摘要:

Doubly terminatéd LC filters realised with simulated inductances are considered by some authors to have particularly satisfactory sensitivity characteristics. The paper provides an analytical comparison of the sensitivity characteristics obtainable with such filters and with a cascade of 2nd-order active sections. The results confirm that the simulated-inductance filter can be realised with a limited improvement in sensitivity. It is hoped that this quantitative treatment will allow the designer to decide whether or not the improvements in sensitivity offered by inductance-simulation techniques outweigh other disadvantages inherent in their realisation.

DOI:10.1049/piee.1972.0065

出版商:IEE    

年代:1972

数据来源: IET

摘要:

It is assumed that a sinusoidal RC oscillator consists of a linear, passive or active RC network and an amplifier. The properties of such an oscillator are primarily dependent on its open-loop voltage transfer function. A general form of this function is introduced for RC oscillators of the second order, and expressions for the required maintenance gain and the oscillation frequency are derived. It is shown that there exist four distinct types of 2nd-order oscillators. A set of basic building elements for the oscillators is proposed. This consists of some simple RC networks, a voltage divider, a buffer and two amplifiers. The theory and the building elements are used to develop 18 novel oscillator circuits. All these oscillators have either two earthed tuning capacitances or two earthed resistances. It is shown that six of them can be tuned by varying only one capacitance or resistance. Eight of the oscillators are tunable by varying a voltage parameter; in four of these, the voltage-tuning range can be very wide. 14 additional 2nd-order oscillators are suggested. A general 3rd-order RC oscillator is also considered, and it is shown that there exist 15 distinct kinds of this oscillator. The procedure used in the development of the 2nd-order oscillators can also be applied to the design of those of the third order. It is thought that this will lead to a very large number of different oscillator circuits.

DOI:10.1049/piee.1972.0066

出版商:IEE    

年代:1972

数据来源: IET

摘要:

Exchanges are controlled by processors which comprise logical switching and memory apparatus. The total processing is divided, for economy, between groups of processors, each associated with a transmission circuit or trunk in the exchange. The processors necessary for the control of a connection thus become associated as the connection is built up. Further economy results from the time sharing of a smaller number of processors among the circuit processors of a group by parallel connection, when required, through an interface switch. Electronic devices add time-division time sharing to space-division time sharing and stored-program logic to wired-logic techniques that are already well established in telephone-exchange control systems. Processors and processing in general, and the principles of division for series operation and for time-shared parallel operation, with special reference to the new conditions created by electronic devices, are analysed and defined. Wired and stored-program logic processors are compared, with the conclusion that wired logic should continue as the basis for exchange control systems, but with a backing of stored-program processors for operations that do not greatly affect the economics of exchanges, and for which the flexibility of stored-program logic is an advantage. The conclusions are the basis for exchange systems described in other papers.

DOI:10.1049/piee.1972.0067

出版商:IEE    

年代:1972

数据来源: IET

摘要:

The paper derives the relationship between the angular distribution of incident signals plus noise and the measured angle of arrival, using a twin-beam amplitude-comparison direction-finding system. The analysis allows the aerial phase response and receiver noise to be taken into account. Examples of the use of the analysis are given which derive percentiles of measured angle for a point target, embedded in clutter and adjacent to a patch of clutter. The results give an indication of the signal/clutter ratio required for a particular system performance. The analysis is applicable to a wide range of amplitude-comparison systems and should therefore be of considerable value in system studies.

DOI:10.1049/piee.1972.0070

出版商:IEE    

年代:1972

数据来源: IET

摘要:

A brief survey of past and present impedance relays is given, with particular reference to their immunity from interference owing to non-power-frequency components in their input signals. The frequency characteristic of a suitable digital filter is chosen on the basis of a spectral analysis of a 10 ms section of typical fault waveforms. The chosen filter is used in conjunction with a sampling system of measurement to realise a quadrilateral impedance characteristic. Results of an off line simulation of fault conditions are presented, in the form of typical fault waveforms at the relay input, and the relay operating time for various angles of fault incidence.

DOI:10.1049/piee.1972.0072

出版商:IEE    

年代:1972

数据来源: IET

摘要:

The paper examines important aspects of the asynchronous performance of reluctance machines using the pseudo-constant-speed approach, frequently employed earlier with large synchronous machines. The influence of the arrangement of the conducting material in the rotor is demonstrated, special attention being given to the torque/speed characteristics, the significance of these, particularly for pull-in, and the current distribution between the rotor bars. The influences of the direct-axis-reactance/quadrature-axis-reactance ratio and of stator resistance are also shown. The general problem of determining a 2-coil model for multiple-rotor circuits is considered, and an improved procedure allowing for slip dependence of the parameters is presented. This could be useful in connection with machines of all sizes.

DOI:10.1049/piee.1972.0073

出版商:IEE    

年代:1972

数据来源: IET

摘要:

The paper deals with the problem of the solution of a general network. An attempt has been made to formulate the criteria of solvability and to derive the matrix equations of solution of a linear RLC network, irrespective of how complicated the initial data may be. The method is illustrated by a practical example. The theoretical background and the derivation of some of the equations are given in Appendixes.

DOI:10.1049/piee.1972.0074

出版商:IEE    

年代:1972

数据来源: IET

DOI:10.1049/piee.1972.0075

出版商:IEE    

年代:1972

数据来源: IET

摘要:

A new approach to the design of linear multivariable control systems using the inverse Nyquist array method is proposed and applied to two examples. The technique generalises diagonalisation at zero frequency to an arbitrary finite point on the D contour by minimising the sum of the squares of the moduli of the off-diagonal terms in each row of the inverse open-loop transfer-function matrix. This approach is simple to implement and is especially suitable for interactive computer-aided design. As a large range of possible solutions can be evaluated quickly, this leads either to the choice of a matrix compensator conforming to the requirements of the pertinent stability theorem or to the practical conclusion that the method does not yield a solution to the form considered.

DOI:10.1049/piee.1972.0079

出版商:IEE    

年代:1972

数据来源: IET

摘要:

Essentially related to the problem of spectrum estimation of random data by fast-Fourier-transform techniques is the problem of establishing efficient data windows or data-smoothing procedures for minimising leakage effects. Statistics of spectral estimates derived from finite data lengths indicate that the estimates are related to the true spectrum by a frequency convolution with a Fejer window. It is well known that leakage of power in the spectrum occurs from the nonnegligible sidelobes of this window. The paper presents an investigation into the application of data windows in spectral analysis. Consequent effects on the bias (amplitude) and the variance of the spectral estimates are analysed and compensating factors are specified. Criteria are further developed for comparing the increase in bandwidth of spectral analysis caused by different data-smoothing sequences. As the bandwidth of analysis is dependent on the bandwidth of the spectral window associated with a data window to the frequency tion of the window bandwidth leads to a measure of the loss of frequency resolution entailed by tapering the data. Although no universal definition exists for the bandwidth of a system or a time series, four different expressions are included for the bandwidth of a spectral window which relate the parameters of a data window to the frequency spread of its associated spectral window. Three families of data windows are considered, and computed results are presented which allow the choice of a data window as an optimum compromise between critical factors involved in the design of an efficient spectrum-estimation procedure.

DOI:10.1049/piee.1972.0080

出版商:IEE    

年代:1972

数据来源: IET