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Online ISSN 1350-911X Print ISSN 0013-5194

Electronics Letters

Volume 25, Issue 23, 9 November 1989

Volumes & issues:

Volume 25, Issue 23

9 November 1989

Low-voltage, 50 Ω, GaAs/AlGaAs travelling-wave modulator with bandwidth exceeding 25 GHz
  • Author(s): R.G. Walker ; I. Bennion ; A.C. Carter
  • Source: Electronics Letters, Volume 25, Issue 23, p. 1549 –1550
  • DOI:  10.1049/el:19891041
  • Type: Article
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  • p. 1549 –1550 (2)
    Travelling-wave, Mach-Zehnder electro-optic modulators to a new design in GaAs/AlGaAs are described. Velocity matching, with 50 Ω impedance and high electro-optic efficiency, is achieved using a capacitively loaded stripline approach. Devices with Vx = 4.85 V (λ = 1152 nm) have 3 dB bandwidths of 25.5 GHz, while those with shorter electrodes (Vx = 5.7 V) show no roll-off below 26.5 GHz. The bandwidth/voltage ratio for these devices represents the highest yet reported for any class of electro-optic modulator.
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MOS multiplier/divider cell for analogue VLSI
  • Author(s): N.I. Khachab  and  M. Ismail
  • Source: Electronics Letters, Volume 25, Issue 23, p. 1550 –1552
  • DOI:  10.1049/el:19891042
  • Type: Article
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  • p. 1550 –1552 (3)
    A novel all-MOS continuous-time multiplier/divider parameterised cell is introduced. It comprises eight MOS transistors and a single operational amplifier. The new cell is highly reconfigurable, versatile, extremely simple to design and its output is conveniently programmed via DC control voltages. Some of the many applications of the new cell in analogue VLSI signal processing include analogue multiplication, signal squaring, division, signal inversion, amplitude modulation and RMS/DC conversion. Moreover, the new cell is easily extendable to achieve analogue vector multiplication, and hence it lends itself naturally to analogue MOS VLSI implementation of feedback/feedforward neural networks.
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Voltage transfer function synthesis using current conveyors
Single-chip 2-port adaptors for wave digital filters
  • Author(s): A. Tomlinson  and  A.R. Mirzai
  • Source: Electronics Letters, Volume 25, Issue 23, p. 1553 –1555
  • DOI:  10.1049/el:19891044
  • Type: Article
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  • p. 1553 –1555 (3)
    In recent years, systolic arrays have been widely used for the implementation of signal processing algorithms. The letter reports on the development of a bit-level 2-port systolic adaptor for wave digital filters (WDFs). The 2-port adaptor can be used for the realisation of WDFs based on the cascade of unit elements and lattice analogue filters. The VLSI design of the adaptor is accomplished using the SOLO 1400 design tool.
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Integrated-optic system for high-speed photodetector bandwidth measurements
Multistate degradable system modelling and analysis
  • Author(s): J. Hsieh ; D.R. Ucci ; G.D. Kraft
  • Source: Electronics Letters, Volume 25, Issue 23, p. 1557 –1558
  • DOI:  10.1049/el:19891046
  • Type: Article
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  • p. 1557 –1558 (2)
    A failing digital system may be represented by a multistate Markov diagram in which the system functions in a degraded mode of execution before total failure occurs. The models proposed to date do not consider more than one intermittent fault state, which limits the flexibility of modelling, nor do they take repair into consideration. In the letter we present a very general continuous-parameter Markov model at the processor level. We also show that this model can be generalised to evaluate the reliability and performability of multiprocessor systems. A closed-form solution is also given for the above modelling.
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Far-infra-red microbolometers made with tellurium and bismuth
Bandpass sigma-delta modulation
High-performance Al0.48In0.52As/Ga0.47In0.53As MSM-HEMT receiver OEIC grown by MOCVD on patterned InP substrates
  • Author(s): W.P. Hong ; G.K. Chang ; R. Bhat ; J.L. Gimlett ; C.K. Nguyen ; G. Sasaki ; M. Koza
  • Source: Electronics Letters, Volume 25, Issue 23, p. 1561 –1563
  • DOI:  10.1049/el:19891049
  • Type: Article
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  • p. 1561 –1563 (3)
    We report the first demonstration of a new long-wavelength receiver OEIC comprising an AlInAs/GaInAs MSM detector and an AlInAs/GalnAs HEMT preamplifier. The layer structure was grown by LP-MOCVD on patterned InP substrates, which allowed independent optimisation of the MSM detector and HEMT preamplifier. The MSM detector showed the lowest leakage current yet reported and the HEMT exhibited a transconductance of 260mS/mm. An excellent receiver response to l.7Gbit/s NRZ signals has been obtained.
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High-power 0.98μm GaInAs strained quantum well lasers for Er3+-doped fibre amplifier
  • Author(s): M. Okayasu ; T. Takeshita ; M. Yamada ; O. Kogure ; M. Horiguchi ; M. Fukuda ; A. Kozen ; K. Oe ; S. Uehara
  • Source: Electronics Letters, Volume 25, Issue 23, p. 1563 –1565
  • DOI:  10.1049/el:19891050
  • Type: Article
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  • p. 1563 –1565 (3)
    High-power GalnAs strained quantum well lasers with an emission wavelength of 0.98μ, suitable for Er3+-doped fibre amplifier pumping, have been fabricated. A threshold current of 15 mA and a peak output power as high as 85 mW have been obtained for the ridge waveguide structure with AR/HR facet coating. Highly efficient pumping for the 1.536 μm signals has been confirmed.
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Intelligent learning algorithms for adaptive digital filters
Binary adaptive nonlinear multiplexing
  • Author(s): V.C. Da Rocha  and  E.J. Batista antunes
  • Source: Electronics Letters, Volume 25, Issue 23, p. 1566 –1568
  • DOI:  10.1049/el:19891052
  • Type: Article
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  • p. 1566 –1568 (3)
    Error-correcting properties of a binary adaptive nonlinear multiplexing system which trades channel activity for redundancy are studied. The main results are a family of data channel carriers, a way to establish the multiplex errorcorrection power, and the specification of desirable properties for a set of data channel carriers. Channel activity is extracted at the receiver, directly from the multiplexed signal.
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Analysis of leakage properties of periodic dielectric image guides
Fast electro-optical phase modulators completely measured in frequency and time domains
Vacuum-insulated-gate field-effect transistor
  • Author(s): J. Huang ; R.T. Howe ; H.S. Lee
  • Source: Electronics Letters, Volume 25, Issue 23, p. 1571 –1573
  • DOI:  10.1049/el:19891055
  • Type: Article
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  • p. 1571 –1573 (3)
    A vacuum-insulated-gate field-effect transistor (V1GFET) is fabricated using a modified polysilicon-gate MOS process. The vacuum insulation is formed by first selectively etching the initial SiO2 layer under the polysilicon gate in HF and then depositing LPCVD SiO2 (LTO) to seal the evacuated cavity under the gate. Initial measurements of n-channel FET drain characteristics result in an effective value for the channel-electron mobility × gate capacitance product of k' = μnC' = 21μAV-2, comparable to that of conventional MOSFETs.
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Low-loss, high-δ, single-mode channel waveguides for high-density integrated optical devices
Geometrical birefringence in fibres with D-shaped hole
  • Author(s): Hong Jin  and  Qian Jingren
  • Source: Electronics Letters, Volume 25, Issue 23, p. 1574 –1575
  • DOI:  10.1049/el:19891057
  • Type: Article
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  • p. 1574 –1575 (2)
    Geometrical birefringence in fibres with a D-shaped hole has been investigated in detail by vectorial wave analysis using the improved finite-element method (FEM) in terms of all three components of the magnetic field. A dependence of the modal birefringence on normalised frequency and geometrical parameters is obtained. The highest modal birefringence is found to be about 4.5 × 10-5. This fibre can therefore maintain a single polarisation state to some degree.
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Optically controlled phase shift of Schottky coplanar lines
Polyphase Barker sequences
  • Author(s): L. Bömer  and  M. Antweiler
  • Source: Electronics Letters, Volume 25, Issue 23, p. 1577 –1579
  • DOI:  10.1049/el:19891059
  • Type: Article
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  • p. 1577 –1579 (3)
    Polyphase sequences are time-discrete complex sequences with constant magnitude and variable phase. In this letter polyphase sequences with aperiodic autocorrelation function (ACF) sidelobcs of values less than or equal to 1 are presented. Such sequences are called Barker sequences. Binary Barker sequences with elements 1 or - 1 are only known up to 13 elements. Now, with an iteration scheme, polyphase Barker sequences are found up to 25 elements, except for 20 elements.
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77 K RF SQUID with 1/f noise only below 5 Hz
MESFETs in thin silicon on SIMOX
  • Author(s): H. Vogt ; G. Burbach ; J. Belz ; G. Zimmer
  • Source: Electronics Letters, Volume 25, Issue 23, p. 1580 –1581
  • DOI:  10.1049/el:19891061
  • Type: Article
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  • p. 1580 –1581 (2)
    Si MESFETs have been built into a thin (100nm) Si film on buried oxide implanted wafers. Aluminium has been used as gate material to obtain process compatibility with a highperformance CMOS process. With appropriate back bias the normally-on devices become enhancement-type. The highquality SIMOX substrate provides excellent transconductance, while the thin film reduces two-dimensional effects.
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Nearly back-dissolution-free LPE growth from Sn solutions over gratings for DFB lasers
Integrated optical. acoustically tunable wavelength filter
  • Author(s): J. Frangen ; H. Herrmann ; R. Ricken ; H. Seibert ; W. Sohler ; E. Strake
  • Source: Electronics Letters, Volume 25, Issue 23, p. 1583 –1584
  • DOI:  10.1049/el:19891063
  • Type: Article
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  • p. 1583 –1584 (2)
    A TM/TE convenor is combined with a TE-pass polariser on a common LiNbO3 chip to obtain an integrated optical, acoustically tunable wavelength filter. Its tuning range is 1.45–1.57 μm wavelength with a filter half-width of 2.8 nm. Owing to the combined acoustical/optical strip guide structure used in the mode convenor, a very low acoustic drive power of only 9 mW is required.
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Increase in photoluminescence of Zn-doped p-type InP after hydrogenation
  • Author(s): V. Swaminathan ; J. Lopata ; S.E.G. Slusky ; W.C. Dautremont-Smith ; S.J. Pearton
  • Source: Electronics Letters, Volume 25, Issue 23, p. 1584 –1586
  • DOI:  10.1049/el:19891064
  • Type: Article
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  • p. 1584 –1586 (3)
    We report on the effect of hydrogenation on the lowtempeTature (5.5 K) photoluminescence properties of Zndoped p-type (p ∼ 3 × 1018cm-3) InP substrates. The photoluminescence spectrum of the as-grown sample shows a ZnIn acceptor-related transition near the band-edge at l.386eV, a Zn-related PL band at l.214eV and a phosphorus vacancy Vp-related PL band at 1.01 eV. After hydrogenation of the samples by exposure to hydrogen plasma, which completely passivates the ZnIn acceptors over a depth of more than 1μ, the deep luminescence bands (1.214 and 1.01eV) disappeared, with a concomitant ∼ 2000-fold increase in the intensity of the near-band-edge emission. Such a large increase in radiative efficiency together with the elimination of the deep luminescence bands indicates hydrogen passivation of deep nonradiative centers in addition to passivation of shallow acceptors.
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Fast and accurate method for calculation of polarised modes in semiconductor rib waveguides
  • Author(s): P.W.A. McIlroy ; M.S. Stern ; P.C. Kendall
  • Source: Electronics Letters, Volume 25, Issue 23, p. 1586 –1587
  • DOI:  10.1049/el:19891065
  • Type: Article
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  • p. 1586 –1587 (2)
    A new semivectorial ‘spectral index’ (SI) method for finding the guided modes of semiconductor rib waveguides is described. The results are shown by comparison to be of the same accuracy as well established finite difference calculations. A useful by-product is a contour map of the principal field component. The propagation constants are found using novel transcendental equations which are easy to set up and are given here explicitly. These discriminate clearly between the TE and TM modes and are variational in nature.
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X-band monolithic tunable resonator/filter
Delayed self-homodyne method using solitary monomode fibre for laser linewidth measurements
Phase-matching of optical fibre photorefractive intermodal couplers in infra-red
High-voltage, wavelength-discriminating, light-activated GaAs thyristor
  • Author(s): R.F. Carson ; R.C. Hughes ; T.E. Zipperian ; H.T. Weaver ; T.M. Brennan ; B.E. Hammons ; J.F. Klem
  • Source: Electronics Letters, Volume 25, Issue 23, p. 1592 –1593
  • DOI:  10.1049/el:19891069
  • Type: Article
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  • p. 1592 –1593 (2)
    A GaAs thyristor with 35 V breakover has been fabricated that exhibits large discrimination between light and flash X-ray power levels for triggering. Approximately 108 times more X-ray than light power is needed to switch the device over a bias voltage range of 25 V. This discrimination property represents a form of radiation hardening for a lightactivated switch.
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Reduced bus acquisition time in distributed arbitration systems
  • Author(s): M. Makhaniok ; V. Cherniavsky ; R. MÄnner ; O. Stucky
  • Source: Electronics Letters, Volume 25, Issue 23, p. 1593 –1594
  • DOI:  10.1049/el:19891070
  • Type: Article
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  • p. 1593 –1594 (2)
    A new method for identifying the stable state in distributed arbitration schemes as used in modem multiprocessor buses like Futurebus is suggested. It exploits the dependence of the arbitration time on the arbitration numbers, which is introduced in this letter, the method allows to reduce bus acquisition time without considerable changes to the system, for example by more than a factor of 1.3 for Futurebus. This method allows to improve the performance of standard buses by only introducing individual arbitration delays for bus requestors.
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Optimum coding design for type-I hybrid ARQ error control schemes
Performance analysis of current conveyors
High-quality GaInAs photodiodes grown using tertiarybutylarsine by atmospheric-pressure MOVPE
  • Author(s): D.M. Baker ; W.J. Duncan ; M.D. Learmouth ; T.G. Lynch
  • Source: Electronics Letters, Volume 25, Issue 23, p. 1598 –1600
  • DOI:  10.1049/el:19891073
  • Type: Article
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  • p. 1598 –1600 (3)
    GaInAs was grown by atmospheric-pressure MOVPE using tertiarybutylarsine in place of arsine. Its carbon content was low and its carrier density and mobility were 2×1015cm-3and 50,500 cm2/Vs at 77 K, respectively, comparable with arsine-grown GaInAs. The composition of the GalnAs was, however, sensitive to growth temperature, pin diodes grown from tertiarybutylarsine were comparable with those grown from arsine, having dark currents < 100 pA and capacitance about 0.30 pF.
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FDMA-FSK noncoherent network operated at 600 Mbit/s using two-electrode DFB lasers and fibre optical filter demultiplexer
  • Author(s): A.E. Willner ; I.P. Kaminow ; M. Kuznetsov ; J. Stone ; L.W. Stulz
  • Source: Electronics Letters, Volume 25, Issue 23, p. 1600 –1602
  • DOI:  10.1049/el:19891074
  • Type: Article
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  • p. 1600 –1602 (3)
    We demonstrate a two-channel FDMA-FSK star network using frequency-tunable two-electrode DFB lasers. Channels arc demultiplexed by a tunable fibre Fabry-Perot filter, which also converts the FSK signal to ASK format for noncoherent detection. Bit error rates of 10-13 have been measured at 600 Mbit/s transmission rate for (223-1) word lengths. High bit rate and frequency tunability have thus been combined for use in an FDMA.
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Laser-assisted deposition of BN films on InP for MIS applications
BH lasers with GaInAsP and GaInAs active layers grown by MOVPE using tertiarybutylarsine and tertiarybutylphosphine
  • Author(s): W.J. Duncan ; D.M. Baker ; M. Harlow ; A. English ; A.L. Burness ; J. Haigh
  • Source: Electronics Letters, Volume 25, Issue 23, p. 1603 –1604
  • DOI:  10.1049/el:19891076
  • Type: Article
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  • p. 1603 –1604 (2)
    BH lasers were grown by atmospheric-pressure MOVPE using either PH3 and AsH3 or t-BuPH2 and t-BuAsH2 to produce the active lasing layer. Quaternary (λ = l.5 μm) devices grown from the organic sources approach the quality of hydride-grown devices, with threshold currents of 20 mA and output powers of 6mW. The performance is probably limited by impurities in the t-BuPH2 since GalnAs lasers grown from t-BuAsH2 were identical in performance to GalnAs lasers grown from AsH3. When growing GalnAsP from the organic sources the incorporation of arsenic into the solid phase was nonlinear: similar to that reported for the hydrides.
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VLSI architectures for convolver design using number theoretic transforms
Light-emitting diode as radio-frequency detector: development of RFI-free electromagnetic field sensor
  • Author(s): P.S. Neelakanta  and  D. de Groff
  • Source: Electronics Letters, Volume 25, Issue 23, p. 1606 –1608
  • DOI:  10.1049/el:19891078
  • Type: Article
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  • p. 1606 –1608 (3)
    A unique RFI-free electromagnetic field sensing technique using an LED as an RF detector is described. A double heterojunction (AlGaAs/GaAs) LED is used as an RF rectifier coupled to an EM probe; it delivers proportional light output with significant efficiency even at low (rectified) drive currents. DC biasing of the LED to the threshold of conduction can be achieved by an optically powered photodiode pair. Use of fibre-optic links from the detector to the receiver and in the optically powered bias arrangement eliminates the possibilities of RF1. Presented here are the sensitivity and frequency response of a test probe measured over 3–30 MHz under near-field conditions.
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Four-channel wavelength division multiplexer on Ti:LiNbO3
Formant extraction from phase using weighted group delay function
Analysis of forward wide-angle light propagation in semiconductor rib waveguides and integrated-optic structures
  • Author(s): D. Yevick  and  M. Glasner
  • Source: Electronics Letters, Volume 25, Issue 23, p. 1611 –1613
  • DOI:  10.1049/el:19891081
  • Type: Article
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  • p. 1611 –1613 (3)
    We analyse longitudinally varying semiconductor rib waveguides with a new nonparaxial wide-angle equation for unidirectional light propagation. We further develop a solution method involving multiplication of the incoming electric field by a series of unitary operators which are evaluated by splitstep fast Fourier transform and finite difference techniques. In the test case of a strongly guiding rib waveguide Yjunction, the estimated losses nearly coincide with those of standard Fresnel equation procedures. We also present a numerical analysis of an integrated-optic lens, demonstrating significant errors in previous results. Finally, we explicitly illustrate the increased accuracy of our new method in comparison to the Fresnel equation for a highly nonparaxial Gaussian beam.
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Erratum: Spectral linewidth of AlGaAs/GaAs surface-emitting laser

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