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Online ISSN 1350-911X Print ISSN 0013-5194

Electronics Letters

Volume 29, Issue 23, 11 November 1993

Volumes & issues:

Volume 29, Issue 23

11 November 1993

Aperture fed rectangular and triangular dielectric resonators for use as magnetic dipole antennas
Height reduced superdirective array with helical directors
Novel ultrawide-bandwidth Vivaldi antenna with low crosspolarisation
  • Author(s): J.D.S. Langley ; P.S. Hall ; P. Newham
  • Source: Electronics Letters, Volume 29, Issue 23, p. 2004 –2005
  • DOI:  10.1049/el:19931336
  • Type: Article
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  • p. 2004 –2005 (2)
    The conventional Vivaldi antenna typically has a bandwidth of less than 3:1, limited by the feed line to radiating slot transition. The antipodal Vivaldi antenna removes this limitation but gives very high crosspolarisation which is undesirable for phased array applications. The Letter describes a new balanced antipodal Vivaldi antenna that retains the wide bandwidth characteristics while reducing the crosspolarisation by 15dB across an 18:1 band. Measurements are presented that compare the performance of existing antenna structures with this novel antenna element.
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Novel universal current-mode filter with single input and three outputs using only five current conveyors
  • Author(s): C.-M. Chang
  • Source: Electronics Letters, Volume 29, Issue 23, p. 2005 –2007
  • DOI:  10.1049/el:19931337
  • Type: Article
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  • p. 2005 –2007 (3)
    A new universal active current filter with single input and three outputs using only five current conveyors, two grounded capacitors and three grounded resistors is presented. The proposed circuit offers the following advantageous feature: universal current-mode filter realisation from the same configuration, no requirement for critical component matching conditions/cancellation constraints, orthogonal control of ωo, and Q through grounded resitors, and use of only two grounded capacitors which is ideal for IC implementation.
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Volterra kernel estimation for mildly nonlinear amplifiers
2-D discrete time lossless bounded real functions: minimal state space realisation
Enforcing positiveness on estimated spectral densities
  • Author(s): A. Stoica ; R. Moses ; P. Stoica
  • Source: Electronics Letters, Volume 29, Issue 23, p. 2009 –2011
  • DOI:  10.1049/el:19931340
  • Type: Article
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  • p. 2009 –2011 (3)
    Estimated spectral densities may often take on negative values in some frequency bands, and hence need be corrected to become positive for all frequencies. The Letter describes a most natural approach to enforcing the positiveness condition on an estimated spectral density, which is shown to lead to a semi-infinite optimisation problem. In the numerical example reported, the latter problem is solved by using the Matlab Optimization Toolbox.
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Family of binary sequences with useful correlation properties
Generating a fading process for the simulation of land-mobile radio communications
  • Author(s): D. Verdin  and  T.C. Tozer
  • Source: Electronics Letters, Volume 29, Issue 23, p. 2011 –2012
  • DOI:  10.1049/el:19931342
  • Type: Article
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  • p. 2011 –2012 (2)
    An appropriate design method for the correlation shaping filter used in the simulation of the narrowband land-mobile radio channel is shown to be that of a windowed-Bessel function. Thecoefficients are configured in a multirate filter, combining both the functions of noise shaping and image rejection, to allow the generation of a fading process with precise correlation properties with only moderate size convolutions at each iteration.
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Genetic approach to bearing estimation with sensor location uncertainties
Q2DPSK with new pulse shaping pair in the satellite mobile channel
  • Author(s): L. Wei
  • Source: Electronics Letters, Volume 29, Issue 23, p. 2014 –2015
  • DOI:  10.1049/el:19931344
  • Type: Article
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  • p. 2014 –2015 (2)
    A new pulse shaping pair [exp(jπt/T)uT(t), exp(–jπt/(T)uT(t)] for Q2PSK is proposed, where UT(t) is a rectangular pulse shaping function with symbol duration T. With this pulse shaping pair the performance of (Q2DPSK. is identical for both pulses and is less affected by the multipath time-delay (td) and the transmitter filter in the satellite mobile channel (SMC) than that with the sinusoidal pulse shaping pair [cos(πt/T)uT(t), sin(πt/T)uT(t)] of the original Q2DPSK.
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Evaluation of Booth encoding techniques for parallel multiplier implementation
  • Author(s): D. Villeger  and  V.G. Oklobdzija
  • Source: Electronics Letters, Volume 29, Issue 23, p. 2016 –2017
  • DOI:  10.1049/el:19931345
  • Type: Article
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  • p. 2016 –2017 (2)
    Although generally used in parallel multipliers, Booth encoding is shown to be obsolete due to the improvements in bit compression trees. It was found that a single row of 4:2 compressors reduces the number of partial products to one half, which is the essential function of the Booth encoding technique. With a single row of 4:2 compressors this reduction is achieved in less time and with fewer gates used.
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Application of the FDTD method and a full time-domain near-field transform to the problem of radiation from a PCB
Higher order formulation of absorbing boundary conditions for finite-difference time-domain method
Current-mode lowpass, bandpass and highpass biquads using two CCIIs
  • Author(s): C.-M. Chang
  • Source: Electronics Letters, Volume 29, Issue 23, p. 2020 –2021
  • DOI:  10.1049/el:19931348
  • Type: Article
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  • p. 2020 –2021 (2)
    Two current-mode second-order filter configurations which employ two second-generation current conveyors (CCIIs) and can realise lowpass and bandpass filter responses for one and highpass and bandpass filter responses for the other are presented. The proposed networks offer the following advantageous features: orthogonal control of ωo, and Q, use of only two grounded capacitors which make the networks ideal for integration, no requirement for critical matching condition/cancellation constraints, and low passive senitivities.
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Adaptive error duffusion method for image quantisation
  • Author(s): R.P. Mironov  and  R.K. Kunchev
  • Source: Electronics Letters, Volume 29, Issue 23, p. 2021 –2023
  • DOI:  10.1049/el:19931349
  • Type: Article
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  • p. 2021 –2023 (3)
    An adaptive error diffusion method for image quantisation is presented. The error filter coefficients are adapted using a generalised two-dimensional LMS algorithm and the quantisation scale is calculated on the basis of the image histogram. The developed method provides a minimum reconstruction error, a decrease in false countours in the homogeneous areas and precise reproduction of the edges in the output image.
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Dominant point matching algorithm
New optimal partial unit memory codes based on extended BCH codes
Blindness limitations in optical coherence domain reflectometry
Cascadable CMOS current gain cell with gain insensitive phase shift
New ECL gate in BiFET process
Wireless chip to chip interconnections for murtichip modules using leaky wave antennas
Comparison of optical waveguide losses in silicon-on-insulator
Phase-matched second-harmonic generation in χ(2)-inverted Langmuir-Blodgett waveguide structures
  • Author(s): M. Küpfer ; M. Flörsheimer ; Ch. Bosshard ; P. Günter
  • Source: Electronics Letters, Volume 29, Issue 23, p. 2033 –2034
  • DOI:  10.1049/el:19931357
  • Type: Article
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  • p. 2033 –2034 (2)
    Phase-matched second-harmonic generation by mode conversion in a new waveguide structure fabricated by the Langmuir-Blodgett (LB) technique is demonstrated. The nonlinear optically active part of the waveguide consists of two LB layers with opposite sign to the nonlinear optical coefficient d33. This configuration leads to a large improvement of the overlap integral as compared to conventional waveguides. In first experiments conversionefficiencies up to l%W1cm2have been obtained.
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All fibre, 1.5 μm widely tunable single frequency and narrow linewidth semiconductor ring laser with fibre Fabry-Perot filter
DFB and DBR lasers emitting at 980 nm
  • Author(s): D.T. Nichols ; J. Lopata ; W.S. Hobson ; P.F. Sciortino ; N.K. Dutta
  • Source: Electronics Letters, Volume 29, Issue 23, p. 2035 –2037
  • DOI:  10.1049/el:19931359
  • Type: Article
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  • p. 2035 –2037 (3)
    The performance of DFB and DBR ridge waveguide lasers operating at 980 nm is reported. The DBR devices used a single growth step and gave singlemode output powers as high as 30 mW. The DFB devices used a two-step growth process in which the lower cladding and active regions were grown first, the gratings were etched and then the upper cladding and p-contact layers were regrown on top of the grating. The DFB devices gave output powers as high as 75 mW.
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Equivalent circuit for vertical cavity top surface emitting lasers
High-speed photodetection characteristics of a Fabry-Perot laser amplifier under AM and FM formats
  • Author(s): T. Valkova ; M.J. Chawki ; M. le Ligne ; H. Dupont
  • Source: Electronics Letters, Volume 29, Issue 23, p. 2038 –2040
  • DOI:  10.1049/el:19931361
  • Type: Article
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  • p. 2038 –2040 (3)
    A comparison between the photodetection characteristics of an FP laser amplifier under AM and FM formats is reported. A 450 MHz photodetection bandwidth is obtained under the AM format using a Fabry-Perot laser amplifier, with two antireflection coated facets with 10−5 reflectivity. Using an FP laser amplifier with 10−3 reflectivity as an FM discriminator/photodetector, a photodetection bandwidth of up to 2.6 GHz was measured.
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Interferometric noise limitations in fibre-amplifier cascades
Low voltage, room temperature, ridge waveguide green-blue diode laser
  • Author(s): A Salokatve ; H. Jeon ; M. Hovinen ; P. Kelkar ; A.V. Nurmikko ; D.C. Grillo ; Li He ; J. Han ; Y. Fan ; M. Ringle ; R.L. Gunshor
  • Source: Electronics Letters, Volume 29, Issue 23, p. 2041 –2042
  • DOI:  10.1049/el:19931363
  • Type: Article
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  • p. 2041 –2042 (2)
    Ridge waveguide quantum well (QW) diode lasers in the green/blue region have been operated at voltages as low as 7 V in ZnCdSe/ZnSSe/ZnMgSSe pseudomorphic separate confinement heterostructures. These lasers include a p-Zn(Se, Te) graded gap ohmic contact layer to the top metal electrode. Without any attempt at heatsinking, and without reflective facet coatings, these devices have operated at pulsed duty cycles of 20% at room temperature, with average power output of several milliwatts.
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Reduction of harmonic distortion and noise in a semiconductor optical amplifier using bias current feedback
Simultaneous dual polarisation operation of a diode pumped femtosecond fibre laser
Temperature measurements of telecommunication lasers on a micrometre scale
  • Author(s): A.M. Mansanares ; D. Fournier ; A.C. Boccara
  • Source: Electronics Letters, Volume 29, Issue 23, p. 2045 –2047
  • DOI:  10.1049/el:19931366
  • Type: Article
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  • p. 2045 –2047 (3)
    Temperature maps of laser diode facets obtained by photothermal reflectance microscopy are presented. Biased double heterojunction InGaAsP lasers were investigated. The temperature images reveal the influence of laser mode on the spatial distribution of the heat dissipation in the device. Moreover, a study of the modulated reflectance as a function of the injection current is achieved.
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Wavelength conversion and switching of high speed data signals using semiconductor laser amplifiers
Nonlinear design of multiple-cavity switchable dielectric-resonator oscillators
  • Author(s): V. Rizzoli ; A. Costanzo ; C. Cecchetti
  • Source: Electronics Letters, Volume 29, Issue 23, p. 2048 –2050
  • DOI:  10.1049/el:19931368
  • Type: Article
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  • p. 2048 –2050 (3)
    The application of nonlinear CAD techniques to the design of multiple-cavity dielectric-resonator oscillators is demonstrated. The circuit topology consists of an FET oscillator which can be coupled to one of several dielectric resonators by means of a diode switching network. The circuit is numerically designed as a whole making use of a novel broadband optimisation technique especially devised for autonomous nonlinear circuits. At each fundamental frequency of interest the steady state of oscillation is determined by harmonic-balance analysis and at the same time the oscillator is tuned to the prescribed frequency by changing a parameter of the corresponding resonator. The electrical performance is simultaneously specified at all the fundamentals, and the optimisation is carried out with respect to the circuit parameters of the frequency-invariant part of the network.
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Power distributed amplifier based on interdigital combiners
Wideband transition form conductor-backed coplanar waveguide to modified coplanar stripline using multiple substrates
Equivalent circuits for microstrip gap discontinuities with metallisations of rectangular and trapezoidal cross sections
  • Author(s): J. Martel ; R.R. Boix ; M. Horno
  • Source: Electronics Letters, Volume 29, Issue 23, p. 2052 –2054
  • DOI:  10.1049/el:19931371
  • Type: Article
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  • p. 2052 –2054 (3)
    Microstrip gap discontinuities with finite thickness conducting strips of rectangular and trapezoidal cross-sections are analysed. The finite thickness strips are modelled as pairs of equipotential strips of negligible thickness placed at the top and bottom surfaces of the thick strips. The excess charge technique in the spectral domain is used to compute the quasistatic equivalent circuits of the analysed microstrip gap discontinuities.
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Crosstalk analysis in optically prefiltered subcarrier multiplexed systems
High-speed fibre optic links using 780 nm compact disc lasers
  • Author(s): W.H. Cheng  and  J.H. Bechtel
  • Source: Electronics Letters, Volume 29, Issue 23, p. 2055 –2057
  • DOI:  10.1049/el:19931373
  • Type: Article
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  • p. 2055 –2057 (3)
    High-speed fibre optic data links with transmission speeds of up to 2 Gbit/s and distances of up to 2 km for 50 and 62.5 μm core multimode fibres were demonstrated using low cost compact disc (CD) lasers and Si detectors operating at 780 nm. To the best of the authors′ knowledge, this is the highest data rate yet demonstrated for CD lasers operating at a wavelength of 780 nm. This suggests that a low cost CD laser with multimode fibre and its simple receptacle package design may be more usable for the short-range nature of gigabit fibre optic link applications than has previously been considered to be practical.
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High-speed regenerator section terminating LSIs
Optimal amplifier spacing in ultralong lightwave systems
Spurious-free dynamic range of linewidth-insensitive coherent AM analogue optical links
  • Author(s): T.K. Fong ; D.J.M. Sabido ; M. Tabara ; L.G. Kazovsky
  • Source: Electronics Letters, Volume 29, Issue 23, p. 2060 –2061
  • DOI:  10.1049/el:19931376
  • Type: Article
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  • p. 2060 –2061 (2)
    The Letter shows that externally-modulated coherent AM optical links are limited by the third-order nonlinearity of the electrooptical modulator (EOM) and the EOM nonlinearity reduces the dynamic range by 5–19 dB from the theoretical limit. When the received optical power is less than ̃1 mW, these links have a better dynamic range than conventional direct detection links.
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Suppression of interferometric noise in externally modulated lightwave AM-CATV systems by phase modulation
Elimination of ‘humps’ in methods for measuring the cutoff wavelength of single mode fibres
Domain inversion in LiTaO3 using an ion beam
Enhanced electroabsorption characteristics in δ-doped quantum well optical modulators
Monolithically integrated DBR lasers with simple tapered waveguide for low-loss fibre coupling
  • Author(s): K. Kasaya ; Y. Kondo ; M. Okamoto ; O. Mitomi ; M. Naganuma
  • Source: Electronics Letters, Volume 29, Issue 23, p. 2067 –2068
  • DOI:  10.1049/el:19931381
  • Type: Article
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  • p. 2067 –2068 (2)
    The Letter describes InGaAsP/InP 1.55 μm distributed Bragg reflector lasers monolithically integrated with a laterally tapered waveguide on the output facet. The tapered waveguide region of the devices has a thick partially clad p-InP layer grown by selective growth. The growth and fabrication processing steps were the same as those used to make conventional DBR laser diodes. The lasers demonstrate good lasing characteristics, lowloss coupling of less than 2.8 dB and +/− 2 μm misalignment tolerance with a flat-end singlemode fibre in both the lateral and vertical directions.
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Reliability characteristics of ohmic contacts for AlGaGs/GaAs HBTs
Triple-channel InP-based HEMT with highly nonlinear transconductance for nonlinear circuit applications
  • Author(s): R. Majidi-Ahy ; C. Nishimoto ; S. Bandy ; Y.C. Pao
  • Source: Electronics Letters, Volume 29, Issue 23, p. 2070 –2071
  • DOI:  10.1049/el:19931383
  • Type: Article
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  • p. 2070 –2071 (2)
    The Letter reports the development of a triple-channel HEMT with two undoped In0.53Ga0.47As layers and a spike-doped In0.52Al0.48As layer on InP, designed to have a strongly nonlinear transconductance. The effective electron velocity and the electron density in the InGaAs layers are higher than in the thick InAlAs layer, resulting in a highly nonlinear transconductance device with the potential for improved performance in nonlinear microwave circuit applications, as compared with conventional MESFETs and HEMTs.
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