|
| ||
|
|
||
Broadband
Terms modified by Broadband Selected AbstractsOPTIMAL AND ADAPTIVE SEMI-PARAMETRIC NARROWBAND AND BROADBAND AND MAXIMUM LIKELIHOOD ESTIMATION OF THE LONG-MEMORY PARAMETER FOR REAL EXCHANGE RATES,THE MANCHESTER SCHOOL, Issue 2 2005SAEED HERAVI The nature of the time series properties of real exchange rates remains a contentious issue primarily because of the implications for purchasing power parity. In particular are real exchange rates best characterized as stationary and non-persistent; nonstationary but non-persistent; or nonstationary and persistent? Most assessments of this issue use the I(0)/I(1) paradigm, which only allows the first and last of these options. In contrast, in the I(d) paradigm, d fractional, all three are possible, with the crucial parameter d determining the long-run properties of the process. This study includes estimation of d by three methods of semi-parametric estimation in the frequency domain, using both local and global (Fourier) frequency estimation, and maximum likelihood estimation of ARFIMA models in the time domain. We give a transparent assessment of the key selection parameters in each method, particularly estimation of the truncation parameters for the semi-parametric methods. Two other important developments are also included. We implement Tanaka's locally best invariant parametric tests based on maximum likelihood estimation of the long-memory parameter and include a recent extension of the Dickey,Fuller approach, referred to as fractional Dickey,Fuller (FD-F), to fractionally integrated series, which allows a much wider range of generating processes under the alternative hypothesis. With this more general approach, we find very little evidence of stationarity for 10 real exchange rates for developed countries and some very limited evidence of nonstationarity but non-persistence, and none of the FD-F tests leads to rejection of the null of a unit root. [source] Porous Polymer Films with Gradient-Refractive-Index Structure for Broadband and Omnidirectional Antireflection CoatingsADVANCED FUNCTIONAL MATERIALS, Issue 2 2010Xiao Li Abstract Porous polymer films that can be employed for broadband and omnidirectional antireflection coatings are successfully shown. These films form a gradient-refractive-index structure and are achieved by spin-coating the solution of a polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA)/PMMA blend onto an octadecyltrichlorosilane (OTS)-modified glass substrate. Thus, a gradient distribution of PMMA domains in the vertical direction of the entire microphase-separated film is obtained. After those PMMA domains are removed, a PS porous structure with an excellent gradient porosity ratio in the vertical direction of the film is formed. Glass substrates coated with such porous polymer film exhibit both broadband and omnidirectional antireflection properties because the refractive index increases gradually from the top to the bottom of the film. An excellent transmittance of >97% for both visible and near-infrared (NIR) light is achieved in these gradient-refractive-index structures. When the incident angle is increased, the total transmittance for three different incident angles is improved dramatically. Meanwhile, the film possesses a color reproduction character in the visible light range. [source] Waiting for Broadband: Local Competition and the Spatial Distribution of Advanced Telecommunication Services in the United StatesGROWTH AND CHANGE, Issue 2 2004TONY H. GRUBESIC ABSTRACT With the passage of the Telecommunications Act of 1996, Congress directed the Federal Communications Commission and all fifty U.S. states to encourage the deployment of advanced telecommunication capability in a reasonable and timely manner. Today, with the rollout of advanced data services such as digital subscriber lines (xDSL), cable modems, and fixed wireless technologies, broadband has become an important component of telecommunication service and competition. Unfortunately, the deployment of last-mile infrastructure enabling high-speed access has proceeded more slowly than anticipated and competition in many areas is relatively sparse. More importantly, there are significant differences in the availability of broadband services between urban and rural areas. This paper explores aspects of broadband access as a function of market demand and provider competition. Data collected from the Federal Communications Commission is analyzed using a geographic information system and spatial statistical techniques. Results suggest significant spatial variation in broadband Internet access as a function of provider competition in the United States. [source] Broadband proton-decoupled proton spectra,MAGNETIC RESONANCE IN CHEMISTRY, Issue 4 2007Andrew J. Pell Abstract We present a new method for recording broadband proton-decoupled proton spectra with absorption mode lineshapes and substantially correct integrals; in both these respects, the new method has significant advantages over conventional J -spectroscopy. In our approach, the decoupled spectrum is simply obtained from the 45° projection of the diagonal-peak multiplets of an anti z -COSY spectrum. This method is straightforward to apply, and does not require any unusual data processing. However, there is a significant reduction in sensitivity when compared to a conventional proton spectrum. The method is demonstrated for typical medium-sized molecules, and it is also shown how such a decoupled spectrum can be used to advantage in measurements of diffusion constants (DOSY), the measurement of relaxation parameters, and the analysis of complex mixtures. Copyright © 2007 John Wiley & Sons, Ltd. [source] Broadband gap-coupled half hexagonal microstrip antennasMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 2 2008K. P. Ray Abstract Three configurations of compact gap-coupled half hexagonal microstrip antennas have been presented for broad bandwidth. Parametric studies for the effect of coupling gap and feed point location on the performance of these antennas have been investigated and the results have been validated experimentally. Increase in bandwidth is more than twice for the two configurations and about four times for the third case when compared with that of the corresponding hexagonal microstrip antenna. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 271,275, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23069 [source] Broadband circularly polarized wide-slot antennaMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 5 2007R. P. Xu Abstract A new broadband single-fed circularly polarized (CP) wide-slot antenna is presented in the letter. The antenna is composed of a wide-slot, with a T-shaped stub and a microstrip T-junction. The CP operation is realized by the interaction from the T-shaped stub on the wide-slot and the T-junction. The antenna has been investigated numerically and experimentally. Measured result shows that the antenna has an impedance bandwidth of 58% and a 3-dB bandwidth of axial ratio of 22.2%. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1005,1007, 2007; Published online in Wiley InterScience (www.interscience.wiley.com).DOI 10.1002/mop.22337 [source] Broadband circularly polarized inverted-L patch antennaMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 2 2003Che-Wei Su Abstract An innovative design of a corner-truncated inverted-L patch antenna for achieving circular polarization (CP) operation over a wide bandwidth is presented. The antenna has a thick air-layer substrate; however, it can be easily excited using a probe feed with a short probe pin. CP operation is obtained by selecting an optimal size of the truncated corners, and good impedance matching over a wide bandwidth is obtained by using a beveling technique on the vertical portion of the inverted-L patch. For a prototype constructed for wireless local area network (WLAN) operation in the 2.4-GHz band (2.4,2.484 GHz), the obtained CP bandwidth (3-dB axial ratio) reaches about 7%, and the measured antenna gain is about 8.0 dBi across the CP bandwidth. Details of the antenna design and the experimental results are presented. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 134,136, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10995 [source] Slice-selective FID acquisition, localized by outer volume suppression (FIDLOVS) for 1H-MRSI of the human brain at 7,T with minimal signal lossNMR IN BIOMEDICINE, Issue 7 2009Anke Henning Abstract In comparison to 1.5 and 3,T, MR spectroscopic imaging at 7,T benefits from signal-to-noise ratio (SNR) gain and increased spectral resolution and should enable mapping of a large number of metabolites at high spatial resolutions. However, to take full advantage of the ultra-high field strength, severe technical challenges, e.g. related to very short T2 relaxation times and strict limitations on the maximum achievable B1 field strength, have to be resolved. The latter results in a considerable decrease in bandwidth for conventional amplitude modulated radio frequency pulses (RF-pulses) and thus to an undesirably large chemical-shift displacement artefact. Frequency-modulated RF-pulses can overcome this problem; but to achieve a sufficient bandwidth, long pulse durations are required that lead to undesirably long echo-times in the presence of short T2 relaxation times. In this work, a new magnetic resonance spectroscopic imaging (MRSI) localization scheme (free induction decay acquisition localized by outer volume suppression, FIDLOVS) is introduced that enables MRSI data acquisition with minimal SNR loss due to T2 relaxation and thus for the first time mapping of an extended neurochemical profile in the human brain at 7,T. To overcome the contradictory problems of short T2 relaxation times and long pulse durations, the free induction decay (FID) is directly acquired after slice-selective excitation. Localization in the second and third dimension and skull lipid suppression are based on a T1 - and B1 -insensitive outer volume suppression (OVS) sequence. Broadband frequency-modulated excitation and saturation pulses enable a minimization of the chemical-shift displacement artefact in the presence of strict limits on the maximum B1 field strength. The variable power RF pulses with optimized relaxation delays (VAPOR) water suppression scheme, which is interleaved with OVS pulses, eliminates modulation side bands and strong baseline distortions. Third order shimming is based on the accelerated projection-based automatic shimming routine (FASTERMAP) algorithm. The striking SNR and spectral resolution enable unambiguous quantification and mapping of 12 metabolites including glutamate (Glu), glutamine (Gln), N -acetyl-aspartatyl-glutamate (NAAG), , -aminobutyric acid (GABA) and glutathione (GSH). The high SNR is also the basis for highly spatially resolved metabolite mapping. Copyright © 2009 John Wiley & Sons, Ltd. [source] Broadband targeted UVB phototherapy for localized vitiligo: a retrospective studyPHOTODERMATOLOGY, PHOTOIMMUNOLOGY & PHOTOMEDICINE, Issue 3 2009Ahmet Akar Phototherapy with ultraviolet B (UVB) or PUVA has been used in the treatment of vitiligo for many years. The aim of this study was to analyze retrospectively the efficacy and safety of targeted broadband UVB phototherapy in patients with localized vitiligo. Thirty-two patients (14 male, 18 female), aged 18,65 years, were treated with Daavlin T500x High Dose Targeted Phototherapy System. Patients were treated twice or thrice weekly, totaling 20 to 60 sessions. Out of 32 total patients, only four patients (12.5%) showed visible repigmentation. In two patients, repigmentation was more than 75%. Other two patients showed mild repigmentation (less than 25%). All the lesions responsive to treatment were facial lesions. Mild adverse events recorded in 3 of 32 patients. Although safety of targeted broadband UVB phototherapy in the treatment of localized vitiligo is good, its therapeutic effectiveness is limited and depends on the locations of vitiligo lesions. [source] Combustion Measurements of Fuel-Rich Aluminum and Molybdenum Oxide Nano-Composite MixturesPROPELLANTS, EXPLOSIVES, PYROTECHNICS, Issue 2 2010Tim Bazyn Abstract Fuel rich nano-composite powders of aluminum and molybdenum oxide were tested for ignition and combustion behind the incident and reflected shock waves in a shock tube. The powders consisted of approximately 10,,m particles, each of which contained Al and MoO3 mixed by mechanical alloying on the nano-scale. These powders were aluminum rich with composition ratios of 4,:,1, 8,:,1, and 16,:,1 Al,:,MoO3 by mass. Ignition tests were performed behind incident shocks for temperatures in the range of 900 to 1500,K. From these tests, ignition delay times were obtained, and some information on combustion duration was also derived. Samples were tested in air at 0.2,MPa, and compared against nano-Al, 2.7,,m Al, and 10,,m Al baselines. Ignition results for the baseline Al cases were as expected: 10,,m Al not igniting until 2000,K, 2,,m Al igniting down to ,1400,K, and n-Al igniting as low as 1150,K. The thermite samples showed considerable improvement in ignition characteristics. At the lowest temperature tested (900,K), both the 8,:,1 and 4,:,1 samples ignited within 250,,s. The 16,:,1 sample (94% Al) ignited down to 1050,K , which represents an improvement of roughly 1000,K over baseline Al with only a small energetic penalty. In all cases, the ignition delay increased as the amount of MoO3 in the composite was reduced. The 4,:,1 nano-composite material ignited as fast or faster than the n-Al samples. Ignition delay increased with decreasing temperature, as expected. Emission spectra and temperature data were also taken for all samples using high-speed pyrometry and time-integrated spectroscopy. In these cases, measurements were made behind the reflected shock using end-wall loading, though the conditions (temperature, pressure, and gas composition) were identical to the incident shock tests. Spectroscopy showed strong AlO features in all the samples, and the spectra fit well to an equilibrium temperature. Broadband, low resolution spectra were also fit to continuum, gray body temperatures. In general, the observed temperatures were reasonably close to 3500,K, which is similar to the combustion temperatures of pure aluminum under these conditions. [source] Performance assessment of next-generation wireless mobile systemsBELL LABS TECHNICAL JOURNAL, Issue 4 2009Krishna Balachandran The deployment of third generation (3G) systems such as Universal Mobile Telecommunications System (UMTS) and code division multiple access (CDMA) 1X is now ubiquitous. Furthermore, several operators have already deployed evolved 3G systems such as high speed packet access (HSPA) and 1× evolution data optimized (1× EV-DO). These 3G and evolved 3G systems are based on spread spectrum technologies. Now the industry has begun to focus on next-generation wireless systems based on orthogonal frequency division multiplexing (OFDM) technology, flat-Internet Protocol (IP) architectures, and advanced multiple input-multiple output (MIMO) capabilities. These next-generation technologies, primarily are: 3rd Generation Partnership Project (3GPP)-based evolved UMTS terrestrial radio access network (EUTRAN), also called Long Term Evolution (LTE); 3rd Generation Partnership Project 2 (3GPP2)-based Ultra Mobile Broadband (UMB); and Institute of Electrical and Electronics Engineers (IEEE) 802. 16e-based Worldwide Interoperability for Microwave Access (WiMAX). These technologies are in the final specifications to initial deployment phases in selected markets. This paper provides an overview and performance analysis of these next-generation technologies based on their initial releases. Additionally, a comparative performance analysis of these technologies is also presented. © 2009 Alcatel-Lucent. [source] Examining Drivers of Course Performance: An Exploratory Examination of an Introductory CIS Applications CourseDECISION SCIENCES JOURNAL OF INNOVATIVE EDUCATION, Issue 1 2006Rhonda A. Syler ABSTRACT The accelerating diffusion of broadband Internet access provides many opportunities for the development of pedagogically robust Web-based instruction (WBI). While the supporting technology infrastructure of broadband disseminates, the attention of academic researchers focuses upon issues such as the drivers of student usage of WBI. Specifically, the research presented herein examined the impact of WBI on a student's aggregate course performance. We hypothesized that learning independence (LI) is a determinate factor in a student's use of WBI. In this study, we employed structural equation modeling techniques to examine the data and assess the direct and indirect effects of LI on WBI usage. The subjects, students in an introductory Computer Information Systems applications course, used a Web-based tutorial program for skills instruction. The findings of this study suggest that WBI usage has a significant impact on a student's course performance. Despite its plausibility, the effect of LI on WBI usage was not significant. However, we did conclude that two of the second order factors of the LI construct have a direct effect on a student's performance in the course. [source] Clinical Improvement of Solar Lentigines and Ephelides with an Intense Pulsed Light SourceDERMATOLOGIC SURGERY, Issue 6 2002Akira Kawada MD background. A noncoherent, broadband, intense pulsed light (IPL) source has been used for the symptoms of photoaging skin as a nonablative method. objective. To investigate the efficacy and tolerability of IPL in solar lentigines and ephelides on the face. methods. An open study was performed in patients with solar lentigines and ephelides who received three to five treatments of IPL. results. Forty-eight percent of patients had more than 50% improvement and 20% had more than 75% improvement. In the group of solar lentigines, 40% of patients showed more than 50% improvement and 16% had more than 75% improvement. Patients with small plaques of solar lentigines responded well, whereas patients with small + large and large plaques showed poor response. Patients with solar lentigines + ephelides and ephelides responded remarkably with 75% and 71% of patients, respectively, having more than 50% improvement. conclusion. IPL was well tolerated and may be a new modality for the therapy of solar lentigines and ephelides. [source] On the reliability of long-period response spectral ordinates from digital accelerogramsEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 5 2008Roberto Paolucci Abstract Using records from co-located broadband and digital strong motion (SM) instruments, it is first shown that the displacement waveforms obtained by double integration of the accelerogram need not be free of unrealistic baseline drift to yield reliable spectral ordinates up to at least 10,s. Secondly, to provide objective criteria for selecting reliable digital SM records for ground motion predictions at long periods, a set of synthetic accelerograms contaminated by random long-period noise has been used, and the difference between the original accelerograms and the spurious ones in terms of response spectra has been quantified, by introducing a noise index that can be easily calculated based on the velocity waveform of the record. The results of this study suggest that high-pass filtering the digital acceleration record from a cutoff period selected to suppress baseline drifts on the displacement waveform appears to be in most cases too conservative and unduly depletes reliable information on long-period spectral ordinates. Copyright © 2007 John Wiley & Sons, Ltd. [source] Porous Polymer Films with Gradient-Refractive-Index Structure for Broadband and Omnidirectional Antireflection CoatingsADVANCED FUNCTIONAL MATERIALS, Issue 2 2010Xiao Li Abstract Porous polymer films that can be employed for broadband and omnidirectional antireflection coatings are successfully shown. These films form a gradient-refractive-index structure and are achieved by spin-coating the solution of a polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA)/PMMA blend onto an octadecyltrichlorosilane (OTS)-modified glass substrate. Thus, a gradient distribution of PMMA domains in the vertical direction of the entire microphase-separated film is obtained. After those PMMA domains are removed, a PS porous structure with an excellent gradient porosity ratio in the vertical direction of the film is formed. Glass substrates coated with such porous polymer film exhibit both broadband and omnidirectional antireflection properties because the refractive index increases gradually from the top to the bottom of the film. An excellent transmittance of >97% for both visible and near-infrared (NIR) light is achieved in these gradient-refractive-index structures. When the incident angle is increased, the total transmittance for three different incident angles is improved dramatically. Meanwhile, the film possesses a color reproduction character in the visible light range. [source] Waiting for Broadband: Local Competition and the Spatial Distribution of Advanced Telecommunication Services in the United StatesGROWTH AND CHANGE, Issue 2 2004TONY H. GRUBESIC ABSTRACT With the passage of the Telecommunications Act of 1996, Congress directed the Federal Communications Commission and all fifty U.S. states to encourage the deployment of advanced telecommunication capability in a reasonable and timely manner. Today, with the rollout of advanced data services such as digital subscriber lines (xDSL), cable modems, and fixed wireless technologies, broadband has become an important component of telecommunication service and competition. Unfortunately, the deployment of last-mile infrastructure enabling high-speed access has proceeded more slowly than anticipated and competition in many areas is relatively sparse. More importantly, there are significant differences in the availability of broadband services between urban and rural areas. This paper explores aspects of broadband access as a function of market demand and provider competition. Data collected from the Federal Communications Commission is analyzed using a geographic information system and spatial statistical techniques. Results suggest significant spatial variation in broadband Internet access as a function of provider competition in the United States. [source] Contrasting roles of neural firing rate and local field potentials in human memoryHIPPOCAMPUS, Issue 8 2007Arne Ekstrom Abstract Recording the activity of neurons is a mainstay of animal memory research, while human recordings are generally limited to the activity of large ensembles of cells. The relationship between ensemble activity and neural firing rate during declarative memory processes, however, remains unclear. We recorded neurons and local field potentials (LFPs) simultaneously from the same sites in the human hippocampus and entorhinal cortex (ERC) in patients with implanted intracranial electrodes during a virtual taxi-driver task that also included a memory retrieval component. Neurons increased their firing rate in response to specific passengers or landmarks both during navigation and retrieval. Although we did not find item specificity in the broadband LFP, both ,- and ,-band LFPs increased power to specific items on a small but significant percent of channels. These responses, however, did not correlate with item-specific neural responses. To contrast item-specific responses with process-specific responses during memory, we compared neural and LFP responses during encoding (navigation) and retrieval (associative and item-specific recognition). A subset of neurons also altered firing rates nonspecifically while subjects viewed items during encoding. Interestingly, LFPs in the hippocampus and ERC increased in power nonspecifically while subjects viewed items during retrieval, more often during associative than item-recognition. Furthermore, we found no correlation between neural firing rate and broadband, ,-band, and ,-band LFPs during process-specific responses. Our findings suggest that neuronal firing and ensemble activity can be dissociated during encoding, item-maintenance, and retrieval in the human hippocampal area, likely relating to functional properties unique to this region. © 2007 Wiley-Liss, Inc. [source] Liquid Crystals: Electrically Tuneable Liquid Crystal Photonic Bandgaps (Adv. Mater.ADVANCED MATERIALS, Issue 38-39 200939/2009) On p. 3915, Stephen Morris and co-workers demonstrate broadband wavelength tuning of a photonic bandgap that is electrically driven in a chiral nematic liquid crystal. Remarkably, this tuning is not only broadband but is found to occur without altering the reflection quality of the optical structure. In addition, under certain conditions, the helical structure can be made to exhibit multiple bandgaps across the visible spectrum. [source] Performance evaluation of GPON vs EPON for multi-service accessINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 2 2009T. Orphanoudakis Abstract Recently both ITU and IEEE have standardized solutions for passive optical networks (PONs) operating at gigabit per second line rates and optimized for the transport of packet-based traffic to improve the efficiency of previously standardized broadband PONs, which used the ATM cell as the data transport unit. The efficiency and performance of PON systems depend on the transmission convergence layer and mainly on the implemented medium access protocol. Although the latter is not part of the standards and left to the implementer, the standards describe a set of control fields that constitute the tool-set for the media access control (MAC) operation. Though starting from a common and quite obvious basis, the two standards present significant differences with the legacy of Ethernet marking the IEEE approach, while the emphasis of ITU is on demanding services. In this paper we compare the efficiency and performance of the two systems assuming the implementation of as close as possible MAC protocols. The target is twofold: assess and compare the traffic handling potential of each of the two standards and identify the range of applications they can support. Useful insight can also be gained to the MAC tools that could be designed into the next generation extra large WDM PONs. Copyright © 2008 John Wiley & Sons, Ltd. [source] Passive rational fitting of a network transfer function from its real partINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 3 2008Anne Y. Woo Abstract A methodology is presented for the rational function approximation of a passive network function from sampled values of its real part over the bandwidth of interest. The accuracy and validity of the proposed methodology are demonstrated through its application to the fitting of several broadband, multiport transfer functions. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008. [source] Matching network design using non-Foster impedancesINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 2 2006*Article first published online: 8 FEB 200, Stephen E. Sussman-Fort Abstract Non-Foster synthesis bypasses the gain-bandwidth limitations of conventional LC matching and achieves superior broadband performance by employing negative circuit elements, which are realized via negative impedance converters. The idea is to construct a negative-image model of an antenna, which cancels the antenna's parasitic reactance and transforms its frequency-dependent radiation resistance to a constant value. Successful implementation of negative-image modeling requires the realization of stable, low-loss negative elements. After a discussion of the basic ideas of non-Foster matching, we present experimental results for broadband, stable, high- Q, grounded negative capacitance. Next, in the first experimental confirmation of non-Foster impedance matching for signal reception, we use a floating negative capacitor to cancel a substantial portion of the reactance of a 6-in. monopole antenna. Over 20,110 MHz, the signal-to-noise ratio improved by up to 6 dB as compared to the same antenna with no matching, or to a lossy-matched blade antenna of twice the size. © 2006 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2006. [source] 10W CW broadband balanced limiter/LNA fabricated using MSAG MESFET processINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 2 2003Inder J. Bahl Abstract This article presents the design and test data for a 10W broadband balanced limiter/LNA MMIC fabricated using MSAG MESFET process. The limiter is based on Schottky diodes and the two-stage LNA is designed using high-performance MESFETs. The typical measured performance for the limiter/LNA circuit includes gain greater than 14 dB, NF less than 2.7 dB, and return loss better than 20 dB over the 8.5,11.5 GHz frequency range. The CW power handling for the packaged limiter/LNA circuits was greater than 10W. The packaged devices were also exposed to power levels greater than 10W, and no catastrophic failures were observed up to 18W. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 13: 118,127, 2003. [source] A DVB/Inmarsat hybrid architecture for asymmetrical broadband mobile satellite servicesINTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 2 2006Bjørn Roger Andersen Abstract In order to bridge the gap, both regulatory and technologically, between offering mobile satellite services at L-band today and broadband mobile services at C-band, Ku-band or Ka-band in the future, a short-term solution is foreseen. Therefore, a DVB/Inmarsat hybrid service offering bi-directional asymmetrical satellite connectivity, with a broadband receive channel at Ku-band based on DVB-S, and with a transmit channel at L-band based on Inmarsat Mobile Packet Data Service, has successfully been developed, implemented and tested. The article focuses on the rationale for, and a technical solution, and how this can be evolved to support use of Inmarsat Broadband Global Area Access as transmit channel at L-band. There are no regulatory issues associated with global operation of such a system, and the users can access the services using cost-efficient off-the-shelf equipment, since the well established Inmarsat and DVB standards are utilized. The system has proved its feasibility to offer services like Internet access, email access, fast file transfers, and IP streaming of audio and video, in addition to the traditional Inmarsat services. Copyright © 2006 John Wiley & Sons, Ltd. [source] Satellite communications: the contribution of the 5th framework programme and future perspectivesINTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 1 2004Bernard Barani Abstract The telecommunication sector is of key importance for the European economy. Digitization, secure broadband access and mobility are expected to shift an ever-growing proportion of the economy on line, thus creating new markets and business opportunities. With the eEurope 2002 and eEurope 2005 initiatives, the European Union has initiated a number of policy actions aiming at favouring the rapid introduction of innovative communication systems, services and applications. Research and development, as supported under the IST programme of the Union, is closely associated to the overall policy picture. The IST programme is notably instrumental in supporting, with a longer-term approach, key policy orientations such as the pervasive introduction of low cost broadband access, introduction of advanced mobile systems, or migration of networks towards the next generation of Internet protocol, IPv6. Satellite communication form an integral part of this diversified communication landscape, and has also been significantly supported under the 5th Framework Programme. Even if the problematic of the satcom industry are to some extent similar to those of the terrestrial players (e.g. catalysing take up of broadband and advanced mobile markets), the strategies followed by the satcom sector differ from those followed by the terrestrial players. This paper review the current technological approaches of the satcom industry, their relevance in the context of the policy goals of the Union, and how they have been supported under the IST programme. It also introduces briefly how co-ordination with ESA work has been achieved, and the perspectives for further support, notably under the now starting 6th Framework Programme. Copyright © 2004 John Wiley & Sons, Ltd. [source] Two-beam multiplexed CARS based on a broadband oscillator,JOURNAL OF RAMAN SPECTROSCOPY, Issue 8 2010Kentaro Furusawa Abstract A two-beam multiplexed coherent anti-Stokes Raman scattering (CARS) microscopy setup is demonstrated by using a broadband (BB) Ti:sapphire oscillator without using any specialty fibres. A well-defined spectral structure of the source leads to a delay-sensitive CARS measurement in two-colour CARS and also provides an efficient means of obtaining three-colour CARS signals combined with the dispersion compensation of the BB pulse. Our result implies that the background suppression is limited by the onset of the spurious signals caused by the different CARS process, qualitatively differing from what is typically observed in the CARS microscopy. Copyright © 2010 John Wiley & Sons, Ltd. [source] Efficient broadband optical parametric amplification of supercontinuum in visible by narrowband pumpLASER PHYSICS LETTERS, Issue 5 2007D. V. Khakhulin Abstract It is shown that application of narrowband pump for non-collinear parametric amplification of supercontinuum radiation is more profitable than of broadband one. The usage of 0.5 nm bandwidth pump with energy of 350 ,J allowed us to get 20 percents signal-to-pump efficiency during amplification of supercontinuum radiation belonging to a spectral range between 550 and 750 nm. (© 2007 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Broadband proton-decoupled proton spectra,MAGNETIC RESONANCE IN CHEMISTRY, Issue 4 2007Andrew J. Pell Abstract We present a new method for recording broadband proton-decoupled proton spectra with absorption mode lineshapes and substantially correct integrals; in both these respects, the new method has significant advantages over conventional J -spectroscopy. In our approach, the decoupled spectrum is simply obtained from the 45° projection of the diagonal-peak multiplets of an anti z -COSY spectrum. This method is straightforward to apply, and does not require any unusual data processing. However, there is a significant reduction in sensitivity when compared to a conventional proton spectrum. The method is demonstrated for typical medium-sized molecules, and it is also shown how such a decoupled spectrum can be used to advantage in measurements of diffusion constants (DOSY), the measurement of relaxation parameters, and the analysis of complex mixtures. Copyright © 2007 John Wiley & Sons, Ltd. [source] Spin-echo MRI using ,/2 and , hyperbolic secant pulses,MAGNETIC RESONANCE IN MEDICINE, Issue 1 2009Jang-Yeon Park Abstract Frequency-modulated (FM) pulses have practical advantages for spin-echo experiments, such as the ability to produce a broadband , rotation, with an inhomogeneous radiofrequency (RF) field. However, such use leads to a nonlinear phase of the transverse magnetization, which is why FM pulses like the hyperbolic secant (HS) pulse are not commonly used for multislice spin-echo magnetic resonance imaging (MRI). Here, a general theory and methods are described for conventional spin-echo imaging using a , HS pulse for refocusing. Phase profiles produced by the HS pulse are analytically described. The analysis is extended to yield the specific relationships between pulse parameters and gradients, which must be satisfied to compensate the nonlinear phase variation produced with a spin-echo sequence composed of ,/2 and , HS pulses (the ,/2 HS , , HS sequence). The latter offers advantages for multislice spin-echo MRI, including excellent slice-selection and partial compensation for RF inhomogeneity. Furthermore, it can be implemented with a shorter echo time and lower power deposition than a previously described method using a pair of , HS pulses. Magn Reson Med 61:175,187, 2009. © 2008 Wiley-Liss, Inc. [source] Precipitable water vapour estimation on the basis of sky temperatures measured by a single-pixel IR detector and screen temperatures under clear skiesMETEOROLOGICAL APPLICATIONS, Issue 3 2010A. Maghrabi Abstract Precipitable water vapour (PWV) is an important component of the atmosphere, but remains difficult to measure with adequate spatial and temporal resolution under all weather conditions. Over the last four decades several techniques and methods have been developed to measure PWV more accurately, but each carries limitations preventing its widespread use. This paper presents preliminary results of a simple method for inferring PWV from the air temperature and infrared (IR) sky temperature under clear skies. Sky temperatures are measured using a broadband, single-pixel IR radiometer. A parametric model of the physical relationship between these three quantities was created using PWV data derived from a GPS receiver. By inverting the model, PWV estimates can be obtained from new temperature measurements. The measurements were taken between October 2002 and July 2004 in a coastal region of South Australia. The method was found to predict PWV quite accurately, with a mean bias error (MBE) of only , 0.009 mm and a root mean square error (RMSE) of 2.311 mm. The model was also compared to a set of 120 radiosonde-derived PWV values, resulting in a MBE and RMSE of 0.262 and 2.601 mm respectively. These preliminary results show that the clear sky PWV can be estimated accurately from sky temperatures obtained using a simple IR detector. Future work will extend the method to different sky and weather conditions. Copyright © 2009 Royal Meteorological Society [source] Broadband Wilkinson balun using pure left-handed transmission lineMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 7 2010Young-Ho Ryu Abstract Utilizing the opposite phase shift property of a microstrip line (MSL) and a pure left-handed transmission line (PLH TL), the broadband Wilkinson balun is designed. The PLH TL without a right-handed (RH) branch is designed using effectively negative elements obtained by a cross connection of vias to ground. The PLH TL gives inherently phase-advanced response properties because of negative phase velocity, whereas a conventional MSL has a phase-lag response. The property of a broadband left-handed branch of a PLH TL applies to the implementation of broadband balun. The proposed balun has a good return loss, a good isolation between output ports, an equal-power division, and a 180° ± 10° phase difference in a wide fractional bandwidth of ,71%. Furthermore, the wideband balun that has the fractional bandwidth of 107.8% is theoretically designed with the modified PLH TL having four unit cells. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1665,1668, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25242 [source] | ||||||||||||||||||||||||||||||||||