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image of Volume 23, Issue 14
Online ISSN 1350-911X Print ISSN 0013-5194

Electronics Letters

Volume 23, Issue 14, 2 July 1987

Volumes & issues:

Volume 23, Issue 14

2 July 1987

Simple block-effect reduction method for image coding with vector quantisation
Novel varactor-tuned millimetre-wave Gunn oscillator
  • Author(s): R.N. Bates  and  S. Feeney
  • Source: Electronics Letters, Volume 23, Issue 14, p. 714 –715
  • DOI:  10.1049/el:19870507
  • Type: Article
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  • p. 714 –715 (2)
    A novel design of varactor-tuned millimetre-wave second-harmonic Gunn oscillator is reported in which a varactor is mounted in a secondary cavity resonant at the fundamental frequency of the Gunn diode. This has the advantage that the varactor does not significantly load the Gunn diode at the output second-harmonic frequency, and enables the oscillator to produce the maximum possible output power from the diode while still offering varactor tuning and high Q.
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Linewidth enhancement for DFB lasers due to longitudinal field dependence in the laser cavity
  • Author(s): J. Wang ; N. Schunk ; K. Petermann
  • Source: Electronics Letters, Volume 23, Issue 14, p. 715 –717
  • DOI:  10.1049/el:19870508
  • Type: Article
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  • p. 715 –717 (3)
    To calculate the linewidth for an index-guided semiconductor laser, one usually neglects a correction factor for the spontaneous emission rate, which is introduced by the longitudinal field distribution within the laser cavity. For FabryPerot lasers with cleaved facets the correction factor is small. However, for DFB lasers this correction factor may become quite significant, yielding a linewidth enhancement for DFB laser diodes.
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Perturbation analysis of fused tapered single-mode fibre couplers
Power penalty due to jitter on optical communication systems
Optically bistable operation in InGaAs/lnAIAs MOW laser diodes using resonant tunnelling effect
Prediction of electromagnetic radiation of a multilayer board
  • Author(s): V. Ungvichian  and  R. Perez-Rodriquez
  • Source: Electronics Letters, Volume 23, Issue 14, p. 721 –722
  • DOI:  10.1049/el:19870512
  • Type: Article
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  • p. 721 –722 (2)
    The moment method technique was used to determine the radiation from a multilayer board in the frequency range 30-200 MHz. A portion of clock trace, board ground plane and reflecting plane were modelled using several straight round wires which formed a radiating structure. The equivalent wire radius was obtained from the cross-section of the square traces. The clock pulse information was entered into the computer program in which the frequency spectrum was determined. The amplitude of each spectrum represented the peak voltage source fed into the radiating structure. Comparisons between the measured and calculated data indicated that the moment method technique can provide an excellent prediction, provided that the input impedances of the chip are known at every frequency.
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Enhanced Schottky barrier heights on n-type Ga0.47In0.53As by Be implantation
Wide temperature range of stable single-mode operation in weakly coupled asymmetric mirror reflectivity DFB lasers
  • Author(s): H. Soda ; K. Kihara ; M. Furutsu ; M. Matsuda ; H. Seki ; S. Ogita ; H. Ishikawa ; H. Imai
  • Source: Electronics Letters, Volume 23, Issue 14, p. 724 –725
  • DOI:  10.1049/el:19870514
  • Type: Article
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  • p. 724 –725 (2)
    A maximum difference between the peak gain wavelength and the lasing wavelength where stable DFB mode operation is achieved has been obtained for weakly coupled (KL̃; 0–7), asymmetric mirror structure (Rf = 5%, Rr = 31%) DFB lasers. DFB lasers optimally fabricated exhibit single-longitudinal-mode operation over a wide temperature range of 5–100°C.
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Fully implanted GaAs millimetre-wave mixer diode using high energy implantation
GaAs monolithic Schottky junction pairs for W-band crossbar mixers
Electrothermally excited silicon beam mechanical resonators
Perfect binary arrays with 36 elements
Advances in electrical properties of plasma-grown oxides of silicon
Effect of process parameters on plasma-enhanced chemical vapour deposition of tungsten
  • Author(s): C.M.T. Hodson  and  J. Wood
  • Source: Electronics Letters, Volume 23, Issue 14, p. 733 –735
  • DOI:  10.1049/el:19870520
  • Type: Article
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  • p. 733 –735 (3)
    Films of tungsten have been deposited on substrates of silicon by plasma-enhanced chemical vapour deposition, using the reaction of tungsten hexafluoride and hydrogen. The sheet resistance and adhesion of the films has been studied as a function of substrate temperature, gas composition and flow rate, and other reaction parameters, and an activation energy of 0.23 eV is proposed for the reaction. Reliable tungsten films with sheet resistances of the order of 1Ω/□ can be produced.
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Guided-wave multi/demultiplexers with compensation for centre wavelength shift by fabrication process fluctuations
  • Author(s): K. Imoto ; H. Sano ; M. Miyazaki
  • Source: Electronics Letters, Volume 23, Issue 14, p. 735 –736
  • DOI:  10.1049/el:19870521
  • Type: Article
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  • p. 735 –736 (2)
    A new multi/demultiplexer is proposed together with its fabrication method, which can compensate for the centre wavelength shift Δλ0 caused by fabrication process fluctuations. This device consists of a directional coupler with three different-refractive-index (nb, nw and nc) layers; i.e. an underlayer with index nb, a middle core waveguide layer with index nw and an upper layer with index nc (nw > nc, nw > nb and nc ≠ nb). In the method, Δλ0 can be compensated for selecting the optimum nc, which is calculated by measuring deviations in core widths, core heights and waveguide separation before coating the waveguides with cladding material. Then, cladding material with the optimum nc is coated on to the core waveguides. This method offers high reproducibility and stability.
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Stress-induced index change for K+-Na+ ion exchange in glass
2 Gbit/s timing recovery circuit using dielectric resonator filter
Signal level degradation due to snow accretion on a radome
Explicit formulation of delays in CMOS VLSI
Novel fully differential MOS transconductor for integrated continuous-time filters
Ultra-high-power quasi-CW monolithic laser diode arrays with high power conversion efficiency
Embedding data in DSB-AM using zero-synchronous modulation
Analytical investigation of LOS multipath propagation
Effect of curvature on characteristics of rectangular patch antenna
  • Author(s): J.S. Dahele ; R.J. Mitchell ; K.M. Luk ; K.F. Lee
  • Source: Electronics Letters, Volume 23, Issue 14, p. 748 –749
  • DOI:  10.1049/el:19870530
  • Type: Article
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  • p. 748 –749 (2)
    The effect of curvature on the characteristics of a rectangular patch antenna is studied theoretically and experimentally. For the TM01 mode it is found that the resonant frequency is not affected by curvature. However, as curvature increases the pattern broadens, the resonant resistance decreases, the Q-factor is smaller and the bandwidth is larger. Good agreement between theory and experiment is obtained.
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Resonant coupled stub in nonradiative dielectric waveguide
Frequency stabilisation of FDM optical signals
  • Author(s): B. Glance ; P.J. Fitzgerald ; K.J. Pollack ; J. Stone ; C.A. Burrus ; G. Eisenstein ; L.W. Stulz
  • Source: Electronics Letters, Volume 23, Issue 14, p. 750 –752
  • DOI:  10.1049/el:19870532
  • Type: Article
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  • p. 750 –752 (3)
    Frequency confinement of FDM optical signals to a comb of equally spaced frequencies has been demonstrated. The result was achieved by locking the frequencies of three optical sources to three different resonances of a fibre Fabry-Perot resonator. The frequency spacing between the frequency-locked signals was adjusted to be 500 MHz, the spacing between adjacent resonances, or a multiple of this value. Implementation of the frequency stabilisation circuit requires only a fibre Fabry-Perot resonator, a photodetector and simple electronics. Such a simple circuit provides the means to frequency-stabilise a large number of FDM optical signals originating from the same location.
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Design of a high-gain, single-stage operational amplifier for GaAs switched-capacitor filters
Dependence of central-lobe output power on fill factor of an in-phase laser array
  • Author(s): J.E. Epler ; R.L. Thornton ; T.L. Paoli
  • Source: Electronics Letters, Volume 23, Issue 14, p. 754 –755
  • DOI:  10.1049/el:19870534
  • Type: Article
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  • p. 754 –755 (2)
    In a multiple-emitter diode laser array, coupled in-phase, a substantial amount of the output power is radiated in off-axis lobes. An approximate calculation of the central (0°) lobe output power of an in-phase array as a function of emitter width and array spacing is presented. The results for an array of Gaussian emitters indicate that a near-field fill factor of 70% is required to obtain 95% of the output power in the central lobe.
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Buried-heterostructure diode lasers with in-situ-grown self-aligned GaAs mask for Zn diffusion
Chromatic dispersion limitations in coherent optical fibre transmission systems
  • Author(s): A.F. Elrefaie ; R.E. Wagner ; D.A. Atlas ; D.G. Daut
  • Source: Electronics Letters, Volume 23, Issue 14, p. 756 –758
  • DOI:  10.1049/el:19870536
  • Type: Article
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  • p. 756 –758 (3)
    Computer simulation results indicate that the chromatic dispersion limitation in coherent single-mode-fibre systems is more severe than in direct-detection systems. As an example, for transmission through 100km of fibre at 1550nm, where chromatic dispersion is 15ps/km nm, the modulation rate that produces 2dB dispersion penalty ranges from 5 to lOGbit/s, depending on the modulation format.
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Distributed-feedback, surface-emitting laser diode with lateral double heterostructure
Optimised pulse-width modulation method of forced commutated cycloconvertor
Extremely high-quality GaInAs/AlInAs single quantum wells grown by molecular beam epitaxy
  • Author(s): E.G. Scott ; S.T. Davey ; G.J. Davies
  • Source: Electronics Letters, Volume 23, Issue 14, p. 761 –763
  • DOI:  10.1049/el:19870539
  • Type: Article
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  • p. 761 –763 (3)
    Conventional molecular beam epitaxy (MBE) has been used to grow extremely high-quality single quantum wells in the GaInAs/AlInAs materials system. GaInAs wells varying in thickness from 6.7 Å to 122Å are clearly resolved in the 4K photoluminescence spectrum. Emission from the narrowest quantum well was observed at 897.3 nm, which we believe is at a shorter wavelength than any previously reported for GalnAs quantum wells. The FWHM of the luminescence lines are, in some instances, nearly an order of magnitude narrower than any previously recorded for this materials system.
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Erratum: Direct two's-complement algorithm for XY ± Z
Erratum: Computer simulation of SC circuits using NAP

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