摘要:

A general analysis of circular wire loops with arbitrary electromagnetic excitation and admittance loading is given. The analysis is made in terms of generalised network parameters and is equivalent to previous analyses of particular problems. Some important special cases of the general theory are circular-loop antennas, loaded-loop antennas, circular-loop scatterers and loaded circular-loop scatterers. A number of new computations of radiation and scattering patterns are given to illustrate the general behaviour of wire loops.

DOI:10.1049/piee.1968.0011

出版商:IEE    

年代:1968

数据来源: IET

摘要:

The paper describes an experimental 16-element circular array and associated receiving system which is capable of forming a fan-beam directional pattern and electronically rotating this pattern through 360°. The receiver operates at a frequency of 427 MHz and a beam rotation rate of 400kHz. The system is designed to study the possible application of this technique to a 360° within-pulse scanning radar. Studies are made of the phase- and frequency-stability requirements of parts of the receiving system necessary to avoid distortion of the rotating directional pattern. Satisfactory results are obtained from the experimental receiver which employs a directional pattern in the form of a J0(x) function having an 8 dB sidelobe level; proposals are discussed for extending the system to handle patterns with lower sidelobe levels.

DOI:10.1049/piee.1968.0012

出版商:IEE    

年代:1968

数据来源: IET

摘要:

A computer study was made of the spillover, crosspolarisation and illumination efficiency of paraboloids of various focal-length/paraboloid-diameter (F/D) ratios, fed by rectangular, square and circular wave-guides in their lowest-order modes. The feed radiation patterns used were those derived by simple diffraction theory from the incident waveguide-mode field distribution. The approximations made in this derivation give unnaturally low spillovers for very small aperture feeds, and thus favour shortF/Dsystems, which would use such feeds. The feed dimensions were optimised to give a maximum figure of merit (gain/total noise temperature) for each combination of feed, receiver noise temperature andF/Dratio. Some of the optimum horn dimensions and resulting illumination tapers, excess aerial noise temperatures, gain efficiencies and figures of merit produced by the computations are presented. The results show, among other things, that the figure of merit of aF/D-ratio system. about 0.8dB less than that of a large-F/D-ratio system They also show that, if the system has a low receiver temperature, the feed dimensions should be larger than conventional design procedures indicate, to give up to 3dB more edge-illumination taper

DOI:10.1049/piee.1968.0013

出版商:IEE    

年代:1968

数据来源: IET

摘要:

In order to investigate the reduction of aerial noise from a small dish with its mainbeam at a low elevation, a 112cm-diameter circular symmetric paraboloid was mounted with a 45° flat plate. The combination was fed so that when the mainbeam was horizontal the feed spillover was predominantly upward. A Dicke-type radiometer is described with synchronously switched i.f. attenuators and a resolution of 10deg K. This was used to investigate the aerial noise against mainbeam elevation angle at 9.6GHz of the dish plus the 45° plate. The aerial noise temperature showed a broad minimum around 30° elevation as expected. The possibility of trading dish size for cryogenic complexity is discussed.

DOI:10.1049/piee.1968.0014

出版商:IEE    

年代:1968

数据来源: IET

摘要:

The paper deals with reradiation from the interior of cylindrical conducting structures of finite length and arbitrary termination. Expressions are developed for far fields at points in the principal plane. For rectangular cross-sections this plane is one containing a broad side of the structure, whereas for circular cross-sections it is a plane containing the longitudinal axis of the structure. Incident plane waves having the propagation vector parallel to the principal plane and polarised either vertically or horizontally with respect to the principal plane are considered. The method of solution involves use of normal-mode techniques in conjunction with the Stratton-Chu integral.Comparisons of computer-calculated theoretical data and measured data were made for illumination of rectangular and circular structures. The theoretical and experimental data, which were for zero bistatic angle and short-circuit terminations of the structures, show remarkably good agreement. For aspect angles of less than about 60°, the return from the interior is dominant, while for larger aspect angles the return from the outer surface masks the interior return. The theory is also valid for nonzero bistatic angles.

DOI:10.1049/piee.1968.0015

出版商:IEE    

年代:1968

数据来源: IET

DOI:10.1049/piee.1968.0016

出版商:IEE    

年代:1968

数据来源: IET

DOI:10.1049/piee.1968.0017

出版商:IEE    

年代:1968

数据来源: IET

摘要:

The paper presents a case for correlating transient response with transient-stability limit of power systems. An elementary power system provided with fast acting voltage regulators using various feedback signals is analysed in detail. The effect of varying regulator gains on transient response is investigated with the help of gain-locus diagrams on a gain plane. The Runge-Kutta method with fourth-order approximation is used to determine the transient-stability limit of the same system for various gains. The gains which give good transient response are compared with those which give high stability limit. Efforts have thus been made to see whether it is possible to correlate good transient response with high transient-stability limit.

DOI:10.1049/piee.1968.0018

出版商:IEE    

年代:1968

数据来源: IET

摘要:

Loss-minimisation techniques applied to load-flow analysis form an effective means of obtaining a desirable voltage solution. In addition, the method offers improvement in convergence, which is especially important for networks which give rise to ill conditioned equations. The described method uses the nodal-impedance matrix and minimises that part of the total real-power losses which depends on the generator reactive-power input and on the transformer tap settings. The reactive-power input and voltages at the generator busbars, together with transformer tap settings, are calculated automatically by the program according to the criterion of minimum loss. In contrast to the methods previously employed, the off-nominal turns ratio of transformers is represented by a superimposed branch current and an injected nodal current. The transformers may be in-phase or phase-shifting. The paper shows how the minimisation procedures may be incorporated into the iterative process of a general load-flow program. A comparison with other methods is given by means of a sample-system study.

DOI:10.1049/piee.1968.0019

出版商:IEE    

年代:1968

数据来源: IET

摘要:

The paper is a contribution to work on the problem of synthetic testing under short-line fault conditions. Traditional ‘current-injection’ circuits for terminal faults have already been extended to the case of the short-line fault by various authors. The circuit which is proposed in the paper accurately reproduces an actual short-line fault occurring in a network under most general conditions. The test circuit is described, and a survey is given on a complete series of tests carried out at CESI Laboratories, with the object of comparing synthetic and direct methods of testing. Test results have shown that the synthetic circuit adopted complies with the requirements for equivalence to the corresponding direct circuit. A confirmation of the results is given both by statistical analysis and by current-zero measurements, which allow a better insight into the interaction between test breaker and test circuit.

DOI:10.1049/piee.1968.0021

出版商:IEE    

年代:1968

数据来源: IET