Showing papers in "Electronics & Communication Engineering Journal in 1994"
TL;DR: A tutorial introduction to the theory, implementation and interpretation of the wavelet transform to the time-scale (time-frequency) analysis of discrete signals.
Abstract: Wavelets and wavelet transforms are a relatively new topic in signal processing. Their development and, in particular, their application remains an active area of research. This paper presents a tutorial introduction to the theory, implementation and interpretation of the wavelet transform. The paper concentrates on the application of the wavelet transform to the time-scale (time-frequency) analysis of discrete signals. Examples are given of the analysis of basic test signals and of an actual electrocardiographic signal.<
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159Â citations
TL;DR: In this paper, the results of a two-year research program aimed at the development of practical adaptive-antenna signal-processing structures are presented, based on a series of analysis and field trial activities undertaken with an adaptive antenna test bed.
Abstract: Adaptive-antenna techniques offer the possibility of increasing the performance of mobile radio communication systems by maximising directional gain and enhancing the protection towards multipath conditions. The net effect of these techniques is to improve immunity to interference, extend the range of each cell and thus increase the system capacity. The paper presents the results of a two year research programme aimed at the development of practical adaptive-antenna signal-processing structures. Specifically, results obtained from a series of analysis and field trial activities undertaken with an adaptive antenna test bed and based around the DECT cordless standard are presented.
88Â citations
TL;DR: In this article, the use of differential reflectivity measurements in determining rainfall rates, microwave attenuation and the phase of hydrometeors is discussed and examples of radar scans and applications of the radar are presented.
Abstract: An ex-air-surveillance S-band radar was installed on the 25 m antenna at Chilbolton, near Winchester, over 20 years ago for studies of the effects of rain on communications systems. Since that time the functionality of the radar has been steadily developed to keep it at the forefront of meteorological research radars throughout the world. Recent developments have added phase and Doppler capabilities to the radar. The paper briefly discusses the use of differential reflectivity measurements in determining rainfall rates, microwave attenuation and the phase of hydrometeors. The new hardware and signal processing are described and examples of radar scans and applications of the radar are presented.
80Â citations
TL;DR: The constraints imposed by the nature of the microwave radio channel along with some of the main challenges in the design of the radio interface are described.
Abstract: The high performance radio local area network (HIPERLAN) standard is currently being developed by the European Telecommunications Standards Institute (ETSI). As well as providing a wired LAN substitute, with a target bit rate of 20 Mbit/s, the standard will provide for the creation of ad hoc networks, communication with mobile users, and access to interactive multimedia services. Radio spectrum has been recommended for HIPERLAN in the 5 GHz and 17 GHz bands. The constraints imposed by the nature of the microwave radio channel along with some of the main challenges in the design of the radio interface are described.
64Â citations
TL;DR: In this article, the authors describe a concept for a compact pointing, acquisition and tracking (PAT) system which employs a passive antivibration mount to filter out highfrequency disturbances from the satellite.
Abstract: Free-space links between satellites provide a means of introducing increased connectivity into a satellite system. This can result in enhanced traffic capacity and extended coverage for telecommunication systems and real-time relay of instrument data to the ground for Earth observation missions. Optical links offer the potential advantages over microwave links of lower mass and power and reduced size so that they can be accommodated more easily on the satellite. However the narrow optical beamwidths involved result in stringent pointing, acquisition and tracking (PAT) requirements. This paper describes a concept for a compact PAT system which employs a passive antivibration mount to filter out high-frequency disturbances from the satellite. This is under development as part of the ESA-funded Small Optical User Terminal (SOUT) programme. The system concept, hardware implementation, and results of breadboarding critical items are presented.
56Â citations
TL;DR: The issues and design solutions for complex low-power digital CMOS IC design for commercial application areas and the needs for portability are considered.
Abstract: The increasing levels of circuit integration are leading to the implementation of highly sophisticated algorithms. Many of the commercial application areas have a requirement for portability, which leads to the need for low-power design. This paper considers the issues and design solutions for complex low-power digital CMOS IC design.
35Â citations
TL;DR: In this paper, the physical principles behind their operation and how their unique characteristics are set to bring about a qualitative change in the way in which optical fiber is used are described. But their physical principles are not discussed.
Abstract: Like many technological advances associated with optical fibre communication, erbium-doped fibre amplifiers have moved from the laboratory to the field with extraordinary speed. They are capable of low-noise, low-distortion, high-gain and high-power operation over a broad bandwidth. The paper describes the physical principles behind their operation and shows how their unique characteristics are set to bring about a qualitative change in the way in which optical fibre is used.
20Â citations
TL;DR: The three main spread-spectrum techniques are outlined and then applications of frequency-hopping systems and some of the techniques used are described.
Abstract: Spread-spectrum modulation can be used in a radio system to reduce the likelihood of intercept, as well as providing some protection against jamming and interference. These antijam, anti-interference and low-probability-of-intercept properties are highly desirable in secured communication systems. In addition, spread-spectrum techniques have been proposed to combat spectral congestion by improving the efficiency of spectrum utilisation. Spread-spectrum techniques are also widely used in ranging systems and in local-area networks (LANs) or other multiple-access systems. In the present article, the three main spread-spectrum techniques are outlined and then applications of frequency-hopping systems and some of the techniques used are described.
20Â citations
TL;DR: The network architecture and basic nodal functions are explained, and a brief review given of the essential intelligent network building blocks, namely the IN (intelligent network) call model and the enhanced CCITT No.7 signalling system.
Abstract: This paper looks first at the background to the development of intelligent networking concepts and then tracks this development to the advanced intelligent networks (AINs) of today. The network architecture and basic nodal functions are explained, and a brief review given of the essential intelligent network building blocks, namely the IN (intelligent network) call model and the enhanced CCITT No.7 signalling system. Typical intelligent network services are examined and the tutorial finishes with a review of the latest IN standards.
17Â citations
TL;DR: The arguments for and against the adoption of these techniques are presented with illustrations from practical development projects and some of the key principles behind self-timed operation are reviewed.
Abstract: Self-timed and asynchronous design techniques are currently proposed as a vehicle for pushing digital integrated circuits to higher levels of density and performance. The arguments for and against the adoption of these techniques are presented with illustrations from practical development projects. Some of the key principles behind self-timed operation are reviewed. Design tools to enable complex practical applications to be engineered are considered. For engineers who wish to find out more a selection of key references is provided.
14Â citations
TL;DR: In this article, the physical mechanisms involved in the interaction of optical and microwave signals are described through the consideration of photo-effects within microwave GaAs FETs, and current applications relevant to hybrid and monolithic constructions are given and the discussion extended to potential future developments.
Abstract: The distinct advantages of optical transmission systems and the increasing use of microwave frequencies within general communication systems, coupled with the ability to integrate microwave and optical components onto a single slice of gallium arsenide have stimulated considerable interest in the development of microwave optoelectronic systems. The paper reviews the electro-optic techniques for achieving direct optical control of microwave signals, and provides some insight into the historical development of the subject. The physical mechanisms involved in the interaction of optical and microwave signals are described through the consideration of photo-effects within microwave GaAs FETs. Current applications relevant to hybrid and monolithic constructions are given and the discussion extended to potential future developments.<
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TL;DR: In this paper, the acoustic properties of sewage and characteristics of a sonar survey system have been described, and measurements have been made to determine the acoustic property of sewage, and the characteristics have been undergoing trials.
Abstract: Between 5 and 10% of closed-circuit television surveys of sewers in the UK are abandoned because the images are not sufficiently clear when the camera becomes submerged. Ultrasonic scanning can overcome this problem. The paper describes measurements which have been made to determine the acoustic properties of sewage and the characteristics of a sonar survey system which has been undergoing trials.
TL;DR: This tutorial paper describes the main features of ATM, a new telecommunications technology which is being developed and standardised for use with broadband services.
Abstract: Asynchronous transfer mode (ATM) is a new telecommunications technology which is being developed and standardised for use with broadband services. This tutorial paper describes the main features of ATM.
TL;DR: The paper considers one category of sensors suitable for structural integration, namely fibre-optic sensors, and examines their role in the domain of future smart structures, and concludes that fibre- Optic sensors are likely to play a key role in such structures of the future.
Abstract: The idea of 'smart' structures, which are designed to react to the conditions of their internal or external environment, has attracted considerable attention from scientists and engineers alike. In such structures of the future, integrated sensors will be utilised to monitor the 'health' of the structure, thus warning of the onset of abnormal conditions which might, for instance, compromise its safety. The paper considers one category of sensors suitable for structural integration, namely fibre-optic sensors, and examines their role in the domain of future smart structures. >
TL;DR: It is possible to establish communication between different MSK modems employing different formulations of MSK by simple processing of the data, and how to convert from one formulation to another by manipulating the input or output data is shown.
Abstract: Minimum shift keying (MSK) is a digital modulation scheme which is suited to demanding applications requiring good bandwidth efficiency and error performance. It can be regarded as continuous phase frequency shift keying (CPFSK) with two signalling frequencies. In general, there is no unique mapping from the input data polarity to the particular signalling frequency during a given bit interval. The simplest formulation maps zeros of the data (marks) to the lower frequency, and ones (spaces) to the higher frequency. Other formulations of MSK employ more complex mappings. The article summarises the most commonly encountered mappings, then shows how to convert from one formulation to another by manipulating the input or output data. It is, therefore, possible to establish communication between different MSK modems employing different formulations of MSK by simple processing of the data.
TL;DR: The design and performance of a number of uniplanar MMIC couplers, amplifiers, and other test circuits fabricated using the GEC-Marconi (Caswell) foundry are described.
Abstract: `Uniplanar' techniques have recently been introduced for the design of monolithic microwave integrated circuits (MMICs). The aim of these techniques is to achieve a higher level of integration of circuitry and to overcome the need for through-substrate via holes and the related back-face processing steps. This is achieved by using coplanar waveguide (CPW), slotline, and miniature `thin-film microstrip' transmission-line media as opposed to conventional microstrip. The design and performance of a number of uniplanar MMIC couplers, amplifiers, and other test circuits fabricated using the GEC-Marconi (Caswell) foundry are described.
TL;DR: The synchronous digital hierarchy (SDH) as mentioned in this paper is a single-world multiplexing standard that supports switched broadband telecommunication services and for a standard optical interface for use by interexchange carriers.
Abstract: The synchronous digital hierarchy (SDH) arose from a need for a new and single world multiplexing standard which could support switched broadband telecommunication services and for a standard optical interface for use by interexchange carriers. This tutorial paper reviews the features of SDH and outlines its frame structure. Network design and applications are reviewed and the paper concludes with a summary of the advantages of SDH.
TL;DR: In this article, the reasons for selecting the Global System for Mobile Communications (GSM) as the basis for the radio system are examined and changes required to provide the enhancements necessary for railway operation are detailed.
Abstract: Radio communications form an essential part of railway operations. However, across Europe, a range of often incompatible, analogue private mobile radio (PMR) type systems is currently in use. With new digital standards emerging, and increasing European harmonisation, the railway authorities, in line with the EC directive on the harmonisation of European High Speed Railway Network technology, have decided to standardise a new radio system for introduction from 1997 in order to allow interoperability and open competition from industry on a Europe-wide basis. In the paper, the reasons for selecting the Global System for Mobile Communications (GSM) as the basis for the radio system are examined and changes required to provide the enhancements necessary for railway operation are detailed. The resulting technology, which will become available to all GSM operators, might make cellular systems more attractive to current PMR users.
TL;DR: In this article, the basic technologies associated with measurements of monolithic microwave integrated circuits are introduced and the use of test fixtures and wafer probe stations at ambient room temperature is reviewed and their role at thermal and cryogenic temperatures is discussed.
Abstract: Introduces the basic technologies that are associated with measurements of monolithic microwave integrated circuits. The use of test fixtures and wafer probe stations at ambient room temperature is reviewed and their role at thermal and cryogenic temperatures is discussed. With the increasing need for performing non-invasive measurements, advances in experimental field probing techniques are explored. >
TL;DR: Satellites are no longer seen as an alternative to a terrestrial mobile telecommunications system or the (optical-fibre-based) integrated broadband communications network Instead they are now being considered as one of the components of the Universal Mobile Telecommunications System being developed within the European Union's RACE Programme for the next century and as a component of the broadband ISDN as discussed by the authors.
Abstract: Satellites are no longer seen as an alternative to a terrestrial mobile telecommunications system or the (optical-fibre-based) integrated broadband communications network Instead they are now being considered as one of the components of the Universal Mobile Telecommunications System being developed within the European Union's RACE Programme for the next century and as a component of the broadband ISDN This paper discusses the role played by satellites in these systems and the issues which have to be addressed >
TL;DR: A mobile radar scatterometer designed to complement the vertical incidence measurements of satellite radar altimeters has been successfully deployed in Antarctica and an Australian desert to make measurements contemporaneous with satellite observations as discussed by the authors.
Abstract: The interpretation of satellite radar observations of the Earth's surface requires models to link the observations to physical processes. These models require validation through surface measurements. This paper describes a mobile radar scatterometer designed to complement the vertical incidence measurements of satellite radar altimeters. The instrument has been successfully deployed in Antarctica and an Australian desert to make measurements contemporaneous with satellite observations. The key findings from these field experiments are briefly described and results which have implications for synthetic aperture radar studies of similar terrain are presented.
TL;DR: In this article, the effect of RF currents on cables and connectors is assessed using their transfer impedance and it is explained why application of this test in real life depends critically on the electrical length of the cable.
Abstract: Cable and connector screening is given as transfer impedance, which relates a voltage seen inside the component to the current on its outside. One transient disturbance comes from switching on the local mains network, which results in large RF currents flowing in an instrument cable nowhere near the original source. The effect of this current on cables and connectors is assessed using their transfer impedance and it is explained why application of this test in real life depends critically on the electrical length of the cable. The screening performance of different components is compared and an attempt made to explain why some are much better than others. This is extended to outlining the effect of cable construction and detailing the importance of connector design. In conclusion an outline is given of the problems which are found in braid optimisation and how the measurement of cable and connector screening can be used in system design-not just to show one to be better or worse than another.
TL;DR: In this paper, the authors discuss the use of diffraction theory to compute the radiation patterns of low-gain antennas installed on conducting structures, and discuss the benefits of using diffraction to evaluate the performance of antennas on aircraft or spacecraft.
Abstract: It is the performance of an antenna when installed in a complete system that is important. In situ measurements and measurements on scale models can be impractical or too costly. Computation of the performance of antennas on aircraft or spacecraft has considerable advantages, and may use the method of moments or diffraction theory. The paper concentrates on discussing the use of diffraction theory to compute the radiation patterns of low-gain antennas installed on conducting structures.
TL;DR: The background to the user-network interface specification is examined and a description of the control plane, user plane, management plane, the ATM bearer, and signalling protocols are presented along with the key issues that were considered.
Abstract: Broadband ISDN requires a clear and unambiguous specification of the interface between customers' equipment and the public network - the user-network interface-so that equipment and networks can be developed that will work together. A project was carried out under the RACE collaborative programme to develop a specification for this interface. This paper examines the background to the user-network interface specification and describes in broad terms its contents. A description of the control plane, user plane, management plane, the ATM bearer, and signalling protocols are presented along with the key issues that were considered.
TL;DR: In this paper, the future capability of optical communication technology vastly exceeds the use that we make of it today, and opportunities are now opening up to completely bypass large parts of established telecommunication networks with immensely powerful new networks having very different properties to the long-established ones.
Abstract: Research shows that the future capability of optical communication technology vastly exceeds the use that we make of it today. The result is that opportunities are now opening up to completely bypass large parts of established telecommunication networks with immensely powerful new networks having very different properties to the long-established ones. `Free' bandwidth may soon be a near reality with major consequences for today's network operators.
TL;DR: The relationship between data and information is explored, as is the difficulty of passing information across system interfaces, and some potentially fruitful areas for future research by a new generation of information technologists are suggested.
Abstract: The paper examines the impact of information technology on senior managers, taking the military commander as an illustrative example. The relationship between data and information is explored, as is the difficulty of passing information across system interfaces. The human-computer interface involves the translation between data and information, and contextual understanding and human psychology are just as important as technology in this translation. Methods of helping the commander to deal with the data explosion are discussed and some potentially fruitful areas for future research by a new generation of information technologists are suggested.
TL;DR: In this paper, the authors trace the history of CCITT modem recommendations from the 1960s until the present, and present an alternative design approach which offers potential advantages for the simpler, yet currently still popular, modem specifications.
Abstract: The paper starts by tracing the history of CCITT modem recommendations (the V-series) from the 1960s until the present. This leads into a review of the methods of implementation used in current products. With cost minimisation in mind, an alternative design approach is then outlined which offers potential advantages for the simpler, yet currently still popular, modem specifications. The paper concludes with a glimpse into the future by outlining the latest CCITT V.fast proposals.
TL;DR: In this article, the authors argue that duplicating local telecommunications plants is a mistake and should stop; price cap regulation produces the wrong result; and an authoritative engineering agency is needed to co-ordinate technology nationally.
Abstract: Following privatisation in 1984, BT was mainly preoccupied with customer service, operating costs and business exploitation. BT, its competitors and the industry regulators now have to address major new network issues. Their success in meeting the challenges of the new technologies will have a major impact on the future of UK telecommunications equipment manufacturers. The author takes a hard look at the facts. He argues that duplicating local telecommunications plant is a mistake and should stop; price cap regulation produces the wrong result; and an authoritative engineering agency is needed to co-ordinate technology nationally.