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1887

Radio and Electronic Engineer

Volume 41, Issue 6, June 1971

Volumes & issues:

Volume 41, Issue 6

June 1971

Electronic control of mechanical handling
The electric and photoresponse characteristics of Ge/ZnSe heterojunctions
  • Author(s): J.T. Calow ; D.L. Kirk ; S.J.T. Owen ; P.W. Webb
  • Source: Radio and Electronic Engineer, Volume 41, Issue 6, p. 243 –252
  • DOI:  10.1049/ree.1971.0082
  • Type: Article
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  • p. 243 –252 (10)
    Wide band gap II-VI compounds deposited epitaxially upon semiconducting substrates have possible applications as solid-state infra-red detectors and imaging devices. The Ge/ZnSe heterojunction has been prepared by vacuum evaporation of epitaxial layers of zinc selenide on to orientated, single crystal, p-type, germanium substrates. Measurements have been made of the electrical characteristics, capacitance properties and photoresponse of these junctions. From these measurements a realistic band model has emerged involving intrinsic and extrinsic defects present in the bulk and interfacial region of the zinc selenide. The data presented suggest that a Mott-type barrier rather than a Schottky barrier is present at the germanium-zinc selenide interface. Techniques are described for reducing the magnitude of this Mott barrier and the resulting change in the physical properties and band structure are discussed.
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Non-linear control system stability investigation using the circle criterion
Self and mutual impedances of two parallel staggered dipoles by variational method
  • Author(s): J.V. Surutka
  • Source: Radio and Electronic Engineer, Volume 41, Issue 6, p. 257 –264
  • DOI:  10.1049/ree.1971.0084
  • Type: Article
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  • p. 257 –264 (8)
    The problem of the self- and mutual-impedances of two arbitrarily located parallel dipoles is solved by using the variational method and a two-term trial function for current distribution. The impedances are calculated for half-wave and full-wave dipoles in non-staggered, echelon and collinear arrangements. In all three cases the results are in excellent agreement with those obtained by the Chang-King five-term theory. In the non-staggered case agreement with experimental results is also very satisfactory.
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12.5 kHz channel spacing for mobile communications in the u.h.f. band between 420 and 512 MHz
  • Author(s): J.R. Brinkley
  • Source: Radio and Electronic Engineer, Volume 41, Issue 6, p. 265 –272
  • DOI:  10.1049/ree.1971.0085
  • Type: Article
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  • p. 265 –272 (8)
    The historical and technical background which lead to the development of 12 kHz channel spacing at u.h.f. is described. The advantages and disadvantages of the narrower channel spacing, including problems of achieving satisfactory adjacent channel protection and frequency stability, are discussed. A series of field tests within the London metropolitan area is reported which demonstrated that coverage and quality of reception is as good as with 25 kHz channel spacing.
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Method of synthesis of non-minimum-phase transfer functions for time-delay simulation
  • Author(s): B.D. Rakovich  and  B. Djurich
  • Source: Radio and Electronic Engineer, Volume 41, Issue 6, p. 273 –283
  • DOI:  10.1049/ree.1971.0086
  • Type: Article
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  • p. 273 –283 (11)
    The paper presents a new method for designing non-minimum phase rational approximants of the ideal delay function e−s suitable for the applications where the frequency spectrum of the input signal occupies large bandwidth. It is shown by theoretical considerations that for this purpose the most suitable type of delay characteristic is the one approximating to a constant delay over a frequency range extending from zero to a frequency ω < ωc and having a relatively large delay peak at the end of the passband (ωc). The amplitude of the initial transient ringing (precursor) and the overshoot in the transient response of the filter mainly depend on the value of the peak in the delay characteristic. The polynomials with two variable parameters that exhibit this type of delay response are then introduced and shown that the precursor and overshoot can be adjusted to any prescribed value by varying the free parameters. Extensive tables are presented enabling direct determination of the fourth-order transfer function with three right-half-plane zeros for almost any practical prescribed values of the precursor and overshoot. The method can be extended to higher-order networks and as an example a table containing data on the sixth-order functions with five right-half-plane zeros is also included. A comparison of the transient responses reveals that the technique proposed yields an improvement over all other methods so far described.
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The application of a synchronous switch for educational use
The problem of safe navigation in confined waters

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