bluuebunny/crossref_metadata_2025_split huggingface dataset:
Core Hole Relaxation Energy in Semiconductors. Using a Pseudopotcntial Description of the Core Hole Perturbation
Authors: Castellani N. J. , Lambrecht W. R. L. 
Published: July 2007

AbstractCore hole relaxation energies in semiconductors are calculated by means of a linear response method, combining a model dielectric function with a pseudopotential description of the core hole perturbation. The latter incorporates the core‐orthogonality constraints on the valence electron screening charge density. Both, norm‐conserving pseudopotentials and Ashcroft‐like model pseudopotentials are used. The latter allow to obtain the results in closed analytical form. Atomic local density functional calculations are performed for the intra‐core contribution and combined with the valence electron contribution in the semiconductor, provide total relaxation energies.
Slocum Gliders: Robust and ready
Authors: Schofield Oscar , Kohut Josh , Aragon David , Creed Liz , Graver Josh , Haldeman Chip , Kerfoot John , Roarty Hugh , Jones Clayton , Webb Doug , Glenn Scott 
Published: July 2007

AbstractBuoyancy driven Slocum Gliders were a vision of Douglas Webb, which Henry Stommel championed in a futuristic vision published in 1989. Slocum Gliders have transitioned from a concept to a technology serving basic research and environmental stewardship. The long duration and low operating costs of Gliders allow them to anchor spatial time series. Large distances, over 600 km, can be covered using a single set of alkaline batteries. Since the initial tests, a wide range of physical and optical sensors have been integrated into the Glider allowing measurements of temperature, salinity, depth averaged currents, surface currents, fluorescence, apparent and inherent optical properties. A command/control center, entitled Dockserver, has been developed that allows users to fly fleets of gliders simultaneously in multiple places around the world via the Internet. Over the last 2.5 years, Rutgers Gliders have logged 27 056 kilometers, and flown 1357 days at sea. Gliders call into the automated Glider Command Center at the Rutgers campus via satellite phone to provide a status update, download data, and receive new mission commands. The ability to operate Gliders for extended periods of time are making them the central in situ technology for the evolving ocean observatories. Off shore New Jersey Gliders have occupied a cross shelf transect and have documented the annual variability in shelf wide stratification on the Mid‐Atlantic Bight and the role of storms in sediment resuspension. The sustained data permits scientists to gather regional data critical to addressing if, and how, the oceans are changing. © 2007 Wiley Periodicals, Inc.
Intelsat VI. A new satellite generation for 1986–2000
Authors: Thompson P. T. , Johnston E. C. 
Published: July 2007

AbstractFollowing three years of conceptual studies, and a competitive procurement contract, construction of the INTELSAT VI series of satellites is now under way. The design represents a major step forward in satellite size and technical complexity. Sixfold frequency reuse and on‐board satellite switching are particularly important developments.
Subjective evaluation of companded frequency modulation and continuously variable slope delta modulation single channel per carrier satellite communication systems
Authors: Abachi N. , Evans B. G. 
Published: July 2007

AbstractA comprehensive series of subjective tests are carried out on narrow‐band companded F.M. and continuously controlled delta modulation SCPC satellite systems. In order to resolve discrepancies reported in the literature both Youden square and mean opinion scale listening tests have been applied. Both white noise and modulated noise reference conditions are employed and the performance of the systems, in terms of signal to noise and equivalent Q factor are given for various C/N0 fixed and mobile‐maritime performance requirements.
Telematic services via satellite in Europe
Authors: Goumy C. , Golden E. 
Published: July 2007

AbstractThe word ‘telematics’ was used for the first time in France in 1978 by Simon Nora and Alain Minc; it is a contraction of the French words ‘tétécommunications’ and ‘informatique’, and defines a marriage between computers and data transmission networks. This paper describes the five systems which will be implemented to provide telematic services via satellite in Europe during the next few years: EUTELSAT, TELECOM 1, UNISAT, DFS and ITALSAT. The main characteristics of the ‘special service’ transponders are presented, showing that, in Europe, (a) 2 to 5 transponders per satellite will be devoted to the special (telematic) services; (b) 4 satellites out of the 5 use the 12.5–12.75 GHz down‐link band for this purpose (only ITALSAT uses the 20 GHz down‐link for the same purpose), and (c) e.i.r.p.s at 12 GHz are in the range 40–49 dBW.The ground and space segments corresponding to this new service are presented. The main peculiarity of the ground segment is the exclusive use of ‘small’ earth‐stations equipped with fixed antennas and SCPC or 25–60 Mb/s TDMA multiple access equipment. Telematic services include videoconference at 2048 kb/s, voice services, computer‐to‐computer transfer of data, data distribution, remote printing, electronic mail, high‐speed facsimile, offshore voice and data services, digital network overflow, transatlantic digital business etc…Customer bit rates start from 2.4, 4.8, 9.6 and 32 kb/s (for TELECOM 1) up to 2048 kb/s by 64 kb/s steps. Bit error rates are maintained below 10−6 (standard) or 10−10 (higher grade) during 99 per cent of the year using FEC. The five networks for telematics via satellite in Europe are independent. A large efficiency improvement of the different services should be obtained through a future interconnection of the various networks via intersatellite links.
Leased services on the intelsat system. Part 1: Domestic service and international television
Authors: Kelley T. Michael 
Published: July 2007

AbstractThis is Part One of a two‐part article on the current status of INTELSAT's leased services, a relatively unfamiliar subject when compared with INTELSAT's standard communications services.In Part One, domestic service and international television service will be covered. For both services, statistics on existing and planned levels of use will be provided. Key aspects of the terms and conditions governing the lease will be outlined, and the annual charges summarized. The variety of services possible when using these leases, and the earth station networks chosen by users to meet their communications goals are also described.A brief look at the future of these two services will be given, and the topics of Part Two. INTELSAT Business Service (IBS), and the low‐density telephony service (VISTA) will be introduced.
Multiple‐beam antennas for contiguous coverage of europe for business service applications
Authors: Claydon B. , Dinwiddy S. E. , Adatia N. 
Published: July 2007

AbstractDemands for increased channel capacity in future communication satellite systems coupled with basic limitations in terms of satellite power and frequency spectrum will lead to requirements for advanced multiple‐beam antenna systems with frequency re‐use capability.This paper describes the results of a study of multiple‐beam antenna systems suitable for an advanced European business services satellite. Initially, background work is described which serves to define the overall system, analyse the link performance and specify the antenna requirements. A generalized parametric study of the capabilities of a model antenna is discussed to set the bounds of feasibility, as it was appreciated that some specification targets might prove impossible to attain. In parallel, a comparative survey of a wide range of antenna types is presented to determine the most promising configurations. Based on these two outputs, candidate antenna configurations are analysed in detail to predict accurately the capability of the more promising antenna types to meet the range of performance objectives. Finally, detailed electrical design studies are performed for specific example missions.
Depolarization properties of metal space frame radomes for use in satellite communication systems
Authors: Rwabona‐Katashaya S. , Evans B. G. 
Published: July 2007

AbstractRadomes have traditionally only been used in military satellite systems. However, higher availability civil applications are demanding their consideration in the higher frequency bands and for dualpolarization frequency re‐use systems. This paper investigates the depolarization performance of metal space frame radomes and presents results of XPD for radome covered antennas in the 4/6 and 11/14 GHz bands and for antennas of 30, 11, 5 and 3 m diameters. It is demonstrated that current polarization specifications adopted in the INTELSAT system should be able to be met by radome covered earth‐stations using conventional antennas.
A reassessment of satellite communications in the 20 and 30 GHz bands
Authors: Bargellini Pier L. 
Published: July 2007

AbstractNotwithstanding the additional spectrum allocations of the 1979 World Administrative Radio Conference (WARC '79) and the ever‐increasing sophistication of spacecraft antennas which allow more intensive spectrum reuse, saturation of the 6/4 and 14/11 GHz bands is foreseeable by the late‐1990s.The next available frequency bands at 30/20 GHz were allocated at WARC '71, when knowledge of propagation phenomena and their effect on satellite communications systems performance was fragmentary. During the past 8 years, numerous experimental programmes have led to the acquisition of more precise information about hydrometeor‐induced propagation disturbances. Analysis of the data reveals that even with corrective means such as diversity and coding, service reliability of satellite communications systems with up‐links at 30 GHz and down‐links at 20 GHz could not reach 99.99 per cent as currently available at the lower frequencies and could be 98.0 per cent, or lower, in certain parts of the world. Since the conventionally proposed use of the 30/20 GHz bands does not lead to optimal solutions, alternative approaches are needed.An approach which would involve a revision of the spectrum allocations at 30/20 GHz is proposed. Placing both up‐ and down‐links around 20 GHz and redistributing the spectrum available at 20 GHz would prevent the intrinsic imbalance of the up‐ and down‐links with consequent higher reliability, reduced earth‐station transmitter power, reduced construction and operational costs, and simplification of the spacecraft transponders and antenna design.The use of frequencies around 30 GHz could be postponed until the 20 GHz bands became saturated. When the 30 GHz bands would eventually be used, there would be no imbalance of up‐ and down‐links.
High speed receiver designs based on surface acoustic wave devices
Authors: Nanayakkara S. , Anderson J. B. 
Published: July 2007

AbstractThe principles of operation and several types of surface acoustic wave devices are reviewed. One device, the interdigital transducer device, can accomplish matched filtering for complex bandwidth‐efficient phase modulations. Data speeds in excess of 120 Mb/s are accomplished with existing thin film lithography. Filters are cheap and small, and show little mismatch to the desired response. A number of receiver designs are proposed that are based on these filters. A bank‐of‐matched‐filters approach seems superior to the Viterbi algorithm at high speeds.
Experimental study and empirical evaluation of carrier compression and third order intermodulation products of unequal carriers in a communication satellite transponder
Authors: Rustogi Dipti , Sengupta N. 
Published: July 2007

AbstractCarrier compression and third order intermodulation products of two and three unequal carriers have been studied experimentally using a 36 MHz wide C‐band transponder of INSAT‐1B satellite. From the experimental data, empirical relations for carrier compression for two unequal carriers have been derived, which agree with the measured data within ±0.5 dB. The empirical relations for carrier compression derived for two unequal carriers have been extended to three unequal carriers and good correlations with measured data have been obtained. Empirical relations for third order intermodulation products of two and three (f1+f2‐f3 type) unequal carriers have also been derived.
An interactive computer program for elliptical beam optimization
Authors: Richharia M. 
Published: July 2007

AbstractElliptical antenna beams are used for planning of direct broadcast satellite systems. In this paper concepts of the beam optimization process are described briefly. A method of plotting the optimized beam on a suitable map projection is discussed. An interactive computer program, which can be used for the optimization and plotting of beams on a given territory, is described with the help of examples.
Intelsat tdma/dsi system: implementation and system management
Authors: Parthasarathy R. 
Published: July 2007

AbstractThis paper presents an overview of the concepts underlying the implementation of the TDMA/DSI technique in the INTELSAT satellite system, together with a description of preliminary ideas on the system management of TDMA networks. The TDMA project is an INTELSAT response to steady growth in international services, and the TDMA system uses digital techniques for enhancing capacity on a satellite. The establishment of the system requires international co‐operation on an extensive scale; all the decision‐making components in INTELSAT's structure have contributed to the planning and implementation of the system. Preliminary ideas on network management are discussed. The methods used for establishing internationally agreed procedures and for orchestrating the maintenance of reference stations are described.
The acquisition and synchronization control procedures for the intelsat tdma system
Authors: Bedford R. , Ishi Y. 
Published: July 2007

AbstractControl of all bursts in the TDMA system is achieved by the use of complementary controlled and controlling procedures. Controlled procedures operate in traffic terminals and reference terminals alike, whereas controlling procedures operate only in reference terminals. Controlling procedures are the subject of this paper. These procedures govern the acquisition, synchronization and monitoring of all bursts, including reference bursts, in the TDMA system.To perform the acquisition and synchronization control function, each reference burst contains a control and delay channel (CDC) in which control information is transmitted to controlled terminals on a constant repetitive basis. The structure and timing of this control cycle will be discussed, assuming that the basic control frame and multiframe structure is familiar.Acquisition and synchronization control is performed only on the principal burst transmitted by each terminal; all other bursts are monitored by the reference terminals and controlled by the SDNTX (selective do not transmit) message which is transmitted in the reference burst service channel on an as‐needed basis. The procedure which governs the generation of these messages will also be discussed.
Intelsat tdma system monitor
Authors: Barnett Jerry , Phiel John F. 
Published: July 2007

AbstractThe INTELSAT 120 Mb/s TDMA/DSI system consists of reference stations and traffic terminals which access the INTELSAT V satellites as a multiple beam network. Two reference stations located within each satellite beam serve the network by controlling the acquisition and synchronization of the traffic terminals and by performing TDMA system monitoring. Within the reference stations, the acquisition and synchronization control functions are performed by the reference terminal equipment and the monitoring functions are performed by the TDMA system monitor. This paper provides a discussion of the TDMA system monitor, including its configuration, measurement techniques, and an assessment of its measurement.
The french tdma terminal
Authors: Bernard A. , Kerromes L. , Meunier J. , Rancy F. , Bareyt C. , Vautier D. , Beaucent A. , Salomon J. , Sergent C. 
Published: July 2007

AbstractThe paper describes the TDMA terminal manufactured by the French consortium regrouping TEL‐SPACE, SAT and CIT‐ALCATEL. Details on terminal organization, equipment modularity and operational aspects are first presented. The constituent parts of the terminal (common TDMA terminal equipment, DSI/DNI module, order wire module) are then described. Results of modem performances are also indicated. Finally, a description of the first French earth‐station operating with TDMA, Pleumeur‐Bodou 6, is given.
The italian tdma‐dsi terminal for the intelsat system
Authors: La Rocca C. , Menciotti F. , Alletto G. , Argento D. 
Published: July 2007

AbstractThis paper describes the salient characteristics of the Italian TDMA‐DSI Terminal for the INTELSAT System. After an overall presentation, the major building blocks, i.e. the CLE, the modem and IF switchover, and the DSI TIM are discussed. A brief presentation of the maintenance and troubleshooting auxiliary equipment is also given.
A 120 mb/s qpsk modem designed for the intelsat tdma network
Authors: De Cristofaro R. , Mc Farthing A. L. 
Published: July 2007

AbstractThis paper presents the major aspects of a 120 Mb/s QPSK modem developed for use within the INTELSAT TDMA network. Particular attention is focused upon the most important elements of the modem, namely the pre‐modulation lowpass filters, the demodulator AGC, the carrier and symbol timing recoveries and the demodulator filtering strategy. In addition to the modem description, details of a burst mode bit error rate test equipment will also be given. This test equipment was especially designed to simulate a practical TDMA working environment thus enabling the modem's burst mode performance to be evaluated in laboratory conditions. Finally, the modem's measured probability of bit errors versus Eb/No, and the probability of clock and carrier cycle skips versus Eb/No are presented. Results of the modem performance both in IF and RF loop‐back are shown. The modem RF loop‐back performance was evaluated using an INTELSAT V satellite simulator.
An introduction to the pdts (pcm/dsi test set): design principles and application in the intelsat tdma/dsi system
Authors: Lai Daniel K. N. 
Published: July 2007

AbstractThe operational use of TDMA in the INTELSAT system brings about an exciting major milestone in satellite telecommunications. To a certain extent, the performance of the technically complex, robust, centrally controlled TDMA/DSI system depends on the effectiveness of the alignment, maintenance and testing procedures. The wide range of disciplines encountered in such an advanced system may raise difficulties for the station staffs currently familiar with the existing FDMA network.Such problems have given rise to the birth of a conceptually new test equipment PDTS (PCM/DSI test set) to evaluate the performance of the DSI or DNI unit in a TDMA terminal. This equipment is capable of generating PCM test patterns in predetermined sequences and feeding them at the baseband channel level into the terrestrial interface of the DSI for purposes of operationally testing channel continuity, DSI assignment and cumulative BER during the test cycle. The present paper describes the general principles of PDTS as well as its operational use in the TDMA/DSI system.
MEASUREMENTS OF THE TIME STATISTICS OF FMTV SPECTRA AND TV INTERFERENCE INTO FDM/FM CARRIERS
Authors: Nguyen Nam , Mazur B. , Prasanna S. 
Published: July 2007

AbstractWhen computing the amount of interference from FMTV signals in satellite systems, it is customary to consider that the only effective TV modulation is the energy dispersal signal (EDS). This leads to a sufficient but highly conservative system design, since for most of the time the wanted demodulated signal may experience interference levels well below that computed using this approach. If the time statistics of the interference can be determined through measurement, then a grade‐of‐service approach can be taken in which interference can be guaranteed not to exceed a certain level for more than a prescribed fraction of the time. This approach will lead to more efficient use of orbit/spectrum resources as a result of the implementation of less conservative system designs.This paper presents a simulation approach used to ‘measure’ FMTV power spectra with and without EDS and the corresponding interference powers into the basebands of FDM/FM carriers. Time statistics in the form of FMTV spectral masks and FDM baseband interference power time distributions have been derived from the measured data of 1000 off‐air TV frames for co‐channel TV and standard FDM/FM carrier sets (12 to 1200 channels) deployed by INTELSAT. Sample results are given.
The variability of the ionospheric total electron content and its effect on satellite microwave communications
Authors: Wolff Richard S. 
Published: July 2007

AbstractRotation of linearly polarized waves (Faraday rotation) passing through the ionosphere causes depolarization in frequency reuse satellite communication systems. As the ionospheric total electron content (TEC) is not constant, dynamic compensation for this effect may be required. This paper investigates the magnitude of the TEC variations, the time scales of the variability and the predictability of the excursions. Analysis of long‐term TEC measurements shows that the variations are statistical with yearly and seasonal trends strongly coupled to long term solar and geophysical effects. Short‐term variations are difficult to predict. Data indicate that reliable Faraday rotation estimates can be made for 99·9 per cent of the time, provided that long‐term solar, seasonal and geographical factors are considered. Occasional bursts of solar activity limit the accuracy of long‐term predictions.
System implications of 14/11 GHz path depolarization. Part I: Predicting the impairments
Authors: Rogers D. V. , Allnutt J. E. 
Published: July 2007

AbstractExploitation of the international 14/11 GHz communications bands will probably follow the same pattern as that of the 6/4 GHz bands. First, the available monopolarized bandwidth will be filled. Next, multiple beams that use spatial isolation to provide frequency reuse will be developed. Finally, full dual‐polarized operation will be employed. In the 14/11 GHz bands, rain can cause appreciable attenuation and depolarization. In some instances, dual polarized links will be depolarization limited. If up‐link power control is implemented on attenuation dominated paths, depolarization can again dominate, owing to interference constraints. In both cases, a measure of depolarization compensation needs to be introduced to reduce the impact of interference. Part I of this paper quantifies this problem and establishes a set of reference statistics which can be used to assess the need for impairment restoration. Part II will discuss several ways of reducing the system impact of path depolarization.