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Online ISSN 1350-911X Print ISSN 0013-5194

Electronics Letters

Volume 6, Issue 17, 20 August 1970

Volumes & issues:

Volume 6, Issue 17

20 August 1970

Refraction and reflection of ultrasonic surface waves by thin-gold-film layers on lithium-niobate substrates
  • Author(s): M.E. Pedinoff  and  M. Waldner
  • Source: Electronics Letters, Volume 6, Issue 17, p. 533 –534
  • DOI:  10.1049/el:19700370
  • Type: Article
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  • p. 533 –534 (2)
    Acoustic-surface-wave phenomena similar to optical refraction and total internal reflection have been observed in thin metal prisms deposited on y cut lithium niobate. In addition, scattering of the surface waves has been observed both at the boundaries and interior of the gold-film prisms. The observed total internal reflection and refraction angles were found to agree with theoretical predictions.
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Spherical-harmonic expansions in near-field aerial problems
A priori stability guarantee for suboptimal-control designs
Langmuir-probe measurement of electron temperature in a flowing high-density plasma
  • Author(s): R.M. Clements  and  P.R. Smy
  • Source: Electronics Letters, Volume 6, Issue 17, p. 538 –539
  • DOI:  10.1049/el:19700373
  • Type: Article
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  • p. 538 –539 (2)
    Measurements with cooled double probes in a propane-air flame show that the measured electron temperature and the floating voltage of the probes can be strongly affected by variation of the probe temperature. Simple theoretical considerations indicate that these effects arise from cooling of the plasma electrons by collisions with cold molecules in the hydrodynamic boundary layer surrounding the probe.
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Attenuation of dispersive Rayleigh waves on quartz
On Wu's theory of microstrip
Adaptifon system for telephony — an alternative implementation of the Lincompex concept
Determination of the noise parameters of a linear 2-port
Decreasing antenna beamwidth with increasing scan angle
  • Author(s): R.C. Hansen
  • Source: Electronics Letters, Volume 6, Issue 17, p. 544 –545
  • DOI:  10.1049/el:19700378
  • Type: Article
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  • p. 544 –545 (2)
    All antennas, including phased arrays, exhibit beam broadening in the near field and also beam broadening in the far field at scan angles off broadside. For scan angles in the near field, the effective aperture is reduced, thereby producing less beam broadening due to the near field. At any scan angle, there is a near-field distance at which the broadside far-field beamwidth plus broadening equals the scan angle far-field beamwidth plus broadening. For larger scan angles, the beamwidth is less than at broadside. Calculations of this phenomenon are made for uniform linear and for tapered circular apertures.
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Stopping conditions for iterative control-function optimisation
Applicability of Kirchhoff integral to antenna near fields
  • Author(s): J.R. James
  • Source: Electronics Letters, Volume 6, Issue 17, p. 547 –549
  • DOI:  10.1049/el:19700380
  • Type: Article
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  • p. 547 –549 (3)
    The physical interpretation and subsequent application of Silver's formula to aperture fields containing surface waves is questioned. Using the more general Kirchhoff and Weber integrals, it is shown that the choice of the complex radial wavenumber k1 in these formulas must be consistent with the radial field decay; the formulas are therefore not applicable to composite fields having components with different radial decays. An antenna with a composite near field is described and the implications are discussed.
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Active filters and gain-bandwidth product
  • Author(s): E.A. Faulkner  and  J.B. Grimbleby
  • Source: Electronics Letters, Volume 6, Issue 17, p. 549 –550
  • DOI:  10.1049/el:19700381
  • Type: Article
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  • p. 549 –550 (2)
    For several active-filter configurations employing operational amplifiers, the variation of resonance frequency and Q factor is given as a function of the ratio of the resonance frequency to the gain-bandwidth product of the operational amplifier. Consideration of these equations leads to the choice of the Wien-bridge filter or its equivalents for applications requiring a high Q factor at high frequencies.
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Novel type of cut for KDP crystals for low-voltage light modulation
Effect of various gases on formative times of laser-triggered spark gap
  • Author(s): S.H. Khan  and  D. Walsh
  • Source: Electronics Letters, Volume 6, Issue 17, p. 551 –553
  • DOI:  10.1049/el:19700383
  • Type: Article
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  • p. 551 –553 (3)
    According to the streamer theory for the laser-triggered spark gap, gases with higher Townsend α coefficients and avalanche drift times. Thus faster switching was observed by using oxygen or air instead of nitrogen (in that order) or by increasing the amount of argon added to nitrogen. Clouding of the focusing lens was observed over a group of about 200 laser shots at 7 MW. No significant lens clouding was observed with 5 MW laser power, even after 1000 shots.
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Radiation resistance of a square loop in a warm plasma
  • Author(s): R.K. Gupta  and  I.L. Freeston
  • Source: Electronics Letters, Volume 6, Issue 17, p. 553 –554
  • DOI:  10.1049/el:19700384
  • Type: Article
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  • p. 553 –554 (2)
    A linearised hydrodynamic theory has been used to calculate the radiation resistance of a square-loop antenna in a warm plasma. It is suggested that cosinusoidal currents of two different propagation coefficients and amplitudes are simultaneously and independently present. Comparisons of the theoretical results with the measured values of the radiation resistance of a square-loop antenna on Ariel 3 satellite gives the ratio of the amplitudes of the currents in the two modes, for various values of the ratio of plasma to measuring frequency.
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Evidence for a correlation between discontinuities and filamentary conduction in the forward characteristic of diode thyristors
Adaptive equaliser for multipath channels
Electronic-network analysis by digital computer
Erratum: New equivalent circuits for elementary piezoelectric transducers
Erratum: Dielectric Green's function for parameters of microstrip

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