Online ISSN
1350-911X
Print ISSN
0013-5194
Electronics Letters
Volume 22, Issue 20, 25 September 1986
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Volume 22, Issue 20
25 September 1986
Security of Okamoto public-key cryptosystem
- Author(s): K. Koyama
- Source: Electronics Letters, Volume 22, Issue 20, p. 1033 –1034
- DOI: 10.1049/el:19860708
- Type: Article
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The security of the Okamoto public-key cryptosystem is analysed. If some secret keys of this system are chosen inadequately, the known-plaintext attack is applicable to obtain all secret keys. To prevent the proposed cryptanalysis, the necessary condition for the secret keys is shown.
Transmission loss characteristics of fluoride glass single-mode fibre
- Author(s): Y. Ohishi ; S. Sakaguchi ; S. Takahashi
- Source: Electronics Letters, Volume 22, Issue 20, p. 1034 –1035
- DOI: 10.1049/el:19860709
- Type: Article
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The transmission loss spectrum of a fluoride glass single-mode fibre as obtained with a new preform fabrication technique is shown. It is clearly confirmed on the loss spectrum that the obtained fibre is a single-mode waveguide in the minimum loss wavelength range (2–4 μm). The minimum loss of this fibre is 8.5 dB/km at 2.2 μm and the OH excess loss is 15dB/km at 2.85 μm. This fabrication technique is effective in eliminating OH contamination.
Method for traffic and blocking estimation from test-calling measurements
- Author(s): M. Koukias and G. Kokkinakis
- Source: Electronics Letters, Volume 22, Issue 20, p. 1035 –1037
- DOI: 10.1049/el:19860710
- Type: Article
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A method for the estimation of real traffic offered to a trunk from the congestion loss measured with a test-call generator is described. The method consists in simulating both kinds of traffic (real and artificial) and in extracting a relation between the above quantities. Simulations were made for several offered traffic models and test calling rates and led to the construction of tables and diagrams for practical use.
Flicker noise in GaAs MESFET X-band amplifiers in the temperature range 300 K to 2 K
- Author(s): L.D. Mann ; D.G. Blair ; K.J. Wellington
- Source: Electronics Letters, Volume 22, Issue 20, p. 1037 –1038
- DOI: 10.1049/el:19860711
- Type: Article
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We report measurements of the noise temperature of small-signal, low-noise X-band GaAs MESFET amplifiers from room temperature down to 2 K, at offset frequencies of several hundred hertz from the carrier and for input carrier powers from -40 to -20dBm. We observe a dramatic increase in the level of flicker noise as these devices are cooled to liquid helium temperatures, in marked contrast to the normally observed decrease in noise temperature of an unsaturated GaAs MESFET amplifier as it is cooled.
Two-dimensional index distribution determination from near-field measurements in single-mode fibres
- Author(s): G. Coppa ; P. di Vita ; M. Potenza
- Source: Electronics Letters, Volume 22, Issue 20, p. 1038 –1040
- DOI: 10.1049/el:19860712
- Type: Article
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The refractive-index distribution of single-mode optical fibres can be obtained from transmitted near-field intensity measurements. The generalisation of the method from conventional fibres to noncircularly symmetric guides (e.g. polarisation-maintaining fibres) is discussed. Results obtained both on circular and on polarisation-maintaining fibres are presented.
Dichroic dual-band microstrip array
- Author(s): J.R. James and G. Andrasic
- Source: Electronics Letters, Volume 22, Issue 20, p. 1040 –1042
- DOI: 10.1049/el:19860713
- Type: Article
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It is demonstrated that two microstrip arrays can be superimposed in a common planar aperture to create a dual-band array. The concept relies critically on the invisibility of the uppermost array, which is constructed from a frequency-selective conducting surface (FSCS). Analysis and measurements establish the degree of invisibility obtainable in an FSCS of finite extent and indicate the likely behaviour in a composite system. Measurements for a dual-band array illustrate the findings and good future prospects for the concept, but also show that feeder line radiation, if not reduced, can constrain sidelobe levels.
Antenna power pattern synthesis using method of successive projections
- Author(s): G.T. Poulton
- Source: Electronics Letters, Volume 22, Issue 20, p. 1042 –1043
- DOI: 10.1049/el:19860714
- Type: Article
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A general technique for the synthesis of antenna power patterns is presented which does not require the calculation of derivatives. Based on the method of successive projections, it leads to a fast and simple algorithm. An example is presented for a satellite antenna giving hemispheric coverage from a directly radiating horn array.
Power penalty due to decision-time jitter in receivers using avalanche photodiodes
- Author(s): T.M. Shen
- Source: Electronics Letters, Volume 22, Issue 20, p. 1043 –1045
- DOI: 10.1049/el:19860715
- Type: Article
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Power penalties on receiver sensitivity due to the presence of timing jitter are derived for receivers incorporated with PIN detectors and with avalanche photodiodes. It is shown that the presence of timing jitter will lower the optical gain of the avalanche photodiodes and will reduce the improvement in receiver sensitivity of using avalanche photodiodes over PIN detectors. Using computer simulation on results of transmission experiments it is shown that the receiver sensitivity can be degraded by several decibels owing to the presence of timing jitter in the Anritsu pulse pattern generator and/or error detector.
Compact bulk optical isolator with monomode fibre pigtails for use at 1.3 μm
- Author(s): A.E. Green and G. Georgiou
- Source: Electronics Letters, Volume 22, Issue 20, p. 1045 –1046
- DOI: 10.1049/el:19860716
- Type: Article
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A compact optical isolator has been designed, with monomode optical fibre pigtails, for use at a wavelength of 1.3 μm. The device has an isolation of greater than 26 dB and a fibre-to-fibre insertion loss of 3.5 dB, and the return loss is better than 26 dB.
Complexity and autocorrelation properties of a class of de Bruijn sequences
- Author(s): M. Beale and S.M.S. Lau
- Source: Electronics Letters, Volume 22, Issue 20, p. 1046 –1047
- DOI: 10.1049/el:19860717
- Type: Article
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The complexity and autocorrelation properties of de Bruijn sequences generated by an algorithm of Etzion and Lempel are investigated. While the autocorrelation results deviate from the behaviour expected for truly random sequences, the complexity distributions are very encouraging. Specifically, the minimum complexities are significantly greater than those of other de Bruijn sequences.
Design of DFB lasers for high-power single-mode operation
- Author(s): H. Soda ; H. Ishikawa ; H. Imai
- Source: Electronics Letters, Volume 22, Issue 20, p. 1047 –1049
- DOI: 10.1049/el:19860718
- Type: Article
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The longitudinal-mode behaviour above threshold for DFB lasers has been analysed taking into account spatial hole burning along the laser axis. As a result, the single-longitudinal-mode operating condition up to high optical output power has been made clear.
Solution to some electromagnetic problems using fast Fourier transform with conjugate gradient method
- Author(s): M.F. Cátedra
- Source: Electronics Letters, Volume 22, Issue 20, p. 1049 –1051
- DOI: 10.1049/el:19860719
- Type: Article
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Using the fast Fourier transform (FFT) to compute the convolution integrals that appear in the conjugate-gradient method (CGM), an efficient numerical procedure to solve electromagnetic problems is obtained. In comparison with the method of moments (MM), the proposed FFT-CGM avoids the storage of large matrices and reduces the computer time by orders of magnitude.
Dispersion-determined limits on production tolerances of single-mode fibres
- Author(s): S.B. Andreasen
- Source: Electronics Letters, Volume 22, Issue 20, p. 1051 –1052
- DOI: 10.1049/el:19860720
- Type: Article
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For single-mode fibres the standard deviation of dispersion at the nominal zero-dispersion wavelength depends strongly on the dispersion slope. For dispersion-shifted fibres, optimum values of the slope as a function of production tolerances on core radius and index difference are found, and for dispersion-flattened fibres maximum allowable production tolerances are given.
Measurement of direct frequency modulation characteristics of DFB-LD by delayed self-homodyne technique
- Author(s): S. Ryu and S. Yamamoto
- Source: Electronics Letters, Volume 22, Issue 20, p. 1052 –1054
- DOI: 10.1049/el:19860721
- Type: Article
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The direct frequency modulation characteristics of a DFB-LD can be simply measured by means of a delayed selfhomodyne method using a single-mode fibre delay line and a single-mode fibre coupler. This measuring method has the features of simple set-up and high resolution when narrow-linewidth optical sources are used, compared to the conventional interferometric methods. Direct frequency modulation characteristics of a DFB-LD in the 1.55 μm region are measured, and the results obtained agree well with those by a Fabry-Perot interferometer.
Planim: a new concept in the design of MIC filters
- Author(s): M. Salerno and R. Sorrentino
- Source: Electronics Letters, Volume 22, Issue 20, p. 1054 –1056
- DOI: 10.1049/el:19860722
- Type: Article
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The planar circuit approach for the characterisation of microstrip circuits is combined with the image parameter method to give a new powerful technique for integrated circuit filter design (planim). The inclusion of two-dimensional effects in the synthesis procedure makes the planim approach particularly suited for monolithic microwave circuits. The design of microstrip filters with extremely wide stopbands is shown as an example.
MOS SC microsystem for generating trigonometrical functions and their inverses
- Author(s): A. Cichocki and R. Unbehauen
- Source: Electronics Letters, Volume 22, Issue 20, p. 1056 –1057
- DOI: 10.1049/el:19860723
- Type: Article
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A new switched-capacitor (SC) circuit arrangement is proposed for the simultaneous generation of trigonometrical functions (sin x, cos x, tan x) and their inverses (sin-1x, cos-1x, tan-1x) in analogue form, where x(t) is the input voltage. The method is based on the sample-and-hold and time-division principles. The system possesses some attractive features, e.g. simplicity and low cost, and can be easily implemented in monolithic (IC) form using MOS technology. The performance of the system is illustrated by experimental results.
High-performance millimetre-wave suspended stripline Gunn VCO
- Author(s): R.S. Tahim ; G.M. Hayashibara ; K. Chang
- Source: Electronics Letters, Volume 22, Issue 20, p. 1057 –1059
- DOI: 10.1049/el:19860724
- Type: Article
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A novel millimetre-wave integrated circuit Gunn voltagecontrolled oscillator (VCO) has been developed with high output power using suspended stripline. An output power of 100 to 150mW has been achieved at frequencies between 33 and 42 GHz. A varactor diode was mounted in alignment and in close proximity to the Gunn diode to achieve an electronic tuning range of 300 MHz
Feed design for a two-dimensional bootlace lens
- Author(s): H.P. Coleman and B.D. Wright
- Source: Electronics Letters, Volume 22, Issue 20, p. 1059 –1060
- DOI: 10.1049/el:19860725
- Type: Article
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A coaxial probe assembly for use as a feed for two-dimensional bootlace lenses is described. Experimental results are presented with parasitic elements used to improve the impedance match.
Coherent phase-locked synchronous oscillator
- Author(s): V. Uzunoglu
- Source: Electronics Letters, Volume 22, Issue 20, p. 1060 –1061
- DOI: 10.1049/el:19860726
- Type: Article
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A coherent phase-locked synchronous oscillator (CPSO) is a coherent synchronisation and tracking network developed using a synchronous oscillator and a feedback network, external to the synchronous oscillator (SO). It is a unique network whose noise bandwidth is fully independent of its tracking range and has absolute coherency throughout the tracking range. It has several orders of magnitude wider tracking range for a given input signal/noise ratio than any other tracking network.
Method to reduce the sign bit extension in a multiplier that uses the modified Booth algorithm
- Author(s): M. Roorda
- Source: Electronics Letters, Volume 22, Issue 20, p. 1061 –1062
- DOI: 10.1049/el:19860727
- Type: Article
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A technique that reduces the number of full adders that are used to implement the modified Booth algorithm is described. This technique is based on the need to extend the sign bit of the partial products and on the redundancy that is implicit in this operation.
Mechanism of carrier lifetime increase in ion beam synthesised SOI structures
- Author(s): W. Skorupa ; H. Oertel ; H. Bartsch
- Source: Electronics Letters, Volume 22, Issue 20, p. 1062 –1064
- DOI: 10.1049/el:19860728
- Type: Article
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Carrier lifetimes were measured in epitaxial silicon layers which were deposited on silicon wafers implanted with different nitrogen doses at 330 keV. At doses greater than 1016 cm-2 the lifetime was more than one order of magnitude higher on the implanted part of the wafers (∼300μs). The mechanism responsible for this effect is connected with the gettering efficiency for heavy metals of a precipitation-rich dislocation network in the implanted silicon.
Compact broadband microstrip antenna
- Author(s): C.K. Aanandan and K.G. Nair
- Source: Electronics Letters, Volume 22, Issue 20, p. 1064 –1065
- DOI: 10.1049/el:19860729
- Type: Article
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The development of a compact broadband microstrip antenna configuration is presented. The system uses a number of parasitic elements which are gas-coupled to a driven patch. The enhancement of bandwidth does not cause deterioration of the radiation pattern of the system.
Nondispersive delay line at microwave frequency by magnetostatic forward volume waves
- Author(s): P. de Gasperis ; G. Miccoli ; C. di Gregorio
- Source: Electronics Letters, Volume 22, Issue 20, p. 1065 –1066
- DOI: 10.1049/el:19860730
- Type: Article
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The letter describes how a magnetostatic constant delay line can be designed and practically realised by using two identical dispersive delay lines operating with forward volume waves and frequency-inverting one of the band responses.
Optical waveguides in In0.52Al0.48As grown on InP by MBE
- Author(s): S. Ritchie ; E.G. Scott ; P.M. Rodgers
- Source: Electronics Letters, Volume 22, Issue 20, p. 1066 –1068
- DOI: 10.1049/el:19860731
- Type: Article
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Planar and rib optical waveguides have been made in In0.52Al0.48As grown on InP substrates by molecular beam epitaxy. The evidence that In0.52Al0.48As has a higher refractive index than InP is at variance with the values obtained from existing theoretical models.
Direct electro-optic sampling of a GaAs integrated circuit using a gain-switched InGaAsP injection laser
- Author(s): A.J. Taylor ; R.S. Tucker ; J.M. Wiesenfeld ; C.A. Burrus ; G. Eisenstein ; J.R. Talman ; S.S. Pei
- Source: Electronics Letters, Volume 22, Issue 20, p. 1068 –1069
- DOI: 10.1049/el:19860732
- Type: Article
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We demonstrate an electro-optic sampling system based on a gain-switched InGaAsP injection laser. The system has a temporal resolution of 18ps and is used for noninvasive probing of waveform internal to a GaAs monolithic integrated circuit operating at 2.4GHz.
Simple formula for estimation of minimum clock-feedthrough error voltage
- Author(s): G.C. Temes
- Source: Electronics Letters, Volume 22, Issue 20, p. 1069 –1070
- DOI: 10.1049/el:19860733
- Type: Article
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A simple approximating formula is derived for the prediction of clock-feedthrough noise in a switched-capacitor (SC) integrator. It can be used for estimating the achievable accuracy and dynamic range of SC circuits.
Novel trial field of single-mode graded-index fibres usable for non-Gaussian field distributions
- Author(s): K. Hayata ; M. Koshiba ; M. Suzuki
- Source: Electronics Letters, Volume 22, Issue 20, p. 1070 –1072
- DOI: 10.1049/el:19860734
- Type: Article
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A novel trial field for the variational analysis of the fundamental mode of graded-index optical fibres is proposed, which is usable for non-Gaussian field distributions and is compatible with our physical intuition. A comparison is made with results obtained using the conventional Gaussian trial field and those of a rigorous numerical method. As a result, the present method can yield satisfactorily accurate results even in the region where the conventional method fails to be applied, without involving much computational effort.
Calculation of bit error rate in ASK heterodyne systems with envelope detection influenced by laser phase noise
- Author(s): J. Franz and U. Helnerus
- Source: Electronics Letters, Volume 22, Issue 20, p. 1072 –1074
- DOI: 10.1049/el:19860735
- Type: Article
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The bit error rate (BER) is calculated as a function of the laser phase noise, the intermediate filter bandwidth and the bit rate. The calculation is based on the derived probability density function (PDF) of the detected envelope signal. The evaluation of the BER gives a direct criterion for the permissible laser linewidth.
Random test length with and without replacement
- Author(s): W.H. Debany ; P.K. Varshney ; C.R.P. Hartmann
- Source: Electronics Letters, Volume 22, Issue 20, p. 1074 –1075
- DOI: 10.1049/el:19860736
- Type: Article
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We compare the effectiveness of two methods of random test generation: with and without replacement of test patterns. Expressions for test length and test confidence for both methods are given. Determination of random test length is simpler when tests are generated with replacement, yet most practical random test methods produce tests without replacement. The conditions are obtained such that testing without replacement can be approximated using the simpler approach.
Ultrahigh-strength fibre splices by modified H2/O2 flame fusion
- Author(s): J.T. Krause
- Source: Electronics Letters, Volume 22, Issue 20, p. 1075 –1077
- DOI: 10.1049/el:19860737
- Type: Article
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Although original fibre strength can be retained in fibre splices by fusing with an H2/O2 flame incorporating Cl2, there are often circumstances where the use of Cl2 is not always convenient or possible. The present effort to optimise splice strengths in the absence of Cl2 has resulted in average splice strengths of ∼690 ksi (∼4.8 GPa), values double those by conventional flame fusion or are fusion methods. This is of major advantage for all fusion splicing applications requiring high strength and long-term reliability.
Adaptive correlation diversity for a CD900-like system in an urban mobile radio environment
- Author(s): W.H. Lam and R. Steele
- Source: Electronics Letters, Volume 22, Issue 20, p. 1077 –1078
- DOI: 10.1049/el:19860738
- Type: Article
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A CD900-like system using Gold codes and nonadaptive diversity yielded asymptotic average probability of symbol error Pa of 6 × 10-3, 6 × 10-4, 10-3 and 9 × 10-3, for diversity order 1, 2, 3 and 5, respectively. An adaptive diversity scheme reduced Pa to 6 × 10-5. Walsh codes had a minimum Pa of 4 × 10-2.
Impact of coherence length on the amplitude variations of the delay power profile in a mobile environment
- Author(s): J. van Rees
- Source: Electronics Letters, Volume 22, Issue 20, p. 1078 –1079
- DOI: 10.1049/el:19860739
- Type: Article
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The impact of coherence length on the amplitude variations of the delay power profile has been determined by computer simulation using a Rayleigh fading model for each delay bin. The results can be used for choosing the coherence length, over which the transfer function of the radio channel is considered time-invariant, for different wideband mobile radio systems.
Linear imaging in scanning polarisation/interference contrast microscopy
- Author(s): C.W. See and M. Vaez Iravani
- Source: Electronics Letters, Volume 22, Issue 20, p. 1079 –1081
- DOI: 10.1049/el:19860740
- Type: Article
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The theory and design of a linear polarisation/interference contrast microscope are described. The operation of the technique is based on the use of a sinusoidally driven electro-optic phase modulator. The expected sensitivity of the system in detecting phase variations is 5 × 10-7 rad, in a 10Hz bandwidth. Experimental results are presented on the imaging of magnetic domains, which clearly demonstrate the sensitivity superiority of linear operation.
High-power ridge-waveguide AlGaAs GRIN-SCH laser diode
- Author(s): C. Harder ; P. Buchmann ; H. Meier
- Source: Electronics Letters, Volume 22, Issue 20, p. 1081 –1082
- DOI: 10.1049/el:19860741
- Type: Article
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AlGaAs ridge single-quantum-well graded-index separate confinement heterostructure (SQW GRIN-SCH) lasers with typical threshold currents of 9 mA and differential quantum efficiencies between 80% and 85% for 0.4 mm-long cavities have been fabricated with molecular beam epitaxy. Continuous-wave light output increases linearly with the drive current up to approximately 15 times the threshold current. The lasers fail catastrophically at power levels between 65 mW/facet and 85 mW/facet, corresponding to power densities between 2.6 MW/cm2 and 3.4 MW/cm2.
Large optical cavity (LOC) semiconductor laser arrays
- Author(s): M. Jansen ; S.S. Ou ; J.J. Yang ; J. Wilcox ; M. Sergant ; L. Eaton ; W. Simmons
- Source: Electronics Letters, Volume 22, Issue 20, p. 1083 –1084
- DOI: 10.1049/el:19860742
- Type: Article
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Schottky barrier and oxide-restricted ridge-waveguide large optical cavity (LOC) arrays were fabricated and tested. Both evanescently coupled and diffraction-coupled array geometries were evaluated in terms of lateral and transverse mode behaviour. The array stripes were 3 μm wide, with a separation of 4.5, 6, 7.5 and 9 μm from centre to centre. Peak powers of over 2W were obtained for 11-element devices, with typical threshold currents in the range of 20–25 mA/ stripe and differential quantum efficiencies of more than 60%. Single-lobe lateral far-field patterns were obtained for evanescently coupled arrays with a centre-to-centre stripe spacing of 4.5 μm and for diffraction-coupled arrays with a centre-to-centre stripe spacing of 6 μm and with 30 μm-long diffraction regions. The transverse-mode behaviour was investigated as a function of the guiding layer width.
Narrowband tunable optical filter for channel selection in densely packed WDM systems
- Author(s): A.R. Chraplyvy and R.W. Tkach
- Source: Electronics Letters, Volume 22, Issue 20, p. 1084 –1085
- DOI: 10.1049/el:19860743
- Type: Article
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Stimulated Brillouin amplification is used for channel selection in a densely packed WDM direct-detection lightwave experiment. Data at 45 Mbit/s were detected error-free with a similar interfering channel as close as 140 MHz away.
Parasitic-insensitive realisation of switched-capacitor leapfrog ladder filters with reduced number of operational amplifiers
- Author(s): P.J. O'Donovan
- Source: Electronics Letters, Volume 22, Issue 20, p. 1085 –1086
- DOI: 10.1049/el:19860744
- Type: Article
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A method for the implementation of SC leapfrog ladder filters is described which requires approximately half the number of op amps used in standard SC designs. The resulting filters utilise a Nyquist rate clock and are insensitive to stray capacitances.
Importance of rapid damping of relaxation oscillations for high-performance optical communication systems
- Author(s): G.P. Agrawal and T.M. Shen
- Source: Electronics Letters, Volume 22, Issue 20, p. 1087 –1088
- DOI: 10.1049/el:19860745
- Type: Article
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The performance of a 1.55 μm lightwave transmission system employing directly modulated single-frequency semiconductor lasers depends on the dynamic characteristics such as the wavelength chirp and the damping of relaxation oscillations. Numerical simulations which include the effect of fibre dispersion and decision-time jitter on the detected power show that rapid damping of relaxation oscillations is critically important for high-bit-rate systems. We discuss how the system performance can be improved by optimising certain laser parameters.
InGaAs/InAlAs heterojunction Schottky transistors grown by MBE
- Author(s): J.C. Vlcek and C.G. Fonstad
- Source: Electronics Letters, Volume 22, Issue 20, p. 1088 –1089
- DOI: 10.1049/el:19860746
- Type: Article
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Heterojunction bipolar transistors incorporating a Schottky collector have been fabricated in In0.53Ga0.47As/In0.52Al0.48As grown by molecular beam epitaxy. Devices show very high emitter-base junction saturation current densities, low offset voltages and current gain greater than unity (≃2.5) in spite of the fact that no attempt was made to isolate the extrinsic base-emitter junction.
Erratum: Fast convergence method for Lloyd-Max quantiser design
- Author(s): K.N. Ngan and K.S. Leong
- Source: Electronics Letters, Volume 22, Issue 20, page: 1089 –1089
- DOI: 10.1049/el:19860747
- Type: Article
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Erratum: Spontaneous Brillouin scattering for single-mode optical-fibre characterisation
- Author(s): R.W. Tkach ; A.R. Chraplyvy ; R.M. Derosier
- Source: Electronics Letters, Volume 22, Issue 20, page: 1089 –1089
- DOI: 10.1049/el:19860748
- Type: Article
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