bluuebunny/crossref_metadata_2025 huggingface dataset:
Compact wideband bandpass filters using rhombus‐shaped triple‐mode resonator
Authors: Wong Sai Wai , Zhu Lei
Published: June 2009

A novel compact wideband bandpass filter is proposed using a stub‐loaded triple‐mode resonator (TMR) with rhombus configuration. This TMR is formed by shunt‐loading a stepped‐impedance stub at the center of a half‐wavelength resonator. As this TMR is driven in its two sides by two identical quarter‐wavelength parallel coupled lines, a wideband passband with a fractional bandwidth 80% is achieved. With the help of a two‐section stub, two transmission zeros are excited near the lower and higher cut‐off frequencies so as to sharpen the roll‐off skirt of the passband. A two‐stage filter is finally designed to enhance the rejection skirts. Measured results for the two fabricated filters confirm the predicted results with sharp rejection skirt and wideband performances. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2107–2109, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24536
An efficient finite element‐boundary integral method solving electromagnetic scattering problems
Authors: An Xiang , Lü Zhi‐Qing
Published: June 2009

The “conventional” finite element‐boundary integral (FE‐BI) method suffers from two major drawbacks, one is the huge computer resources required by the dense BI submatrix; the other is the slow convergence rate of the resulting linear system of equations. In this article, both the drawbacks are investigated. First, the integral equation fast Fourier transform (IE‐FFT) algorithm with a Gaussian interpolation scheme is employed to deal with the BI part. Second, an effective and simple preconditioner is developed for solving the matrix equation obtained from FE‐BI method. Numerical results show that the proposed preconditioner can dramatically speed up the convergence of the FE‐BI system, whatever the combined field integral equation (CFIE), the electric field integral equation (EFIE), and the magnetic field integral equation (MFIE) are employed on the truncation boundary. Some examples are given to demonstrate the accuracy and efficiency of the method. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2065–2071, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24538
A 5‐GHz low‐phase noise CMOS VCO with swing boosting technique
Authors: Liu Junhua , Liao Huailin , Huang Ru
Published: June 2009

A 5‐GHz CMOS VCO with improved phase noise is proposed in this article. A gate voltage boosting technique is realized with only one inductor. The proposed VCO is fabricated in 0.18 μm CMOS process, and the measured phase noise is −122.7 dBc/Hz@1 MHz when operates at 4.936 GHz, with a power dissipation of 5.28 mW from 1 V supply. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2061–2064, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24539
Double dipole antenna for dual‐band wireless local area networks applications
Authors: Steyn Johanna M. , Odendaal Johann W. , Joubert Johan
Published: June 2009

A double‐dipole antenna design is proposed for wireless local area network (WLAN) applications. Two parallel dipoles are used to facilitate operation in both the standard WLAN frequency bands (IEEE 802.11b and IEEE 802.11a) simultaneously. The lower band dipole is rhombus shaped and radiates above a planar ground plane, whereas radiation from the rectangular higher band dipole is directed through the use of a passive director. The antenna is characterized in terms of impedance bandwidth, gain and radiation patterns through simulations and measurements. The design addresses the need for dual‐band operation, whereas delivering directional radiation patterns with adequate gain, low cross‐polarization, and good front‐to‐back ratio. The 2.4/5 GHz WLAN bands are covered with an impedance bandwidth of 17.8 and 26.4%, respectively, for a VSWR better than 2:1. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2034–2038, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24540
Extraction of CAD‐compatible statistical nonlinear models of GaAs HEMT MMICs
Authors: Centurelli Francesco , Di Martino Alberto , Scotti Giuseppe , Tommasino Pasquale , Trifiletti Alessandro
Published: June 2009

In this article, a statistical nonlinear model of GaAs HEMT MMICs based on standard CAD library models is presented. A previously developed extraction procedure is used to determine model parameters. Extraction and CAD implementation of the model in 1–50 GHz frequency range provide validation of both the statistical model and the extraction procedure. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2163–2166, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24543
Compact tunable periodically LC loaded phase shifter using left‐handed transmission line
Authors: Sheng Su , Wang Peng , Ong C. K.
Published: June 2009

In this article, a compact tunable periodically LC loaded phase shifter using left‐handed transmission line is presented. The unique nature of left‐handed transmission line metamaterials enables reduced size, compared to conventional loaded line phase shifters realized as right‐handed transmission lines. The phase shifter based on four unit cells provides 0°–280° continuous phase shift at 7.2 GHz from 0 to 6 V. Measured figure of merit is 78°/dB using the highest insertion loss. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2127–2129, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24544
Linearity enhancement of analog optical transmitter using gain saturated reflective semiconductor optical amplifier
Authors: Piao Yin‐Xing , Won Yong‐Yuk , Han Sang‐Kook
Published: June 2009

We propose a new linearization scheme in optical external modulator employing high‐pass filter characteristic of a gain saturated reflective semiconductor optical amplifier for an analog optical transmission system. The proposed scheme is based on power level relation between fundamental signal and IMD3 signal when a radio‐frequency tone is modulated, using an optical modulator at linearity region of transfer curve. Based on the proposed idea, a linearized optical transmitter module is implemented and evaluated. The proposed scheme is demonstrated and verified using a small scale test‐bed. Both carrier‐to‐interference ratio and spurious‐free dynamic range are improved. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2100–2103, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24545
Frequency selective surface with dual band switchable reflection and transmission characteristics
Authors: Munir A. , Fusco V.
Published: June 2009

A pin diode‐loaded active doubly periodic flat strip FSS is shown to act as a dynamic screen. It is shown that by means of d.c. bias control, we can utilize the screen in, (1) transmission mode as a dual band electromagnetic shutter, or with the inclusion of a ground plane in reflection mode, as (2) a dual band refection canceller, (3) an amplitude shift keying (ASK) spatial modulator. The properties of the FSS are characterized using a specially designed parallel plate waveguide simulator that permits normal incidence excitation of the FSS under test. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2059–2061, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24547
Environmentally stable nonlinear optical polarization switching by using a nonreciprocal all‐optical circuit
Authors: Kishi Naoto , Ehsan Ul Islam
Published: June 2009

We proposed and demonstrated a stable nonlinear optical polarization self‐switching based on nonreciprocal nonlinear phase shift induced by self‐phase modulation in optical fiber. The polarization self‐switching was achieved at input power levels of around 10 mW in a nonreciprocal circuit using Faraday rotator mirrors. This nonlinear polarization switching is quite stable against polarization fluctuation caused by environmental perturbation. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2056–2059, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24548
PA and LNA for millimeter‐wave WPAN using 90 nm CMOS process
Authors: Kang Min‐Soo , Kim Bong‐Su , Byun Woo‐Jin , Kim Kwang‐Seon , Oh Seung‐Hyeub , Pinel Stephane , Laskar Joy , Song Myung‐Sun
Published: June 2009

We present the design and fabrication of power amplifier (PA) and low noise amplifier (LNA) in 60 GHz using 90 nm CMOS process. Both of them have three stages topology. We obtained small signal gain of 21 dB, P1dB of 4 dBm, and input/output return losses of <−9 dB in PA. We also obtained small signal gain of 25 dB, noise figure of <7 dB, P1dB of 1.5 dBm, input/out return losses of <−8 dB in LNA. The die sizes of PA and LNA are 1.1 × 0.8 mm2 and 0.59 × 0.78 mm2, respectively. Both sizes contain the RF pads and bias pads. Especially, the size of LNA is reduced by using hairpin type matching structure. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2029–2032, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24549
Tunable dual‐band bandpass filter for WLAN applications
Authors: Girbau David , Lázaro Antonio , Martínez Esther , Masone Diego , Pradell Lluís
Published: June 2009

This article proposes the design of tunable dual‐band filters for multiband multistandard systems, specifically for wireless local‐area network applications. The two main goals are to provide frequency tunability in the second band while maintaining the first band fixed and to obtain a structure capable of offering a ratio between the second and first passband center frequencies larger than 2. To this end, a capacitively loaded stepped‐impedance resonator is proposed for integration in dual‐band filters. A detailed analysis of the resonator is provided. A filter has been designed to validate the concept. It demonstrates operability in wireless local‐area network frequency bands, with a fixed first band at 2.45 GHz and a second band which can be tuned between 5.75 GHz and 5.25 GHz. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2025–2028, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24550
Multiband ladder‐shaped monopole antenna for digital television and wireless communications
Authors: Liu Wen‐Chung , Huang Der‐Lun
Published: June 2009

A multiband monopole antenna covering DTV and several popular wireless communications was presented. The antenna fed by a microstrip line comprises a ladder‐shaped patch and a notched ground plane. By precisely choosing the dimensions of both the patch and the ground, dual wide continuous impedance bandwidths of 880 MHz (0.51–1.39 GHz) and 1.66 GHz (2.11–3.77 GHz) applicable for multiband wireless operation can be easily achieved. Also, the monopole‐like type of radiation patterns and the average gains of about 0.1 and 4.5 dBi, respectively, over the lower and upper operating bands have been obtained. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2124–2127, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24555
Design of a stopband‐improved UWB filter using a pair of shunt and embedded open stubs
Authors: Weng Min‐Hang , Kuan Hon , Chen Wen‐Lang , Ye Chang‐Sin , Su Yan‐Kuin
Published: June 2009

In this letter, an ultrawideband (UWB) bandpass filter (BPF) with an improved stopband has been proposed. The proposed UWB BPF, having a lower passband of 3.5–5.2 GHz and a higher passband of 6.5–9.7 GHz, mainly comprises the parallel‐coupled lines and slot‐line resonator. A wide stopband of the proposed BPF from 10 to 20 GHz can be achieved by using a pair of shunt and embedded open stubs. The proposed UWB BPF is designed, fabricated, and measured. Good agreement with the electro‐magnetic simulation and measurement is demonstrated. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2121–2124, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24556
Full‐wave analysis of antenna‐array mutual coupling using the FETI‐DEPM algorithm
Authors: Li Yu‐Jia , Jin Jian‐Ming
Published: June 2009

The electromagnetic dual‐primal finite‐element tearing and interconnecting (FETI‐DPEM) algorithm is applied to the three‐dimensional (3D) full‐wave analysis of mutual coupling between antenna arrays mounted on a large platform. For large antenna arrays with repeated unit cells, the geometrical repetition is fully utilized to reduce the computation time and memory requirements. For general antenna arrays without geometrical repetitions, the full‐wave simulation using the FETI‐DPEM algorithm is accelerated through parallel computation. The numerical scalability of the algorithm ensures a high‐parallel efficiency on both shared‐ and distributed‐memory systems. Curvilinear tetrahedral elements, higher‐order vector basis functions, and port boundary conditions are employed in the finite‐element formulation to accurately model the geometry and the fields in antennas and feeds. Simulations of antenna arrays on large platforms using the FETI‐DPEM algorithm are carried out to demonstrate the efficiency and capability. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2088–2093, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24558
Hybrid approach for efficient calculation of the parallel‐plate impedance of lossy power/ground planes
Authors: Rimolo‐Donadio Renato , Brüns Heinz‐D. , Schuster Christian
Published: June 2009

Two different approaches to calculate analytically the impedance of rectangular power planes of printed circuit boards and package structures (parallel‐plate impedance) are discussed, namely, the cavity resonator model and the radial waveguide approach. Both methods are compared and it is shown that they can be combined to improve the efficiency of the computation over a broad frequency range. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2051–2056, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24559
Negative index metamaterials composed of triangular open‐loop resonator and wire structures
Authors: Zhu Cheng , Ma Jing‐Jing , Chen Liang , Liang Chang‐Hong
Published: June 2009

This article presents a new type of left‐handed materials composed of two kinds of triangular open‐loop resonators (TOLRs) and wires. Parameter retrieval algorithm, prism simulations, and the transmission experiments all have been carried out to validate the left‐handed characteristic of TOLR‐wire structures. The negative refraction indices obtained by prism simulations are in good agreement with the retrieval results. Besides, the transmission experiments show that each transmission peak does appear in each negative index frequency region, which confirm the left‐handed characteristic of those two kinds of structures. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2022–2025, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24561
Analytical shielding effectiveness model of metal foams for high frequency
Authors: Losito Onofrio
Published: June 2009

The applications of metal foam in the last years continues to grow up in terms of research and application even in electromagnetic environment. An analytical 3D model of metal foams is developed and discussed in this article to characterize the electromagnetic shielding behavior, showing good agreement results with this model, some prototype of this model, and experimental measurements of metal foams. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2189–2193, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24563
A theoretical basis for Doherty amplifier bias control based on drain current characteristics
Authors: Smith Karla J.I. , Eccleston Kimberley W. , Gough Peter T. , Mann Stephen I.
Published: June 2009

This article introduces a gate bias control scheme for Doherty amplifiers, based on the measured gate‐voltage to drain‐current transfer characteristics of the FETs used, and their ideal fundamental output currents. An amplifier was realized at 800 MHz, and achieved over 35% drain efficiency from 8–14 dBm input power. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2152–2156, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24565
Optimization and modeling for MOS varactors in 65 nm low‐power mixed‐signal/radio‐frequency technology
Authors: Chen Chia Chung , Jiang Meshon , Chang Li Ming , Yeh Tzu Jin , Liu Feng Ming , Liu Sally
Published: June 2009

CMOS technology scaling opens up the possibility of designing variable capacitors based on a metal oxide semiconductor (MOS) structure with improved tuning range and quality factor. In this work, the high Q‐factor 24 and 21, wide tuning ratio 45% and 36% can be achieved by 65 nm low power technology n+/n‐well and p+/p‐well MOS varactor up to 10 GHz, respectively. Meanwhile, the equivalent circuit model, to model intrinsic and extrinsic parameters of MOS varactor, also have demonstrated that parasitic resistance is a main issue to dominate Q‐factors, and the measured flicker noise result of MOS varactor is directly dependant on gate leakage current. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2119–2121, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24567
Implementation of parallel GMRES(m) FFT method for solving large scale electromagnetic problems
Authors: Zhang Ming , Yeo Tat Soon , Li Le Wei
Published: June 2009

In this article, the parallel restarted generalized minimum residual [GMRES(m)] scheme has been implemented to solve large scale multilevel block Toeplitz matrix equations. The parallel fast Fourier transform has been used to accelerate the matrix‐vector multiplications in the iterative solver. The numerical results of electromagnetic scattering by cylindrical wire arrays demonstrate the accuracy and efficiency of the parallelization scheme. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2084–2087, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24569
A compact slot‐coupled dual‐band RFID tag antenna
Authors: Zeng Rui‐Hua , Chu Qing‐Xin
Published: June 2009

A slot‐coupled dipole antenna is presented for dual‐band passive radio frequency identification (RFID) tag application. A structure using a slot‐coupled feed is explored to achieve dual‐band operation. The proposed antenna satisfies the −10 dB return loss characteristics from 840 to 940 MHz (11%) for ISO 18000‐6 and from 2.26 to 2.56 GHz (12%) for ISO 18000‐4 applications, respectively. The simulated and measured return loss results are in good agreement. Also reasonably good radiation characteristics are obtained for 900 MHz and 2.45 GHz RFID bands. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2046–2048, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24571
A dual‐band Wilkinson power divider with bandwidth enhancement
Authors: Xi Li , Yang Lin , Gong Shu‐xi , Yang Yan‐jiong
Published: June 2009

The design and analysis of a novel dual‐band equal‐split Wilkinson power divider are presented in this article. The proposed structure has no extra lumped and distributed elements. Moreover, the measured bandwidth of the proposed structure is more than 240 MHz for S11<‐20 dB. The formulas used to determine the design parameters have been given. Closed‐form design equations are derived using Z‐parameters matrix. For verification, a microwave power divider operating at 1 and 2.6 GHz is fabricated, the experimental results show that the designed power divider fulfills all the features of a conventional Wilkinson power divider, such as an equal power split and impedance matching at ports. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2043–2046, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24572
90‐Degree H‐plane bent waveguide using dielectric rods
Authors: Kokubo Yoshihiro , Kawai Tadashi
Published: June 2009

Conventional rectangular metallic waveguides are seldom used at frequencies higher than twice cutoff because of higher mode propagation. However, single‐mode propagation can occur for a metallic waveguide composed of an array of dielectric rods. An efficient way to construct one is to introduce dielectric rods at the bent portions because mode conversion does not occur in straight segments. As an example of the ease of fabrication, holes can be drilled at the top of a waveguide and dielectric rods inserted. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2015–2017, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24573
CPW‐fed dual‐mode resonators with double‐ring and double‐square‐loop for dual‐band applications
Authors: Liu Ji‐Chyun , Wang Jhih‐Wei , Kuei Ching‐Pin , Zeng Bing‐Hao
Published: June 2009

The CPW‐fed configurations of dual‐mode double‐ring resonator (DMDRR) and double‐square‐loop (DMDSLR) are introduced to achieve the performance of the dual‐band filters. To obtain lower insertion loss, higher out‐of‐band rejection level, and wider band of DMDRR and DMDSLR filters, using two twin‐T couples and dual‐mode perturbations are proposed here. Simulation and measurement results including surface current distributions and frequency responses are presented and discussed. It can be applied to 0.9 and 1.2 GHz dual‐band systems. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2010–2015, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24574
Compound field integral equation approach for analyzing quasi‐waveguide structures
Authors: Golestanirad Laleh , Mattes Michael , Mosig Juan R.
Published: June 2009

In this article, a compound field integral equation approach has been applied to analyze the problem of quasi‐waveguide structures, that is, structures consisting of a main waveguide with a constant cross section that may bear an arbitrary number of printed circuits backed by dielectric substrates. A detailed mathematical procedure is described to retrieve modal scattering parameters conventionally defined in planar multilayered structures excited by wave ports. In the case that the structure as well as the excitation holds symmetry requirements, simplifications may be applied to considerably improve the usage of computational resources. Formulations providing the theoretical background for applying symmetry conditions have also been developed in the context of this work. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2181–2186, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24575
Design of CMOS T/R switch using high‐substrate isolation and RF floated body for 1.9‐GHz applications
Authors: Lin Yih‐Hsia , Chu Chun‐Hsueh , Chang Da‐Chiang , Gong Jeng , Juang Ying‐Zong
Published: June 2009

In this work, two single‐pole, double‐throw CMOS transmit/receive (T/R) switches are designed for 1.9‐GHz application. Of the two T/R switches, one adopts single‐transistor architecture; the other adopts transistor‐stacking architecture to get a higher power‐handling capability. Both of the T/R switches make use of optimized transistor sizes to inherently achieve low‐insertion loss. In addition, techniques including high‐substrate isolation between transistors and RF floated body are used to further enhance the input 1‐dB compression point (IP1dB) and reduce the insertion loss of the T/R switches. The T/R switch with stacking architecture achieves a measured IP1dB of 23.5 dBm and an insertion loss of 1 dB at 1.9 GHz. The T/R switch using single‐transistor architecture achieves a very low‐insertion loss of 0.57 dB and a measured IP1dB of 21.6 dBm at 1.9 GHz. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2145–2149, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24577
Bandwidth enhancement of a quarter‐wavelength slot antenna by capacitive loading
Authors: Liu Zidong , Boyle Kevin
Published: June 2009

In this article, a novel wideband slot antenna is proposed. The slot is quarter‐wavelength long and loaded with a capacitor to increase its bandwidth. The effect of the capacitor on the antenna radiation efficiency is also investigated. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2114–2116, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24579
A low‐power wideband CMOS low‐noise amplifier using current‐reuse technique
Authors: Hsu Meng‐Ting , Lin Shih‐Kai
Published: June 2009

A CMOS low noise amplifier (LNA) for low‐power ultra‐wideband wireless applications is presented. To achieve low power consumption and wide operating bandwidth, the proposed LNA uses a current‐reused technique and a simple high‐pass input matching network. This work is implemented in 0.18‐μm CMOS process technology and shows a 3.1–10.6 GHz bandwidth. With only 1.5 V supply voltage, the LNA can achieve power flat gain of 13.2 dB with input matching of −10.3 dB, the minimum noise figure of 3.33 dB, and input third‐order‐intercept point (IIP3) of −3.3 dBm. The power dissipation is only 9.3 mW. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2077–2080, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24581
Small‐size microstrip‐coupled printed PIFA for 2.4/5.2/5.8 GHz WLAN operation in the laptop computer
Authors: Wong Kin‐Lu , Chen Wei‐Ji
Published: June 2009

With a microstrip‐coupled feed, a small‐size (9 × 10 mm2) printed PIFA capable of generating two wide bands to cover WLAN operation in the 2.4 GHz and 5.2/5.8 GHz bands for laptop computer application is presented. The PIFA is easily printed on a thin, inexpensive FR4 substrate at low cost. Although, the printed PIFA provides a resonant path of about 20 mm only (about 0.16 wavelength at 2.4 GHz), far less than the required resonant length for the conventional quarter‐wavelength mode excitation and hence showing large inductive reactance at around 2.4 GHz, the applied microstrip‐coupled feed in this study effectively compensates for it to result in a resonance (zero reactance) at about 2.4 GHz. A desired resonant mode for covering 2.4 GHz WLAN operation is thus excited for the proposed small‐size printed PIFA. In addition, a higher‐order resonant mode at about 5.5 GHz is also generated to cover the 5.2/5.8 GHz WLAN operation. Details of the proposed PIFA are described, and results of the fabricated prototype are presented and discussed. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2072–2076, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24582
Broadband small‐size wire cone antenna
Authors: Kyi Yu Yu , Jianying Li
Published: June 2009

The broadband characteristic of wire cone antenna is presented in this article. The size reduction of top loading wire cone antenna is done by using inductive posts and lumped resistor loading. The broadband result of frequency span from 100–800 MHz over of VSWR < 2 was obtained. The wire cone antenna with top capacitive loading and resistor loading design was fabricated, and the measured results are compared with the simulation results. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2040–2043, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24583
Lateral and axial displacements measurement using fiber optic sensor based on beam‐through technique
Authors: Yasin M. , Harun S. W. , Fawzi W. A. , Kusminarto  , Karyono  , Ahmad H.
Published: June 2009

The performance of the fiber‐optic displacement sensor with beam‐through detection technique is investigated. The effects of lateral and axial displacements on the detected output voltage are investigated for various core's diameters of the sensor. The highest sensitivity is obtained at 0.0008 mV/μm for the lateral displacement with core's diameters for both transmitting and receiving fibers are fixed at 0.5 mm. At present, the widest linear range is obtained at 3195 μm for the axial displacement with 1.0 mm core's diameters for both fibers. The highest resolution of the 13 μm is obtained with the lateral displacement sensor with 0.5 mm core diameter. The sensor with the smaller core shows a better sensitivity and resolution with the expense of the smaller linear range. The beam‐through sensors have a simple design, high degree of sensitivity and dynamic range, and low cost. These make the sensors are useful for microdisplacement measurement in the hazardous region. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2038–2040, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24584
An independently tunable second‐passband by spiral open stubs in dual‐band HTS filter design
Authors: Li Mingjie , Jin Shichao , Guo Xubo , Wei Bin , Zhang Xiaoping , Cao Bisong , Gao Baoxin
Published: June 2009

This article presents a novel dual‐band HTS filter using open‐loop stepped impedance resonators (SIRs) and λ/4 spiral open stubs. The center frequencies of the two passbands are determined by the structure of the SIRs. By introducing the λ/4 spiral open stubs, the external quality factor of the second passband can be tuned independently without influence on that of the first one. The measured results of the filter at 77 K are in good agreement with the simulated ones. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2007–2010, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24585
A CMOS fully integrated concurrent dual ultrawideband receiver frontend
Authors: Chirala Mohan K. , Nguyen Cam
Published: June 2009

A new fully integrated receiver front‐end operating concurrently over the two bands of 3.1–4.8 and 6.3–7.9 GHz of the UWB spectrum (3.1–10.6 GHz) has been developed using a 0.18‐μm CMOS process. The receiver front‐end occupies a chip size of only 1.18 × 0.87 mm2and exhibits conversion gains from 12.5–16.5 dB and 14.5–16 dB and RF return losses from 10 to 11 dB and 10.5 to 12 dB over the 3.1–4.8 GHz and 6.3–7.9 GHz bands, respectively. The measured input 1‐dB compression points are −4.1 and −5.2 dBm at 4 and 6.5 GHz, respectively. The measured noise figure is from 7.5 to 12.5 dB across 3.1–7.9 GHz and less than 10 dB up to 7 GHz. The receiver front‐end consumes about 42 mA of current from a 1.8 V power supply. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2003–2007, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24586
Wideband integrated CPS‐fed dual polarized quasi bow‐tie antenna
Authors: Vahdani Mohammad , Begaud Xavier
Published: June 2009

A wideband integrated dual polarized bow‐tie antenna using an optimized microstrip‐to‐CPS transition has been presented in this article. This antenna has been designed and fabricated in a very compact geometry with overall dimensions of 1.1λL × 1.1λL × 0.015λL where λL is the wavelength at the lowest operating frequency. Measurement and simulation results show wideband behavior in dual polarization with return loss better than 10 dB from 5.4 to 12 GHz. The radiation patterns show good symmetrical patterns in E‐ and H‐plane. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2130–2136, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24588
Solving the steady‐state groundwater flow equation for finite linear aquifers using a generalized Fourier series approach in two‐dimensional domains
Authors: Capilla Jose E. , Pulido‐Velazquez David , Sahuquillo Andrés , Andreu Joaquín
Published: June 2009

A method to solve steady linear groundwater flow problems using generalized Fourier Series is developed and particularized for multiple Fourier series in two‐dimensional domains. It leads to a linear vector equation whose solution provides a finite number of generalized Fourier coefficients approximating the hydraulic head field. Its implementation is shown and two relevant properties are found for the system matrix. It is always symmetric and, once computed, if additional Fourier terms are needed for a better approximation of the hydraulic head field, previously computed matrix elements remain invariant, i.e. only new rows and columns are added to the system matrix. The method is demonstrated in three simple cases with different geometries and transmissivity fields, where solutions are compared with analytical and finite element method results. Thus, the method is verified as an alternative to other flow solvers. Additionally, it provides a direct way to obtain the spectral form of the flow equation solution, given a spectral representation of transmissivity, and can be easily extended to obtain continuous velocity fields and their approximated spectral expressions. Copyright © 2009 John Wiley & Sons, Ltd.
A Padé‐based factorization‐free algorithm for identifying the eigenvalues missed by a generalized symmetric eigensolver
Authors: Avery P. , Farhat C. , Hetmaniuk U.
Published: June 2009

When computing the solution of a generalized symmetric eigenvalue problem of the form Ku=λMu, the Sturm sequence check, also known as the inertia check, is the most popular method for reporting the number of missed eigenvalues within a range [σL,σR]. This method requires the factorization of the matrices K−σLM and K−σRM. When the size of the problem is reasonable and the matrices K and M are assembled, these factorizations are possible. When the eigensolver is equipped with an iterative solver, which is nowadays the preferred choice for large‐scale problems, the factorization of K−σM is not desired or feasible and therefore the inertia check cannot be performed. To this effect, the purpose of this paper is to present a factorization‐free algorithm for detecting and identifying the eigenvalues that were missed by an eigensolver equipped with an iterative linear equation solver within an interval of interest [σL,σR]. This algorithm constructs a scalar, rational, transfer function whose poles are exactly the eigenvalues of the symmetric pencil (K, M), approximates it by a Padé expansion, and computes the poles of this approximation to detect and identify the missed eigenvalues. The proposed algorithm is illustrated with an academic numerical example. Its potential for real engineering applications is also demonstrated with a large‐scale structural vibrations problem. Copyright © 2009 John Wiley & Sons, Ltd.
An energy approach to space–time Galerkin BEM for wave propagation problems
Authors: Aimi A. , Diligenti M. , Guardasoni C. , Mazzieri I. , Panizzi S.
Published: June 2009

In this paper we consider Dirichlet or Neumann wave propagation problems reformulated in terms of boundary integral equations with retarded potential. Starting from a natural energy identity, a space–time weak formulation for 1D integral problems is briefly introduced, and continuity and coerciveness properties of the related bilinear form are proved. Then, a theoretical analysis of an extension of the introduced formulation for 2D problems is proposed, pointing out the novelty with respect to existing literature results. At last, various numerical simulations will be presented and discussed, showing unconditional stability of the space–time Galerkin boundary element method applied to the energetic weak problem. Copyright © 2009 John Wiley & Sons, Ltd.
Approximate imposition of boundary conditions in immersed boundary methods
Authors: Codina Ramon , Baiges Joan
Published: June 2009

We analyze several possibilities to prescribe boundary conditions in the context of immersed boundary methods. As basic approximation technique we consider the finite element method with a mesh that does not match the boundary of the computational domain, and therefore Dirichlet boundary conditions need to be prescribed in an approximate way. As starting variational approach we consider Nitsche's methods, and we then move to two options that yield non‐symmetric problems but that turned out to be robust and efficient. The essential idea is to use the degrees of freedom of certain nodes of the finite element mesh to minimize the difference between the exact and the approximated boundary condition. Copyright © 2009 John Wiley & Sons, Ltd.
A Simple Method for Identification of the Parameters of the Fractional Kelvin‐Voight Model
Authors: Lewandowski Roman , Chorazyczewski Bartosz
Published: June 2009

A major difficulty connected with fractional rheological models is the estimation of the model parameters of experimental data. A new method for identification of the parameters of the fractional Kelvin‐Voight model is presented. The procedure has been validated using artificial data and then used in estimating parameters from experimental data. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Synthesis and characterization of polyaniline/silicon dioxide composites and preparation of conductive films
Authors: Zengin Huseyin , Erkan Belgin
Published: June 2009

The focus of this study was to synthesize the inherently conductive polymer polyaniline using an optimized process to prepare polyaniline/silicon dioxide (PANI/SiO2) composites by in situ polymerization and ex situ solution mixing. PANI and PANI/SiO2 composite films were prepared by drop‐by‐drop and spin coating methods. The electrical conductivities of HCl doped PANI film and PANI/SiO2 composite films were measured according to the standard four‐point‐probe technique. The composite films exhibited an increase in electrical conductivity over neat PANI. PANI and PANI/SiO2 composites were also investigated by spectroscopic methods including UV‐Vis, FT‐IR, and Photoluminescence. UV‐Vis and FT‐IR studies showed that SiO2 particles affect the quinoid units along the polymer backbone and indicate strong interactions between the SiO2 particles and the quinoidal sites of PANI (doping effect). The photoluminescence properties of PANI and PANI/SiO2 composites were studied and the PANI/SiO2 composites showed increased intensity as compared to neat PANI. The increase of conductivity of PANI/SiO2 composite may be partially due to the doping or impurity effect of SiO2 where the silicon dioxides compete with chloride ions. The morphology of particles and films were examined by a scanning electron microscope (SEM). SEM measurements indicated that the SiO2 were well dispersed and isolated in composite films. Copyright © 2009 John Wiley & Sons, Ltd.
Structural understanding of stabilization patterns in engineered bispecific Ig‐like antibody molecules
Authors: Jordan Jacob L. , Arndt Joseph W. , Hanf Karl , Li Guohui , Hall Janine , Demarest Stephen , Huang Flora , Wu Xiufeng , Miller Brian , Glaser Scott , Fernandez Erik J. , Wang Deping , Lugovskoy Alexey
Published: June 2009

Bispecific immunoglobulin‐like antibodies capable of engaging multiple antigens represent a promising new class of therapeutic agents. Engineering of these molecules requires optimization of the molecular properties of one of the domain components. Here, we present a detailed crystallographic and computational characterization of the stabilization patterns in the lymphotoxin‐beta receptor (LTβR) binding Fv domain of an anti‐LTβR/anti‐TNF‐related apoptosis inducing ligand receptor‐2 (TRAIL‐R2) bispecific immunoglobulin‐like antibody. We further describe a new hierarchical structure‐guided approach toward engineering of antibody‐like molecules to enhance their thermal and chemical stability. Proteins 2009. © 2009 Wiley‐Liss, Inc.
Ligand unbinding from the estrogen receptor: A computational study of pathways and ligand specificity
Authors: Burendahl Sofia , Danciulescu Cristian , Nilsson Lennart
Published: June 2009

The estrogen receptor (ER) belongs to the nuclear receptor superfamily, whose members regulate important cellular events like development and metabolism. The ER functions as a transcription regulator and can be activated on ligand binding. Consequently, ligand binding and unbinding constitute fundamental processes in the regulation of genes. Even though both biochemical and structural data of ER are available, the actual mechanism of the ligand binding/unbinding remains elusive. We have performed computational studies on the unbinding mechanism of ERα and ERβ, in the presence of cofactors and with ligands ranging from agonist to a full antagonist. Our results show that agonists or selective ER modulators can dissociate from the receptor through multiple pathways with minor effect on the receptor structure, whereas an antagonist requires larger conformational changes. Furthermore, a specific receptor/ligand combination can exhibit a pathway preference depending on character and conformation of both parts. Hence, it is possible that the binding/unbinding mechanism can explain ligand subtype specificity and thus have an impact in drug discovery. Proteins 2009. © 2009 Wiley‐Liss, Inc.
Modularity of intrinsic disorder in the human proteome
Authors: Pentony Melissa M. , Jones David T.
Published: June 2009

Predicting regions of disorder has become of increasing interest when determining protein structure and function. With ∼33% of eukaryotic proteins having significant disordered regions, and an increasing occurrence of disorder in higher organisms, an analysis of the importance of disorder from an evolutionary perspective was clearly warranted. Focusing on the human proteome, we have studied how abundant disorder is and its relevance to protein function and structure. We have shown that disordered regions frequently appear to be independent functional units, and judged by complete association to certain protein domains, may be evolutionarily conserved. Our work also supports previous analyses on association between disorder and alternate splicing and provides support for the modularity of disorder by showing that with respect to splicing events, disordered regions frequently appear to be spliced as whole units. Proteins 2010. © 2009 Wiley‐Liss, Inc.
Induction of the tetracycline repressor: Characterization by molecular‐dynamics simulations
Authors: Haberl Florian , Lanig Harald , Clark Timothy
Published: June 2009

Extensive molecular‐dynamics simulations show that the distance between the centers of gravity of the two equivalent helices 3 in the DNA‐binding heads of the dimer of the tetracycline‐repressor protein (TetR) can be used as a reliable diagnostic of induction. This is not, however, true for X‐ray structures, but only for molecular‐dynamics simulations. This is suggested to be because TetR is inherently flexible along the coordinate of the allosteric change (as is always likely to be the case for allosteric proteins), so that crystal‐packing forces can determine the conformation of the protein. However, the time scale of the allosteric rearrangement in the absence of DNA‐complexationis found to be of the order of tens of nanoseconds, so that rearrangements can be observed reproducibly in 100 ns simulations. Metastable (pre‐equilibrium) conformations of TetR have been observed for up to 60 ns. The likely equilibrium processes and key features of the TetR system are discussed. Proteins 2009. © 2009 Wiley‐Liss, Inc.
Muscle FBPase is targeted to nucleus by its 203KKKGK207 sequence
Authors: Gizak Agnieszka , Maciaszczyk‐Dziubinska Ewa , Jurowicz Magdalena , Rakus Dariusz
Published: June 2009

It has been recently found that muscle fructose 1,6‐bisphosphatase (FBPase) is actively transported into cells' nuclei. Results of an analysis in silico of muscle FBPase structure gave rise to a hypothesis that sequence 203KKKGK207 is responsible for nuclear targeting of the enzyme. To test this, HL‐1 cardiomyocytes were transfected with FITC‐labeled muscle FBPase constructs, bearing mutations within the putative nuclear localization signal (NLS). Results revealed that integrity of the 203KKKGK207 motif is critical to nuclear targeting of muscle FBPase and even a single amino‐acid change within this sequence results in significant decrease of nuclear accumulation of the enzyme. Although it has long been recognized as a canonical NLS in theoretical and computational research, to the best of our knowledge this is the first experimental evidence confirming that the KKKGK motif can act as a functional NLS in a protein. Proteins 2009. © 2009 Wiley‐Liss, Inc.
GPCR 3D homology models for ligand screening: Lessons learned from blind predictions of adenosine A2a receptor complex
Authors: Katritch Vsevolod , Rueda Manuel , Lam Polo Chun‐Hung , Yeager Mark , Abagyan Ruben
Published: June 2009

Proteins of the G‐protein coupled receptor (GPCR) family present numerous attractive targets for rational drug design, but also a formidable challenge for identification and conformational modeling of their 3D structure. A recently performed assessment of blind predictions of adenosine A2a receptor (AA2AR) structure in complex with ZM241385 (ZMA) antagonist provided a first example of unbiased evaluation of the current modeling algorithms on a GPCR target with ∼ 30% sequence identity to the closest structural template. Several of the 29 groups participating in this assessment exercise (Michino et al., doi: 10.1038/nrd2877) successfully predicted the overall position of the ligand ZMA in the AA2AR ligand binding pocket, however models from only three groups captured more than 40% the ligand‐receptor contacts. Here we describe two of these top performing approaches, in which all‐atom models of the AA2AR were generated by homology modeling followed by ligand guided backbone ensemble receptor optimization (LiBERO). The resulting AA2AR‐ZMA models, along with the best models from other groups are assessed here for their vitual ligand screening (VLS) performance on a large set of GPCR ligands. We show that ligand guided optimization was critical for improvement of both ligand‐receptor contacts and VLS performance as compared to the initial raw homology models. The best blindly predicted models performed on par with the crystal structure of AA2AR in selecting known antagonists from decoys, as well as from antagonists for other adenosine subtypes and AA2AR agonists. These results suggest that despite certain inaccuracies, the optimized homology models can be useful in the drug discovery process. Proteins 2010. © 2009 Wiley‐Liss, Inc.
Applying Undertaker to quality assessment
Authors: Archie John G. , Paluszewski Martin , Karplus Kevin
Published: June 2009

Our group tested three quality assessment functions in CASP8: a function which used only distance constraints derived from alignments (SAM‐T08‐MQAO), a function which added other single‐model terms to the distance constraints (SAM‐T08‐MQAU), and a function which used both single‐model and consensus terms (SAM‐T08‐MQAC). We analyzed the functions both for ranking models for a single target and for producing an accurate estimate of GDT_TS. Our functions were optimized for the ranking problem, so are perhaps more appropriate for metaserver applications than for providing trustworthiness estimates for single models. On the CASP8 test, the functions with more terms performed better. The MQAC consensus method was substantially better than either single‐model function, and the MQAU function was substantially better than the MQAO function that used only constraints from alignments. Proteins 2009. © 2009 Wiley‐Liss, Inc.