DOI:10.1049/pi-b-1.1955.0002

出版商:IEE    

年代:1955

数据来源: IET

摘要:

The properties of an artificial dielectric at centimetre wavelengths are compared with those of a solid material, and the possible definitions of the refractive index and the wave impedance are examined. It is concluded that the most appropriate definition of the latter is in terms of the reflection coefficient at an interface between the artificial dielectric and free space. The reactive fields which are set up near such an interface are discussed qualitatively, and a number of ways in which they may be represented are given. The paper concludes with suggestions for further applications of artificial dielectrics.

DOI:10.1049/pi-b-1.1955.0003

出版商:IEE    

年代:1955

数据来源: IET

摘要:

A parallel-plate transmission line has been developed for wavelengths between 8 and 11 cm and has been used for an examination of the properties of artificial dielectrics under conditions which approximate closely to those existing in free space. An experimental method by which the effective electrical length of dielectric samples can be determined has been shown to give reliable results. Particular attention has been paid to the occurrence of dispersion and a distinction is drawn between two forms of this. The first arises from the resonance of the elements from which the dielectric is constructed and is called “dipolar dispersion”because of the similarity to the corresponding behaviour of solid dielectrics. The second depends primarily on the spacings between the conducting elements and is referred to as “cavity dispersion. ” Experimental results are given for both types of dispersion.

DOI:10.1049/pi-b-1.1955.0004

出版商:IEE    

年代:1955

数据来源: IET

摘要:

This paper describes measurements at centimetre wavelengths (8.0–11.0cm) on a system representing a semi-infinite array of infinitely thin, perfectly conducting, metallic plates. The purpose is to illustrate a general experimental method of determining the properties of such artificial media. The parallel-plate system was chosen since, in addition to exhibiting the interface phenomena peculiar to artificial media, it is the only one for which a rigorous solution is known. The measurements were made using a parallel-strip transmission-line1specially developed for the study of two-dimensional structures which are non-uniform transverse to the direction of propagation.

DOI:10.1049/pi-b-1.1955.0005

出版商:IEE    

年代:1955

数据来源: IET

摘要:

The methods available for the calculation of the interaction field of an array of dipoles are discussed with reference to an artificial dielectric formed from a tetragonal array of conducting discs. A modified method is described and used to derive a formula for the relative permittivity, valid when the discs are not too closely spaced. For closely packed discs, the fields due to higher-order multipoles become important and a second formula for the relative permittivity is obtained for this case. Comparison with experimental values already obtained shows that the two formulae together enable the calculation of the relative permittivity over the whole range of spacings likely to be used in practice to be made.

DOI:10.1049/pi-b-1.1955.0006

出版商:IEE    

年代:1955

数据来源: IET

摘要:

Widespread v.h.f. continuous signal-strength measurements made in tropical and Mediterranean regions over the last four years have exemplified and thrown into relief many of the well-known mechanisms of tropospheric propagation. Although these mechanisms are broadly familiar to many engineers and physicists, the practical magnitudes, as exemplified throughout the paper, are perhaps less widely appreciated despite their great importance to the communication engineer.It is the purpose of the paper to present and analyse new v.h.f. data from the sources indicated, so as to show (a) that observed v.h.f. signal patterns are consistent with tropospheric structures known commonly to occur, and (b) that sufficient information is now available to enable the communication engineer to forecast to a useful accuracy the statistical behaviour of projected v.h.f. radio paths in certain parts of the world.

DOI:10.1049/pi-b-1.1955.0008

出版商:IEE    

年代:1955

数据来源: IET

摘要:

The paper describes an investigation of the noise generated in crystals and in ceramic forms of barium titanate when subjected to electric stress, as a function of the stress and of temperature above and below the Curie point of the material. The primary purpose of the work was to establish the existence of a ferro-electric Barkhausen effect associated with the domain structure. The results obtained on crystals have permitted an estimate of the effective volume of the individual domains, and this is compared with a previously published value. The ceramic specimens exhibited considerable additional noise of different origin. The characteristics of this noise have been studied, but its satisfactory elucidation will require much further investigation.

DOI:10.1049/pi-b-1.1955.0009

出版商:IEE    

年代:1955

数据来源: IET

摘要:

The paper contains a short survey of the principles of the successive- detection-type logarithmic receiver for pulsed radar, followed by a detailed description of its video problems. A new detection arrange ment is described, and a mathematical analysis of its operation under practical conditions is given. A video amplifier including a differentiat ing circuit for signals of large dynamic range with negligible overshoot is described. Conclusions are drawn for the practical application of the logarithmic receiver with various indicators.

DOI:10.1049/pi-b-1.1955.0011

出版商:IEE    

年代:1955

数据来源: IET

摘要:

The propagation in curved and twisted rectangular waveguides is investigated by putting the wave equation in a form in which the co-ordinates in a waveguide cross-section are also the independent variables in the differential equation. The wavelength is found for the E-curved and H-curved guides, and for twisted guides. In the latter case there is a degeneracy when the guide sides become equal. Curves are presented for the correction to the wavelength in a straight guide caused by the bending or twisting.

DOI:10.1049/pi-b-1.1955.0013

出版商:IEE    

年代:1955

数据来源: IET

摘要:

Experiments have been made on the characteristics of magnetron oscillators at anode voltages from zero to the value at which the oscillations start. In particular, the noise in the anode current was investigated. Discrete peaks of noise were found in the spectrum, and the frequency at which they occurred varied in a regular manner with anode voltage and magnetic field strength. A qualitative explanation of these peaks is given, and the implication of these results on the mechanism of build-up of oscillations and the selection of modes of oscillation is discussed.

DOI:10.1049/pi-b-1.1955.0014

出版商:IEE    

年代:1955

数据来源: IET