摘要:

The paper shows how simple circuitry can be used to combine test points leading to far fewer points to be observed, while still retaining the full ability to detect faults. Rules are laid down for the design of this circuitry that depend on the relationship between the test points. Practical examples are given of circuits for condensing test points for a number of different circumstances. Finally, it is shown how the adequate testing of this additional condensing circuitry can be ensured.

DOI:10.1049/piee.1977.0015

出版商:IEE    

年代:1977

数据来源: IET

摘要:

Measurements of the received signal envelope magnitude have been made in three British cities at frequencies of 85.875, 167.2 and 441.025 MHz. In all cases unmodulated carrier waves were radiated from aerials atop tall buildings, or prominent terrain features, and detected using a vehicle-mounted receiver. These measurements have provided the basis for an analysis of the factors affecting the transmission loss in urban/suburban areas which, in turn, has enabled a propagation prediction model to be constructed. Close agreement between measured and predicted path losses has been found for the various terrains investigated. The statistical prediction errors produced by the proposed model for the three British cities analysed are shown to be similar in magnitude to those obtained using an extrapolation of the Okumura method. Because the proposed model is much less complex and procedurally simpler, it is recommended for use, in the first instance, in British cities.

DOI:10.1049/piee.1977.0016

出版商:IEE    

年代:1977

数据来源: IET

摘要:

The properties of surface-channel charge-coupled shift registers are analysed taking into account all four mechanisms involved in the transfer of charge, namely thermal diffusion, charge gradient-induced drift, fringing-field drift, and interface state trapping. A nonlinear equation for the simulation of the signal transfer and degradation in charge-coupled shift registers in the presence of interface states is derived. It is shown that under some realistic assumptions, the nonlinear properties of both 2-phase and 3-phase devices are governed by the same equation. The theoretical results are used to investigate, by computer simulation, the input/output properties of digital registers. Among the discussed results, special emphasis is placed on worst case output signals. Small-signal and large-signal degradation parameters are also discussed and numerical results are presented.

DOI:10.1049/piee.1977.0017

出版商:IEE    

年代:1977

数据来源: IET

摘要:

The effects of field-dependent mobility on transfer inefficiency due to intrinsic transfer limitations, dynamic-dram conductance and threshold-voltage modulation are calculated for an m.o.s. bucket-brigade delay line. The results show significant differences over previous theories at higher clock frequencies, where line performance is critical if quantisation errors are to be minimised in analogue applications.

DOI:10.1049/piee.1977.0018

出版商:IEE    

年代:1977

数据来源: IET

摘要:

Two models are proposed for the probability density function (p.d.f.) of the amplitude fluctuations that arise when short-duration sound pulses are transmitted under shallow-water conditions. The models are derived for the conditions in which the prevailing surface-wind directions are parallel and perpendicular to the line of transmission. The probability density functions obtained from the models are compared with experimentally measured p.d.f.s and are found to be in excellent agreement. The models are then used to predict the bit-error probability in a binary underwater amplitude-shift-keyed (a.s.k) data-transmission system and the results are compared with experimentally measured error probabilities. It is found that the measured error probabilities lie between the values computed using the p.d.f. models and it is conjectured that the proposed models provide approximate upper and lower bounds to the average error probability in a.s.k. underwater data-transmission systems. Finally, the p.d.f. models are used to compute new receiver-operating-characteristic (r.o.c.) curves.

DOI:10.1049/piee.1977.0019

出版商:IEE    

年代:1977

数据来源: IET

摘要:

A consequence of the projected trend in turbine-generator design towards large airgaps, airgap windings without slots, and superconducting windings, is a progressive change in the nature of the machine from ‘iron-cored’ to ‘air-cored’. A general analysis of fields and winding inductances that is applicable to all configurations is presented. The underlying unity of the various types is brought out, and particular attention is given to a comparison of the conventional design and the fully air-cored (superconducting) machine. In a companion paper the comparative design and performance analysis of air-cored and iron-cored synchronous machines is discussed.

DOI:10.1049/piee.1977.0021

出版商:IEE    

年代:1977

数据来源: IET

摘要:

A consequence of the projected trend in turbine-generator design towards larger airgaps, airgap windings without slots, and superconducting windings, is a progressive change in the nature of the machine from ‘iron-cored’ to ‘air-cored’.A simple analysis is presented which enables the main design and performance paramaters of both types of machine to be calculated and compared. A design philosophy for air-cored machines is outlined, and a number of favourable and adverse design features are revealed. In a companion paper the analysis of fields and inductances in air-cored and iron-cored synchronous machines is discussed.

DOI:10.1049/piee.1977.0022

出版商:IEE    

年代:1977

数据来源: IET

摘要:

A systematic Laplace method is presented for the determination of transient-current propagation in a single transmission line. Earth distortion and skin effects are considered in the analysis. The method permits a quick and accurate evaluation of these currents without using numerical-integration techniques. From the theoretical study, an efficient method of digital simulation is also derived for a simpler current evaluation in computers. Both analytical and simulation expressions are in terms of line and earth parameters, which enables an easy computation of transient current propagation in different transmission lines to be carried out. Results are in good agreement with those obtained by other investigations. Part 1 of the paper deals with a basic single line which would represent either an a.c. or a d.c. scheme. Part 2 of the paper deals with polyphase systems with lossy earth returns (see p. 137).

DOI:10.1049/piee.1977.0023

出版商:IEE    

年代:1977

数据来源: IET

摘要:

In this study, an operational Laplace method is presented for analysing current propagation in 3-phase lines. Basic results obtained in Part 1(see p. 133)are systematically extended to polyphase-line investigations. Modified operational Laplace impedances are used and results can be carried out by a direct use of Laplace transforms and matrix theory. An efficient simulation method is also presented, which permits an easier computation of current surges in computers. Earth distortion and skin effects of conductors are included in the study. Analytical and simulation expressions are in terms of line and earth parameters. Therefore they make easy numerical computations of currents of different lines. Other advantages mentioned in Part 1 of the paper are also found in Part 2 of the paper, e.g. no numerical integration is needed.

DOI:10.1049/piee.1977.0024

出版商:IEE    

年代:1977

数据来源: IET

摘要:

The paper considers the performance of both unswitched and switched distance protection schemes using polarised-mho relays on systems subjected to simultaneous faults. The disturbances considered are flashoverfaults to earth, cross-country earth faults and open-conductor plus earth faults on a double-circuit 132 kV transmission system. Consideration is also given to protection performance for double earth faults separatedby a star-delta transformer. Differences in protection philosophies of British and Continental relay manufacturers are highlighted and a comparison is given for switched schemes employing overcurrent starter units.

DOI:10.1049/piee.1977.0025

出版商:IEE    

年代:1977

数据来源: IET