Showing papers in "Radio and Electronic Engineer in 1984"
TL;DR: In this article, the general properties of hybrid networks are described and two main types, the quadrature and the 0-180° types, are identified, and a list of uses of hybrid network in radio frequency circuits is given.
Abstract: The general properties of hybrid networks are described and two main types, the quadrature and the 0–180° types, are identified. A list of uses of hybrid networks in radio frequency circuits follows. Seventeen configurations of hybrid networks are given with diagrams showing the variations of their input and output parameters with frequency. The 3 dB transmission line coupler is described in more detail and multiplexers are mentioned.
20 citations
TL;DR: In this article, a microstrip version of this lens has been designed, constructed and tested, with the addition of a beam port overlap network to now provide nine beams with crossovers ≈ − 2 dB.
Abstract: A recent paper1 has described the design and performance of a waveguide-fed parallel plate lens which provides five beams from a sixteen element antenna array, with sidelobes ≈ − 20 dB and beam crossovers ≈ − 10dB, in the frequency band 8–12 GHz. A microstrip version of this lens has been designed, constructed and tested, with the addition of a beam port overlap network to now provide nine beams with crossovers ≈ − 2 dB. Fair performance is achieved at midband, but internal reflections are found to limit the bandwidth of the microstrip lens design.
18 citations
TL;DR: In this paper, a technique for implementing moving target indication (m.t.i.) in an independent bistatic radar receiver is described, where an oscillator at the receiver is primed at the instant of switch-on at the beginning of each p.r., such that its phase is determined by the clutter echo.
Abstract: The paper describes a technique for implementing moving target indication (m.t.i.) in an independent bistatic radar receiver. Conventional techniques for m.t.i., and the particular features and advantages of the bistatic radar configuration are also reviewed.The technique of phase priming by clutter echoes is suggested as a means for providing a coherent reference at the receiver, without need for any link between radar transmitter and receiver. An oscillator at the receiver is primed at the instant of switch-on at the beginning of each p.r.i. with a small sample of echo signal from close-in stable clutter, such that its phase is determined by that of the clutter echo. This enables m.t.i. processing to be obtained, just as with a conventional monostatic radar system.An experimental system using this principle is described, and results demonstrated and discussed.
16 citations
TL;DR: In this article, the seasonal, diurnal and longer term trends in the data are discussed and the cumulative distributions of event durations are presented for different groupings of the data.
Abstract: Results are presented of observations extending over a decade of propagation by means of sporadic-E ionization at frequencies in the range 59 to 77 MHz. The seasonal, diurnal and longer term trends in the data are discussed. Cumulative distributions of event durations are presented for different groupings of the data. A limited study of possible polarization discrimination at these frequencies is also described. The results are discussed in terms of their potential use in spectrum planning at frequencies around 70 MHz.
15 citations
TL;DR: In this article, the authors describe an experimental and theoretical study of the currents in typical circuits, and a set of maximum-current curves is presented, which form the basis of safe field-strength curves contained in the British Standard guide to the prevention of inadvertent initiation of electro-explosive devices by radio-frequency radiation.
Abstract: Radio waves can induce currents in electrical firing circuits used for blasting in quarries, and for similar industrial purposes, and could cause premature detonation if sufficiently strong. The paper describes an experimental and theoretical study of the currents in typical circuits, and a set of maximum-current curves is presented. These curves form the basis of a set of safe field-strength curves contained in the British Standard guide to the prevention of inadvertent initiation of electro-explosive devices by radio-frequency radiation.
12 citations
TL;DR: A high-speed local area network that uses a bus architecture and spread spectrum techniques to overcome the problems of contention in a system with distributed control is described.
Abstract: A high-speed local area network that uses a bus architecture and spread spectrum techniques to overcome the problems of contention in a system with distributed control is described. Each node uses a pseudo-random binary code to modulate the data to be transmitted, effectively 'spreading' the bandwidth of the signal, and may transmit independently without first sensing the media. Interference between simultaneous transmissions is avoided by the careful selection of the codes used. The paper presents a technical description of the system developed and compares its performance with other bus networks. The choice of codes to be used, and their effect on the maximum number of nodes allowed and the data rate is discussed. The performance of the system in a noisy environment is also considered.
10 citations
TL;DR: In this article, the authors discuss the manner in which jitter accumulates in a digital network with particular emphasis being given to accumulation along transmission systems and the important sources of jitter.
Abstract: Unless proper control is exercised in limiting the amplitude of jitter in future digital networks, serious degradations can arise. The important sources of jitter are identified and described. Trie manner in which jitter accumulates in a digital network is discussed with particular emphasis being given to accumulation along transmission systems. A brief review is given of the current status of jitter studies within international organizations (CCITT and CEPT).† The jitter control and specification philosophy for digital networks and equipments based on the 2048-kbit/s hierarchy is outlined.
10 citations
TL;DR: The internationally agreed end-to-end error performance specification for a digital connection is reviewed along with the methodology for allocating this overall objective to constituent transmission equipments operating over different media.
Abstract: The liability of a digital signal to error is one of the most significant transmission impairments experienced in a digital communication network. Consideration is given to the activities and status of studies within the International Telegraph and Telephone Consultative Committee (CCITT). The sources of interference causing errors are discussed and an introduction is given to Hypothetical Reference Connections (HRX). The internationally agreed end-to-end error performance specification for a digital connection is reviewed along with the methodology for allocating this overall objective to constituent transmission equipments operating over different media. A number of mathematical models are identified which might be adequately representative of the error characteristics to be found in real networks. Finally, measurement aspects are discussed.
9 citations
TL;DR: The development of a microprocessor based system for converting videotex pages to synthetic speech in real time, for the benefit of blind people, is described.
Abstract: Videotex is an electronic information service which allows the sighted user to access a vast amount of information via the telephone line, to be viewed on the screen of the domestic television receiver in a compact and colourful layout In this paper, the development of a microprocessor based system for converting videotex pages to synthetic speech in real time, for the benefit of blind people, is described The system has been successfully used by some blind people to access the British Telecom videotex service (Prestel)
8 citations
TL;DR: The results demonstrate that, although the receivers are small, light, cheap to manufacture and low in power consumption, their accuracy, fix repeatability and skywave interference sensitivity compare favourably with those of traditional analogue receivers.
Abstract: The paper deals with the design principles of a type of microprocessor-based receiver for the Decca Navigator continuous-wave, hyperbolic radio-navigation system. Two experimental receivers are described, one for automatic vehicle location, the other hand-portable. Both are fully automatic in operation. Novel features of their hardware software are outlined and the results of land-vehicle, marine, airborne and hand-held field trials are presented. The results demonstrate that, although the receivers are small, light, cheap to manufacture and low in power consumption, their accuracy, fix repeatability and skywave interference sensitivity compare favourably with those of traditional analogue receivers.
7 citations
TL;DR: The slip mechanism and the alternative methods of its minimization, i.e. the use of high accuracy clocks working in a plesiochronous mode or the phase locking of nodal clocks to a reference clock are discussed.
Abstract: The timing of signals and processes within integrated digital networks requires careful control in order to minimize signal degradation through the occurrence of slip. The paper discusses the slip mechanism and the alternative methods of its minimization, i.e. the use of high accuracy clocks working in a plesiochronous mode or the phase locking of nodal clocks to a reference clock.The progress of relevant international standardization activities in CCITT is discussed, particularly in relation to the specification of reference clocks, limits for tolerable slip performance and equipment design limits to cater for wander and jitter in the network.The approach taken to timing control within the international network and to synchronization techniques adopted by certain administrations with respect to synchronization methodology and network topology, clock configurations and interconnecting timing links are also given.
TL;DR: In this article, the role of ion implantation in the fabrication of optical waveguides in lithium niobate is described together with a review of work carried out in this field, in addition the waveguide structure and the process parameters which determine its characteristics are outlined.
Abstract: The role of ion implantation in the fabrication of optical waveguides in lithium niobate is describedtogether with a review of work carried out in this field. In addition the waveguide structure and the process parameters which determine its characteristics are outlined. Finally, the implications of this technology forthe fabrication of more complex integrated optical devices are discussed.
TL;DR: In this paper, the authors used linear programming technique to define an optimum sidelobe reducing network which introduces small mismatching losses when cascaded to a matched filter and evaluated the influence of quantization in a digital implementation.
Abstract: Binary phase-coded waveforms are widely used in modern radar systems. In linear receivers the sidelobes present at the output of the compression filter cause a reduction of the useful dynamic range. Many procedures have been developed to reduce the sidelobes based on a compensation of their Fourier spectra or on a design of an optimum single mismatched filter. The present paper uses linear programming technique to define an optimum sidelobe reducing network which introduces small mismatching losses when cascaded to a matched filter. The influence of quantization in a digital implementation is evaluated.
TL;DR: In this article, a simple single-ended forward converter, with d.c. current control, derived from the secondary power circuit, and an additional fixed voltage ramp is also included in the control loop to provide ''feedforward? compensation for input voltage disturbances, and also to extend the maximum duty cycle from 50% up to 100%.
Abstract: By adapting the forward converter range of switching regulators to include an additional current-controlled feedback loop, derived from either the secondary or primary power circuit, an improvement in the closed-loop performance of the switching regulator can be obtained. The basic analysis work examines the simple single-ended forward converter, with d.c. plus a.c. current control, derived from the secondary power circuit. An additional fixed voltage ramp is also included in the control loop to provide `feedforward? compensation for input voltage disturbances, and also to extend the maximum duty cycle from 50% up to 100%. Using this circuit configuration a simple small signal equivalent circuit for the current-controlled switching regulator can be obtained, enabling the performance of practical designs to be predicted. Practical implementation of the current mode control technique using a standard large-scale integrated circuit together with a number of applications is also given.
TL;DR: In this paper, a three-stage Darlington transistor is described which has been specifically designed for direct off-line power control and features fast, low-loss switching with direct drive from an integrated circuit.
Abstract: A recently developed three-stage Darlington transistor is described which has been specifically designed for direct off-line power control. The device features fast, low-loss switching with direct drive from an integrated circuit. The transistor has been designed with a very extensive safe operating area so that a snubber network is not required. The device is sufficiently robust to survive a number of system fault conditions and when used in conjunction with a suitable drive circuit, it can even withstand a short circuit load without damage.
TL;DR: New methods of detecting rotor position in stepping motors with chopper drives are described and accurate trajectory control in an XY table, where close position coordination between two motors is necessary; and velocity control in a two-motor system where mechanical interaction creates a variable inertia load for one motor.
Abstract: Stepping motors, as digital machines, are commonly used in electromechanical systems since they can easily be interfaced to and controlled by computers. Electrical and mechanical interaction in multiple-motor systems, however, can lead to severe control problems, and in intelligent systems such as programmable XYtables, rotor position feedback from each machine is necessary to implement effective control algorithms.This paper describes new methods of detecting rotor position in stepping motors with chopper drives. By monitoring the motor phase current waveforms and detecting the chopping current rise-times, motor phase excitation angle may be varied continuously over a step cycle, and performance may be maximized.Two industrial applications are described: accurate trajectory control in an XY table, where close position coordination between two motors is necessary; and velocity control in a two-motor system where mechanical interaction creates a variable inertia load for one motor.
TL;DR: In this article, the importance of the sampling frequency as a design parameter of sampled-data feedback control systems and its implication to the ability of the systems to withstand gross variations of the plant without unacceptable deviation from the desired performance is discussed.
Abstract: Attention is drawn to the importance of the sampling frequency as a design parameter of sampled-data feedback control systems and consideration is given to its implication to the ability of the systems to withstand gross variations of the plant without unacceptable deviation from the desired performance. It is seen that the robustness of a system is intimately related to the sampling frequency as a consequence of the limitations which it imposes on the achievable loop bandwidth. Conversely, for any specified degree of robustness, the minimum frequency of sampling is well defined. However, for plants with high-frequency dynamics such as the electro-hydraulic servo discussed within the paper, time constraints imposed by a dedicated microprocessor add to the restrictions of the sampling process in such a way that it may not be possible to guarantee the existence of a discrete compensator to satisfy the given specifications.
TL;DR: The ECS SMS and in particular the Single Channel Per Carrier (SCPC) access system is described, which incorporates a number of novel features including satellite-link encryption, the use of soft-decision error correction, and full support of terrestrial interface standards.
Abstract: The European Telecommunications Administrations are planning to offer Business Satellite Services from the beginning of 1985. Designed under the auspices of EUTELSAT, the Satellite Multiservice System (SMS) operates in the 14/12.5 GHz bands and will use two satellites: the European Communications Satellite (ECS), and capacity leased on the French domestic satellite, Telecom 1. This paper describes the ECS SMS and in particular the Single Channel Per Carrier (SCPC) access system. This system operates over a range of data rates from 64 kbit/s to 2 Mbit/s and incorporates a number of novel features including satellite-link encryption, the use of soft-decision error correction, and full support of terrestrial interface standards.
TL;DR: This paper reviews the evolution of digital transmission and switching in a telecommunication network, and emphasizes the importance of integration of networks and services.
Abstract: This paper reviews the evolution of digital transmission and switching in a telecommunication network, and emphasizes the importance of integration of networks and services. The concept of an Integrated Digital Network and an Integrated Services Digital Network are introduced and a brief review is given of the repertoire of transmission systems available in the United Kingdom to realize such networks. The objective of this introductory paper is to provide general background information supporting the companion papers in these special issues.
TL;DR: The basic concepts in testing are presented, beginning with fault-models, and the major contributions to the design of testable logic are summarized, and some of the current problems in v.i.l.s. testing and testability are identified.
Abstract: This paper presents the basic concepts in testing, beginning with fault-models, and summarizes the major contributions to the design of testable logic. It identifies some of the current problems in v.l.s.i. testing and testability which need further investigation.
TL;DR: A feasibility study into the use of broadcast telesoftware in secondary education was conducted jointly with the BBC and IBA using prototype equipment developed by Mullard, and is being extended to primary education.
Abstract: A feasibility study into the use of broadcast telesoftware in secondary education was conducted jointly with the BBC and IBA using prototype equipment developed by Mullard. Using the BBC Microcomputer and its teletext adapter the study is being extended to primary education and 40 schools are taking part in extensive trials
TL;DR: This paper considers the performance evaluation of the future Integrated Services Digital Network and focuses on both the measurement and the instrumentation necessary to quantify the most important digital transmission impairments, jitter and errors.
Abstract: This paper considers the performance evaluation of the future Integrated Services Digital Network. Emphasis is given to both the measurement and the instrumentation necessary to quantify the most important digital transmission impairments, jitter and errors. The trend towards non-intrusive measurement and automated testing made possible by advances in digital technology is reviewed
TL;DR: In this article, the authors reviewed the role of opto-electronics in modern electronic systems and concluded that the combined power of optics and electronics represents a formidable capability which is still at an early stage of development.
Abstract: Optical technology is playing an expanding role in modern electronic systems. Apart from the much publicized aspects of optical fibre communications, we are currently making use of opto-electronics in television cameras, displays, signal processing and sensors. The address briefly reviews the developing role of opto-electronics and concentrates on the three separate fields of communications, sensors and radar systems. It concludes that the combined power of optics and electronics represents a formidable capability which is still at an early stage of development. The broader impact of such changes within the profession is also touched upon.
TL;DR: In this paper, specific design aspects of long-haul digital submarine systems utilizing optical fibre bearer pairs are addressed. But no such systems have yet been deployed other than for field trial but development is well advanced.
Abstract: Following a table of typical system parameters, this paper seeks to address specific design aspects of long-haul digital submarine systems utilizing optical fibre bearer pairs. These aspects include · Reliability · Error performance specification and design philosophy · Receiver design, noise and intersymbol interference considerations · Jitter accumulation and control · Telemetry, supervision and fault location No such systems have yet been deployed other than for field trial but development is well advanced. The first systems should be deployed during the latter half of 1984.
TL;DR: By identifying the basic units of speech (phonemes) which are wrongly perceived and comparing these with known confusions arising in listening to real speech under difficult conditions, it was possible to identify the limitations of a given synthesizer.
Abstract: Commercially available speech synthesizers are now being used extensively in talking machines. As their numbers continue to grow, it is essential to establish standard evaluation tests as quality control checks in their manufacture. A contribution towards this goal is described in this paper. Listeners heard the output of two commercial synthesizers. By identifying the basic units of speech (phonemes) which are wrongly perceived and comparing these with known confusions arising in listening to real speech under difficult conditions, it was possible to identify the limitations of a given synthesizer.
TL;DR: The use of the general Bessel-type polynomial for group delay approximation has been investigated and results described in this article, where the polynomials yield better results and are superior to those proposed by Johnson and Johnson.
Abstract: The use of the general Bessel-type polynomial for group delay approximation has been investigated and results described. The polynomials yield better results and are superior to those proposed by Johnson and Johnson.
TL;DR: In this article, the authors describe a comprehensive evaluation of optical fiber transmission systems, both in a field environment and also under controlled conditions in the laboratory, and provide detailed information on the performance of optical systems from a number of commercial sources.
Abstract: The paper describes a comprehensive evaluation programme being carried out on optical fibre transmission systems, both in a field environment and also under controlled conditions in the laboratory. The work is providing detailed information on the performance of optical fibre systems from a number of commercial sources, in particular by monitoring the overall error performance and by measuring variations of parameters incorporated in the optical power budget. A data logging arrangement, which collects information from operational systems, and the laboratory test schedule are described. An overview of the results obtained to date is given, which concludes by validating the integrity of optical systems design.
TL;DR: In this paper, the authors developed a system developed can interface a central mini-computer to an established medium-size machine shop including a range of NC and CNC machine tools.
Abstract: The system developed can interface a central mini-computer to an established medium-size machine shop including a range of NC and CNC machine tools. The system distributes NC part program data as well as job planning and tooling data, eliminating many of the disadvantages associated with the use of paper tape, and enhancing machine tool utilization and thus return on capital investment. The system incorporates real-time machine-shop monitoring with an integrated communications and information network, which can encompass a multiplicity of departments within an organization, and as such is best described as a Factory Information System (FIS). The benefits include increased management control and the basis for a further development to a full flexible manufacturing system (FMS). The design of interface units and the structure of the software required to drive such a system are proposed.
TL;DR: In this article, a summary of the techniques available for implementing digital satellite transmission systems, then the authors discuss current and probable new error performance objectives that will be consistent with the requirements of the Integrated Services Digital Network (ISDN).
Abstract: The paper starts with a summary of the techniques available for implementing digital satellite transmission systems, then goes on to discuss current and probable new error performance objectives that will be consistent with the requirements of the Integrated Services Digital Network (ISDN). The main body of the paper discusses factors which affect performance, including capacity/quality trade-offs, satellite and Earth station parameters, atmospheric propagation conditions, interference and intermodulation. The conclusion indicates briefly the techniques available to a system designer to meet performance requirements.
TL;DR: In this paper, the authors describe some pioneering R&D work done by the second author, as a hobbyist inventor, for promoting electronic information processing in some LDC languages.
Abstract: The Lesser Developed Countries (LDCs) of the 1980s are fairly well aware of the modern technological trends and progress made in the more advanced countries, especially in electronic information technology and are quite eager to keep pace with them. But several obstacles lie in their path of progress. This paper amplifies the authors' experience of such problems, and describes some pioneering R&D work done by the second author, as a hobbyist inventor, for promoting electronic information processing in some LDC languages.