Online ISSN
1350-911X
Print ISSN
0013-5194
Electronics Letters
Volume 14, Issue 25, 7 December 1978
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Volume 14, Issue 25
7 December 1978
Improving the efficiency of Sammon's nonlinear mapping by using clustering archetypes
- Author(s): C.E. Pykett
- Source: Electronics Letters, Volume 14, Issue 25, p. 799 –800
- DOI: 10.1049/el:19780539
- Type: Article
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–800
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Sammon's nonlinear mapping technique is discussed and certain inefficiencies are highlighted. It is shown how the algorithm can be streamlined by using appropriately chosen cluster archetypes. This results in reductions in storage requirements and in execution time, the latter by at least an order of magnitude.
Simple iterative method for overcoming errors due to heating of current-measuring shunts
- Author(s): C.R. Melbourne and M.R. Barrault
- Source: Electronics Letters, Volume 14, Issue 25, p. 800 –802
- DOI: 10.1049/el:19780540
- Type: Article
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A simple numerical method is given that describes how to obtain the true current pulse from the signal of a shunt heated during the passage of the current pulse.
Nondestructive determination of refractive-index profile of an optical fibre: forward light scattering method
- Author(s): C. Saekeang and P.L. Chu
- Source: Electronics Letters, Volume 14, Issue 25, p. 802 –804
- DOI: 10.1049/el:19780541
- Type: Article
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802
–804
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A nondestructive technique is presented for determining the refractive-index profile of an optical fibre from its forward-scattered pattern arising from a normally incident laser beam. This method does not require any index-matching liquid and is not limited to single-mode fibres. It uses as essential information only the angular positions of the extrema in the measured pattern.
Short thin-wire antenna to measure the horizontal electric-field component at v.l.f. on the Earth's surface
- Author(s): David V. Thiel
- Source: Electronics Letters, Volume 14, Issue 25, p. 804 –805
- DOI: 10.1049/el:19780542
- Type: Article
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804
–805
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A short insulated thin-wire antenna lying on the surface of the earth is shown to be a valid probe of the horizontal electric-field component of a v.l.f. signal at the surface. The input impedence of such an antenna is virtually independent of the electrical characteristics of the local earth.
Microwave match of low-impedance thin-film Josephson junctions
- Author(s): J.H. Hinken
- Source: Electronics Letters, Volume 14, Issue 25, p. 805 –806
- DOI: 10.1049/el:19780543
- Type: Article
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It is demonstrated how a thin-film low-impedance Josephson junction can be matched in a rectangular waveguide at 9 GHz, thus reducing the necessary power in voltage standard applications by a factor of 250. The method is also applicable to higher frequencies and to microwave devices such as detectors and mixers.
Multilevel signals in digital optical-fibre communications
- Author(s): Rade Petrović
- Source: Electronics Letters, Volume 14, Issue 25, p. 806 –808
- DOI: 10.1049/el:19780544
- Type: Article
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806
–808
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The theory for multilevel signal applications in digital optical-fibre communications is derived for systems with avalanche and nonavalanche photodetectors. It is shown that a multilevel signal can significantly increase the information rate and/or the repeater spacing. At the same time equaliser design can be simplified.
Low-loss Y-coupler for multimode single fibres
- Author(s): L. Fiorina ; S. Mezzetti ; F. Svelto
- Source: Electronics Letters, Volume 14, Issue 25, p. 808 –809
- DOI: 10.1049/el:19780545
- Type: Article
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A technique for making low-loss 3dB Y-couplers in multimode single fibres was developed and evaluated. The couplers were obtained by the fusion of two optical fibres by means of a neated Kantal wire. A set of fifty samples using a Pilkington step-index fibre showed an average excess insertion loss of about 0.7dB.
Semiconductor-laser self pulsing due to deep level traps
- Author(s): John A. Copeland
- Source: Electronics Letters, Volume 14, Issue 25, p. 809 –810
- DOI: 10.1049/el:19780546
- Type: Article
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809
–810
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By adding a rate equation for the charge state of deep-level traps to the rate equations for electron and photon density, it is shown that the observed self pulsing observed in semiconductor lasers can be due to the presence of deep-level traps with less than 1017 cm−3 density.
Parallel-beam excitation method for estimating refractive-index profiles in optical fibres
- Author(s): A. Ankiewicz ; M.J. Adams ; D.N. Payne ; F.M.E. Sladen
- Source: Electronics Letters, Volume 14, Issue 25, p. 811 –812
- DOI: 10.1049/el:19780547
- Type: Article
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A theoretical model is developed that demonstrates the presence of a ring in the far-field pattern when a graded-index fibre is excited by a collimated beam, incident at a given radius from the core centre. The angular position of tnis ring can be used to obtain an estimate of the fibre refractive-index profile, provided a correction for the finite beam spot size is applied.
Current-tuned GaAs Schottky-barrier Impatt diodes for 60–96 GHz operation
- Author(s): Robert I. Schawarz and Ernst Bonek
- Source: Electronics Letters, Volume 14, Issue 25, p. 812 –814
- DOI: 10.1049/el:19780548
- Type: Article
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812
–814
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Oscillation of GaAs single-drift Schottky-barrier Impatt diodes mounted in a full-height IEC-R740 waveguide (3.1 × 1.55 mm2) has been observed between 60 and 96 GHz in pulsed operation. By bias-current tuning, a range of up to 19 GHz was covered with a single diode.
Multirate multiplierless discrete ladder filters
- Author(s): L.T. Bruton and R.H. Khan
- Source: Electronics Letters, Volume 14, Issue 25, p. 814 –815
- DOI: 10.1049/el:19780549
- Type: Article
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Multirate discrete ladder filter structures are proposed that, when implemented as a digital filter, achieve better passband accuracy than the corresponding uniform-rate filter and, of more importance, may be implemented without the use of digital multipliers and consequently with simpler hardware and reduced filter processing times.
Long-term lifetests of c.w. (AlGa)As laser diodes at room temperature
- Author(s): M. Ettenberg ; H. Kressel ; I. Ladany
- Source: Electronics Letters, Volume 14, Issue 25, p. 815 –816
- DOI: 10.1049/el:19780550
- Type: Article
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–816
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Real-time lifetest data are given for a group of c.w. laser diodes operated continuously for periods as long as 4 years. Out of 24 lasers studied, four lasers have failed to date. This failure rate is compared with accelerated lifetests at 70°C; an estimated m.t.t.f. of ≈ 105 hours at room temperature is obtained.
Compact optical circulator for near-infrared region
- Author(s): Atsushi Shibukawa and Morio Kobayashi
- Source: Electronics Letters, Volume 14, Issue 25, p. 816 –817
- DOI: 10.1049/el:19780551
- Type: Article
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816
–817
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A compact Faraday-rotation 4-port circulator was developed for the near-infrared region. This circulator consists of an yttrium-iron-garnet Faraday rotator, biased by two permanent magnets, and two Glan-Taylor prisms. Insertion losses of 2.7–3.2 dB and isolation ratios of 13–28 dB among non-reciprocal ports were obtained at 1.15μm wavelength.
Distortion-induced d.c. offset analysis using Volterra-Wiener series approach
- Author(s): A. Borys
- Source: Electronics Letters, Volume 14, Issue 25, p. 817 –818
- DOI: 10.1049/el:19780552
- Type: Article
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817
–818
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It is shown that the Volterra-Wiener series approach is an attractive tool for the analysis of the distortion-induced d.c. offset. A differential input stage of an operational amplifier is taken into account as an example.
New estimate of the minimum noise figure of a m.e.s.f.e.t.
- Author(s): C.R. Brewitt-Taylor ; P.N. Robson ; J.E. Sitch
- Source: Electronics Letters, Volume 14, Issue 25, p. 818 –820
- DOI: 10.1049/el:19780553
- Type: Article
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p.
818
–820
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New estimates of the drain and gate noise multiplication parameters, the correlation coefficient and the minimum noise figure for a m.e.s.f.e.t. are advanced. For an uncooled GaAs m.e.s.f.e.t. having a 1 μm gate length, a minimum possible noise figure of 1 dB at 10 GHz is predicted. InP is only marginally better.
Generalised disturbance adaptive optimal regulator
- Author(s): S. Mukhopadhyay
- Source: Electronics Letters, Volume 14, Issue 25, p. 820 –821
- DOI: 10.1049/el:19780554
- Type: Article
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820
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In the present work, choosing a varying output weighting matrix, an optimal regulator having state feedback terms with variable gain and feed-forward terms dependent on input as well as output disturbances has been proposed.
P.I.D. equivalent of optimal regulator
- Author(s): S. Mukhopadhyay
- Source: Electronics Letters, Volume 14, Issue 25, p. 821 –822
- DOI: 10.1049/el:19780555
- Type: Article
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In this work an optimal regulator for linear systems has been realised indirectly in terms of the proportional, integral and derivative of the measurable outputs of the system.
Wideband near-i.r. continuum (0.7–2.1 μm) generated in low-loss optical fibres
- Author(s): Chinlon Lin ; V.T. Nguyen ; W.G. French
- Source: Electronics Letters, Volume 14, Issue 25, p. 822 –823
- DOI: 10.1049/el:19780556
- Type: Article
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822
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A wideband near-infrared continuum is obtained by nonlinear optical interactions in low-loss single-mode and multimode silica fibres pumped by pulses from a Q-switched Nd:y.a.g. laser. With 50 kW pump power coupled into a 315 m long 33 μm core-diameter low-loss multimode fibre, a continuum spanning the spectral range 0.7–2.1 μm with a total power of 12 kW is generated. In single-mode and low-mode-number fibres a similar continuum of lower power has been obtained. Such continuum sources are useful for measurement of fibre properties as well as for spectroscopic study of other optical materials.
Legendre tapers
- Author(s): P.A. Massaro and V. Picciarelli
- Source: Electronics Letters, Volume 14, Issue 25, p. 823 –824
- DOI: 10.1049/el:19780557
- Type: Article
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A new class of tapered lines using Legendre polynomials is discussed. The main advantage of such a device is the high value of the major/minor lobes ratio for the reflection coefficient, especially for frequencies much higher than the cutoff value.
Very low noise mixer at 115 GHz using a Mott diode cooled to 20 K
- Author(s): Nigel Keen ; Robert Haas ; Eduard Perchtold
- Source: Electronics Letters, Volume 14, Issue 25, p. 825 –826
- DOI: 10.1049/el:19780558
- Type: Article
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Measurements on a cooled resistive mixer are reported using a Mott-barrier diode cooled to 20 K, operating at 115 GHz and pumped with a local oscillator power as low as 150 μW. The mixer noise temperature of 200 K is not only the lowest reported for a resistive mixer above 90 GHz but indicates that some improvement in shot-noise models for resistive mixers is desirable.
Reflection of electromagnetic wave from a time-varying medium
- Author(s): Shogo Kozaki
- Source: Electronics Letters, Volume 14, Issue 25, p. 826 –828
- DOI: 10.1049/el:19780559
- Type: Article
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For the purpose of radiowave propagation in the ionosphere, in a plasma and in other media, the reflection and transmission of an electromagnetic wave from a suddenly changed conductivity, when a plane wave is normally incident upon an interface separating two conducting media, are studied. The field expressions are exactly obtained through the use of the Laplace transform. The discussion is primarily on the time behaviour of the reflected wave.
Realisation of single-resistance-controlled lossless floating inductance
- Author(s): Raj Senani
- Source: Electronics Letters, Volume 14, Issue 25, p. 828 –829
- DOI: 10.1049/el:19780560
- Type: Article
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828
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A new active RC circuit is proposed for the realisation of lossless floating inductance employing three operational amplifiers as unity-gain summers, three external resistors and a single grounded capacitor. Unlike other existing three-amplifier and two-amplifier circuits for lossless floating inductance, the new circuit realises an inductance that is controllable through a single resistor.
Initial observations of optical injection locking of an X-band Impatt oscillator
- Author(s): A.J. Seeds and J.R. Forrest
- Source: Electronics Letters, Volume 14, Issue 25, p. 829 –830
- DOI: 10.1049/el:19780561
- Type: Article
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An experiment is described in which the output of a GaAlAs laser, modulated at 2.6 GHz, was used to optically sub-harmonic injection lock a 7.8 GHz Impatt oscillator. A locking range of 1 MHz was achieved and means are suggested by which this may be increased substantially.
Remediable and nonremediable causes of parasitic elements in InP m.e.s.f.e.t.s
- Author(s): T. Wada and Jeffrey Frey
- Source: Electronics Letters, Volume 14, Issue 25, p. 830 –832
- DOI: 10.1049/el:19780562
- Type: Article
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Two-dimensional analyses of InP and GaAs m.e.s.f.e.t. structures are used to qualitatively explain relative magnitudes of parasitic element values observed in experimental InP m.e.s.f.e.t.s. Large drain-gate capacitance observed in InP is attributed mainly to substrate conduction, whereas large drain conductance at certain drain biases in InP may be unavoidable due to large velocity dropback and large high-field diffusion in this material. Low Schottky-barrier height and substrate conduction also increase gD
Simulation of inductors and capacitors using operational-amplifier compensation pole: a caution
- Author(s): Barrie Gilbert
- Source: Electronics Letters, Volume 14, Issue 25, page: 832 –832
- DOI: 10.1049/el:19780563
- Type: Article
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Repeatability of computer-corrected network-analyser measurements of reflection coefficients
- Author(s): E.F. da Silva and M.K. McPhun
- Source: Electronics Letters, Volume 14, Issue 25, p. 832 –834
- DOI: 10.1049/el:19780564
- Type: Article
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Practical results relating to the accuracy of 100 sets of repeated reflection-coefficient measurements using a computer-corrected network analyser are given. Statistical data based on the above sets of measurements are presented. The results show that measurement accuracies of 1% can be predicted with a confidence level of 99%. A method of dealing with the possible occurrence of ‘rogue’ measurements is discussed.
Erratum: Computer studies on the widening of the avalanche zone and the decrease in efficiency of silicon X-band symmetrical double-drift impatt diodes at high current densities
- Author(s): M. Sridharan and S.K. Roy
- Source: Electronics Letters, Volume 14, Issue 25, page: 834 –834
- DOI: 10.1049/el:19780565
- Type: Article
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Erratum: General analysis of nonmonotonic lowpass filters having multiple pairs of imaginary-axis zeros with weighted least-mean-square error characteristic
- Author(s): Dang Tan Phuc and J. Attikiouzel
- Source: Electronics Letters, Volume 14, Issue 25, page: 834 –834
- DOI: 10.1049/el:19780566
- Type: Article
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