Online ISSN
1350-911X
Print ISSN
0013-5194
Electronics Letters
Volume 14, Issue 11, 25 May 1978
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Volume 14, Issue 11
25 May 1978
Concerning the maximum number of essential prime implicants in a Boolean function
- Author(s): Lorenzo Gómez-gonzález
- Source: Electronics Letters, Volume 14, Issue 11, page: 319 –319
- DOI: 10.1049/el:19780217
- Type: Article
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It is proved that the maximum number of essential prime implicants in a Boolean function with n variables is 2n−1, or the number of its canonic terms T if T is less than 2n−1.
U.H.F. low-noise GaAs m.e.s.f.e.t. amplifier for colour t.v. broadcasting translator
- Author(s): Masataka Mitama and Hidehiko Katoh
- Source: Electronics Letters, Volume 14, Issue 11, p. 319 –321
- DOI: 10.1049/el:19780218
- Type: Article
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–321
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Low-noise amplifiers for u.h.f. colour t.v. broadcasting translator use have been successfully developed by using 1 μm gate GaAs m.e.s.f.e.t.s. The obtained performances revealed that a GaAs m.e.s.f.e.t. has low-noise and low intermodulation distortion characteristics, even in the 500–800 MHz frequency range, compared with a Si bipolar transistor.
Efficient codes for single error detection and partial single error correction
- Author(s): A.H. Bhatt and L.L. Kinney
- Source: Electronics Letters, Volume 14, Issue 11, p. 321 –322
- DOI: 10.1049/el:19780219
- Type: Article
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–322
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Coding schemes are proposed for error control in systems where individual blocks of information are organised as two sub-blocks each requiring a different degree of error control. The codes described guarantee single error correction in one sub-block and provide single error detection and partial single error correction in the other. The main advantages are savings in redundancy and ability to use standard encoding/decoding procedures.
Multimode optical-fibre phase modulators and discriminators: I-theory
- Author(s): S.A. Kingsley and D.E.N. Davies
- Source: Electronics Letters, Volume 14, Issue 11, p. 322 –324
- DOI: 10.1049/el:19780220
- Type: Article
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Low-moded optical fibres are very microphonic when guiding highly coherent light. Acoustic signals applied to the fibre cause phase modulation of the optical carrier. This phase modulation is then converted to a related amplitude modulation by a fibredyne (fibre-optic self-homodyne) detection process at the photodiode. A simple theory is presented which describes the causes and characteristics of three p.m. to a.m. discriminator effects in coherent multimode fibre systems. Possible applications for fibredyne systems include data highways and low-fidelity distributed microphones.
Design of stochastic learning automata using adaptive digital logic elements
- Author(s): R.G. Neville ; C.R. Nicol ; P. Mars
- Source: Electronics Letters, Volume 14, Issue 11, p. 324 –326
- DOI: 10.1049/el:19780221
- Type: Article
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–326
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The hardware design of stochastic learning automata using adaptive digital logic elements is considered. Such techniques, based on digital stochastic computing, are shown to provide economical and fast learning-time computations. Experimental results are presented for a variety of linear learning algorithms.
Material dispersion in lightguide glasses
- Author(s): J.W. Fleming
- Source: Electronics Letters, Volume 14, Issue 11, p. 326 –328
- DOI: 10.1049/el:19780222
- Type: Article
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–328
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Material dispersion measurements are reported on six characteristic lightguide glass compositions. The measurements were made on bulk specimens and cover the wavelength range from 0.8 to 1.5 μm. It is observed that in these silicate glasses the wavelength at which material dispersion is zero is in all cases greater than 1.2μm.
New contact resistance profiling method for the assessment of III–V alloy multilayer structures
- Author(s): R.C. Goodfellow ; A.C. Carter ; R. Davis ; C. Hill
- Source: Electronics Letters, Volume 14, Issue 11, p. 328 –330
- DOI: 10.1049/el:19780223
- Type: Article
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–330
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A practical technique for the assessment of multilayer III–V structures is described which is based on the measurement of the contact resistance between a tungsten carbide probe and an angle lapped sample surface. The technique has been applied to homostructure and double heterostructure layers of GaAs, GaAlAs, InP and GaInAsP and quantitative information on the doping profiles has been obtained by calibration against binary material samples of known impurity levels.
Optical waveguides with low pulse dispersion over an extended spectral range
- Author(s): R. Olshansky
- Source: Electronics Letters, Volume 14, Issue 11, p. 330 –331
- DOI: 10.1049/el:19780224
- Type: Article
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–331
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A class of index profiles is described which can be used to minimise pulse dispersion over an extended range of wavelengths or at several different wavelengths. These profiles are compatible with standard waveguide compositions.
A note on the evaluation of Schottky diode parameters in the presence of an interfacial layer
- Author(s): S. Ashok ; J.M. Borrego ; R.J. Gutmann
- Source: Electronics Letters, Volume 14, Issue 11, p. 332 –333
- DOI: 10.1049/el:19780225
- Type: Article
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Metal-semiconductor barrier height and semiconductor doping concentration evaluated from room temperature current-voltage and capacitance-voltage data of Schottky barrier diodes exhibit significant error in the presence of an interfacial oxide layer of appreciable thickness (≥50 Å). The effective Richardson constant obtained from an activation energy plot of saturation current is shown to provide a sensitive indication of the presence of the interfacial layer.
Evaluation of nonperiodic autocorrelation parameters for maximal-length sequences
- Author(s): R. Skaug
- Source: Electronics Letters, Volume 14, Issue 11, p. 333 –335
- DOI: 10.1049/el:19780226
- Type: Article
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A spread-spectrum communication system using binary p.s.k. modulation often applies m-sequences as sub-baud codes for bandwidth expansion. In this situation one tries to minimise the probability of false synchronisation and prevent multipath distortion choosing sequences with suitable nonperiodic autocorrelation functions. Formulas for bounding the autocorrelation parameters are discussed. The letter also presents a table of ‘worst’ and ‘best’ m-sequences of period 15–1023.
Multimode optical fibre phase modulators and discriminators: II—Experiments
- Author(s): S.A. Kingsley
- Source: Electronics Letters, Volume 14, Issue 11, p. 335 –337
- DOI: 10.1049/el:19780227
- Type: Article
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p.
335
–337
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Low-moded coherent optical fibre systems are very microphonic. Any mechanical stress applied to the fibre causes phase modulation of the guided optical carrier, which is then converted to a related amplitude modulation by a fibredyne (fibre optic self-homodyne) detection process at the photodiode. In a companion letter, a simple theory was published which described the causes and characteristics of three p.m. to a.m. discriminator effects in multimode fibredyne systems. Experimental evidence for the two predominant p.m. to a.m. phenomena is presented and compared with the theory.
Photoelectric detector for daytime lightning
- Author(s): E.M. Thomson
- Source: Electronics Letters, Volume 14, Issue 11, p. 337 –339
- DOI: 10.1049/el:19780228
- Type: Article
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–339
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A wideband optical detector has been developed to determine the time characteristics of optical radiation from daytime lightning. A feature of the device is its ability to discriminate relatively low level long duration (500 ms) pulses due to lightning against a background illumination of up to 13,000 lx. This allows the characteristics of continuing currents to be investigated even in bright sunlit conditions.
Small toroidal antennas
- Author(s): T.S.M. Maclean and F. Rahman
- Source: Electronics Letters, Volume 14, Issue 11, p. 339 –340
- DOI: 10.1049/el:19780229
- Type: Article
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–340
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The radiation fields of small air-cored toroidal antennas carrying a uniform in-phase current have been evaluated. It is shown that according to whether the number of turns is one or more, different radiation patterns result. For the single turn toroid the position of its null axis can be adjusted by altering the ratio of its mean radius to the radius of its cross-section.
Two-way transmission experiments over a single optical fibre at the same wavelength using micro-optic 3 dB couplers
- Author(s): Kouichi Minemura ; Kohroh Kobayashi ; Tomoo Yanase ; Ro Ishikawa ; Minoru Shikada ; Atsufumi Ueki ; Shigetoki Sugimoto
- Source: Electronics Letters, Volume 14, Issue 11, p. 340 –342
- DOI: 10.1049/el:19780230
- Type: Article
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–342
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Two-way transmission of 10 Mb/s pulse signals at the same optical wavelength over a single 600 m optical fibre cable has been realise by employing newly developed small size and low loss micro-optic 3 dB couplers, GeAlAS l.e.d.s, a SELFOC® fibre cable, and conventional Si p.d.s and compact electronic circuits with TTL level interface.
Fast digital frequency synthesiser
- Author(s): M.J. Underhill ; P.A. Jordan ; M. Sarhadi
- Source: Electronics Letters, Volume 14, Issue 11, p. 342 –343
- DOI: 10.1049/el:19780231
- Type: Article
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–343
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A new phase-locked-loop type frequency synthesiser is described and tested which employs a digital-analogue convertor to give very rapid coarse frequency switching and optimum lock in speed anywhere in a wide frequency range. The experimental results are in good agreement with theory.
Contribution of reflector profile errors to antenna sidelobe radiation
- Author(s): A.B. Harris
- Source: Electronics Letters, Volume 14, Issue 11, p. 343 –345
- DOI: 10.1049/el:19780232
- Type: Article
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p.
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–345
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The validity of a simple formula for the level of sidelobe radiation due to profile errors in an antenna reflector has been verified by numerical evaluation of Ruze's integral. The statistical distribution of the sidelobes is discussed before the formula is applied to the practical case of large earth-station antennas. Profile errors may significantly impair the sidelobe performance of these antennas unless adequate tolerances are specified.
Optical wavelength-division multiplexer for the 1–1.4 μm spectral region
- Author(s): W.J. Tomlinson and Chinlon Lin
- Source: Electronics Letters, Volume 14, Issue 11, p. 345 –347
- DOI: 10.1049/el:19780233
- Type: Article
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–347
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An optical wavelength-division multiplexer, for multimode fibre transmission systems, has been demonstrated at λ ~ 1.1 μm. The device used a blazed reflection grating and a graded-refractive-index (g.r.i.n.) lens. The spectral response was measured using a tunable fibre Raman oscillator. The insertion loss was ≤2.6 dB, and the crosstalk level was ≤−29 dB. The device is compared to other multiplexers.
Fibre bundle comprising nineteen optical fibres drawn from the double crucible
- Author(s): H.A. Aulich ; J.G. Grabmaier ; K.H. Eisenrith
- Source: Electronics Letters, Volume 14, Issue 11, p. 347 –348
- DOI: 10.1049/el:19780234
- Type: Article
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–348
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A new technique of simultaneously drawing nineteen optical fibres from a double crucible is presented. Rotation of the crucible around its axis allows the fibres to be stranded during the drawing process. The fibres coated in-line with a silicone resin showed good cross-sectional symmetry and optical losses similar to those obtained in the single-fibre drawing process.
1.1 Gb/s pseudorandom pulse-code modulation of 1.27 μm wavelength c.w. InGaAsP/InP d.h. lasers
- Author(s): S.M. Abbott ; W.M. Muska ; T.P. Lee ; A.G. Dentai ; C.A. Burrus
- Source: Electronics Letters, Volume 14, Issue 11, p. 349 –350
- DOI: 10.1049/el:19780235
- Type: Article
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p.
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Pulse-code modulation of InGaAsP/InP d.h. injection lasers at a 1.1. Gb/s rate in a room-temperature environment has been demonstrated. The operating wavelength was 1.27 μm. Fabrication and characteristics of the lasers, design of the 1.1 Gb/s circuitry, and performance of the experimental transmitter are described briefly.
Erratum: Improving the large-signal models of bipolar transistors by dividing the intrinsic base into two lateral sections
- Author(s): H.-M. Rein
- Source: Electronics Letters, Volume 14, Issue 11, page: 350 –350
- DOI: 10.1049/el:19780236
- Type: Article
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