Online ISSN
1350-911X
Print ISSN
0013-5194
Electronics Letters
Volume 21, Issue 10, 9 May 1985
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Volume 21, Issue 10
9 May 1985
Ultra-high doping levels of GaAs with beryllium by molecular beam epitaxy
- Author(s): J.L. Lievin and F. Alexandre
- Source: Electronics Letters, Volume 21, Issue 10, p. 413 –414
- DOI: 10.1049/el:19850293
- Type: Article
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–414
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P-type doping levels up to 2×1020 at cm−3 in GaAs are presented using molecular beam epitaxy and beryllium as acceptor impurity. The epilayers present a perfect surface morphology and Be is not found to diffuse into the substrate, which permits the incorporation of such films into multilayer structures for device applications.
Approximation errors in the computation of Cheby̅shev expansion coefficients
- Author(s): A. Lepschy ; G.A. Mian ; U. Viaro
- Source: Electronics Letters, Volume 21, Issue 10, p. 414 –415
- DOI: 10.1049/el:19850294
- Type: Article
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–415
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Exact and approximate formulas for computing the Chebyÿshev expansion coefficients of a rational function are analysed. A simple expression is then given for evaluating the approximation errors of a classic numerical quadrature formula.
Fibre-optic polarising beam splitter employing birefringent-fibre coupler
- Author(s): I. Yokohama ; K. Okamoto ; J. Noda
- Source: Electronics Letters, Volume 21, Issue 10, p. 415 –416
- DOI: 10.1049/el:19850295
- Type: Article
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–416
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An in-line fibre-optic polarising beam splitter, consisting of a fused birefringent-fibre coupler, is reported. Splitting of the orthogonally polarised lights was accomplished by increasing the difference of coupling ratios for the two polarisation modes. When a light at 1.402 μm wavelength was coupled to the input lead, each polarisation was split on to different output leads, showing extinction ratios of more than 17 dB in both leads.
Ultra-low-noise, high-impedance preamp for cryogenic detectors
- Author(s): E.R. Brown
- Source: Electronics Letters, Volume 21, Issue 10, p. 417 –418
- DOI: 10.1049/el:19850296
- Type: Article
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A preamplifier design is presented which is based on a common-drain JFET input. The midband noise performance is En = 0.42 nV/Hz½, In = 2.8 fA/Hz½. The circuit has considerably less input capacitance than comparably noisy common-source amplifiers. It is particularly useful for preamplification of 0.1 to 10 MHz signals from liquid-helium-cooled radiation detectors.
High-power single-mode optical-fibre coupling to InGaAsP 1.3 μm mesa-structure surface-emitting LEDs
- Author(s): T. Uji and J. Hayashi
- Source: Electronics Letters, Volume 21, Issue 10, p. 418 –419
- DOI: 10.1049/el:19850297
- Type: Article
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–419
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High-power single-mode optical-fibre coupling to LEDs has been achieved by novel mesa-structure InGaAsP 1.3 μm surface-emitting LEDs. A −26.7 dBm (2.1 μW) fibre-coupled power has been obtained with 210 MHz optical −3 dB modulation bandwidth at 23°C 50 mA current. The 140 Mbit/s transmission feasibility over a single-mode optical fibre has been studied.
Wideband and high-gain negative-feedback AGC amplifier for high-speed lightwave digital transmission systems
- Author(s): K. Yamashita ; T. Kinoshita ; Y. Takasaki ; M. Maeda ; T. Kaji ; N. Maeda
- Source: Electronics Letters, Volume 21, Issue 10, p. 419 –420
- DOI: 10.1049/el:19850298
- Type: Article
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A negative-feedback AGC amplifier based on a new circuit configuration concept is proposed and monolithically integrated. The amplifier exhibits characteristics 2.5 times superior to those of the conventional AGC amplifier: 410 MHz bandwidth, 16 dB maximum gain and 18 dB gain dynamic range.
Dynamic channel allocation schemes for cordless telephones
- Author(s): F.A. Al-Salihi
- Source: Electronics Letters, Volume 21, Issue 10, p. 420 –422
- DOI: 10.1049/el:19850299
- Type: Article
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–422
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A comparison is made between the traffic capacity of two multichannel cordless telephone systems using different dynamic channel allocation schemes in their call set-up and termination procedures. One uses a dedicated control channel and the other uses any free channel for signalling purposes.
On-chip switching for DC parametric testing
- Author(s): A.J. Walton ; J.M. Robertson ; R. Holwill ; B. Moore
- Source: Electronics Letters, Volume 21, Issue 10, p. 422 –423
- DOI: 10.1049/el:19850300
- Type: Article
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–423
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The concept of on-chip switching for parametric testing of semiconductor processing is introduced. The feasibility of this approach is demonstrated for contact chain and diode-connected MOSFETs.
Broad-passband-width optical filter for multi/demultiplexer using a diffraction grating and a retroreflector prism
- Author(s): I. Nishi ; T. Oguchi ; K. Kato
- Source: Electronics Letters, Volume 21, Issue 10, p. 423 –424
- DOI: 10.1049/el:19850301
- Type: Article
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–424
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The letter describes the experimental results of a novel optical filter for a multi/demultiplexer using a diffraction grating and a retroreflector prism. A broader passband width, which is proportional to the difference between the prism base length and the input fibre core diameter, is obtained. The minimum insertion loss is 2.2 dB.
Inversion algorithm to construct Routh approximants
- Author(s): E. Kahoraho ; J.L. Gutierrez ; S. Dormido
- Source: Electronics Letters, Volume 21, Issue 10, p. 424 –426
- DOI: 10.1049/el:19850302
- Type: Article
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–426
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The purpose of the letter is to develop a direct method for deriving a kth-order Routh approximant, the main advantage being that, in order to find the parameters of a kth-order approximant, it will no longer be necessary to previously obtain those of all pth-order approximants (p≤k−1), as occurs with the Hutton and Friedland method (1975).
Substrate influence on flat folded dipole bandwidth
- Author(s): G. Dubost and A. Rabbaa
- Source: Electronics Letters, Volume 21, Issue 10, p. 426 –427
- DOI: 10.1049/el:19850303
- Type: Article
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–427
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The flat folded dipole has its largest bandwidth when low dielectric substrate is used, and when it acts at both third and fourth resonances. Theory and experiments are in good agreement.
Measurement of Gaussian beam diameter using ronchi rulings
- Author(s): M.A. Karim
- Source: Electronics Letters, Volume 21, Issue 10, p. 427 –429
- DOI: 10.1049/el:19850304
- Type: Article
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–429
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The analytical and experimental scope of the generalised Ronchi ruling method for the measurement of Gaussian laser beam diameter is presented. The effects of the ruling periodicity, ruling duty cycle, ruling type and the ruling contrast are considered.
Platinum intermetallic resistors for GaAs-based circuits
- Author(s): S. Tiwari and W.H. Price
- Source: Electronics Letters, Volume 21, Issue 10, p. 429 –430
- DOI: 10.1049/el:19850305
- Type: Article
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–430
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A simple technique for making intermetallic resistors of sheet resistance around 25 Ω/□ is described. The resistors were formed by reacting a 300 Å film of platinum with underlying GaAs to completion. PtGa, PtGa2 and PtAs2 phases were identified in the temperature range of 450°C to 550°C investigated. The temperature coefficient of resistivity was of the order of +9.2×10−4°C−1 at 25°C and the resistors appeared to be stable up to current densities of 105 A/cm2.
Improved switched-capacitor algorithmic analogue-to-digital convertor
- Author(s): H. Matsumoto and K. Watanabe
- Source: Electronics Letters, Volume 21, Issue 10, p. 430 –431
- DOI: 10.1049/el:19850306
- Type: Article
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–431
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A novel switched-capacitor circuit is presented for algorithmic analogue-to-digital conversion. Besides the reduced component count, the proposed circuit shows that it can accept a differential analogue signal. A conversion accuracy higher than 12 bits is easily attainable with its integrated version.
Determination of P-adic transform bases and lengths
- Author(s): Pei Soo-Chang and Wu Ja-Ling
- Source: Electronics Letters, Volume 21, Issue 10, p. 431 –432
- DOI: 10.1049/el:19850307
- Type: Article
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–432
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The P-adic transform bases and lengths can be easily determined by the Hensel code weight sums defined over a finite ring Pr. The maximum transform length is found to be Pr−1(P−1) instead of(P−1), it has much wider choice and is longer than before in terms of transform size.
Improved method of controlling stepping motor switching angle
- Author(s): R. Danbury
- Source: Electronics Letters, Volume 21, Issue 10, p. 432 –434
- DOI: 10.1049/el:19850308
- Type: Article
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–434
(3)
The letter describes a convenient method of controlling stepping motor switching angle which puts no limits on the range over which the angle can be varied. The description includes details of a practical implementation of the scheme.
OFDR diagnostics for fibre and integrated-optic systems
- Author(s): S.A. Kingsley and D.E.N. Davies
- Source: Electronics Letters, Volume 21, Issue 10, p. 434 –435
- DOI: 10.1049/el:19850309
- Type: Article
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–435
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Optical frequency-domain reflectometry (OFDR) shows promise as a diagnostic tool for high-resolution ranging in fibre/integrated-optic systems, and in high-resolution distributed fibre-optic sensors. We discuss some signal processing aspects of this technology, potential performance and application.
Optical system for real-time processing of multiple matrix product
- Author(s): H. Nakano and K. Hotate
- Source: Electronics Letters, Volume 21, Issue 10, p. 435 –437
- DOI: 10.1049/el:19850310
- Type: Article
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–437
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A novel optical system for real-time processing of a multiple matrix product is proposed. In this system, there is no scanning mechanism, and all of the N×N matrices to be multiplied have the N2 format. This system can easily be extended to that for multiplication of more than three matrices using a holographic unidirectionally diffusing screen. The preliminary experiments of multiplying three matrices based on this system is successfully demonstrated with a mean error of 4.7%.
Broadband circularly polarised planar array composed of a pair of dielectric resonator antennas
- Author(s): M. Haneishi and H. Takazawa
- Source: Electronics Letters, Volume 21, Issue 10, p. 437 –438
- DOI: 10.1049/el:19850311
- Type: Article
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–438
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A new type of planar array composed of a pair of dielectric resonator antennas has been devised and tested. Both the radiation patterns and ellipticity properties are presented. The 2 dB ellipticity bandwidth obtained was approximately 15% at X-band.
Photobleaching effect on visible-region loss increase for heat-treated optical fibres in a hydrogen atmosphere
- Author(s): K. Noguchi ; N. Uesugi ; N. Shibata ; K. Ishihara ; Y. Negishi
- Source: Electronics Letters, Volume 21, Issue 10, p. 438 –439
- DOI: 10.1049/el:19850312
- Type: Article
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–439
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The photobleaching effect on the visible-region loss increase due to hydrogen was observed for the first time by argon-ion laser light launching in fibres. A 660 nm fluorescence intensity reduction for the bleached fibres was also observed.
Dielectric switching with memory in thin films of stearic acid
- Author(s): W. Fulop and R. Ginige
- Source: Electronics Letters, Volume 21, Issue 10, p. 439 –441
- DOI: 10.1049/el:19850313
- Type: Article
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–441
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Stearic acid (CH3-CH216-COOH) films were deposited by thermal evaporation under vacuum. Thin-film capacitors were formed as aluminium-stearic acid-aluminium/gold structures. These devices exhibited dielectric memory switching between two stable states. This effect is analysed and discussed.
InGaAs photodiodes prepared by low-pressure MOCVD
- Author(s): P. Poulain ; M. Razeghi ; K. Kazmierski ; R. Blondeau ; P. Philippe
- Source: Electronics Letters, Volume 21, Issue 10, p. 441 –442
- DOI: 10.1049/el:19850314
- Type: Article
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InGaAs/InP double-heterostructure PIN photodiodes are demonstrated using the low-pressure MOCVD growth technique. Several types of detectors are reported, ranging from small-area ones suitable for PINFET implementation to broad-area general-purpose devices for both long- and short-wavelength applications. These diodes have performances equivalent to those obtained when using conventional growth techniques.
Switched predictor adaptation of DPCM-AQB speech coder using an imbedded vector quantisation
- Author(s): V. Ramamoorthy
- Source: Electronics Letters, Volume 21, Issue 10, p. 442 –444
- DOI: 10.1049/el:19850315
- Type: Article
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–444
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An adaptive differential pulse-code-modulation speech coder with a switched predictor adaptation scheme is described. The predictor adaptation is done by switching one of the several predetermined predictors stored both at the encoder and the decoder. The selection of the predictor is controlled by a vector quantiser. The tradeoff between the performance and the extra side information that needs to be transmitted is evaluated for bit rates of 16, 24 and 32 Kbit/s.
Software distribution via broadcast television signals
- Author(s): J. Billingsley and R.J. Billingsley
- Source: Electronics Letters, Volume 21, Issue 10, p. 444 –445
- DOI: 10.1049/el:19850316
- Type: Article
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A method is described for the transmission of software and digital data at rates of multiples of 500 baud as part of a broadcast television signal. Unlike teletext-based systems, this method enables signals to be recorded on a domestic video recorder for subsequent decoding. The receiver interface is also much simpler, consisting of low-cost, commonplace components in a configuration which can be assembled by novices.
Two-dimensional probability distribution of attenuation and depolarisation on Earth-space path
- Author(s): H. Fukuchi
- Source: Electronics Letters, Volume 21, Issue 10, p. 445 –447
- DOI: 10.1049/el:19850317
- Type: Article
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Two-dimensional probability distribution of attenuation and crosspolarisation discrimination (XPD) on Earth-space path at 19.5 GHz (circular polarisation) is derived. Moreover, the distribution is approximated by a mathematical function. The distribution is compared with the theoretical relationship between rain-induced attenuation and XPD, which is based on the deformed raindrop model. It is found that the measured attenuation and XPD values are distributed two-dimensionally in an attenuation-XPD plane, and the results cannot be explained by the theoretical relationship. This fact implies that special attention should be paid when the XPD statistics on the Earth-space path are predicted by the theoretical relationship between attenuation and XPD.
Planar InGaAs PIN photodiode with a semi-insulating InP cap layer
- Author(s): J.C. Campbell ; A.G. Dentai ; G.J. Qua ; J. Long ; V.G. Riggs
- Source: Electronics Letters, Volume 21, Issue 10, p. 447 –448
- DOI: 10.1049/el:19850318
- Type: Article
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We report a new planar InGaAs PIN photodiode structure which utilises a semi-insulating InP cap layer to achieve very low dark currents (id˜50 pA at −10 V, J = 5×10−7 A/cm2).
Selectively implanted oxygen isolation technology (SIO)
- Author(s): P. Ratnam and C.A.T. Salama
- Source: Electronics Letters, Volume 21, Issue 10, p. 448 –449
- DOI: 10.1049/el:19850319
- Type: Article
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–449
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A new isolation technology using selectively implanted oxygen into silicon is presented. The technique offers a five-fold reduction in the bird's beak as compared to the standard LOCOS process. Good interface characteristics are observed for the implanted oxide as well as for the active oxide grown between the implanted oxide regions. Electrical characteristics of n+/p diodes isolated by the implanted oxide are found to be comparable to that of LOCOS diodes.
InGaAs junction FETs with frequency limit (MAG = 1) above 30 GHz
- Author(s): R. Schmitt and K. Heime
- Source: Electronics Letters, Volume 21, Issue 10, p. 449 –451
- DOI: 10.1049/el:19850320
- Type: Article
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InGaAs JFETs were made by LPE growth of the n-channel and zinc diffusion from spin-on films at low temperatures for the p+-gate. Extrinsic transconductances in excess of 100 mS/mm for gate lengths of 1.2 μm and frequency limits (MAG = 1) above 30 GHz were obtained. The good agreement between experimentally determined data and those calculated from material parameters and device dimensions indicates that a low temperature and/or short time process for gate formation is a necessary prerequisite in InGaAs JFET technology.
Nonequilibrium devices for infra-red detection
- Author(s): T. Ashley and C.T. Elliott
- Source: Electronics Letters, Volume 21, Issue 10, p. 451 –452
- DOI: 10.1049/el:19850321
- Type: Article
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To increase the operating temperature of long-wavelength infra-red detectors it is proposed that narrow-gap semiconductor devices be operated in a nonequilibrium mode such that the carrier densities are held below their equilibrium, near-intrinsic, levels. The possible use of exclusion in photo-conductors and extraction in photodiodes is discussed, and experimental results are shown for the former.
Variable-length shift register
- Author(s): K. Nagaraj and K. Singhal
- Source: Electronics Letters, Volume 21, Issue 10, p. 452 –453
- DOI: 10.1049/el:19850322
- Type: Article
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A new implementation for a variable-length shift register is described. It employs two unidirectional MOS dynamic shift registers. The length of the shift register can be selected by programming the clock signals suitably.
New ν(E) relationship for GaAs
- Author(s): Y.-K. Feng
- Source: Electronics Letters, Volume 21, Issue 10, p. 453 –454
- DOI: 10.1049/el:19850323
- Type: Article
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A new ν(E) relationship of GaAs has been developed, in which the nonequilibrium transport effects (or velocity overshoot effects) of electrons were included. It was observed that the peak electric field Ep, corresponding to the average peak electron velocity νp, and the saturation electron velocity νs increase with shortening of the length of GaAs devices, and that Ep decreases slightly with the decrease of the lattice temperature To.
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