The rise time budget evaluation is improved. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1657–1662, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24425
Miniature 60‐GHz‐band bandpass filter with 2.55‐dB insertion‐loss using standard 0.13 μm CMOS technology
Authors: Lu Mei‐Ching , Chang Jin‐Fa , Lu Li‐Chun , Lin Yo‐Sheng
Published: April 2009

In this article, we demonstrate a miniature low‐insertion‐loss 60‐GHz‐band bandpass filter by standard 0.13 μm CMOS technology. Low‐insertion‐loss is achieved by adopting thick microstrip‐line (MSL) with optimized ground‐plane pattern as the needed inductors to minimize the metal and substrate loss. This filter achieved insertion‐loss (1/S21) lower than 3 dB over the frequency range of 56.9–68.6 GHz, input return loss (S11) better than −10 dB over the frequency range of 53.4–71.9 GHz, and output return loss (S22) better than −10 dB over the frequency range of 53.2–70.9 GHz. The minimum insertion‐loss was 2.55 dB at 62.5 GHz. To the authors' knowledge, this is the best result ever reported for a 60‐GHz‐band CMOS bandpass filter in the literature. The chip area was only 0.175 × 0.194 mm2, i.e. 0.034 mm2, excluding the test pads. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1632–1635, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24426
Broadband cloaking with volumetric structures composed of two‐dimensional transmission‐line networks
Authors: Alitalo Pekka , Luukkonen Olli , Mosig Juan R. , Tretyakov Sergei A.
Published: April 2009

The cloaking performance of two microwave cloaks, both based on the recently proposed transmission‐line approach, are studied using commercial full‐wave simulation software. The cloaks are shown to be able to reduce the total scattering cross sections of metallic objects of some restricted shapes and sizes. One of the studied cloaks is electrically small in diameter, and the other is electrically large, with the diameter equal to several wavelengths. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1627–1631, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24427
A tunable triangular microstrip patch antenna for multiband applications
Authors: Lee K.‐M. , Sung Y.‐J. , Baik J.‐W. , Kim Y.‐S.
Published: April 2009

A tunable triangular microstrip patch antenna is proposed for multiband applications in this letter. The proposed antenna consists of varactor diodes and F‐shaped slits. As the input impedance of the antenna can be varied by changing the bias voltage of the varactor diode on the F‐shaped slits, the resonant frequency may be changed. The designed antenna has return losses better than 20 dB within 1.95–2.16 GHz. The peak gains of the antenna present 2.87 and 3.1 dBi at the both ends of the above frequency range. Details of the antenna design are described. Its performances are also presented. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1788–1790, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24428
Internal multiband monopole antenna for wireless‐USB dongle application
Authors: Park Piljun , Choi Jaehoon
Published: April 2009

An internal multiband monopole antenna for application in a USB dongle is proposed. The antenna consists of two metal strips which are constructed of a dielectric substrate and have a volume of 20 mm × 10 mm × 1 mm. The multiband characteristic is obtained by using a folded meander strip on the top side of the substrate, and the wideband performance in the lower band is achieved by connecting an inverted L‐shaped stub to the ground. The measured bandwidths were 26.1% (1.7–2.9 GHz) in the lower band for the DCS‐1800, US‐PCS, WCDMA, WiMax, 2.4 GHz‐WLAN, and S‐DMB bands and 15.5% (5.05–5.9 GHz) in the upper band for the 5 GHz‐WLAN band. Nearly omnidirectional radiation patterns and reasonable antenna gains were obtained in the desired frequency bands. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1786–1788, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24429
Reconfigurable patch with switchable conductive edges
Authors: Haupt Randy L.
Published: April 2009

This article demonstrates the use of materials with variable conductivity on the edges of a rectangular patch antenna to change the resonant frequency. The dimensions of the patch and edge material are numerically optimized to create resonances at four microwave frequencies. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1757–1760, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24430
Compact dual‐frequency double T‐shaped slot antenna for RFID application
Authors: Zhang Li , Jiao Yong‐Chang , Song Kun , Zhang Fu‐Shun
Published: April 2009

A novel compact double T‐shaped slot antenna is introduced to achieve a dual‐frequency for radio frequency identification (RFID) applications. The designed antenna with an overall dimension of only 33.5 × 12.5 mm2 is low in profile and can operate simultaneously at 2.45 and 5.8 GHz bands. Also, good omnidirectional radiation patterns have been obtained. Its properties make the antenna not only suitable for RFID tags but also for WLAN applications. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1755–1757, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24431
A miniature X‐band‐embedded multilayer band‐pass filter using LTCC technology
Authors: Wang Zhigang , Yan Bo , Xu Ruimin , Lin Weigan
Published: April 2009

This article proposes a miniature embedded multilayer interdigital bandpass filter (BPF) based on low temperature co‐fired ceramic (LTCC) technology, which is used to suppress fundamental and harmonic components of local‐oscillator signal in a LTCC transceiver module. A practical design methodology corresponding to LTCC multilayer configuration is described. A five‐order Chebyshev interdigital BPF is developed and verified by full‐wave simulation. The proposed filter is fabricated using multilayer LTCC technology and measured using vector network analyzer. Good agreement between simulated and measured response is observed. Covering area of the fabricated BPF is only 8.1 × 7.4 mm2 (including via fences). © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1722–1725, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24432
Gilbert upconversion mixers using single‐band/dual‐band LC current combiners
Authors: Syu Jin‐Siang , Meng Chinchun , Yen Ying‐Chieh , Huang Guo‐Wei
Published: April 2009

The 0.35‐μm SiGe BiCMOS high linearity Gilbert upconverters are demonstrated in this article by utilizing NMOS and PMOS transconductance amplifiers (TCAs), respectively. To improve the linearity of a Gilbert upconverter, the IF input TCA is replaced by a bias‐offset differential pair. A reactive LC current combiner is used as the load of the Gilbert mixer to double the output current. The upconverter with an NMOS TCA achieves the conversion gain of −4 dB, the OP1dB of −11 dBm, and the OIP3 of 5.5 dBm, whereas the other one with a PMOS TCA has the conversion gain, OP1dB, and OIP3 of −6 dB, −11 dBm, and 9.5 dBm, respectively. Furthermore, the LC current combiner can be extended to a dual‐band version. The 2.4/5.7 GHz dual‐band upconverter is also demonstrated in this work. The conversion gain at 2.4/5.7 GHz is −3/−3.5 dB with the OP1dB of −15.5/−15 dBm and the OIP3 of −2.5/−3 dBm, respectively. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1718–1722, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24433
Optical fiber AC voltage sensor
Authors: Kim Soobong , Park Jaehee , Han Won‐Taek
Published: April 2009

A fiber‐optic interferometric voltage sensor with a high‐sensitivity is investigated. The fiber‐optic voltage sensor is composed of an in‐line Michelson interferometer bonded to a piezoelectric transducer (PZT). The in‐line Michelson interferometer is a hollow optical fiber spliced to a single‐mode fiber at one end and cleaved at the other end. A phase shift in the sensor output signal is induced when applying an AC voltage to the PZT; and a higher‐amplitude voltage produces an output interference signal with a higher frequency. The relation between the amplitude of the applied voltage and the phase shift of the sensor output signal is found to be approximately linear and the slope of the relation graph is about 0.116 πradian/V. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1689–1691, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24434
A novel multilayered cross‐coupled substrate‐integrated waveguide (SIW) circular cavity filter in LTCC
Authors: Wei Qi‐Fu , Li Zheng‐Fan , Wu Lin‐Sheng , Li Lin
Published: April 2009

A novel multilayered cross‐coupled substrate‐integrated waveguide (SIW) circular cavity filter is proposed in this letter. The filter is designed using standard low‐temperature co‐fired ceramic (LTCC) technology, with the fractional bandwidth of 0.25% obtained, can operate at 20 GHz and have two finite frequency transmission zeros at 19.51 and 20.51 GHz, respectively. Measured results show good agreement with simulated results and validate the structure of the proposed filter. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1686–1689, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24435
Experimental demonstration of a clock recovery scheme utilizing nonlinear relaxation oscillation in directly modulated lasers
Authors: Yan Minhui , Chen Chih‐Hung , Xu Qing‐Yang , Huang Wei‐Ping
Published: April 2009

An experimental demonstration was presented for a clock recovery scheme suitable for low‐cost short‐haul optical communications. This scheme utilizes the nonlinear relaxation oscillation in a directly modulated laser, which creates clock information in modulated nonreturn‐to‐zero optical signals. At the receiver, an injection locked oscillator is employed to extract and restore the clock. Eye diagrams of both received data signal and recovered clock demonstrate the capability of recovering clock from the data signal with an almost closed eye at ∼9 Gbps. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1654–1657, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24436
Low‐profile dielectric resonator antenna with high‐permittivity for application in WiMAX
Authors: Chen Yih‐Chien , Chen Kai‐Hao
Published: April 2009

In this article, the measurement results of the dielectric resonator antenna with high‐permittivity have been presented. With this technique, a 5.4% bandwidth (return loss < −10 dB) of center frequency at about 3.5 GHz for application in WiMAX has successfully been achieved. The copolarization radiation is strongest at θ ≅ 5° from the broadside in the E‐plane. The cross‐polarized patterns are about 10 dB less than the copolarized patters in the broadside direction. The antenna has a 3 dB beam angle of about 80°. Peak antenna gain is about 5.96 dBi, with gain variations less than 1.0 dBi for frequencies within in the −10 dB S11 bandwidth. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1652–1654, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24437
A wideband circularly polarized microstrip antenna array with single feeding
Authors: Yao Ping , Yu Yang , Che Wenquan , Chen Wentao
Published: April 2009

In this article, one wideband circularly polarized microstrip antenna array has been proposed and investigated. The technique of sequential rotation subarray has been employed to construct the whole antenna array, which enhances the impedance bandwidth and axial ratio (AR) bandwidth by 54.65 and 220.93%, respectively, when compared with the traditional way of CP array formation. One 8 × 4 antenna array has been fabricated and measured, agreement can be observed between the experimental and simulation results, the measured VSWR bandwidth is 7.33%, the AR bandwidth is 4.31%, and the gain is about 19 dB. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1624–1627, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24438
Embedded dual fiber Bragg grating sensor for simultaneous measurement of temperature and load (strain) with enhanced sensitivity
Authors: Mondal Samir K. , Mishra Vandana , Tiwari Umesh , Poddar G. C. , Singh Nahar , Jain Subhash C. , Sarkar S. N. , Kapur Pawan
Published: April 2009

An embedded dual fiber Bragg gratings sensor for simultaneous measurement of temperature and load (strain) is proposed and experimentally demonstrated. Two nearly identical gratings are mounted on opposite side of an arch‐shaped steel strip. The grating in concave and convex position experiences equal blue and red shift, respectively, due to bending of the strip which is exploited in temperature and load (strain) discrimination. The temperature and load (strain) sensitivity of the sensor improves to 28.5 pm/°C and 2.8 pm/g (2.6 pm/με). The sensor can measure temperature and load (strain) accurately with small error of ±1°C and ±1 g, respectively. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1621–1624, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24439