摘要:

In 1991 the countries of Western Europe will introduce a new cellular radio system to replace the plethora of different standards currently in place. This initiative provides the European mobile communications industry with a home market of 300 million people, while at the same time giving it a significant technical challenge. This paper discusses the progress towards the standard, outlines the system and describes some of the technical problems now facing the product development teams

DOI:10.1049/ecej:19890004

出版商:IEE    

年代:1989

数据来源: IET

摘要:

Digital technology and VLSI are having a profound effect on the development of television. With the advent of high-definition television, we will see receivers with vastly more digital video signal processing than even the most advanced set available today. But what will we get from all this processing?

DOI:10.1049/ecej:19890005

出版商:IEE    

年代:1989

数据来源: IET

摘要:

The application of intelligent systems is investigated for the automatic tuning of microwave waveguide filters and the alignment of quadrature-amplitude-modulated (QAM) digital microwave radio equipment. The intelligent techniques include conventional rule-based expert systems as well as a machine-learning system which combines techniques from pattern recognition and adaptive signal processing. These approaches are shown to significantly reduce the time and skill required for manual filter alignment and, in addition, they can readily diagnose both type and magnitude of selected faults in the radio communication equipment. This is accomplished via a set of feature data whose parameters are monitored under fault or misalignment conditions, and the deviations from a good pattern are used to adjust the device under test. The selection of appropriate features and alignment of sixcavity 11 GHz waveguide filters and 16-state QAM digital microwave radio-relay-system equipments are discussed.

DOI:10.1049/ecej:19890006

出版商:IEE    

年代:1989

数据来源: IET

摘要:

Proven feedback theory applied to linear and nonlinear microwave active circuits enables designers to predict true stability margins in amplifiers. H.W. Bode's return ratio can always be defined for transistors, and some applications in analysis and design are clarified by examples. Combined with a semigraphical technique, it shows the influence of feedback on reflection properties of singly terminated transistors. Return ratio is a powerful CAD concept for oscillators. The first known combination with nonlinear simulation using the direct method is both effective and accurate, as demonstrated for a nonlinear VCO. Possible extensions to matching and interstage design and to other nonlinear microwave circuits are noted. The current worldwide drive towards more realistic characterisation and modelling of active and passive components and of circuits will provide data from which more accurate assessments of feedback can be achieved using the return ratio concept

DOI:10.1049/ecej:19890007

出版商:IEE    

年代:1989

数据来源: IET

摘要:

Picture-on-the-wall television has long been a dream of display engineers throughout the world. This vision, combined with the enormous growth in applications for electronic displays over recent years, has resulted in major efforts aimed at achieving a cathode-ray tube design which is both flat and thin. Moreover, there is evidence of increasing activity in this field, in spite of the many advances being made with other flat-panel display technologies. This review paper provides an introduction to the wide range of flat-panel CRT designs, and describes some of the leading approaches to the achievement of colour in these displays. Some photographic results are also included

DOI:10.1049/ecej:19890008

出版商:IEE    

年代:1989

数据来源: IET