摘要:

Some general rules concerning the simulation of floating impedances using immittance-convertor circuits are introduced, and used to derive RC-active circuits for simulating floating inductances in series or in parallel with resistances. These circuits require only two operational amplifiers to produce a single floating lossy inductance. Practical examples are given of these methods applied to the synthesis of economical low-sensitivity active filters.

DOI:10.1049/piee.1974.0014

出版商:IEE    

年代:1974

数据来源: IET

摘要:

An original approach for the analysis of switching-control circuits is described. A new transformation method is introduced to simplify the calculations. This method is especially suitable for switching that is not synchronised with the frequency of the mains supply. Practical uses of such circuits are described in a companion paper.

DOI:10.1049/piee.1974.0015

出版商:IEE    

年代:1974

数据来源: IET

摘要:

An equation is obtained which gives the derivatives of the graph transfer functions with respect to a parameter of interest when the parameter is the transmittance of many branches and when the graph transfer functions are in the bilinear form of the parameter. This equation is useful for evaluating the sensivity functions of active RLC network functions by variation of the passive or active parameters of interest.

DOI:10.1049/piee.1974.0016

出版商:IEE    

年代:1974

数据来源: IET

摘要:

Interest has recently been shown in the use of d.s.b. diminished carrier for the mobile land radio service. Difficulties in the design of a suitable transmitter employing a conventional exciter-amplifier technique are described. A method that overcomes these difficulties is discussed, and a suitable design presented. A transmitter capable of delivering 38 W peak envelope power with an 18 V supply has been built. The spurious responses close to the wanted sidebands, were almost one order of magnitude lower than can be achieved with the conventional exciter/linear-amplifier technique. Power efficiency was also greatly improved.

DOI:10.1049/piee.1974.0017

出版商:IEE    

年代:1974

数据来源: IET

摘要:

Extensive experimental and theoretical results are presented for thin cylindrical antennas with lumped capacitive loadings along their length. The capacitive loading is in the form of a narrow gap between two sections of the antenna. Experimental curves for the gap capacitance against gapwidth are presented, and these values are used in calculating current distribution along the antenna and its admittance. The agreement between experimental and theoretical results indicates that, with the construction proposed, it is possible to make a capacitively loaded antenna that has properties quite close to those predicted by the theory.

DOI:10.1049/piee.1974.0018

出版商:IEE    

年代:1974

数据来源: IET

摘要:

A theory of signal quantisation is developed from first principles that describes quantisation using analogue-modulation techniques. The nonlinearities, which are fundamental to digital source encoding, are expressed by two sampling processes, which directly lead to solutions in terms of amplitude and phase modulation. The analysis derives a related set of mathematical models that deter mini stically describe the input/output transfer characteristics of uniform and nonuniform p.c.m., uniform delta modulation (d.m.) and uniform d.p.c.m.

DOI:10.1049/piee.1974.0019

出版商:IEE    

年代:1974

数据来源: IET

摘要:

The braking torque, that acts on a nonmagnetic metal disc of radius a rotating at constant speed in a nonuniform magnetic field, is determined. Solutions are obtained by means of an electromagnetic analogy and by direct integration of the relevant differential equation. Comparison with experimental results is provided.

DOI:10.1049/piee.1974.0021

出版商:IEE    

年代:1974

数据来源: IET

摘要:

A dynamic model to describe the nonlinear surge-current characteristics of several concentrated earths has been developed. The model accurately accounts for the surge behaviour of these earths on a time-to-time basis, in soils with resistivities ranging from 5000 Ω cm to 31 000 Ω cm. This results in a significant improvement over the previous methods used to describe them. The use of the new model for studies of concentrated earths at high lightning currents reveals that greater surge reduction factors than was previously assumed can be expected. This study serves to overcome previous difficulties in having to extrapolate values from meagre experimental results.

DOI:10.1049/piee.1974.0022

出版商:IEE    

年代:1974

数据来源: IET

摘要:

The propagation characteristics of various surges on a 500 kV untransposed transmission line in horizontal array are described, and the test data are compared with computer results. Interesting phenomena are observed at the wavefronts of surge waves in the field test, and these are substantiated both analytically and by computer calculation.

DOI:10.1049/piee.1974.0023

出版商:IEE    

年代:1974

数据来源: IET

摘要:

A mixed-integer linear programming approach to the planning of electrical-power networks is described. The method is based on an interpretation of fixed-cost transportation-type models, and includes both network security and costs of network losses. Both single-period and multitime-period planning problems are considered. A large general-purpose mathematical programming system is used to obtain solutions using branch-and-bound algorithms, and the practical aspects of organising the problems and controlling the branch-and-bound tree search within a modern m.p.s. package are discussed. Three case studies are presented for illustration: the optimal design of a 132 kV subtransmission system, the optimal time-phased design of the same system over. eight years, and the optimal layout and cable selection for a new housing-estate low-voltage network. The paper concludes by indicating potential further applications of the method for scheduling, for example, new plant at substations.

DOI:10.1049/piee.1974.0024

出版商:IEE    

年代:1974

数据来源: IET