摘要:

As in so many other branches of electronics, the coming of the transistor has revolutionised broadcast engineering. New devices have made it possible to adopt digital coding for the distribution of television sound and radio programmes to most of the network of transmitters. The small size and low power consumption of the solid-state device has allowed the television camera and its associated equipment to become very much more mobile; this, in turn, has had a profound effect on the methods of television production. Lightweight production units, housed in a single vehicle, allow plays and series to be recorded in natural settings, away from the studio. The ability to store whole television fields in electronic memories of relatively small cost and physical size, has made possible a whole range of new technical processes. One television field can be compared with its predecessor; this is the basis of electronic conversion between the world's television standards. It is also possible to discriminate between random noise and wanted information in the image, because the latter can be correlated from field to field. While broadcasting is under constant technical development, so too are the demands on its services. There is greater emphasis on education and the need for broadcasting schedules to fit patterns of work and leisure. New services must be matched by new receiver designs allowing easy tuning and selection of programme, reliable reception and automatic recording for replay later. Inaudible control signals sent out by the broadcaster will make these possible. New forms of transmission and special services, e.g. a traffic information channel and subtitles for the hard of hearing, offer new opportunities to broadcasters and receiver manufacturers alike.

DOI:10.1049/piee.1979.0001

出版商:IEE    

年代:1979

数据来源: IET

摘要:

The paper presents a review of some recent advances in microwave reflector antennas, and places emphasis on the work of the Electromagnetics Applications Group at Queen Mary College (QMC). After a brief historical review, the following classes of antenna are considered: pencil beam, shaped beam, beam scanning and multiple beam. The operation of these antennas is described in nonmathematical terms and their performance constraints are identified. Many new antennas and feeds are illustrated and their operation discussed. In nearly all cases, they have resulted from innovation coupled with computer-aided design methods. The latter development distinguishes antenna developments of the last decade from those of the past. It is expected that this feature of antenna design will be exploited still more in the future.

DOI:10.1049/piee.1979.0002

出版商:IEE    

年代:1979

数据来源: IET

摘要:

An analysis of the addition of echoes generated by the transmission of a digital signal over a structurally periodic coaxial cable is presented. The p.d.f. of the ensemble of forward propagating echoes is demonstrated to be generally Gaussian, provided that the original data source is random. The frequency dependence of the resulting p.d.f. is also shown to be relatively insignificant for all but a restricted number of cases.

DOI:10.1049/piee.1979.0003

出版商:IEE    

年代:1979

数据来源: IET

摘要:

In this paper we present the analytical results of the computational requirement for the minimum-distance decoding of convolutional codes. By deriving upper bounds for the number of decoding operations required to advance one code segment, we show that many less operations are required than in the case of sequential decoding This implies a significant reduction in the severity of the buffer-overflow problem. Then, we propose several modifications which could further reduce the computational effort required at long back-up distance. Finally we investigate the trade-off between coding-parameters selection and storage requirement as an aid to quantitative decoder design. Examples and future aspects are also presented and discussed.

DOI:10.1049/piee.1979.0004

出版商:IEE    

年代:1979

数据来源: IET

摘要:

A new numerical technique is presented for the analysis of diffraction of horizontally and vertically polarised waves by an array of conducting cylinders with arbitrary elemental cross-section, commonly known as transmission gratings. The method, which is on the finite-element technique, is simple in nature and involves no iterative calculations. Numerical results are obtained for gratings of rectangular and circular elements for both polarisations at arbitrary angles of incidence. These results compare favourably with the experimental and theoretical data available in the literature. They further reveal some of the interesting properties of the transmission gratings. The proposed solution technique is also applicable to a large class of problems in electromagnetics and physics and therefore should be of considerable interest to engineers and physicists.

DOI:10.1049/piee.1979.0005

出版商:IEE    

年代:1979

数据来源: IET

摘要:

Minimal realisations of 1st-orderRCtransfer immittances are derived. The proposed method of realisation works in the following two steps. First it realises an open-circuitRCvoltage-transfer function obtained through the ratio of the specified transfer immittance and a suitably chosenRCdriving-point immittance. Next it restores the location of the pole of the driving-point immittance chosen by scaling/adding a resistor in a suitable manner. It gives balanced realisation for nonminimum phase functions and unbalanced realisation for the remaining functions. In each case the realisation requires one, and only one, grounded capacitor except in one special case.

DOI:10.1049/piee.1979.0006

出版商:IEE    

年代:1979

数据来源: IET

摘要:

Power-supply engineers are required to control the impact of their activities on the consumer, the system and the environment. The integrated transmission system enhances the control of costs of generation and of energy to the consumer. Load is met by the provision of spare generation, but advantage should be taken of systems for load management in the future. European interconnection, with pooled resources, will be beneficial, and a d.c. interconnection with France is being considered using thyristor-valve technology. Effects of faults can be severe. Advances in circuit breakers and protection systems using microprocessors are enabling shorter fault-clearance times to be achieved. More automatic control is leading to a more reliable supply by rapid restoration of circuits, even in extreme weather conditions. Economy in the use of expensive circuit breakers can result in complexity of auxiliary connections, but the computer provides both design and commissioning capability. System control using computer technology is being extended and will be adapted to the provision of a 2-tier hierarchy in the future. Control of environmental impact is achieved by sympathetic siting of substations and route selection for lines. A new line design at 400 kV should reduce the wirescape and provide lighter and smaller towers.

DOI:10.1049/piee.1979.0008

出版商:IEE    

年代:1979

数据来源: IET

摘要:

The paper describes the development of the numerical Fourier transform with exponential sampling. This is called the exponential Fourier transform (e.f.t.). The e.f.t. gives quite a high accuracy and a very long observation time with a small number of samples in comparison with a conventional numerical Fourier transform with equally spaced sampling. Thus, the computational efficiency of the e.f.t. is much higher than the conventional Fourier transform. Various calculated examples using the e.f.t. are given and are compared with the results obtained by the conventional Fourier transform. From the results the superiority of the e.f.t. compared with the conventional Fourier transform becomes clear. The e.f.t. would be very useful to deal with electrical transients with a very wide range of frequency or time.

DOI:10.1049/piee.1979.0009

出版商:IEE    

年代:1979

数据来源: IET

摘要:

The paper presents the results of a digital analysis of a wide set of square and rectangular grounding grids. The diagrams for grid resistances and mesh voltage factors are displayed appropriate for practical design purposes. Simple approximate formulas for both grid parameters considered are also proposed, providing a fair estimation of the parameters.

DOI:10.1049/piee.1979.0010

出版商:IEE    

年代:1979

数据来源: IET

摘要:

The operation and control of power systems depends on adequate metering. To reduce inherent difficulties and metering inaccuracies, modern online control schemes use some form of state estimation. This paper is concerned with economic design of metering pattern to improve the metering performance. The proposed method is based on a fast-decoupled estimator that can be used to design new systems or improve existing ones. The paper includes some practical results of designing and improving existing metering system.

DOI:10.1049/piee.1979.0011

出版商:IEE    

年代:1979

数据来源: IET