Online ISSN
1350-911X
Print ISSN
0013-5194
Electronics Letters
Volume 24, Issue 17, 18 August 1988
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Volume 24, Issue 17
18 August 1988
20 GHz bandwidth low-noise HEMT preamplifier for optical receivers
- Author(s): N. Ohkawa
- Source: Electronics Letters, Volume 24, Issue 17, p. 1061 –1062
- DOI: 10.1049/el:19880719
- Type: Article
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A broadband, low-noise HEMT preamplifier is designed for very high-speed fibre-optic transmission systems. A 20 GHz 3dB down bandwidth and 7.6pA/√(Hz) averaged input equivalent noise current density from 100 MHz to 18 GHz are achieved using inductor peaking techniques and low stray capacitance chip resistors.
Non-bulk Si-O bonding at the Si-SiO2 interface
- Author(s): I.W. Boyd
- Source: Electronics Letters, Volume 24, Issue 17, p. 1062 –1063
- DOI: 10.1049/el:19880720
- Type: Article
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A simple silicon dioxide bonding model is applied to a variety of films and shown to be applicable only for grown layers thicker than about 400 Å, indicating that ‘non-bulk’ bonding is present near to the silicon interface.
High-speed digital-to-analogue convertor using passive switched-capacitor algorithmic conversion
- Author(s): V.F. Dias ; J.E. Franca ; J.C. Vital
- Source: Electronics Letters, Volume 24, Issue 17, p. 1063 –1065
- DOI: 10.1049/el:19880721
- Type: Article
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A purely passive parasitic-compensated switched-capacitor circuit is shown to implement a simple signal conversion algorithm consisting of a mere charge division between equal valued capacitors. Such a circuit is the core of the new digital-to-analogue convertor described in this letter, and which is particularly suitable for high-frequency applications. Appropriate design conditions are established to render the overall circuit insensitive to the offset voltage and finite DC gain errors of the amplifier.
Limits of stable operation of AR-coated semiconductor lasers with strong optical feedback
- Author(s): J. Mørk ; P.L. Christiansen ; B. Tromborg
- Source: Electronics Letters, Volume 24, Issue 17, p. 1065 –1066
- DOI: 10.1049/el:19880722
- Type: Article
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The experimentally observed instability of AR-coated lasers in external cavity operation is explained by a simple theory, which yields critical values for the bias current and the reflectivities of the coated laser facet and the external mirror.
High-speed Gao.47In0.53As/InP infra-red Schottky-barrier photodiodes
- Author(s): L. Figueroa ; J.-H. Kim ; S.S. Li ; T.F. Carruthers ; R.S. Wagner
- Source: Electronics Letters, Volume 24, Issue 17, p. 1067 –1068
- DOI: 10.1049/el:19880723
- Type: Article
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We report a new high-speed InP-based Ga1−xInxAs infra-red Schottky-barrier photodiode. The photodiodes were fabricated on both p- and n-GaInAs epilayers using Schottky barrier height enhancement technology. The response speed was measured by the impulse response and autocorrelation method; the risetimes of 85ps for p-GaInAs and 180ps for n-GaInAs photodiodes were obtained, which correspond to the 3dB cutoff frequency of 2–4 GHz. The intrinsic response speed was 12GHz for n-GaInAs and 18GHz for p-GaInAs photodiodes based on SPICE simulation with measured device parameters. The photodiodes had the responsivity as high as 0.55 A/W and the quantum efficiency of up to 45% at 1.3–1.6μm without antireflection coating.
Efficient operation of an Yb-sensitised Er fibre laser pumped in 0.8 μm region
- Author(s): D.C. Hanna ; R.M. Percival ; I.R. Perry ; R.G. Smart ; A.C. Tropper
- Source: Electronics Letters, Volume 24, Issue 17, p. 1068 –1069
- DOI: 10.1049/el:19880724
- Type: Article
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The dependence of threshold and slope efficiency on pump wavelength around 0.8 μm has been investigated for an Yb-sensitised fibre laser. Results confirm a wider choice of pump wavelength compared with unsensitised Er fibre. A 5 mW threshold and slope efficiency of 8.5% were observed for 820–830 nm pumping.
InAsPSb/InAs diode laser emitting in the 2.5μm range
- Author(s): S. Akiba ; Y. Matsushima ; T. Iketani ; M. Usami
- Source: Electronics Letters, Volume 24, Issue 17, p. 1069 –1071
- DOI: 10.1049/el:19880725
- Type: Article
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A double heterostructure consisting of InAsPSb alloys was made by LPE-growth on InAs substrates. Lasing action was confirmed at 15–55K, where the emission wavelength was 2.5–2.7μm.
Network experiment using an 8000 GHz tuning-range optical filter
- Author(s): A.R. Chraplyvy ; R.W. Tkach ; R.M. Derosier
- Source: Electronics Letters, Volume 24, Issue 17, p. 1071 –1072
- DOI: 10.1049/el:19880726
- Type: Article
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A tunable optical filter with 180 MHz resolution and continuous tuning range of 8000 GHz was used in a lightwave network experiment. Three 50Mbit/s channels with minimum channel spacing of 1.6 GHz and maximum channel pacing of 4000 GHz were individually received error-free in the presence of interfering optical power corresponding to 6000 channels.
Fabrication of wavelength-flattened tapered couplers using polishing for cladding removal
- Author(s): C.D. Hussey and T.A. Birks
- Source: Electronics Letters, Volume 24, Issue 17, p. 1072 –1073
- DOI: 10.1049/el:19880727
- Type: Article
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Wavelength-flattened fused tapered couplers have been fabricated with low loss using a new technique. The asymmetry between the constituent fibres is induced by the rapid removal of a small amount of the cladding of one of the fibres with a polishing wheel.
Outage probability calculations for mobile radio systems with multiple interferers
- Author(s): K.W. Sowerby and A.G. Williamson
- Source: Electronics Letters, Volume 24, Issue 17, p. 1073 –1075
- DOI: 10.1049/el:19880728
- Type: Article
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Outage probability calculations are presented for the case when the transmission from a wanted base station is received by a mobile in the presence of multiple cochannel interfering signals for the case where the transmissions suffer both lognormal shadowing and Rayleigh fading. The calculations consider the need to achieve simultaneously both a sufficient SNR and SIR to obtain satisfactory radio reception.
Polarisation-independent configuration optical amplifier
- Author(s): N.A. Olsson
- Source: Electronics Letters, Volume 24, Issue 17, p. 1075 –1076
- DOI: 10.1049/el:19880729
- Type: Article
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A new polarisation independent semiconductor laser amplifier is presented. By using a regular semiconductor amplifier in a double pass configuration, polarisation independent gain is achieved. Experiments demonstrate a reduction in the gain difference between TE and TM waves from 4dB to 0.2 dB.
Characteristic temperature Toof Ga0.83In0.17As0.15Sb0.85/AI0.27Ga0.73As0.02Sb0.98 injection lasers
- Author(s): A. Joullie ; C. Alibert ; H. Mani ; F. Pitard ; E. Tournie ; G. Boissier
- Source: Electronics Letters, Volume 24, Issue 17, p. 1076 –1078
- DOI: 10.1049/el:19880730
- Type: Article
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Stripe injection lasers emitting at 2.18μm at room temperature with a threshold current density Jth = 7−9kA/cm2 have been prepared from Ga0.83In0.17As0.15Sb0.85/Al0.27Ga0.73As0.02Sb0.98 double heterojunctions. The characteristic temperature To of such devices measured between 80 K and 296 K was found to be To = 90 K, essentially controlled by the Auger effect at high temperature.
Observation of mobility enhancement in ultrathin SOI MOSFETs
- Author(s): M. Yoshimi ; H. Hazama ; M. Takahashi ; S. Kambayashi ; H. Tango
- Source: Electronics Letters, Volume 24, Issue 17, p. 1078 –1079
- DOI: 10.1049/el:19880731
- Type: Article
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The mobility in n-channel SOI MOSFETs exhibits a significant increase as the SOI film becomes thinner than 1000 Å. At a 500 Å SOI thickness, the mobility values are distributed in the 700–1100 cm2/Vs range, which are obviously higher than the value in a bulk MOSFET having an identical doping concentration. The observed mobility enhancement has been explained by a decrease in the vertical electric field, associated with the complete depletion of the SOI film.
Digital fast acquisition method for phase-lock loops
- Author(s): R.C.Den Dulk
- Source: Electronics Letters, Volume 24, Issue 17, p. 1079 –1080
- DOI: 10.1049/el:19880732
- Type: Article
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A method for enhancing the frequency-acquisition performance of phase-lock loops (PLLs) is presented, which can be used in all PLLs that employ sequential phase detectors. The proposed method always forces the PLL into the phase-acquisition ode by realising a phase detector transfer characteristic with a pseudolinear infinite phase range. Especially in the case of charge-pump PLLs the proposed method is very useful. Practical results show that the acquisition performance can increase by nearly two orders of magnitude.
Equivalence of optimal slope-sum product discrete and continuous linear electromagnetic radiators
- Author(s): D.A. McNamara and J.P. Jacobs
- Source: Electronics Letters, Volume 24, Issue 17, p. 1081 –1082
- DOI: 10.1049/el:19880733
- Type: Article
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The discrete distributions which provide maximum slope-sum product, analogous to that derived earlier for continuous line sources, are considered and some comparisons made.
Fast sliding search algorithm for vector quantisation in image coding
- Author(s): J.-S. Koh and J.-K. Kim
- Source: Electronics Letters, Volume 24, Issue 17, p. 1082 –1083
- DOI: 10.1049/el:19880734
- Type: Article
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The letter describes a simple algorithm for reducing the coding complexity of vector quantisation (VQ), exploiting the feature of a vector currently being coded. A proposed VQ of vector dimension 16 can reduce the complexity from 256 codeword searches to 16–32 with a slight performance degradation of about 0.1–0.9dB.
Performance improvement in decision feedback equalisers by using ‘soft decision’
- Author(s): E. Dahlman and B. Gudmundson
- Source: Electronics Letters, Volume 24, Issue 17, p. 1084 –1085
- DOI: 10.1049/el:19880735
- Type: Article
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A method to introduce ‘soft decisions’ in a decision feedback equaliser is presented. The method gives a performance improvement in SNR of about 1.5 dB with almost no increase in complexity compared to an ordindary DFE.
Microwave cavity made from high temperature superconductor
- Author(s): W.J. Radcliffe ; J.C. Gallop ; C.D. Langham ; M. Gee ; M. Stewart
- Source: Electronics Letters, Volume 24, Issue 17, p. 1085 –1086
- DOI: 10.1049/el:19880736
- Type: Article
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We report surface impedance measurements made on a cylindrical cavity resonator constructed entirely from the sintered high temperature superconductor YBa2Cu3O7, and have measured the temperature dependence of the surface impedance for five different modes in the frequency range 10–18GHz, in the temperature range from 4–300K.
High power, CW single-frequency, TEMoo, diode-laser-pumped Nd:YAG laser
- Author(s): K. Wallmeroth and P. Peuser
- Source: Electronics Letters, Volume 24, Issue 17, p. 1086 –1088
- DOI: 10.1049/el:19880737
- Type: Article
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255 mW of 1.06μm, CW, single-longitudinal-mode, TEMoo output has been obtained by end-pumping a twisted-mode cavity Nd:YAG laser with a 1 W diode laser.
Three-step heuristic algorithm for optimal PLA column folding
- Author(s): Y.-Y. Yang and C.M. Kyung
- Source: Electronics Letters, Volume 24, Issue 17, p. 1088 –1090
- DOI: 10.1049/el:19880738
- Type: Article
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A three-step heuristic algorithm for PLA column folding is presented, which is significantly faster than the earlier works and provides nearly optimal results. The three steps are (i) Min-Cut partition of vertices in the column intersection graph, (ii) determination of product order using Fiduccia's Min-Net Cut algorithm, and (iii) head-tail pairing for deciding column folding pairs.
Lorentzian force type fibre-optic AC magnetic sensor realising frequency-independent sensitivity
- Author(s): H. Okamura and Y. Fujii
- Source: Electronics Letters, Volume 24, Issue 17, p. 1090 –1091
- DOI: 10.1049/el:19880739
- Type: Article
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A Lorentzian force type fibre-optic magnetic sensor is reported attaining frequency-independent sensitivity in the range 1 Hz to 10 kHz with minimum detectable field down to 50 nT. It is also shown that this technique can introduce frequency superimposition, which enables measurement of AC magnetic fields at different points simultaneously with one interferometer.
New multigate pulsed Doppler system using second-order sampling
- Author(s): Y.B. Ahn ; Y.G. Kim ; S.B. Park
- Source: Electronics Letters, Volume 24, Issue 17, p. 1091 –1093
- DOI: 10.1049/el:19880740
- Type: Article
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A new multigate Doppler system using second-order sampling is proposed. To reduce the hardware complexity and to eliminate the balancing problem between in-phase and quadrature signal channels in conventional systems, the proposed system uses a single signal processing channel. This system can be used in a multigate Doppler system and implemented in a full digital fashion.
Generalised impedance boundary conditions for EM scattering problems
- Author(s): R.G. Rojas
- Source: Electronics Letters, Volume 24, Issue 17, p. 1093 –1094
- DOI: 10.1049/el:19880741
- Type: Article
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Generalised impedance boundary conditions (GIBC) are derived for a planar, homogeneous, magnetic dielectric slab grounded by a perfect electric conducting plane. These boundary conditions, which are expressed in terms of linear differential operators of infinite order, reduce to the Weinstein boundary conditions in the limiting case of small thickness of the dielectric slab.
GaInP/AlGaInP double-heterostructure laser grown on a (111)B-oriented GaAs substrate by metalorganic chemical vapour deposition
- Author(s): M. Ikeda ; E. Morita ; A. Toda ; T. Yamamoto ; K. Kaneko
- Source: Electronics Letters, Volume 24, Issue 17, p. 1094 –1095
- DOI: 10.1049/el:19880742
- Type: Article
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Room temperature continuous-wave operation of a Ga0.5In0.5P/(Al0.5Ga0.5)0.5In0.5P double-heterostructure laser grown on a (111)B-oriented GaAs substrate by metalorganic chemical vapour deposition was obtained for the first time. The threshold current was 99 mA. The emission wavelength was around 650 nm, which was about 30 nm shorter than that of a similar laser grown on a (100)-oriented GaAs substrate.
One-step completely orthogonalisable UEP codes and their soft decision decoding
- Author(s): Fan Pingzhi ; Chen Zhi ; Jin Fan
- Source: Electronics Letters, Volume 24, Issue 17, p. 1095 –1097
- DOI: 10.1049/el:19880743
- Type: Article
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The concept of one-step complete orthogonality is extended to linear UEP codes and then, two soft-decision decoding algorithms for the one-step completely orthogonalisable UEP codes are presented.
Assessment of moisture content of fibres and fabrics by measurement of extinction cross-section in an open resonator
- Author(s): A.L. Hume and L.J. Auchterlonie
- Source: Electronics Letters, Volume 24, Issue 17, p. 1097 –1098
- DOI: 10.1049/el:19880744
- Type: Article
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A new application of a large, computer-controlled open resonator is described. Measurement of the extinction crosssections of samples of wet materials are recorded very quickly and continuously throughout the drying period. The measurements may be taken throughout the interval 8–12 GHz and provide a complete record of the drying process.
Parallel processing for Viterbi algorithm
- Author(s): Kuei Ann Wen and Jau Yien Lee
- Source: Electronics Letters, Volume 24, Issue 17, p. 1098 –1099
- DOI: 10.1049/el:19880745
- Type: Article
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Dual-dimensional parallelisation for the Viterbi algorithm is exploited. That is, parallelisation of the decoding procedures within each stage of the trellis and parallelisation of the decoding procedures are expanded to consecutive stages without excessive path memories. Since an arbitrary number of stages can be parallelised, the trade-off between computation speed and degree of integration can be adjusted as required.
Back side reflection influence on quantum efficiency of photovoltaic devices
- Author(s): Z. Djuric and Z. Jaksic
- Source: Electronics Letters, Volume 24, Issue 17, p. 1100 –1101
- DOI: 10.1049/el:19880746
- Type: Article
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A method is proposed for calculation of the quantum efficiency of photovoltaic devices, which takes into account the back side reflection and corresponding surface recombination rates. The applied technique enables simple theoretical prediction of basic photovoltaic device parameters.
Improved self-boot-strapped gain enhancement technique for GaAs amplifiers
- Author(s): H.C. Yang and D.J. Allstot
- Source: Electronics Letters, Volume 24, Issue 17, p. 1101 –1102
- DOI: 10.1049/el:19880747
- Type: Article
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In this letter, we report an improved self-boot-strapped gain enhancement circuit structure for GaAs MESFET amplifiers. Unlike previously reported work, this circuit operates based on first-order characteristics of GaAs MESFETs and requires no extra processing steps. Analysis shows that the new circuit also provides a higher output resistance.
Subpicosecond spectral gain dynamics in AlGaAs laser diodes
- Author(s): M.P. Kesler and E.P. Ippen
- Source: Electronics Letters, Volume 24, Issue 17, p. 1102 –1104
- DOI: 10.1049/el:19880748
- Type: Article
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We present results of tunable probe measurements of ultrafast dynamics in AIGaAs diode laser amplifiers. The use of gated upconversion has allowed the observation of subpicosecond gain depletion and recovery with pump-probe separations of up to 30 nm. The data show no sign of spectral hole burning and are consistent with the mechanism of dynamic carrier heating.
Pulsed laser emission at 2.3μm in a thulium-doped fluorozirconate fibre
- Author(s): L. Esterowitz ; R. Allen ; I. Aggarwal
- Source: Electronics Letters, Volume 24, Issue 17, page: 1104 –1104
- DOI: 10.1049/el:19880749
- Type: Article
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We report for the first time laser emission at 2.3μ from a thulium-doped fluorozirconate fibre pumped by a pulsed alexandrite laser at 0.786μm. Threshold occurs at 25μd incidenton the focusing lens. This wavelength is in the 2–3 n ultra-low loss region of fluorozirconate fibres. Furtherimprovement is expected to result in CW operation using diode laser pumping.
New determination of resonant frequency of circular disc microstrip antenna: application to thick substrate
- Author(s): F. Abboud ; J.P. Damiano ; A. Papiernik
- Source: Electronics Letters, Volume 24, Issue 17, p. 1104 –1106
- DOI: 10.1049/el:19880750
- Type: Article
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An analytical expression is presented for the resonant frequency of a circular disc microstrip antenna with a thick dielectric substrate. It shows explicitly the dependence of the resonant frequency on the characteristic parameters of a patch antenna. The theoretical results are in good agreement with experimental data.
140 Mbit/s DPSK transmission using an all-optical frequency convertor with a 4000 GHz conversion range
- Author(s): G. Grosskopf ; R. Ludwig ; H.G. Weber
- Source: Electronics Letters, Volume 24, Issue 17, p. 1106 –1107
- DOI: 10.1049/el:19880751
- Type: Article
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A new method of optical frequency conversion is described and demonstrated by a 140 Mbit/s DPSK optical transmission experiment. A modulated optical input signal is converted by 1500 GHz in a modulated optical output signal with a fibre-to-fibre efficiency of −10dB.
Experimental evaluation of trellis decoding performance on linear block codes in digital mobile radio
- Author(s): T. Matsumoto
- Source: Electronics Letters, Volume 24, Issue 17, p. 1107 –1108
- DOI: 10.1049/el:19880752
- Type: Article
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Word error rate (WER) performance with soft decision decoding of linear block codes using a trellis is investigated in a Rayleigh fading channel. The signal envelopes corresponding to each bit in a received block are sampled and used for estimating the reliability of the bit. The WER performance is evaluated via laboratory experiments using Hamming (7, 4) code. A great improvement in WER performance can be achieved over conventionally-used minimum distance decoding.
AlGaAs/GaAs HBT dynamic frequency divider constructed of a single d type flip-flop
- Author(s): Y. Yamauchi ; K. Nagata ; O. Nakajima ; H. Ito ; T. Nittono ; T. Ishibashi
- Source: Electronics Letters, Volume 24, Issue 17, p. 1109 –1110
- DOI: 10.1049/el:19880753
- Type: Article
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A new dynamic frequency divider circuit operated by a single D-type flip-flop was designed and fabricated utilising AlGaAs/GaAs heterojunction bipolar transistors (HBTs). The circuit was constructed as a divide-by-four circuit combined with a static divide-by-two circuit for a second stage. A toggle frequency range from 18 to 26.5 GHz was obtained for a total power dissipation of 315 mW at a power supply voltage of 7 V.
Four new runlength constrained recording codes
- Author(s): G. van Rensburg and H.C. Ferreira
- Source: Electronics Letters, Volume 24, Issue 17, p. 1110 –1111
- DOI: 10.1049/el:19880754
- Type: Article
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Four simple runlength constrained codes for digital optical or magnetic recording are presented. Parameters are R = 1/3, (d, k) = (1, 2), R =1/4, (d, k) = (4, 8), R = 1/4, (d, k) = (4, 7) and R = 1/4, (d, k) = (5, 9). Both the finite-state transition diagrams for the encoders and sliding-block decoders are presented.
Continuous-wave oscillation of a monomode ytterbium-doped fibre laser
- Author(s): D.C. Hanna ; R.M. Percival ; I.R. Perry ; R.G. Smart ; P.J. Suni ; J.E. Townsend ; A.C. Tropper
- Source: Electronics Letters, Volume 24, Issue 17, p. 1111 –1113
- DOI: 10.1049/el:19880755
- Type: Article
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Laser emission has been observed in a monomode fibre doped with ytterbium. A wide tuning range has been observed, 1.015μm to 1.140μm, when pumped by a dye laser at 840 nm. Diode pumped operation has also been achieved in a cooled fibre.
Intrinsic limitation of transconductance in extremely short silicon MOS transistors
- Author(s): G. Ghibaudo
- Source: Electronics Letters, Volume 24, Issue 17, p. 1113 –1114
- DOI: 10.1049/el:19880756
- Type: Article
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An analysis of the limitation of transconductance by nonstationary transport in extremely short silicon MOS transistors is presented. It is shown using a dynamic Boltzmann transport approach that the transconductance should saturate when reducing the device length to some fraction of the mean free path. In silicon, this limit is found to range around 0.03 – 0.04μm for devices operating at 77 K.
Observation of high cn2 and turbulent path length on OTS space-Earth link
- Author(s): P. Basili ; P. Ciotti ; G. D'Auria ; P. Ferrazzoli ; D. Solimini
- Source: Electronics Letters, Volume 24, Issue 17, p. 1114 –1116
- DOI: 10.1049/el:19880757
- Type: Article
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Simple models have been used to estimate characteristic height and intensity of tropospheric refractive turbulence from fluctuations of the field amplitude received by two antennas of diverse sizes on the OTS space-Earth path. Data refer to particular events of high scintillation, probably associated with the presence of nonprecipitating clouds, and yield elevated values of cn2.
Analytical model for semiconductor laser amplifiers in coherent optical systems
- Author(s): K. Hinton
- Source: Electronics Letters, Volume 24, Issue 17, p. 1116 –1117
- DOI: 10.1049/el:19880758
- Type: Article
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A model based on a full travelling-wave analysis of a semiconductor laser amplifier is applied to calculate the increase in spectral linewidth of an unmodulated optical carrier passing through the amplifier. This linewidth can then be used in system performance calculations for a coherent optical transmission system employing laser amplifiers along the fibre link.
Erratum: Asymptotic formula for elliptic function modulus
- Author(s): H. Hsu ; S.-S. Bor ; Y. Xu
- Source: Electronics Letters, Volume 24, Issue 17, page: 1117 –1117
- DOI: 10.1049/el:19880759
- Type: Article
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Erratum: Improved figure of merit for noise in avalanche photodiodes
- Author(s): L.D. Westbrook ; M.D.A. MacBean ; P.M. Rodgers
- Source: Electronics Letters, Volume 24, Issue 17, page: 1117 –1117
- DOI: 10.1049/el:19880760
- Type: Article
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Erratum: GaAs/AlGaAs multiple quantum well pin diodes grown by selective area epitaxy
- Author(s): D.A. Roberts ; J.P.R. David ; G. Hill ; P.A. Houston ; M.A. Pate ; J.S. Roberts ; P.N. Robson
- Source: Electronics Letters, Volume 24, Issue 17, page: 1117 –1117
- DOI: 10.1049/el:19880761
- Type: Article
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