摘要:

The field of a plane wave diffracted by an obstacle equivalent to a semi-infinite screen has been studied close to the diffracting edge. The experimental intensity and phase values of the field associated with a thin, highly conducting sheet are compared with Sommerfeld's rigorous solution for an infinitely thin, perfectly conducting half-plane. Further experimental values show the effect on the diffraction pattern of increasing the thickness and decreasing the conductivity of the sheet.

DOI:10.1049/pi-3.1952.0062

出版商:IEE    

年代:1952

数据来源: IET

摘要:

Long-term measurements of microwave transmission over a 39-mile optical path have shown fading too deep to be easily accounted for by simple theory.It is concluded from experimental evidence that both scattering from turbulence and movements of the interference pattern contribute to the fading.

DOI:10.1049/pi-3.1952.0063

出版商:IEE    

年代:1952

数据来源: IET

摘要:

The paper deals with the general theory and design of microwave radio links as transmission systems.After a brief introduction, the questions of propagation and atmospheric phenomena are outlined in so far as they affect the design of a link. There is then given a treatment of a frequency-modulated multichannel radio link in which thermal and intermodulation noise are calculated in terms of the system parameters. This work makes possible the determination of the deviation for minimum total noise. In a particular case of practical importance a merit factor of a link is defined. The problem of pre-emphasis is outlined, and finally the required bandwidth is determined.The problems of a television link are discussed.In order to present a clear picture of the overall action, problems of a statistical character have been omitted. In particular, all occupied channels are assumed to have signals of equal amplitude. It follows that more work needs to be done to obtain design data for systems in which the statistical effects are important.

DOI:10.1049/pi-3.1952.0064

出版商:IEE    

年代:1952

数据来源: IET

摘要:

The paper describes the circuit problems in wide-band microwave communication links and is illustrated by reference to the development of links operating at frequencies around 4 000 Mc/s for 180-channel telephony and for television.Modulating and demodulating circuits with very linear characteristics, and i.f. amplifiers with uniform time-delay are described, together with the necessary techniques required to assess their performances.The optimum design for a broad-band low-noise i.f. amplifier is shown to consist of cascaded earthed-grid triodes.Automatic-frequency-control systems, the special video problems of television, and high-level intermediate-frequency/microwave mixers are described.

DOI:10.1049/pi-3.1952.0065

出版商:IEE    

年代:1952

数据来源: IET

摘要:

The paper describes theoretical and practical work carried out in the development of the microwave parts of links to work in the band 7.15–8.33 cm (3 600–4 200 Mc/s). Special microwave techniques are described and illustrated by particular components, with reference to performance and matching over a broad frequency-band.The antenna system chosen for the link is based on the parabolic mirror, and the special developments needed to ensure satisfactory performance are outlined.A description of a precision signal-generator for use in measurement and development is included.

DOI:10.1049/pi-3.1952.0066

出版商:IEE    

年代:1952

数据来源: IET

摘要:

Compared with conventional means the time-series method offers a great reduction of the computing work involved in solving many of the practical waveform or “transient” problems of cascade-connected linear 4-terminal networks. The basis is that any waveform arising from a system of limited bandwidth can be represented exactly by a time series, or sequence of equidistant ordinates of the waveform, having an interval equal to half the reciprocal of the bandwidth.It is pointed out that the advantages of the method can be exploited, not only when a limitation of bandwidth is a physical property of a given system, but also when a limitation arises merely from a restriction of interest in the performance of the system to a given range of frequency. Such a restriction can be applied to a waveform by an arithmetical filtering process without recourse to spectrum analysis.An elementary description is given of practical procedures for dealing with time series, including serial multiplication (equivalent to convolution), serial division, differentiation, integration, filtration and an interpolation method for reconstituting a waveform from its time series. These are illustrated by examples chosen from the field of television transmission.

DOI:10.1049/pi-3.1952.0069

出版商:IEE    

年代:1952

数据来源: IET

摘要:

Vacuum capacitors are particularly suitable for high-frequency high-voltage operation in airborne radio equipment. Capacitors developed to fulfil requirements of a specific nature revealed a number of interesting effects which are explained qualitatively, and which have considerable influence on the capacitor design. The results are of general application and tests on the capacitors developed show that their performance is very satisfactory. It is believed that, for the requirements specified, no other type of capacitor has a comparable performance.

DOI:10.1049/pi-3.1952.0070

出版商:IEE    

年代:1952

数据来源: IET

DOI:10.1049/pi-3.1952.0071

出版商:IEE    

年代:1952

数据来源: IET

DOI:10.1049/pi-3.1952.0072

出版商:IEE    

年代:1952

数据来源: IET

DOI:10.1049/pi-3.1952.0073

出版商:IEE    

年代:1952

数据来源: IET