By Topic

Electrical Engineers, Proceedings of the Institution of

Issue 9 • Date September 1971

Filter Results

Displaying Results 1 - 25 of 33
  • Exact model for delta-modulation processes

    Page(s): 1155 - 1161
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (851 KB)  

    A mathematical model is described which generates a pulse waveform identical to that of a single-integrator delta modulator, provided that the input signals to the latter do not cause slope overloading. The model uses analogue techniques of angle modulation and sampling to generate time- and amplitude-quantised signals, thus readily lending itself to exact analysis. The delta-modulation process is treated in a general manner that is equally applicable to delta-entry and sigma-entry systems. By this means, a central delta modem is defined which includes both pulse modulation and local decoding (prior to final filtering) of the pulse waveform. The model formulation is such that it is equivalent to the delta modem. The equivalence of the delta modem and model is proved analytically. It has also been verified by simulation on a digital computer and demonstrated experimentally. The model can be extended to simulate a double-integration network, provided that the necessary prediction is included. The model can also be extended to represent pulse-code modulation, because a linearly quantised p. c. m. siganal can be obtained by suitable sampling of the output of a delts modulator. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • H.F. data transmission using chirp signals

    Page(s): 1162 - 1166
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (682 KB)  

    Swept-frequency or chirp signals are currently under investigation for data-transmission applications. In particular, long-range air/ground communication in the h.f. band may benefit from the use of these wideband signals owing to the inherent protection chirp signals offer against fading in a time-varying multipath channel. The theory of pulse compression and data transmission using chirp signals is outlined, and an experimental communication system is described with measured error rates in noise and carrier interference. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Propagation and radiation behaviour of corrugated feeds. Part 1: Corrugated-waveguide feed

    Page(s): 1167 - 1176
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1238 KB)  

    An investigation of the propagation and radiation behaviour of circular corrugated waveguides is described. Particular attention is given to modes of unity azimuthal dependence because of their importance in antennafeed applications. It is shown that the radiation pattern of a corrugated waveguide exhibits nearly perfect symmetry over a 1.5:1 frequency band, and, when the corrugations are approximately ¿/4 deep, the pattern is symmetric and there is no crosspolarised component of radiated field. The attenuation of the dominant HE11 mode is investigated theoretically and is shown to be less than that of the H11mode in a uniform waveguide over at least a 2:1 frequency bandwidth. An important similarity is described between the propagation behaviour of a corrugated waveguide and that of a dielectric rod of low relative permittivity, such as those used in fibre optics and optical waveguides. Finally, the determination of the input voltage standing-wave ratio (v.s.w.r.) at the junction between homogeneous and corrugated waveguides is theoretically and experimentlly studied. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Propagation and radiation behaviour of corrugated feeds. Part 2: Corrugated-conical-horn feed

    Page(s): 1177 - 1186
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1163 KB)  

    A theoretical and experimental investigation of the radiation behaviour of conical corrugated horns is described. The horn-aperture field is determined using spherical-mode analysis, and the radiation pattern is obtained by two methods, one of which employs a Kirchhoff-Huygen integration over a constant-phase surface at the mouth of the horn, and the other of which employs an expansion of the aperture field in terms of TE and TM spherical modes of freespace. Excellent agreement is obtained between the two methods and with experimental results. A theoretical investigation is reported of the use of lenses to correct the phase of a conical corrugated horn. Finally, the performance of paraboloid antennas using corrugated horns as feeds is briefly discussed. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Field configuration of the TMc01 mode in an elliptical waveguide

    Page(s): 1187 - 1189
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (377 KB)  

    A new field configuration for the TMc01 mode in an elliptical waveguide is proposed. The theoretical computations are verified by practical measurements. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Wave polarisation and its influence on the power available from a radio signal propagated through the ionosphere. Part 3: Two-hoop modes

    Page(s): 1190 - 1196
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (927 KB)  

    In Pts. 1 and 2 of this paper, an analysis and numerical calculations were given for the fractions of power associated with linearly polarised components of the ordinary and extraordinary waves at a distant receiver, for single-hop sky-wave modes at medium and high frequencies. The present paper extends the analysis to the case of 2-hop propagation. It deals in particular with the effect of the midpath ground reflection. Expressions are given for the change in wave polarisation and loss of power during this reflection, and for the ionospheric coupling on the up going leg of the second hop. Numerical results for a number of sample paths are quoted and discussed. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Optical approximation for residue series of terminal gain in radiowave propagation over inhomogeneous earth

    Page(s): 1197 - 1202
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (846 KB)  

    The method of geometric-optical approximation is applied to the residue series of the obstacle gain, or `terminal gain¿, which has been previously introduced. This approximation leads to a simple formula for the terminal gain which consists of two terms representing, respectively, the direct ray and the reflected ray from the ground, in the same way as does the corresponding formula of the field strength in the case of radiowave propagation over homogeneous Earth. The optical values obtained from this formula, and the exact values given by the residue series, are numerically compared with the corresponding flat-earth values (obtained by the formula previously published) for various obstacle heights and distances in the case of a ridge and a bluff on homogeneous earth. A very good agreement is found in the region slightly before the horizon, when the obstacle is high enough from the ground, particularly in the ridge case. When the obstacle height is not large enough, on the other hand, the flat-earth values show a very good agreement with the residue values. Finally, an empirical formula is introduced to estimate the gain caused by a ridge or a bluff on homogeneous earth, in terms of the values found from the diagrams of the terminal gains, without important restrictions for its location in the wavepath. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • IEE Conference Publication 77. Aerospace antennas

    Save to Project icon | PDF file iconPDF (169 KB)  
    Freely Available from IEEE
  • Numerical solution of 2-dimensional scattering problems using a transmission-line matrix

    Page(s): 1203 - 1208
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (714 KB)  

    A numerical method using impulse analysis of a transmission-line matrix is introduced and used to obtain wave-impedance values in a waveguide. The method is demonstrated by applying it to the scattering caused by a waveguide bifurcation. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Diffraction by a multilayered dielectric-coated sphere with an azimuthal slot

    Page(s): 1209 - 1214
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (724 KB)  

    The wall air-gap concept for low-loss lines and reactive-wall waveguides is employed in the exterior problem of a dielectric-coated sphere with an aximuthal slot. The results for the gain and radiation pattern for a specific case are based on a boundary-value solution, and are optimised numerically to establish the concept. It is shown that, for a spherical antenna of electrical radius k0a = 5, coated with a dielectric layer (of thickness and relative permittivity equal to 0.254¿ and 16, respectively), which encloses a wall airgap (of 0.00303¿ thickness), the increase in gain over the uncoated antenna is 5.17 dB, while the shift in the main lobe is 12.5°. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Full text access may be available. Click article title to sign in or learn about subscription options.
  • Whither nuclear power?

    Page(s): 1215 - 1226
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (2423 KB)  

    The paper commences with a broad examination of the likely role of nuclear power in relation to other sources of primary energy for electricity generation in the UK, and then briefly reviews the historical reasons for the choice of different types of reactors in various countries. The design and operational performance of the Mk. I gas-cooled-reactor stations (Magnox) of the UK's first nuclear-power programme are fully discussed. The paper continues with an account of the progress to date in the design and construction of the Mk. II gas-cooled reactor, stations (a.g.r.) of the second nuclear-power programme and a description of the a.g.r. system. Basic descriptions are given of the more advanced types of thermal-reactor systems available for large-scale application and from which a successor or concomitant to the a.g.r. may be chosen, namely the Mk. III gas-cooled reactor, also known as the high-temperature reactor (h.t.r.), and the steam-generating heavy-water reactor (s.g.h.w.r.), and also of the type which should become available for commercial exploitation within a few years, the fast-breeder reactor. The paper concludes by considering the dilemma facing the CEGB in the immediate future before deciding on which more advanced reactor type to adopt. The advantages and disvantages of the four options open to the CEGB¿choice of the h.t.r.s.g.h.w.r. or a light-water reactor, or adherence to the a. g.r.¿are explained. The cost of introducing a more advanced reactor system can be so great that the case for internationally financed launching programmes is indisputable. In spite of the present uncertainties about the direction of nuclear power, there is no dilemma about the merit of nuclear power for electricity generation in the long term. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Formulas and tables for mutual inductance between parallel circuits with earth return

    Page(s): 1227 - 1236
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1137 KB)  

    Existing formulas for the mutual inductance between parallel circuits with earth return, which are required for the calculation of interference, are either inadequate or difficult to apply in certain cases. The original formulas given by Carson have been modified and extended to give a more useful presentation in terms of the rectangular co-ordinates of the conductors, and Tables calculated by a computer are given for the ready application of the formulas. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Dielectric design criteria for solid-insulated superconducting a.c. cables

    Page(s): 1237 - 1241
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (683 KB)  

    The electrical and thermal requirements of a solid dielectric for superconducting a. c. cables have been determined theoretically. From some recently published data on thin samples, such criteria seem atainable with certain nonpolar polymers; the range for experimental work on more relevant dimensions and geometry is specified. The transmission characteristics of such a cable are considered good. Economic and technical comparisons are made briefly with similar cables which have nonsolid insulants. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Frequency response of a.c.-d.c. convertor with constant-current control

    Page(s): 1242 - 1246
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (582 KB)  

    A transfer function is derived for the 3-phase bridge-connected rectifier with a sampler as the phase controller which is different from the conventional inverse-cosine device. The effect of the time lag associated with the controller is accounted for in formulating the small-signal equations. The stability of the current-control loop is investigated with the aid of graphical methods. The results, in general, agree with those obtained from a physical model. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Multigroup convertors with series a.c. connection

    Page(s): 1247 - 1253
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (944 KB)  

    The paper presents an analysis and assessment of multigroup convertors with the group transformers connected in series on the a.c. side. Two such arrangements are examined; one with series connection and the other with parallel connection of the d.c. side. The d.c. and a.c. characteristics are derived for rectification and inversion, and it is shown that, if these two types of convertor are supplied by the same a.c. system, the lowest-order harmonic on the a.c. side is the 23rd. This is achieved with ordinary delta-star, star-star transformers. The suggested arrangement operates at a considerably higher power factor, but it is inferior with regard to the rating of rectifying elements and transformers when compared with the conventional multigroup convertor. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Full text access may be available. Click article title to sign in or learn about subscription options.
  • Magnetic permeance of identical double slotting. Deductions from analysis by F.W. Carter

    Page(s): 1257 - 1268
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1475 KB)  

    Using the analytical results of an original, as yet unpublished, work of the late F.W. Carter, which is presented in some detail in an appendix to the paper, computed numerical values are given for the permeance per tooth pitch between two identically slotted surfaces when the teeth on one are centrally opposite the slots on the other, for a range of tooth and slot widths. By comparison with the known case when the two sets of teeth are opposite, values are given for the difference of permeance between the two positions. These numerical results are utilised to obtain the `flux-utilisation coefficient¿ in Guy-type inductor alternators as a function of dimensionless parameters characterising the slotting and the airgap. Further, a process of crossplotting gives the ratios of slot and tooth width to airgap width which make the ratio of the change of permeance to the square of the `unslotted permeance¿ an optimum, for possible use as a guideline from which to start the design of vernier reluctance motors. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Tooth-ripple losses in electrical machines. Some basic measurements

    Page(s): 1269 - 1274
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (716 KB)  

    An experimental investigation has been carried out of the eddy-current loss generated at the face of a stack of ferromagnetic laminations by a travelling wave produced by permeance variations, the conditions reproducing those which may exist at the pole face of an alternator. Measurements cover a range of values of lamination thickness, slot pitch, flux density and frequencies up to 3kHz. Experimental results are compared with calculated values based on linear theory. Certain of the phenomena of flux penetration are studied experimentally, and qualitative explanations are offered. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • State-space eigenvalues program for stability of regulated synchronous machine

    Page(s): 1275 - 1279
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (406 KB)  

    The program determines the steady-state stability of a synchronous machine connected to an infinite busbar through an external reactance. The excitation control can be similar to, or simpler than, a generalised form of automatic voltage regulator. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Full text access may be available. Click article title to sign in or learn about subscription options.
  • Full text access may be available. Click article title to sign in or learn about subscription options.
  • Full text access may be available. Click article title to sign in or learn about subscription options.
  • Full text access may be available. Click article title to sign in or learn about subscription options.
  • Full text access may be available. Click article title to sign in or learn about subscription options.

Aims & Scope

The Proceedings of the Institution of Electrical Engineers was published by the IET between 1963 and 1979.

Full Aims & Scope