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Online ISSN 1350-911X Print ISSN 0013-5194

Electronics Letters

Volume 24, Issue 3, 4 February 1988

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Volume 24, Issue 3

4 February 1988

Generation of self-sustained optical pulses from transients in external cavity semiconductor lasers
Semi-insulating blocked planar BH GaInAsP/InP laser with high power and high modulation bandwidth
Stable optical picosecond pulses from actively mode-locked twin-section diode lasers
Use of GaAs high-gain photoconductors as new detectors in spectroscopic systems
  • Author(s): M. Constant ; L. Boussekey ; D. Decoster ; J.P. Vilcot
  • Source: Electronics Letters, Volume 24, Issue 3, p. 141 –142
  • DOI:  10.1049/el:19880094
  • Type: Article
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  • p. 141 –142 (2)
    The purpose of the letter is to show the capability of GaAs planar photoconductors for use as new detectors in spectro-scopic systems. After a description of the devices, their optical properties are briefly reviewed in terms of external steady-state gain. An example of the application of these devices in a conventional Raman detection system and the performance of the photoconductor array in image detection are given.
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Efficient algorithm for logic design using multiplexers
New class of codes suitable for computer error control
Study of the operation speed of half-micron design rule CMOS ring oscillators
  • Author(s): M. Yoshimi ; K. Tsuchiya ; M. Iwase ; M. Takahashi ; E. Nishimura ; T. Suzuki ; Y. Kato
  • Source: Electronics Letters, Volume 24, Issue 3, p. 146 –147
  • DOI:  10.1049/el:19880097
  • Type: Article
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  • p. 146 –147 (2)
    The operation speed of a 73-stage CMOS ring oscillator with 0.5 μm channel lengths has been investigated. By employing a capacitance-reduced structure, gate delays of 47.4 ps and 49.3 ps with and without substrate bias at room temperature, and of 43.0 ps at 77K, respectively, have been experimentally obtained at a supply voltage of 5 V. From the evaluation of parasitic capacitances, the speed which is achievable by the proper scaling of the device parameters at a half-micron design rule is estimated to be approximately 30 ps.
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Low threshold operation of 1.55 μm GaInAsP/InP DFB-BH LDs entirely grown by MOVPE on InP gratings
  • Author(s): H. Yamada ; T. Sasaki ; S. Takano ; T. Numai ; M. Kitamura ; I. Mito
  • Source: Electronics Letters, Volume 24, Issue 3, p. 147 –149
  • DOI:  10.1049/el:19880098
  • Type: Article
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  • p. 147 –149 (3)
    1.55 μm GaInAsP/InP DFB-BH LDs on corrugated InP substrates were fabricated by only two-stage MOVPE, including burying layer growth. The 9 mA minimum threshold current was achieved with both facets cleaved, which the authors believe is the lowest among MOVPE grown DFB LDs with InP grating. Up to 20mW maximum output power and 0.21 W/A differential quantum efficiency were also attained under single longitudinal mode operation.
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Performance comparison between semicontinuous and discrete hidden Markov models of speech
Narrowband GaInAsP/InP waveguide grating-folded directional coupler multiplexer/demultiplexer
2.4 GHz MESFET sampler
Al0.48In0.52As/Ga0.47In0.53As resonant tunnelling diodes with large current peak/valley ratio
  • Author(s): A.A. Lakhani ; R.C. Potter ; D. Beyea ; H.H. Hier ; E. Hempfling ; L. Aina ; J.M. O'CONNOR
  • Source: Electronics Letters, Volume 24, Issue 3, p. 153 –154
  • DOI:  10.1049/el:19880102
  • Type: Article
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  • p. 153 –154 (2)
    Resonant tunnelling diodes consisting of an MBE-grown AlInAs barrier on each side of a lattice-matched GaInAs well have been fabricated. Current peak/valley ratios up to 7.1 and 39 have been measured at 300 K and 77K, respectively. These represent the largest values reported to date in any double-barrier, single-well device. The enhanced peak/valley ratio has been attributed to thick barriers (72 Å) and wide, undoped GaInAs spacer layers (400 Å).
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Relationship between MDS codes and threshold schemes
Two mask step polysilicon TFT technology for flat panel displays
Intensity noise in ASK coherent lightwave receivers
  • Author(s): A.F. Elrefaie ; D.A. Atlas ; L.G. Kazovsky ; R.E. Wagner
  • Source: Electronics Letters, Volume 24, Issue 3, p. 158 –159
  • DOI:  10.1049/el:19880105
  • Type: Article
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  • p. 158 –159 (2)
    The effect of local oscillator intensity noise on the performance of two and three-branch ASK homodyne receivers and single-branch ASK heterodyne receivers is investigated and an optimum local oscillator power is found. At optimum local oscillator power, both the three-branch and heterodyne receivers are found to have a somewhat better sensitivity than the two-branch receiver. If the local oscillator power is higher than the optimum value, the three-branch receiver is significantly less sensitive to intensity noise than the other two receivers.
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Inline tunable etalon filter for optical channel selection in high density wavelength division multiplexed fibre systems
  • Author(s): A. Frenkel  and  C. Lin
  • Source: Electronics Letters, Volume 24, Issue 3, p. 159 –161
  • DOI:  10.1049/el:19880106
  • Type: Article
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  • p. 159 –161 (3)
    We report an inline angle-tuned Fabry-Perot etalon for optical channel selection in a high-density wavelength division multiplexed (WDM) direct-detection experiment. Feasibility is demonstrated in experiments with two different etalons: one for 5 distributed feedback (DFB) lasers in the 1550 nm region (1527–1559 nm), each spaced by 8 nm, and the other for 12 lasers (1527–1549nm), each spaced by 2 nm.
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Improving discriminability among acoustically similar words by modified distance metric
  • Author(s): H.S. Kim  and  C.K. Un
  • Source: Electronics Letters, Volume 24, Issue 3, p. 161 –163
  • DOI:  10.1049/el:19880107
  • Type: Article
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  • p. 161 –163 (3)
    In a template-matching based speech recognition system, excessive weight given to perceptually unimportant spectral variations is undesirable for discriminating among acoustically similar words. By introducing a simple threshold-type nonlinearity applied to the distance metric, the word recognition performance can be improved for a vocabulary with similar sounding words, without modifying the system structure.
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1 Gbit/s bipolar optical FSK transmission experiment over 121 km of fibre
Detection of airborne compact sources against maritime backgrounds in infra-red scenes
Hard waveguide feeds with circular symmetry for aperture efficiency enhancement
  • Author(s): E. Lier
  • Source: Electronics Letters, Volume 24, Issue 3, p. 166 –167
  • DOI:  10.1049/el:19880110
  • Type: Article
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  • p. 166 –167 (2)
    Hard horns or waveguide feeds with circular symmetry have been studied with respect to gain (aperture efficiency) and crosspolarisation. The corrugated or strip-loaded representations of these feeds give almost identical radiation properties when surface waves are neglected. The contribution from the wall region increases the gain and crosspolar bandwidth of the feed. The gain increases and the crosspolar bandwidth decreases with increasing waveguide diameter and wall permittivity. The hard horns may be useful in cluster feeds and limited scan arrays due to reduced size and weight.
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Noninvasive pulse modulator concept for nonradiative dielectric (NRD) waveguide
Definition of artificially soft and hard surfaces for electromagnetic waves
Picosecond pulse generation in detuned distributed feedback lasers
  • Author(s): T. Sogawa ; Y. Arakawa ; T. Kamiya
  • Source: Electronics Letters, Volume 24, Issue 3, p. 170 –171
  • DOI:  10.1049/el:19880113
  • Type: Article
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  • p. 170 –171 (2)
    The effect of detuning the Bragg wavelength for picosecond pulse generation in GalnAsP distributed feedback (DFB) lasers is investigated using the gain switching method. We have observed that the pulse width is reduced in a detuned DFB laser, in which the differential gain is enhanced through detuning the Bragg wavelength λB, from the gain peak to a shorter wavelength by 100 Å. This result demonstrates the significance of the differential gain for short pulse generation.
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Electrical properties of low-temperature pyrolytic SiO2 on InP
  • Author(s): B.R. Bennett ; J.P. Lorenzo ; K. Vaccaro
  • Source: Electronics Letters, Volume 24, Issue 3, p. 172 –173
  • DOI:  10.1049/el:19880114
  • Type: Article
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  • p. 172 –173 (2)
    The first application of a new technique (SiH4 + O2 at 83–330°C and 2–12 torr) for deposition of SiO2 on InP is reported. SiO2 deposited at 150–330°C has breakdown strength of 8–10MV/cm, resistivity > 1015 Ωcm, and refractive index of 1.45–1.46 comparable to thermal SiO2 grown at 1100°C/V measurements on Al/SiO2/InP MIS structures suggest that very low temperature oxides (90–100°C) have the best interfacial properties.
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Low-cost approach for steerable flat-plate antenna design with application to reception of broadcasting from satellite
  • Author(s): M.C.D. Maddocks
  • Source: Electronics Letters, Volume 24, Issue 3, p. 173 –174
  • DOI:  10.1049/el:19880115
  • Type: Article
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  • p. 173 –174 (2)
    A novel design approach for circularly polarised flat-plate antennas has been developed. The proposed antenna is of multilayer construction, rotatable about its normal axis, and comprises a polarisation convertor, an array of elements and a beamforming network. In one potentially large application, the reception of satellite broadcast signals in the 12GHz band, it can be mounted flat on the most suitable wall of an arbitrarily orientated house and be readily aligned.
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Using Lagrange's interpolation formula to construct Reed-Solomon codes over GF(p)
Three-channel, high-speed transmission over 8 km installed, 1300 nm optimised single-mode fibre using 800 nm CD laser and 1300/1500 nm LED transmitters
  • Author(s): M. Stern ; V. Shah ; W.I. Way ; M.B. Romeiser ; W.C. Young
  • Source: Electronics Letters, Volume 24, Issue 3, p. 176 –177
  • DOI:  10.1049/el:19880117
  • Type: Article
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  • p. 176 –177 (2)
    The feasibility of wavelength division multiplexing 800, 1300 and 1500 nm channels over an 8 km long, installed, 1300nm optimised single-mode fibre loop has been demonstrated. A 780 nm CD-laser and Si-APD receiver were used to transmit data at 150 Mbit/s on one of the channels. A 0.25 metre long, 800 nm optimised SM fibre section was used at the receiver to filter the LP11 mode propagating in 1300 nm optimised SM fibre at 800 nm. The mode filter significantly reduced intermodal distortion, thus allowing high-speed 800 nm transmission over the loop. Edge-emitting, 1300 and 1500 nm LEDs were used to transmit 140 and 90 Mbit/s data, respectively.
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Design of parallel resonant convertor with LCC-type commutation
  • Author(s): I. Batarseh ; R. Liu ; C.Q. Lee
  • Source: Electronics Letters, Volume 24, Issue 3, p. 177 –179
  • DOI:  10.1049/el:19880118
  • Type: Article
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  • p. 177 –179 (3)
    Using a set of characteristic curves derived from the stateplane diagram, a novel approach to the design of the LCCtype capacitive coupled parallel resonant convertor (LCC-type PRQ, operating in the continuous conduction mode, is presented. The steady-state response of the convertor can also be obtained from the characteristic curves, from which the convenor's component stress can be easily assessed.
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Optical mixer-preamplifier for lightwave subcarrier systems
Two-wavelength disordered quantum-well photodetector
  • Author(s): B.C. Johnson ; J.C. Campbell ; R.D. Dupuis ; B. Tell
  • Source: Electronics Letters, Volume 24, Issue 3, p. 181 –182
  • DOI:  10.1049/el:19880120
  • Type: Article
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  • p. 181 –182 (2)
    A GaAs/AlGaAs waveguide photodetector combining disordered and as-grown quantum well photodiodes is described. The disordered section serves both as short wavelength photodiode and as a passive waveguide to transmit longer wavelengths to the as-grown section. Optical absorption and photocurrent spectra demonstrate the absorption edge shift due to disordering and the two wavelength-band selectivity of the device.
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Performance of crossbar interconnection networks in presence of ‘hot spots’
  • Author(s): A. Pombortsis  and  C. Halatsis
  • Source: Electronics Letters, Volume 24, Issue 3, p. 182 –184
  • DOI:  10.1049/el:19880121
  • Type: Article
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  • p. 182 –184 (3)
    In the letter we present an interference analysis of an N × N crossbar for a tightly coupled multiprocessor in the presence of ‘hot spot’ traffic conditions. The analysis shows that this hot spot traffic model includes the uniform traffic model as a special case and that the crossbar network compared to multistage networks is less affected by this nonuniformity of memory reference patterns.
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Implementation of MOSFET-C filters based on active RC prototypes
Performance of continuous phase modulations in presence of cochannel interference
Resonant tunnelling in AlInas/GaInAs double barrier diodes grown by MOCVD
Ultrahigh-voltage double-interdigitated (TIL) gate-assisted turnoff thyristors
Erratum: Antireflection coatings for optical semiconductor amplifiers: justification of a heuristic analysis
Erratum: Generalised alternor

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