Broad-Band Communication Systems in Germany

In its overall responsibility as the major network provider in Germany, the Deutsche Bundespost launches all highly sophisticated technologies in order to serve the telecommunication market with those promising services which the national economy requires. In this contribution, some background information about the objectives can be found. The basic assumptions for the implementation of the future highly efficient totally integrated universal network achievable by a step-by-step strategy are mentioned and the existing and intended activities pointed out in more detail. As a result, the reader of this paper may recognize that there exists a well-defined German approach for handling the challenges of the future development in the telecommunication scenario, though not all of the trends of technological development can be assessed in detail.     

Architecture of Broad-Band Communications Systems

At present there are worldwide efforts directed towards a services-integrated broad-band network. The first section of this paper describes different solutions of broad-band network components such as subscriber premises networks, local loops, subscriber exchanges, and trunk networks. The design of these components was taken from various proposals and broad-band communication field trials carried out in several countries up to 1984. In the second section, we consider the possibilities and implications of integrated optical components and of optical coherent communication techniques for broad-band networks in the far future.     

Integrated Broad-Band Communication Systems in Belgium

Belgian politicians, the National Telecommunications Administration (RTT), and the telecommunication industry in general fully realize the major economic, industrial, and social importance of an advanced telecommunications infrastructure for the future of the country. A national effort is therefore underway. This paper describes the specific Belgian telecommunications environment, its development towards an ISDN infrastructure, and evolution towards the integration of telecommunication and distribution services into a uniform broad-band communication network. The present network structures for both telecommunication and distribution services are briefly discussed in this paper. Furthermore, plans and experiments in the area of ISDN are also described. Explanations related to the basic concepts of a national integrated broad-band communication network and possible architectures for a demonstration project are given.     

Integrated Circuits for Broad-Band Communications Systems

Integrated circuits for broad-band communication systems which enable broad-band communication between subscribers require LSI's with a performance concerning speed, complexity, and power dissipation which cannot be fully met by present semiconductor technologies. The requirements for coders and decoders, line transmission circuits, and broad-band switching network elements depend upon the system concept chosen. For one chosen system concept, these requirements are derived. By using a representative model for the development of the demand, characteristic curves for the demand of subscriber-line circuits and for central unit elements are resulting. From these curves the optimum semiconductor technologies, complexities, and design strategies are derived. It can be assumed that the results are rather independent of variations of system concept and introduction models.     

Broad-Band Communication Systems in Great Britain

Great Britain, like other advanced countries, stands on the threshold of rapid changes in the local network driven by the twin forces of technological opportunity, which permit new network architectures and service capability, and demand for new services which can be flexibly and speedily provided. The paper first discusses the commercial and regulatory environment. The development of cable TV networks is then examined, particularly the more advanced forms of networks which support a wide range of interactive services such as videotex, photo videotex, and interactive video. Scenarios for telecommunications networks evolution are then outlined taking account of optical fiber systems and reliable VLSI circuitry developments. The two forms of network are compared and notable points of similarity are highlighted which suggest a natural convergence. Finally, some thoughts are presented on the possible nature of the network from this convergence.     

High-Speed and Broad-Band Communication Systems in Japan

This paper presents the current state of each high-speed and broad-band system and the development of the high-speed and broad-band network (HBN) in Japan. System configuration of a video conference system, a video transmission system, a high-speed digital circuit system, and so on, are introduced. Fundamental technologies to realize HBN, 1) switching technologies to handle broad bit-rate class transmission, 2) high-capacity transmission and high-speed digital terminal technology, 3) economical fiber optic subscriber loop technology, and 4) high-performance video codec technology, are discussed. Based on the above discussion, configuration of HBN is proposed.     

Services Integration and Multiplexing for Broad-Band Communication Systems

In broad-band communication networks, a number of services are simultaneously available to the subscriber. The issues of service integration and multiplexing techniques, and their impact on network topologies, are addressed in this paper. Alternative realizations of broadband networks, together with necessary electrical and optical components, are discussed. A comparison between the different alternatives is also made.     

Trends in U.S. Broad-Band Fiber Optic Transmission Systems

Fiber optic media are rapidly penetrating the telecommunications network. They are used as undersea and terrestial trunk lines, central-office loops, optical data links, and will eventually be included within the distribution plant which connects directly into individual premises. The rapid implementation of lightwave systems is occurring because the high bandwidths and low losses of optical fibers enable broad-band communication services to be provided between widely spaced repeaters and also allows users to upgrade currently installed systems to meet future needs. This paper will describe current applications and show how future trends will depend upon the continuing evolution of lightwave components and optical fiber designs.     

Main Effect of Mutual Interference in Radio Communication Systems Using Broad-Band Transmitters

Present-day radio communication systems employing antijam techniques, such as frequency hopping or spread spectrum, require that the transmitter final stage be a broad-band solid-state device. An analysis of such radio communication systems has shown that these systems suffer from the effects of intermodulation (IM) products generated within the transmitters, especially under collocation situations. A qualitative analysis of the transmitter IM-product interference sources is followed by the development of a computational method for obtaining their disturbing effects on a VHF/FM radio system operating under severe tactical collocation scenarios. The computed results for other mutual interference sources upon the system are also presented. The numerical results of the developed computer printout are discussed and conclusions presented, which contribute to obtaining a clearer insight into the mutual-interference sources within the system, especially from the transmitter IM disturbances.     

Interactive Broad-Band Dialogue Systems in the Integrated Services Digital Network (ISDN)

In the integrated services digital network of the future, Which will also have broad-band capacity, it will be possible to offer information services with multimedia presentation (e.g., with support of audiovisual material). For easy use, dialogue structures must be developed which lower the barrier of access for casual users. Offering information in a variety of applications at any place, a technical system consisting of different types of storage devices, operating Systems, and terminals, connected by a narrow- and broad-band switching and transmission system, must be available.     

Broad-Band Quarter-Wave Plates

Analytical expressions are given for the propagation constant for the two orthogonal dominant modes in a square waveguide loaded with a centered slab of dielectric. These are combined to find the differential phase shift in a loaded section. Solutions of these equations are given for polystyrene which enables one to design broad-band quarter wave plates. The problem of transforming from unloaded to loaded guide is discussed and two solutions are given and another suggested. Experimental results are given and it is found that the work in square guide carries over to circular guide almost intact. It is shown that quarter-wave plates may easily be designed to cover a normal waveguide bandwidth.     

Broad-Band Directional Couplers

It is shown how to connect two identical hybrids to obtain a directional coupler of arbitrary power division that operates over a broader band than that of the components. The broad-banding technique is possible with a certain kind of hybrid that includes Riblet couplers, multihole hybrids, coaxial hybrids and semioptical hybrids, but excludes T hybrids and ring hybrids. Riblet couplers have a geometry particularly adaptable to the broad-banding technique. Where the balance of one of these couplers is better than 1 db, the balance of the broad-band hybrid can be made better than 0.16 db. The broad-banding technique is particularly effective in the case of the 100 per cent transfer directional coupler type of circuit used for band separation filters and RADAR duplexers. In the semioptical waveguide band-splitting filters the bandwidth can be increased from about one to about four octaves (35-75 kMc to 35-580 kMc).     

Broad-Band Balanced Duplexers

Balanced duplexer circuits are described and a comparison is made between the two principal configurations employing gaseous switching devices. The balanced tr duplexer is limited in power-handling ability, while the balanced atr duplexer has slightly greater received-signal insertion loss. An analysis is made of the reflecting properties of an atr array, and the practical upper limit of the number of array elements is determined.     

A Broad-Band Microwave Circulator

The discovery of a simple, low loss way to hold Faraday rotation constant over a broad-band (coupled with the development of wide-band, high return loss, circular-to-rectangular waveguide transformers, and polarization couplers) has made it possible to design and build a high quality circulator for use in the 10.7 kmc to 11.7 kmc band. The essential characteristics of the described unit include a more than 30-db return loss at each terminal, an isolation of 30 db or greater between "isolated" terminals, and a 0.35-db insertion loss between transmission terminals.     

Broad-Band Diode Phase Shifters

Design figures are presented for four types of diode phase shifters: switched line, reflection, loaded line, and a new type using lumped-element high-pass and low-pass circuits. Comparison of their bandwidths shows that most of them can work over an octave bandwidth.     

Broad-Band TEM Diode Limiting

The bandwidths of two types of limiters operating below diode resonance and one type of limiter operating at diode resonance are calculated. A 2.5-Gc base-band limiter was made providing a low power insertion loss of less than 1 db, a limiting threshold of 10 mw, and a high power isolation of greater than 20 db. A 0.9-to 1.3-Gc matched limiter was made having a VSWR of less than 1.2 for all power levels. The burnout power of these two limiters was calculated to be about 10 watts incident CW power or 1500 watt-microsecond incident pulse energy. Using the diode resonance the calculations indicate that it is possible to make a 5-Gc limiter with 15 per cent bandwidth, less than 1-db low power insertion loss, a limiting level of 10 mw, and greater than 20-db isolation at high power. The bandwidths derived for diode limiting are equally applicable to switching.     

Broad-Band Personal Computer LAN's

Broad-band technology provides several advantages for personal computer local area networks (PC LAN's) including mature readily available transmission technology, large total bandwidth, support for multiple services, and cost-effective expansion from very small to very large systems. This paper presents an overview of basic broad-band technology, hardware, software, and protocols needed for PC LAN's. Gateways and network management are also considered. Recent PC LAN products are compared, with a more detailed case study of the PC LAN developed by IBM and Sytek.     

Broad-Band and Narrow-Band Measurements

EMC specifications consider two kinds of signals (broad band and narrow band). Special care is to be taken to determine the nature of the signal if meaningful measurements are desired. Tests specified in MIL-STD-462 and in other EMC specifications to decide if there are narrow-band or broad-band emissions are not conclusive, and many times it is difficult to make a decision about the nature of the signal. The decision is less difficult to make when bandwidth effects are understood. This paper tries to show the implications of performing EMC measurements using different receiver bandwidths. It appears that broad-band measurements are valid only in the special case in which the signal has a continuous flat frequency spectrum; in the other cases their meaning is rather questionable. In the conclusion some remarks are made in order to clarify this difficult situation.     

N-Way TEM-Mode Broad-Band Power Dividers

An integrative graphical method of designing a broadband TEM-mode power divider of N output ports is presented. Each branch of the divider's circuit consists of cascaded transmission-line segments, and the corresponding segments of each branch are connected by resistors to a common junction. These resistors absorb the reflected signals due to mismatch at any of the output ports; they are therefore isolated from one another. The symmetry of this circuit permits the use of the method of even- and odd-mode excitations at the output ports. It was found that the even-mode circuit is the same as for a stepped-impedance transformer, which is well known. The odd-mode circuit lends itself to the determination of the isolation resistors using the iterative graphical procedure on a Smith chart. Numerical values of the isolation conductance for dividers of bandwidths up to 10:1, the maximum input VSWR, and the minimum isolation among the output ports are given.