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Proceedings of the Institution of Electrical Engineers

Volume 120, Issue 2, February 1973

Volumes & issues:

Volume 120, Issue 2

February 1973

Determination of vocal-tract-area function from transfer impedance
Radiometer measurements of atmospheric attenuation at 19 and 37 GHz along Sun-Earth paths
  • Author(s): P.G. Davies
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 2, p. 159 –164
  • DOI:  10.1049/piee.1973.0035
  • Type: Article
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  • p. 159 –164 (6)
    The measurements of attenuation described in the paper refer to data recorded over a 3-year period at a frequency of 19 GHz, and over a 1-year period at 37 GHz. The relevance of these data to Earth-space communication links is discussed. Statistics showing the percentage of observation time for which the attenuation exceeds various values are given for each year for various ranges of elevation angle. At 19 GHz, the values of attenuation obtained from the extreme annual distributions differ by a factor of about two at a given percentage of time. Also, the percentage of time for which the attenuation at 19 GHz exceeded 10 dB for the ‘worst’ month is an order of magnitude larger than the corresponding value for the 3-year period. Statistics derived from data obtained during periods of common observation at 19 and 37 GHz are compared for various ranges of elevation angle. Histograms showing the number of fades as a function of the duration of the fade are presented for both frequencies for fades greater than 5 and 10 dB, and a comparison of the instantaneous values of attenuation at 19 and 37 GHz at fade maxima has been made.
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Transhorizon propagation on v.h.f. and u.h.f. radio links in the United Kingdom
  • Author(s): I.E. Owolabi  and  J.A. Lane
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 2, p. 165 –172
  • DOI:  10.1049/piee.1973.0036
  • Type: Article
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  • p. 165 –172 (8)
    An analysis has been made of v.h.f. and u.h.f. transmission data on 65 overland links of up to 400 km in length in the United Kingdom. The analysis reveals that the field strength exceeded for 1% of the time is significantly greater than that predicted by CCIR recommendation 370-1, especially for band III (150–250 MHz), but also to some extent for band I (41.68 MHz). A detailed analysis is made of several transmission links in which the factors distance, antenna height, terrain irregularities and meteorological condition were very similar, but the operating frequencies were different. The results of the detailed analysis are interpreted in terms of reflection theory using a 4-ray model. The layer heights at which partial reflection gives enhancements of band-III transmissions similar to those observed experimentally are found to correspond approximately to atmospheric layers of maximum lapse rate of refractive index, as computed from meteorological-radiosonde observations.
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Transmission loss at high frequencies on 3260 km temperate-latitude path
Scattering by perfectly conducting rotational bodies of arbitrary form excited by an obliquely incident plane wave or by a linear antenna
Near-field technique for inferring aperture antenna radiation patterns
  • Author(s): A.R. Jamieson  and  R.H.T. Bates
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 2, p. 183 –185
  • DOI:  10.1049/piee.1973.0039
  • Type: Article
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  • p. 183 –185 (3)
    The method of Brown and Jull for inferring the far field from the near field has been extended to arbitrary antennas, with measurements made in one plane only. The primary concern has been with aperture antennas. The theory of the computational reduction of the measured data has been obtained. The results of a practical application of this near-field technique (n.f.t.) to a circular-waveguide-aperture antenna are described. The modal distribution in the waveguide aperture is estimated. This distribution has been substituted into a variational expression for the waveguide admittance. The result is close to the measured value, thereby confirming the accuracy of the n.f.t.
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Microwave data link for computer communication
  • Author(s): A.C. Peatfield ; H.J. Sherman ; A.J. White ; B. Zacharov
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 2, p. 186 –190
  • DOI:  10.1049/piee.1973.0040
  • Type: Article
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  • p. 186 –190 (5)
    An experiment is described in linking to a large digital computer at data rates in the order of 107 bit/s. The system is based on standard British Post Office microwave equipment and well established high-speed wire links; the interface between the two sections uses the CAMAC-system convention. The total system is described, and details are given of some of the equipment not previously published. Important features of the system are the termination of both ends of the link in a high-level-language module (in this case PL1), executing in a multiprogramming operating system, and corrected error rates better than 1 bit in 109.
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Application of time-series algebra to the adaptive equalisation of band-limited waveform-transmission systems
  • Author(s): J.B. Potter
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 2, p. 191 –196
  • DOI:  10.1049/piee.1973.0041
  • Type: Article
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  • p. 191 –196 (6)
    Using time-series algebra, the operation of adaptive equalisers for both minimum-mean-signal-error and minimum-mean-square-error criteria are considered, and the convergence properties of the iterative procedures generally used are discussed. It is pointed out that, in any practical situation, the control criterion and the iterative algorithm to be used, must be selected to provide the desired performance over the range of situations likely to be encountered. The effect of the equaliser on the regenerator-input signal/noise ratio is also considered, and this, together with the economic need to minimise the equaliser length, is shown to lead to a requirement to select the reference sampling point accordingly. One selection algorithm is described, and its operation is demonstrated in an example.
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Millimetre-wave generator that uses a spiralling electron beam
  • Author(s): A.H.W. Beck  and  W.P.C. Mills
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 2, p. 197 –205
  • DOI:  10.1049/piee.1973.0042
  • Type: Article
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  • p. 197 –205 (9)
    A millimetre-wave generator that uses a helical electron beam spiralling around the axis of a nearly square wave-guide is described. The frequency of gyration round the axis is made equal to one-half of the signal frequency, thus halving the longitudinal magnetic field by comparison with those of cyclotron devices. Power outputs in excess of 2W at Q band wavelengths have been achieved with low-current, high-voltage beams, but the most important feature of the device is that the same electro-optical system can be used at considerably shorter wavelengths, for example λ = 2 mm. A brief historical introduction describes the development of this tube in relation to the better known cyclotron tubes.
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Precision hardware circular-arc generation for computer graphic-display systems using line-segment-data
  • Author(s): G. Hughes  and  H.C.A. Hankins
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 2, p. 206 –212
  • DOI:  10.1049/piee.1973.0043
  • Type: Article
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  • p. 206 –212 (7)
    For advanced graphics, it is required that both general and circular functions should be displayed, in addition to alphanumeric and line diagrams. For general functions, software is used, owing to the low frequency of occurrence of general functions on display diagrams. For circular functions, this is not the case, and there is a need for hardware generation with scaling, windowing and scissoring properties. Further, for precision, the circular arc should start and finish exactly on the m × m screen matrix, with points on the drawn arc within one increment of the true arc. This paper describes the generation of arcs by hardware, using successive line-segment data that satisfy the error equations. These errors are derived, and a computer simulation of the hardware logic design is used to analyse the errors and to determine the bit redundancy in the δθ2/2 registers. The final design is capable of generating circular arcs within the prescribed error limits at high generation speeds. The generator may be included in any display system that possesses accurate line-drawing facilities.
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Computer technique for solving 3-dimensional electron-optics and capacitance problems
  • Author(s): A.B. Birtles ; B.J. Mayo ; A.W. Bennett
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 2, p. 213 –220
  • DOI:  10.1049/piee.1973.0044
  • Type: Article
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  • p. 213 –220 (8)
    Electron-optics problems involving planar and axial symmetry are frequently analysed by using iterative procedures to solve Laplace's equation within a specified boundary. The computation time and storage requirement for these procedures may be prohibitive when it is necessary to extend the analysis to three dimensions for problems involving asymmetric fields. An alternative approach is described, known as the method of moments, which does not use an iterative method, but calculates the field directly from the charges induced on the electrodes by the excitation potentials. This technique provides a further facility, which permits the capacitances between arbitrary 3-dimensional electrodes to be obtained. The basic theory and operation of a computer program which employs this method are described. As a practical application, the program has been used to investigate the electron-optical properties of a mesh with rectangular apertures.
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IEE Western Centre Electronics & Control Section: Chairman's address. Electrical aspects of aircraft control
Feasibility of turbogenerator with superconducting rotor and conventional stator
  • Author(s): H.O. Lorch
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 2, p. 221 –227
  • DOI:  10.1049/piee.1973.0046
  • Type: Article
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  • p. 221 –227 (7)
    In a 660 MW turbogenerator, the losses associated with the rotor total some 4.5 MW, mainly due to direct current in the field winding. The feasibility of saving this by making the winding superconducting is examined. The stator coils carry alternating current, and so they cannot be made superconducting, and, in the concept proposed here, the stator is substantially conventional. The new rotor has no iron, except for shaft ends, and the winding is embedded in an insulating cylinder cooled with liquid helium from a refrigeration plant. The winding is protected from harmful a.c. fields by a copper cylinder which rotates with it. The gap is evacuated, and this screening cylinder is kept cold by thermal conduction in the residual gas to a stationary low-temperature shield. The machine has high steady-state-and transient-stability margins, and the need for rapid field changes is greatly diminished The new rotor allows the present stator to be uprated. The economic advantage of the machine, taking refrigeration into account, depends on the degree of uprating found possible, and is in the range £290 000–£830 000 for an output range of 660–1000 MW. Many problems, particularly of a mechanical nature, remain to be solved, but none appears insuperable.
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Open-circuit voltage decay of a turbogenerator
  • Author(s): H. Yee  and  T. Wilson
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 2, p. 228 –232
  • DOI:  10.1049/piee.1973.0047
  • Type: Article
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  • p. 228 –232 (5)
    The decay of terminal voltage of an unexcited turbogenerator, following its disconnection from the a.c. busbars, is determined analytically. It is shown that, because of eddy current in the solid rotor, an infinite number of exponential-decay terms are required to describe the voltage decay. Results obtained theoretically are compared with those of tests carried out by the Central Electricity Generating Board at Northfleet, and good agreement is obtained. Of particular interest are the large quadrature-axis time constants evident in both theoretical and experimental studies.
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IEE Mersey & North Wales Power Section: Chairman's address. Switchgear progression
Improvement of turbogenerator transient performance by control means
New temperature test for synchronous machines
Simplified universal-commutator electric motor
Power-factor compensation of thyristor-controlled single-phase load
Improvement of power-system transient stability by phase-shift insertion
IEE North-Western Utilisation Section: Chairman's address. Less and less about more and more—some aspects of utilisation engineering
Erratum: Safety of household electrical appliances
Transient analysis of underground power-transmission systems. System-model and wave-propagation characteristics
  • Author(s): L.M. Wedepohl  and  D.J. Wilcox
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 2, p. 253 –260
  • DOI:  10.1049/piee.1973.0056
  • Type: Article
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  • p. 253 –260 (8)
    A mathematical model suitable for the analysis of travelling-wave phenomena in underground power-transmission systems is presented. The model is developed in terms of a generalised angular frequency, and may therefore be applied to the solution of steady-state problems or, by means of Fourier-transform techniques, to the solution of transient problems. The model takes into account skin effect in the conductors and in the soil. It is then shown how the system model may be analysed using multiconductor-transmission-line theory to give the transient response of the cable system. The wave-propagation characteristics are given for the natural modes of a certain cable system. These characteristics are examined with a view to their implications on transient phenomena.
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Optical technique for measurement of current at high voltage
  • Author(s): A.J. Rogers
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 2, p. 261 –267
  • DOI:  10.1049/piee.1973.0057
  • Type: Article
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  • p. 261 –267 (7)
    Consideration is given to the design of an optical device for the measurement of current at high voltage based on the Faraday magneto-optic effect in flint glass. A laser beam directed upward from the ground passes through the free atmosphere to interrogate a passive transducer situated on the high-voltage line. The beam is then reflected down to a ground-based detector system. The investigation has been directed, in the first instance, towards the provision of a versatile research tool for the analysis of disturbed-line conditions, although, ultimately, such an arrangement could obviate the necessity for the expensive and bulky insulation found in conventional current transformers. This is particularly relevant in view of the trend towards higher transmission voltages. The appropriate design features are considered in some detail. Their implementation in a prototype device is also considered. The bandwidth of the prototype device was from direct current to 2 MHz, and its dynamic range for less than 5% nonlinearity was 10–12000 A (these figures are not fundamental and can be varied). The device promises to provide a cheap, accurate and robust current-measurement system for various applications in power-transmission networks.
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IEE Western Power Section: Chairman's address. A century of overvoltages
Digital simulation for mode identification in thyristor circuits
  • Author(s): G.N. Revankar  and  S.A. Mahajan
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 2, p. 269 –272
  • DOI:  10.1049/piee.1973.0059
  • Type: Article
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  • p. 269 –272 (4)
    The paper deals with the digital simulation of thyristor circuits wherein the exact circuit operation is not known. Two methods for digital simulation of thyristor circuits are presented. In the first, a switching device is assumed to be an ideal switch operated by a logic module. The need for automatic formulation of the network equations at the mode changeover points is explained, and it is shown how to achieve this by using suitable forcing functions. This method requires assignment of proper initial conditions at the mode changeover points. In the second method, a switching device is modelled by a binary resistance. In this case, the problem of initial conditions at the mode changeover points is eliminated. These methods are illustrated with an example.
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Degradation mechanisms of mechanical connectors on aluminium conductors
  • Author(s): R.D. Naybour  and  T. Farrell
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 2, p. 273 –280
  • DOI:  10.1049/piee.1973.0060
  • Type: Article
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  • p. 273 –280 (8)
    The factors which affect the performance of mechanical connectors for use on aluminium power cables have been investigated. The initial resistance depends upon surface roughness, mechanical load and degree of plastic deformation. The stability of resistance has been studied under conditions of mechanical-load cycling, stress relaxation, interface oxidation, temperature cycling and current loading. The conditions for designing stable mechanical connectors for use on aluminium conductors are given, and the stability of connectors satisfying these conditions has been illustrated by current-cycling measurements.
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Experimental visual prosthesis
Probability distributions for discrete Fourier spectra
  • Author(s): T.S. Durrani  and  J.M. Nightingale
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 2, p. 299 –311
  • DOI:  10.1049/piee.1973.0062
  • Type: Article
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  • p. 299 –311 (13)
    The paper analyses power-spectrum estimates obtained by fast-Fourier-transform techniques. Distributions are obtained for data, augmented, where necessary, by sequences of zeros, and the effect of data smoothing on the reliability of the estimates is considered. The effect of segment averaging is analysed and a joint probability distribution is derived for the resulting spectrum estimates. The number of degrees of freedom per estimate can then be directly determined. 1st- and 2nd-order moments of logarithmic spectra are derived which lead to confidence bands on the spectral estimates. Frequency-domain smoothing is then considered, and it is shown, that, for specified lengths of Gaussian random data, this, unlike data smoothing, does not lead to a reduction in the number of degrees of freedom. Finally, the general case of frequency smoothing followed by adjacent estimate averaging is analysed. A factor is proposed for assessing loss of stability of such estimates. Computer results are given which demonstrate the effects of several data windows and sets of frequency-smoothing coefficients. Results in the appendixes show that loss in degrees of freedom is related to the eigenvalues of a specific covariance matrix.
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Design of Kalman filters using signal-model output statistics
Computer-aided-design procedure for reduced-order observers. Estimate of entire state vector
  • Author(s): N. Munro
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 2, p. 319 –324
  • DOI:  10.1049/piee.1973.0064
  • Type: Article
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  • p. 319 –324 (6)
    A systematic design procedure for reduced-order observers for linear time-invariant dynamical systems described by state-space equations is presented, using an alternative canonical form to that considered by Luenberger. The algorithm developed is suitable for the case where an estimate of the entire state vector is required, and can be extended to the case where only an estimate of a single linear functional of the state is required. The paper is concerned with the computer-aided design of reduced-order observers which will reconstruct an estimate of the entire state vector. The procedure presented is illustrated by an example.
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Direct method for transfer-matrix inversions

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