摘要:

The eddy-current anomaly effects in an 0.019 in thick low-silicon sheet steel are investigated and analysed on the basis of the magnetic inhomogeneity arising from ferromagnetic domain structure. This particular steel was chosen because previous experimental work had shown that inherent time-lag effects in the magnetization process were small. However, in such a steel, flux waveform distortion arising from hysteresis phenomena adds to the anomaly effect, and a special experimental technique by which such distortion effects could be eliminated from the analysis was developed. This made it possible to test the steel, focusing attention upon the anomaly effect attributable to the magnetic inhomogeneity. The results obtained are interpreted in terms of a hypothetical domain configuration, and it is concluded that the magnetic inhomogeneity arising from ferromagnetic domain structure does account for the eddy-current anomaly, distortion and time-lag effects being of minor importance.

DOI:10.1049/pi-c.1957.0002

出版商:IEE    

年代:1957

数据来源: IET

摘要:

The frequency pulling of an oscillating magnetron is measured by inserting a reactor in the output feeder, which produces a reflection of constant magnitude but variable in phase; the frequency pulling is usually estimated on the assumption of constant v.s.w.r. in the feeder. In practice, when multiple reflected waves exist in the feeder the v.s.w.r. is not constant, but it is found that the amplitude/phase variation of the resultant reflected wave is such that the locus of the voltage reflection coefficient is a circle in the Smith chart. An idealized equivalent circuit for the magnetron is assumed and the theoretical frequency pulling is estimated. The performance of a typical waveguide system used in magnetron testing is examined with regard to the possible variation in measured frequency pulling.

DOI:10.1049/pi-c.1957.0003

出版商:IEE    

年代:1957

数据来源: IET

摘要:

The method of steepest descents is applied to evaluate the impulse response of a number of identical buffered circuits in cascade. It is shown that exact results may be obtained by analogue computing. Approximate analytical expressions are obtained for various values of time, including the period of build-up. These are tested against two networks for which exact evaluation is possible. A cruder approximation valid near the build-up time is applied to predict suitable parameters for video-frequency compensating networks. These again are checked with known results.

DOI:10.1049/pi-c.1957.0004

出版商:IEE    

年代:1957

数据来源: IET

摘要:

Unwanted modes in cylindrical cavity resonators operating in the H01nmode may be suppressed by inserting a ring of lossy material in a groove cut at the junction between an end wall and the cylindrical wall. This groove does not affect the H01nmode but may suppress the others if the groove dimensions are correctly chosen. An analysis of the effectiveness of this method is given and is confirmed by measurements in the 3 cm band of wavelengths.

DOI:10.1049/pi-c.1957.0005

出版商:IEE    

年代:1957

数据来源: IET

摘要:

Hall effect and radiation pressure are shown to be different manifestations of the same basic phenomenon, and their relationship is deduced for a plane wave transmitted through a slab of material of given electrical characteristics. In particular, the contributions to these effects of both the conduction and displacement components of current in the material are examined, and it is shown that the latter can be a significant supplementary factor at ultra-high frequencies.Both Hall effect and radiation pressure have been used for microwave power measurement, and some aspects of these applications are discussed in the light of the present analysis. To permit a better assessment of the Hall-effect-wattmeter problem, numerical calculations have been made at 4000 Mc/s forn-type germanium and silicon showing that a high-resistivity material is necessary to achieve a satisfactory performance with a transmission type of instrument. Similar computations for polythene predict that a measurable Hall effect arising from displacement current in this material should exist, and it is suggested that observations based on that effect might offer a new approach in further exploration of the properties of dielectrics.

DOI:10.1049/pi-c.1957.0006

出版商:IEE    

年代:1957

数据来源: IET

摘要:

The problem considered is that in which vertically polarized waves are propagated across a single straight-line discontinuity in the electrical properties of a smooth flat earth, the discontinuity being such as might occur at a (rather idealized) coastline. It is further specialized by the assumption that one of the media (e.g. sea) has infinite conductivity, and this is replaced by an infinitely thin, perfectly conducting half-plane lying in the interface of the air and the land medium, the latter now being taken to fill completely the region below the interface.With this model a method of solution is proposed which is a union of ray theory and rigorous diffraction theory. The presence of the land is accounted for by the introduction of a suitable image field and the problem thereby reduced to one in which two fields are incident upon a perfectly conducting sheet situated in free space. The technique is illustrated by application to the case of a three-dimensional plane wave, and this solution forms the basis for the later work.When the transmitter is at a finite distance from the coastline the solution can be obtained by expressing the incident field as an angular spectrum of plane waves the propagation of which has already been studied. This procedure is first applied to the two-dimensional problem of a line source and the results are shown to be in close agreement with previous work on the subject. On examination, however, the solution is found to be made up of the field of the actual transmitter diffracted at the coastline, together with the diffracted field arising from an image transmitter of strength equal to the Fresnel reflection coefficient appropriate to a particular angle of incidence, and this suggests an even more elementary way of tackling the problem. For any type of transmitter all that is now required is the solution of the corresponding Sommerfeld diffraction problem, and with this new approach the case of a point source is treated. The result is almost identical with that found by resolution into plane waves. Moreover, a comparison with the solution for a line source shows that the factor by which the free-space field must be multiplied to give the total field is of the same form for both transmitters, the factor for a point source being obtainable from that for a line source by replacing each two-dimensional distance by the corresponding three-dimensional one. In particular this justifies the application to each radial separately of the formulae for normal incidence on the coastline and enables the analytical difficulties associated with three-dimensional propagation to be avoided.The nature of the field is then studied with particular reference to the rapid changes of intensity and phase just beyond the coastline; the former is generally termed the ‘recovery effect’, whilst the latter gives rise to the phenomenon of coastal refraction. The use of height-gain factors is considered and it is shown that, for sufficiently small elevations of transmitter and receiver, the factors appropriate to homogeneous earths may be applied. Several numerical examples are given.

DOI:10.1049/pi-c.1957.0007

出版商:IEE    

年代:1957

数据来源: IET

摘要:

The behaviour of a trigatron three-electrode spark-gap in air has been investigated and its characteristics obtained with particular reference to its use as a controlled high-voltage switch. It is found that the voltage range over which it may be triggered satisfactorily depends, not only on the polarities of the main gap and triggering voltages, but also on the energy of the discharge. The breakdown time-lag is also determined by these same voltage polarities and also by the time-constant of the trigger discharge circuit.From these characteristics and certain other relevant observations, a theory of the breakdown process in such a spark-gap is suggested, involving the propagation from the trigger of a low-density easilyionized region.Finally, a brief investigation of the successful use of a trigatron in a diverter circuit capable of diverting the discharge energy in a spark-gap subjected to direct and impulse voltages of 300 kV and in a circuit providing accurate ‘chopping’ of impulse voltage waves, is reported.

DOI:10.1049/pi-c.1957.0008

出版商:IEE    

年代:1957

数据来源: IET

摘要:

A theory for the tandem connection of quadripoles is presented, using as basic parameters the operating factor and input and output impedances of a quadripole when operating under reference conditions between arbitrarily chosen source and load impedances. These parameters are termed the reference parameters, and the source and load impedances are called the nominal impedances. Simple extension leads to the reference loss parameters.Operating-loss and input-return-loss formulae are derived for the non-reference operation of a quadripole, and, in conjunction with return-loss formulae obtained for quadripole junctions, are used to determine overall operating-loss characteristics of a transmission system when quadripoles are added or removed. Furthermore, these formulae are used for transmission-system synthesis.A technique is developed which permits convenient and precise calculation of return and operating loss, or alternatively enables calculation of their limits.The formulae derived facilitate the rapid solution of a variety of practical transmission problems, and their application in some instances is illustrated by the inclusion of numerical examples.

DOI:10.1049/pi-c.1957.0009

出版商:IEE    

年代:1957

数据来源: IET

摘要:

The chief cause of erratic results when field gradients are measured in an electrolytic tank by means of closely spaced probes is shown to be variability of the meniscus near the probes. A new form of tank is described in which measurements are made by capillary probes in a plane defined by an insulating surface, thereby eliminating the meniscus effects present when the probes are placed in a free surface.

DOI:10.1049/pi-c.1957.0010

出版商:IEE    

年代:1957

数据来源: IET

摘要:

The effects of interaction across a circular aperture in a plane, perfectly conducting screen are studied by application of the approximate edge-current diffraction theory previously developed,1the interaction terms being found by asymptotic evaluation of the first-order aperture field. Their effect is examined by computing the aperture and axial fields and comparing the results with exact theory. An interaction correction to the geometrical-optics transmission coefficient, which agrees well with rigorous theory except for a monotonic component, is obtained. With an assumed current distribution over the entire screen, an expression is found for the transmission coefficient, neglecting interaction, which exhibits monotonic behaviour at variance with that expected from exact theory. A term with the desired variation is derived empirically.The possibility of extending the method to apertures of more general form is briefly mentioned.

DOI:10.1049/pi-c.1957.0011

出版商:IEE    

年代:1957

数据来源: IET