Online ISSN
1350-911X
Print ISSN
0013-5194
Electronics Letters
Volume 24, Issue 16, 4 August 1988
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Volume 24, Issue 16
4 August 1988
Low-Threshold Patterned quantum well lasers grown by molecular beam epitaxy
- Author(s): E. Kapon ; C.P. Yun ; J.P. Harbison ; L.T. Florez ; N.G. Stoffel
- Source: Electronics Letters, Volume 24, Issue 16, p. 985 –986
- DOI: 10.1049/el:19880670
- Type: Article
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GaAs/AlGaAs patterned quantum well lasers were grown by molecular beam epitaxy on grooved substrates. The carrier confinement and the real-index waveguiding in these lasers rely on lateral thickness variations in the quantum well active layer. Very low threshold currents, as low as l.8mA for uncoated devices at room temperature, with 63% differential efficiency have been obtained.
Enhanced throughput in packet radio channels with shadowing
- Author(s): R. Prasad and J.C. Arnbak
- Source: Electronics Letters, Volume 24, Issue 16, p. 986 –988
- DOI: 10.1049/el:19880671
- Type: Article
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The throughput of a slotted-ALOHA radio channel with lognormal shadowing has been derived. Uncorrelated packet shadowing is shown to assist receiver capture, so that the throughput always exceeds the throughput obtained in both ‘ideal’ channels and channels with pure Rayleigh fading.
Miniature packaged external-cavity semiconductor laser with 50 GHz continuous electrical tuning range
- Author(s): J. Mellis ; S.A. Al-Chalabi ; K.H. Cameron ; R. Wyatt ; J.C. Regnault ; W.J. Devlin ; M.C. Brain
- Source: Electronics Letters, Volume 24, Issue 16, p. 988 –989
- DOI: 10.1049/el:19880672
- Type: Article
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Miniature, packaged, grating-external-cavity lasers have been developed for use in PSK. and DPSK coherent transmission systems at 1.5μm. The outside dimensions of the package are 30 × 30 × 50 mm and the optical cavity length is nominally 30 mm, resulting in a spectral linewidth < 100 kHz. The lasing wavelength is mechanically adjustable over the range 1510–1560 nm and electrically tunable over a range of 0.8 nm. With appropriate control of the grating piezos, a continuous (hop-free) tuning range of 50 GHz (0.4 nm) can be obtained.
Simple determination of coupling coefficient in DFB waveguide structures
- Author(s): P. Brosson ; C. Artigue ; B. Fernier ; D. Leclerc ; J. Jacquet ; J. Benoit
- Source: Electronics Letters, Volume 24, Issue 16, p. 990 –991
- DOI: 10.1049/el:19880673
- Type: Article
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A simple method allowing the determination of the coupling coefficient Kq of DFB waveguide structures of arbitrary type, number of layers and grating profile is proposed. The method relies on effective index determination and the fast Fourier transform of the actual grating profile. The method has been validated by comparison with the measured stopband width of liquid phase epitaxy (LPE) and gas source molecular beam epitaxy (GSMBE) grown 1.5μm DFB lasers.
Execution of the NEC2 electromagnetic moment method code on the Inmos T800 Transputer
- Author(s): J.J. le Roux ; P.J. Bakkes ; J.J. du plessis ; J.H. Cloete
- Source: Electronics Letters, Volume 24, Issue 16, p. 991 –992
- DOI: 10.1049/el:19880674
- Type: Article
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The NEC2 electromagnetic moment method code has been successfully transferred into the personal computer environment. The Inmos T800 Transputer was used to execute the code. The analysis of a 12 element log-periodic antenna was used as a benchmark to compare execution times. Execution on the Transputer was 1.5 times faster than on a DEC microVAX computer, and comparable to the speed of a DEC VAX785 computer.
High-temperature CW operation of planar buried-ridge structure lasers at λ = 1.5μm
- Author(s): W. Thulke and A. Zach
- Source: Electronics Letters, Volume 24, Issue 16, p. 992 –993
- DOI: 10.1049/el:19880675
- Type: Article
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GaInAsP/InP-PBRS lasers emitting at l.5μm have been fabricated by multiple liquid-phase epitaxy. Effective current confinement is achieved without current blocking layers. CW threshold current is as low as 9 mA at 25°C. Output powers per facet of up to 10mW at 80°C and 3.5 mW at 100°C are obtained. The maximum operation temperature of 110°C is the highest value yet achieved with this type of laser at 1.5μm.
Acknowledgment schemes for window flow control in a quasi-M/D/1 cut-through switching network
- Author(s): Y.J. Cho and C.K. Un
- Source: Electronics Letters, Volume 24, Issue 16, p. 993 –995
- DOI: 10.1049/el:19880676
- Type: Article
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Window flow control in a quasi-M/D/1 cut-through switching network with noisy channel is discussed. Two acknowledgment schemes for window edge control at the entry node are proposed, and their various properties investigated.
Gainas pin photodiode/GaAs preamplifier photoreceiver for gigabit-rate communications systems using flip-chip bonding techniques
- Author(s): M. Makiuchi ; H. Hamaguchi ; T. Kumai ; O. Aoki ; Y. Oikawa ; O. Wada
- Source: Electronics Letters, Volume 24, Issue 16, p. 995 –996
- DOI: 10.1049/el:19880677
- Type: Article
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We report on an integrated photoreceiver using a flip-chip bonding technique. The integrated photoreceiver consists of a back-illuminated GaInAs/InP pin photodiode with a small junction area and a GaAs high-impedance preamplifier having a two-stage amplifier. The quantum efficiency and the cut-off frequency of the pin photodiode were 81% and 19 GHz. This photoreceiver exhibited good practical performance characteristics, including a minimum detectable power of −29.8dBm at 1 Gbit/s, and −26.9 dBm at 2 Gbit/s.
Accurate two-dimensional approach for capacitance calculation in microcoplanar mes transmission lines
- Author(s): A. Benghalia ; M. Ahmadpanah ; H. Baudrand
- Source: Electronics Letters, Volume 24, Issue 16, p. 996 –998
- DOI: 10.1049/el:19880678
- Type: Article
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A new two-dimensional approach is proposed for the analysis of microcoplanar metal-semiconductor structures, where the depletion layer capacitance is calculated accurately after an exact determination of its boundary. The Green function, which is used to invert the Laplacian operator, is obtained by means of a conformal mapping technique to take into account the real position of the ground planes. The method constitutes a solid base for a further study of slowwave MES coplanar waveguides and, with a small change in the boundary conditions, it can be extended to the analysis of MESFET propagating structures.
Low-loss bends in planar optical ridge waveguides
- Author(s): E.C.M. Pennings ; G.H. Manhoudt ; M.K. Smit
- Source: Electronics Letters, Volume 24, Issue 16, p. 998 –999
- DOI: 10.1049/el:19880679
- Type: Article
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Bending losses lower than 0.7 dB for 90° bend sections with radii of curvature as small as 75μm were measured on silicon-based Al2O3 ridge waveguides with SiO2 cladding layers at a wavelength of 632.8 nm. These values, which are close to the calculated values, are the lowest thus far reported.
New sensitivity-enhancing scheme for a fibre-optic interferometer utilising two optical loops
- Author(s): K. Arai ; K. Hayashi ; K. Iiyama ; Y. Ida ; T. Mori
- Source: Electronics Letters, Volume 24, Issue 16, p. 1000 –1001
- DOI: 10.1049/el:19880680
- Type: Article
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To improve the sensitivity or dynamic range of fibre-optic interferometer systems a new scheme utilising two optical loops is presented. The validity of the scheme is also experimentally confirmed by a tentative bulk-optic configuration.
Origin of residual semiconductor-laser linewidth in high-power limit
- Author(s): K. Kikuchi
- Source: Electronics Letters, Volume 24, Issue 16, p. 1001 –1002
- DOI: 10.1049/el:19880681
- Type: Article
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The FM noise spectrum and the spectral width of semiconductor lasers are measured in the high-power state up to 20 mW. The FM noise spectrum consists of the white noise and the 1/f noise. The spectral density of the white noise is suppressed by the increase in the output power, whereas that of the l/f noise is kept constant. This fact means that the residual linewidth in the high-power limit is caused by the l/f noise rather than the white noise.
Frequency-locked diode laser for interferometric sensing systems
- Author(s): D.J. Webb ; J.D.C. Jones ; D.A. Jackson
- Source: Electronics Letters, Volume 24, Issue 16, p. 1002 –1004
- DOI: 10.1049/el:19880682
- Type: Article
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Interferometric sensors for slowly varying measurands, such as temperature or pressure, require a long term frequency stability of the source. We describe a system for frequency locking a laser diode to an atomic transition in a hollow cathode lamp using the optogalvanic effect.
Resonant frequency analysis of dielectric ring resonators
- Author(s): D.-L. Paul ; M. Habibi ; P. Gelin
- Source: Electronics Letters, Volume 24, Issue 16, p. 1004 –1005
- DOI: 10.1049/el:19880683
- Type: Article
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The mode-matching technique is applied to guided and continuous spectra to derive the resonant frequencies of the high-order azimuthal modes of dielectric ring resonators. The numerical results of this field theory analysis are in close agreement with the measurements in the X-band.
Measurement of intermodulation products generated by structural components
- Author(s): P.L. Lui ; A.D. Rawlins ; D.W. Watts
- Source: Electronics Letters, Volume 24, Issue 16, p. 1005 –1007
- DOI: 10.1049/el:19880684
- Type: Article
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A computer-controlled measurement system is described, developed to investigate intermodulation products generated by nonlinear junctions in antenna towers, mast support and mounting components. Results are presented which suggest that certain mechanical features, commonly encountered in some components, should be regarded as more likely to be associated with this cause of interference.
Stray-free second-order circuit for correction of sample-and-hold amplitude distortion in switched-capacitor filters
- Author(s): S.P. Sharma ; J.T. Taylor ; D.G. Haigh
- Source: Electronics Letters, Volume 24, Issue 16, p. 1007 –1008
- DOI: 10.1049/el:19880685
- Type: Article
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A second-order stray-free circuit for the correction of amplitude deviations arising from the sample-and-hold effect in switched capacitor filters is proposed. The new circuit removes many of the shortcomings of a previously published first-order correction circuit, having improved correction accuracy together with reduced capacitance spread and total capacitance.
Performance of shot-noise limited optical communications in presence of intersymbol interference
- Author(s): F.D. Garber and D.P. Michal
- Source: Electronics Letters, Volume 24, Issue 16, p. 1008 –1010
- DOI: 10.1049/el:19880686
- Type: Article
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Results are presented for the average error probability of shot-noise limited on-off-keying optical communications in the presence of intersymbol interference. An expression for a near-optimum detection threshold is given and the results of evaluating the probability of error for this threshold are shown.
Electrical and microstructural characterisation of an ultrathin silicon interlayer used in a silicon dioxide/germanium-based MIS structure
- Author(s): G.G. Fountain ; R.A. Rudder ; S.V. Hattangady ; D.J. Vitkavage ; R.J. Markunas ; J.B. Posthill
- Source: Electronics Letters, Volume 24, Issue 16, p. 1010 –1011
- DOI: 10.1049/el:19880687
- Type: Article
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Ultrathin (1.0 nm) Si layers have been deposited on Ge(100) surfaces using remote plasma-enhanced chemical vapour deposition (RPECVD) at 350°C followed by in situ RPECVD deposition of an SiO2 insulating layer. Microstructural data from transmission electron microscopy along with elemental analysis from X-ray photoelectron spectroscopy and ion scattering spectroscopy indicate that the Si layer is present and may be pseudomorphic in nature. The formation of a Si/Ge heterojunction prior to oxide deposition minimises the formation of Ge oxides and thus controls the chemical nature of the Ge surface. Indeed, dramatic improvements in the electrical interfacial characteristics were observed in the SiO2/Si/Ge over the SiO2/Ge MIS structure.
Mode field radius definitions for arbitrary planar single-mode optical waveguides and their relations to splice loss and propagation constant
- Author(s): A.H. Liang and C.C. Fan
- Source: Electronics Letters, Volume 24, Issue 16, p. 1011 –1013
- DOI: 10.1049/el:19880688
- Type: Article
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Root-mean-square and Laplacian mode field radius (MFR) definitions for planar single-mode optical waveguides (PSMOW) with arbitrary index profile are proposed based on the second moment of the near-field (NF) and far-field (FF) distributions. Expressions of these definitions in both NF and FF, as well as their simple relations to the propagation constant and splice loss between two identical waveguides, are derived.
High reliability planar-type GaInAs/InP heterostructure avalanche photodiodes
- Author(s): Y. Matsushima ; S. Akiba ; Y. Kushiro
- Source: Electronics Letters, Volume 24, Issue 16, p. 1013 –1014
- DOI: 10.1049/el:19880689
- Type: Article
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High-temperature, long-term life tests of GaInAs/InP heterostructure avalanche photodiodes have been carried out to establish criteria for high reliability photodetectors in 1.55μm-wavelength optical submarine cable systems. A failure rate of less than 0.2 FIT at 10°C was predicted for the first time with an activation energy of 0.7 eV.
Bistable operation of 0.8μm GaInAsP/AaAs lasers
- Author(s): J. Ishikawa ; T. Ito ; N.S. Takahashi ; S. Kurita
- Source: Electronics Letters, Volume 24, Issue 16, p. 1014 –1016
- DOI: 10.1049/el:19880690
- Type: Article
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Quaternary GaInAsP prepared on GaAs is a very promising material for optoelectronic devices in alternating AlGaAs/GaAs systems. We report bistable operation in stripe geometry GaInAsP/GaAs DH lasers with gain region and absorbing region in the laser resonator. A hysteresis loop is observed in the I/L curve under pulsed operation at room temperature.
Stability of differential multipass processes
- Author(s): S. Foda and P. Agathoklis
- Source: Electronics Letters, Volume 24, Issue 16, p. 1016 –1017
- DOI: 10.1049/el:19880691
- Type: Article
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Edwards' notion of stability along the pass for differential multipass processes is shown to be equivalent to what is known as pointwise asymptotic stability for delay differential systems.
Efficient power combining quasi-optic oscillator
- Author(s): P.G. Frayne and C.J. Riddaway
- Source: Electronics Letters, Volume 24, Issue 16, p. 1017 –1018
- DOI: 10.1049/el:19880692
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Slot coupled self-oscillating patch antennas are used as efficient source modules for a quasi-optic power combining cavity. Optimum coupling between the antenna and the device, and also the need for slot coupling between the source module and the cavity, is discussed.
Fused couplers function in a broad range of wavelength
- Author(s): Zheng Xue-Heng
- Source: Electronics Letters, Volume 24, Issue 16, p. 1018 –1019
- DOI: 10.1049/el:19880693
- Type: Article
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There is a specific V value around which a fused coupler can function as a directional coupler in a broad range of wavelengths. This V value is too small to be achieved by a conventional fused coupler.
Detectivity of high-gain GaAs photoconductive detectors
- Author(s): M. Constant ; D. Lefebvre ; L. Boussekey ; D. Decoster ; J.P. Vilcot
- Source: Electronics Letters, Volume 24, Issue 16, p. 1019 –1021
- DOI: 10.1049/el:19880694
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Detailed studies of noise properties and dynamic responsivity of GaAs planar photoconductors have been made in the 1 Hz –100 kHz frequency range. The results obtained lead to the determination of the specific detectivity of the devices, which in turn is compared to that of Si photodiodes.
Capacitance of a small tubular antenna
- Author(s): J.P. Casey and R. Bansal
- Source: Electronics Letters, Volume 24, Issue 16, p. 1021 –1022
- DOI: 10.1049/el:19880695
- Type: Article
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The input capacitance of an electrically small tubular monopole antenna above a perfectly conducting ground is computed using a modified expression for the capacitance of a coplanar stripline. The calculated results are compared with measured data.
CMOS compatible, self-biased bipolar transistor aimed at detecting maximum temperature in a silicon integrated circuit
- Author(s): M. Bafleur ; J. Buxo ; G. Sarrabayrouse ; J. Millan ; S. Hidalgo
- Source: Electronics Letters, Volume 24, Issue 16, p. 1022 –1024
- DOI: 10.1049/el:19880696
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A new bipolar device, fully CMOS compatible, that properly detects and amplifies the leakage current of a reverse-biased bulk junction is presented. The amplification factor is the current gain hFE of the bipolar transistor which is maximised and independent of all spurious and less reproducible surface and space-charge recombination mechanisms.
Optical receiver with third-order capacitive current-current feedback
- Author(s): R.F.M. van den Brink
- Source: Electronics Letters, Volume 24, Issue 16, p. 1024 –1025
- DOI: 10.1049/el:19880697
- Type: Article
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A 500 MHz optical receiver front-end with third-order overall current-current feedback has been realised. The capacitive feedback loop combines the high-bandwidth performance and the large dynamic range of a transimpedance receiver with the low noise performance of a high-impedance receiver.
SC circuit for very large and accurate time constant integrators with low capacitance ratios
- Author(s): G. Espinosa Flores-Verdad and F. Montecchi
- Source: Electronics Letters, Volume 24, Issue 16, p. 1025 –1027
- DOI: 10.1049/el:19880698
- Type: Article
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A switched capacitor active integrator which realises long time constant values with low capacitance ratios is presented. The basic circuit implements a parasitic-insensitive capacitive charge division, which allows for accurate control of the equivalent time constant. The offset of the operational amplifier is reduced via a correlated-double-sampling operation, and the effect of the finite gain of the operational amplifier is also reduced with respect to classic integrators when a modified topology is used.
High-speed accurate CMOS comparator
- Author(s): M. Steyaert and V. Comino
- Source: Electronics Letters, Volume 24, Issue 16, p. 1027 –1028
- DOI: 10.1049/el:19880699
- Type: Article
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A high-speed CMOS comparator for A/D convertors is discussed. The circuit has high resolution (better than 5 mV) in combination with high speed (clock frequencies up to 50 MHz). The advantage of the proposed structure is that no clock feedthrough is injected to the input, only one switch in a symmetrical structure is used and the effect of any current biasing on the comparator speed has been reduced.
High-performance MESFETs in MOCVD-grown gallium arsenide on silicon
- Author(s): D.J. Warner ; R.R. Bradley ; T.B. Joyce ; R.J.M. Griffiths
- Source: Electronics Letters, Volume 24, Issue 16, p. 1029 –1030
- DOI: 10.1049/el:19880700
- Type: Article
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The use of MOCVD for growing device quality GaAs on silicon material has not been widely reported. This letter describes an MOCVD growth process that has allowed GaAs MESFETs to be fabricated with transconductances as high as 185 mS/mm with an operating yield of greater than 78%. The structural stability of the grown layers was good with no peeling of the GaAs from the silicon substrate during the scribing and breaking of the wafer into individual device chips.
Optical tristability including spectral bistability using an inhomogeneously excited multielectrode DFB LD
- Author(s): M. Jinno ; M. Koga ; T. Matsumoto
- Source: Electronics Letters, Volume 24, Issue 16, p. 1030 –1031
- DOI: 10.1049/el:19880701
- Type: Article
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Optical tristability, including spectral bistability, controlled either electrically or optically has been observed in a multielectrode DFB LD with a saturable absorber. A number of preliminary applications as optical logic gates (AND, OR, INVERT, NAND, NOR, and XOR) and optical memories are demonstrated experimentally.
First SiC dynistor
- Author(s): V.A. Dmitriev ; M.E. Levinshtein ; S.N. Vainshtein ; V.E. Chelnokov
- Source: Electronics Letters, Volume 24, Issue 16, p. 1031 –1033
- DOI: 10.1049/el:19880702
- Type: Article
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A four-layer dynistor has been made from SiC for the first time. Switching voltage is in the range from 30–50 V and switching time is about 10−8 s. The structure has been fabricated with a modified liquid-phase epitaxy (LPE).
Natural error coding for phonetically encoded speech messages
- Author(s): E.D. Chesmore
- Source: Electronics Letters, Volume 24, Issue 16, p. 1033 –1034
- DOI: 10.1049/el:19880703
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Preliminary outlines for the exploitation of natural redundancy in phonetically encoded speech messages are introduced. The techniques are specific to the Votrax SC-01A speech synthesiser but can be applied to any phoneme or allophone based devices.
Ultra-thin-channelled GaAs MESFET with double-δ-doped layers
- Author(s): A. Ishibashi ; K. Funato ; Y. Mori
- Source: Electronics Letters, Volume 24, Issue 16, p. 1034 –1035
- DOI: 10.1049/el:19880704
- Type: Article
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GaAs MESFETs with double-δ-doped layers have been fabricated with electron-beam-induced resist. The FET is made with the δ-doped channel embedded as shallow as 70 ̇ from the surface, and shows an intrinsic transconductance of 400 mS/mm for a gate length of about 1500 ̇.
Interference and long-loop phase-lock receivers
- Author(s): B.N. Biswas ; S. Sarkar ; S. Chatterjee
- Source: Electronics Letters, Volume 24, Issue 16, p. 1035 –1037
- DOI: 10.1049/el:19880705
- Type: Article
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Based upon a simple concept, the phenomenon of falselocking is described and the locking range characteristics of a long-loop phase-locked receiver exposed to a signal contaminated with a cochannel interfering tone are presented. Also, the limiting condition of synchronisation in such a situation is obtained.
GaAs MESFETs, ring oscillators and divide-by-2 integrated circuits fabricated on MBE grown GaAs on Si substrates
- Author(s): F. Ren ; N. Chand ; P. Garbinski ; S.J. Pearton ; C.S. Wu ; L.D. Urbanek ; T. Fullowan ; N. Shah ; M.D. Feuer
- Source: Electronics Letters, Volume 24, Issue 16, p. 1037 –1039
- DOI: 10.1049/el:19880706
- Type: Article
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Using a very thin layer of GaAs (2.1 μm) on Si, we have fabricated GaAs MESFETs, 19 stage ring oscillators, and divide-by-2 frequency dividers with good yield. The MESFETs exhibited a maximum gm of 153 mS/mm. The DCFL 19 stage ring oscillators had a minimum propagation delay of 52ps/gate at a power dissipation of 1.3 mW/gate with a yield of 40%. The divide-by-2 circuits performed the frequency dividing operation up to 1.8 GHz.
Characteristics of acoustic echo cancellers using sub-band sampling and decorrelation methods
- Author(s): H. Yasukawa ; I. Furukawa ; Y. Ishiyama
- Source: Electronics Letters, Volume 24, Issue 16, p. 1039 –1040
- DOI: 10.1049/el:19880707
- Type: Article
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An acoustic sub-band echo canceller offering high speech quality has been implemented. Echo cancellation in excess of 40 dB was obtained over the 7 kHz frequency band in the hardware with 4000-tap FIR filters. It was confirmed using a decorrelation algorithm that the convergence speed for coloured signals was about three times faster than the conventional NLMS algorithm.
Multiprocessor based system design
- Author(s): A. Delavari
- Source: Electronics Letters, Volume 24, Issue 16, p. 1041 –1042
- DOI: 10.1049/el:19880708
- Type: Article
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The letter discusses the design of a marketable and powerful microcomputer with maximum efficiency while keeping the cost and parts count low. The two main processors in the system are capable of operating in parallel and independently, thus resulting in high system throughput and speed. Colour graphics, floppy disks and hard disks are considered in this design.
Modes of phase-locked diode-laser arrays of closely spaced antiguides
- Author(s): D. Botez and G. Peterson
- Source: Electronics Letters, Volume 24, Issue 16, p. 1042 –1044
- DOI: 10.1049/el:19880709
- Type: Article
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A uniform, ten-element array of closely spaced (1–3 μm) realindex depressions (antiguides), with lasing suppressed in the positive-index regions between antiguides, supports ten lasing eigenmodes. Near-field amplitude profiles and radiation losses are presented and discussed. Radiation losses of inphase and out-of-phase array modes are negligible in comparison with the radiation loss of one array element taken separately.
Error correction capabilities of BCH codes with interleaving in Rayleigh fading channel
- Author(s): H. Suda and T. Miki
- Source: Electronics Letters, Volume 24, Issue 16, p. 1044 –1045
- DOI: 10.1049/el:19880710
- Type: Article
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Error correction capabilities of several BCH codes with different code lengths are investigated for a Rayleigh fading channel where burst bit errors occur frequently. The decoded BERs are compared under the same delay time condition for bit interleaving. Error sequences obtained from laboratory experiment are used for GMSK BER calculations. The results show that difference in the effects of code lengths on error correction capabilities is almost negligible under the slow fading with short delay time (short interleaving size) conditions.
1.5 μm multiple-quantum-well distributed feedback laser diodes grown on corrugated InP by MOVPE
- Author(s): M. Kitamura ; S. Takano ; N. Henmi ; T. Sasaki ; H. Yamada ; Y. Shinohara ; H. Hasumi ; I. Mito
- Source: Electronics Letters, Volume 24, Issue 16, p. 1045 –1046
- DOI: 10.1049/el:19880711
- Type: Article
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1.5 μm band GaInAs multiple-quantum-well distributed feedback laser diodes have been successfully fabricated on InP grating substrates by metalorganic vapour phase epitaxy for the first time. Extremely low chirp single-longitudinal-mode operation at 2.4 Gbit/s RZ modulation has been realised.
Low-drive-voltage, low-loss AlGaAs/GaAs 2 × 2 switch
- Author(s): C. Wüthrich ; J. Faist ; W. Baer ; F.K. Reinhart
- Source: Electronics Letters, Volume 24, Issue 16, p. 1047 –1048
- DOI: 10.1049/el:19880712
- Type: Article
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The letter reports the realisation of a 2 × 2 switch using a Mach-Zehnder interferometer with tunable coupler sections. The structure is based on a GaAs-AlGaAs double heterostructure with SnO2-doped In2O3 electrodes. At a wavelength of 1.15 μm, this device is characterised by a low switching voltage of 7.5 V and a low loss of 4 dB/cm. A high extinction ratio of 20 dB can be achieved.
Frequency-locking of a 1.5μm DFB laser to an atomic krypton line using optogalvanic effect
- Author(s): Y.C. Chung and C.B. Roxlo
- Source: Electronics Letters, Volume 24, Issue 16, p. 1048 –1049
- DOI: 10.1049/el:19880713
- Type: Article
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The frequency of a GaInAsP DFB laser has been locked to the 2p10-3d3 transition of krypton atoms at 1.5339 μm using the optogalvanic effect. The absolute frequency stability was estimated to be better than 4 MHz by using a frequency discriminator which is independent from the frequency-locking servo loop.
Comparison of optical reflection tolerance between conventional and λ/4-shifted DFB lasers in a 2.4 Gbit/s system
- Author(s): H. Nakano ; S. Sasaki ; S. Tsuji ; N. Chinone ; M. Maeda
- Source: Electronics Letters, Volume 24, Issue 16, p. 1049 –1051
- DOI: 10.1049/el:19880714
- Type: Article
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Effects of optical reflection on transmission characteristics with conventional fibre (1.3μm zero dispersion) are examined using 1.55μm conventional and λ/4-shifted DFB lasers. It is shown for the first time that λ/4-shifted DFB lasers are superior to conventional ones in transmission performance with optical reflection. BER floor levels of λ/4-shifted DFB lasers are lower than those of conventional ones, and do not change for the reflection level of PC-type optical connector.
Multibit oversampled Σ-Δ A/D convertor with digital error correction
- Author(s): L.E. Larson ; T. Cataltepe ; G.C. Temes
- Source: Electronics Letters, Volume 24, Issue 16, p. 1051 –1052
- DOI: 10.1049/el:19880715
- Type: Article
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A new architecture is presented for a multibit oversampled Σ-Δ analogue/digital convertor (ADC). A novel digital correction scheme is employed to enhance the overall resolution without requiring increased precision of the analogue components.
Effect of channel spacing in an optical two-channel DPSK transmission system with optical amplifiers
- Author(s): G. Grosskopf and R. Ludwig
- Source: Electronics Letters, Volume 24, Issue 16, p. 1052 –1054
- DOI: 10.1049/el:19880716
- Type: Article
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In a two-channel 560 Mbit/s DPSK system with optical broadband amplifiers the effect of channel spacing is investigated. The main crosstalk mechanism is independent of the amplifiers. It is caused by the spectral overlap of the two channels. No additional crosstalk due to four-wave mixing in the amplifier is found.
Photochromic dynamics and nonlinear transmission at modulated CW blue/green wavelengths in germanosilicate optical fibres
- Author(s): L.J. Poyntz-Wright and P.St.J. Russell
- Source: Electronics Letters, Volume 24, Issue 16, p. 1054 –1055
- DOI: 10.1049/el:19880717
- Type: Article
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Photochromic dynamics in germanosilicate fibres at quasi- CW blue/green wavelengths are investigated using sinusoidally modulated Ar+ laser light. The induced loss has both transient and permanent features, and gives rise to strongly nonlinear transmission.
Handling isochronous and non-isochronous traffic in local area networks
- Author(s): A. Pattavina
- Source: Electronics Letters, Volume 24, Issue 16, p. 1055 –1057
- DOI: 10.1049/el:19880718
- Type: Article
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A token ring network is described that integrates isochronous and non-isochronous services at the medium access layer. It guarantees an upper bound on the transport delay of isochronous information units, together with a lower bound and a fair allocation of the bandwidth for non-isochronous traffic.
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