bluuebunny/crossref_metadata_2025 huggingface dataset:
Using residue sums to estimate high‐order Fourier harmonics of piecewise‐continuous transcendental functions: Application to Class A‐, B‐ and F‐type amplifier circuits
Authors: Kenny R. G.
Published: September 2007

A discrete fast‐Fourier transform (DFFT) is the preferred method of choice for the rapid evaluation of a set of harmonics of a piecewise‐continuous and periodic transcendental form. For large sets of Fourier components specified to some stringent error criterion, the approach becomes increasingly unattractive owing to the presence of round‐off errors that result from the switching of one transcendental form to another. As an alternative, it might be wondered whether the high‐frequency components can be more efficiently estimated by employing a combination of residue sums and boundary integrals in the complex plane z = Reiωt, where ω is the fundamental frequency and R = ∣z∣.

The starting point is the construction of suitable contours that divide the complex plane into a number of sectors in accordance with the number of intervals of smooth behaviour of a periodic piecewise‐continuous real function along ∣z∣ = 1. Each sector encompasses the analytic extension of a real transcendental function on ∣z∣ = 1 to yield p(z)T(f(z)), where T(ζ) is meromorphic and p(z), f(z) are Laurent series. Fourier coefficients are subsequently expressed in terms of residue series and constant‐phase boundary integrals from each of the various sectors associated with a given p(z)T(f(z)). This approach is applied to the model for the drain current of a field effect transistor (FET), where in this case T(ζ) = tanh(ζ), which is subject to the modes of operation: ‘Class A’, ‘Class B’ and approximate ‘Class F’. In contrast to Classes A and B, the Fourier coefficients in the ‘Class F’ drain current decay slowly with frequency, suggesting that this mode might be more suitably analysed using a combined DFFT/residue procedure. Copyright © 2007 John Wiley & Sons, Ltd.
Antioxidant capacity of leafy vegetables as affected by high tunnel environment, fertilisation and growth stage
Authors: Zhao Xin , Iwamoto Takeo , Carey Edward E
Published: September 2007

BACKGROUND: This study was conducted to evaluate the influences of protected environment, organic fertilisation and growth stage on the oxygen radical absorbance capacity (ORAC) values of leafy vegetables.

RESULTS: In a first experiment, pac choi grown in high tunnels had significantly lower ORAC than field‐grown plants. Organic fertiliser markedly increased the antioxidant capacity of pac choi compared with conventional treatment, especially in the open field. However, both open field and organic production resulted in significantly lower yield and more severe leaf damage due to insect attack. In a second study, spinach showed the highest ORAC, followed by pac choi, red leaf lettuce and romaine lettuce. A significant decline in ORAC under high tunnel production was observed only in spinach. In contrast to the first trial, organic fertilisation did not cause an increase in antioxidant capacity of the leafy vegetables. The ORAC values of spinach from the open field and pac choi from high tunnels were significantly higher when harvested at the mature head stage than at the baby size stage.

CONCLUSION: Further studies will help to elucidate effects of genotype, growth stage, and production environment on antioxidant capacities of vegetables and may lead to recommended practices to maximise antioxidant capacity of vegetable crops. Copyright © 2007 Society of Chemical Industry
Content composition and antioxidant activity of isoflavones in commercial and homemade soymilk and tofu
Authors: Ishihara Michiko , Singh Harmit , Chung Glen , Tam Chick
Published: September 2007

BACKGROUND: Isoflavones, found in soymilk and tofu, are one of the phytochemicals in soy‐based products that may promote good health. Homemade tofu and various homemade soymilk samples were made using different soaking, grinding, and cooking methods. The homemade samples were compared to commercial tofu and soymilk for total isoflavone content and composition as well as their antioxidant capacity. All samples were freeze‐dried and extracted with a 58% acetonitrile solution which was subsequently used to determine the isoflavone content by reverse‐phase high‐performance liquid chromatography. The antioxidant activity of extracts was determined using a modified 2,2‐azino‐bis‐(3‐ethylbenzthiazoline‐6‐sulfonic acid) method and total antioxidant capacity was reported as ascorbic acid equivalents.

RESULTS: The total isoflavone, aglycone, and antioxidant levels were significantly higher in homemade soymilk and tofu (1571 µg) than in commercial samples. Homemade soymilk made by the extended boiling method yielded the highest total isoflavone (2567 µg) and glucoside (1525 µg) content. A strong positive correlation was observed between the total isoflavone, aglycone conjugates, and genistein series concentration and antioxidant capacity of soymilk.

CONCLUSION: Increased moist heating time yielded the highest concentration of total isoflavones as well as aglycone conjugates and the genistein series. Increasing the duration of boiling can increase the isoflavone content of both homemade and commercial soymilk and tofu. Copyright © 2007 Society of Chemical Industry
Gelatine–starch films: Physicochemical properties and their application in extending the post‐harvest shelf life of avocado (Persea americana)
Authors: Aguilar‐Méndez Miguel A , Martín‐Martínez Eduardo San , Tomás Sergio A , Cruz‐Orea Alfredo , Jaime‐Fonseca Mónica R
Published: September 2007

BACKGROUND: Several storage techniques have been developed to extend the post‐harvest shelf life of horticultural products. One method involves the use of edible or biodegradable coatings. Such coatings are made of biological materials that are used to coat fresh products, providing a semi‐permeable barrier to water vapour and gases, e.g. O2 and CO2. The influence of starch concentration, glycerol content and pH on the carbon dioxide permeability (CO2P) and mechanical properties of gelatine–starch edible films were evaluated.

RESULTS: Results showed that increments in the starch concentration and pH resulted in higher CO2P values. Film puncture strength increased when the starch concentration decreased and the maximum resistance value (32.6 N) was obtained at pH 6. Deformation was mainly affected by glycerol and starch content. Some films were chosen in order to evaluate their effect, as coatings, in the post‐harvest shelf life of avocados (Persea americana Mill c.v. Hass). Fruits were immersed in the coating solutions, air dried and stored at two temperatures. Changes in colour, weight loss and pulp firmness were determined in fruits stored at 6 °C. In addition, respiration rate was measured in avocados kept at 20 °C.

CONCLUSION: The application of gelatine–starch coatings delayed the ripening process of avocados, as indicated by a better pulp firmness and retention of skin colour, and lower weight loss of coated fruits in comparison with control avocados. The coatings also resulted in a delayed respiratory climacteric pattern, by 3 days, for coated fruits. Copyright © 2007 Society of Chemical Industry
Synergism between lipoxygenase‐active soybean flour and ascorbic acid on rheological and sensory properties of wheat bread
Authors: Junqueira Roberto M , Cocato Maria L , Colli Célia , Castro Inar A
Published: September 2007

BACKGROUND:The interaction between lipoxygenase‐active soybean flour (LOX) and ascorbic acid (AA), on colour, rheological and sensory properties of wheat bread was studied with the aim of reducing the applied quantity of additives in bread formulations.

RESULTS:The ascorbic acid (0–500 ppm) and active soybean flour (0–1%) mixture improved bread‐crumb colour by lowering the yellow hue in a higher proportion than those expressed by the components alone, characterising a synergistic mechanism (ŷb= 15.1− (1.7 × LOX) − (0.5 × AA) − (5.8 × LOX × AA), whereŷbrepresent the estimated value for the yellow hue parameter). No differences in flavour and porosity were seen between the samples. As supported by the instrumental methods, breads made with active soybean flour and ascorbic acid (LOX + AA) had whiter crumbs and were softer and springier than controls as assessed by a trained sensory panel. In summary, the combination of both active soybean flour and ascorbic acid showed synergism, promoting a greater bleaching effect than when used alone.

CONCLUSION:These results suggest the potential use of active soybean flour as a synergistic ingredient in the substitution of artificial additives in bread making. Since the interaction on the bleaching response was not linear and active soybean flour showed a higher iron concentration (66.40 ± 4.23 µg g−1) than non‐active soybean flour (52.30 ± 0.40 µg g−1), more studies are warranted to establish the biochemical mechanisms involved in this interaction. Copyright © 2007 Society of Chemical Industry
Weak-guidance-theory review of dispersion and birefringence management by laser inscription
Authors: Zheltikov A M , Reid D T
Published: September 2007

A brief review of laser inscription of micro- and nanophotonic structures in transparent materials is provided in terms of a compact and convenient formalism based on the theory of weak optical waveguides. We derive physically instructive approximate expressions allowing propagation constants of laser-inscribed micro- and nanowaveguides to be calculated as functions of the transverse waveguide size, refractive index step, and dielectric properties of the host material. Based on this analysis, we demonstrate that dispersion engineering capabilities of laser micromachining techniques are limited by the smallness of the refractive index step typical of laser-inscribed structures. However, a laser inscription of waveguides in pre-formed micro- and nanostructures suggests a variety of interesting options for a fine dispersion and birefringence tuning of small-size waveguides and photonic wires.
Proteasome inhibitors: Poisons and remedies
Authors: Meiners Silke , Ludwig Antje , Stangl Verena , Stangl Karl
Published: September 2007

The proteasome inhibitor bortezomib has been approved as a cytostatic drug for the therapy of multiple myeloma, and is currently being tested in clinical trials for a variety of other malignancies. At the same time, a growing number of animal studies suggest that proteasome inhibitors may also prove to be valuable remedies for the treatment of non‐tumorous diseases. In this review, we will revisit the current applications of proteasome inhibitors in clinical research according to the cellular effects of proteasome inhibitors as poisons, which induce apoptosis, or as remedies, which modulate cellular function and protect from cell death. We postulate that the correct distinction of a poison from a remedy depends on cell type and on the degree of proteasome inhibition. Dose‐dependent and differential inhibition of the proteasome may affect specific sets of substrates, thereby conferring substrate specificity. According to this idea, we suggest that inhibition of the proteasome to a defined degree may offer a promising tool in achieving desired therapeutic effects in various diseases. © 2007 Wiley Periodicals, Inc. Med Res Rev, 28, No. 2, 309–327, 2008
Molecular network of cartilage homeostasis and osteoarthritis
Authors: Hashimoto Megumi , Nakasa Tomoyuki , Hikata Tomohiro , Asahara Hiroshi
Published: September 2007

This review article presents the current understanding of the molecular basis of articular cartilaginous homeostasis, and outlines potential areas to focus on within the developing field of therapeutics for cartilage disorders. Articular cartilage, an integral component of joints in extremities and the vertebral column, is essential for locomotion. Disturbance of joint development or cartilage homeostasis causes congenital osteocartilaginous dysplasia or osteoarthritic diseases, respectively. Symptomatic treatments and surgical replacement of joints are effective but can also be problematic in terms of quality of life over time. Recently, new insights into the molecular biological basis of chondrocyte differentiation and cartilage homeostasis have been reported. While joint formation is regulated by several growth factors such as Wnts (wingless‐related MMTV integration site) and Gdfs (growth and differentiation factors), the pathology of osteoarthritis is now interpreted as the disruption of balance between anabolic and catabolic signals. Current findings in molecular biology on joint development are reviewed concisely to aid in the understanding of the molecular network that governs articular cartilage development and homeostasis. © 2007 Wiley Periodicals, Inc. Med Res Rev, 28, No. 3, 464–481, 2008
Olive oil and oxidative stress
Authors: Fitó Montserrat , de la Torre Rafael , Covas María‐Isabel
Published: September 2007

Oxidative stress is defined as an imbalance between the oxidant and antioxidant systems of the body, in favor of the oxidants. Oxidative stress produced by free radicals has been linked to the development of several diseases such as cardiovascular, cancer, and neurodegenerative diseases Olive oil is the main source of fat of the Mediterranean diet which has been shown to be effective against oxidative stress associated diseases and also with ageing. Besides its richness in monounsaturated fatty acids, the oleic acid, olive oil contains minor components with antioxidant properties. In this review, we summarize the state of the art, and degree of evidence, of the body of knowledge concerning the protective role of the major and minor components of olive oil on oxidative stress.
Nutrition in the genomics era: Cardiovascular disease risk and the Mediterranean diet
Authors: Ordovas Jose M. , Kaput Jim , Corella Dolores
Published: September 2007

The effect of dietary changes on phenotypes (i.e., plasma lipid measures, body weight and blood pressure) differs significantly between individuals. This phenomenon has been more extensively researched in relation to changes in dietary fat and plasma lipid concentrations for the prevention of cardiovascular disease (CVD) compared to other pathological conditions. Although common knowledge associates low fat diets with reductions in total and plasma LDL cholesterol, the clinical evidence shows dramatic inter‐individual differences in response that are partially due to genetic factors. The discovery of the cardioprotective and other healthy properties of the Mediterranean diet has popularized the consumption of Mediterranean products such as olive oil. Molecular, clinical, and epidemiological studies have begun to shed some light about how various components of this diet may protect the cardiovascular system and to decrease the risk of other diseases such as cancer. However, it is also possible that the right combination of genetic, cultural, socioeconomic factors is needed to achieve full benefit. It has been proposed that the Mediterranean diet may be closer to the ancestral foods that were part of human development and our metabolism may have evolved to work optimally on such a diet rather than with the current diets richer in saturated fat and highly refined and processed foods. Therefore, it is possible that alleles that are associated with increase disease risk may be silenced in the presence of that more ancestral and traditional diet and lifestyle. This knowledge may provide the basis for successful public health as well individual approaches for disease prevention.
Time‐dependent characterization of an optically modulated CPW line characterized with a large signal network analyzer
Authors: Poesen G. , Stiens J. , Vounckx R. , Poesen G. , Vanden Bossche M.
Published: September 2007

Time‐dependent behavior of a CPW line under optical modulation is characterized using a large‐signal vector network analyzer. The influence of the optical modulation frequency on the propagation of high carrier frequencies along a CPW is discussed in this article. Different operation conditions in time are defined for a CPW line under illumination. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 3124–3128, 2007; Published online in Wiley Inter‐Science (www.interscience.wiley.com). DOI 10.1002/mop.22888
Wideband circularly‐polarized serial rotated 2 × 2 circular patch antenna array
Authors: Bian Lei , Shi X. Q.
Published: September 2007

In this article, a novel wideband cularly‐polarized serial rotated 2 × 2 circular patch antenna array is presented. The patches are excited sequentially by a broadband feed network. It is found that the antenna array can deliver a measured impedance bandwidth of 46.6% for SWR < 2, 3‐dB axial‐ratio measured bandwidths of 40%, and the measured bandwidth of 70.1% for the gain > 3 dBi. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 3122–3124, 2007; Published online in Wiley Inter‐Science (www.interscience.wiley.com). DOI 10.1002/mop.22889
Electromagnetic scattering from cylinder with generalized impedance boundary condition
Authors: Serkan Tezel Necmi
Published: September 2007

In this study, the electromagnetic scattering from cylinder whose surface satisfies most general impedance boundary is presented. The proposed method is based on the series representation of incident and scattering fields. Surface impedance is assumed to be both inhomogeneous and anisotropic. The anisotropic surface impedances are expressed by terms of Fourier series. By applying the boundary condition on the surface of the cylinder, series equation is obtained. This equation is reduced the matrix equation by using the orthogonal properties of the Fourier expansion functions, and unknown cylindrical mode coefficients are calculated. Obtained results are compared with those obtained by numerically Nyström method for inhomogeneous isotropic impedance cylinder and good agreements are observed. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 3090–3093, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22890
Optimization of integrated circuits placement for electric field reduction inside telecommunications equipment using Monte Carlo simulation and parallel recombinative simulated annealing
Authors: Goudos Sotirios K. , Zaharis Zaharias D. , Lazaridis Pavlos I. , Gallion Philippe B.
Published: September 2007

This article presents a novel approach to the modeling and reduction of electromagnetic interference (EMI) caused by radiated emissions of integrated circuits (ICs) inside rectangular metallic enclosures of telecommunications devices. This type of analysis applies for several types of modern telecommunications equipment found in high‐speed networks as well as in mobile communications. A generic model of such a device is created. The ICs are modeled as small electric dipoles and their interaction with the enclosure walls is studied by using the dyadic Green's functions. The electric field on the enclosure walls is computed and its reduction is studied as optimization problem using evolutionary algorithms. Two algorithms are employed: Genetic algorithms (GAs) and parallel recombinative simulated annealing (PRSA). PRSA is a hybrid evolutionary strategy that inherits properties from both GAs and simulated annealing. Monte Carlo simulation is subsequently applied to the optimization results to derive the electric field on the metallic walls and also to perform a worst‐case analysis. The applications of the above approach in early PCB design process are discussed. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 3049–3055, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22893
Slot‐loaded gap‐coupled microstrip array antenna for wide impedance bandwidth
Authors: Konda R. B. , Mulgi S. N. , Satnoor S. K. , Hunagund P. V.
Published: September 2007

A novel design of four‐element gap‐coupled slot rectangular microstrip array antenna fed by aperture coupling is presented for wideband operation. From the experimental results it is seen that a −10 dB return loss impedance bandwidth of 34.17% is achieved at X‐band frequencies. This impedance bandwidth is 2.43 times more than that of conventional corporate fed four‐element gap‐coupled rectangular microstrip array antenna, which operates at triple band of frequencies. The effect of slot in the radiating and parasitic elements and use of aperture coupling is studied for converting its triple bands into a single band. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 3014–3017, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22894
A novel compact CPW bandpass filter with spurious response suppression
Authors: Weng Min‐Hang , Huang Chun‐Yueh , Ye Chang‐Sin , Hung Cheng‐Yuan
Published: September 2007

It is an important issue to suppress the spurious response of the coplanar‐waveguide (CPW) bandpass filter (BPF). In this letter, a novel CPW BPF at 1.57 GHz with spurious responses suppression for application in Global Positioning System is presented. By adjusting the filter structure, the wide stopband rejection greater than 20 dB from 1.8 to 4.5 GHz could be obtained away from the designed central frequency without increasing the circuit dimension. The designed CPW‐BPF is investigated numerically and experimentally. Measured results show a good agreement with the simulated analysis. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2941–2944, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22898
Compact wideband inverted planar monopole antenna
Authors: Baik J. W. , Sung Y. J. , Kim Y.‐S.
Published: September 2007

In this article, an inverted planar monopole antenna with two shorting plates is proposed. This inverted planar monopole antenna provides a 3.55:1 impedance bandwidth (for VSWR < 2). Owing to its compact size and wide impedance bandwidth, this antenna is suitable for CDMA, GSM, DCS, PCS, and wireless LAN (IEEE 802.11b) applications. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2913–2914, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22900
Metamaterial filters with attenuation poles in the pass band for ultra wide band applications
Authors: Gil Marta , Bonache Jordi , Martín Ferran
Published: September 2007

In this work, a composite right/left handed (CRLH) transmission line implemented by means of complementary split rings resonators (CSRRS) and interdigital capacitors is designed to provide a transmission band useful for ultra wide band (UWB) applications, i.e., in the interval 3.1–10.6 GHz. This huge bandwidth is obtained by balancing the line, namely by merging the left handed (LH) and right handed (RH) bands typical of these structures. The result is a single and broad transmission band, which exhibits a sharp cut‐off at the lower edge due to the presence of a transmission zero. In these UWB band pass filters, an attenuation pole within the band may be of interest for the elimination of possible interfering signals. It is demonstrated that such attenuation poles can be introduced by adding properly designed spiral resonators (SRs) at both sides of the host line on the top layer of the design. The fabricated device is small (area A = 0.66 cm2) and exhibits reasonable performance. This work contributes to demonstrate the potentiality of transmission line metamaterials for the design of microwave components in planar technology. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2909–2913, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22901
Modeling of dielectric charging in RF MEMS capacitive switches
Authors: Sumant Prasad S. , Cangellaris Andreas C. , Aluru Narayana R.
Published: September 2007

A unified, macroscopic, one‐dimensional model is presented for the quantitative description of the process of dielectric charging in RF MEMS capacitive switches. The model provides for the direct incorporation of various physical factors known to impact dielectric charging, such as surface roughness, material inhomogeneity, and electric field‐dependent conduction in the dielectric. The values of the various parameters used in the model are extracted from experimental data. The proposed model serves as a generalization of various earlier models reported in the literature for the quantitative description of dielectric charging. Its formulation is such that it can be incorporated in a straightforward manner in coupled electro‐mechanical modeling schemes for the computer‐aided analysis of RF MEMS capacitive switches. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 3188–3192, 2007; Published online in Wiley InterScience (www.interscience.wiley.com).DOI 10.1002/mop.22903
Diversity gain measurements of a reconfigurable antenna with switchable polarization
Authors: Poussot B. , Laheurte J. M. , Cirio L. , Picon O.
Published: September 2007

This article presents an experimental investigation on the diversity performance of a reconfigurable antenna integrating a SPDT for polarization switching. The antenna is characterized in terms of its envelope correlation factor, mean effective gain, and diversity gain (DG) in a multipath indoor environment. The influence of the antenna placement and orientation is emphasized. Low correlation factors and large DGs are observed making this device highly performing for indoor wireless communication systems. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 3154–3158, 2007; Published online in Wiley Inter‐Science (www.interscience.wiley.com). DOI 10.1002/mop.22904
A steerable array antenna using controllable 4‐bit dielectric slab phase shifters on a coplanar waveguide at 24 GHz
Authors: Cha Junho , Kuga Yasuo
Published: September 2007

A steerable antenna using a movable dielectric phase shifter is designed and developed. The change of the effective dielectric constant at different dielectric slab positions on a CPW is used as the phase shifter. The impedance matching and desired phase shift conditions are satisfied at two slab heights. Additionally, the reflection is designed to be minimized at these slab positions and at the designed frequency. A low‐loss dielectric material is used as the dielectric slab and is placed close to a coplanar transmission line with an airgap. A tapered 8 × 7 steerable array antenna with phase shifters is designed and fabricated at 24 GHz. The E‐ and H‐plane radiation patterns are measured at different phase shift positions and compared with the expected results. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 3118–3122, 2007; Published online in Wiley Inter‐Science (www.interscience.wiley.com). DOI 10.1002/mop.22906
Balanced BPSK modulator for Ka‐band communication systems
Authors: Mittal Ashok , De Asok
Published: September 2007

This article details the design of balanced PSK modulator using integrated finline coplanar line hybrid junction. The PSK signal output is in suspended stripline with incident wave carrier in unilateral symmetric finline. Schottky barrier diodes MA4E2037 from M/ACom has been used for modulation. The balanced configuration offers high isolation between the carrier input port and the modulated carrier output port and thus the pulse width variations and amplitude deviations are suppressed. An insertion loss imbalance of ±1.5 dB with an average loss of 2.5 dB in the two switching states has been achieved over 37.0 to 38.0 GHz against the estimated loss of 2.0 dB. The phase imbalance is ±10° with phase switching from 165° to 185°. As the PSK output signal is in suspended stripline, two BPSK Modulators can easily be combined together to work as QPSK modulator for point to point millimeter wave radio links. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 3046–3049, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22910
Suppression of higher order modes in vertically coupled micro‐ring resonators
Authors: Alexandropoulos Dimitris , Kapsalis Alexandros , Syvridis Dimitris
Published: September 2007

we propose a new scheme for monomode operation of micro‐ring resonators utilizing vertical coupling. The scheme succeeds in suppressing higher order spatial modes by selectively exciting the fundamental mode of the ring. This is achieved by properly varying the material and waveguide properties facilitated by the vertical geometry of the structure. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2963–2968, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22915
The design of broadband circularly polarized planar microstrip antenna array
Authors: Jjian‐Gang Liang , Xiang‐Jun Gao , Hai‐Zhou Zhao
Published: September 2007

Based on the conventional microstrip antenna, a broadband circularly polarized microstrip antenna fed by electromagnetism coupling is designed, which is composed of three substrates. The frequency band is broadened not only, but also the circular polarization axial ratio is effectively improved. Then four such cells are constructed to a circularly polarized array. Through calculating and testing, the 14.4% and 39.65% (VSWR < 2) bandwidth and 8.34% and 21.4% 3‐dB axial ratio bandwidth are achieved, respectively. Such circularly polarized array can be used extensively in communications field. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2936–2939, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22916
Characterization of on‐chip miniature multi‐layer spiral inductors for RFICs
Authors: Xie Jian‐Yong , Yin Wen‐Yan , Shi Jinglin , Kang Kai , Chen Zhizhang (David)
Published: September 2007

Several existing closed‐form equations for calculating DC inductance and resistance of single‐spiral inductors are examined at first, and the most accurate formula is chosen for characterizing the DC inductance of multi‐layer spiral inductors. The partial element equivalent circuit (PEEC) method is implemented for computing their frequency‐dependent (AC) resistance and inductance. To validate our calculated results, we designed and fabricated some multi‐layer spiral inductors using standard 0.18 μmCMOS technology. The on‐chip measurements are carried out so as to obtain two‐portS‐parameters of these inductors. Excellent agreements are obtained between the calculated and experimental results, which include DC and low‐frequency inductances of three‐, four‐, and fiver‐layer spiral inductors, respectively. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2932–2936, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22917
Design of frequency selective surface superstrates for scanning microstrip patch array antenna
Authors: Hyun Lee Dong , Mittra Raj , Sang Park Wee
Published: September 2007

We investigate the directivity, sidelobe level (SLL) and maximum radiation angle characteristics of a frequency selective surface (FSS) superstrate placed above a 5 × 1 patch array antenna for different scan angles. We find that the frequency at which a high directivity is achieved moves higher as the scan angle of the array is increased, and that the size of the original FSS superstrate needs to be increased along the direction of the scan angle, in comparison to that of the broadside case (0°), to effectively enhance the directivity and suppress the SLL. A rectangular FSS superstrate with enlarged dimension in the scan direction is proposed, and the radiation patterns of the original and elongated FSS composites are compared. For a 20° scan angle of the array antenna, the directivity and the SLL of the changed FSS composite are enhanced by 1.3 and 3.9 dB, respectively, relative to those of the original FSS composite. We compare and summarize the results for the directivity and SLL characteristics of four different antenna prototypes, namely a single antenna; a conventional 5 × 1 array antenna; the FSS antenna composite with a single patch antenna; and an FSS array composite comprising of a 5 × 1 array antenna designed for a scan angle of 0°. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 3184–3187, 2007; Published online in Wiley InterScience (www.interscience.wiley.com).DOI 10.1002/mop.22919
Fully embedded LC diplexer passive circuit into an organic package substrate
Authors: Lee Hwan Hee , Park Jae Yeong
Published: September 2007

In this article, fully embedded and miniaturized diplexer passive circuit device has been developed and characterized for dual‐band/mode CDMA handset applications. The size of the embedded diplexer is significantly reduced by embedding high Q circular spiral inductors and high DK MIM capacitors into a low cost organic package substrate. The embedded inductor and capacitor have quality factors of 61 and 32 at 1 GHz. The fabricated diplexer has insertion losses and isolations of −0.5 and −23 dB at 824–894 MHz and −0.7 and −22 dB at 1850–1990 MHz, respectively. Its size is 3.9 mm × 3.9 mm × 0.77 mm (height). The fabricated diplexer is the smallest one which is fully embedded into a low cost organic package substrate. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2960–2963, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22921
Analysis of inductive frequency selective surfaces by the method of moments with entire‐domain basis functions
Authors: Don Nataliya , Bozzi Maurizio , Kirilenko Anatoly , Perregrini Luca
Published: September 2007

This study presents an efficient method for the analysis of thick metal screens perforated periodically with apertures (inductive frequency selective surfaces). The analysis is based on the Method of Moments with entire‐domain basis functions. The peculiarity of the proposed approach is the particular calculation of the basis functions in the case of arbitrarily shaped apertures. The method is validated through the comparison with published data and is applied to the design of a new dual‐band filter. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2929–2932, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22923
A microstrip antenna using patch array resonator
Authors: Kim D. , Kim M. , Tanaka M. , Matsugatani K.
Published: September 2007

A new planar antenna using two‐dimensional patch array resonator for an improved‐bandwidth performance is presented. The antenna, designed to work at 6.8 GHz on a 1.27‐mm‐thick substrate with a dielectric constant of 9.8, has a total size of 314 mm2. The measurements showed a 6‐dB frequency bandwidth of 12.9%, which is a significant improvement over the 3.3% bandwidth measured from a 40 mm2 single‐patch reference antenna. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2926–2928, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22924
A wideband 8‐element omnidirectional array for wireless system
Authors: Wu Dakui , Zhao Minghua , Fan Yong , Zhang Yonghong
Published: September 2007

A smart broad‐band planar antenna for wireless system is presented. The simple modeling of this antenna and design method based on equivalent circuits has been developed. An eight‐element planar array has been designed, fabricated and measured. Measured results exhibit good performance of the return loss and horizontal plane radiation pattern. The measured 10‐dB return loss bandwidth of the broad‐band planar array is demonstrated to be 62.5% and the un‐roundness of its horizontal plane pattern is less than 4.5 dB. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2944–2946, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22925
Optimal design of ultra wideband antennas using a mixed model of 2‐D genetic algorithm and finite‐difference time‐domain
Authors: Ding Min , Jin Ronghong , Geng Junping
Published: September 2007

A mixed model of two‐dimensional (2‐D) genetic algorithm and finite‐difference time‐domain is applied to the automatic design of ultra wideband (UWB) planar antennas in a finite size. The results illustrate that the method is valid and a new UWB antenna is designed successfully in the small size. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 3177–3180, 2007; Published online in Wiley InterScience (www.interscience.wiley.com).DOI 10.1002/mop.22928
Printed compact S‐shaped monopole antenna with a perpendicular feed for penta‐band mobile phone application
Authors: Wu Chih‐Hsien , Wong Kin‐Lu
Published: September 2007

A printed compact S‐shaped monopole antenna for penta‐band mobile phone application is presented. The S‐shaped monopole antenna has a uniplanar structure and can be printed on an FR4 substrate of small size 10 × 45 mm2 to achieve a compact configuration. By mounting the antenna above the top edge of the system ground plane of the mobile phone and feeding it using a perpendicular feed, the antenna occupies a small volume in the top portion of the mobile phone. This makes it especially suited for application in the thin mobile phone in which the embedded internal antenna is required to be small in occupied volume and narrow in width. In addition, the antenna can generate two wide operating bands at about 900 and 2000 MHz to cover the GSM850/900 and DCS/PCS/UMTS operation, respectively. Details of the proposed antenna are presented. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 3172–3177, 2007; Published online in Wiley InterScience (www.interscience.wiley.com).DOI 10.1002/mop.22929
Design of dual‐band bandpass filter using stepped impedance resonator and defected ground structure
Authors: Chen Wu‐Nan , Chia Wei‐Kuo , Yang Cheng‐Fu , Shih Chih‐Liang
Published: September 2007

This article presents a novel microstrip dual‐band bandpass filter (BPF) comprising a symmetrically‐bent, open‐loop, square‐ring stepped impedance resonator (SIR) on the upper surface and a symmetrical U‐shaped defected ground structure (DGS) on the lower metallic ground plane. A center frequency of 2.45 GHz is obtained for the first passband of the BPF by adjusting the dimensions of the SIR, while a center frequency ranging from 5 to 7 GHz is obtained for the second passband by adjusting the dimensions of the DGS unit. The experimental and simulation results demonstrate that the insertion losses of the BPF are −1.4 dB at 2.45 GHz, −1.3 dB at 5.75 GHz, and −4.1 dB at 5.2 GHz. The characteristics of the proposed BPF with and without the DGS unit are compared, and the dependency of the second resonance frequency on the dimensions of the DGS unit is discussed. Finally, the effectiveness of etching an additional DGS unit beneath the feed lines to suppress the high out‐of‐band harmonic frequencies is also demonstrated. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 3099–3103, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22933
A hybrid approach for modeling stochastic ray propagation in stratified random lattices
Authors: Martini Anna , Franceschetti Massimo , Massa Andrea
Published: September 2007

The present contribution deals with ray propagation in semi‐infinite percolation lattices consisting of a succession of uniform density layers. The problem of analytically evaluating the probability that a single ray penetrates up to a prescribed level before being reflected back into the above empty half‐plane is addressed. A hybrid approach, exploiting the complementarity of two mathematical models in dealing with uniform configurations, is presented and assessed through numerical ray‐tracing‐based experiments to show improvements upon previous predictions techniques. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 3068–3073, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22934
An efficient technique to lower the error due to the truncation of the scanning region in a bipolar facility
Authors: D'Agostino F. , Ferrara F. , Gennarelli C. , Guerriero R. , Riccio G. , Savarese C.
Published: September 2007

An efficient technique is developed in this article to extrapolate the near‐field data falling outside the measurement region in the bipolar scanning. It is based on the nonredundant sampling representations of the electromagnetic field and on the optimal sampling interpolation expansions. The singular value decomposition method is properly employed for estimating the external data. This allows one to reduce in a significant way the truncation error occurring in the near‐field–far‐field transformation with bipolar scanning. Numerical examples assessing the effectiveness of the technique are shown. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 3033–3037, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22936
2D EIT for biomedical imaging: Design, measurement, simulation, and image reconstruction
Authors: Lim Kim Hwa , Shi Guining , McCarter Kyle , George Rhett , Ybarra Gary , Joines William T. , Wartenberg Scott , Liu Qing Huo
Published: September 2007

A 2D electrical impedance tomography (EIT) system has been developed at Duke University as an experimental system to test the forward and inverse algorithms for EIT application. The forward model is based on the 2nd‐order finite element method (FEM), while the image reconstruction is based on the distorted Born iterative method (DBIM). The major contributions of this work are the application of the higher‐order FEM as a forward solver, and the DBIM as an inverse solver to the integrated EIT system. The forward model has been validated with the measured data to within 0.5% accuracy. Excellent images have been reconstructed with these collected EIT data sets. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2989–2998, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22938
V‐band corrugated metal antenna for Giga‐bit wireless applications
Authors: Fusco V. , Romanek D. , Nair B.
Published: September 2007

In this article we describe the design and performance of a waveguide‐fed corrugated surface wave antenna for use in the 57–62 GHz V‐band wireless communication band for HD video hook‐up. The antenna dimensions are calculated using standard closed form leaky‐wave formulae for infinitely wide corrugations. The actual structure which has finite corrugations is simulated using HFSS with good agreement to measurement. The final structure has a mid‐band return loss of −8 dB and the antenna, exhibits ∼4.2‐dB gain at 60° above the horizontal plane. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2953–2956, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22940
A miniaturized millimeter‐wave branch‐line coupler using nonsymmetrical T‐shape structure with quasi‐stepped impedance resonator
Authors: Shiau Miin‐Shyue , Yuan Shih‐Yi , Liao Shry‐Sann , Sun Pou‐Tou , Liu Don‐Gey
Published: September 2007

In this study, a novel ka‐band compact‐size branch‐line coupler was proposed. The coupler was designed and fabricated with WIN Semiconductors 0.15‐μm pseudomorphic high electron‐mobility transistor process. The design method, simulation data, and measurement results of the proposed coupler were also discussed. The coupler occupied less than 45% of the circuit area compared with conventional design at 30 GHz, and did not implement any lumped elements via‐hole grounding, and bonds wire, making it simpler to design, easier to fabricate, and lower cost. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2950–2953, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22941
Patch fed 2D planar Luneburg lens
Authors: Xue L. , Fusco V. F.
Published: September 2007

A simple means using rectangular patch antennas to feed a 2D planar Luneburg lens is presented. The lens together with the patch launching system is modelled using commercial 3D electromagnetic software. The −23 dB return loss, better than −20 dB port to port isolation of the patches, as well as 15 dB antenna gain and 5.3° −3 dB H‐plane (lens plane) beamwidth indicate excellent lens performance potential at 23.3 GHz. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2922–2924, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22942
Electrothermally‐actuated RF‐MEMS suspended parallel switch
Authors: Girbau David , Pradell Lluís , Lázaro Antonio , Nebot Àlvar
Published: September 2007

This article presents an electrothermally‐actuated lateral resistive‐contact RF‐MEMS parallel switch for application to low GHz wireless communication bands. The device is driven by a metal electrothermal actuator, which achieves large displacements and contact forces at much lower temperatures than conventional polysilicon electrothermal actuators. It was manufactured on a standard low‐resistivity substrate and its RF performance was improved by suspending the structures 25 μm from the substrate. Measured (at 1 GHz) insertion loss is −0.11 dB, return loss −41 dB, and isolation −22 dB. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2894–2896, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22943
Design and optimization of microstrip passive circuits by field‐based equivalent circuit model with aggressive space mapping
Authors: Tang Wanchun , Zhou Puke , Chen Xuemei , Chow Y. Leonard
Published: September 2007

The field‐based equivalent circuit model is applied to the design and optimization of microstrip passive circuits with aggressive space mapping (ASM) technique. The field‐based equivalent circuit model is taken as coarse model, whereas the commercial software IE3D is used as the fine model. Three practical passive components, i.e., two low‐pass filters and a power divider are designed by the field‐based equivalent circuit model with ASM. Good convergence performance is achieved for the designs of all examples. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2889–2893, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22944
A real‐time monitoring photopolarimeter based on a multichannel signal process system
Authors: Twu Ruey‐Ching
Published: September 2007

This study developed and evaluated a photopolarimeter based on a polarization interferometer with four photo detectors. By using the proposed multichannel signal process system, the time varying polarization states of an incident light beam, modulated by an electrically driving liquid crystal cell, can be measured instantly and monitored continually. Research findings contribute to the study of dynamic behaviors of the liquid crystal cell. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 3093–3096, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22947
Microstrip leaky‐wave antenna with beam‐patterns switchable capability
Authors: Li Yuanxin , Xue Quan , Yung Edward Kai‐Ning , Long Yunliang
Published: September 2007

A beam‐patterns switchable microstrip leaky‐wave antenna (MLWA) is presented in this letter. A new feeding configuration of MLWA has been shown. MLWA fed with two feeding terminals on different sides radiates out single‐beam radiation patterns. Through controlling SPDT switch, the beam‐patterns change from single‐beam mode to dual‐beam mode. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 3060–3063, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22949
Spectrum conversion phase‐locked loops used for 43 Gbit/s 3R optical receivers
Authors: Wang Xinyue , Wang Ziyu
Published: September 2007

On the basis of a novel spectrum conversion phase‐locked loop, this article presents a method to recover a 10.709‐GHz synchronized clock from an optical signal of 42.84 Gbit/s (NRZ 27–31–1) and demonstrates a 43 Gbit/s 3R optical receiver based on the spectrum conversion PLL. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 3017–3020, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22951