摘要:

A photo-electric cell having the form of a parallel-strip transmission line in which the lower strip is photo-emissive is proposed as a means of generating millimetre waves from two laser beams.The non-emissive strip is maintained at a positive potential with respect to the emissive strip, so that photo electrons are attracted to it. By making the potential as large as possible and the separation of the strips as small as possible the electron transit time is reduced.Two laser beams, differing in frequency by the required millimetric frequency, are directed on to the photo-emissive surface along the strip at almost grazing incidence. Electron emission is proportional to the instantaneous intensity of the two beams together; as this is proportional to the square of the sum of their amplitudes a difference-frequency term (in the millimetric range) appears in the photo-current emitted. As the laser beams travel almost parallel to the strips, the phase velocity of the beams measured along the strips is almost equal to that of a millimetric TEM wave travelling between them. Through the electron-emission process, such a TEM wave is in fact generated, and grows linearly in amplitude with distance along the strips.The theory of the device is worked out, and a numerical example is given.

DOI:10.1049/piee.1963.0071

出版商:IEE    

年代:1963

数据来源: IET

摘要:

The paper describes the response of a synchronized van der Pol oscillator to small-amplitude signals accompanying the synchronizing signal. A simple method of characterization, which involves the response to symmetrical and antisymmetrical sideband pairs of the synchronizing signal, is obtained analytically and is shown to be simple to use. Advantages of this particular characterization of small-signal response are demonstrated by examples, one of which discusses the response of a synchronized oscillator to narrowband noise. A practical oscillator is presented whose behaviour closely approximates to that of the van der Pol oscillator, and which can be used for practical application of the filtering properties of the synchronized oscillator.

DOI:10.1049/piee.1963.0072

出版商:IEE    

年代:1963

数据来源: IET

摘要:

A system is described for the recognition of the signals of a redundant 5-unit telegraph code using a correlation technique. The expected error rates of this system, when the signals are perturbed by Gaussian noise, are calculated and compared with experimental results obtained from equipment constructed. The theoretical and practical error rates agree, and are less than those obtained by feeding the perturbed signals directly to a teleprinter.

DOI:10.1049/piee.1963.0073

出版商:IEE    

年代:1963

数据来源: IET

摘要:

A series expression for the near-field radiation pattern of an aerial obtained with a directive measuring aerial in a two-dimensional system is derived from a cylindrical-mode expansion of the radiated field. Patterns calculated from this series show better agreement with experimental results at shorter ranges than is provided by previous series evaluations. An inversion of the first few terms of this series suggests a convenient technique for the determination of the radiation pattern from near-field measurements. Calculations based on this method of inversion indicate that the approximate shape of the pattern may be obtained with relatively little effort from the near-field pattern yielded by a small measuring aerial at a range ofa2/λ, whereais the aperture length of the transmitting aerial. At ranges considerably shorter thana2/λ, a more directive measuring aerial, which provides a closer initial approximation to the far-field pattern, has the advantage of reducing the amount of calculation required.

DOI:10.1049/piee.1963.0074

出版商:IEE    

年代:1963

数据来源: IET

摘要:

The paper describes how the principle of a Van Atta linear array may be extended to circular arrays, which can act as corner reflectors over 360°. It is also shown that several methods are available for varying the direction of the reflected signal relative to the incident wave. The properties of such arrays with 2-way amplification in the delay paths is discussed, and some possible applications are suggested in the field of responder beacons and satellite communication.

DOI:10.1049/piee.1963.0075

出版商:IEE    

年代:1963

数据来源: IET

摘要:

The common-emitter current gain (β0) of diffused-base transistors increases and eventually becomes negative as the temperature is raised. This effect is attributed to a field-dependent current of collector minority carriers flowing into the base. Two types of germanium transistor have been studied in detail. In the first transistor (gold-doped) the collector has low bulk lifetime and in the second (sand-blasted) a high surface recombination velocity at the collector contact. For both types satisfactory agreement between theory and experiment has been obtained. The results indicate that the principal source of the additional base current can be determined in any particular transistor by measuring the current and temperature dependence of β0.

DOI:10.1049/piee.1963.0076

出版商:IEE    

年代:1963

数据来源: IET

摘要:

The thermal problems associated with the design of layer-type h.v. transformer windings are outlined, and the concept of ‘fully developed’ thermal and hydrodynamic conditions is introduced. The equations governing the distributions of interlayer temperature and duct-oil velocity are derived for these conditions. The effect of the thermal field on oil density and viscosity in determining the velocity distribution is taken into account.The resistance-network analogue computer used in the iterative solution of the equations is described, and the procedure is explained. The results thus obtained for a particular case are compared with test values. When the test values represent significant departure from fully developed conditions, a correlation method can be employed that gives satisfactory agreement between analogue and test results within the limits of accuracy claimed. Methods for improved accuracy and further application are indicated.

DOI:10.1049/piee.1963.0078

出版商:IEE    

年代:1963

数据来源: IET

摘要:

The behaviour of transformer windings under axial short-circuit forces has not been fully understood up to the present time. The paper attempts to remedy this deficiency by describing the results of a comprehensive short-circuit test programme and by producing a theoretical approach to the problem.The authors show that a large power transformer of 33.3 MVA single-phase, when subjected to short-circuits, has a mechanical equivalence for which the relevant motion equations are derived. These control the behaviour of the winding and, when suitably programmed for computer solution, produce calculated values of axial forces and coil displacements. The behaviour is fully borne out by the test results, which also show the influence of the dynamic phenomenon, including the occurrence of a state of resonance for specific conditions of the insulation, under variable-frequency excitation.It becomes apparent that amplification of forces, both within the winding and on the winding supports, can take place and are calculable. These forces can be controlled by judicious use of the controlling parameters, which may be so chosen as to avoid these ill effects, provided that the heat treatment of the windings has been rigorously carried out and that the stability of the insulation is maintained.

DOI:10.1049/piee.1963.0079

出版商:IEE    

年代:1963

数据来源: IET

摘要:

The paper gives the mathematical formulation, and indicates the mathematical solution, of the problem of the dynamic behaviour of a transformer winding under axial short-circuit forces, certain basic physical assumptions being made initially. Various practical tapping arrangements are considered so that there may be either magnetic balance or unbalance between the winding and an adjacent winding of constant length.Two methods of solution are discussed. In the classical method, it is explained how a system of ordinary linear differential equations with constant coefficients may be solved. This method can be used only when the stiffnesses of the winding insulation and end insulation remain virtually constant. When these stiffnesses vary, the coefficients are no longer constant and the classical method is impracticable, and the second method of adapting the mathematical formulation of the problem for solution with a digital computer is used. The system of ordinary linear differential equations is replaced by an approximately equivalent system of linear difference equations with constant time step-length. Assuming that some empirical law or data are known for the variation of stiffness in the insulation elements, these difference equations can then be programmed for the digital computer.Attention is drawn to the advantages of using a digital computer, even with constant insulation stiffnesses, because the work in the classical method may be tedious and involved. Finally, two sets of results from the digital computer are compared with test measurements with a fair measure of agreement.

DOI:10.1049/piee.1963.0080

出版商:IEE    

年代:1963

数据来源: IET

摘要:

A 7000-ton electromagnet forms part of the 7 GeV proton synchrotron Nimrod now under construction at the Rutherford High Energy Laboratory, Harwell. The paper outlines the design of the pulsed power supply for this magnet. The derivation of the power-supply requirements is given, and possible power supply systems are reviewed briefly. The evolution of the design of the selected system, namely motor-alternator flywheel set plus a grid-controlled mercury-arc rectifier equipment, is discussed in some detail.

DOI:10.1049/piee.1963.0081

出版商:IEE    

年代:1963

数据来源: IET