bluuebunny/crossref_metadata_2025_split huggingface dataset:
Planar multilateral disc monopole antenna for UWB application
Authors: Hsu Cheng‐Hsing 
Published: March 2007

AbstractA planar multilateral disc monopole antenna for ultrawideband (UWB) application is proposed and experimentally studied. The proposed antenna has wide impedance bandwidth from 2.85 GHz to more than 15 GHz with better than −10 dB return loss. Moreover, the proposed antenna is simple in structure and easy to fabricate. The design is demonstrated assuming FR4 substrate with a relative dielectric constant of 4.4 and thickness of 1.6 mm. The size of the antenna is 40 mm × 50 mm. Experimental patterns are showing the behavior of omnidirectional beam pattern in H‐plane. Details of the proposed antenna design and simulation results for UWB operations are presented and discussed. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1101–1103, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22353
Fully embedded high Q circular stacked spiral inductors into organic substrate
Authors: Lee Hwan H. , Park Jae Y. 
Published: March 2007

AbstractIn this paper, fully embedded circular‐stacked spiral inductors are investigated into a multilayered PCB substrate for low cost and miniaturized RF system on package (SOP) applications. The embedded circular‐stacked inductors are optimally designed to obtain high quality factor and self‐resonant frequency by using 3D EM simulator. The fabricated two‐turn circular‐stacked inductor has an inductance of 8.4 nH and a maximum quality factor of 67 at 1.2 GHz. The device size of the staked inductor is ∼65% of the planar inductor. The measured performance characteristics are well matched with the 3D EM‐simulated ones. The embedded circular stacked spiral inductors are promising for organic‐based SOP, which needs various functionality, low cost, small size and volume, and high packaging density. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1074–1077, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI.10.1002/mop.22354
Flexible‐substrate low‐cost construction of a coplanar‐waveguide aperture‐coupled microstrip patch antenna
Authors: Depret Dominic , Rogier Hendrik , Dhaenens Kristof , Vanfleteren Jan 
Published: March 2007

AbstractAn innovative and cost‐effective procedure for building multi‐layered planar antennas is presented. The antenna is constructed by defining copper patterns forming the feed plane and the antenna plane on a single flexible polyimide substrate and by folding the flex around a low εr and low‐loss spacer. By a suitable choice of transfer tape to assemble the different layers, a high alignment accuracy and low substrate losses are ensured. To illustrate our new approach, the design and manufacturing of a coplanar‐waveguide aperture‐coupled patch antenna covering the complete 2.45 GHz ISM band is described. By means of reflection and transmission measurements, the high gain and high efficiency of the antenna prototypes are demonstrated. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1071–1074, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI.10.1002/mop.22355
All‐optical diode in photorefractive crystal
Authors: Yuan W. , Wang B. 
Published: March 2007

AbstractIn this letter, we present a technique that employs photorefractive crystals for all‐optical diode. We theoretically designed a structure using two‐pieces of photorefractive crystals, this special crystals set show significantly potentials for applications in unidirectional diffraction beams. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1092–1095, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22360
Analysis of the band‐stop techniques for ultrawideband antenna
Authors: Hong Seokjin , Shin Jaewoong , Park Hoon , Choi Jaehoon 
Published: March 2007

AbstractTwo band‐stop techniques for UWB antenna design are suggested in this article. The proposed antennas have wide bandwidth enough to cover UWB services along with the band‐stop characteristic for 5 GHz WLAN band. By inserting an U‐shaped slot or attaching an inverted Y‐shaped short‐circuited stub, the band‐stop characteristic is obtained. Prototypes of the proposed antennas are implemented and the parametric studies of the two band‐stop techniques are performed. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49:1058–1062, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22363
Integrated electro‐optic Mach–Zehnder modulator fabricated by vapour Zn‐diffusion in LiNbO3
Authors: Suárez I. , Pernas P. L. , Lifante G. 
Published: March 2007

AbstractA novel integrated Mach–Zehnder modulator fabricated on Z‐cut lithium niobate wafers is presented. The optical waveguides were fabricated by the Zn‐diffusion method, which allows monomode TM propagation at the wavelength of interests by choosing the channel waveguide width. The TM‐mode is shown to be buried beneath the surface, which avoids the need of using a dielectric buffer to reduce propagation losses induced by the metallic electrodes to perform electro‐optic modulation. A figure of merit of 9.2 V cm has been obtained for the switching voltage‐interaction length product, which is slightly higher than the calculated theoretical value using the overlap between the externally applied electrical field and the propagating optical field. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49:1194–1196, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22376
Design and modeling of RF MEMS switch by reducing the number of interfaces
Authors: Sboui N. , Gharsallah A. , Baudrand H. , Gharbi A. 
Published: March 2007

AbstractThe transverse wave concept iterative procedure is presented for full wave investigation of MEMS capacitive switch. Using the transverse wave approach we can reduce the number of interfaces in planar circuit by the introduction of adequate boundary conditions. The circuit plane includes four subdomains: Metal (M), Dielectric (I), Sources (S1 and S2), and switch (SW). The switch subdomain is characterized as a lumped element model in the two states that are on and off. Taking use of the major advantages of the wave concept iterative procedure method offered by the developed fast modal transform (FMT), which is based on the 2D‐FFT algorithm, minimum computation time, and less memory, is needed to calculate the scattering parameters of the switch. Two different MEMS switches are studied that are the cantilever and the air bridge. The simulated results for these examples show very good agreement compared with those obtained by other methods. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1166–1170, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22378
Design approach for realizing two‐dimensional electromagnetic band gap structures
Authors: Shaker George S. A. , Safavi‐Naeini Safieddin 
Published: March 2007

AbstractThis paper presents a simple approach for designing two‐dimensional electromagnetic band gap structures (EBGs). The approach is based on designing a planar band pass filter at a desired center frequency. A simple modification is introduced to the well known design steps of the filter. This modification allows for specifying the high impedance property of the structure, as well as its stop band, using a circuit simulator. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49:1189–1192, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22382
Closely coupled triple layer hybrid FSS/EBG for increased directivity
Authors: Davies Ryan W. , Morrow Ivor L. 
Published: March 2007

AbstractA novel frequency selective surface (FSS)/electromagnetic bandgap material (EBG) is presented, which operates as a spectral (frequency domain) and spatial/directional filter. The filter antenna filter (FAF) is shown to increase directivity of a compact EBG monopole antenna in simulation and measurement, resulting in a gain of 15 dB. The FAF can achieve a filtering response equivalent to multiple stacked λ/4 separated FSSs with a triple layer tightly coupled (0.16λ electrical length) surface. Its reflection phase properties exhibit those of an EBG material in its operating frequency making it possible to integrate closely to a radiating source and its reflector. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1125–1128, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI.10.1002/mop.22387
Picosecond ultra‐wideband short pulse radiated by antenna arrays
Authors: Ruan Chi , Zhao Wei , Chen Guo‐Fu , Zhu Shao‐Lan , Liu Bai‐Yu , Yang Hong‐Chun , Ruan Cheng‐Li 
Published: March 2007

AbstractThis report presents the experiments to study the characteristics of the picosecond ultra‐wideband pulses coherent radiation. The testing involves bow‐tie horn antennas for both the transmitting and receiving antenna. Sixteen channels of electrical pulses with 290 ps duration and jitter <30 ps have been used. The antenna arrays with various frames of 4 × 1, 4 × 2, 4 × 3, 4 × 4 are employed to radiate the pulses. The receiving antenna measures the electrical field in different distance from the transmitting antennas array. The results show that if the pulses are in coherent condition, the peak power pulse of output by antennas array with N elements are N2of that of the single element antenna. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1148–1151, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI.10.1002/mop.22391
Design of compact microstrip diplexer with simple coupled resonators
Authors: Weng Min‐Hang , Wu Hung‐Wei , Shu Kevin 
Published: March 2007

AbstractThis article presents a microstrip diplexer with 2.4/5.2 GHz response by using the simple coupled resonators for reducing the circuit size. Stepped impedance resonator (SIR) can be shared by the two filter channels for the designed diplexer if their fundamental and the higher order frequencies are properly assigned. The diplexer has only three simple resonators which can achieve both two good passbands and effectively reduce the circuit size. Measured results of the proposed diplexer have a good agreement with the electromagnetic (EM) simulated results. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1222–1225, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI.10.1002/mop.22397
Numerical computation of the Green′s function of a layered media with rough interfaces
Authors: Altuncu Yasemin , Yapar Ali , Akduman Ibrahim 
Published: March 2007

AbstractA numerical method for the calculation of the Green's function related to a layered media containing rough interfaces is presented. The method is based on the assumption that the perturbations of the rough surfaces from planar ones are objects located at both sides of the planar boundaries. Such an approach allows one to formulate the problem as a scattering of cylindrical or spherical waves from buried bodies, which can be solved by means of MoM. The method is effective for surfaces having a localized and arbitrary roughness. This asymptotic behavior of the Green's function is also derived for large distances. The Green's function obtained here is applied to some direct and inverse scattering problems related to objects buried in a layered background to see its effectiveness and applicability. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1204–1209, 2007; Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/mop.22401
Proton transfer ratio, lactate, and intracellular pH in acute cerebral ischemia
Authors: Jokivarsi Kimmo T. , Gröhn Heidi I. , Gröhn Olli H. , Kauppinen Risto A. 
Published: March 2007

AbstractThe amide proton transfer ratio (APTR) from the asymmetry of the Z‐spectrum was determined in rat brain tissue during and after unilateral middle cerebral artery occlusion (MCAo). Cerebral lactate (Lac) as determined by 1H NMR spectroscopy, water diffusion, and T1ρ were quantified as well. Lac concentrations were used to estimate intracellular pH (pHi) in the brain during the MCA occlusion. A decrease in APTR during occlusion indicated acidification from 7.1 to 6.79 ± 0.19 (a drop by 0.3 ± 0.2 pH units), whereas pHi computed from Lac concentration was 6.3 ± 0.2 (a drop by 0.8 ± 0.2 pH units). Despite the disagreement between the two methods in terms of the size of the change in the absolute pHi during ischemia, ΔAPTR and pHi (and Lac concentration) displayed a strong correlation during the MCAo. Diffusion and T1ρ indicated cytotoxic edema following MCA occlusion; however, APTR returned slowly toward the values determined in the contralateral hemisphere post‐ischemia. These data argue that the APTR during ischemia is affected not only by pHi but by other physicochemical factors as well, and indicates different aspects of pathology in the post‐ischemic brain compared to those that influence water diffusion and T1ρ. Magn Reson Med 57:647–653, 2007. © 2007 Wiley‐Liss, Inc.
Concomitant gradient field effects in balanced steady‐state free precession
Authors: Sica Christopher T. , Meyer Craig H. 
Published: March 2007

AbstractLinear magnetic field gradients spatially encode the image information in MRI. Concomitant gradients are undesired magnetic fields that accompany the desired gradients and occur as an unavoidable consequence of Maxwell's equations. These concomitant gradients result in undesired phase accumulation during MRI scans. Balanced steady‐state free precession (bSSFP) is a rapid imaging method that is known to suffer from signal dropout from off‐resonance phase accrual. In this work it is shown that concomitant gradient phase accrual can induce signal dropout in bSSFP. The spatial variation of the concomitant phase is explored and shown to be a function of gradient strength, slice orientation, phase‐encoding (PE) direction, distance from isocenter, and main field strength. The effect on the imaging signal level was simulated and then verified in phantom and in vivo experiments. The nearest signal‐loss artifacts occurred in scans that were offset from isocenter along the z direction with a transverse readout. Methods for eliminating these artifacts, such as applying compensatory frequency or shim offsets, are demonstrated. Concomitant gradient artifacts can occur at 1.5T, particularly in high‐resolution scans or with additional main field inhomogeneity. These artifacts will occur closer to isocenter at field strengths below 1.5T because concomitant gradients are inversely proportional to the main field strength. Magn Reson Med 57:721–730, 2007. © 2007 Wiley‐Liss, Inc.
Correction for geometric distortion and N/2 ghosting in EPI by phase labeling for additional coordinate encoding (PLACE)
Authors: Xiang Qing‐San , Ye Frank Q. 
Published: March 2007

AbstractEcho‐planar imaging (EPI) is vulnerable to geometric distortion and N/2 ghosting. These artifacts can be analyzed with an intuitive k‐t space tool, and here we propose a simple method for their correction. In a slightly modified additional EPI acquisition, we sample the k‐t space with a shift in ky by adding a small area to the phase‐encoding (PE) gradient. Physically, the added gradient area creates a relative phase ramp across the object and directly encodes the undistorted original y‐coordinate of each voxel into a phase difference between two distorted complex images, in a method called “phase labeling for additional coordinate encoding” (PLACE). The phase information is then used to map the mismapped signals back to their original locations for geometric and intensity correction. Smoothing of expanded complex data matrix effectively reduces noise in the differential phase map and allows subpixel warping. The two acquired images can also be averaged to effectively suppress the N/2 ghost. Efficient correction for both artifacts can be achieved with three acquisitions. These acquisitions can also serve as reference scans to correct for geometric distortion and/or N/2 ghost artifacts on all images in a time series. The technique was successfully demonstrated in phantom and animal studies. Magn Reson Med 57:731–741, 2007. © 2007 Wiley‐Liss, Inc.
Assessment of the morphological and functional effects of the anti‐angiogenic agent SU11657 on 9L gliosarcoma vasculature using dynamic susceptibility contrast MRI
Authors: Quarles C.C. , Schmainda K.M. 
Published: March 2007

AbstractTo investigate the influence of anti‐angiogenic agents on tumor perfusion, we employed a dynamic susceptibility contrast (DSC)‐MRI method that utilizes a simultaneous gradient‐echo (GE) and spin‐echo (SE) imaging sequence to derive perfusion parameters (blood flow, blood volume, and mean transit time (MTT)). These parameters are sensitive to both the total vasculature (from the GE data) and the microvasculature (from the SE data), and can also provide a measure of the mean vessel diameter (mVD). This approach was used to evaluate the response of a 9L rat brain tumor model to 20 mg/kg and 40 mg/kg of the anti‐angiogenic agent SU11657. The 20‐mg/kg dose significantly decreased mVD by 29.9% (P = 0.02). The 40‐mg/kg dose significantly decreased mVD by 30.4% (P = 0.0007), SE blood volume by 31.8% (P = 0.03), GE and SE MTT by 46.9% (P = 0.03) and 62.0% (P = 0.0005), and increased GE and SE blood flow by 36.6% (P = 0.04) and 52.6% (P = 0.02). These findings demonstrate that DSC‐MRI perfusion methods can play a key role in the noninvasive evaluation of morphological and functional changes in tumor vasculature in response to therapy. Magn Reson Med 57:680–687, 2007. © 2007 Wiley‐Liss, Inc.
Strategies for improved temporal and spectral resolution in in vivo oximetric imaging using time‐domain EPR
Authors: Devasahayam Nallathamby , Subramanian Sankaran , Murugesan Ramachandran , Hyodo Fuminori , Matsumoto Ken‐Ichiro , Mitchell James B. , Krishna Murali C. 
Published: March 2007

AbstractA radiofrequency (RF) time‐domain electron paramagnetic resonance (EPR) instrument operating at 300, 600, and 750 MHz was used to image tumor hypoxia with high spatial and temporal resolution. A high‐speed signal‐averaging Peripheral Component Interconnect (PCI) board with flexibility in the input signal level and the number of digitized samples per free induction decay (FID) was incorporated into the receive arm of the spectrometer. This enabled effective and fast averaging of FIDs. Modification of the phase‐encoding protocol, and replacement of the General Purpose Interface Bus (GPIB)‐based handshake with a PCI‐based D/A board for direct control of the gradient amplifier decreased the gradient settling and communication overhead times by nearly two orders of magnitude. Cyclically‐ordered phase sequence (CYCLOPS) phase cycling was implemented to correct for pulse imperfections and cancel out unwanted constant signals. These upgrades considerably enhanced the performance of the imager in terms of image collection time, sensitivity, and temporal resolution. We demonstrated this by collecting a large number of 2D images successively and rapidly. The results show that it is feasible to achieve accurate, 2D pO2 maps of tumor hypoxia with 1‐mm2 resolution and minimal artifacts using a set of multigradient images within an acceptable measuring time of about 3 s, and 3D maps can be obtained in less than 1 min. Magn Reson Med 57:776–783, 2007. © 2007 Wiley‐Liss, Inc.
Gradient‐echo and CRAZED imaging for minute detection of Alzheimer plaques in an APPV717I × ADAM10‐dn mouse model
Authors: Faber Cornelius , Zahneisen Benjamin , Tippmann Frank , Schroeder Anja , Fahrenholz Falk 
Published: March 2007

AbstractDifferent strategies to visualize amyloid plaques with MRI at 17.6 Tesla were investigated in a novel mouse model of Alzheimer's disease (AD). Large iron‐containing plaques were observed in the thalamus, but cortical plaques did not show iron deposits. Plaques in the thalamus were visualized in vivo with the use of low‐resolution, 3D gradient‐echo (GRE) imaging in 82 s, and with 94‐μm resolution in 34 min. The feasibility of obtaining bright contrast from plaques using the COSY revamped with asymmetric z‐GRE detection (CRAZED) technique was investigated in experiments on fixed brains. The original CRAZED approach provided reduced signal near the plaques (similarly to GRE imaging) and additionally emphasized small structures in the brain. In CRAZED images acquired with mismatched gradients, elevated signal near the plaques was obtained, while background signal was suppressed almost to the noise level. Bright‐contrast images were acquired in 2.6 min with the use of a 2D GRE sequence with slightly mismatched slice refocusing gradients. For future detection of plaques in patients, such bright‐contrast visualization protocols may be of particular value when contrast agents that allow labeling of early plaques with iron oxide nanoparticles become available. Magn Reson Med 57:696–703, 2007. © 2007 Wiley‐Liss, Inc.
Projection reconstruction MR imaging using FOCUSS
Authors: Ye Jong Chul , Tak Sungho , Han Yeji , Park Hyun Wook 
Published: March 2007

AbstractThe focal underdetermined system solver (FOCUSS) was originally designed to obtain sparse solutions by successively solving quadratic optimization problems. This article adapts FOCUSS for a projection reconstruction MR imaging problem to obtain high resolution reconstructions from angular under‐sampled radial k‐space data. We show that FOCUSS is effective for projection reconstruction MRI, since medical images are usually sparse in some sense and the center region of the undersampled radial k‐space samples still provides a low resolution, yet meaningful, image essential for the convergence of FOCUSS. The new algorithm is successfully applied for synthetic data as well as in vivo brain imaging obtained by under‐sampled radial spin echo sequence. Magn Reson Med 57:764–775, 2007. © 2007 Wiley‐Liss, Inc.
Myocardial and liver iron status using a fast T quantitative MRI (TqMRI) technique
Authors: Maris Thomas G. , Papakonstantinou Olympia , Chatzimanoli Vasiliki , Papadakis Alekos , Pagonidis Konstantinos , Papanikolaou Nickolas , Karantanas Apostolos , Gourtsoyiannis Nicholas 
Published: March 2007

AbstractThis work demonstrates the use of a fast and precise methodology for evaluating myocardial and liver iron status in multitransfused thalassemic patients by means of a fast T quantitative MRI (TqMRI) technique. Myocardial and liver T values were calculated in 48 thalassemic patients and 21 normal subjects on a 1.5T MRI system using a breath‐hold 2D single‐slice multiecho gradient‐echo (MEGRE) sequence (16 echoes, TR/TE1/TE16/FA = 160/2.7/37.65 ms/25°). No ECG gating was used. Myocardial T, liver T, and myocardial to muscle (CR/MS) and liver to muscle (LV/MS) T ratios were correlated with serum ferritin concentration (SFC) levels for all patients. Significant differences in myocardial and liver mean T, CR/MS, and LV/MS T values between patients and normal subjects were found (P < 0.0005). Differences in paraspinous muscle mean T values between patients and normal subjects were not significant. Myocardial T and CR/MS T values were not correlated with SFC levels. Liver T and LV/MS T values were significantly correlated with SFC (r = 0.540, P < 0.0005). Myocardial T and CR/MS T values were not correlated with either liver T or LV/MS T values, respectively. We conclude that myocardial and liver iron deposition can be evaluated using the fast non‐ECG‐gated TqMRI technique. Magn Reson Med 57:742–753, 2007. © 2007 Wiley‐Liss, Inc.