摘要:

A method is proposed for the analysis of thin cylindrical dipoles with nonzero internal impedance per unit length. Current distribution along the dipole is approximated by a polynomial with complex coefficients. The method is applicable to dipoles with arbitrary internal impedance per unit length (which must, however, be constant along the dipole), but particular attention is devoted to purely resistive antennas, for which experimental data are available. Values of input admittances of purely resistive dipoles, obtained by the proposed method using the 2nd-order, or mostly the 3rd-order, polynomial current distribution, are in excellent agreement with experimental results.

DOI:10.1049/piee.1970.0404

出版商:IEE    

年代:1970

数据来源: IET

摘要:

A theoretical analysis is presented in which the phase pertubations of the sounding signal due to ionospheric propagation are interpreted into a ‘phase-error’ rate. An indication of how this may be used to assess the likely error rate associated with an information channel using that frequency is also given. The paper describes how the sounding technique will be used to control the time at which to change frequency, the best standby frequency and the degree of redundancy required to protect the information. The paper is a sequel to that presented by the authors at the IEE conference on signal-processing methods for radio-telephony, London, May 1970.

DOI:10.1049/piee.1970.0405

出版商:IEE    

年代:1970

数据来源: IET

摘要:

A linear 1-dimensional theory is given for the acoustoelectric oscillator. In this device, a direct current is passed through a plate of piezoelectric material sandwiched between two electrical contacts. Oscillations occur at frequencies near the natural acoustic frequencies of the plate when the ‘round-trip gain’ exceeds unity. All five waves are included in the theory, and the effects of the external load on the growth rate and initial oscillation frequency are computed. The theory provides an explanation for such previously reported phenomena as mode enhancement and mode quenching.

DOI:10.1049/piee.1970.0406

出版商:IEE    

年代:1970

数据来源: IET

摘要:

A theoretical model of the avalanche-diode oscillator, based on Read's analysis is developed. It is shown that, with appropriate circuit constraints, a complex voltage waveform appears across the device terminals and high-efficiency low-frequency oscillations occur. The model is applicable at low current densities and the effects of carrier space charge on the electric-field distribution within the device are neglected in the computations. A switch from transit time to operation at a harmonically related low frequency, with increasing direct-current density and under constant-r.f.-loading conditions, is predicted by this theory. An experimental circuit by which such effects may be investigated is described, and avalanche-diode behaviour in qualitative agreement with the model is observed.

DOI:10.1049/piee.1970.0407

出版商:IEE    

年代:1970

数据来源: IET

摘要:

The paper presents a survey of the literature as it pertains to the problem of multiparameter sensitivity in network theory. In particular, a critical appraisal is made of several multiparameter sensitivity functions, and the problems involved in their computation are considered. Several procedures for their evaluation are described, with attention focused on the auxilliary network approach of Leeds and Ugron and the adjoint network approach of Director and Rohrer. Another approach considered is the so-called direct approach, in which an algorith, is used to obtain directly the partial derivaties of the network function.

DOI:10.1049/piee.1970.0408

出版商:IEE    

年代:1970

数据来源: IET

摘要:

An analysis is presented for the problem of the sheet-secondary induction motor when the sheet is displaced sideways from a symmetrical position. It is shown that the forces which act on the sheet are decentralising and that the magnitude of these forces and of the changes in propulsive force and winding impedance are dependent on five dimensionless parameters which are functions of the motor's design and its operating slip. Measurements made on a small linear motor, while indicating that the neglected skin effect and endwinding leakage fluxes can be significant, show reasonable agreement with the analysis. A means of reducing the decentralising force is suggested, and reference is made to a method of achieving lateral stabilisation of a freely suspended sheet.

DOI:10.1049/piee.1970.0411

出版商:IEE    

年代:1970

数据来源: IET

摘要:

The region of minimum damping for a 2-machine system, which occurs at low speeds, in which self-excited hunting may take place is investigated. Under certain circumstances, it is shown that, even where machines are provided with satisfactory damper windings, negative-damping phenomena may be exhibited. A transfer function for a 2-machine system is set up to which various stability criteria may be applied. Frequency-response curves for a typical system which may be employed in a large pumped-storage scheme are given. The rotor oscillations obtained by tests on an actual system are reproduced, and comparisons are made with predictions obtained by application of the stability-criteria method which is developed.

DOI:10.1049/piee.1970.0412

出版商:IEE    

年代:1970

数据来源: IET

摘要:

In the paper, the method of dimensional analysis is applied to determine the flashover characteristics of polluted insulators. Expressions deduced for the flashover voltage in a d.c. circuit under simplified conditions are found to agree with the analytical findings of previous authors. The work is then extended to flashover characteristics in a.c. systems, where the dynamic properties of arcs are introduced. It is found that the same functional dependence of the flashover voltage on pollution and insulator characteristics prevails as for d.c. conditions, although the magnitude of the flashover voltage may be different in the two cases. Finally, an expression for the velocity of arc propagation along the polluted insulator surface is deduced with due consideration of insulator, layer and circuit parameters. Of special interest is the dependence of the ultimate arc velocity on the short-circuit current of the test circuit, as well as the expression for the minimum voltage necessary to start arc motion. Whenever possible, the analyses included in the paper are compared with previous field and/or laboratory experience.

DOI:10.1049/piee.1970.0413

出版商:IEE    

年代:1970

数据来源: IET

摘要:

An analytical treatment of four capacitor-input rectifier circuits is outlined, and computed results are indicated. The instantaneous minimum output voltage is given as a function of the source resistance, the load resistance and the filter capacitance, for a knowledge of this quantity is essential to the design of regulated power supplies. Peak-peak voltage ripple, peak current and root-mean-square current are also given, to permit the design of transformer and rectifiers. Significant differences are found to exist between the results and those published previously.

DOI:10.1049/piee.1970.0414

出版商:IEE    

年代:1970

数据来源: IET

摘要:

The method of Popov is extended in the paper in order to derive sufficient conditions for the asymptotic stability in the mean of a Lur'e-type nonlinear feedback system having stochastic parameters in the linear part. It is assumed that the nonlinear characteristic is specified by known bounds on the slope, as well as on the sector in which it may lie. It is also assumed that the statistics of the random parameters of the linear subsystem are known. The stability conditions developed are analogous to those proved for the deterministic versions of the problem.

DOI:10.1049/piee.1970.0418

出版商:IEE    

年代:1970

数据来源: IET