Online ISSN
1350-911X
Print ISSN
0013-5194
Electronics Letters
Volume 5, Issue 21, 16 October 1969
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Volume 5, Issue 21
16 October 1969
Natural conduction and thermal-activation energy in chlorobenzene and bromobenzene
- Author(s): P. Prabhakara Rao and G.R. Govinda Raju
- Source: Electronics Letters, Volume 5, Issue 21, p. 507 –508
- DOI: 10.1049/el:19690382
- Type: Article
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Natural conduction in chlorobenzene and bromobenzene has been measured for field strengths of 50 V/cm to 50 kV/cm with brass electrodes. The conduction current is found to be caused by the injection of electrons into the liquid from the cathode. The thermal activation energy is 0.61 eV for chlorobenzene and 0.41 eV for bromobenzene.
Periodically modulated dielectrically filled waveguide as a microwave antenna
- Author(s): P. Balling
- Source: Electronics Letters, Volume 5, Issue 21, p. 508 –510
- DOI: 10.1049/el:19690383
- Type: Article
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p.
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Complex solutions to a determinantal equation have been found numerically and employed to predict the properties of a frequency-scanning forward-radiating antenna obtained through a superposition of two waves propagating in oblique angles on an infinite periodic structure. The range of parameters of a usable antenna has been examined.
Focal-plane field distribution of parabolic reflectors
- Author(s): A.W. Rudge
- Source: Electronics Letters, Volume 5, Issue 21, p. 510 –512
- DOI: 10.1049/el:19690384
- Type: Article
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The principal component of the parabolic-reflector focal-plane electric-field distribution is derived from scalar wave theory in a form providing a simple analytic representation of the field in terms of available tabulated functions not restricted to large focal-length/diameter ratios.
Experimental investigation of the input-impedance characteristics of an antenna in a rectangular waveguide
- Author(s): M.J. Al-Hakkak
- Source: Electronics Letters, Volume 5, Issue 21, p. 513 –514
- DOI: 10.1049/el:19690385
- Type: Article
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513
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The input impedance of a monopole antenna in a rectangular waveguide is investigated experimentally. It is found that theoretical results based on the assumption of a sinusoidal current distribution are in good agreement for monopole lengths up to about 0.6 of the guide height and about 1/4 λ0. For longer monopoles, a more accurate theory should be sought.
Floating-drive circuit for f.e.t. switches
- Author(s): I.D.G. Macleod
- Source: Electronics Letters, Volume 5, Issue 21, page: 515 –515
- DOI: 10.1049/el:19690386
- Type: Article
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515
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A simple circuit which facilitates the provision of a floating-drive waveform for an analogue f.e.t. switch is described. Rise and fall times in this waveform of less than a microsecond and decay times of greater than a second are readily achieved.
Orthogonal decomposition of the 2-port network
- Author(s): A.W. Keen and Jacqueline L. Glover
- Source: Electronics Letters, Volume 5, Issue 21, p. 515 –517
- DOI: 10.1049/el:19690387
- Type: Article
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An investigation is made into the geometrical aspect of the immittance transformation properties of the general 2-port network. Its transmission matrix is decomposed to reveal orthogonal components which represent rotation and/or reflection of the load in the v/t plane, thereby obtaining new insight into the general immittance transformation process.
Parameters of microstrip
- Author(s): J.A. Weiss and T.G. Bryant
- Source: Electronics Letters, Volume 5, Issue 21, p. 517 –518
- DOI: 10.1049/el:19690388
- Type: Article
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The program computes the capacitance, effective permittivity, characteristic impedance and phase velocity of single strips, and of the normal modes of coupled pairs of strips, in an approximation in which the longitudinal components of the fields and the thickness of the conducting strips are neglected. Within this model, the inhomogeneous dielectric is treated in a rigorous manner.
Acoustoelectric interactions in cadmium-sulphide thin films
- Author(s): I.M. Mason
- Source: Electronics Letters, Volume 5, Issue 21, p. 519 –520
- DOI: 10.1049/el:19690389
- Type: Article
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p.
519
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High-field photocurrent saturation and noise generation in a heat-treated CdS thin film is attributed to incoherent surfacewave amplification in the presence of field-enhanced trapping.
Accurate trimming of active rc filters by means of phase measurements
- Author(s): K. Mossberg and D. Åkerberg
- Source: Electronics Letters, Volume 5, Issue 21, p. 520 –521
- DOI: 10.1049/el:19690390
- Type: Article
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A method is described for accurate determination of the locations of poles and zeroes of a transfer function by means of phase measurements. It is especially suitable for trimming of second-degree active RC networks.
Output spectrum of IMPATT-diode oscillators
- Author(s): M.T. Vlaardingerbroek
- Source: Electronics Letters, Volume 5, Issue 21, p. 521 –522
- DOI: 10.1049/el:19690391
- Type: Article
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The width of the output spectrum of an IMPATT-diode oscillator, operating at low- and intermediate-output levels, is calculated. It depends on the power-density spectrum of the primary noise current, introduced by Hines, at the oscillation frequency. Low-frequency components of this noise current give rise to an additional modulation of the centre frequency of the output spectrum.
Performance of two types of log-periodic microwave circuit
- Author(s): B.G. Evans
- Source: Electronics Letters, Volume 5, Issue 21, p. 522 –524
- DOI: 10.1049/el:19690392
- Type: Article
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522
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The principle of log-periodicity is extended to microwave components, the performance of impedance transformers and stub filters being investigated. The general nonoptimum nature of log-periodic components is demonstrated, and some novel amplitude/phase characteristics of a log-periodic stub filter are presented.
Circular resonant structures in microstrip
- Author(s): J. Watkins
- Source: Electronics Letters, Volume 5, Issue 21, p. 524 –525
- DOI: 10.1049/el:19690393
- Type: Article
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524
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Mode patterns of circular disc resonant sections are analysed. Radiation losses are expected to be small for the dominant mode, which would therefore have the highest Q value.
Second-order spin-wave instability in Mn-Zn2Y planar hexagonal ferrites
- Author(s): J. Helszajn and J. Mcstay
- Source: Electronics Letters, Volume 5, Issue 21, p. 525 –526
- DOI: 10.1049/el:19690394
- Type: Article
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The letter describes some measurements of the decline of the main resonance under 2nd-order pumping in an Mn-Zn2Y single-crystal hexagonal ferrite biased in the easy plane. Measurements were carried out with the r.f. field in the easy plane and also with the r.f. field perpendicular to it. The ratio of the two responses in the linear region is e02, which is the ratio of the susceptibilities for the two excitations. The ratio of the two r.f. threshold fields is also approximately e. Here e02 is the uniform-mode ellipticity. For the samples used, the critical r.f. threshold field was 41A/m in the easy plane and the spinwave linewidth was 565A/m.
Field-effect transistors with arbitrary charge distributions in the gate and in the channel
- Author(s): M. Dierckens
- Source: Electronics Letters, Volume 5, Issue 21, p. 526 –527
- DOI: 10.1049/el:19690395
- Type: Article
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The expressions for drain current, mutual transconductance and output conductance of a junction f.e.t. below pinchoff, given by Bockemuehl, are generalised to structures where the gate doping profile is arbitrary and where the depletion region penetrates also in the gate region.
Low-sensitivity easily trimmed standard building block for active rc filters
- Author(s): D. Åkerberg and K. Mossberg
- Source: Electronics Letters, Volume 5, Issue 21, p. 528 –529
- DOI: 10.1049/el:19690396
- Type: Article
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p.
528
–529
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Four building blocks have been found that realise the biquadratic transfer functionT(s)=Ks2 + 2σos + ωoo2/s2 + 2σps + ωop2with very low sensitivities to variations in the passive and active components, and with the possibility of trimming σo, ωoo, σop and ωop independently each by one resistor. The networks may be manufactured in standardised integrated blocks which may be trimmed for specific applications.
Evidence of parametric conversion in the frequencies of acoustic domains in CdS
- Author(s): G.I. Robertson and M.B.N. Butler
- Source: Electronics Letters, Volume 5, Issue 21, p. 529 –530
- DOI: 10.1049/el:19690397
- Type: Article
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529
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Under certain conditions, low-frequency components of an acoustic domain are seen to increase in amplitude after removal of the drive field. This effect is thought to be caused by parametric conversion.
p-level sequences with primitive autocorrelation functions
- Author(s): H.A. Barker
- Source: Electronics Letters, Volume 5, Issue 21, p. 531 –532
- DOI: 10.1049/el:19690398
- Type: Article
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531
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The general conditions under which a transformation of a p-level m-sequence yields a sequence with a primitive auto-correlation function are derived. Specific results are given for 3<p<13.
Improved method of solution of 2-point boundary-value problems arising in optimal control
- Author(s): A. Griffin
- Source: Electronics Letters, Volume 5, Issue 21, p. 532 –533
- DOI: 10.1049/el:19690399
- Type: Article
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532
–533
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The letter outlines the existing methods of solution for the 2-point boundary-value problem arising from the use of Pontryagin's maximum principle. It then describes an improved method which combines the advantages of two other methods of solution.
Charging time of a high-voltage impulse generator
- Author(s): G.W. Swift
- Source: Electronics Letters, Volume 5, Issue 21, page: 534 –534
- DOI: 10.1049/el:19690400
- Type: Article
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For design and operation, it is useful to know the charging behaviour of high-voltage impulse generators. The problem is one of finding the sum of the voltages along a uniform RC line as a function of time, for a step input. It is shown that the response is very nearly a simple exponential curve having a time constant (2/π)3 times the total RC product for the line.
Novel technique for measuring the Q factor of thin-film lumped elements at microwave frequencies
- Author(s): J.J. Hughes ; L.S. Napoli ; W.F. Reichert
- Source: Electronics Letters, Volume 5, Issue 21, p. 535 –536
- DOI: 10.1049/el:19690401
- Type: Article
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p.
535
–536
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Using higher-order resonances, it is possible to determine the Q factors of thin-film lumped elements at microwave frequencies. This technique avoids any perturbation of the experimental arrangement which normally arises from insertion and removal of the unknown.
Field dependence of ionisation rates of electrons in silicon
- Author(s): S. Ahmad and W.S. Khokle
- Source: Electronics Letters, Volume 5, Issue 21, p. 536 –537
- DOI: 10.1049/el:19690402
- Type: Article
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536
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A theoretical model for the ionisation coefficient of electrons in silicon has been developed based on the solution of the Boltzmann transport equation. Analytic expressions are obtained for the ionisation coefficient and the drift velocity. Modifications in the deformation potential constants have been suggested for obtaining a fit to the experimentally observed results for the drift velocity and ionisation coefficient. The mean free path for ionisation calculated with the help of this model fits well with the earlier predictions.
Use of inverse Karnaugh maps in realisation of logic functions
- Author(s): F.C. Evans
- Source: Electronics Letters, Volume 5, Issue 21, p. 537 –538
- DOI: 10.1049/el:19690403
- Type: Article
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p.
537
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The dual form of the commonly used Karnaugh map has certain advantages when it is required to minimise a logical function, particularly if the function is to be realised by means of NAND gates making use of the ‘wired-OR’ connection.
Input synthesis for minimum covariance state and parameter estimation
- Author(s): G.C. Goodwin
- Source: Electronics Letters, Volume 5, Issue 21, p. 539 –540
- DOI: 10.1049/el:19690404
- Type: Article
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539
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An input signal is synthetised which minimises the covariance of the error in the estimates of the parameters and states of a dynamic process. The method is applicable as long as the noise is approximately white and initial estimates of parameters and states are available.
Propagation characteristics of magnetoelastic surface wave
- Author(s): J.P. Parekh
- Source: Electronics Letters, Volume 5, Issue 21, p. 540 –541
- DOI: 10.1049/el:19690405
- Type: Article
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The propagation characteristics of a magnetoelastic surface wave in ferrites are described using numerical calculations pertinent to gallium-y.i.g.
Ray method for scattering by small discontinuities in a waveguide
- Author(s): L.B. Felsen
- Source: Electronics Letters, Volume 5, Issue 21, page: 542 –542
- DOI: 10.1049/el:19690406
- Type: Article
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As an improvement on the conventional induced-dipolemoment calculation, a ray-optical method is advocated which provides for obstacle-wall interaction and is not invalidated by short-wavelength approximations. Possible applications to other propagation problems are listed.
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