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Online ISSN 1350-911X Print ISSN 0013-5194

Electronics Letters

Volume 26, Issue 24, 22 November 1990

Volumes & issues:

Volume 26, Issue 24

22 November 1990

Two new ternary line codes
‘Synchronous’ CDMA demonstration for fibre-optic networks with optical processing
  • Author(s): W.C. Kwong  and  P.R. Prucnal
  • Source: Electronics Letters, Volume 26, Issue 24, p. 1990 –1992
  • DOI:  10.1049/el:19901287
  • Type: Article
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  • p. 1990 –1992 (3)
    ‘Synchronous’ code-division multiple-access (S/CDMA) for fibre-optic networks with optical processing is investigated. A two-user experiment demonstrating the feasibility of such a network is performed at 10 Mbit/s (500 Mchip/s) using modified prime sequence codes and optical processing. Fibre-optic delay-lines are used for code sequence generation and correlation without using fast electronic components. An environment in which S/CDMA would be particularly suitable is discussed.
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High-efficiency coupling of laser diodes in tapered proton-exchanged waveguides
Magnetostatic wave mixer
Analysis of ‘D type’ flip-flop frequency changers
  • Author(s): D.I. Shaw ; J.C. Bennett ; A.M. Clements
  • Source: Electronics Letters, Volume 26, Issue 24, p. 1995 –1997
  • DOI:  10.1049/el:19901290
  • Type: Article
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  • p. 1995 –1997 (3)
    A novel approach using Fourier analysis to model a digital system, in this case a ‘D type’ flip-flop, is presented. An analysis of the flip-flop using mathematics, with a graphical example to illustrate the logic operation of the flip flop as a frequency changer, in this case a down-convertor, is presented. This type of analysis could prove invaluable in modelling digital phase locked loops and frequency synthesisers.
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Overconstrained version of moment method for prediction of electromagnetic energy deposition inside dielectric objects
  • Author(s): S. Caorsi ; G.L. Gragnani ; M. Pastorino
  • Source: Electronics Letters, Volume 26, Issue 24, p. 1997 –1998
  • DOI:  10.1049/el:19901291
  • Type: Article
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  • p. 1997 –1998 (2)
    An overconstrained version of the moment method is presented that is based on a redundant number of testing functions and the use of a pseudoinversion transformation to solve the related overdetermined system of equations. Preliminary results prove that numerical solutions to electromagnetic scattering problems involved in SAR calculation can also be reached by using limited computer resources.
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Coplanar-waveguide/microstrip probe coupler and applications to antennas
  • Author(s): R.N. Simons  and  R.Q. Lee
  • Source: Electronics Letters, Volume 26, Issue 24, p. 1998 –2000
  • DOI:  10.1049/el:19901292
  • Type: Article
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  • p. 1998 –2000 (3)
    A method to couple microwave power from a coplanar waveguide to a microstrip line on opposite sides of a ground plane is demonstrated. The coupler uses a metallic post which passes through an aperture on the ground plane connecting the strip conductor of the coplanar waveguide to the microstrip line. The measured insertion loss and return loss are about 1 dB and 10 dB, respectively, across the frequency range of 0.045–6.5 GHz. To demonstrate potential applications of the coupler as a feeding network for a microstrip patch array, measured radiation patterns of two rectangular patch antennas with a direct coplanar-waveguide/microstrip feed and with a proximity coupled coplanar-waveguide/microstrip feed are presented.
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High frequency Pnp AlGaAs/InGaAs heterojunction bipolar transistor with an ultrathin strained base
  • Author(s): W.U. Liu ; D. Hill ; D. Costa ; J.S. Harris
  • Source: Electronics Letters, Volume 26, Issue 24, p. 2000 –2002
  • DOI:  10.1049/el:19901293
  • Type: Article
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  • p. 2000 –2002 (3)
    High performance Pnp AlGaAs/InGaAs heterojunction bipolar transistors (HBTs) have been fabricated. The transistors have a 300 Å strained InGaAs base, with indium composition linearly graded from 0 to 15%. The cutoff frequency and maximum oscillation frequency for a transistor with emitter area of 2 × 8 μm2 are measured to be 23.3 GHz and 40 GHz, respectively, at a collector current of −10 mA. These are the highest published results for Pnp HBTs.
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Correlation of relative intensity noise with linewidth floors in narrow linewidth DFB lasers
Direct observation of shot noise in linewidth broadening of DBR lasers
Cascadable current-mode single CCII biquads
  • Author(s): S.-I. Liu ; H.-W. Tsao ; J. Wu
  • Source: Electronics Letters, Volume 26, Issue 24, p. 2005 –2006
  • DOI:  10.1049/el:19901296
  • Type: Article
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  • p. 2005 –2006 (2)
    A new configuration for the realisation of current-mode single-CCII-biquad (SCB) filters with high output impedance is presented. It can synthesise lowpass, bandpass, highpass, notch, and allpass filtering functions with a single CCII connected to five passive RC one-port elements. The quality factor, Q, and the central frequency, ω0, of the proposed SCBs are insensitive to the current tracking error of the CCII. These SCBs have the advantages of low passive sensitivities and independently adjustable ω0 or Q
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Effects of ice depolarisation on Ka-band satellite-Earth path in stratus rainfall events
All-optical loop mirror switch employing an asymmetric amplifier/attenuator combination
Novel high precision alignment technique for polarisation maintaining fibres using a frequency modulated tunable laser
Multiple quantum well directional coupler as a self-electro-optic effect device
  • Author(s): B.P. Keyworth ; M. Cada ; J.M. Glinski ; A.J. Springthorpe ; C. Rolland ; K.O. Hill
  • Source: Electronics Letters, Volume 26, Issue 24, p. 2011 –2013
  • DOI:  10.1049/el:19901300
  • Type: Article
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  • p. 2011 –2013 (3)
    Self-electro-optic effect devices (SEEDs) have recently received much attention due in part to their versatility and performance. However, the work to date has concentrated on electro-optic modulators which respond in some way to an optical signal. A report is made here on results obtained with a GaAs/AlGaAs multiple quantum well directional coupler configured as a SEED device. A robust optical switching operation is demonstrated with a high contrast ratio and constant output power.
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Silicon implementation of a function of visual peripheral processes
Dielectric resonator antenna using aperture coupling
  • Author(s): J.T.H.ST. Martin ; Y.M.M. Antar ; A.A. Kishk ; A. Ittipiboon ; M. Cuhaci
  • Source: Electronics Letters, Volume 26, Issue 24, p. 2015 –2016
  • DOI:  10.1049/el:19901302
  • Type: Article
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  • p. 2015 –2016 (2)
    A practical antenna configuration for use at microwave and millimetre wave frequencies is investigated. It consists of a circular cylindrical dielectric resonator fed by a microstrip feedline through a coupling aperture in the ground plane between them. Several elements, with different physical parameters, operating between 14 and 16GHz were constructed and tested. Experimental results confirm the effective and practical performance of the antenna structure.
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5V, DC-12 GHz InP/InGaAs HBT amplifier
  • Author(s): R.N. Nottenburg ; M. Banu ; B. Jalali ; D.A. Humphrey ; R.K. Montgomery ; R.A. Hamm ; M.B. Panish
  • Source: Electronics Letters, Volume 26, Issue 24, p. 2016 –2018
  • DOI:  10.1049/el:19901303
  • Type: Article
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  • p. 2016 –2018 (3)
    An InP/InGaAs HBT cascode amplifier operating from a single 5 V power supply is described. The circuit has a DC gain of 17.2 dB and a −3 dB frequency point of 12.3 GHz. This results in a gain-bandwidth product in excess of 90 GHz. The frequency response of the amplifier remains constant if the power supply voltage is as low as 4 V.
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Comparison of DFB laser linewidth measurement techniques: results from COST 215 round robin
  • Author(s): M.O. van Deventer ; P. Spano ; S.K. Nielsen
  • Source: Electronics Letters, Volume 26, Issue 24, p. 2018 –2020
  • DOI:  10.1049/el:19901304
  • Type: Article
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  • p. 2018 –2020 (3)
    An interlaboratory comparison on four different linewidth measurement techniques was performed for twelve DFB lasers from various manufacturers. The measured linewidths agreed very well for the lasers that had a flat frequency noise spectrum. Differences of more than a factor of 2 in measured linewidth for some of the other lasers could be explained by an increased level of the low frequency noise spectrum recognised by a Michelson interferometer. The conclusion was made that the application of the laser determines what is the best definition of linewidth and which is the best method for its measurement.
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Construction of block modulation codes over rings for fading channels
Measurement of intermodal coupling in weakly multimode fibre optics
Digital passband filtering of megabaud transmitted data stream
Residual and absolute timing jitter in actively mode-locked semiconductor lasers
Digital demodulation by a non-coherent differential PSK modem
Compact low-voltage InGaAs/InAlAs multiple quantum well waveguide interferometers
Approximate expression for normalised throughput of multistage interconnection networks
Wavelength-tunable single-frequency and single-polarisation er-doped fibre ring-laser with 1.4 kHz linewidth
Strained-layer 1.5 μm wavelength InGaAs/InP multiple quantum well lasers grown by chemical beam epitaxy
  • Author(s): W.T. Tsang ; M.C. Wu ; L. Yang ; Y.K. Chen ; A.M. Sergent
  • Source: Electronics Letters, Volume 26, Issue 24, p. 2035 –2036
  • DOI:  10.1049/el:19901313
  • Type: Article
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  • p. 2035 –2036 (2)
    A substantial reduction is reported in the threshold current densities for 1.5 μm wavelength InxGa1−xAs/ InxGa1−xAs1−xPy, strained-layer multiple quantum well (SLMQW) lasers over lattice-matched MQW lasers. Threshold current density was found to depend sensitively on the InAs content x and thickness d of the InxGa1−xAs quantum wells. Threshold current densities as low as 370 A/cm2 and internal quantum efficiency of 90% were obtained for separate confinement heterostructure SL-MQW lasers having four quantum wells and with x = 0.65 and d = 5 nm. Such a threshold current density is among the lowest values obtained thus far for 1.5 μm wavelength InGaAs/lnGaAsP MQW lasers. The present lasers were grown by chemical beam epitaxy.
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Noise reduction based on microphone array with LMS adaptive post-filtering
Femtosecond optical pulse generation using a distributed-feedback laser diode
  • Author(s): M. Nakazawa ; K. Suzuki ; E. Yamada
  • Source: Electronics Letters, Volume 26, Issue 24, p. 2038 –2040
  • DOI:  10.1049/el:19901315
  • Type: Article
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  • p. 2038 –2040 (3)
    Femtosecond optical pulses have been successfully generated for the first time using a distributed-feedback laser diode (DFB LD), erbium-doped optical fibre amplifiers, and the soliton narrowing effect in dispersion-shifted single-mode fibres. The DFB LD was gain-switched by a 500 MHz comb generator, and the pulse was converted into high power soliton pulses using a narrowband spectral windowing technique and the erbium amplifiers. With a three-stage soliton compression technique, 180–250 fs pulses with a peak power as high as 260 W were obtained. The average output power was 32mW.
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Efficient systolic string matching
  • Author(s): G.M. Megson
  • Source: Electronics Letters, Volume 26, Issue 24, p. 2040 –2042
  • DOI:  10.1049/el:19901316
  • Type: Article
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  • p. 2040 –2042 (3)
    Two new string matching heuristics are presented which reduce the hardware requirement and improve the computation speed of the systolic string matcher due to Lipton and Lopresti1 The new array requires A = m/2 + n/2 −1 basic cells, T = m/2 + n/2 −1 + max (m, n) steps to match strings of size n and m,respectively, and has efficiency e = 1 (100%). A measure of the heuristic effectiveness compared with the minimum edit distance is also given
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10 dB gain and high saturation power in a Nd3+-doped fluorozirconate fibre amplifier
Automated adaptive hysteresis current control technique for a voltage-fed PWM inverter
Companding current-mode integrator: A new circuit principle for continuous-time monolithic filters
High-efficiency AlGaAs/InGaAs heterostructure FET oscillators at V-band
Simple model for calculation of distortion in an optical analogue subcarrier multiplexed CATV system
Microstrip inversion transition
Line coding for very high speed LANs
Strong dependence of time resolution on detector diameter in single photon avalanche diodes
‘Fibre/radio’ for the provision of cordless/mobile telephony services in the access network
Erratum: Generalised theory of a non-TEM transmission line taper without discontinuities

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