Online ISSN
1350-911X
Print ISSN
0013-5194
Electronics Letters
Volume 25, Issue 5, 2 March 1989
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Volume 25, Issue 5
2 March 1989
Phase matching in magneto-optic YIG films by waveguide temperature control
- Author(s): J.P. Castera ; P.L. Meunier ; J.M. Dupont ; A. Carenco
- Source: Electronics Letters, Volume 25, Issue 5, p. 297 –298
- DOI: 10.1049/el:19890207
- Type: Article
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We have demonstrated the tuning of linear birefringence in magneto-optic planar thin-film waveguides by temperature adjustment. Using this method, phase matching between coupled TE0 and TM0 modes, a necessary condition for the integrated optical isolator based on mode conversion, has been obtained at λ = 1.52 µm in bilayer gadolinium galliumsubstituted YIG films. The waveguide temperature was 85°C. Moreover, the phase-matching temperature can be modified by a slight variation of gadolinium and gallium substitutions as shown by a phase matching observed in a waveguide at room temperature.
Highly efficient 980 nm operation of an Yb3+-doped silica fibre laser
- Author(s): J.R. Armitage ; R. Wyatt ; B.J. Ainslie ; S.P. Craig-Ryan
- Source: Electronics Letters, Volume 25, Issue 5, p. 298 –299
- DOI: 10.1049/el:19890208
- Type: Article
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–299
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Efficient operation of an Yb3+-doped silica-fibre laser at 980 nm is reported. When pumped with a dye laser at 890 nm, and with a symmetrical cavity, a lasing threshold of 17 mW launched power and a single-ended slope efficiency of nearly 40% against launched pump power has been achieved.
Negative differential resistance in InP JFETs
- Author(s): W. Kruppa and J.B. Boos
- Source: Electronics Letters, Volume 25, Issue 5, p. 299 –301
- DOI: 10.1049/el:19890209
- Type: Article
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Negative differential resistance, as evidenced by DC and microwave measurements, has been observed in InP JFETs for a range of channel geometries and bias values. These results, adjusted for possible substrate current, are shown to be consistent with the simple theory of stationary Gunn domain formation.
Relative transmission loss of teand tm-like modes in metal-coated coupler halves
- Author(s): A. Kumar ; D. Uttamchandani ; B. Culshaw
- Source: Electronics Letters, Volume 25, Issue 5, p. 301 –302
- DOI: 10.1049/el:19890210
- Type: Article
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The relative transmission losses of TE-and TM-like waves through a metal-coated coupler half is measured as a function of the overlay index. For very thin metal films, the TE-like wave was found to be more lossy than the TM-like wave for certain overlay indices. The present study should find applications in the design of inline fibre-optic polarisers and sensors.
Analogue neural networks with distributed neurons
- Author(s): S. Satyanarayana ; Y. Tsividis ; H.P. Graf
- Source: Electronics Letters, Volume 25, Issue 5, p. 302 –304
- DOI: 10.1049/el:19890211
- Type: Article
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A new technique is proposed for implementing neurons in analogue electronic neural networks. It features integrating a fraction of a neuron with each synapse. Each neuron is distributed over all associated synapses. This methodology operates with just one building block, the distributed-neuron synapse, in contrast to existing techniques which are based on two distinct blocks, the neuron and synapse. This approach can be applied to a variety of implementations, including transconductor and MOSFET-op-amp neural networks. Modularity, ease of interconnectivity, expandability and reconfigurability are the advantages of this technique.
Pure frequency modulation or intensity modulation with suppressed frequency chirp using active Bragg reflector integrated laser
- Author(s): E. Goobar ; R. Schatz ; B. Broberg ; S. Nilsson
- Source: Electronics Letters, Volume 25, Issue 5, p. 304 –305
- DOI: 10.1049/el:19890212
- Type: Article
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The modulation properties of a laser structure which consists of an active Bragg reflector (300µm) integrated with an uncorrugated gain region (600µm) have been measured. The laser exhibited a flat FM response and very low spurious intensity modulation when modulating the current in the Bragg reflector. Furthermore, broadband intensity modulation with suppressed frequency chirp could also be achieved. An inhomogeneous linewidth enhancement factor α caused by the uneven carrier density distribution between the two sections gives a qualitative explanation to our results.
Technique for compensation of errors in analogue multipliers
- Author(s): A. Cichocki and R. Unbehauen
- Source: Electronics Letters, Volume 25, Issue 5, p. 305 –307
- DOI: 10.1049/el:19890213
- Type: Article
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A new method for significantly reducing the effect of nonlinear errors on the performance of an analogue multiplier is presented. The method is especially well suited for switched-capacitor devices where time-shared (multiplexing) techniques can be easily employed. However, the method is quite general in nature and can be applied to any type of analogue integrated multiplier. The effectiveness of the technique has been checked through extensive simulation studies.
Ultrasonic experiments with lead zirconate titanate thin films fabricated by sol gel processing
- Author(s): G. Yi ; Z. Wu ; K. Sreenivas ; M. Sayer ; C.K. Jen ; G. Perluzzo
- Source: Electronics Letters, Volume 25, Issue 5, p. 307 –309
- DOI: 10.1049/el:19890214
- Type: Article
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Surface and bulk acoustic wave measurements with lead zirconate titanate (PZT) thin films fabricated by a sol gel processing technique are reported for the first time. The piezoelectricity of such films was achieved by poling. Good acoustic properties of these films are confirmed by the acoustic images and V(z) curves obtained by a scanning acoustic microscope.
Supervisory system for cascaded semiconductor laser amplifier repeaters
- Author(s): A.D. Ellis ; W.A. Stallard ; D.J. Malyon
- Source: Electronics Letters, Volume 25, Issue 5, p. 309 –311
- DOI: 10.1049/el:19890215
- Type: Article
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A technique for locating a transmission path failure in an inline cascade of semiconductor laser amplifier repeaters to within one fibre span is demonstrated. If a fault occurs, the loss of signal is detected in the following repeaters and a locally generated tone modulates the spontaneous emission of the repeater, signalling the fault to the system terminals.
Novel technique for investigating high-power microwave pulses using Kerr effect
- Author(s): R.K. Khanna and P.K. Sharma
- Source: Electronics Letters, Volume 25, Issue 5, p. 311 –312
- DOI: 10.1049/el:19890216
- Type: Article
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A novel method for the measurement of peak power of microwave pulses up to the few hundred kilowatts level based on the microwave-induced electro-optical Kerr effect in nonlossy dielectric liquids is described. This method provides additional information about the shape of the pulse, which is not usually given by the conventional methods.
Pseudolapped orthogonal transform
- Author(s): H.S. Malvar
- Source: Electronics Letters, Volume 25, Issue 5, p. 312 –314
- DOI: 10.1049/el:19890217
- Type: Article
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The pseudo-LOT, a modified version of the lapped orthogonal transform (LOT), is introduced. It can be viewed as either a block transform with overlapping basis functions or a critically-sampled multirate filter bank with nearly perfect reconstruction. A fast algorithm for the pseudo-LOT, based on the discrete cosine transform, is presented.
Polarisation-insensitive, near-travelling-wave semiconductor laser amplifiers at 1.5 µm
- Author(s): S. Cole ; D.M. Cooper ; W.J. Devlin ; A.D. Ellis ; D.J. Elton ; J.J. Isaac ; G. Sherlock ; P.C. Spurdens ; W.A. Stallard
- Source: Electronics Letters, Volume 25, Issue 5, p. 314 –315
- DOI: 10.1049/el:19890218
- Type: Article
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–315
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A polarisation-insensitive, near-travelling-wave semiconductor laser amplifier (TWSLA) is presented. Polarisation sensitivity of less than 1 dB is demonstrated. We believe this to be the lowest reported polarisation sensitivity for a TWSLA. In addition, the saturated output power is in excess of 5.2 dBm.
Analysis of a double latch synchroniser circuit
- Author(s): T.A. Jackson and A. Albicki
- Source: Electronics Letters, Volume 25, Issue 5, p. 315 –316
- DOI: 10.1049/el:19890219
- Type: Article
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A model for a synchroniser composed of two serially connected D-latches is constructed and analysed to determine the mean time between failures. The analysis demonstrates that the best synchroniser reliability is obtained using a single-latch synchroniser.
Technique for polynomial factorisation employing optimised iterative method
- Author(s): J.T. Taylor ; D.G. Haigh ; L.F. Lind
- Source: Electronics Letters, Volume 25, Issue 5, p. 316 –318
- DOI: 10.1049/el:19890220
- Type: Article
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An iterative procedure based on the Newton-Raphson process for the factorisation (splitting) of a real-coefficient polynomial into two lower-degree polynomials is reviewed, and the method extended to the case where the Jacobian matrix is not updated at each iteration (a ‘quasi-Newton’ process). This can result in a faster process. In the case of a particular class of problems, an optimal rate of update of the Jacobian matrix is determined, which results in a further reduction in computation time. This represents a significant improvement in performance, especially if the algorithm is to be used as part of an iterative network design package.
Lasing at 1.00 µm in erbium-doped fluorozirconate fibres
- Author(s): J.Y. Allain ; M. Monerie ; H. Poignant
- Source: Electronics Letters, Volume 25, Issue 5, p. 318 –319
- DOI: 10.1049/el:19890221
- Type: Article
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–319
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Continuous-wave lasing has been obtained at 1.00 µm in erbium-doped fluorozirconate fibres. This laser operates as three-level system. Data concerning saturation of absorption at 488 and 514.5 nm, and absorption and fluorescence from the lasing level are also reported.
8 Gbit/s FSK modulation of DFB lasers with optical demodulation
- Author(s): A.R. Chraplyvy ; R.W. Tkach ; A.H. Gnauck ; B.L. Kasper ; R.M. Derosier
- Source: Electronics Letters, Volume 25, Issue 5, p. 319 –321
- DOI: 10.1049/el:19890222
- Type: Article
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Single-contact DFB lasers were frequency modulated by pseudorandom data at rates up to 8 Gbit/s by direct current modulation with no pre-equalisation of the modulation signal. The signals were optically demodulated by Fabry-Perot interferometers for conversion to ASK signals which were detected by a direct-detection receiver. At 8 Gbit/s the receiver sensitivity was − 22dBm.
Optical-fibre surface-plasmon-wave polarisers with enhanced performance
- Author(s): M.N. Zervas and I.P. Giles
- Source: Electronics Letters, Volume 25, Issue 5, p. 321 –323
- DOI: 10.1049/el:19890223
- Type: Article
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The effect of a thin metal film with positive dielectric permittivity on the performance of an optical-fibre surfaceplasmon-wave polariser is presented. A dramatic improvement has been achieved with polarisation extinction ratios in excess of 45 dB over an extended range of superstrate refractive indices.
Ridged cavity backed slot antenna with dielectric loading
- Author(s): J.H. Cloete and C.F. du Toit
- Source: Electronics Letters, Volume 25, Issue 5, p. 323 –324
- DOI: 10.1049/el:19890224
- Type: Article
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A reduced size cavity backed slot antenna, consisting of a transverse slot in the flat broadwall of a deep single ridge waveguide cavity is described. Partial dielectric loading achieves significant further reduction in electrical size. Moderate dielectric loss increases bandwidth (and significantly reduces antenna gain).
Conjugate pair fast Fourier transform
- Author(s): I. Kamar and Y. Elcherif
- Source: Electronics Letters, Volume 25, Issue 5, p. 324 –325
- DOI: 10.1049/el:19890225
- Type: Article
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A new algorithm for the fast computation of the discrete Fourier transform is introduced. The algorithm, called the conjugate pair FFT (CPFFT), is used to compute a length-2m DFT. The number of multiplications and additions required by the CPFFT is less than that required by the SRFFT algorithm.
Intensity-based fibre-optic sensing system using contrast modulation of subcarrier interference pattern
- Author(s): G. Adamovsky ; T.N. Sherer ; D.J. Maitland
- Source: Electronics Letters, Volume 25, Issue 5, p. 325 –326
- DOI: 10.1049/el:19890226
- Type: Article
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An intensity-based fibre-optic sensor using modulation of the contrast of an interference pattern has been demonstrated. As an example the intensity sensor was chosen to be a displacement sensor. The system has shown high sensitivity and stability.
Biphase linecoding in optical FSK heterodyne transmission experiment, without sensitivity degradation compared to NRZ
- Author(s): P.W. Hooijmans ; M.T. Tomesen ; A. van de Grijp
- Source: Electronics Letters, Volume 25, Issue 5, p. 326 –328
- DOI: 10.1049/el:19890227
- Type: Article
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A biphase linecoding scheme was used in a 140 Mbit/s optical FSK transmission experiment. Owing to the analogue decoding, only 0.3 dB sensitivity penalty was observed, compared to NRZ. A sensitivity of − 54dBm was achieved.
Performance of coded hybrid spread-spectrum communication system in presence of Rician fading and multiple access interference
- Author(s): L. Sadiq and A.H. Aghvami
- Source: Electronics Letters, Volume 25, Issue 5, p. 328 –329
- DOI: 10.1049/el:19890228
- Type: Article
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The letter investigates the performance of an asynchronous hybrid direct sequence/frequency-hopped spread-spectrum communication system in the presence of a combined multiple access interference, Rician fading and thermal noise. The system employs M-ary FSK modulation (M > 2) and a noncoherent demodulator. Several forward error corrections are examined in this study.
Implantation-enhanced oxidation of tantalum for capacitor structures
- Author(s): M.A. Mohammed ; D.V. Morgan ; M. Nobes
- Source: Electronics Letters, Volume 25, Issue 5, p. 329 –330
- DOI: 10.1049/el:19890229
- Type: Article
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The letter investigates the enhanced thermal oxidation of tantalum using oxygen-ion implantation. A comparison of the electrical and dielectric properties is made between the oxygen-implanted thermal oxides and of those fabricated without implantation. The ion-implanted tantalum-oxide films are shown to be superior to the unimplanted layers for the fabrication of oxide capacitors.
Heavy doping for improved short-channel operation of GaAs MESFET
- Author(s): S. Mohammad ; M.B. Patil ; H. Morkoc
- Source: Electronics Letters, Volume 25, Issue 5, p. 331 –332
- DOI: 10.1049/el:19890230
- Type: Article
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A theoretical calculation is performed to investigate the I/V characteristics of GaAs MESFETs. The calculation is based on a simple model that takes into account the dependence of electron mobility on electric field and doping. It is shown that velocity overshoot may be treated by an effective velocity higher than the bulk value.
Acknowledgment-based broadband switching architecture
- Author(s): G. Corazza and C. Raffaelli
- Source: Electronics Letters, Volume 25, Issue 5, p. 332 –334
- DOI: 10.1049/el:19890231
- Type: Article
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A simple architecture for broadband switching based on a multistage interconnection network without internal buffers is proposed. An acknowledgment-based mechanism to manage contention situations that arise in the routing network is provided. The proposed architecture can be used with different kinds of routing networks to obtain a compromise between performance and complexity. For this purpose, performance comparisons between some significant examples of routing networks are also presented.
5 Gbit/s modulation characteristics of optical intensity modulator monolithically integrated with DFB laser
- Author(s): H. Soda ; M. Furutsu ; K. Sato ; M. Matsuda ; H. Ishikawa
- Source: Electronics Letters, Volume 25, Issue 5, p. 334 –335
- DOI: 10.1049/el:19890232
- Type: Article
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Dynamic characteristics under 5 Gbit/s NRZ modulation are reported for a newly developed optical intensity modulator monolithically integrated with a DFB laser. Clear eye opening and a low chirp of less than 0.16 Å are attained with sufficient extinction ratio under this modulation condition.
Exact computation of generalised scattering matrix of suspended microstrip step discontinuity
- Author(s): Jia Sheng Hong ; Jun Ming Shi ; Lin Sun
- Source: Electronics Letters, Volume 25, Issue 5, p. 335 –336
- DOI: 10.1049/el:19890233
- Type: Article
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The generalised scattering matrix of the suspended microstrip step discontinuity is determined by means of an efficient hybrid mode approach which combines a spectral-domain method with a mode-matching technique. Some numerical results are presented.
New method of computing Wigner-Ville distribution
- Author(s): S. Bala Narayanan and K.M.M. Prabhu
- Source: Electronics Letters, Volume 25, Issue 5, p. 336 –338
- DOI: 10.1049/el:19890234
- Type: Article
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The Wigner-Ville distribution (WVD) is of great significance in time-frequency signal analysis. In the letter we present a new method to evaluate the WVD of a real signal using the fast Hartley transform (FHT). This is compared with the existing fast Fourier transform (FFT) method in terms of computation time. The FHT method presented turns out to be much faster than the FFT method.
FIR digital filter design using non-equispaced frequency sampling
- Author(s): B. Summers ; G.D. Cain ; A. Yardim
- Source: Electronics Letters, Volume 25, Issue 5, p. 338 –339
- DOI: 10.1049/el:19890235
- Type: Article
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Frequency-sampling design of FIR digital filters is a well established technique. The method would be of even greater utility if the constraint frequencies could be specified to lie at arbitrary points, rather than just on the standard equispaced grid. Here we show how non-equispaced sampling can easily be achieved, and offer an example of a typical filter design using this flexible new approach.
Dimensioning concurrent packet reassembly at destination on slotted multiaccess network
- Author(s): D. Economou
- Source: Electronics Letters, Volume 25, Issue 5, p. 339 –341
- DOI: 10.1049/el:19890236
- Type: Article
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When variable-length packets are sent on a slotted, multiaccess network the packets must be segmented at the source and reassembled at the destination. Since each packet being received requires a reassembly resource at the destination, there is a need for multiple such resources at the destination. Congestion of these resources will lead to packet loss, but the number of resources may be constrained, so that an essential part of the design for these networks is to predict the requirement for reassembly resources at the destination. The letter describes an analytic model which may be used to do this and also reports simulation results which support the analysis. The analysis is based on a cyclic service queueing model which is an approximation for a distributed queue dual bus (DQDB) network, the authorised IEEE 802.6 Metropolitan Area Network (MAN) project.
Algebraic decoding of class of multilevel pseudocyclic codes
- Author(s): V.C. Da Rocha
- Source: Electronics Letters, Volume 25, Issue 5, p. 341 –342
- DOI: 10.1049/el:19890237
- Type: Article
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The algebraic decoding of a class of multilevel pseudocyclic codes is presented. An affine permutation is employed which does not preserve the original code but changes it into a cyclic code over an extension field. After a cyclic code is obtained the ordinary algebraic decoding techniques are then applicable.
Analysis of spontaneous emission rate of distributed feedback semiconductor lasers
- Author(s): G.H. Duan ; P. Gallion ; G. Debarge
- Source: Electronics Letters, Volume 25, Issue 5, p. 342 –343
- DOI: 10.1049/el:19890238
- Type: Article
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The spontaneous emission rate of distributed feedback semiconductor lasers with partially reflecting facets is analysed using the Green function approach. It is found that this rate depends on both the facet reflectivities and the coupling coefficient. The linewidth of DFB lasers is evaluated by including this dependence.
High-speed division unit using asymmetric neural network architecture
- Author(s): H. Huang and P. Siy
- Source: Electronics Letters, Volume 25, Issue 5, p. 344 –345
- DOI: 10.1049/el:19890239
- Type: Article
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A neural network with symmetric synaptic connections has been shown to be an effective computational unit. However, this model does not always guarantee global convergence nor yield a fast settling time. An asymmetric model without these problems is introduced in the letter. A high-speed divider illustrates its computational capabilities.
New approach for computing radiation pattern of dielectric leaky-wave antenna
- Author(s): M. Ghomi ; H. Baudrand ; C. Cavalli
- Source: Electronics Letters, Volume 25, Issue 5, p. 345 –346
- DOI: 10.1049/el:19890240
- Type: Article
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A novel approach based on a waveguide model is proposed for determining the complex propagation constant of a leaky wave structure by Galerkin's method. Then the far field radiation can be obtained in terms of the tangential electric fields in the Fourier transform domain. By this approach the undesirable sidelobe in the radiation pattern is shown and patterns with lower sidelobes can be obtained.
Use of highly deterministic model in signal-bearing estimation
- Author(s): J. Litva
- Source: Electronics Letters, Volume 25, Issue 5, p. 346 –348
- DOI: 10.1049/el:19890241
- Type: Article
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In the letter we describe an algorithm, based on deterministic modelling, which is called the correlation height analyis (CHA) technique. The algorithm has been designed to be used specifically for radar tracking of low-angle targets over the ocean. In this algorithm we use a low-angle model to generate radar data corresponding to a series of potential target heights. An ensemble of radar signatures are derived which correspond to these heights. We then correlate the simulated data with the radar data and look for peaks in the crosscorrelation function. A series of peaks is obtained. One of these corresponds to the actual target height and the remainder correspond to alias target heights. The alias peaks are analogous to the lobes of an interferometer. The true track is selected from the ensemble of tracks by introducing a perturbation mechanism into the algorithm.
Quantum-well high-efficiency millimetre-wave frequency tripler
- Author(s): A. Rydberg and H. Grönqvist
- Source: Electronics Letters, Volume 25, Issue 5, p. 348 –349
- DOI: 10.1049/el:19890242
- Type: Article
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A quantum-well QW diode frequency tripler with greater than 1.2% efficiency and 0.8 mW output power at about 250 GHz has been developed. A comparison between the experimental results and the theoretically calculated efficiency for a tripler using such a diode is made.
Low-complexity Viterbi-like detector for ‘two-ray’ channels
- Author(s): E. Dahlman
- Source: Electronics Letters, Volume 25, Issue 5, p. 349 –351
- DOI: 10.1049/el:19890243
- Type: Article
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A new type of ‘near’ maximum-likelihood detector is presented. The proposed method is especially suitable for so-called ‘two-ray’ channels with a long impulse response, which may occur for instance in digital mobile radio.
Observation and mechanism of kink effect in depletion-mode AlGaAs/GaAs and AlGaAs/GaInAs HEMTs
- Author(s): A. Thomasian ; A.A. Rezazadeh ; L.G. Hipwood
- Source: Electronics Letters, Volume 25, Issue 5, p. 351 –353
- DOI: 10.1049/el:19890244
- Type: Article
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The appearance and the mechanism of a kink effect (a sudden rise in the drain current) in the output I(V) characteristics of depletion-mode conventional AlGaAs/GaAs and pseudomorphic AlGaAs/GalnAs high-electron-mobility transistors is reported for the first time. The kink is postulated to arise from impact ionisation in the 2-DEG. The generated electrons drift towards the drain, while generated holes are prevented from entering the AlGaAs layer by the heterojunction barrier, and are injected into the GaAs buffer layer. These holes subsequently combine with electrons on the source side of the channel.
Pulsed resonance identification method
- Author(s): G. Quentin and A. Cand
- Source: Electronics Letters, Volume 25, Issue 5, p. 353 –354
- DOI: 10.1049/el:19890245
- Type: Article
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We describe a new method which allows us to identify rapidly the resonances of immersed elastic axisymmetrical objects. It uses short broadband ultrasonic pulses, a Fourier transform and only one angular scanning around the scatterers. We also present some experimental results.
Coherent optical transmission at 565 Mbit/s through five cascaded photonic amplifiers
- Author(s): D.J. Malyon ; R.C. Steele ; M.J. Creaner ; M.C. Brain ; W.A. Stallard
- Source: Electronics Letters, Volume 25, Issue 5, p. 354 –356
- DOI: 10.1049/el:19890246
- Type: Article
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Results are presented for a 565 Mbit/s coherent DPSK. system operating with a laser power amplifier and up to four cascaded laser amplifier repeaters. The importance of maintaining a good signal/spontaneous noise power ratio and low facet reflectivity amplifiers to reduce backward-travelling waves was demonstrated.
Sub-MHz spectral linewidth in 1.5μm separate-confinementheterostructure (SCH) quantum-well DFB LDs
- Author(s): S. Takano ; T. Sasaki ; H. Yamada ; M. Kitamura ; I. Mito
- Source: Electronics Letters, Volume 25, Issue 5, p. 356 –357
- DOI: 10.1049/el:19890247
- Type: Article
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Extremely narrow spectral-linewidth characteristics in 1.5μ GaInAs/GaInAsP separate-confinement-heterostructure (SCH), quantum-well (QW), distributed-feedback, laser diodes (DFB LDs) are reported. Narrower linewidths were obtained in lasers with smaller numbers of quantum wells. Sub-MHz linewidth was achieved for the first time in single laser diodes.
Temperature-dependent gain and noise of 1.5 μm laser amplifiers
- Author(s): B. Mikkelsen ; D.S. Olesen ; K.E. Stubkjaer ; Z. Wang ; A.J. Collar ; G.D. Henshall
- Source: Electronics Letters, Volume 25, Issue 5, p. 357 –359
- DOI: 10.1049/el:19890248
- Type: Article
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The variations of gain and noise figure with temperature are investigated for a 1.5 μm laser amplifier with angled facets. The gain is decreasing by 4–8 dB for a temperature increase of 20°C and the noise figure is increasing by 2–4 dB. For both parameters the variation is smallest on the high wavelength side of the gain peak.
Optical control of frequency and phase of GaAs MESFET oscillator
- Author(s): I.D. Blanchflower and A.J. Seeds
- Source: Electronics Letters, Volume 25, Issue 5, p. 359 –360
- DOI: 10.1049/el:19890249
- Type: Article
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Results are presented for a system combining optical injection locking and closed-loop optical-frequency tuning to achieve accurate phase and frequency control of a MESFET oscillator operating at 1.3 GHz. The system might find application in the phase synchronisation of modules in phasedarray antennas, where the phase reference is distributed by an optical-fibre network.
Linear-phase digital audio tone control using dual RRS structure
- Author(s): Rong-Huan Yang
- Source: Electronics Letters, Volume 25, Issue 5, p. 360 –362
- DOI: 10.1049/el:19890250
- Type: Article
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A linear-phase digital filter system using a dual RRS structure for audio tone control is presented. It has very low arithmetic complexity, and can thus be implemented in real time.
Use of recursive binary nesting for coding moving image sequences
- Author(s): P.J. Cordell and R.J. Clarke
- Source: Electronics Letters, Volume 25, Issue 5, p. 362 –363
- DOI: 10.1049/el:19890251
- Type: Article
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Recursive binary nesting (RBN) is a quadtree-based interpolation technique originally developed for still picture coding, which we have modified efficiently to code moving sequences. When the basic technique is used for motion coding, visually disturbing effects occur. The causes of these are identified and the algorithm modified to remove them.
1.2 Gbit/s, 218 km transmission experiment using inline Er-doped optical fibre amplifier
- Author(s): N. Edagawa ; K. Mochizuki ; H. Wakabayashi
- Source: Electronics Letters, Volume 25, Issue 5, p. 363 –365
- DOI: 10.1049/el:19890252
- Type: Article
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The first optical fibre transmission experiment using an Erdoped optical fibre amplifier as an optical repeater is reported. With an optical repeater gain of 20 dB, 1.2 Gbit/s intensity-modulated optical signals were transmitted along a 218 km dispersion-shifted optical fibre without any optical filters and without any degradation.
Phase-locked array of antiguided lasers with monolithic spatial filter
- Author(s): L.J. Mawst ; D. Botez ; T.J. Roth ; W.W. Simmons ; G. Peterson ; M. Jansen ; J.Z. Wilcox ; J.J. Yang
- Source: Electronics Letters, Volume 25, Issue 5, p. 365 –366
- DOI: 10.1049/el:19890253
- Type: Article
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Phase-locked arrays with monolithically integrated diffractive spatial filters are proposed and demonstrated. Noncollinear sets of antiguides separated by a half-Talbot distance favour in-phase-mode oscillation. Diffraction-limited fundamental-mode operation is obtained to over twice threshold and in far-field patterns with as much as 75% of the energy in the main lobe.
Low-threshold GaInAsP bridge-contacted planar buried-ridge structure lasers
- Author(s): W. Thulke and A. Zach
- Source: Electronics Letters, Volume 25, Issue 5, p. 366 –367
- DOI: 10.1049/el:19890254
- Type: Article
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–367
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A new type of GaInAsP/InP buried-heterostructure laser, the bridge-contacted planar buried-ridge structure (BC-PBRS) laser, is reported. Current confinement is obtained by reducing the effective area of the forward-biased pn homojunctions at both sides of the active region. Owing to the self-aligning process technique, the lateral InP confining layer widths are highly controllable and reproducible. Threshold currents of 10 mA and maximum operation temperatures exceeding 100°C are achieved in the 1.3μm wavelength region.
High-speed microwave switching using laser-controlled microstrip directional coupler
- Author(s): I.L. Andersson
- Source: Electronics Letters, Volume 25, Issue 5, p. 368 –369
- DOI: 10.1049/el:19890255
- Type: Article
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p.
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The transmission characteristics of a new optoelectronic microwave switching device, a laser-controlled microstrip directional coupler, are reported. Measurements show that the characteristics are greatly affected when illuminating the coupling region of the device. Since this device is based on, rather than limited by, capacitive effects, it has the potential for higher-frequency operation than gap discontinuity devices.
Comment: High-power and fundamental-mode oscillating flared SBA lasers
- Author(s): D. Botez
- Source: Electronics Letters, Volume 25, Issue 5, p. 369 –372
- DOI: 10.1049/el:19890256
- Type: Article
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