摘要:

The paper describes two sets of measurements of aerial noise temperature at a frequency of 5650 Mc/s in the allocated band for commercial radar, these being made with (a) an aerial pointing over the land and (b) an aerial pointing over the sea. The results are discussed in relation to theory and possible applications.

DOI:10.1049/piee.1965.0184

出版商:IEE    

年代:1965

数据来源: IET

摘要:

The use of thin, uniaxially anisotropic, magnetic films in binary-storage cells using the rotational switching system is described briefly. The apparatus used traces out automatically curves of cell output against switching current for switching pulses 6–60ns long. Continuous films on conducting substrates were used and it was found that asymmetries appeared in the curves for the shorter pulses, owing to the field from eddy currents induced in the substrate opposing any changes in the cell setting. However, the curves became symmetrical if the film was in a multidomain state before the cell was set.The experiments also show that the reduction and distortion of the applied fields caused by intersecting conductors can be virtually eliminated by slotting the conductors but that segments ½mm wide are permissible. Contrary to expectation, the drive current required to set the film cells increases with decreasing pulse length (e.g. 1A at 60ns, 2A at 15ns, 5A at 6ns); this effect is only partially explained by substrate eddy currents. The effects of the width of the drive and digit conductors on the required drive currents are explained by the propagation of magnetisation changes away from the edges of the conductor, probably caused by magnetostatic coupling within the film. Also, contrary to expectation, the digit-conductor width was found not to affect the digit current required for widths up to 5mm for films more than 800Å thick. Although this cannot be completely explained by the observed propagation of magnetisation changes, limiting the propagation by using an isolated patch of film produces the expected result that the digit current required to set the cell is proportional to the digit-conductor width.

DOI:10.1049/piee.1965.0185

出版商:IEE    

年代:1965

数据来源: IET

摘要:

An expression is derived for the complex current gain of a composite transistor. It is shown that the current gain of a composite transistor is influenced by the low-frequency current gain and cutoff frequency of the individual transistors. The emitter and collector depletion-layer capacitances and the extrinsic base resistances are also shown to influence the current gain of a composite transistor. It is found that there is a considerable difference between the current-gain characteristic of a composite transistor predicted by the equation for α based on one-dimensional diffusion theory and that predicted by the first-order approximation. Measurements are made of the steady-state frequency response and the transient response of a composite transistor constructed from two alloy-junction transistors of the same polarity. Close agreement is found between the measured characteristic and the characteristic predicted by the equation for α based on one-dimensional diffusion theory where the effects of extrinsic components have been taken into account.

DOI:10.1049/piee.1965.0186

出版商:IEE    

年代:1965

数据来源: IET

摘要:

Using a previously proposed quality-grading method, tests have been made of the effect of both flat and triangular random noise on still, monochrome, 625-line pictures typical of scenes in television broadcasting. 50% favourable opinions are obtained with a signal/weighted-noise ratio of 36db and 95% favourable opinions with a ratio of 39db.

DOI:10.1049/piee.1965.0187

出版商:IEE    

年代:1965

数据来源: IET

摘要:

A rudimentary method of computation is developed by which an approximation to the group delay of minimum-phase networks can be obtained directly from the attenuation function without any reference to phase. The technique is especially suitable for use with a computer; it is illustrated by plots of the delays of the Butterworth filter and the Thomson network. Judged by these plots, the accuracy of the method is about 10%.

DOI:10.1049/piee.1965.0188

出版商:IEE    

年代:1965

数据来源: IET

DOI:10.1049/piee.1965.0189

出版商:IEE    

年代:1965

数据来源: IET

摘要:

The paper describes the resonant magnet network and power supplies of the 4 GeV electron synchrotron Nina, now under construction at the Daresbury Nuclear Physics Laboratory, Cheshire. The requirements of high accuracy and uniformity in the magnetic guide field pose special problems in magnet-network arrangements, excitation methods and control, and these aspects of the accelerator design are discussed in some detail.Special emphasis is given to (a) the dynamic behaviour of the distributed resonant magnet network and its effects on the energy-storage-choke design, (b) the transient characteristics of the pulse power supply and (c) the part played by model and analogue-computer studies during the design stages.

DOI:10.1049/piee.1965.0190

出版商:IEE    

年代:1965

数据来源: IET

摘要:

Simplified cooling fluid-flow equations and temperature distributions are developed which are suitable for quick and easy application without recourse to a computer. These equations show how to determine the duct sizes for efficient cooling. The interaction between coil ducts and cooling tubes is examined, and a novel method of using cooling tubes is proposed and analysed.

DOI:10.1049/piee.1965.0191

出版商:IEE    

年代:1965

数据来源: IET

摘要:

The pole-amplitude-modulation method of obtaining economic and efficient 2-speed and 3-speed operation of a normal 3-phase squirrel-cage induction motor with a single winding, developed by Rawcliffe and Fong, has been applied to the single-phase induction motor.The paper describes the theory and design methods, and presents experimental results obtained with a 3-speed 8/6/4-pole single-phase test motor. Performance of the motor at 6 poles and 4 poles is comparable with that of normal single-phase motors, while at 8 poles it is somewhat inferior. The winding is of a perfectly standard type. Ten terminals only are required for two speeds, and 12 terminals for three speeds, the control gear therefore being extremely simple.

DOI:10.1049/piee.1965.0192

出版商:IEE    

年代:1965

数据来源: IET

摘要:

The complete distribution of the forces acting over the whole of a typical, 2-pole turbogenerator end winding of the involute type is studied and presented in a general form. Further, the way in which these results can be applied to calculate the forces for any other (2-pole) winding of involute type, without restriction as to size, is described. The basic results are presented in such a form that they can be used to determine the point-by-point distribution of forces for any condition of current loading. Additional results give thetotalforces experienced by individual coils of the winding.The method of calculation, which is based upon expressions for the force between any two short, straight, current-carrying conductors, is described. It is very simple and flexible and can be used to determine the distribution of force inanymachine end winding oranyother complex arrangement of conductors.The effects that changes in winding design have on the force distribution are studied. It is shown that the cone angle, the spacing between involutes and the number of stator coils (for fixed electrical loading) all have a considerable influence on the forces. In the cases of the involute spacing and the coil number, simple empirical equations describing their effects are developed.With regard to accuracy of representation, it is shown that the effects of air-gap magnetisation are unimportant; that errors due to the neglect of coil cross-section are of fixed sign and about 5–10% of the true force values; and that errors due to neglect of the machine end surface are generally ±10%. The influences of the stator casing and rotor shaft and retaining ring are briefly considered.The forces due to rotor winding currents are examined, and it is found that, whilst the peripheral and axial components are generally unimportant, the radial component can be as large as 50% of that due to stator currents, and is directed outwards.Brief consideration is given to certain eddy-current effects, and, in conclusion, it is indicated that, owing to these effects, forces computed using values of the subtransient reactance, or indeed actual currents flowing at the instant of short-circuit, will be too high.

DOI:10.1049/piee.1965.0193

出版商:IEE    

年代:1965

数据来源: IET