摘要:

Using a previously proposed quality-grading method, tests have been made of the effects of gain and delay inequalities between the luminance and chrominance channels of a 625-line NTSC-type broadcast colour-television system.50% favourable opinions are obtained with pictures impaired by a gain inequality, expressed as the error in chrominance-channel voltage gain, of ±56% 95% favourable opinions are obtained with a gain inequality of ±36%. For delay inequality the corresponding values are ±350 and ±210ns, respectively.

DOI:10.1049/piee.1965.0299

出版商:IEE    

年代:1965

数据来源: IET

摘要:

Formulas are given to help in the estimation of the positions of poles and zeros of the open-loop gain of an uncorrected transistor amplifier. Design curves are provided to enable the determination of a modified pole-zero configuration which will yield a desired gain and phase margin against oscillation. A synthesis procedure is described which yields a network making the necessary modifications to the pole-zero configuration. Formulas for element values enable the process to be carried out with simple arithmetic calculations for a type of amplifier commonly encountered.This process does not involve the usual practice of measuring the open-loop frequency response of the uncorrected amplifier and then correcting this to approximate to Bode's ideal-loop-gain characteristic. This correction usually involves either fitting a required loss curve with a rational function or an equally tedious ‘cut-and-try’ experimental process.

DOI:10.1049/piee.1965.0300

出版商:IEE    

年代:1965

数据来源: IET

摘要:

The paper describes a method of measuring correlation functions of binary time signals. The use and application of correlation functions are discussed in a general manner, and the authors point out the diversity of fields in which these functions are found. A method of correlation employing logic switching devices is detailed, and, as an example of operation, the autocorrelation of binary noise which has zero crossings occurring at random intervals is described. Finally it is shown that the method is satisfactory and has certain advantages.

DOI:10.1049/piee.1965.0301

出版商:IEE    

年代:1965

数据来源: IET

摘要:

The paper considers the polar response of an array of similar radiators placed uniformly around a circle, in which each radiator is phase-corrected to bring the radiation from all radiating elements into common phase in one direction. Such an array tends to have a pattern with undesirably large side lobes. The effects of varying (a) the polar response of the individual elements, (b) the relative weighting of the elements and (c) the element spacing, are examined. It is found that the side-lobe level can be greatly reduced if (a) each element has a polar pattern confined mainly to the forward hemisphere, with, in particular, a null at 90°, (b) only elements within ±90° of the main beam are used, and (c) the spacing between elements is not more than half the wavelength.

DOI:10.1049/piee.1965.0303

出版商:IEE    

年代:1965

数据来源: IET

摘要:

The paper discusses the results of an experimental investigation of an anomalous galvanomagnetic effect in an evaporated indium-antimonide film. The film used was prepared by the step-by-step method of evaporation in a vacuum, producing successive deposits on a clean glass substrate. The electrical characteristics of the film were measured in a steady magnetic field and showed some unusual features such as high resistivity, a relatively large Hall coefficient dependent on the applied magnetic field and a negative magnetoresistance effect at room temperature. These anomalous effects have been analysed qualitatively in terms of the inhomogeneous nature of the film.

DOI:10.1049/piee.1965.0304

出版商:IEE    

年代:1965

数据来源: IET

摘要:

Integral expressions for the radiation resistances of a point source of electric current and a filament of finite length with a triangular current distribution are obtained for the case in which these sources are immersed in a loss-free and unbounded magnetoionic medium so that they are parallel to the direction of the magnetostatic field. The radiation resistance of the point source of electric current is found to become infinite in two frequency ranges, whose values are stated precisely, and this infinite behaviour is related to the medium resonances. It is found that, for the current filament, the radiation resistance remains finite for all frequencies except the upper hybrid resonant frequency. The reasons for the infinite behaviour of the radiation resistance at the upper hybrid resonant frequency are due to the limitations of the magnetoionic theory on which the present work is based. Numerical results for the radiation resistances of the two elementary electric-current sources are given for some typical values of the parameters of interest.

DOI:10.1049/piee.1965.0305

出版商:IEE    

年代:1965

数据来源: IET

摘要:

The problems involved in the design and the construction of a wideband transistor amplifier for use in a submerged repeater are discussed in the paper. The maximum transmission frequency is 4284 kc/s.The amplifier consists of two three-stage feedback amplifier units. Only one type of transistor is used throughout to simplify reliability assessment. The factors leading to the choice of this type from among those commercially available are discussed. A brief account of the special components employed, and their effect on the design of the amplifier, is given.Several prototype models and the amplifiers used in the repeaters have been constructed to the design given in the paper. Two repeaters have been installed in the St. Margaret's Bay-La Panne No. 6 cable to extend the circuit capacity from 216 to 420 channels.

DOI:10.1049/piee.1965.0306

出版商:IEE    

年代:1965

数据来源: IET

摘要:

A t.d.m.-exchange system is described in which the subscribers' line equipments have permanently allocated channels. Ifnchannel multiplexes are used, the subscribers' lines are effectively divided intonseparate space-division exchanges with common registers and junctions. Existing trunking theory still applies, but with the unusual aspects that the division bynresults in an aggregation ofnsmall, or even very small, exchanges, and that the relatively high cost of the switching elements justifies greater care in trunking design to minimise the number of switching elements.

DOI:10.1049/piee.1965.0307

出版商:IEE    

年代:1965

数据来源: IET

摘要:

This paper discusses the technical problems of traffic flow encountered in the overall design of a communication system for a specific purpose, namely the provision of air-traffic services to civil aircraft. The major part of the paper deals with(a) the evaluation of queueing delays on aeronautical mobile (aeromobile) speech channels, from which the number of channels required to meet a chosen delay criterion is estimated(b) the minimum signal/noise ratio required for satisfactory communication on aeronautical radio channels, and the transmitter power required to produce it.Statistics of operator loading, channel holding times and message-arrival rates are given, and the role of the human operator as a component of the system is evaluated.

DOI:10.1049/piee.1965.0308

出版商:IEE    

年代:1965

数据来源: IET

摘要:

It has already been shown how to obtain 2-speed single-winding squirrel-cage induction motors, using a normal stator with all coils identical, and with only six terminals to the winding. The earlier methods showed how an integral-slot winding may be modulated to give a 2-speed winding for any pole combination, and also how to design a fractional-slot 2-speed winding for pole combinations which do not include a multiple of 6. The fractional-slot windings are the best, and this paper completes the record of close-ratio pole-amplitude modulation in its basic form by showing how to design a fractional-slot winding for any close-ratio pole combination.The performance of machines with such fractional-slot windings very nearly approaches that of a single-speed motor, for both speeds; and it is thought that, for most applications, these fractional-slot windings will supersede the earlier integral-slot ones. Tables of finished winding designs for one pole combination are given in full, together with details of the design methods, which are illustrated by the complete working of one particular design. The basic part of the task of converting the single-winding squirrel-cage induction motor into a close-ratio 2-speed machine has therefore been completed and recorded in full. The application of the same principles to wide-ratio 2-speed machines has been separately described, as will also be certain further developments of the work already recorded.

DOI:10.1049/piee.1965.0312

出版商:IEE    

年代:1965

数据来源: IET