摘要:

A method for calculating the vertical radiation pattern of an h.f. curtain array erected on a flat hill or plateau is described. Computations showing how this pattern depends on the steepness of the side of the plateau and on the distance of the array from its edge are discussed.

DOI:10.1049/piee.1964.0078

出版商:IEE    

年代:1964

数据来源: IET

摘要:

The paper is concerned with the field inside a cylindrical shell, having a central core, surrounded by concentric rings. Such a configuration is found in electronic tubes, circuit breakers, waveguides and transmission lines.The potential functions are derived, subject to the boundary conditions of the problem. For mathematical purposes the actual rings are replaced by flat cylindrical rings whose width is allowed to tend to zero. Then, from the equipotential surfaces surrounding these, one can be chosen to represent the rings.The solutions are in the form of infinite series, and a computer has to be used to evaluate them. The series are modified for computational purposes to accelerate convergence. Calculations were carried out on a large digital computer and some results of the calculations are presented in the paper.The potential derived in this paper does not appear to have been considered before. The numerical solutions, although complex, can be obtained conveniently and inexpensively by computer and can be used in the design of equipment.

DOI:10.1049/piee.1964.0079

出版商:IEE    

年代:1964

数据来源: IET

摘要:

Insertion-loss measurements over the frequency band from 28 to 39 Gc/s have been made on a number of curved waveguide structures of circular cross-section. These included a waveguide periodically loaded with both tapered and parallel-sided dielectric discs placed transversely, in addition to longitudinally and circumferentially corrugated waveguide. It was found that the inhomogeneous anisotropic dielectric loading was difficult to fabricate accurately. Dielectric losses limit the usefulness of this method. Longitudinal corrugations of the wall of the tube were used to provide an anisotropic surface reactance and so break the TE01-TM11mode degeneracy. It was found, unfortunately, that the attenuation coefficient of extruded waveguide of this kind in straight lengths was excessive. Circumferentially corrugated waveguide was also used to remove the TE01-TM11mode degeneracy with much more success. Provided that the waveguide is not too highly overmoded, such a structure gives a method of negotiating a sharp bend with low loss.

DOI:10.1049/piee.1964.0080

出版商:IEE    

年代:1964

数据来源: IET

摘要:

An analysis is made of the propagation and diffraction of electromagnetic waves in regions with uniaxial anisotropy, with special emphasis on the fields excited by arbitrarily prescribed sources. Two classes of problems are considered. In the first, the permittivity and permeability may both be anisotropic and may vary in the direction of the optic axisz; in addition, the cross-section transverse tozmay be wholly or partially bounded by infinite, perfectly conducting, cylindrical surfaces of arbitrary cross-section, oriented parallel toz. It is shown that the fields may be decomposed into E and H modes relative to the direction of the optic axis, that the transverse dependence of a typical mode is as in an isotropically filled region, but that the anisotropy affects the longitudinal-propagation characteristics. Alternative formulations for the fields are given in terms of modal expansions, scalar potentials, and dyadic Green's functions. For media with piecewise constant properties, one may employ a co-ordinate scaling transformation which relates the given problem to similar ones in an isotropic region. In the second class of problems, the medium has constant anisotropic permittivity, and a cylindrical obstacle with arbitrary surface impedance is oriented perpendicular to the optic axis; the fields are now required to have no variation along the direction parallel to the surface. By co-ordinate scaling, one may again find an equivalent isotropic scattering problem in which, however, the obstacle contour is distorted. Applications of these procedures are given in Part 2 of the paper.

DOI:10.1049/piee.1964.0081

出版商:IEE    

年代:1964

数据来源: IET

摘要:

The theory presented in Part 1 of the paper is applied to various problems. To illustrate the general procedure, formal solutions are constructed for a number of specific scattering configurations excited by a transverse electric dipole. Several simpler cases are then analysed in detail to provide an insight into the mechanism of radiation and diffraction in a medium with constant anisotropic permittivity; the obstacles considered at this time include infinite-plane surfaces with zero and nonzero surface impedance, and a perfectly conducting halfplane. A ray-optical interpretation of the field solutions is given, and certain observations are made which may be expected to hold also under more general conditions.

DOI:10.1049/piee.1964.0082

出版商:IEE    

年代:1964

数据来源: IET

摘要:

The paper reports measurements of properties of corrugated waveguide, used in linear accelerators, as a function of iris spacing. Measurements were made of series impedance, group velocity and attenuation. Derived shunt impedance is compared with theoretical estimates. The effect on the design of accelerators is considered.

DOI:10.1049/piee.1964.0083

出版商:IEE    

年代:1964

数据来源: IET

摘要:

An analysis is made of several possible sources of loss which can lead to a degradation in the specification of theQfactor of the semiconductor region of a varactor diode. These sources may arise either within the diode cartridge or in the measuring system. The effects are illustrated in relation to a hypothetical diode having a cutoff frequency of about 40 Gc/s, and it is shown that care must be taken in interpreting data obtained experimentally on real diodes. Some representative experimental data are presented.

DOI:10.1049/piee.1964.0084

出版商:IEE    

年代:1964

数据来源: IET

摘要:

Distortion in transistor amplifiers is a very complex problem not amenable to easy solution. In this paper, an equation is found for the complete collector characteristic of a planar transistor which permits calculation of l.f. distortion when operating in each of the nonlinear regions, i.e. saturation, central and breakdown regions. Distortion due to the nonlinearity of input impedance is also calculated. Means of cancelling distortion are shown. Very good experimental verification is observed.Although the theory presented is valid only at low frequencies, the transistors used were v.h.f. types with short-circuit current gain-bandwidth products between 80 and 400 Mc/s. For reasons discussed in the paper, the results should be valid up to approximately the 1–5 Mc/s region.

DOI:10.1049/piee.1964.0085

出版商:IEE    

年代:1964

数据来源: IET

摘要:

Subjective tests of pictures impaired by distortion and noise provide basic data for the design of television broadcasting systems but their complex nature is a source of difficulty. The results are affected by the many arbitrary factors involved in choosing such features as the type of psychometric test, the class of observers, and the test pictures and viewing conditions. Because these tests are inevitably costly and time consuming, it is the more regrettable that different workers have generally chosen different methods, yielding results that cannot be compared satisfactorily.As a possible basis for some degree of standardisation, a general-purpose quality-grading method is proposed. This is of the type, suitable for nonexpert observers, in which impaired pictures are presented in random sequence and the observers give their opinions in terms of a 5 grade scale of quality. Also described are statistical procedures for analysing the primary data and methods of presenting the results.

DOI:10.1049/piee.1964.0086

出版商:IEE    

年代:1964

数据来源: IET

摘要:

The paper deals with the theory of compressors and expanders in which the gain is adjusted automatically at syllabic rate and follows the envelope of the signal. It is shown that, provided that the compressor and expander are ideally complementary, there will be no overall waveform distortion in the expander output if the circuit connecting them is distortionless over the frequency band occupied by the line signal. Fundamentally this must be wider than that of the uncompressed input signal, but with telephone compandors having the parameter values normally adopted, the effect of this inflation of the frequency band is negligible. Expressions are derived for the transient response and distortion products of the line signal, and the effect of departures from the above ideal conditions on the overall distortion is investigated.Complex compressors and expanders incorporating more than one variable-loss device are also analysed, and it is shown that, within a certain class, all cases can be reduced to an equivalent simple compressor and expander.Special characteristics are obtained with more elaborate compandors not falling in this class, and some examples and possible applications are discussed.

DOI:10.1049/piee.1964.0087

出版商:IEE    

年代:1964

数据来源: IET