Online ISSN
1350-911X
Print ISSN
0013-5194
Electronics Letters
Volume 25, Issue 4, 16 February 1989
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Volume 25, Issue 4
16 February 1989
Laterally seeded epitaxy enhancement in zone melting recrystallisation by increase of silicon film thickness
- Author(s): Lianjun Liu ; Zhi Jiang ; Pei-Hsin Tsien ; Zhijian Li
- Source: Electronics Letters, Volume 25, Issue 4, page: 250–251 –250–251
- DOI: 10.1049/el:19890175
- Type: Article
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250–251
Polycrystalline silicon films with various thickness on SiO2 with seeding windows were recrystallised at high scan speeds using RF-induced graphite strip heating. It has been found that the laterally seeded epitaxial widths of defect-free silicon films on SiO2 are 40 and 53 �m for film thicknesses of 350 and 500 nm, respectively. For a 1100 nm-thick silicon film, the epitaxy width reaches 100�m. The scan direction of the strip heater was perpendicular to seeding windows in the experiments.
Influence of extinction ratio on performance of optical receivers incorporating laser preamplifiers
- Author(s): A.J. McDonald ; R.S. Fyath ; J.J. O'Reilly
- Source: Electronics Letters, Volume 25, Issue 4, p. 249 –250
- DOI: 10.1049/el:19890174
- Type: Article
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We report the performance degradation of optical receivers incorporating semiconductor laser amplifiers (SLAs) caused by the nonzero extinction ratio of the input optical signal. The resulting sensitivity penalty dependencies on bit rate, SLA gain and facet reflectivity are also investigated. The results clearly show that the new receiver can be more affected by a finite extinction ratio compared to a conventional pin or APD receiver. Using a bandpass optical filter to reduce amplifier spontaneous emission noise will increase the extinction ratio penalty.
Performance of 4×4 optical crossbar switch utilising acousto-optic deflector
- Author(s): P.C. Huang ; W.E. Stephens ; T.C. Banwell ; L.A. Reith
- Source: Electronics Letters, Volume 25, Issue 4, p. 252 –253
- DOI: 10.1049/el:19890176
- Type: Article
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A multicasting photonic space switch reconfigurable in 50 ns is demonstrated utilising commercially available acoustooptic Bragg cells at λ = 0.83 µm. Insertion loss of 15 dB, extinction ratio of 33 dB, crosstalk of −24 dB and polarisation difference of 0.8 dB are reported.
The C-patch: a small microstrip element
- Author(s): G. Kossiavas ; A. Papiernik ; J.P. Boisset ; M. Sauvan
- Source: Electronics Letters, Volume 25, Issue 4, p. 253 –254
- DOI: 10.1049/el:19890177
- Type: Article
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We present a radiating element operating in the UHF and L-bands; its dimensions are smaller than those of conventional square or circular elements. For this type of antenna, good matching is obtained with a coaxial feed, and the omni-directional radiation pattern is achieved using linear polarisation. The bandwidth, however, remains somewhat narrow.
Optical FSK heterodyne detection using image rejection mixer
- Author(s): K. Iwashita
- Source: Electronics Letters, Volume 25, Issue 4, p. 255 –256
- DOI: 10.1049/el:19890178
- Type: Article
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A new optical FSK heterodyne detection scheme is proposed and demonstrated. This scheme uses an optical image rejection mixer. The intermediate frequency bandwidth is the same as ASK heterodyne detection while equalling dual filter FSK detection receiver sensitivity.
Paired block line codes for pure photonic networks
- Author(s): Y. Takasaki
- Source: Electronics Letters, Volume 25, Issue 4, p. 256 –257
- DOI: 10.1049/el:19890179
- Type: Article
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New line coding schemes called paired block codes (PBC) are investigated for application in future pure photonic networks. The first block of each pair utilises coding rule violations to simplify transmission frame structures to facilitate frame processing to complement limited capabilities of photonic logic devices. The second block is provided with sufficient redundancies to attain photonic clock recovery through logical processing. An upper bound efficiency of this type code is 75%.
Performance of GMSK frequency detection with soft decision decoding of block codes using Chase's second algorithm in mobile radio channel
- Author(s): K. Sawai and T. Matsumoto
- Source: Electronics Letters, Volume 25, Issue 4, p. 257 –259
- DOI: 10.1049/el:19890180
- Type: Article
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Bit error rate (BER) performance of a GMSK frequency detection system with soft decision decoding of block codes using Chase's second algorithm is investigated in mobile radio channels. The channel measurement information (CMI) for a bit in the received block is calculated from samples of the received signal envelope (Rs) and the demodulator output (eye level). The CMIs of eye level × Rs and of Rs2 are investigated, and the decoding performances for the CMIs are compared using the Hamming (7,4) code in nonfading (static) and fading channels in laboratory experiments.
Four logic states using two resonant tunnelling diodes
- Author(s): C. van Hoof ; J. Genoe ; M. van Hove ; M. van Rossum ; R. Mertens ; G. Borghs
- Source: Electronics Letters, Volume 25, Issue 4, p. 259 –260
- DOI: 10.1049/el:19890181
- Type: Article
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Using a series connection of two specially designed resonant tunnelling diodes, we observed three negative differential resistance regions, resulting in four possible logic states. This behaviour can be expanded, at least in theory, to n tunnelling diodes, resulting in 2n − 1 times switching and 2n logic states. These new devices can be used for analogue/digital conversion and multivalued logic or as multistate memory cells using only a minimum in device area.
Linewidth narrowing in semiconductor laser pumped all-fibre Brillouin ring laser
- Author(s): P. Bayvel and I.P. Giles
- Source: Electronics Letters, Volume 25, Issue 4, p. 260 –262
- DOI: 10.1049/el:19890182
- Type: Article
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Brillouin lasing in an all-fibre ring resonator made of polarisation-maintaining fibre using a semiconductor laser pump at 830 nm is reported. The stimulated Brillouin scattering (SBS) lasing threshold is 0.91 mW, and the Stokes output is polarised and exhibits linewidth narrowing.
Mathematical models for Hamming code error control system on an HF channel
- Author(s): D.R. Oosthuizen and H.C. Ferreira
- Source: Electronics Letters, Volume 25, Issue 4, p. 262 –264
- DOI: 10.1049/el:19890183
- Type: Article
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p.
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A procedure is presented to develop simple partitioned Markov chains, representing the underlying statistical structure of the block error detection, correction and misdetection events of a block code on a discrete renewal channel. As an example, results obtained with a (7, 4) Hamming code and the HF channel model due to Tsai are presented.
Transfer characteristics of Brillouin fibre amplifiers for use in self-homodyne coherent optical transmission systems
- Author(s): A.S. Siddiqui and S. Andronikidis
- Source: Electronics Letters, Volume 25, Issue 4, p. 264 –266
- DOI: 10.1049/el:19890184
- Type: Article
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264
–266
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We present, for the first time, the basic input-output characteristics of a Brillouin fibre amplifier, and show that these are in good agreement with the first experimental results reported recently by other workers on a novel and potentially very important application of Brillouin amplification in a coherent optical fibre transmission system. For this type of application, theoretical results are also presented on the optical pump power dependence of the amplifier gain per unit optical pump power.
Real-time Doppler analysis of radar signals
- Author(s): F. Baldassini ; L. Pierucci ; F. Pirri ; G. Castellini ; P.L. Emiliani ; M. Bernabo
- Source: Electronics Letters, Volume 25, Issue 4, p. 266 –267
- DOI: 10.1049/el:19890185
- Type: Article
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p.
266
–267
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Pulse Doppler radar Fourier analysis usually requires bulky and complex circuits to obtain a real-time implementation. The letter suggests the feasibility of a spectral analyser by means of commercial programmable gate array devices (PGAs) using Curtis and Wickenden's ‘prime radix recursive algorithm transform’ (PRAT). PRAT leads to simple and regular networks, which can be easily fitted in the proposed devices and then transferred to gate arrays.
Experimental investigation of all-optical switching in fibre loop mirror device
- Author(s): N.J. Doran ; D.S. Forrester ; B.K. Nayar
- Source: Electronics Letters, Volume 25, Issue 4, p. 267 –269
- DOI: 10.1049/el:19890186
- Type: Article
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p.
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–269
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Nonlinear optical switching has been experimentally demonstrated in a monomode fibre loop mirror (Sagnac) interferometer using both Q-switched and CW-mode locked pulses of a Nd: YAG laser at 1.32 µm. The switching crossover for a 25 m loop occurs at 22 W. It has been shown that incomplete switching occurs due to pulse shape effects. The presence of Raman scattering results in a step-like, rather than periodic, response.
Electric-field-dependent photoresponse of multiple quantum well modulator
- Author(s): R.J. Manning ; P.J. Bradley ; A. Miller ; J.S. Roberts ; P. Mistry ; M. Pate
- Source: Electronics Letters, Volume 25, Issue 4, p. 269 –270
- DOI: 10.1049/el:19890187
- Type: Article
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p.
269
–270
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By monitoring the quantum confined Stark effect using subpicosecond laser pulses, we time resolve the field dependence of the photoconductive impulse response of a GaAs/AlGaAs multiple quantum well pin modulator.
External cavity semiconductor laser comprising Brewster-angled rectangular core fibre
- Author(s): R. Bachen ; J.I. Vukusic ; J.R. Cozens ; M. Green
- Source: Electronics Letters, Volume 25, Issue 4, p. 270 –272
- DOI: 10.1049/el:19890188
- Type: Article
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p.
270
–272
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A GaInAsP semiconductor laser diode, with one of its facets Brewster angled, was coupled to a Brewster angled rectangular core fibre to obtain an external cavity. Very good coupling efficiency and a high degree of polarisation of the output beam has been obtained.
Four-wave mixing in travelling-wave semiconductor laser amplifier
- Author(s): F. Favre ; D. LeGuen ; J.-C. Simon ; P. Doussiere
- Source: Electronics Letters, Volume 25, Issue 4, p. 272 –273
- DOI: 10.1049/el:19890189
- Type: Article
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p.
272
–273
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Experiments on codirectional nondegencrate four-wave mixing in a 1.52µm travelling-wave semiconductor laser amplifier are presented. Estimations for the spontaneous carrier lifetime and linewidth enhancement factor are derived from comparison between experimental and calculated results from theory based on signal-induced carrier-density modulation.
System performance of optical fibre preamplifier
- Author(s): M.J. Pettitt ; R.A. Baker ; A. Hadjifotiou
- Source: Electronics Letters, Volume 25, Issue 4, p. 273 –275
- DOI: 10.1049/el:19890190
- Type: Article
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273
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An optical fibre amplifier has been used as an optical preamplifier for a pin detector-based receiver. A maximum amplifier gain of 22 dB has been measured and, at this gain with no additional optical filtering, an improvement of 10.5 dB in receiver sensitivity has been achieved.
Adaptive polarisation diversity receiver configuration for coherent optical fibre communications
- Author(s): A.D. Kersey ; M.J. Marrone ; A. Dandridge
- Source: Electronics Letters, Volume 25, Issue 4, p. 275 –277
- DOI: 10.1049/el:19890191
- Type: Article
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275
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We describe an implementation of the polarisation diversity detection technique for coherent heterodyne communications which maintains the total IF amplitude at a constant level, irrespective of fluctuations in the state of polarisation of either the signal or local oscillator optical fields at the output polarisation beam-splitter.
High power and low optical feedback noise AlGaAs single quantum well lasers
- Author(s): M. Nido ; K. Endo ; S. Ishikawa ; M. Uchida ; I. Komazaki ; K. Hara ; T. Yuasa
- Source: Electronics Letters, Volume 25, Issue 4, p. 277 –278
- DOI: 10.1049/el:19890192
- Type: Article
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–278
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GaAs/AlGaAs single quantum well self-aligned lasers have been developed for optical disc recording. The lasers emitting at 834 nm have realised low optical feedback noise as well as high output power. The lasers have shown less than −130dB/Hz relative intensity noise at 3mW, and stable 50 mW operation (over 500 hours at 50°C ambient).
Novel method for analysis of curved optical rib-waveguides
- Author(s): J.S. Gu ; P.A. Besse ; H. Melchior
- Source: Electronics Letters, Volume 25, Issue 4, p. 278 –280
- DOI: 10.1049/el:19890193
- Type: Article
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p.
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A three-dimensional method for obtaining the bending losses and field distributions of curved integrated optic rib-waveguides is presented. The method is based on a so called ‘line method’ and relies on a discretisation of the potential in the direction of the rib-heights and leads to Bessel-equations in the radial direction. Good agreement with experimental results is obtained.
On the CNET: a rearrangeably nonblocking optical interconnection network
- Author(s): S. Kar and A. Selvarajan
- Source: Electronics Letters, Volume 25, Issue 4, p. 280 –281
- DOI: 10.1049/el:19890194
- Type: Article
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A planar, circular, rearrangeably nonblocking optical switching architecture using N(N − 1) Ti: LiNbO3 directional coupler switches is suggested. Various figures of merit like the signal-to-crosstalk ratio (SXR), insertion loss and fault tolerance are presented. The outline for a distributed routing algorithm in O(N) time is given.
116 photons/bit in a 565 Mbit/s optical DPSK heterodyne transmission experiment
- Author(s): E. Meissner
- Source: Electronics Letters, Volume 25, Issue 4, p. 281 –282
- DOI: 10.1049/el:19890195
- Type: Article
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A 565 Mbit/s DPSK heterodyne experiment is presented. A sensitivity of −50.0 dBm at the receiver input was achieved, which is the best reported value for this data rate. The experimental data match the theory within 1.4 dB.
Planar heterojunction bipolar transistor with an implanted base
- Author(s): J.Y. Yang ; D.L. Plumton ; W.A. White
- Source: Electronics Letters, Volume 25, Issue 4, p. 282 –283
- DOI: 10.1049/el:19890196
- Type: Article
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A novel process to fabricate a planar emitter-up AlGaAs/GaAs heterojunction bipolar transistor HBT, has been developed relying on selective base implantation through the emitter and the heterojunction. The selective base definition means that all three transistor contacts can be made from the top surface, thereby making device integration easier because of the planar surface topology. This simple transistor fabrication process was examined using MOCVD material. Transistors with a DC current gain of 120 have been measured.
Sensitivity of tripole and calthrop fss reflection bands to angle of incidence
- Author(s): L. Musa ; P.W.B. Au ; E.A. Parker ; R.J. Langley
- Source: Electronics Letters, Volume 25, Issue 4, p. 284 –285
- DOI: 10.1049/el:19890197
- Type: Article
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284
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The stability of the transmission response of a tripole FSS as the angle of incidence is increased from 0° to 70° is compared with that for a surface using a three-dimensional version of the element, a calthrop. For TM incidence the drift in frequency of the reflection resonance is 10% for the tripole, but only 2.5% for the calthrop.
Components of bit-rate variation in videoconference signals
- Author(s): M. Ghanbari and D.E. Pearson
- Source: Electronics Letters, Volume 25, Issue 4, p. 285 –286
- DOI: 10.1049/el:19890198
- Type: Article
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285
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The sources of bit-rate variation in a conditional-replenishment videoconference coder were found experimentally to be due to the interaction between coding method and image content. The isolation of the components of variation and the effect on them of buffering and packetisation are reported.
New electronically tunable OTA-C sinusoidal oscillator
- Author(s): R. Senani
- Source: Electronics Letters, Volume 25, Issue 4, p. 286 –287
- DOI: 10.1049/el:19890199
- Type: Article
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p.
286
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A new transconductance-amplifier-capacitor sinusoidal oscillator configuration is introduced which requires only three OTAs (in contrast to previously known circuits which employ four to five OTAs) to facilitate generation of linearly tunable (through an external current or voltage) variable frequency oscillations.
Crosscorrelation of m-sequences over nonprime finite fields
- Author(s): J.J. Komo
- Source: Electronics Letters, Volume 25, Issue 4, p. 288 –289
- DOI: 10.1049/el:19890200
- Type: Article
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The crosscorrelation function of m-sequences over GF(q) where q = pm, p a prime and m an integer greater than 1 is developed. This crosscorrelation function is shown to have three and four levels similar to the case of m-sequences over GF(p) (a prime field) when the elements of GF(q) are expressed as elements of a vector space over the pth roots of unity. These nonbinary m-sequences can improve performance over binary m-sequences in spread spectrum and code division multiple access communication systems.
InSb n-channel enhancement mode MISFET grown by molecular beam epitaxy
- Author(s): T. Ashley ; A.B. Dean ; C.T. Elliott ; C.F. McConville ; C.R. Whitehouse
- Source: Electronics Letters, Volume 25, Issue 4, p. 289 –290
- DOI: 10.1049/el:19890201
- Type: Article
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InSb n-channel enhancement mode MISFETs have been fabricated in homoepitaxial material grown by molecular beam epitaxy. Silicon doping during growth of the epitaxial layers was used to form the source and drain junctions. The output characteristics are of the classical type, with a maximum gm of 12 mS/mm, corresponding to a surface electron mobility of 3–4 × 104cm2/Vs at liquid nitrogen temperature.
Concatenation of polarisation dispersion in single-mode fibres
- Author(s): F. Curti ; B. Daino ; Q. Mao ; F. Matera ; C.G. Someda
- Source: Electronics Letters, Volume 25, Issue 4, p. 290 –292
- DOI: 10.1049/el:19890202
- Type: Article
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The evolution of the differential group delay between the principal states of polarisation versus distance in a link composed of 12 fibres, each 2.2 km long, is studied experimentally with a colour centre laser at 1.5µm. The results of a simulation based on a theoretical model are in agreement with the measurements.
Exact computation of two-port noise parameters
- Author(s): G.I. Vasilescu ; G. Alquie ; M. Krim
- Source: Electronics Letters, Volume 25, Issue 4, p. 292 –293
- DOI: 10.1049/el:19890203
- Type: Article
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A new procedure to determine the noise parameters of a linear two-port from a set of experimental data is introduced. It consists in directly solving a system of four nonlinear equations instead of using a least-squares fit or casting the original equations in a form that is linear with respect to the four noise parameters. The proposed symbolic solution provides insight in error analysis. This method is compared with Minimax optimisation performed on an experimental set of noise figures measured for nine different source admittances.
Soft error-trapping decoding of cyclic codes
- Author(s): V.C. DaRocha
- Source: Electronics Letters, Volume 25, Issue 4, p. 293 –294
- DOI: 10.1049/el:19890204
- Type: Article
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An error-trapping (ET) decoder is described which effectively uses softly-quantised demodulator output levels as an integral part of the decoding process. This soft ET decoder operates on multilevel symbols, which belong to a Galois field and represent the quantised demodulator output levels of a communication system. The procedure differs from other approaches to soft-decision decoding which employ conventional hard-decision decoders where, as separate items, the digit reliability measures are used in an ad-hoc fashion.
Small astigmatism, high power and low noise 0.78 µm self-aligned lasers
- Author(s): I. Komazaki ; M. Uchida ; S. Ishikawa ; M. Nido ; K. Endo ; K. Hara ; T. Yuasa
- Source: Electronics Letters, Volume 25, Issue 4, p. 294 –296
- DOI: 10.1049/el:19890205
- Type: Article
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0.78 µm self-aligned AlGaAs lasers have been developed for optical disc recording. The lasers have shown a small astigmatism (<3 µm), low-noise characteristics (RIN < −126 dB/Hz at 3 mW) and stable 30 mW operation (over 1800 hours at 50°C).
Erratum: High-gain GaInP/GaAs heterojunction phototransistor utilising guard-ring structure
- Author(s): J.K. Twynam ; P.A. Claxton ; R.C. Woods ; D.R. Wight
- Source: Electronics Letters, Volume 25, Issue 4, page: 296 –296
- DOI: 10.1049/el:19890206
- Type: Article
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