摘要:

As part of the process of harmonisation of technical standards needed to achieve the Single European Market in 1992, the European Commission has proposed a Directive on EMC. This paper describes the requirements contained within the proposal and, since the proposal will refer to European Standards for technical requirements, a brief outline of the standards-making procedure is included.

DOI:10.1049/ecej:19890010

出版商:IEE    

年代:1989

数据来源: IET

摘要:

Proposals for a European Directive on electromagnetic compatibility are focusing attention on the techniques for measurement of noise and unwanted signal emissions from a wide variety of equipment. Assessment of the immunity of sensitive electronic equipment to electromagnetic disturbances, such as electrostatic discharges and RF transmissions, is equally important. This paper includes an outline description, with reference to the various British and international standards, of most of the EMC measurement techniques which may be applied to any item of electrical equipment.

DOI:10.1049/ecej:19890011

出版商:IEE    

年代:1989

数据来源: IET

摘要:

An elementary reconsideration of first principles in aperture-domain processing of wave phenomena for reception (and, by reciprocity, for transmission) can yield revealing, and in some cases novel, insights into what can or cannot be achieved. The subjects covered here include direction-selective reception, superdirectivity, direction finding, focused near-field reception, circular arrays and circular modes in such arrays, and the new concepts of arrays composed of ‘random symmetrical pairs’, and of real gain in omnidirectional receiving antennas. The ideas are basic to all wave directional analysis and imaging applications, be they electromagnetic or acoustic, in radar or sonar, communications, navigation, surveillance or medical imaging.

DOI:10.1049/ecej:19890012

出版商:IEE    

年代:1989

数据来源: IET

摘要:

Following the rapid growth of land mobile radio, increased attention is being paid to the provision of aircraft passenger telephony services. This paper reviews the requirements for such services and outlines how modern technology will shortly enable worldwide aeronautical telephony to become a reality—via satellite. The current service provisions and enabling technologies are described and an insight provided into an experimental airline passenger telephone system.

DOI:10.1049/ecej:19890013

出版商:IEE    

年代:1989

数据来源: IET

摘要:

Digitised colour images quantised at 24 bits per pel represent a considerable storage requirement. For many applications a coarser quantisation is allowable or even necessary. This paper describes three variations on a method to quantise RGB data at approximately 4 bits per pel. The main criterion in the scheme is that of a minimum perceptual distortion in the reproduced data. The MacAdam chromaticity domain is used as a perceptually metric space in which equal Euclidean distances may be assumed to represent equally perceived colour differences. Histogram and cluster analysis methods are used to quantise the RGB data at 4 bits luminance and 0.75 bits chromaticity. The results appear acceptably close to the originals.

DOI:10.1049/ecej:19890021

出版商:IEE    

年代:1989

数据来源: IET