Online ISSN
1350-911X
Print ISSN
0013-5194
Electronics Letters
Volume 23, Issue 23, 5 November 1987
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Volume 23, Issue 23
5 November 1987
Simple method for increasing current gain and voltage ratings of power transistors
- Author(s): A. Silard ; F. Floru ; C. Stefan ; G. Nani
- Source: Electronics Letters, Volume 23, Issue 23, p. 1213 –1214
- DOI: 10.1049/el:19870844
- Type: Article
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The letter presents a simple design/technological approach which increases both the (DC and small-signal) current gains and the voltage ratings (VCEO(SVS) and VCBO) of power bipolar transistors. The novel method offers a fair balance between cost-effectiveness and overall device performance, the electro-thermal reliability included.
Resistance of Ti:LiNbO3 devices to ionising radiation
- Author(s): E.I. Drummond
- Source: Electronics Letters, Volume 23, Issue 23, p. 1214 –1215
- DOI: 10.1049/el:19870845
- Type: Article
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Optical waveguide devices of titanium diffused into lithium niobate were exposed to ̃105rad of 2.25 MeV β particles and 35 keV X-rays. At a wavelength of 1.3μm, no change was detected in transmission or coupling between adjacent guides, either during or after irradiation.
Second-harmonic generation in single-mode optical fibres
- Author(s): F.P. Payne
- Source: Electronics Letters, Volume 23, Issue 23, p. 1215 –1216
- DOI: 10.1049/el:19870846
- Type: Article
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We consider the origin of frequency-doubling in single-mode optical fibres. We show that the presence of nonlinear electric quadrupole and magnetic dipole moments can explain the initial formation of frequency-doubled light, and present the results of a detailed theoretical analysis of these effects which is in good agreement with experiment.
New tungsten silicide thin-film resistor technology applied to GaAs integrated circuits
- Author(s): D.A. Allan ; M.J. Gilbert ; P.J. O'Sullivan
- Source: Electronics Letters, Volume 23, Issue 23, p. 1216 –1218
- DOI: 10.1049/el:19870847
- Type: Article
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Tungsten silicide resistors in the range 50–300 ω sheet resistance have been deposited on GaAs by RF sputtering and patterned by etching in an SF6 plasma. High-temperature stability has been demonstrated and a change in resistance of less than 01% after lOOOh at 125°C achieved with passivated resistors.
Decision-directed nonlinear filter for image processing
- Author(s): G. Ramponi and G.L. Sicuranza
- Source: Electronics Letters, Volume 23, Issue 23, p. 1218 –1219
- DOI: 10.1049/el:19870848
- Type: Article
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A complete quadratic Volterra filter working under the control of a decision algorithm is proposed for image restoration and enhancement. A particular application in the enhancement of images having reduced luminance dynamics is considered.
OTDR in a 147 km single-mode fibre in 1.55 μm wavelength region using an LD and GaInAs/InP APD at room temperature
- Author(s): Y. Namihira ; Y. Horiuchi ; H. Wakabayashi ; T. Oshimi ; K. Kitagawa ; T. Ooka
- Source: Electronics Letters, Volume 23, Issue 23, p. 1219 –1221
- DOI: 10.1049/el:19870849
- Type: Article
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A Rayleigh backscattered signal over 147.7 km of single-mode optical fibre has been observed for the first time by long-range, optical time-domain reflectometry (OTDR) usinga 1.54 μm high-power semiconductor laser (LD) and a GaInAs/InP APD with a small dark current at room temperature. A one-way backscattered dynamic range of 29.3 dB at room temperature has been achieved.
Novel CMOS latch with clock hysteresis
- Author(s): D.W.R. Orton
- Source: Electronics Letters, Volume 23, Issue 23, p. 1221 –1222
- DOI: 10.1049/el:19870850
- Type: Article
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A latch circuit is described which tolerates the use of slow and skewed clock signals. The low-complexity circuit has been shown to provide a safe alternative to the use of non-overlapping clocks, and enables the minimisation of clock interconnection and power.
Uniformity of threshold voltage for MESFETs fabricated on VGF GaAs substrates
- Author(s): C.L. Reynolds ; W.C. Gibson ; J.E. Clemans
- Source: Electronics Letters, Volume 23, Issue 23, p. 1222 –1223
- DOI: 10.1049/el:19870851
- Type: Article
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Improved uniformity of threshold voltage is shown for MESFETs fabricated on GaAs substrates grown by a novel vertical gradient freeze technique when compared to devices fabricated on LEC GaAs substrates. The improved uniformity is most likely related to the decreased dislocation density and reduced impurity clustering in the VGF material.
Linewidth enhancement in quantum-well lasers
- Author(s): L.D. Westbrook and M.J. Adams
- Source: Electronics Letters, Volume 23, Issue 23, p. 1223 –1225
- DOI: 10.1049/el:19870852
- Type: Article
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We have developed explicit approximations for the Hnewidth enhancement factor in quantum-well lasers. These simple expressions represent a quick and easy means of calculating the linewidth enhancement factor under a variety of operating conditions, and help us to understand the physics influencing this important parameter.
Measurements of high-Tc superconductivity in a microwave cavity
- Author(s): T.M.P. Percival ; J.S. Thorn ; R. Driver
- Source: Electronics Letters, Volume 23, Issue 23, p. 1225 –1226
- DOI: 10.1049/el:19870853
- Type: Article
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Measurements on a cylindrical microwave cavity with yttrium barium copper oxide end-plates show that this new class of superconductor has low loss at microwave frequencies. Low-loss microwave components operating at liquid nitrogen temperatures could be built using this compound.
Dual aperture-coupled microstrip antenna for dual or circular polarisation
- Author(s): A. Adrian and D.H. Schaubert
- Source: Electronics Letters, Volume 23, Issue 23, p. 1226 –1228
- DOI: 10.1049/el:19870854
- Type: Article
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A new method for radiating dual or circular polarisation with a printed circuit antenna element is described. A square microstrip patch on one substrate is coupled to a pair of microstriplines on another substrate via two orthogonal, rectangular apertures in a common ground plane. Quadrature excitation of the system results in circularly polarised radiation.
Sampled optical time-division multiplexing of asynchronous data
- Author(s): P.J. Chidgey and D.W. Smith
- Source: Electronics Letters, Volume 23, Issue 23, p. 1228 –1229
- DOI: 10.1049/el:19870855
- Type: Article
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A simple and novel sampling technique for optical timedivision multiplexing circuit and packet switched data is proposed using a gain-switched distributed feedbacksemiconductor laser and lithium niobate modulators. System error rate measurements on a two-channel system multiplexing data at 140 Mbit/s and 50 Mbit/s are given and operating penalties analysed.
Room-temperature operation of Ga0.47In0.53As/AI0.48In0.52As resonant tunnelling diodes
- Author(s): S. Sen ; F. Capasso ; A.L. Hutchinson
- Source: Electronics Letters, Volume 23, Issue 23, p. 1229 –1231
- DOI: 10.1049/el:19870856
- Type: Article
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The first room-temperature operation of Ga0.47In0.53As/Al0.48In0.52As resonant tunnelling (RT) diodes is reported. The peak/valley ratio of the current is as high as 4:1 at room temperature and is 15:1 at 80 K. These are the highest values of peak/valley ratio at the respective temperatures, reported so far, in this material system. The position of the peak in the current/voltage characteristic also showed good agreement with that obtained from an electron tunnelling transmission calculation.
New approach to analysing conductor-dielectric periodic structures
- Author(s): Tian-Lin Dong
- Source: Electronics Letters, Volume 23, Issue 23, p. 1231 –1232
- DOI: 10.1049/el:19870857
- Type: Article
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A new approach to analysing conductor-dielectric periodic structures is presented. The formulations can take the transverse resonance conditions in both conductor and dielectric segments and the effects of their thickness into account. The measurements of the frequency-scanning characteristics of a leaky-wave antenna are in good agreement with the theory.
High-speed GaInAsP/InP buried-heterostructure optical intensity modulator with semi-insulating InP burying layers
- Author(s): H. Soda ; K. Nakai ; H. Ishikawa ; H. Imai
- Source: Electronics Letters, Volume 23, Issue 23, p. 1232 –1234
- DOI: 10.1049/el:19870858
- Type: Article
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GaInAsP/InP buried-heterostructure (BH) optical intensity modulators have been fabricated by the use of Fe-doped semi-insulating InP burying layers. The reduction of a parasitic capacitance due to the semi-insulating burying layers realised a wide modulation bandwidth of 11.2GHz. At a wavelength of 1.53/μm, an attenuation ratio of 20 dB at 26°C was achieved with an applied voltage of −8.5 V.
Endless polarisation state matching control experiment using two controllers of finite control range
- Author(s): C.J. Mahon and G.D. Khoe
- Source: Electronics Letters, Volume 23, Issue 23, p. 1234 –1235
- DOI: 10.1049/el:19870859
- Type: Article
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The experimental results of a new, endless polarisation state matching (PSM) control scheme which requires only two finite control range controllers are presented. Only one controller is required to maintain PSM conditions. The second controller is only utilised during the reset procedure. The consequently simplified control protocol can maintain PSM conditions even during resets.
Electro-optic effects and electroabsorption in a GaAs/AlGaAs multiquantum-well heterostructure near the bandgap
- Author(s): M. Glick ; D. Pavuna ; F.K. Reinhart
- Source: Electronics Letters, Volume 23, Issue 23, p. 1235 –1237
- DOI: 10.1049/el:19870860
- Type: Article
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We report phase difference measurements at 50 and 30 meV from the excitonic peak of a GaAs/AlGaAs multiquantum-well structure. We find pronounced dispersion of the quadratic effect; in contrast, we see no indication of dispersion in the linear effect even this close to the bandgap.
Connection-based media access for multichannel local and metropolitan area networks
- Author(s): B.P. Mohanty and T.D. Todd
- Source: Electronics Letters, Volume 23, Issue 23, p. 1237 –1238
- DOI: 10.1049/el:19870861
- Type: Article
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A multichannel access technique is proposed for local and metropolitan area networks. The method presented achieves load balancing in a single-connection environment by employing a dynamic channel assignment scheme. Analytic and simulation results show that the nonpersistent mode of the protocol performs as well as the best existing multichannel CSMA/CD protocol. This is accomplished with a considerable reduction in hardware per network connection.
Connection of VLSI chips to printed circuit board using stacked solder bumps
- Author(s): S. Sasaki ; T. Kishimoto ; N. Matsui
- Source: Electronics Letters, Volume 23, Issue 23, p. 1238 –1240
- DOI: 10.1049/el:19870862
- Type: Article
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A new type of flip-chip interconnection technology usingstacked solder bumps is proposed, where the diameter of theupper solder bump is less than that of the lower ones. This isto reduce the capacitance between the stacked solder bumps and the ground plane and to prolong the lifetime ofthe solder joints.
High-brightness, high-efficiency, single-quantum-well laser diode array
- Author(s): D.F. Welch ; M. Cardinal ; W. Streifer ; D.R. Scifres ; P.S. Cross
- Source: Electronics Letters, Volume 23, Issue 23, p. 1240 –1241
- DOI: 10.1049/el:19870863
- Type: Article
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Single-quantum-well, separate-confinement double-heterostructure laser diode arrays which exhibit a high power conversion efficiency of greater than 54% have been demonstrated. The high efficiency results from a low internal loss of 3cm1 and high internal conversion efficiency. The maximum output power for a 100μm emitting aperture is 2 W CW and is independent of the cavity length.
Characterisation of a fibre Raman oscillator using fibre grating reflectors
- Author(s): P.N. Kean ; K. Smith ; B.D. Sinclair ; W. Sibbett ; C.J. Rowe ; D.C.J. Reid
- Source: Electronics Letters, Volume 23, Issue 23, p. 1241 –1243
- DOI: 10.1049/el:19870864
- Type: Article
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We have constructed a completely integrated fibre Raman oscillator using two fibre grating reflectors. This was synchronously mode-locked using a CW mode-locked Nd:YAG laser operating at 1.06μm. Spectral and temporal characteristics of the Raman oscillator are presented.
Frequency stabilisation of FDM optical signals originating from different locations
- Author(s): B. Glance ; J. Stone ; P.J. Fitzgerald ; K.J. Pollock ; C.A. Burrus ; L.W. Stulz
- Source: Electronics Letters, Volume 23, Issue 23, p. 1243 –1245
- DOI: 10.1049/el:19870865
- Type: Article
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Frequency stabilisation of FDM optical signals to a comb of equally spaced frequencies has been demonstrated for optical signals originating from different locations. The result was achieved by locking each optical source to a resonance of a separate fibre Fabry-Perot cavity. The Fabry-Perot's comb of resonances was synchronised by locking all these devices to a master reference. Implementation of the frequency stabilisation circuit requires, at each location, a tunable fibre Fabry-Perot resonator, a photodetector and simple electronics. Such a simple circuit provides the means to frequency-stabilise a large number of FDM optical sources originating from different locations, as in a star network.
Improved method of measuring loss and phase shifts in waveguide devices
- Author(s): I.D. Henning and P.M. Rodgers
- Source: Electronics Letters, Volume 23, Issue 23, p. 1245 –1246
- DOI: 10.1049/el:19870866
- Type: Article
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The letter presents two novel methods, based on Fabry-Perot interference, for the characterisation of passive and active waveguide devices. Loss measurements have been made on passive devices using a distributed feedback laser as a frequency-tunable source. Simultaneous measurement of phase shift and loss are obtained for a phase modulator by using the electro-optic effect.
Broadband correlators employing fibre-optic recirculating delay lines
- Author(s): P.V. Gatenby ; D.L. Switzer ; N. Green
- Source: Electronics Letters, Volume 23, Issue 23, p. 1246 –1248
- DOI: 10.1049/el:19870867
- Type: Article
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A novel method of correlating broadband signals is proposed based on a pair of fibre-optic recirculating delay lines (RDLs). An implementation based on active single-mode fibre RDLs is described and the performance potential for such a scheme is assessed.
Narrow-aperture SAW filter with both transducers finger-length-weighted
- Author(s): C.D. Blake
- Source: Electronics Letters, Volume 23, Issue 23, p. 1248 –1249
- DOI: 10.1049/el:19870868
- Type: Article
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A 2.5 λ-aperture SAW filter has been designed and tested. The single-mode nature of the waveguiding filter allows finger-length-weighting to be distributed between input and output transducers according to a simple procedure. The resulting filter has a stopband rejection in excess of 50 dB.
Dynamic response of an integrated optoelectronic logic device
- Author(s): P. Wheatley ; G. Parry ; J.E. Midwinter ; G. Hill ; M. Mistry ; A. Pate ; J.S. Roberts
- Source: Electronics Letters, Volume 23, Issue 23, p. 1249 –1250
- DOI: 10.1049/el:19870869
- Type: Article
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A monolithically integrated form of optoelectronic logic device, based on a GaAs/AlGaAs multiple-quantum-well modulator, has been fabricated using MOVPE and tested. The dynamic response of the device is modelled theoretically and tested experimentally, and good agreement is found over a substantial range
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