Online ISSN
1350-911X
Print ISSN
0013-5194
Electronics Letters
Volume 29, Issue 23, 11 November 1993
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Volume 29, Issue 23
11 November 1993
Aperture fed rectangular and triangular dielectric resonators for use as magnetic dipole antennas
- Author(s): A. Ittipiboon ; M. Cuhaci ; R.K. Mongia ; P. Bhartia ; Y.M.M. Antar
- Source: Electronics Letters, Volume 29, Issue 23, p. 2001 –2002
- DOI: 10.1049/el:19931334
- Type: Article
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p.
2001
–2002
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The Letter reports the results of investigations on aperture-fed rectangular and triangular shaped dielectric resonators for use as magnetic-dipole antenna elements. Measured results show that both antennas have a large bandwidth (>10%) and their far field patterns are similar to that of a magnetic dipole.
Height reduced superdirective array with helical directors
- Author(s): G. Andrasic and J.R. James
- Source: Electronics Letters, Volume 29, Issue 23, p. 2002 –2004
- DOI: 10.1049/el:19931335
- Type: Article
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p.
2002
–2004
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A new end-fire helical superdirective array configuration is described that achieves both height and length reduction but does not need a corporate feed. Computations and measurements illustrate the sensitivity of the array directivity and efficiency to geometric changes for significant electrical size reductions. Possible applications and the use of superconducting elements are discussed.
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
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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.
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
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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.
Volterra kernel estimation for mildly nonlinear amplifiers
- Author(s): J.G. McRory and R. Johnston
- Source: Electronics Letters, Volume 29, Issue 23, p. 2007 –2008
- DOI: 10.1049/el:19931338
- Type: Article
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p.
2007
–2008
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The linear, third and fifth order Volterra kernels for two mildly nonlinear amplifiers have been estimated using common RF laboratory equipment. The estimation U made through a series of least square curve fits between measured data and nonlinear transfer functions. The estimation is validated through the comparison between measured and predicted IM3 distortion levels
2-D discrete time lossless bounded real functions: minimal state space realisation
- Author(s): G.E. Antoniou
- Source: Electronics Letters, Volume 29, Issue 23, p. 2008 –2009
- DOI: 10.1049/el:19931339
- Type: Article
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p.
2008
–2009
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A circuit realisation for two-dimensional (2-D) nth order discretetime lossless bounded real functions, with minimum number of delay elements, is presented. Based on this circuit realisation the corresponding matrix vectors A, b, c' of the Givone-Roesser 2-D state space model, are derived. The dimension of the 2-D state space model is minimal.
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.
Family of binary sequences with useful correlation properties
- Author(s): K. Byard
- Source: Electronics Letters, Volume 29, Issue 23, page: 2011 –2011
- DOI: 10.1049/el:19931341
- Type: Article
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2011
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A method for the synthesis of an infinite family of binary sequences with perfectly flat cross-correlation sidelobes is presented. The corresponding postprocessing arrays are similarly two-valued, and so the sequences may be particularly suited to applications in high noise environments.
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
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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.
Genetic approach to bearing estimation with sensor location uncertainties
- Author(s): J.S. Hong
- Source: Electronics Letters, Volume 29, Issue 23, p. 2013 –2014
- DOI: 10.1049/el:19931343
- Type: Article
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p.
2013
–2014
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A genetic approach which combines a genetic optimisation algorithm with an adaptive weighting function has been developed to estimate the bearing or direction of arrival (DOA) of multiple sources in the presence of sensor location uncertainties. Computer simulations show the good performance of the proposed approach.
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
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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.
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
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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.
Application of the FDTD method and a full time-domain near-field transform to the problem of radiation from a PCB
- Author(s): I.J. Craddock and C.J. Railton
- Source: Electronics Letters, Volume 29, Issue 23, p. 2017 –2018
- DOI: 10.1049/el:19931346
- Type: Article
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p.
2017
–2018
(2)
The finite-difference time-domain method is combined with a full tinie-domain near-field transform to yield accurately and efficiently the radiated field levels measured at a distance of 3m from a printed circuit board.
Higher order formulation of absorbing boundary conditions for finite-difference time-domain method
- Author(s): P.Y. Wang ; S. Kozaki ; M. Ohki ; T. Yabe
- Source: Electronics Letters, Volume 29, Issue 23, p. 2018 –2020
- DOI: 10.1049/el:19931347
- Type: Article
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p.
2018
–2020
(3)
A simple formulation of absorbing boundary conditions with higher order approximation is proposed for the finite-difference time-domain (FD-TD) method. Although this formulation is based on the third order approximation of the one-way wave equations, the authors have succeeded in reducing it to an equation in a form quite similar to the second order approximation.
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.
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.
Dominant point matching algorithm
- Author(s): P.C. Yuen
- Source: Electronics Letters, Volume 29, Issue 23, p. 2023 –2024
- DOI: 10.1049/el:19931350
- Type: Article
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p.
2023
–2024
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A novel dominant point matching algorithm is designed and developed for occluded object recognition. The developed algorithm is capable of grouping all scattered dominant points on an object boundary, due to occlusion, into a single representation for recognition. A set of handtools is selected to evaluate the performance of the algorithm and the results are encouraging.
New optimal partial unit memory codes based on extended BCH codes
- Author(s): U. Dettmar and U.K. Sorger
- Source: Electronics Letters, Volume 29, Issue 23, p. 2024 –2025
- DOI: 10.1049/el:19931351
- Type: Article
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p.
2024
–2025
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Some new optimal binary partial unit memory codes are presented. The codes are constructed from extended BCH codes. A general method for constructing PUM codes based on extended RS and BCH codes is described.
Blindness limitations in optical coherence domain reflectometry
- Author(s): S.R. Chinn and E.A. Swanson
- Source: Electronics Letters, Volume 29, Issue 23, p. 2025 –2027
- DOI: 10.1049/el:19931352
- Type: Article
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2025
–2027
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The theoretical and measured limitations on dynamic range near strong reflections in optical coherence domain reflectometry arc examined. A model and data are presented that show that such blindness limitations can be caused by broad spectral tails from the superluminescent diodes typically used in such measurements.
Cascadable CMOS current gain cell with gain insensitive phase shift
- Author(s): E.A.M. Klumperink
- Source: Electronics Letters, Volume 29, Issue 23, p. 2027 –2028
- DOI: 10.1049/el:19931353
- Type: Article
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p.
2027
–2028
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It is shown that by using a complementary circuit topology, electronically variable gain in combination with a gain insensitive phase shift can be achieved. A cascadable CMOS current gain cell based on this concept is proposed, together with a linearisation technique for this circuit
New ECL gate in BiFET process
- Author(s): V.G. Oklobdzija
- Source: Electronics Letters, Volume 29, Issue 23, p. 2029 –2030
- DOI: 10.1049/el:19931354
- Type: Article
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p.
2029
–2030
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An ECL gate implemented as a combination of bipolar and MOS circuits in a BiFET process is presented. The resulting ECL gate exhibits an improved speed-power product over circuits presented in the past. Owing to its reduced power consumption this gate allows a higher level of integration for ECL. The process used is standard BiCMOS.
Wireless chip to chip interconnections for murtichip modules using leaky wave antennas
- Author(s): M.K. Iyer ; R.D. Seager ; J.C. Vardaxoglou
- Source: Electronics Letters, Volume 29, Issue 23, p. 2030 –2031
- DOI: 10.1049/el:19931355
- Type: Article
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p.
2030
–2031
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A novel interchip communication technique for very high speed multichip modules is presented. The feasibility of using a dielectric guide leaky wave antenna integrated on a chip for transmission and reception is discussed. J-band measurements and predictions based on a model developed using the transmission line matrix (TLM) method are compared
Comparison of optical waveguide losses in silicon-on-insulator
- Author(s): T. Zinke ; U. Fischer ; A. Splett ; B. Schüppert ; K. Petermann
- Source: Electronics Letters, Volume 29, Issue 23, p. 2031 –2033
- DOI: 10.1049/el:19931356
- Type: Article
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p.
2031
–2033
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Waveguide losses in SOI (silicon-on-insulator) material fabricated by different techniques are compared thus enabling us to confirm the theoretical dependence of losses on layer thickness. Singlemode waveguide losses in BE-SOI (bond and etchback-SOI) below 0.5dB/cm are reported for waveguides with cross-sections of several square micrometres.
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
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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.
All fibre, 1.5 μm widely tunable single frequency and narrow linewidth semiconductor ring laser with fibre Fabry-Perot filter
- Author(s): M.J. Chawki ; I. Valiente ; R. Auffret ; V. Tholey
- Source: Electronics Letters, Volume 29, Issue 23, p. 2034 –2035
- DOI: 10.1049/el:19931358
- Type: Article
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p.
2034
–2035
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An all fibre, widely tunable, single frequency, semiconductor ring laser was constructed with a narrow linewidth of 35 kHz. Tuning over 50 nm was electronically obtained using a fibre Fabry-Perot filter as a selected wavelength element. Single-frequency operation was demonstrated with sidemode suppression higher than 35 dB.
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
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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.
Equivalent circuit for vertical cavity top surface emitting lasers
- Author(s): P.R. Brusenbach ; S. Swirhun ; T.K. Uchida ; M. Kim ; C. Parsons
- Source: Electronics Letters, Volume 29, Issue 23, p. 2037 –2038
- DOI: 10.1049/el:19931360
- Type: Article
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p.
2037
–2038
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A small signal equivalent circuit for VCSELs is developed which provides an excellent fit to measured S-parameter data. Equivalent circuits were obtained for 6 μm diameter, 780 nm, gain guided VCSELs with 14 GHz modulation bandwidth, the highest yet reported.
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
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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.
Interferometric noise limitations in fibre-amplifier cascades
- Author(s): L. Eskildsen ; E.L. Goldstein ; M. Andrejco ; L. Curtis ; V. Shah ; D. Mahoney ; C.E. Zah ; C. Lin
- Source: Electronics Letters, Volume 29, Issue 23, p. 2040 –2041
- DOI: 10.1049/el:19931362
- Type: Article
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p.
2040
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Phase-induced intensity noise from weak multiple reflectors is evaluated theoretically and experimentally in amplifier cascades without isolators. Rayleigh backscattering alone significantly limits the number of amplifiers in the span. Theory and experiment agree closely for a six-amplifier cascade.
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
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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.
Reduction of harmonic distortion and noise in a semiconductor optical amplifier using bias current feedback
- Author(s): J.A. Constable ; I.H. White ; A.N. Coles ; D.G. Cunningham
- Source: Electronics Letters, Volume 29, Issue 23, p. 2042 –2044
- DOI: 10.1049/el:19931364
- Type: Article
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2042
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The application of bias current feedback to a semiconductor optical amplifier is shown to improve considerably its noise and distortion performance in analogue applications. Improvements in harmonic distortion of up to 12.75 dB, and in noise levels of up to 7.5 dB, have been achieved.
Simultaneous dual polarisation operation of a diode pumped femtosecond fibre laser
- Author(s): M.J. Guy and J.R. Taylor
- Source: Electronics Letters, Volume 29, Issue 23, p. 2044 –2045
- DOI: 10.1049/el:19931365
- Type: Article
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2044
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The behaviour of a diode pumped figure-of-eight ytterbium/erbium-doped fibre laser which generates subpicosecond pulses is described. This laser is observed to mode-lock simultaneously in two orthogonal polarisation states with distinct temporal and spectral characteristics.
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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2045
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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.
Wavelength conversion and switching of high speed data signals using semiconductor laser amplifiers
- Author(s): R. Schnabel ; W. Pieper ; A. Ehrhardt ; M. Eiselt ; H.G. Weber
- Source: Electronics Letters, Volume 29, Issue 23, p. 2047 –2048
- DOI: 10.1049/el:19931367
- Type: Article
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2047
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Nonlinear gain dynamics in semiconductor laser amplifiers enables ultrafast signal processing. Wavelength conversion of up to 18 Gbit/s data signals is demonstrated. The switching characteristics are applied to the operation of an AND gate for 30 ps pulses.
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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2048
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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.
Power distributed amplifier based on interdigital combiners
- Author(s): S. D'Agostino and C. Paoloni
- Source: Electronics Letters, Volume 29, Issue 23, p. 2050 –2051
- DOI: 10.1049/el:19931369
- Type: Article
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2050
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An innovative power distributed amplifier topology to improve the small signal gain and the power added efficiency is presented. The introduction of Lange couplers at the input and output ports of the amplifier leads to a remarkable advantage in comparison with the conventional configuration. An example is discussed to confirm the validity and the effectiveness of the proposed circuit.
Wideband transition form conductor-backed coplanar waveguide to modified coplanar stripline using multiple substrates
- Author(s): K. Tilley ; X.-D. Wu ; K. Chang
- Source: Electronics Letters, Volume 29, Issue 23, p. 2051 –2052
- DOI: 10.1049/el:19931370
- Type: Article
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p.
2051
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The Letter presents a wideband and low-loss transition from conductor-backed coplanar waveguide to a modified, conductor-backed coplanar strip transmission line. The measured insertion loss is less than 1 dB up to 4.8 GHz and the return loss is greater than 12 dB. To reduce undesired modes two dielectric layers are used between the circuit and the conductor backing.
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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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.
Crosstalk analysis in optically prefiltered subcarrier multiplexed systems
- Author(s): J. Marti ; J. Capmany ; H. Mangharam
- Source: Electronics Letters, Volume 29, Issue 23, p. 2054 –2055
- DOI: 10.1049/el:19931372
- Type: Article
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p.
2054
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Theoretical modelling of optical prefiltering, taking into account the coherence function of the optical source and crosstalk degradation in intensity modulation/direct detection subcarrier multiplexing systems, is studied.
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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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.
High-speed regenerator section terminating LSIs
- Author(s): Y. Yamabayashi ; Y. Sato ; S. Matsuoka ; K. Hohkawa
- Source: Electronics Letters, Volume 29, Issue 23, p. 2057 –2058
- DOI: 10.1049/el:19931374
- Type: Article
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The Letter reports the first four-chip set for the STM-64 regenerator-section terminator, a key component of the next generation SDH transmission system. The Si-bipolar gate-array LSIs are fabricated and tested to confirm operation at 1.244 Gbit / s. This result makes it feasible to construct the line terminators needed.
Optimal amplifier spacing in ultralong lightwave systems
- Author(s): E. Lichtman
- Source: Electronics Letters, Volume 29, Issue 23, p. 2058 –2060
- DOI: 10.1049/el:19931375
- Type: Article
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The optimal amplifier spacing required for the best system performance is calculated. The analysis considers the effect of amplified spontaneous emission noise, post-amplifier loss, and polarisation dependent gain on the optimal spacing. The optimal spacing was found to be a few tens of kilometres depending on the specific system.
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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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.
Suppression of interferometric noise in externally modulated lightwave AM-CATV systems by phase modulation
- Author(s): F.W. Willems and W. Muys
- Source: Electronics Letters, Volume 29, Issue 23, p. 2062 –2063
- DOI: 10.1049/el:19931377
- Type: Article
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Multiple discrete reflections and Rayleigh scattering in a fibre network cause interterometric intensity noise, which degrades the carrier to noise ratio in AM-CATV systems, depending on the laser linewidth and length of the fibre section. This noise can be suppressed by up to 10 dB if single tone phase modulation of the optical signal is applied.
Elimination of ‘humps’ in methods for measuring the cutoff wavelength of single mode fibres
- Author(s): F Wilczewski and F. Krahn
- Source: Electronics Letters, Volume 29, Issue 23, p. 2063 –2064
- DOI: 10.1049/el:19931378
- Type: Article
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The measurement of the cutoff wavelength in singlemode fibres is strongly affected by‘humps’. The Letter shows that the humps can be eliminated totally by replacing the higher-index primary coating by an oil, whose refractive index is matched exactly by controlling its temperature.
Domain inversion in LiTaO3 using an ion beam
- Author(s): K. Mizuuchi and K. Yamamoto
- Source: Electronics Letters, Volume 29, Issue 23, p. 2064 –2066
- DOI: 10.1049/el:19931379
- Type: Article
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The fabrication of domain inversion in LiTaO3 at room temperature by injecting Si2+ ion into the +c face is presented. A first-order periodic domain inversion with 50% duty cycle and depth of 0.3mm was realised. Using this structure, 22.8 μW of blue light was generated for a conversion efficiency of 20%/Wcm2.
Enhanced electroabsorption characteristics in δ-doped quantum well optical modulators
- Author(s): W. Batty and D.W.E. Allsopp
- Source: Electronics Letters, Volume 29, Issue 23, p. 2066 –2067
- DOI: 10.1049/el:19931380
- Type: Article
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It is shown by device simulation that quantum well shaping by strategic δ-doping provides a new and flexible means of producing enhanced electroabsorption characteristics in normal transmission, asymmetric Fabry-Perot and waveguide optical modulators based on the quantum confined Stark effect.
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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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.
Reliability characteristics of ohmic contacts for AlGaGs/GaAs HBTs
- Author(s): T. Nozu ; N. Iizuka ; Y. Kuriyama ; S. Hongo
- Source: Electronics Letters, Volume 29, Issue 23, p. 2069 –2070
- DOI: 10.1049/el:19931382
- Type: Article
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The thermal stability of ohmic contacts for AlGaAs/GaAs HBTs is presented. Ti/Pt/Au, Ti/Pt/Au and Cr/Pt/Au, and AuGe/Ni/Ti/Pt/Au were investigated for emitter, base, and collector contacts, respectively. As a result of 200°C storage tests, it was found that these contacts did not limit the reliability of AlGaAs/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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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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