Online ISSN
1350-911X
Print ISSN
0013-5194
Electronics Letters
Volume 19, Issue 17, 18 August 1983
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Volume 19, Issue 17
18 August 1983
Negative differential resistance in GaAs MESFETs
- Author(s): T.A. Fjeldly and J.S. Johannesson
- Source: Electronics Letters, Volume 19, Issue 17, p. 649 –650
- DOI: 10.1049/el:19830441
- Type: Article
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The occurrence of stationary domains and negative differential resistance in GaAs MESFETs is shown to be favoured for a certain range of combinations of pinch-off voltage, gate voltage and saturation voltage. Outside this range the transistor either shows instability or normal JFET behaviour. The predictions are in good agreement with available experimental data.
Fitting of a weighted Gaussian lowpass filter to the transfer function of graded-index fibres to reduce bandwidth ambiguities
- Author(s): D. Schicketanz
- Source: Electronics Letters, Volume 19, Issue 17, p. 650 –652
- DOI: 10.1049/el:19830442
- Type: Article
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It is proposed to fit a weighted Gaussian lowpass filter to the transfer function of graded-index fibres to reduce the error in bandwidth value.
Linewidth of a single mode in a multimode injection laser
- Author(s): M.J. Adams
- Source: Electronics Letters, Volume 19, Issue 17, p. 652 –653
- DOI: 10.1049/el:19830443
- Type: Article
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An expression is derived for the quantum noise-limited line-width of each individual mode in a multimode laser. Numerical calculations show that the mode linewidth of a two-mode 1.55 μm laser is only about 10% larger than that in a single-mode device.
Laser-beam attenuation measurement using acousto-optic modulator
- Author(s): T. Kawakami and I. Yokoshima
- Source: Electronics Letters, Volume 19, Issue 17, p. 653 –654
- DOI: 10.1049/el:19830444
- Type: Article
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A laser-beam attenuation-measurement method using the first-order diffraction from an acousto-optic modulator is newly developed. The attenuation is determined from the voltage of the 30 MHz driving signal of the modulator. A value of attenuation of more than 50 dB can be measured at 633 nm.
Joint-loss dependence on mismatch parameters in graded-index optical fibres
- Author(s): G. Coppa ; P. di Vita ; U. Rossi
- Source: Electronics Letters, Volume 19, Issue 17, p. 654 –656
- DOI: 10.1049/el:19830445
- Type: Article
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The dependence of the mean value and the RMS joint-loss distribution on geometrical and optical parameters deduced in practical cases by simple and compact formulas. The different sensitivities of the various parameters can suggest different, more advantageous choices of the tolerance set.
Wavelength tuning of GaInAsP/InP integrated laser with butt-jointed built-in distributed Bragg reflector
- Author(s): Y. Tohmori ; Y. Suematsu ; H. Tsushima ; S. Arai
- Source: Electronics Letters, Volume 19, Issue 17, p. 656 –657
- DOI: 10.1049/el:19830446
- Type: Article
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Fine tuning of lasing wavelength was achieved with a butt-jointed built-in DBR laser integrated with an additional tuning waveguide. The plasma effect of the injected carrier was utilised. The wavelength shift of 4.0 Å was demonstrated by an injected tuning current of 4.1 mA.
Solid-state devices in H-guide, groove guide and fence guide
- Author(s): F.A. Benson ; P.A. Cudd ; F.J. Tischer
- Source: Electronics Letters, Volume 19, Issue 17, p. 657 –658
- DOI: 10.1049/el:19830447
- Type: Article
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A novel concept of integrating solid-state devices with H-groove and fence guides at millimetre wavelengths is described. Microstrip circuits containing beam-lead diodes are inserted parallel to the sidewalls in the centre of the guides. As an example an integrated detector circuit is shown and results of experiements presented.
New method for equivalent-step-index fibre determination
- Author(s): C. Pask and F. Rühl
- Source: Electronics Letters, Volume 19, Issue 17, p. 658 –659
- DOI: 10.1049/el:19830448
- Type: Article
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We propose a new method for determining equivalent-step index fibres: the far-field intensity halfangle is measured for a range of wavelengths and the data fitted by the step-fibre formula. A simple analytical formula aids the analysis. Proven experimental techniques can be used and no Gaussian or other theoretical approximations are involved.
Optical losses in metal/SiO2-clad Ti:LiNbO3 waveguides
- Author(s): L.L. Buhl
- Source: Electronics Letters, Volume 19, Issue 17, p. 659 –660
- DOI: 10.1049/el:19830449
- Type: Article
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We present measured excess loss resulting from electrode overlays for both TE and TM polarisations as a function of SiO2 buffer layer thickness for Ti:LiNbO3 strip waveguides at λ = 1.32 μm. We find there is negligible excess loss to the TE mode with no buffer layer and that the excess loss to the TM mode can be essentially eliminated with a SiO2 layer only 700 Å thick. A passive polariser with ̃ 1.5 dB fibre-waveguide-fibre insertion loss and > 13 dB extinction ratio is also demonstrated.
Far-field distribution of semiconductor phase-locked arrays with multiple contacts
- Author(s): J. Katz ; E. Kapon ; C. Lindsey ; S. Margalit ; A. Yariv
- Source: Electronics Letters, Volume 19, Issue 17, p. 660 –662
- DOI: 10.1049/el:19830450
- Type: Article
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Experimental results of far-field patterns of semiconductor laser arrays with multiple contacts are reported. It is found that, by tailoring the distribution of the currents through the array elements, narrow single-lobe patterns—which are more useful in most applications—can be obtained from arrays that usually operate in a double-lobe mode. A diffraction-limited 1.8°-wide far-field pattern was obtained from a three-element array.
Incident wavelength dependence of pulse responses in InP/InGaAsP/InGaAs avalanche photodiodes
- Author(s): K. Yasuda ; T. Shirai ; T. Mikawa ; Y. Kishi ; T. Kaneda
- Source: Electronics Letters, Volume 19, Issue 17, p. 662 –663
- DOI: 10.1049/el:19830451
- Type: Article
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Pulse responses of InP/InGaAsP/InGaAs APDs have been studied at 1.3 and 1.55 μm. A faster response rise-up characteristic was observed at 1.55 μm than at 1.3 μm. This result indicates that response speed depends on the hole generating region and hole pile-up at the heterojunction is decreased by introducing a hole-acceleration layer such as InGaAsP.
Emission frequency stability in single-mode-fibre optical feedback controlled semiconductor lasers
- Author(s): F. Favre and D. le Guen
- Source: Electronics Letters, Volume 19, Issue 17, p. 663 –665
- DOI: 10.1049/el:19830452
- Type: Article
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A newly designed semiconductor laser emitter with adjustable linewidth by controlling the coupling to a single-mode fibre is described with emphasis on thermal requirements to obtain a high-frequency stability. A stable operation has been achieved during more than 1 h using an AlGaAs laser diode with optical feedback from a 50 cm-long single-mode fibre resulting in a 50-fold reduction of the spectral linewidth.
Ka-band Y-circulators in integrated waveguide technology
- Author(s): C. Schieblich and J.H. Hinken
- Source: Electronics Letters, Volume 19, Issue 17, p. 665 –666
- DOI: 10.1049/el:19830453
- Type: Article
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A simple Ka-band Y-circulator is presented, fabricated according to integrated waveguide technology (INWATE). The performance is as follows: 20 dB isolation bandwidth of 20%, and return loss and insertion loss about 20 dB and 0.5 dB, respectively. This type of circulator seems to be well suited to form part of future INWATE circuits.
Electroplated Au-GaAs1−xPx and Au-Ga1−xAlxAs Schottky barriers
- Author(s): M. López-Coronado ; M. Aguilar ; M.T. Martínez ; E. Calleja ; E. Muñoz
- Source: Electronics Letters, Volume 19, Issue 17, p. 666 –668
- DOI: 10.1049/el:19830454
- Type: Article
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A novel technique based on pulse electroplating and surface treatment with very slow etching rate solutions has been applied to fabricate Au Schottky barriers on GaAs1−xPx and Ga1−xAlxAs. Device characteristics are compared to the behaviour of vacuum-deposited barriers. The present technique allows a simple and fast procedure to obtain Schottky barriers for material evaluation and device applications.
Generation of single-longitudinal-mode gigabit-rate optical pulses from semiconductor lasers through harmonic-frequency sinusoidal modulation
- Author(s): H. Kawaguchi and K. Otsuka
- Source: Electronics Letters, Volume 19, Issue 17, p. 668 –669
- DOI: 10.1049/el:19830455
- Type: Article
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Generation of optical pulses at gigabit rates from semiconductor lasers by means of harmonic-frequency sinusoidal injection current modulation has been demonstrated for the first time. It was confirmed that these optical pulses consisted of one longitudinal oscillating mode because of the presence of a ‘self-optical injection-locking effect’.
Low-temperature expitaxial growth of (100) silicon
- Author(s): M. Milosavljević ; C. Jeyens ; I.H. Wilson
- Source: Electronics Letters, Volume 19, Issue 17, p. 669 –671
- DOI: 10.1049/el:19830456
- Type: Article
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Epitaxial silicon films have been grown onto as-received and implanted (100) silicon wafers by electron-beam evaporation. A high-temperature treatment to remove native oxide was not employed. Optimum temperatures for epitaxial growth were between 600°C and 700°C. Deposition rates were from 30 to 80 nm/min and the operating pressure was < 5 × 10 − 7 mbar. The Rutherford backscattering spectra of the optimum films have values of χmin indistinguishable from that of a bulk wafer (3.9%).
Fibre-optic digital transmission experiment with heterodyne detection
- Author(s): E.-J. Bachus ; F. Böhnke ; W. Eutin ; B. Strebel
- Source: Electronics Letters, Volume 19, Issue 17, p. 671 –672
- DOI: 10.1049/el:19830457
- Type: Article
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A single-channel single-polarisation all-fibre-optic transmission system at 830 nm wavelength with transmitter laser and a heterodyne receiver with local laser, monomode fibre coupler and APD mixer has been set up. The intermediate frequency was 1.5 GHz. 8.4 Mbit/s digital signals were transmitted over 280 m of single-polarisation fibre by a subcarrier modulated baseband method.
Wavelength-discriminating photodetector for lightwave systems
- Author(s): J.C. Campbell ; C.A. Burrus ; J.A. Copeland ; A.G. Dentai
- Source: Electronics Letters, Volume 19, Issue 17, p. 672 –674
- DOI: 10.1049/el:19830458
- Type: Article
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We demonstrate that a dual-wavelength photodetector can be used to determine simultaneously the wavelength and the power level of a lightwave signal. The signal wavelength is determined by monitoring the ratio of the two outputs from this photodetector at the crossover of its responsivity curves; the signal level is determined from the sum of the two outputs. Possible applications for this type of photodetector include mode-control of single-frequency injection lasers, direct demodulation for lightwave systems utilising frequency-shift-keyed transmission, wavelength-division multiplexing and optical logic.
Optical fibre jacketed with high-modulus low-linear-expansion-coefficient polymer
- Author(s): F. Yamamoto ; K. Nakagawa ; Y. Shuto ; S. Yamakawa
- Source: Electronics Letters, Volume 19, Issue 17, p. 674 –675
- DOI: 10.1049/el:19830459
- Type: Article
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A high Young's modulus, low-linear-expansion-coefficient-polymer loose-jacket optical fibre has been developed using orientated polyoxymethylene (POM), which exhibits Young's moduli 20 to 40 GPa and linear expansion coefficients ≤ 10−6°C−1. The highly orientated POM loose-jacket fibre has no microbending losses in a temperature range −60 to 80°C.
Double-square frequency-selective surfaces and their equivalent circuit
- Author(s): R.J. Langley and E.A. Parker
- Source: Electronics Letters, Volume 19, Issue 17, p. 675 –677
- DOI: 10.1049/el:19830460
- Type: Article
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The general form of the plane-wave transmission/frequency curves for frequency-selective surfaces consisting of arrays of double squares has been deduced from the performance of 13 different arrays. Band spacing ratios between 1.5 and about 2.2 are available. An equivalent circuit is presented for design work.
Easily trimmed third-order RC-active-filter section with finite transmission zeros
- Author(s): J.M. Rollett
- Source: Electronics Letters, Volume 19, Issue 17, p. 677 –678
- DOI: 10.1049/el:19830461
- Type: Article
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A third-order single-amplifier RC-active-filter section with finite transmission zeros is described. The poles and zeros of the network can be adjusted with little interaction by varying resistances in a suitable sequence, so that the section can be economically constructed with wide tolerance capacitors and trimmed to specification. A design for a ninth-order audio bandpass filter is included as an example.
Bend behaviour of polarising optical fibres
- Author(s): M.P. Varnham ; D.N. Payne ; R.D. Birch ; E.J. Tarbox
- Source: Electronics Letters, Volume 19, Issue 17, p. 679 –680
- DOI: 10.1049/el:19830462
- Type: Article
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Experimental results are presented which show how both bend radius and the orientation of the fibre in the bend considerably affect the single-polarisation operation of bow-tie fibres.
Improved feed network for group-type unidirectional transducers
- Author(s): G. Macchiarella and G. Viola
- Source: Electronics Letters, Volume 19, Issue 17, p. 680 –681
- DOI: 10.1049/el:19830463
- Type: Article
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In the letter we propose a phasing and matching network for group-type unidirectional transducers (GT-UDTs) which takes into account the electroacoustic interactions between the two phases of the GT-UDT. In comparison with analogous feed circuits from the literature, this network represents an improvement as far as the reduction of the residual fluctuations in the passband frequency response of a GT-UDT device is concerned.
Modification of phase-locked-loop performance using a sample-and-hold circuit
- Author(s): D.V. Thiel and Xiao Wu Wu
- Source: Electronics Letters, Volume 19, Issue 17, p. 681 –682
- DOI: 10.1049/el:19830464
- Type: Article
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The inclusion of a sample-and-hold circuit between the lowpass filter and the VCO of a phase-locked loop allows control over the time period when the loop is locked to the input voltage. This technique has potential in phase measurements, demodulation techniques, phase radar and spread-spectrum communications.
Universal multiple-output second-order digital filter
- Author(s): C. Eswaran and A. Antoniou
- Source: Electronics Letters, Volume 19, Issue 17, p. 683 –684
- DOI: 10.1049/el:19830465
- Type: Article
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A universal, second-order, digital-filter structure is proposed, which realises simultaneously a lowpass, a highpass, a bandpass, a notch and allpass transfer function. The structure uses two unit-delays and four multipliers, and is quite attractive for VLSI implementation since a versatile universal chip can be fabricated, which can be used for the implementation of Butterworth, Cheby̅shev and elliptic digital filters as well as digital equalisers.
Subthreshold currents in CMOS transistors made on oxygen-implanted silicon
- Author(s): D.J. Foster
- Source: Electronics Letters, Volume 19, Issue 17, p. 684 –685
- DOI: 10.1049/el:19830466
- Type: Article
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Kinks have been observed in subthreshold current plots of mesa-shaped n-channel transistors made on oxygen implanted silicon substrates. The kinks represent additional current flow and are due to overlapping fields from the gate electrode causing early corner inversion and to a Qss side-wall effect. Subthreshold currents in n-channel transistors are dominated by the two effects which, as a consequence, reduce threshold voltages especially in narrow n-channel transistors. The subthreshold characteristics of p-channel transistors were not affected in the same way.
Totally self-checking checker for 3N arithmetic codes
- Author(s): N. Gaitanis
- Source: Electronics Letters, Volume 19, Issue 17, p. 685 –686
- DOI: 10.1049/el:19830467
- Type: Article
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In the letter we present a totally self-checking checker for 3N arithmetic codes for every code length n. This checker is composed of two different parts. The first part of the checker is a modulo 15 residue generator and the second part is a simple totally self-checking checker for 3N arithmetic code with code length 4.
Practical single-polarisation anisotropic fibres
- Author(s): A.W. Snyder and F. Rühl
- Source: Electronics Letters, Volume 19, Issue 17, p. 687 –688
- DOI: 10.1049/el:19830468
- Type: Article
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We explain why single-mode single-polarisation operation is possible in practical fibres using less stress-induced birefringence than predicted for ideal anisotropic fibres. Furthermore, our ‘leaky-mode’ design is shown to be superior to more conventional strategies for single-polarisation operation.
Comment: Quantum mechanical explanation of spontaneous emission K-factor
- Author(s): J. Arnaud
- Source: Electronics Letters, Volume 19, Issue 17, p. 688 –689
- DOI: 10.1049/el:19830469
- Type: Article
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Polarisation-mode dispersion as bandwidth-limiting factor in a long-haul single-mode optical-transmission system
- Author(s): K. Suzuki ; N. Shibata ; Y. Ishida
- Source: Electronics Letters, Volume 19, Issue 17, p. 689 –691
- DOI: 10.1049/el:19830470
- Type: Article
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Polarisation-mode dispersion and fibre length dependence of extinction ratio between two orthogonally polarised HE11 modes are measured for predicting bandwidth limitation in high-capacity transmission systems. For a single-mode fibre with 10% core ellipticity and 0.5% refractive-index difference, 3 dB bandwidth and available bit rate after 50 km transmission are evaluated to be 4.8 GHz and 8.8 Gbit/s at v = 2.2, respectively.
Frequency-selective combline directional couplers designed as novel filters and multiplexers
- Author(s): B.A. Herscher and J.E. Carroll
- Source: Electronics Letters, Volume 19, Issue 17, p. 691 –692
- DOI: 10.1049/el:19830471
- Type: Article
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Combline directional couplers may be designed to have useful frequency-dependent transfer characteristics. The normal modes are optimised by a numerical technique to show that novel nonreflective filters and band-branching multiplexers may be achieved without the use of nonreciprocal components such as isolators and circulators.
Comparing the chromatic dispersions of two single-mode silica fibres with pure F and pure GeO2 doping, respectively
- Author(s): T. Müller and W.E. Heinlein
- Source: Electronics Letters, Volume 19, Issue 17, p. 692 –694
- DOI: 10.1049/el:19830472
- Type: Article
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The refractive-index profile and the group-delay spectrum of a purely F-doped silica fibre were measured. This fibre's chromatic dispersion behaves considerably differently from that of a purely GeO2-doped fibre having the same profile function and V-parameter at λ = 0.633 μm.
New and simple method for selective mode group excitation in graded-index optical fibres
- Author(s): A.K. Agarwal ; G. Evers ; U. Unrau
- Source: Electronics Letters, Volume 19, Issue 17, p. 694 –695
- DOI: 10.1049/el:19830473
- Type: Article
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A modified monomode-fibre offset technique as well as a new and very simple method for selective mode excitation in multimode graded-index fibres is presented. It is shown that an inclined plane wave launch followed by a mandrel-wrap mode filter is a powerful way to excite a definite number of mode groups in graded-index fibres. Besides its extreme simplicity this method yields improved selectivity. Experimental results are presented.
CMOS current comparator circuit
- Author(s): D.A. Freitas and K.W. Current
- Source: Electronics Letters, Volume 19, Issue 17, p. 695 –697
- DOI: 10.1049/el:19830474
- Type: Article
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A CMOS current comparator circuit design is presented and its simulated performance described. A comparator circuit designed to detect the presence of, for example, 5 μA realised in a standard polysilicon-gate CMOS process technology exhibits a simulated propagation delay of about 10 ns.
Simulation of GaAs submicron FET with hot-electron injection structure
- Author(s): K. Tomizawa ; Y. Awano ; N. Hashizume ; M. Kawashima
- Source: Electronics Letters, Volume 19, Issue 17, p. 697 –698
- DOI: 10.1049/el:19830475
- Type: Article
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Two-dimensional Monte Carlo simulation of a 0.25 μm-long GaAs FET with an (Al, Ga)As/GaAs heterojunction source is reported for the first time. The mean electron velocity reaches above 7 × 107 (cm/s) in the channel, and extremely high values of Id = 11 (mA/20 μm) and gm = 1250 (mS/mm) are obtained. The unity-current-gain frequency fr is found to reach about 250 GHz.
Polarimetric strain gauges using high birefringence fibre
- Author(s): M.P. Varnham ; A.J. Barlow ; D.N. Payne ; K. Okamoto
- Source: Electronics Letters, Volume 19, Issue 17, p. 699 –700
- DOI: 10.1049/el:19830476
- Type: Article
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When a highly-birefringent fibre is stretched, the birefringence changes. The phenomenon is shown to result from a difference in Poisson's ratio of the two glasses from which the fibre is constructed. Experimental verification is given and a simple polarimetric strain gauge made from bow-tie fibre is demonstrated.
1.3 μm InGaAsP/InP multiquantum-well lasers grown by vapour-phase epitaxy
- Author(s): T. Yanase ; Y. Kato ; I. Mito ; M. Yamaguchi ; K. Nishi ; K. Kobayashi ; R. Lang
- Source: Electronics Letters, Volume 19, Issue 17, p. 700 –701
- DOI: 10.1049/el:19830477
- Type: Article
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Low-threshold InGaAsP/InP multiquantum-well lasers emitting at 1.3 μm have been successfully fabricated. The multilayer structure has been grown by hydride transport vapour-phase epitaxy with a double-growth chamber reactor. Broad-area structure threshold current density as low as 1.2 kA/cm2 has been obtained.
New method for determining the series resistances in a MESFET or TEGFET
- Author(s): P. Urien and D. Delagebeaudeuf
- Source: Electronics Letters, Volume 19, Issue 17, p. 702 –703
- DOI: 10.1049/el:19830478
- Type: Article
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The forward characteristic of the Schottky gate is generally used in a MESFET (or TEGFET) to measure the source or gate series resistances. An original model describing the FET behaviour when a high current flows through the gate is presented. From this model we deduce simple methods for determination of parasitic resistances.
Simple coding scheme for modular arithmetic
- Author(s): B.S. Adiga and P. Shankar
- Source: Electronics Letters, Volume 19, Issue 17, p. 703 –705
- DOI: 10.1049/el:19830479
- Type: Article
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A dual representation scheme for performing arithmetic modulo an arbitrary integer M is presented. The coding scheme maps each integer N in the range 0 ≤ N < M into one of two representations, each being identified by its most significant bit. The encoding of numbers is straightforward and the problem of checking for unused combinations is eliminated.
Equivalent-circuit consideration of dual-gate MESFETs at high frequency
- Author(s): B. Kim
- Source: Electronics Letters, Volume 19, Issue 17, p. 705 –706
- DOI: 10.1049/el:19830480
- Type: Article
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The simplified high-frequency equivalent circuit of a dual-gate FET is described. It is shown that the input impedance is similar to that of a single-gate FET but the output resistance and capacitance (parallel equivalent circuit) are higher. The output resistance and the transconductance decrease as frequency increases. The unilateral gain of a dual-gate FET rolls off 12 dB/octave.
Erratum: Relevance of complex normalisation in precision reflectometry
- Author(s): D. Woods
- Source: Electronics Letters, Volume 19, Issue 17, page: 706 –706
- DOI: 10.1049/el:19830481
- Type: Article
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- Type: Article
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Experimental verification of on-chip CMOS fractional-order capacitor emulators
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54 Gbit/s OOK transmission using single-mode VCSEL up to 2.2 km MMF
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