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Online ISSN 1350-911X Print ISSN 0013-5194

Electronics Letters

Volume 26, Issue 19, 13 September 1990

Volumes & issues:

Volume 26, Issue 19

13 September 1990

Generalised theory of a non-TEM transmission line taper without discontinuities
Spread-spectrum optical fibre network based on pulsed coherent correlation
  • Author(s): D.D. Sampson  and  D.A. Jackson
  • Source: Electronics Letters, Volume 26, Issue 19, p. 1550 –1552
  • DOI:  10.1049/el:19900995
  • Type: Article
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  • p. 1550 –1552 (3)
    Coherent recombination of a series of pulses derived from a single laser pulse by matched filtering, using optical ladder networks is shown to result in a highly single-peaked correlation function. The technique may be used in a local area network based on a star topology when this coherent correlation is generated using a low coherence source. This provides a more practical but equally powerful alternative to other current proposals.
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Results of site-diversity radiometric measurements at Ku-band in brazil
Simple method to calculate the maximum user density for microwave point-to-point links
Novel merged BiCMOS circuit structures
Luminescent Er doped microparticles in a semiconductor matrix
  • Author(s): P.N. Favennec ; H. L'Haridon ; D. Moutonnet ; M. Salvi ; A.C. Papdopoulo
  • Source: Electronics Letters, Volume 26, Issue 19, p. 1556 –1558
  • DOI:  10.1049/el:19900999
  • Type: Article
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  • p. 1556 –1558 (3)
    The rare earth element erbium was implanted into various semiconductors. Photoluminescence of the erbium implanted layer is studied. The peak wavelength is centred at 1.54 =m wavelength and has about the same maximum intensity whatever the host material is. Results of cathodoluminescence from a scanning electron microscope revealed that the 1.54 =m emission is not uniformly dispersed at the surface. The 1.54 =m emission could be from microparticles of Er-rich compounds.
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Analysis of the superconducting coplanar waveguide by combining spectral domain method and phenomenological equivalence method
  • Author(s): K.-S. Kong ; C.W. Kuo ; T. Kitazawa ; T. Itoh
  • Source: Electronics Letters, Volume 26, Issue 19, p. 1558 –1560
  • DOI:  10.1049/el:19901000
  • Type: Article
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  • p. 1558 –1560 (3)
    A conductor loss of the high Tc superconducting coplanar waveguide (CPW) is calculated by combining the spectral domain method (SDM) and the phenomenological equivalence method (PEM). An inductance of CPW is calculated by the SDM and the geometric factor is then calculated by using a numerical derivative of the inductance. This calculated geometric factor of the CPW is used in the PEM to calculate the conductor loss. Owing to the combination of the accurate analysis of CPW by SDM and PEM, the merits of two methods are obtained, which are: better accuracy, simple and fast calculation, and applicability to any case of penetration depth compared with the conductor thickness
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Electro-optic polarisation convertor on (110) InP
Modified Hebbian auto-adaptive impulse neural circuits
  • Author(s): N. Nintunze  and  A. Wu
  • Source: Electronics Letters, Volume 26, Issue 19, p. 1561 –1563
  • DOI:  10.1049/el:19901002
  • Type: Article
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  • p. 1561 –1563 (3)
    Artificial neural networks learn by adapting interconnection weights. A generalised weight adaptation expression for associative learning has been implemented using synapse circuits based on floating gate devices. A reinforcement depending on the correlation of a synapse input and a neuronal output is used. The circuits also illustrate the influence of the conditioning stimuli amplitude on the conditioning rate.
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Large amplitude picosecond step generation with FETs
  • Author(s): A. Ouslimani ; G. Vernet ; H. Hafdallah ; R. Adde
  • Source: Electronics Letters, Volume 26, Issue 19, p. 1563 –1564
  • DOI:  10.1049/el:19901003
  • Type: Article
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  • p. 1563 –1564 (2)
    A two stage FET picosecond step sharpener driven by a 95 ps large-signal generator is realised, tested and simulated. Transistor nonlinearities, as well as propagation effects, are precisely modelled. Dynamic waveforms of the step response are measured and analysed. A 24 ± 4 ps intrinsic output time response and 2 V amplitude are obtained. These results demonstrate FET potential to regenerate and compress large-signal picosecond steps.
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Modified backpropagation algorithm for fast learning in neural networks
Cerenkov third-harmonic generation in optical glass fibre
Grafted GaAlAs rib waveguides on an InP substrate
  • Author(s): A. Yi-Yan ; M. Seto ; T.J. Gmitter ; D.M. Hwang ; L.T. Florez
  • Source: Electronics Letters, Volume 26, Issue 19, p. 1567 –1569
  • DOI:  10.1049/el:19901006
  • Type: Article
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  • p. 1567 –1569 (3)
    Rib waveguides were fabricated on a 1.4 µm thick GaAlAs epilayer grafted on the surface of a semiinsulating InP substrate by epitaxial lift-off. Single-mode waveguides with propagation losses (< 7 dB/cm) lower than heteroepitaxially grown counterparts have been achieved. TEM analysis on the GaAlAs/InP interface indicates surface scattering as one of the main loss mechanisms.
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Photon timing OTDR: a multiphoton backscattered pulse approach
Improved allan variance real-time processing system to measure frequency tracking error of heterodyne optical phase-locked loops
  • Author(s): C.-H. Shin  and  M. Ohtsu
  • Source: Electronics Letters, Volume 26, Issue 19, p. 1571 –1572
  • DOI:  10.1049/el:19901008
  • Type: Article
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  • p. 1571 –1572 (2)
    The performance of an Allan variance measuring system was drastically improved by employing time interval analysis incorporating a beat frequency method. It was used to evaluate the performance of a heterodyne optical phase-locked loop with a very low optical frequency tracking error of 0.4mHz at the integration time of 70s. Advantages of the system are precise measurement for highly stable frequency sources with good reproducibility and simple structure.
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New adaptive Viterbi detector for fast-fading mobile-radio channels
Proposed semiconductor narrow-band wavelength filter using directional coupler
Modified scatterer distribution model for fast fading mobile communication channel
Over 350 km CPFSK repeaterless transmission at 2.5 Gbit/s employing high-output power erbium-doped fibre amplifiers
Temperature dependence of second harmonic generation in germania-doped silica optical fibres
New analogue four-quadrant voltage divider
  • Author(s): A. Cichocki  and  R. Unbehauen
  • Source: Electronics Letters, Volume 26, Issue 19, p. 1580 –1582
  • DOI:  10.1049/el:19901014
  • Type: Article
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  • p. 1580 –1582 (3)
    A new circuit structure for the realisation of an analogue four-quadrant voltage divider with improved dynamic performance is proposed. The structure was developed on the basis of the augmented Lagrangian method and the gradient optimisation approach. The circuit is especially suited for monolithic IC implementation by employing the CMOS switched-capacitor (SC) techniques. The device has been built using SC discrete components and also simulated on computer. Experimental test and computer simulation results have confirmed the theoretical predictions, especially the dynamic error reduction of the device.
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New skin-effect equivalent circuit
  • Author(s): T. Vu Dinh ; B. Cabon ; J. Chilo
  • Source: Electronics Letters, Volume 26, Issue 19, p. 1582 –1584
  • DOI:  10.1049/el:19901015
  • Type: Article
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  • p. 1582 –1584 (3)
    An accurate equivalent network for modelling the skin-effect is presented. No specific approximation in the frequency behaviour is used. The method is therefore applicable whatever the geometry of the microstrip line, especially when the thickness is greater than the width. The frequency-dependent parameters of a transmission microstrip line as well as the attenuation are simulated using SPICE. Very good agreement is obtained with other published results.
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Progressive bounds on merit factor
675 mW diffraction limited operation and thermal characteristics of laser diode arrays in an external cavity
  • Author(s): R.G. Waarts ; D. Mehuys ; D.F. Welch ; W. Streifer
  • Source: Electronics Letters, Volume 26, Issue 19, p. 1586 –1588
  • DOI:  10.1049/el:19901017
  • Type: Article
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  • p. 1586 –1588 (3)
    A compact external cavity configuration consisting of a high power gain guided laser array, a graded index lens and a mode selective mirror was investigated. The laser array was stabilised in a single spatial mode to an output power of 950 mW with 675 mW in a diffraction limited lobe under pulsed operation. The spatial mode properties of the external cavity are also correlated to thermal lasing effects in good agreement with theory.
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Very low voltage, normally-off asymmetric Fabry–Perot reflection modulator
Continuous wave top surface emitting quantum well lasers using hybrid metal/semiconductor reflectors
  • Author(s): G. Hasnain ; K. Tai ; J.D. Wynn ; Y.H. Wang ; R.J. Fischer ; M. Hong ; B.E. Weir ; G.J. Zydzik ; J.P. Mannaerts ; J. Gamelin ; A.Y. Cho
  • Source: Electronics Letters, Volume 26, Issue 19, p. 1590 –1592
  • DOI:  10.1049/el:19901019
  • Type: Article
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  • p. 1590 –1592 (3)
    Continuous wave lasing at room temperature of vertical cavity top surface emitting quantum well lasers using hybrid metal/semiconductor reflectors is demonstrated. Semi-transparent metal films, about 350 Å thick, are used with a reduced number of periods of distributed Bragg reflectors to form a hybrid top mirror with greatly reduced electrical resistance. Voltage at a threshold current of 11 mA is as low as 3.2 V and 100Ω differential series resistance is obtained with lO =m diameter devices. Improved uniformity and yield were obtained using silver/gold thin films deposited in-situ under ultra-high vacuum after molecular beam epitaxial growth of the semiconductor layers.
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20 Gbit/s soliton transmission over 200 km using erbium-doped fibre repeaters
High-performance algorithmic switched-current memory cell
Computer simulation of indoor data channels with a linear adaptive equaliser
GaAs MESFET differential pass-transistor logic
  • Author(s): J.H. Pasternak  and  C.A.T. Salama
  • Source: Electronics Letters, Volume 26, Issue 19, p. 1597 –1598
  • DOI:  10.1049/el:19901023
  • Type: Article
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  • p. 1597 –1598 (2)
    A GaAs MESFET implementation of differential pass-transistor logic (DPTL) is presented. This logic technique combines the greater area efficiencies and high operation speeds of ratioless, pass-transistor circuits with the additional advantages of good noise immunity and low power dissipation. Experimental results are provided for a four-bit counter implemented in a 1 =m, depletion (D)-mode MESFET technology to demonstrate both the functionality and noise immunity of GaAs DPTL.
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Chirp and linewidth enhancement factor α of current modulated Ga(Al)As-GRINSCH-SQW-MCRW flared waveguide lasers
  • Author(s): M. Heinrich  and  M. Claassen
  • Source: Electronics Letters, Volume 26, Issue 19, p. 1598 –1600
  • DOI:  10.1049/el:19901024
  • Type: Article
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  • p. 1598 –1600 (3)
    The frequency deviation (‘chirp’) of two current modulated Ga(Al)As-GRINSCH-SQW-MCRW flared waveguide lasers was measured with a phase-sensitive Michelson interferometer. Their linewidth enhancement a phase-sensitive Michelson interferometer. Their linewidth enhancement factor could be determined to be as low as α = +2.2 and α = +2.4 including the confirmation of the sign according to the definition used. At low modulation frequencies the lasers exhibited an excess chirp with a magnitude strongly decreasing with increased bias current and a FM-to-AM phase shifting from 180° down to 0°.
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Room temperature vertical cavity GaAs/AlGaAs surface emitting injection laser
  • Author(s): C. Wüthrich ; J.H. James ; J.D. Ganière ; F.K. Reinhart
  • Source: Electronics Letters, Volume 26, Issue 19, p. 1600 –1601
  • DOI:  10.1049/el:19901025
  • Type: Article
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  • p. 1600 –1601 (2)
    A vertical cavity GaAs/AlGaAs top surface emitting injection laser (SEIL) has been fabricated using a simple planar technology. The laser has a low series resistance (40 Ω) and works at room temperature in pulsed operation with a duty cycle up to 35% and a threshold current of 55 mA. We obtained monomode operation at 896 nm wavelength, with a linewidth less than 1.5 Å. Both single SEILs and two dimensional SEIL arrays has been fabricated.
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Cryptanalysis of new modified Lu-Lee cryptosystems
Extending sizes of effective convolution algorithms
152 photons per bit detection at 622 Mbit/s to 2.5 Gbit/s using an erbium fibre preamplifier
Ba(Zn1/3Ta2/3)O3–Ba(Cd1/3Nb2/3)O3 dielectric ceramics with low microwave loss
‘On-spot’ interferometric optical coherence domain polarimetry for quasi-distribute temperature sensors
  • Author(s): S. Chen  and  I.P. Giles
  • Source: Electronics Letters, Volume 26, Issue 19, p. 1607 –1608
  • DOI:  10.1049/el:19901030
  • Type: Article
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  • p. 1607 –1608 (2)
    A novel ‘quasi-distributed’ optical fibre interferometric sensor system is described. The positions of the sensors along an optical high-birefringence fibre are located by employing ‘white-light’ interferometry when each sensor is a local interferometer producing independent measurand-induced phase signals. The experimental results with the system configured as a distributed temperature sensor are also presented.
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Programmable fractional sample delay filter with Lagrange interpolation
Very linear CMOS floating resistor
  • Author(s): J. Silva-Martinez ; M. Steyaert ; W. Sansen
  • Source: Electronics Letters, Volume 26, Issue 19, p. 1610 –1611
  • DOI:  10.1049/el:19901032
  • Type: Article
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  • p. 1610 –1611 (2)
    A very linear CMOS floating resistor is introduced. The proposed topology takes advantage of the MOS transistor characteristics biased in the linear region. It is claimed that the resistor linearity can be improved by reducing the AC voltage swing in the transistor terminals, the drain and the source, and using the linear behaviour between the gate voltage and the drain current. Simulated results, even in the presence of large transistors mismatches, have shown that the total harmonic distortion (THD) is lower than 0.1% for applied voltages up to 2 V peak to peak, VPTP. Resistance values of 500Ω and a frequency response up to 10MHz have been simulated in a typical 3 =m CMOS process. The supply voltages was only ± 2.5 V.
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Backlog performance of some controlled slotted ALOHA systems
Reduction of the propagation losses in impurity disordered quantum well waveguides
Full-wave analysis of shielded coplanar waveguide short-end
Fast cosine transform based on the successive doubling method
Fast encoding algorithm for VQ-based image coding
Noise characteristics of polarisation sensitive optically preamplified receivers
Field demonstration of two channel coherent transmission with a diode-pumped fibre amplifier repeater
  • Author(s): M.J. Creaner ; R.C. Steele ; D. Spirit ; G.R. Walker ; N.G. Walker ; J. Mellis ; S.AL. Chalabi ; W. Hale ; I. Sturgess ; M. Rutherford ; D. Trivett ; M. Brain
  • Source: Electronics Letters, Volume 26, Issue 19, p. 1621 –1623
  • DOI:  10.1049/el:19901039
  • Type: Article
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  • p. 1621 –1623 (3)
    A field demonstration of two channel 622 Mbit/s DPSK and FSK coherent transmission over 200 km of installed terrestrial fibre and unrepeatered over 264 km of undersea fibre is reported. Diode-pumped erbium-doped fibre amplifiers were used as power boosters and multi-wavelength repeaters. The maximum launch power of the amplifiers was > + 15dBm and the amplifiers exhibited repeater gains of ˜30dB.
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Soft switch-avalanche IGBT convertor
Proposal for a versatile monolithic multi-Gbit/s m-sequence test system
  • Author(s): M. Bußmann  and  U. Langmann
  • Source: Electronics Letters, Volume 26, Issue 19, p. 1625 –1626
  • DOI:  10.1049/el:19901041
  • Type: Article
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  • p. 1625 –1626 (2)
    A multi-functional system is proposed which combines four important features for m-sequence applications: Generation of m-sequences, detection of bit errors, derivation of word synchronisation pulses, and scrambling as well as descrambling of a data stream. Circuit simulations show that a monolithic realisation for data rates of more than 10Gbit/s is feasible using a simple self-aligning Si bipolar technology.
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Design and fabrication of two layer anti-reflection coatings for semiconductor optical amplifiers
90% coupling of top surface emitting GaAs/AlGaAs quantum well laser output into 8 µm diameter core silica fibre
  • Author(s): K. Tai ; G. Hasnain ; J.D. Wynn ; R.J. Fischer ; Y.H. Wang ; B. Weir ; J. Gamelin ; A.Y. Cho
  • Source: Electronics Letters, Volume 26, Issue 19, p. 1628 –1629
  • DOI:  10.1049/el:19901043
  • Type: Article
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  • p. 1628 –1629 (2)
    Top surface emitting GaAs/AIGaAs quantum well lasers were fabricated to exhibit stable single longitudinal and two-dimensional Gaussian-like transverse mode emission characteristics under room temperature continuous wave operation with threshold currents of less than 3 mA. Efficient coupling of laser outputs to 8 µm diameter core silica fibres was achieved through butt-coupling with coupling coefficients of 90% and 50% for fibres with etched lens-like end and flat cleaved end, respectively.
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Extension of the T-gate concept to a hybrid U-gate architecture for ternary and higher order logic systems
  • Author(s): J.A.C. Webb  and  S.J. Laverty
  • Source: Electronics Letters, Volume 26, Issue 19, p. 1629 –1630
  • DOI:  10.1049/el:19901044
  • Type: Article
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  • p. 1629 –1630 (2)
    A hybrid gate structure is described enabling multiple valued logic (MVL) combinational functions to be implemented using a single building block. In particular, a three-input ternary universal gate (U-gate) is considered having an equivalent functional capability of 13 T-gates. Ease of MVL system design and the prospect of hybrid ASIC implementation are noted as potential benefits justifying increased primitive module complexity.
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Self adjusting weights for hardware neural networks
Heterojunction field effect transistor laser
Modelling of electron mobility in silicon MOS inversion and accumulation layers at liquid helium temperature
  • Author(s): I.M. Hafez ; A. Emrani ; G. Ghibaudo ; F. Balestra
  • Source: Electronics Letters, Volume 26, Issue 19, p. 1633 –1635
  • DOI:  10.1049/el:19901047
  • Type: Article
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  • p. 1633 –1635 (3)
    A study of the effective mobility in silicon MOS inversion and accumulation layers at liquid helium temperature is reported. It is demonstrated, using MOS devices of various technologies, that theeffective mobility, =eff, at liquid helium temperature can be represented by a bell-shaped function of the inversion (or accumulation) charge Qn which has the generic form=eff(Qn) = 2=m/Qn/Qm+QmQnwhere =m is the maximum mobility and Qm a critical charge of the order of 1–3 × 1012q/cm2, which are parameterised functions of the bulk charge in the case of enhancement-mode devices. This mobility law, which can be considered as a universal feature of the transport at the Si–SiO2 interface, enables an analytical modelling of enhancement and depletion mode MOS transistors to be obtained at liquid helium temperature.
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