Online ISSN
1350-911X
Print ISSN
0013-5194
Electronics Letters
Volume 28, Issue 20, 24 September 1992
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Volume 28, Issue 20
24 September 1992
Novel FET active patch antenna
- Author(s): X.-D. Wu ; K. Leverich ; K. Chang
- Source: Electronics Letters, Volume 28, Issue 20, p. 1853 –1854
- DOI: 10.1049/el:19921185
- Type: Article
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A novel dual-FET active patch antenna element for quasi-optical power combining arrays is described. The circuit uses two FETs which symmetrically load a split patch antenna. The push-pull operation of the devices decreases H-plane crosspolarisation dramatically. A power output of 47 mW was achieved at 8.1 GHz.
Continuous complex-valued back-propagation learning
- Author(s): A. Hirose
- Source: Electronics Letters, Volume 28, Issue 20, p. 1854 –1855
- DOI: 10.1049/el:19921186
- Type: Article
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A novel back-propagation learning method is proposed for fully complex-valued layered neural networks. Nonlinearity suitable for realising smooth and unified complex learning is introduced. A gradient descent method is also analysed and optimised so that the variations of independent elements of the output complex vectors are related directly to the fragmentary changes of weighting matrix elements. The learning process is presented and demonstrated.
Pump-wavelength-locked erbium-doped fibre amplifier employing novel external cavity for 0.98 μm laser diode
- Author(s): H. Masuda ; K. Aida ; K. Nakagawa ; K. Yoshino ; M. Wada ; J. Temmyo
- Source: Electronics Letters, Volume 28, Issue 20, p. 1855 –1857
- DOI: 10.1049/el:19921187
- Type: Article
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A novel external cavity configuration for a 0.98 μm strained quantum-well LD set in an erbium-doped fibre amplifier allows the pump wavelength to be locked to within 0.6 nm for LD temperatures from 18.5 to 39°C, and LD drive currents from 40 to 120 mA.
Experimental results for optimum coded digital PPM with Ge APD receiver and Gaussian noise approximated theory
- Author(s): A.J. Massarella and M.J.N. Sibley
- Source: Electronics Letters, Volume 28, Issue 20, p. 1857 –1858
- DOI: 10.1049/el:19921188
- Type: Article
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Practical and theory results are presented for an optical (λ = 1.523 μm) digital PPM system using a suboptimum filtered Ge APD receiver. These original results show that an optimum coding level and APD gain exists for received FWHM Gaussian pulse widths of 11.3 and 35 ns. These optima compare well with those predicted by a suboptimum filter, APD model using Gaussian approximated noise statistics.
Nonlinear mapping performance analysis of the polynomial perceptron
- Author(s): Zengjun Xiang and Guangguo Bi
- Source: Electronics Letters, Volume 28, Issue 20, p. 1858 –1860
- DOI: 10.1049/el:19921189
- Type: Article
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The nonlinear mapping ability of the polynomial perceptron (PP) is analysed, which shows that any continuous functions can be approximated to any given accuracy by the polynomial perceptron with small degree L (L ≥ 2) and the nonlinear mapping ability of the PP is approximately the game as that of the multilayer perceptron (MLP). Numerical results are given.
Equiripple phase for IIR all-pass filters
- Author(s): B.M. Djurich
- Source: Electronics Letters, Volume 28, Issue 20, p. 1860 –1861
- DOI: 10.1049/el:19921190
- Type: Article
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A method is presented for designing IIR all-pass filters, the phase of which approximates a given phase in the equiripple(Chebyshev) sense. The method is exclusively based on the solution of the linear equation system.
Charge storage in vertically integrated GaAs n-channel JFET/junction capacitor device
- Author(s): D.L. Hetherington ; J.F. Klem ; H.T. Weaver
- Source: Electronics Letters, Volume 28, Issue 20, p. 1861 –1863
- DOI: 10.1049/el:19921191
- Type: Article
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A GaAs vertical npn structure in which the bottom layer serves as a JFET charge sensing channel has been fabricated and tested as a dynamic memory element. The device can be read nondestructively and exhibits tens of seconds storage times at room temperature. Use of an n channel for sensing charge provides increased sensitivity compared to earlier p-channel device.
Large-scale and high-density planar lightwave circuits with high-Δ GeO2-doped silica waveguides
- Author(s): S. Suzuki ; K. Shuto ; H. Takahashi ; Y. Hibino
- Source: Electronics Letters, Volume 28, Issue 20, p. 1863 –1864
- DOI: 10.1049/el:19921192
- Type: Article
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GeO2-doped silica waveguides with a high refractive index difference (Δ) of 2% and a propagation loss of 0.1 dB/cm are fabricated on Si substrates. 200 cm-long test circuits and ring resonators are demonstrated, both with a minimum curvature of 2 mm.
Ultrafast polarisation-independent all-optical switching using a polarisation diversity scheme in the nonlinear optical loop mirror
- Author(s): K. Uchiyama ; H. Takara ; S. Kawanishi ; T. Morioka ; M. Saruwatari
- Source: Electronics Letters, Volume 28, Issue 20, p. 1864 –1866
- DOI: 10.1049/el:19921193
- Type: Article
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Polarisation-independent 32 to 8 Gbit/s demultiplexing in the nonlinear optical loop mirror is successfully demonstrated using a novel polarisation diversity scheme in which two independent switching operations are performed along the two principal axes of a polarisation-maintaining fibre loop. The variation of the switched signal powers is measured to be less than 1 dB as the input polarisation direction is varied over 180°.
Highly efficient CW cascade operation of 1.47 and 1.82 μm transitions in Tm-doped fluoride fibre laser
- Author(s): R.M. Percival ; D. Szebesta ; S.T. Davey
- Source: Electronics Letters, Volume 28, Issue 20, p. 1866 –1868
- DOI: 10.1049/el:19921194
- Type: Article
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The 1.475 μm selfterminating transition in a thulium-doped fluorozirconate fibre has been operated CW with thresholds as low as 3.2 mW of launched pump power. Furthermore, by enforcing oscillation at 1.475 and 1.88 μm simultaneously, output powers of ~130 and ~115 mW, respectively, have been observed for around 325 mW of launched pump power. These results correspond to slope efficiencies of 43 and 38%, or photon conversion efficiencies of 82 and 92%, respectively, for the 1.475 and 1.82 μm transitions.
Blue light generation in LiNbO3 waveguide SHG device with first order domain-inverted grating formed by EB scanning
- Author(s): M. Fujimura ; K. Kintaka ; T. Suhara ; H. Nishihara
- Source: Electronics Letters, Volume 28, Issue 20, p. 1868 –1869
- DOI: 10.1049/el:19921195
- Type: Article
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An LiNbO3 waveguide SHG device for blue light generation by first order quasiphase-matching was fabricated using the electron-beam scanning domain inversion technique for the first time. The period of the domain-inverted grating was 3 μm and blue light of wavelength 0.44μm was obtained. The normalised SHG efficiency was 70%/W.
Effect of error-correcting code using DS-3 framing bits on measured dribble-error pattern of 565 Mbit/s fibre optic transmission system
- Author(s): W.D. Grover
- Source: Electronics Letters, Volume 28, Issue 20, p. 1869 –1871
- DOI: 10.1049/el:19921196
- Type: Article
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22 days of error-second data were obtained from a DS-3 tributary of a 565 Mbit/s FOTS to predict the effect of a rate 0.99118 FEC code embedded in the DS-3 masterframe overhead. Using DS-3 masterframe parity to resolve errors within multiply-errored seconds, the code corrects all of the 1189 errors observed. There was no evidence for burstiness at the bit-by-bit timescale.
Use of dynamic RAM in a portable data recorder
- Author(s): X. Huang ; M.J. English ; R. Vincent
- Source: Electronics Letters, Volume 28, Issue 20, p. 1871 –1872
- DOI: 10.1049/el:19921197
- Type: Article
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A portable ECG recorder using dynamic RAM as the recording medium has been developed. In the Letter, the dynamic RAM interface hardware which includes three types of communication mode, that is to a PC, a microcontroller (MCS-51) and an A/D subsystem (AD7821) with dynamic RAMs, is described. This technique opens a new path to the deveopment of low cost, small size and large capacity long-term physiological data recorders.
Erbium-doped composite glass waveguide amplifier
- Author(s): W.J. Wang ; S.I. Najafi ; S. Honkanen ; Q. He ; C. Wu ; J. Glinski
- Source: Electronics Letters, Volume 28, Issue 20, p. 1872 –1873
- DOI: 10.1049/el:19921198
- Type: Article
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Optical amplification at 1.523 μm wavelength is demonstrated in an erbium-doped composite glass waveguide. More than 10 dB amplification is achieved in a 4.7 mm long waveguide with about 30 mW guided pump power of 0.9734 μm wavelength.
Epitaxial AlGaAs/AlAs distributed Bragg reflectors for green (550 nm) lightwaves
- Author(s): D.B. Young ; D.I. Babic ; S.P. Denbaars ; L.A. Coldren
- Source: Electronics Letters, Volume 28, Issue 20, p. 1873 –1874
- DOI: 10.1049/el:19921199
- Type: Article
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Epitaxial AlGaAs/AlAs DBR mirror stacks have been investigated to determine the maximum reflectivity achievable for 550nm wavelength. A maximum reflectivity of greater than 90% has been achieved despite the optical loss in the AlGaAs, and a 70% peak reflectivity can be achieved with as few as five mirror periods.
Comparison of direct and external modulation for CATV lightwave transmission at 1.5 μm wavelength
- Author(s): A.H. Gnauck ; T.E. Darcie ; G.E. Bodeep
- Source: Electronics Letters, Volume 28, Issue 20, p. 1875 –1876
- DOI: 10.1049/el:19921200
- Type: Article
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The use of a high-power 1.5μm DFB laser and a linearised Ti: LiNbO3 Mach-Zehnder modulator as a transmitter in a CATV lightwave system is reported. The performance is compared with directly-modulated 1.5μm-wavelength DFB lasers in 60 channel transmission over 16km of conventional singlemode fibre. The transmission of 52 high-frequency channels is demonstrated (450–750 MHz) in anticipation of future CATV upgrades.
Solving the gate packing problem using a concurrent network
- Author(s): F. Lin and K.-C. Lee
- Source: Electronics Letters, Volume 28, Issue 20, p. 1876 –1878
- DOI: 10.1049/el:19921201
- Type: Article
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The layout problem of gate matrices and one-dimensional logic arrays is composed of two major tasks: to find a permutation of gates which minimises the number of tracks required and to layout/pack gates based on the ordering. A parallel algorithm is presented in the Letter which can pack n gates within O(1) time, whereas the conventional near-optimum algorithm needs O(n2) time. The simulation results show that the increase of the problem size does not degrade the solution quality.
Resonant applicator design for industrial microwave heating
- Author(s): A.P. Duffy and T.M. Benson
- Source: Electronics Letters, Volume 28, Issue 20, p. 1878 –1879
- DOI: 10.1049/el:19921202
- Type: Article
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The use of transmission-line modelling (TLM) as a general tool for designing cavity applications for microwave heating purposes is discussed. This method is used to validate a recent procedure for designing rectangular cavities loaded with an inhomogeneous dielectric layer. The influence of dielectric losses on the cavity resonances is studied.
Observation of spatial solitons in AlGaAs waveguides
- Author(s): J.S. Aitchison ; K. Al-Hemyari ; C.N. Ironside ; R.S. Grant ; W. Sibbett
- Source: Electronics Letters, Volume 28, Issue 20, p. 1879 –1880
- DOI: 10.1049/el:19921203
- Type: Article
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The first observation of spatial optical solitons in the semi-conductor AlGaAs is reported. Operating in the spectral region close to half the bandgap allows the positive nonlinearity of the semiconductor to be fully used, while minimising the effects of two-photon absorption.
Delayed N-path structure for high speed adaptive FIR digital filtering
- Author(s): H.K. Kwan and K. Hirano
- Source: Electronics Letters, Volume 28, Issue 20, p. 1880 –1882
- DOI: 10.1049/el:19921204
- Type: Article
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A structure and its algorithm for high speed adaptive FIR digital filtering based on the delayed N-path concept is presented. Using N2 processors, the throughput rate of the proposed filter can be N2 times faster than that of the same filter realised directly using one such processor.
Three-step pin assignment algorithm for building block layout
- Author(s): S.-G. Choi and C.-M. Kyung
- Source: Electronics Letters, Volume 28, Issue 20, p. 1882 –1884
- DOI: 10.1049/el:19921205
- Type: Article
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A new pin assignment algorithm is proposed which can be use in floorplanning and building block layout to minimise the total wiring length and channel area while satisfying the minimum distance constraint among pin positions on the block boundary. This algorithm can be used in floorplanning in which block shapes are iteratively modified by the channel density obtained as a result of global routing. The proposed pin assignment algorithm occurs in three steps: approximate pin assignment, global routing and detailed pin assignment. Experimental results were obtained using MCNC placement and floorplanning benchamark examples
Finite element method of lines analysis of open periodic structures
- Author(s): M. Davidovitz
- Source: Electronics Letters, Volume 28, Issue 20, p. 1884 –1886
- DOI: 10.1049/el:19921206
- Type: Article
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The applicability of the finite element method of lines to the analysis of open, periodic structures in demonsrated. To validate the method and study its characteristics, the problem of transverse electric (TE) plane wave scattering from a metallic waveguide array is considered. Convergence of the solution is ivestigated both as a function of the mesh density and the order of the polynomial approximation used in the construction of basis functions.
Input impedance of rectangular patch antenna fed by microstrip line
- Author(s): Z. Šipuš ; J. Bartolić ; B. Stipetić
- Source: Electronics Letters, Volume 28, Issue 20, p. 1886 –1888
- DOI: 10.1049/el:19921207
- Type: Article
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A simple full-wave method for analysing rectangular microstrip antennas is presented. The Problem of voltage term calculation is elucidated in the case of the microstripline-fed antenna. A new model for calculating the voltage term is proposed and compared to the other two models take from literature
Quantum well interferometric modulator monolithically integrated with 1.55 μm tunable distributed Bragg reflector laser
- Author(s): J.E. Zucker ; K.L. Jones ; M.A. Newkirk ; R.P. Gnall ; B.I. Miller ; M.G. Young ; U. Koren ; C.A. Burrus ; B. Tell
- Source: Electronics Letters, Volume 28, Issue 20, p. 1888 –1889
- DOI: 10.1049/el:19921208
- Type: Article
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The first monolithically integrated laser/interferometric modulator is reported. The total chip length of 2.5 mm includes a 970 μm-long strained InGaAs/InGaAsP quantum well gain section, a 230 μm-long wavelength tuning section containing a distributed Bragg reflector grating, and an 800 μm-long active length Mach-Zehnder modulator based on electrorefractive InGaAsP/InP quantum wells. 4 V pushpull drive voltage produces 12.5 dB modulation depth with −9 dBm optical power coupled into a cleaved fibre.
Direct dispersion measurement of highly -erbium -doped optical amplifiers using a low coherence reflectometer coupled with dispersive Fourier spectroscopy
- Author(s): K. Takada ; T. Kitagawa ; K. Hattori ; M. Yamada ; M. Horiguchi ; R.K. Hickernell
- Source: Electronics Letters, Volume 28, Issue 20, p. 1889 –1891
- DOI: 10.1049/el:19921209
- Type: Article
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The group delay and dispersion, including the erbium ion contributions, of the highly erbium-doped silica planar wave-guide amplifier and multicomponent glass fibre amplifiers are directly measured at different pump powers using a low coherence reflectometer and dispersive Fourier spectroscopy. This method derives the refractive index spectra of these amplifiers directly from the produced reflectograms without any physical or mathematical assumptions. The dispersion of the planar or mathematical assumptions. The dispersion of the planar waveguide amplifier at 500mW pumping changes between +300 and −200Ps/Km/nm with a 0.4wt% erbium concentration
Comparison of the effect of discrietisation on absorbing boundary algorithms in the finite difference time domain method
- Author(s): C.J. Railton and E.M. Daniel
- Source: Electronics Letters, Volume 28, Issue 20, p. 1891 –1893
- DOI: 10.1049/el:19921210
- Type: Article
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With the recent growth of interest in the finite difference time domain mehtod for the analysis of structures with open boundaries, much investigation is taking place into the use of absorbing boundary algorithms. Most analyses so far have not, however, taken account of finite discretisation. In the Letter, the properties of several popular absorbing boundary conditions are compared, and it is show that, although for mally identical when discretisation is not considered, differences in performance exist when realistic unit cells sizes are used. The best algorithm for general cases is identified.
Unidirectional systolic multiplier
- Author(s): D. Ait-boudaoud
- Source: Electronics Letters, Volume 28, Issue 20, p. 1893 –1894
- DOI: 10.1049/el:19921211
- Type: Article
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A higt throughtput unidirectional systolic multiplier is presented. The new architecture is based on the cell merging approach, where each basic building unit is a radix-2 bit-level cell. A Comparison with the existing pipelined multiplier shows that the proposed architecture reduces the latency by at least 40%
High repetition rate figure eight laser with extracavity feedback
- Author(s): M.L. Dennis and I.N. Duling
- Source: Electronics Letters, Volume 28, Issue 20, p. 1894 –1896
- DOI: 10.1049/el:19921212
- Type: Article
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The operation of an erbium figure eight all-fibre laser with a fundamental repetition rate of 28.5 MHz is reported. The feedback of light rejected by the nonlinear amplifying loop mirror back into the laser is found to stabilise mode locking enhance startup, shorten the pulse lenght to 275fs, and provide a simple means of multiplying the repetition rate.
Gain crosstalk in saturated EDFA for WDM applications
- Author(s): F. Meli ; M. Angellieri ; G. Grasso
- Source: Electronics Letters, Volume 28, Issue 20, p. 1896 –1897
- DOI: 10.1049/el:19921213
- Type: Article
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The Phenomenon of gain crosstalk in saturated EDFAs is experimentally shown and justified. The potential effects on WDM optical networks are demonstrated and quantified.
Simple variational approach to optical rib waveguide analysis
- Author(s): T.M. Benson ; P.C. Kendall ; M.A. Matin
- Source: Electronics Letters, Volume 28, Issue 20, p. 1897 –1898
- DOI: 10.1049/el:19921214
- Type: Article
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A truly variational method for analysing polarised modes in optical rib waveguides is presented. The new method exploits recent advances in rib waveguide analysis where the use of effective widths simplifiers the semiconductor/air interface. Results obtained for both TE and TM polarisation are validated using benchmark results produced using estalished mehtods.
Absolute CMC frequency stabilistation with 0.8 THz control range and OEIC front-end module
- Author(s): U.H.P. Fischer ; C. von helmolt ; K. Krüger ; U. Krüger
- Source: Electronics Letters, Volume 28, Issue 20, p. 1899 –1900
- DOI: 10.1049/el:19921215
- Type: Article
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Absolute coherent multiycarrier (CMC) frequency stabilisation experiments are reported featuring an optogalvanic reference at 1547.825 nm, an offset locking range of 800 GHz with 0.4 GHz resolution and a balanced InP polarisation diversity detector hybrid.
Polynomial interpolation for Remez exchange method
- Author(s): M. Iwaki ; R. Ishii ; K. Toraichi
- Source: Electronics Letters, Volume 28, Issue 20, p. 1900 –1902
- DOI: 10.1049/el:19921216
- Type: Article
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Newton interpolation is proven to work faster when employed in the Remez exchange method. Using Newton interpolation in the method, we can increase the speed of the Remez exchange method which is widely used for the design of linear-phase Chebyshev FIR digital filters.
Nonlinear evolution of ASK and PSK signals in repeaterless fibre links
- Author(s): E. Iannone ; F.S. Locati ; F. Matera ; M. Romagnoli ; M. Settembre
- Source: Electronics Letters, Volume 28, Issue 20, p. 1902 –1903
- DOI: 10.1049/el:19921217
- Type: Article
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The appearance of modulation instability in the propagation of amplitude and phase modulated signals in repeaterless fibre is shown. It is demonstrated that, in the anomalous dispersion region of the fibres, the signal degradation due to the effect of chromatic dispersion may be avoided in the nonlinear regime.
Improved FSK frame synchronisation
- Author(s): M. Grayson and M. Darnell
- Source: Electronics Letters, Volume 28, Issue 20, p. 1904 –1905
- DOI: 10.1049/el:19921218
- Type: Article
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An algorithm for obtaining frame synchronisation which uses soft decision information from an FSK demodulator is described. The algorithm has been derived from the optimum rule for high SNR which was originally developed for ASK transmission. Simulation results are reported that show approximately 1 dB improvement over the pure correlation rule at interesting SNRs compared to a 3dB gain offered by the ASK implementation.
Microwave true time-delay modulator using fibre-optic dispersion
- Author(s): R.D. Esman ; M.J. Monsma ; J.L. Dexter ; D.G. Cooper
- Source: Electronics Letters, Volume 28, Issue 20, p. 1905 –1907
- DOI: 10.1049/el:19921219
- Type: Article
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A new method for providing a continuously variable, true time delay for radio frequency (RF), microwave, and millimetre wave signals using fibre optics is proposed and demonstrated. Variation in time delay up to 1.7 ns and millisecond-order modulation speeds are demonstrated for signals to 20 GHz.
Full-wave analysis of dielectric waveguide ferrite phase shifter with longitudinal magnetisation
- Author(s): R. Andriamanjato ; B. Chan ; J.W. Tao ; H. Baudrand
- Source: Electronics Letters, Volume 28, Issue 20, p. 1907 –1908
- DOI: 10.1049/el:19921220
- Type: Article
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A full-wave analysis of a waveguide containing a longitudinally magnetised ferrite is presented to describe the behaviour of a millimetre wave phase shifter. A variational form is obtained from the transverse operator formalism which enables the dielectric waveguide ferrite phasers to be rigorously studied. The phase shift is predicted, and agrees well with experimental results.
Small signal equivalent circuit of two lateral coupled semiconductor diode lasers
- Author(s): H. Lamela ; G. Carpintero ; P. Acedo ; A. Abella
- Source: Electronics Letters, Volume 28, Issue 20, p. 1908 –1910
- DOI: 10.1049/el:19921221
- Type: Article
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A small signal equivalent circuit of two lateral coupled semiconductor diode lasers is presented. The circuit model is based on the small signal analysis of the rate equations. New elements are found for the out-of-phase modulation. Their values are a function of the coupling coefficient between these lasers. Small signal analysis hasbeen carried out and agrees well with recently published data.
Comparison of thin-wire models for TLM method
- Author(s): J.A. Porti ; J.A. Morente ; M. Khalladi ; A. Gallego
- Source: Electronics Letters, Volume 28, Issue 20, p. 1910 –1911
- DOI: 10.1049/el:19921222
- Type: Article
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Two new wire models for the transmission line modelling (TLM) method are presented. The behaviour of the models is compared with that obtained using the most recent existing wire node and with an independent moments method solution for a 3-D problem.
Influence of carrier transport on wavelength chirp of InGaAs/InGaAsP MQW lasers
- Author(s): A.P. Wright ; B. Garrett ; G.H.B. Thompson ; J.E.A. Whiteaway
- Source: Electronics Letters, Volume 28, Issue 20, p. 1911 –1913
- DOI: 10.1049/el:19921223
- Type: Article
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The effect of carrier transport across the heterostructure on wavelength chirp in 1.5 μm InGaAs/InGaAsP MQW lasers is described both theoretically and experimentally. A reduction in the FSK chirp to below the resolution limit of the measurements is observed together with an increased modulation bandwidth as the carrier transport time is reduced.
Ultimate coupling performances for microlensed fibres
- Author(s): C. Vassallo and J. Michiel van der Keur
- Source: Electronics Letters, Volume 28, Issue 20, p. 1913 –1915
- DOI: 10.1049/el:19921224
- Type: Article
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1913
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(3)
Theoretical results are presented on the coupling efficiency of highly diverging Gaussian beams into a microlensed fibre through hyperbolic and spherical lenses.
Segmentation of the facial area for videophone applications
- Author(s): Haibo Li
- Source: Electronics Letters, Volume 28, Issue 20, p. 1915 –1916
- DOI: 10.1049/el:19921225
- Type: Article
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p.
1915
–1916
(2)
A new segmentation scheme for videophone application is described. In model-based image coding, the facial area must be separated from the head-and-shoulder scene in order to fit a parameterised face model to the face of the speaker. Based on the observation that the head and shoulder of the speaker usually undergo two different motions, a dedicated segmentation scheme can be signed. The experimental results on a real image sequence are presented.
Compact, wideband coherent receiver module with 78% external quantum efficiency
- Author(s): H. Tabuchi ; H. Hamaguchi ; T. Mikawa
- Source: Electronics Letters, Volume 28, Issue 20, p. 1916 –1917
- DOI: 10.1049/el:19921226
- Type: Article
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p.
1916
–1917
(2)
A compact, low-profile, front-end module consisting of a fused fibre coupler and a twin pin photodiode for balanced heterodyne receivers is described. Special packaging and mounting techniques ensure excellent performance from a module only 7 mm high. Figures of merit include a 16.8 GHz wideband response, an extremely low 0.8 dB optical loss, and an overall external quantum efficiency of 78%
250 MHz nMOS relaxation oscillator with enhanced linear voltage-frequency characteristic and temperature stability
- Author(s): T.S. Cheung ; H. Wong ; Y.C. Cheng
- Source: Electronics Letters, Volume 28, Issue 20, p. 1917 –1919
- DOI: 10.1049/el:19921227
- Type: Article
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p.
1917
–1919
(3)
The design of an nMOS relaxation oscillator with an operating frequency of 60–250MHz is presented. The design can be incorporated in a PLL system with centre frequency up to 190 MHz. The oscillator gives a highly linear voltage-frequency characteristic and its temperature coefficient is maintained within ±200 ppm for temperatures ranging from 0 to 80°C. The design was found to be suitable in PLL system applications.
Measurement of excess loss in planar silica X junctions
- Author(s): F. MacKenzie ; C.J. Beaumont ; M. Nield ; S.A. Cassidy
- Source: Electronics Letters, Volume 28, Issue 20, p. 1919 –1920
- DOI: 10.1049/el:19921228
- Type: Article
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p.
1919
–1920
(2)
Planar silica provides a compact and stable medium for the fabrication of optical delay lines for signal processing applications. One particularly compact design involves the use of 90% crossovers (X junctions) to allow coiling of buried channel waveguides to form the delay line without the discontinuity loss associated with loopback structures. The Letter presents measurements of the excess loss due to these and compares the results with theoretical treatment.
Repetition frequency stabilisation of passively mode-locked semiconductor lasers
- Author(s): R.J. Helkey ; D.J. Derickson ; A. Mar ; J.G. Wasserbauer ; J.E. Bowers ; R.L. Thornton
- Source: Electronics Letters, Volume 28, Issue 20, p. 1920 –1922
- DOI: 10.1049/el:19921229
- Type: Article
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p.
1920
–1922
(3)
The repetition frequency of an external cavity mode-locked GaAs semiconductor diode laser has been stabilised by voltage controlled electrical feedback. The phase noise has been reduced by 40 dB at 1 kHz offset from the carrier and timing jitter reduced from more than 30 ps to 4 ps. This technique can be used to stabilise millimetre-wave mode-locked lasers.
Comparison of rainfall rate duration distributions for ILE-IFE and barcelona
- Author(s): E. Vilar ; A. Burgueño ; E.B.C. Ofoche
- Source: Electronics Letters, Volume 28, Issue 20, p. 1922 –1924
- DOI: 10.1049/el:19921230
- Type: Article
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p.
1922
–1924
(3)
A comparative statistical study of durations D of rainfall rates R is presented for the temperate region of Barcelona and the tropical region of Ile-Ife (Nigeria). It is shown that the conditional distribution P(D | R) is log normal for the two regions but the mean duration is smaller for the tropical region than for the temperate one. Consideration is given to the value of D̅ for both regions, to the variability σD and to the database required for the statistical study.
Low noise operation of Er3+ doped silica fibre amplifier around 1.6 μm
- Author(s): J.F. Massicott ; R. Wyatt ; B.J. Ainslie
- Source: Electronics Letters, Volume 28, Issue 20, p. 1924 –1925
- DOI: 10.1049/el:19921231
- Type: Article
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p.
1924
–1925
(2)
A novel method of using two pump wavelengths to achieve high gains and enhanced noise performance in the 1.6 μm Er3+ doped fibre amplifier is demonstrated. By launching 82 mW of power at 1.48 μm and up to 1 mW at 1.555 μm, a maximum gain of 31 dB is achieved at 1.57 μm with gains in excess of 24 dB available between 1.57 and 1.605 μm. The noise figure is maintained below 5dB over this bandwidth, close to the theoretical minimum for a 1.48 μm pumped amplifier.
High-tc bandpass filter using miniaturised microstrip hairpin resonators
- Author(s): A. Enokihara ; K. Setsune ; K. Wasa ; M. Sagawa ; M. Makimoto
- Source: Electronics Letters, Volume 28, Issue 20, p. 1925 –1927
- DOI: 10.1049/el:19921232
- Type: Article
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p.
1925
–1927
(3)
Superconducting bandpass filters of 4.9 GHz with 0.5% relative bandwidth were designed using miniaturised microstrip hairpin resonators and fabricated with GdBa2Cu3Ox thin films prepared on MgO. The passband insertion loss was 0.5dB at 20K and the filter configuration was defined in an area less than 5 × 5 mm2.
Interpolation using the discrete cosine transform
- Author(s): J.I. Agbinya
- Source: Electronics Letters, Volume 28, Issue 20, p. 1927 –1928
- DOI: 10.1049/el:19921233
- Type: Article
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p.
1927
–1928
(2)
Zooming and zero padding interpolation algorithms based on the conventional discrete cosine transform (DCT) are presented. The DCT algorithms are shown to be more accurate and outperform algorithms based on the Wang modified DCT-I which was proposed to replace the DCT for interpolation purposes.
Dwt domain split-path structure LMS adaptive filter
- Author(s): K.F. Wan ; P.C. Ching ; K.C. Ho
- Source: Electronics Letters, Volume 28, Issue 20, p. 1929 –1930
- DOI: 10.1049/el:19921234
- Type: Article
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p.
1929
–1930
(2)
A fast convergence adaptive filtering algorithm based on a split-path configuration and the discrete Walsh transform (DWT) is presented. An adaptive FIR predictor is first mapped to the DWT domain. It is then split into a pair of linear phase subfilters connected in parallel. The filter parameters are adapted using the LMS approach with different convergence step sizes to achieve better learning performance. Walsh-Hadamard ordering is applied to simplify and to speed up the algorithm.
Low-frequency electrostrictive ceramic plate voltage sensor
- Author(s): M.D. Mermelstein and S.T. Vohra
- Source: Electronics Letters, Volume 28, Issue 20, p. 1930 –1932
- DOI: 10.1049/el:19921235
- Type: Article
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p.
1930
–1932
(3)
A stress-driven electrostrictive ceramic is used for the first time to demonstrate a DC and low frequency voltage sensor. The device uses a Ba: PZT ceramic plate as the sensor element and exhibits a sensitivity of 0.68 mV/V and a minimum detectable voltage of 1.4 mV/√(Hz) below 10 Hz. A susceptibility for the coupled polarisation and strain modes is developed and used to quantitatively characterise the sensor operation. Design parameters are suggested for improving the device performance by several orders of magnitude.
Silica-based optical waveguide ring laser integrated with semiconductor laser amplifier on Si substrate
- Author(s): Y. Hibino ; H. Terui ; A. Sugita ; Y. Ohmori
- Source: Electronics Letters, Volume 28, Issue 20, p. 1932 –1933
- DOI: 10.1049/el:19921236
- Type: Article
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p.
1932
–1933
(2)
A compact and stable ring laser at 1.3 μm was demonstrated using an InGaAsP semiconductor laser amplifier (SLA) and a silica-based optical waveguide ring resonator with an FSR of 2 GHz on an Si substrate. Two end facets of the SLA were coupled to lensed optical fibres, the other ends of which were attached without alignment to the waveguide resonator through fibre guiding grooves. A low threshold current of 17 mA was obtained in the ring laser.
Excess noise in cooled l-banded HEMT amplifiers
- Author(s): S. Padin
- Source: Electronics Letters, Volume 28, Issue 20, p. 1933 –1935
- DOI: 10.1049/el:19921237
- Type: Article
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p.
1933
–1935
(3)
Measurements of the noise temperature of a cooled 1–2 GHz HEMT amplifier show excess low frequency noise with several different HEMT devices. The noise appears to be generated in the devices and there is no correlation between the room temperature noise performance and the excess noise observed at 15K. Illuminating the devices does not decrease the excess noise. The effect may be important in determining the optimum first IF frequency for millimetre-wave receiver systems.
Cryptanalysis of Xinmei digital signature scheme
- Author(s): J. van Tilburg
- Source: Electronics Letters, Volume 28, Issue 20, p. 1935 –1936
- DOI: 10.1049/el:19921238
- Type: Article
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p.
1935
–1936
(2)
In 1990, Xinmei proposed a digital signature scheme based on error-correcting codes. It was claimed that the security of the signature scheme relies on the difficulty of factoring large matrices and the properties of error-correcting codes. In the Letter it is shown that the private key in the Xinmei scheme can be obtained directly from the public key. As a result this scheme is insecure. In conclusion a modification proposed by Harn and Wang is briefly discussed.
Explicity formulas for weighting coefficients of maximally flat tunable FIR delays
- Author(s): E. Hermanowicz
- Source: Electronics Letters, Volume 28, Issue 20, p. 1936 –1937
- DOI: 10.1049/el:19921239
- Type: Article
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p.
1936
–1937
(2)
Explicit formulas are derived for the weighting coefficients of maximally flat tunable FIR delayers based on the design of Ko and Lim and a link with another existing method for this purpose is demonstrated. A scheme is also presented for evaluating these coefficients with the minimum possible computation.
Erratum: One-layer feedforward neural network for fast maximum/minimum determination
- Author(s): H.K. Kwan
- Source: Electronics Letters, Volume 28, Issue 20, page: 1937 –1937
- DOI: 10.1049/el:19921240
- Type: Article
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p.
1937
(1)
Erratum: New a-SiC, optically controlled, thyristor-like switch
- Author(s): E.I. Dmitriadis ; N. Georgoulas ; A. Thanailakis
- Source: Electronics Letters, Volume 28, Issue 20, page: 1937 –1937
- DOI: 10.1049/el:19921241
- Type: Article
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p.
1937
(1)
Erratum: Hybrid Er-doped fibre amplifiers at 980–1480 nm for long distance optical communications
- Author(s): J.-M.P. Delavaux ; C.F. Flores ; R.E. Tench ; T.C. Pleiss ; T.W. Cline ; D.J. Digiovanni ; J. Federici ; C.R. Giles ; H. Presby ; J.S. Major ; W.J. Gignac
- Source: Electronics Letters, Volume 28, Issue 20, page: 1937 –1937
- DOI: 10.1049/el:19921242
- Type: Article
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p.
1937
(1)
Erratum: Bipolar magnetometer sensor similar to fluxgate device but having equal input and output sinusoidal frequencies and zero Barkhausen noise
- Author(s): R.N.G. Dalpadado
- Source: Electronics Letters, Volume 28, Issue 20, page: 1937 –1937
- DOI: 10.1049/el:19921243
- Type: Article
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p.
1937
(1)
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