Online ISSN
1350-911X
Print ISSN
0013-5194
Electronics Letters
Volume 26, Issue 13, 21 June 1990
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Volume 26, Issue 13
21 June 1990
Three phase high frequency DC-DC convertor
- Author(s): R. Rabinovici
- Source: Electronics Letters, Volume 26, Issue 13, p. 829 –830
- DOI: 10.1049/el:19900543
- Type: Article
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A three phase system in a high frequency DC-DC convertor is proposed. Potential advantages of such an implementation include smaller magnetic parts, much lower output and input ripple, higher transformer utilisation factor and efficiency, and lower AC voltages for the same DC output voltage. There are also some disadvantages. More switchers and rectifying diodes are required. A three phase transformer and master oscillator at high frequencies are also necessary.
New waveguide-to-coplanar waveguide transition for centimetre and millimetre wave applications
- Author(s): G.C. Dalman
- Source: Electronics Letters, Volume 26, Issue 13, p. 830 –831
- DOI: 10.1049/el:19900544
- Type: Article
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A novel waveguide-to-coplanar waveguide adaptor useful for microwave and millimetre wave applications is described. The feasibility of the adaptor has been established through tests performed on X-band and Ka-band prototype structures. Satisfactory operation above 100 GHz is anticipated.
Selective silicon epitaxial growth by LPCVD using silane
- Author(s): G.J. Parker and C.M.K. Starbuck
- Source: Electronics Letters, Volume 26, Issue 13, p. 831 –832
- DOI: 10.1049/el:19900545
- Type: Article
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Chlorine chemistry can have adverse effects on LPCVD systems and components. Results demonstrating the growth of selective silicon epitaxial layers in excess of 0.7 μn thickness showing excellent uniformity and selectivity without the use of HCl are presented.
Demonstration of a 1×2 multichannel grating cavity laser for wavelength division multiplexing (WDM) applications
- Author(s): I.H. White ; K.O. Nyairo ; P.A. Kirkby ; C.J. Armistead
- Source: Electronics Letters, Volume 26, Issue 13, p. 832 –834
- DOI: 10.1049/el:19900546
- Type: Article
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A new form of diode laser source for wavelength-division multiplexing (WDM) applications is reported. The source has been designed to operate in systems requiring wavelength separations between channels of more than 1 nm and provides exact control of channel separation with low crosstalk. Simultaneous multiwavelength generation is also possible.
LiNbO3 acoustic plate mode sensor for dilute ionic solutions
- Author(s): F. Josse ; D.T. Haworth ; U.R. Kelkar ; Z.A. Shana
- Source: Electronics Letters, Volume 26, Issue 13, p. 834 –835
- DOI: 10.1049/el:19900547
- Type: Article
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Experimental studies of ZX-LiNbO3 acoustic plate modes as detectors for dilute electrolyte or metal ion solutions are reported which indicate a strong acousto-ionic interaction. The results show an increase in sensitivity and resolution by more than two orders of magnitude compared with previously reported acoustic wave sensors.
Photoluminescence spectroscopy measurement of elastic strain in heteroepitaxial GaAs films
- Author(s): T.P. Humphreys ; R.J. Nemanich ; K. Das ; N.R. Parikh ; J.B. Posthill
- Source: Electronics Letters, Volume 26, Issue 13, p. 835 –837
- DOI: 10.1049/el:19900548
- Type: Article
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GaAs films have been grown on silicon and various insulating substrates. These include silicon-on-sapphire, silicon with a buried implanted oxide, and single crystal sapphire. Quantitative comparison of the respective measured shifts in the dominant photoluminescence peaks (7K) indicates that the GaAs layers deposited on silicon-on-sapphire substrates that have been microstructurally upgraded by the double solid-phase epitaxy process are strain-free.
New impedance transforming rat-race hybrid ring
- Author(s): H.R. Mgombelo ; H.O. Ali ; M.M. Kissaka
- Source: Electronics Letters, Volume 26, Issue 13, p. 837 –839
- DOI: 10.1049/el:19900549
- Type: Article
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A new impedance transforming rat-race hybrid ring is realised by modifying an impedance transforming Wilkinson power divider.1 The performance characteristics have been computed for different impedance transformation ratios over a 100% bandwidth.
636 nm room temperature CW operation by heterobarrier blocking structure InGaAlP laser diodes
- Author(s): K. Itaya ; M. Ishikawa ; Y. Uematsu
- Source: Electronics Letters, Volume 26, Issue 13, p. 839 –840
- DOI: 10.1049/el:19900550
- Type: Article
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636 nm room temperature CW operation has been achieved by heterobarrier blocking structure InGaAlP laser diodes with a quaternary active layer. This structure was fabricated by two-step metal-organic chemical vapour deposition. The threshold current was 102 mA at 20°C and CW operation of 3mW was attained at up to 48°C.
Transmissive quasidistributed optical fibre sensing scheme for two-state sensors
- Author(s): A. Prewett
- Source: Electronics Letters, Volume 26, Issue 13, p. 840 –842
- DOI: 10.1049/el:19900551
- Type: Article
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A coherence multiplexed sensing scheme for two-state sensors is demonstrated. The system uses conventional white light interferometry to resolve polarisation mode cross-coupling sites along a highly birefringent bus fibre. The limitations of such a system, based on a multi-longitudinal mode laser diode source, are identified.
CAD-oriented cavity model for rectangular patches
- Author(s): D. Thouroude ; M. Himdi ; J.P. Daniel
- Source: Electronics Letters, Volume 26, Issue 13, p. 842 –844
- DOI: 10.1049/el:19900552
- Type: Article
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A cavity model well suited for computed-aided design is presented. The patch antenna is described by geometrical and electrical parameters. Using a cavity model, input impedance as a function of frequency is then calculated with a fast computer program implemented on a PC. Resonant resistance and resonant frequency are deduced.
Evaluation of currents in the fA range
- Author(s): P. Girard and P. Nouet
- Source: Electronics Letters, Volume 26, Issue 13, p. 844 –846
- DOI: 10.1049/el:19900553
- Type: Article
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A method allowing the determination of very low currents is presented. It consists in the association of an amplification element to a leaky device on the same silicon chip. A theoretical approach is given, the possibilities of this method are deduced, and experimental results are reported and discussed.
Anisotype, enhancement-mode, heterojunction gate field-effect transistors
- Author(s): C.L. Lin ; H.H. Wieder ; R. Zuleeg
- Source: Electronics Letters, Volume 26, Issue 13, p. 846 –847
- DOI: 10.1049/el:19900554
- Type: Article
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Anisotype, p+-GaAs/n-In0.15Ga0.85As heterojunction field-effect transistors, grown by molecular beam epitaxy and fabricated by a self-aligned process, have been investigated for digital logic applications. Peak transconductance of 411 mS/mm and a K-value of 292 mA/V2/mm were obtained for an enhancement-mode device with gate length of 1 μm. Preliminary analysis of a nonisolated device leads to a cut off frequency of 17.5 GHz.
SPICE simulation of quasi-resonant zero-current-switching DC-DC convertors
- Author(s): S. Ben-Yaakov ; D. Edry ; Y. Amran ; O. Shimony
- Source: Electronics Letters, Volume 26, Issue 13, p. 847 –849
- DOI: 10.1049/el:19900555
- Type: Article
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A simple, topology-independent method is proposed for simulating the responses of open and closed-loop quasiresonant DC-DC convertors operating in the zero-current-switching mode (ZCS-QRC). The method hinges on the substitution of the resonant network and switch assembly, fundamental in the realisation of such systems, by an equivalent circuit which represents its average behaviour. This permits simulation by a general-purpose electronic circuit simulator such as SPICE. The proposed approach is demonstrated by presenting the simulation results of a buck-boost convertor.
Enhancement of Faraday rotation in a fibre Fabry-Perot cavity
- Author(s): J. Stone ; R.M. Jopson ; L.W. Stulz ; S.J. Licht
- Source: Electronics Letters, Volume 26, Issue 13, p. 849 –851
- DOI: 10.1049/el:19900556
- Type: Article
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The enhancement of Faraday rotation in a rare-earth iron garnet plate inside a fibre Fabry-Perot resonator is demonstrated. An enhancement factor of seven is obtained with a resonator finesse of 10.
Iterative learning control of completely irregular plants with initial impulsive action
- Author(s): B. Porter and S.S. Mohamed
- Source: Electronics Letters, Volume 26, Issue 13, p. 851 –852
- DOI: 10.1049/el:19900557
- Type: Article
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–852
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Iterative learning controllers with initial impulsive action are characterised for a class of completely irregular linear timeinvariant plants. These theoretical results are illustrated by the presentation of numerical results for the iterative learning control of a second-order plant that is completely irregular, and therefore cannot be controlled directly using previous methods.
Simple extraction method for mobility parameters in Si-MOSFETs at 77 K
- Author(s): J.I. Lee ; M.B. Lee ; K.N. Kang ; K.O. Park
- Source: Electronics Letters, Volume 26, Issue 13, p. 852 –853
- DOI: 10.1049/el:19900558
- Type: Article
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–853
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A simple technique for the extraction of low field mobility μ0 and linear and quadratic coefficients α and β in Si-MOSFETs at 77 K is presented. From measurement of the drain currents and transconductances of the devices one can determine the parameters. The method is applied to long channel and short channel LDD MOSFETs.
Selective plasma etching of Si from GaAs-on-Si wafers for microwave via-hole formation
- Author(s): G.W. Turner ; C.L. Chen ; M.K. Connors ; L.J. Mahoney ; W.L. McGilvary
- Source: Electronics Letters, Volume 26, Issue 13, p. 854 –855
- DOI: 10.1049/el:19900559
- Type: Article
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–855
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Selective plasma etching has been used to form via holes in GaAs-on-Si wafers that are superior to the holes formed by conventional methods in semi-insulating GaAs wafers. The plasma etching technique has a variety of potential microwave device applications.
Traffic levels supportable by telepoint systems using current cordless telephone technology
- Author(s): J.E. Button
- Source: Electronics Letters, Volume 26, Issue 13, p. 855 –856
- DOI: 10.1049/el:19900560
- Type: Article
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The traffic carrying capability of Telepoint systems utilising CEPT CT1 and CT2/CAI systems is predicted using computer simulation. This shows that a CT2/CAI based Telepoint system is capable of supporting significantly more traffic than a system based on CT1.
Recognising partially occluded objects by rigid body relaxation matching
- Author(s): T. Lee ; R. Li ; S.H. Kong
- Source: Electronics Letters, Volume 26, Issue 13, p. 856 –858
- DOI: 10.1049/el:19900561
- Type: Article
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By representing 3D objects by a rigid-body model (RBM), application of probabilistic relaxation to satisfy the embedded spatial constraints in the RBMs for recognising partially occluded objects using range data was investigated. A computer simulated data set was used to illustrate the effectiveness of the proposed procedure.
Phase-locking of laser diodes
- Author(s): H.R. Telle and H. Li
- Source: Electronics Letters, Volume 26, Issue 13, p. 858 –859
- DOI: 10.1049/el:19900562
- Type: Article
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–859
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Phase-locking of two optically prestablised laser diodes is realised by controlling the injection current and the feedback cavity resonance frequency of one of the lasers.
Crest factor minimisation in FDM PSK systems
- Author(s): B.T. Tan and Y.K. Some
- Source: Electronics Letters, Volume 26, Issue 13, p. 859 –861
- DOI: 10.1049/el:19900563
- Type: Article
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A scheme to reduce the crest factors of FDM PSK systems is proposed. Results from the proposed scheme compare favourably with the lowest possible crest factors.
Computational improvement in the calculation of the natural log of a square matrix
- Author(s): D.L. Cooper and S. Bingulac
- Source: Electronics Letters, Volume 26, Issue 13, p. 861 –862
- DOI: 10.1049/el:19900564
- Type: Article
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A computational improvement on an algorithm previously derived for the calculation of the natural log of a square matrix is presented, allowing a more general use of the algorithm. This algorithm is useful in estimating the state-space model of a continuous-time multivariable system from data obtained with a discrete-time model.
Two-dimensional electron gas base hot electron transistor
- Author(s): P. Matthews ; M.J. Kelly ; V.J. Law ; D.G. Hasko ; M. Pepper ; H. Ahmed ; D.C. Peacock ; J.E.F. Frost ; D.A. Ritchie ; G.A.C. Jones
- Source: Electronics Letters, Volume 26, Issue 13, p. 862 –864
- DOI: 10.1049/el:19900565
- Type: Article
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We present data on a large area hot-electron transistor in the GaAs/AlGaAs materials system that uses a two-dimensional electron gas for its base. When the feature size is scaled from the present 100 μm (approximately) to 1 μm, we predict useful transistor action at 100 GHz.
Outage probability analysis for microcell mobile radio systems with cochannel interferers in Rician/Rayleigh fading environment
- Author(s): Y.-D. Yao and A.U.H. Sheikh
- Source: Electronics Letters, Volume 26, Issue 13, p. 864 –866
- DOI: 10.1049/el:19900566
- Type: Article
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A microcell mobile radio system where the desired signal within a cell experiences Rician fading while interfering signals from cochannel cells experience Rayleigh fading is studied. This model is named a Rician/Rayleigh fading environment. Expressions of outage probabilities are presented for the mobile radio system in the Rician/Rayleigh fading environment.
Effect of n-type dopant species on the compensating effects of oxygen implantation in GaAs
- Author(s): N.J. Whitehead and B.J. Sealy
- Source: Electronics Letters, Volume 26, Issue 13, p. 866 –869
- DOI: 10.1049/el:19900567
- Type: Article
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The effect of n-type dopant species on the compensating behaviour of oxygen implants has been studied using Hall effect and C/V profiling techniques. Stronger compensation is retained if silicon rather than selenium is used to form the n-type layer. The compensation has been separated into damage related and oxygen atom related mechanisms, both of which are shown to be n-type dopant sensitive. The dopant sensitivity of the damage related compensation is tentatively described by assuming that localised regions of stoichiometric imbalance are introduced by the oxygen implantation, which promotes activation on the arsenic site. However, the reason for the dopant sensitivity of the oxygen atom related mechanism remains unclear.
Multichannel FSK transmission experiment at 565 Mbit/s using tunable three-electrode DFB laserss
- Author(s): N. Flaarønning ; J.O. Frorud ; M. Sotom ; G. Vendrôme ; G. da Loura ; J.M. Gabriagues ; J. Jacquet ; D. Leclerc ; J. Benoit
- Source: Electronics Letters, Volume 26, Issue 13, p. 869 –870
- DOI: 10.1049/el:19900568
- Type: Article
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The first four-channel 565 Mbit/s FSK transmission experiment at 1.53 μm is reported based on tunable three-electrode DFB lasers. −44 dBm receiver sensitivity and 5.5 GHz minimum channel spacing have been measured for 10−9 bit error rate.
Spectrum stability of a broadband 1060 nm Nd-doped fibre laser
- Author(s): F. Fesler ; M. Digonnet ; K. Liu ; B.Y. Kim ; H.J. Shaw
- Source: Electronics Letters, Volume 26, Issue 13, p. 870 –872
- DOI: 10.1049/el:19900569
- Type: Article
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Measurements of the spectrum dependence on temperature of a broadband diode-pumped fibre laser, targeted as a source for high grade fibre gyroscopes is reported. With the proper choice of pump wavelength, the temperature of this source need only be stabilised to 0.1°C for a mean laser wavelength stability of 1 ppm, compared to 0.003°C for a superluminescent diode source.
Fabrication and properties of large core, high NA, high Nd3+ content multimode optical fibres for temperature sensor applications
- Author(s): P.L. Scrivener ; P.D. Maton ; A.P. Appleyard ; E.J. Tarbox
- Source: Electronics Letters, Volume 26, Issue 13, p. 872 –873
- DOI: 10.1049/el:19900570
- Type: Article
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The fabrication and properties of 0.28 NA, 100/140 μm, multimode alumino-silicate fibre doped with 7.5 wt% Nd3+ is reported. These fibres show excellent potential for use as the sensing element in intrinsic optical fibre temperature sensors.
Wavelength stability of Nd3+-doped fibre fluorescent sources
- Author(s): P.R. Morkel ; E.M. Taylor ; J.E. Townsend ; D.N. Payne
- Source: Electronics Letters, Volume 26, Issue 13, p. 873 –875
- DOI: 10.1049/el:19900571
- Type: Article
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The output spectrum of Nd3+-doped fibre fluorescent sources is found to vary with pump wavelength which presents a problem for their use in optical fibre gyroscopes. Different silica-based fibre types show different dependences. It is shown that single-mode fibre fabricated from phosphate glass exhibits a spectrum which is extremely stable.
Buried rectangular GaInAs/InP corrugations of 70 nm pitch fabricated by OMVPE
- Author(s): T. Yamamoto ; Y. Miyamoto ; M. Ogawa ; E. Inamura ; K. Furuya
- Source: Electronics Letters, Volume 26, Issue 13, p. 875 –876
- DOI: 10.1049/el:19900572
- Type: Article
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Rectangular InP corrugations of 70 nm pitch and 40 nm depth were buried with GaInAs by OMVPE so as to preserve the rectangular shape. A low regrowth temperature and short heating up time in an atmosphere of high PH3 partial pressure are effective in the suppression of thermal deformation during regrowth.
Polarisation-maintaining fibre using a novel glass system
- Author(s): Y.T. Ko ; D.J. Digiovanni ; J.B. MacChesney ; J.R. Simpson
- Source: Electronics Letters, Volume 26, Issue 13, p. 876 –878
- DOI: 10.1049/el:19900573
- Type: Article
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A new glass dopant system, AOPO4 is used to form the stress-producing regions of a polarisation-maintaining optical fibre. The advantages of this glass system are that it can match match the refractive index of silica and does not have a fundamental absorption peak near the optical frequencies of interest, allowing it to be placed in close proximity to the fibre core to optimise birefringence. This material was used for the cladding of a preform, which was then flattened to yield an elliptical fibre upon drawing. This fibre demonstrated an extinction ratio at 1.3 μm of 42.5 dB for a 10 m length and 22 dB for 500 m for h = 1.3 × 10−5m−1. The beat length at λ = 0.488 μm was about 9 mm, corresponding to a modal birefringence of 5.3 × 10−5.
Simple multiplexer circuit for CMOS VLSI
- Author(s): S. Summerfield
- Source: Electronics Letters, Volume 26, Issue 13, p. 878 –879
- DOI: 10.1049/el:19900574
- Type: Article
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A simple 2:1 selector follows from the complementary properties of CMOS transistors. It leads to compact circuits such as a four-transistor XOR gate and a six-transistor static latch. A comparison with conventional circuit techniques, through the design and simulation of ripple-carry adders shows the circuits to be slower but much smaller.
CMOS triode transconductor with high dynamic range
- Author(s): B. Stefanelli and A. Kaiser
- Source: Electronics Letters, Volume 26, Issue 13, p. 880 –881
- DOI: 10.1049/el:19900575
- Type: Article
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A CMOS triode transconductor using a novel bias scheme is described. The bias circuit is based on an auxiliary transistor and ensures optimum bias conditions over the entire tuning range. This makes it possible to design low-noise integrated continuous-time filters with a wide tuning range.
New complementary pairs of sequences
- Author(s): S.Z. Budišin
- Source: Electronics Letters, Volume 26, Issue 13, p. 881 –883
- DOI: 10.1049/el:19900576
- Type: Article
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881
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A general method for construction of polyphase complementary pairs of sequences of length 2N is presented. This method is based on the recursive algorithms introduced by Golay for binary sequences and by Sivaswamy for polyphase sequences. A modification of the proposed algorithm can generate multilevel and complex sequences of magnitude different from unity. The proposed sequences are suitable for radar applications where complementary sequences different from the known binary sequences are required.
Efficient CW operation of a 2.9 μm Ho3+-doped fluorozirconate fibre laser pumped at 640 nm
- Author(s): L. Wetenkamp
- Source: Electronics Letters, Volume 26, Issue 13, p. 883 –884
- DOI: 10.1049/el:19900577
- Type: Article
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CW laser operation of a H03+-doped ZBLAN multimode fibre, emitting within the range 2.83–2.95 μm, was achieved by optical pumping at 640 nm, as a result of excited state absorption of the pump. Thresholds were approximately 65 mW absorbed power for a 90% output coupler and approximately 290 mW with reflection of the fibre end only. Slope efficiencies and maximum output powers were 2.9% and 12.6 mW, and 4.4% and 10.2 mW, respectively.
n-AlInAs/(InAs)3(GaAs)1 superlattice modulation-doped field effect transistor grown by molecular beam epitaxy
- Author(s): N. Nishiyama ; H. Yana ; S. Nakajima ; H. Hayashi
- Source: Electronics Letters, Volume 26, Issue 13, p. 885 –886
- DOI: 10.1049/el:19900578
- Type: Article
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A pseudomorphic modulation-doped field effect transistor (MODFET) using a (InAs)3(GaAs)1 superlattice as a channel layer has been successfully demonstrated. The device was grown by molecular beam epitaxy. The MODFET with 0.85 μm gate length exhibits maximum external DC transconductance and current gain cut-off frequency of 475 mS/mm and 28.5 GHz, respectively.
Directional-coupler-based planar concentrator networks
- Author(s): A. Jajszczyk
- Source: Electronics Letters, Volume 26, Issue 13, p. 886 –887
- DOI: 10.1049/el:19900579
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Optical networks, with concentration, composed of directional couplers are studied. We propose a modification of N-stage planar networks. The appropriate procedure to obtain concentration in such networks is given and savings in directional couplers and switching stages are discussed.
Implementation of integration of Walsh series by flowgraphs
- Author(s): M. Ohkita and Y. Kobayashi
- Source: Electronics Letters, Volume 26, Issue 13, p. 887 –889
- DOI: 10.1049/el:19900580
- Type: Article
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It is shown that termwise integration of a series comprising sequency (Walsh) ordered Walsh functions (WFs) can be implemented by the flowgraphs similar to that for the sequency-ordered Walsh transform.
Low-threshold GRIN-SCH AlGaInAs 1.55 μm quantum well buried ridge structure lasers grown by molecular beam epitaxy
- Author(s): C. Kazmierski ; M. Blez ; M. Quillec ; M. Allovon ; B. Sermage
- Source: Electronics Letters, Volume 26, Issue 13, p. 889 –891
- DOI: 10.1049/el:19900581
- Type: Article
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Two-step MBE/MOVPE epitaxy buried ridge stripe GRIN-SCH quantum well lasers having MBE active structure consisting of Gain As quantum wells and an AlGaInAs continuously graded confinement region have been fabricated and characterised. Devices operating at 1.55μm wavelength with a low CW threshold current of 18.7 mA have been demonstrated. This figure is the best result obtained in the AlGaInAs system. A study of the intrinsic optical response of the active layer showed a very fast decay of the resonance oscillations. A good figure of the optical bandwidth move-out rate 3-9GHzmW−1/2has been observed.
Simple-iterative method for pattern synthesis using nonuniformly spaced arrays
- Author(s): M.A. Hassan
- Source: Electronics Letters, Volume 26, Issue 13, p. 891 –892
- DOI: 10.1049/el:19900582
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A simple and easy to use method for synthesising uniformly-excited linear broadside arrays through element position control is proposed. A single equation must be iteratively solved to obtain one of the interelement spacings. The others are deduced accordingly to a simple relation. The resulting separation between the array elements is optimum in the sense that a best fit is obtained between the synthesised pattern and the desired one.
Model minimisation for electron devices using simulated annealing in conjunction with parameter extraction
- Author(s): M.-K. Vai ; D. Ng ; S. Prasad
- Source: Electronics Letters, Volume 26, Issue 13, p. 892 –894
- DOI: 10.1049/el:19900583
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A modelling process which includes both model minimisation and parameter extraction is developed to obtain the best simulation speed while maintaining accuracy. The effectiveness of this approach is demonstrated by its application to the modelling of a transistor. Significant simulation time saving is observed and the simulation accuracy is adequately maintained.
Solution of Poisson equation in p-AlyGa1−yAs/p-Al0.45Ga0.55As/n-GaAs structures
- Author(s): S.C. Kwok
- Source: Electronics Letters, Volume 26, Issue 13, p. 894 –896
- DOI: 10.1049/el:19900584
- Type: Article
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The Poisson equation in a p-AlyGa1−yAs/p-Al0.45Ga0.55As/n-GaAs structures structure under reverse bias is solved analytically subject to ohmic contact boundary conditions. The solution takes into account the linear variation of the dielectric constant in the compositionally graded region. It is shown that the dielectric constant in the graded region can be approximated by an average dielectric constant with good accuracy in solving for the electrostatic field distribution and potential.
Analysis of coupling coefficient between two vertical cavity surface emitting lasers for two-dimensional phase-locked array
- Author(s): H.-J. Yoo ; J.R. Hayes ; Y.-S. Kwon
- Source: Electronics Letters, Volume 26, Issue 13, p. 896 –897
- DOI: 10.1049/el:19900585
- Type: Article
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The coupling coefficient between two adjacent circular vertical cavity surface emitting lasers having an InGaAs strained quantum well active region (λg = 1μm) and a GaAs cavity has been analysed. The analysis was performed for Al0.3Ga0.7As cladding (n = 3.325) and air (n = 1). In order to obtain a coupling coeficient of 10−3, which is known for the stable phase locking of array, the laser separation must beless than 0.25μm for the lasers of radius 0.4μm with air cladding and be less than 0.72μm for the lasers of radius 1.2μm with Al0.3Ga0.7As cladding. Various structures of two-dimensional phase-locked arrays, such as periodic, circular and concentric circular arrays, can be realised by bringing lasers into close proximity of which value can be obtained from the analysis.
Digital signature scheme based on error-correcting codes
- Author(s): W. Xinmei
- Source: Electronics Letters, Volume 26, Issue 13, p. 898 –899
- DOI: 10.1049/el:19900586
- Type: Article
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A new digital signature scheme based on error-correcting codes is proposed. The security of this scheme relies on the difficulty of factoring large matrices and the properties of error-correcting codes. The features of our scheme are that the ciphertext for a given message M is not repeated and errors in the ciphertext received can be detected and corrected. If this scheme is combined with the McEliece publickey cryptosystem, we obtain a scheme that can not only sign, but also encipher, messages.
Carry-save adders for computing the product AB modulo N
- Author(s): C.K. Koç and C.Y. Hung
- Source: Electronics Letters, Volume 26, Issue 13, p. 899 –900
- DOI: 10.1049/el:19900587
- Type: Article
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The letter describes a new algorithm for modulator multiplication using carry-save adders. The proposed algorithm is based on the sign-estimation technique. A carry-save adder structure consisting of three rows of n + 3 simple 1-bit adder cells, and two copies of 3-bit carry look-ahead logic can be used to implement a single step of the algorithm. A completely pipelined array for modular multiplication designed by cascading n carry-save adders performs modulator multiplication at the clock rate.
Comparison of WDM coupler technologies for use in erbium doped fibre amplifier systems
- Author(s): A. Lord ; I.J. Wilkinson ; A. Ellis ; D. Cleland ; R.A. Garnham ; W.A. Stallard
- Source: Electronics Letters, Volume 26, Issue 13, p. 900 –901
- DOI: 10.1049/el:19900588
- Type: Article
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Fused-tapered and interference filter technology are compared for specific application in 1480 nm pumped erbium doped fibre amplifiers as WDM multiplexers for signal and pump light. In particular, the temperature, polarisation and wavelength dependence of the coupling ratio are measured and the implications for amplifier gain variability are discussed.
DC B–H curve tracer with error correction and constant measuring and drawing speed using microcomputer
- Author(s): S. Kusui ; M. Kosukegawa ; M. Inoue
- Source: Electronics Letters, Volume 26, Issue 13, p. 902 –903
- DOI: 10.1049/el:19900589
- Type: Article
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A high precision DC B–H curve tracer is developed which uses microcomputer control. The error caused by the drift of DC amplifiers is automatically corrected and the difference between the starting and finishing points of the curve is automatically corrected to zero. The measuring and plotting interval along the curve can be constant. These are totally processed by the microcomputer.
Erbium-doped fluoride fibre optical amplifier operating around 2.75 μm
- Author(s): D. Ronarc'h ; J.Y. Allain ; M. Guibert ; M. Monerie ; H. Poignant
- Source: Electronics Letters, Volume 26, Issue 13, p. 903 –904
- DOI: 10.1049/el:19900590
- Type: Article
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An optical gain of 18.3 dB at a signal wavelength of 2.707 μm is obtained in an Er3+ doped fluorozirconate fibre pumped at 0.647 μm. The saturation power of the amplifier is estimated to be around 2 mW.
Computation of the right-inverse of G(D) and the left-inverse of Ht(D)
- Author(s): L.H.C. Lee
- Source: Electronics Letters, Volume 26, Issue 13, p. 904 –906
- DOI: 10.1049/el:19900591
- Type: Article
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Useful column and row operations are given for the computation of the right-inverse G−(D) of an k × n generator matrix G(D) and the left-inverse [H(D)]−1 of the transpose of an (n — k) × n parity-check matrix H(D). The methods are illustrated with two examples.
Modulated QMF filter banks with perfect reconstruction
- Author(s): H.S. Malvar
- Source: Electronics Letters, Volume 26, Issue 13, p. 906 –907
- DOI: 10.1049/el:19900592
- Type: Article
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Necessary and sufficient conditions for perfect reconstruction (PR) in a modulated filter bank are derived. It is shown that, for a bank of M filters of length L, PR can be obtained when L = 2KM, for any positive integer K, whereas previous results guaranteed PR only for K = 1.
Two dimensional grating surface emitting laser arrays with wide lateral extent
- Author(s): G.A. Evans ; N.W. Carlson ; D.P. Bour ; J.M. Hammer ; M. Lurie ; J.K. Butler ; R. Amantea ; S.K. Liew ; J.B. Kirk ; W.F. Reichert ; R.K. DeFreez ; D.J. Bossert
- Source: Electronics Letters, Volume 26, Issue 13, p. 907 –908
- DOI: 10.1049/el:19900593
- Type: Article
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Two dimensional grating-coupled surface-emitting laser arrays with as many as 250 ridge-guided elements in each gain section were fabricated. Four gain sections were operated simultaneously with a resulting aperture of 1.0 × 2.1 mm2.
Fuzzy intraframe smoothing of a noisy image
- Author(s): Q. Shen
- Source: Electronics Letters, Volume 26, Issue 13, p. 908 –910
- DOI: 10.1049/el:19900594
- Type: Article
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908
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A fuzzy model for the eight neighbours of a pixel within a noisy image is developed with a possibility distribution function. An optimal intraframe smoothing algorithm is presented based on this model and the maximum possibility criterion. It can be realised with a simple digital structure and suppresses heavy noise.
Optoelectronic synaptic connection circuit with variable analogue weights
- Author(s): H. Yonezu ; T. Himeno ; K. Kanamori ; K. Pak ; Y. Takano
- Source: Electronics Letters, Volume 26, Issue 13, p. 910 –912
- DOI: 10.1049/el:19900595
- Type: Article
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A basic optoelectronic circuit of an artificial synaptic connection was fabricated in which analogue weights were varied electrically. Circuit simplicity and low current level operation, necessary for a large scale OEIC, were realised.
Resonant frequency of wedge shaped microstrip antenna
- Author(s): R.K. Mishra and S.S. Pattnaik
- Source: Electronics Letters, Volume 26, Issue 13, p. 912 –913
- DOI: 10.1049/el:19900596
- Type: Article
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The small bandwidth of microstrip antennas still remains their major drawback and continues to be a major concern. One method used to improve the bandwidth is to make the patch on a wedgeshaped substrate. Only experimental observation on this has been reported. The present work is on a rectangular antenna, whose nonradiating edge is on a plane that intersects the ground plane with an angle, θ. An expression has been derived for the resonant frequency in the dominant mode. The theoretical findings are supported by experimental observation.
Low voltage InGaAs/InP multiple quantum well reflective Fabry-Perot modulator
- Author(s): A.J. Moseley ; J. Thompson ; M.Q. Kearley ; D.J. Robbins ; M.J. Goodwin
- Source: Electronics Letters, Volume 26, Issue 13, p. 913 –915
- DOI: 10.1049/el:19900597
- Type: Article
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The first low voltage, substrate access, reflective InGaAs/InP multi-quantum well modulator exploiting the enhanced performance obtainable through the use of an asymmetric Fabry-Perot cavity around the quantum well absorbing region is reported. This device utilises a low reflectivity AlInGaAs/InP multi-layer mirror (R~35%) on the substrate side of the quantum well region, and a high reflectivity metal mirror (R~95%) on the epitaxial side of the cavity. Devices have been fabricated which exhibit a reflectivity change of >30% and contrast ratio of 3 dB at 5 V bias, with a 1.8 dB insertion loss.
780 nm low threshold current laser fabricated by two-step, solid-phase Zn diffusion
- Author(s): A. Shima ; T. Kamizato ; A. Takami ; S. Karakida ; K. Isshiki ; H. Matsubara
- Source: Electronics Letters, Volume 26, Issue 13, p. 915 –916
- DOI: 10.1049/el:19900598
- Type: Article
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A Zn diffusion stripe laser is fabricated by the metalorganic chemical vapour deposition and the open-tube, two-step, solid-phase diffusion technique. The threshold current is 9.4 mA and the lasing wavelength is 780 nm at 20°C. The laser operates in the fundamental transverse mode and the astigmatic distance is less than 1 μm. The laser has operated for over 1000 h at 60°C with a power of 3 mW.
Fundamental limitation on large-signal modulation of semiconductor lasers and its implications for lightwave transmission
- Author(s): G.P. Agrawal
- Source: Electronics Letters, Volume 26, Issue 13, p. 916 –918
- DOI: 10.1049/el:19900599
- Type: Article
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The performance of single-mode semiconductor lasers under large signal modulation is found to be limited by intraband gain saturation occurring when the on-state output power becomes comparable to the saturation level. The main effect of intraband gain saturation is to increase the fall time associated with the optical pulse. At high bit rates the pulse stretches over several neighbouring bits, thereby affecting the system performance. In the case of 1.55 μm InGaAsP lasers operating at bit rates ∼ 10 Gbit/s intraband gain saturation limits the average power in the range ∼ 10–20 mW for an acceptable system performance.
Combined amplitude and polarisation shift keying optical coherent modulation
- Author(s): S. Benedetto and P. Poggiolini
- Source: Electronics Letters, Volume 26, Issue 13, p. 918 –919
- DOI: 10.1049/el:19900600
- Type: Article
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The letter proposes and analyses two coherent transmission schemes using combined amplitude and polarisation shift keying (CAPSK). The bit-error-rate results (with respect to shot and Gaussian receiver noise) show a performance very close to that of the best performing schemes known so far.
8 GHz full Nyquist HBT comparator
- Author(s): D. Selle ; D. Carisetti ; T. Ducourant ; P. Bertsch ; P. Boissenot
- Source: Electronics Letters, Volume 26, Issue 13, p. 919 –921
- DOI: 10.1049/el:19900601
- Type: Article
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A very high speed voltage comparator circuit implemented with self-aligned GaAlAs/GaAs heteroj unction bipolar transistors (HBTs) has been demonstrated. The 2 μm emitter width transistors have a current gain cut-off frequency of 30 GHz and a maximum oscillation frequency of 34.8 GHz. A full Nyquist test has been performed up to 8 GHz, the input sensitivity varying from 3 mV at 0.5 GHz to 30 mV at 8 GHz. The hysteresis measured under quasi-static conditions is as low as 0.5 mV.
Robust blind deconvolution algorithm: variance approximation and series decoupling
- Author(s): F. Zheng ; S. McLaughlin ; B. Mulgrew
- Source: Electronics Letters, Volume 26, Issue 13, p. 921 –923
- DOI: 10.1049/el:19900602
- Type: Article
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An alternative blind deconvolution algorithm for white-noise driven minimum phase systems is presented and verified by computer simulation. This algorithm uses a cost function based on a novel idea: variance approximation and series decoupling (VASD), and suggests that not all autocorrelation function values are necessary to implement blind deconvolution.
Time-division 8:1 multiplexing and demultiplexing system adapting 7B1C code operating at 5 Gbit/s
- Author(s): N. Yokota ; Y. Hakamata ; K. Takemoto
- Source: Electronics Letters, Volume 26, Issue 13, p. 923 –925
- DOI: 10.1049/el:19900603
- Type: Article
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Time-division 8:1 multiplexing which adapts 7B1C code and 1:8 demultiplexing which satisfies channel alignment using a feature of 7B1C code are described. This system operates at 5 Gbit/s using newly developed ICs employing GaAs technology.
Monolithic integration of an InGaAs/GaAs/AlGaAs strained layer SQW LED and GaAs MESFET using epitaxial lift-off
- Author(s): I. Polentier ; L. Buydens ; A. Ackaert ; P. Demeester ; P. van Daele ; F. Depestel ; D. Lootens ; R. Baets
- Source: Electronics Letters, Volume 26, Issue 13, p. 925 –927
- DOI: 10.1049/el:19900604
- Type: Article
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The successful realisation of a fully electrically interconnected optical and electronic device using the epitaxial lift-off technique is reported. The OEIC consists of a high output power InGaAs/GaAs/AlGaAs strained QW LED and a GaAS MESFET driver. The surface emitting LED shows an external quantum efficiency of 1.7%. The output/input ratio of the LED-FET combination was 54 μWV−1 sr−1.
Efficient Nd:MgO:LiNbO3 waveguide laser
- Author(s): E. Lallier ; J.P. Pocholle ; M. Papuchon ; M. de Micheli ; M.J. Li ; Q. He ; D.B Ostrowsky
- Source: Electronics Letters, Volume 26, Issue 13, p. 927 –928
- DOI: 10.1049/el:19900605
- Type: Article
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Efficient CW operation of a single mode Nd:MgO:LiNbO3 channel waveguide laser is reported. The absorbed pump power at threshold is 2.7 mW and the slope efficiency is 34%. With our available pump power the laser could emit up to 14 mW CW without exhibiting any photorefractive damage.
Finite-element analysis of chirowaveguides
- Author(s): J.A.M. Svedin
- Source: Electronics Letters, Volume 26, Issue 13, p. 928 –929
- DOI: 10.1049/el:19900606
- Type: Article
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A finite-element formulation for the modal analysis of chirowaveguides is described. It consistitutes a generalisation of the vector EH formulation, which has earlier been found to be without spurious nonphysical solutions. The validity of the suggested formulation is confirmed by comparing obtained dispersion relations for a circular chirowaveguide with corresponding exact solutions, the correspondence was found to be excellent.
IR photodetector with exclusion effect and self-filtering n+ layer
- Author(s): Z. Djuric ; V. Jovic ; M. Matic ; Z. Jaksic
- Source: Electronics Letters, Volume 26, Issue 13, p. 929 –931
- DOI: 10.1049/el:19900607
- Type: Article
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A ‘vertical’ exclusion homoepitaxial n+n structure for infrared photodetectors in nonequilibrium with certain advantages when comparison with ‘horizontal’ n+n structures is proposed. The exclusion effect was observed at 220 K in experimental InSb n+n structures fabricated by liquid phase epitaxy. It was not possible to utilise the benefits of the suppression of Auger recombination because of the low Shockley-Read lifetime in the substrate.
Wide angular aperture acousto-optic configurations in biaxial crystals
- Author(s): J.E.B. Oliveira and E.L. Adler
- Source: Electronics Letters, Volume 26, Issue 13, p. 931 –933
- DOI: 10.1049/el:19900608
- Type: Article
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A general formulation of acousto-optic (AO) diffraction is presented for predicting the Bragg angles of noncollinear wide-angular-aperture AO configurations in biaxial crystals. The Bragg angles are determined explicitly without resorting to any trial configuration.
1.53 μm DFB laser on semi-insulating InP substrate with very low threshold current
- Author(s): W. Thulke and S. Illek
- Source: Electronics Letters, Volume 26, Issue 13, p. 933 –934
- DOI: 10.1049/el:19900609
- Type: Article
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A novel GaInAsP DFB laser structure on a semi-insulating InP substrate is reported. A new contacting scheme is applied which allows both contacts to be placed on the wafer top while preserving the planar surface of the buried-heterostructure laser diode. CW threshold currents as low as7 mA have been measured at 25°C on 200 μm long devices. These are the lowest values reported for 1.5 μm DFB lasers on semi-insulating substrate.
Design of a hybrid receiver for the olympus spacecraft beacons
- Author(s): D.G. Sweeney and J.C. McKeeman
- Source: Electronics Letters, Volume 26, Issue 13, p. 934 –936
- DOI: 10.1049/el:19900610
- Type: Article
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The theory and design of a hybrid analogue/digital receiver which acquires and monitors the OLYMPUS satellite beacons is presented. The analogue portion of this receiver uses a frequency locked loop for signal tracking. A digital sampling detector operating at IF is used to obtain the I and Q outputs.
Improved current mode control technique for quantum series resonant convertors
- Author(s): J.H. Ko ; D.S. Oh ; M.J. Youn
- Source: Electronics Letters, Volume 26, Issue 13, p. 936 –937
- DOI: 10.1049/el:19900611
- Type: Article
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An improved current mode control technique capable of self adjusting the offset current is proposed to overcome the disadvantages of quantum series resonant convertors. Near optimum control patterns in view of the current ripple can be obtained without an average offset current. The continuous output voltage levels are also available.
Temperature dependence of bending loss in monomode optical fibres
- Author(s): R. Morgan ; J.S. Barton ; P.G. Harper ; J.D.C. Jones
- Source: Electronics Letters, Volume 26, Issue 13, p. 937 –939
- DOI: 10.1049/el:19900612
- Type: Article
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The temperature dependence of bending loss in monomode optical fibres is reported. The observations are explained on the basis of interference between the core guided mode and a ‘whispering gallery’ mode. Implications of this effect in the design of local light detectors and the realisation of fibre optic sensors are discussed.
Time-resolved chirp in mode-locked semiconductor lasers
- Author(s): A.J. Lowery
- Source: Electronics Letters, Volume 26, Issue 13, p. 939 –940
- DOI: 10.1049/el:19900613
- Type: Article
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Numerical simulations using the transmission-line laser model show that the instantaneous frequency of a 10 ps mode-locked pulse undergoes a rapid red-shift of 60 GHz during the first half of the pulse followed by a slow recovery of 10 GHz. Self-phase modulation is thought to cause this shift.
Surface emitting laser arrays with uniformly separated wavelengths
- Author(s): C.J. Chang-Hasnain ; M.W. Maeda ; N.G. Stoffel ; J.P. Harbison ; L.T. Florez ; J. Jewell
- Source: Electronics Letters, Volume 26, Issue 13, p. 940 –942
- DOI: 10.1049/el:19900614
- Type: Article
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A novel and simple scheme used to achieve a 2-D array of monolithic multiple wavelength lasers is reported. Uniformly separated wavelengths are emitted from an eight-element linear array and an 8 × 8 2-D array of surface emitting lasers in the 950 nm regime. The lasers all have nearly identical light against current characteristics.
Superposition technique for the generalised stochastic Petri net modelling of degradable systems
- Author(s): J. Hsieh and D.R. Ucci
- Source: Electronics Letters, Volume 26, Issue 13, p. 942 –944
- DOI: 10.1049/el:19900615
- Type: Article
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A superposition technique is presented for the solution of generalised stochastic Petri nets (GSPN) in which transition rates differ by orders of magnitude. The technique reduces the state space explosion problem. Examples demonstrate the effectiveness and accuracy of this approach.
Fast computational algorithm for transform coding
- Author(s): Y. Kato and T. Murakami
- Source: Electronics Letters, Volume 26, Issue 13, p. 944 –946
- DOI: 10.1049/el:19900616
- Type: Article
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A transform coding scheme has been widely used in the field of image data compression. A lot of computational power is required for the realtime operation. A new fast computational algorithm, pruned transform coding (PTC), which can reduce the computational complexity compared with the conventional transform coding is proposed. Excellent coding performance is demonstrated through a computer simulation.
Packaged 2×2 array of InGaAs/InP multiple quantum well modulators grown by double-sided epitaxy
- Author(s): M.A.Z. Rejman-Greene and E.G. Scott
- Source: Electronics Letters, Volume 26, Issue 13, p. 946 –948
- DOI: 10.1049/el:19900617
- Type: Article
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Epitaxial growth of InGaAs/InP MQW structures on both sides of an InP substrate is used to enhance the performance of planar optical modulators to 3.8 dB for −10 V change in bias. 2×2 arrays of such devices, operating at 1.51 μm, are realised by means of a novel packaging scheme.
High gain Er3+ -doped fibre amplifier pumped by 820nm GaAlAs laser diodes
- Author(s): K. Suzuki ; Y. Kimura ; M. Nakazawa
- Source: Electronics Letters, Volume 26, Issue 13, p. 948 –949
- DOI: 10.1049/el:19900618
- Type: Article
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An optical gain of 22 dB at 1.535 μm is obtained in an Er3+- doped fibre amplifier for a total pump power of 54 mW. The Er3+ doping concentration is 34 ppm, and the pumping source is GaAlAs laser diodes at 820 nm. By using an Er3+ fibre with a doping concentration of 390 ppm, the maximum gain is as high as 29.4 dB for a pump power of 83 mW.
275 GHz 3-mask integrated GaAs sampling circuit
- Author(s): R.Y. Yu ; M. Case ; M. Kamegawa ; M. Sundaram ; M.J.W. Rodwell ; A.W. Gossard
- Source: Electronics Letters, Volume 26, Issue 13, p. 949 –951
- DOI: 10.1049/el:19900619
- Type: Article
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A monolithic GaAs diode sampling head with 275 GHz ( −3dB) bandwidth gated by a nonlinear-transmission-line (NLTL) strobe pulse generator and fabricated using three masks at 3 μm resolution is reported. The sampling circuit step response, measured using a second NLTL as a testsignal, showed a l.9 ps (10–90%) convolved falltime and 24% peak to peak ringing.
2-MOSFET transresistor with extremely low distortion for output reaching supply voltages
- Author(s): Z. Wang
- Source: Electronics Letters, Volume 26, Issue 13, p. 951 –952
- DOI: 10.1049/el:19900620
- Type: Article
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Square-difference is a new and very attractive linearisation technique. It has been successfully used to implement large-signal MOS transconductors. A transresistor realised with only two MOS devices using the same technique is presented. A linearity error of less than ±0–5% for the output swing from supply voltage Vss to VDD is achieved.
Transmission line model analysis of arbitrary shape symmetrical patch antenna coupled with a director
- Author(s): G. Dubost and A. Zerguerras
- Source: Electronics Letters, Volume 26, Issue 13, p. 952 –954
- DOI: 10.1049/el:19900621
- Type: Article
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A quasi-TEM two coupled transmission line model is used to express the radiation admittance of an arbitrary shape symmetric patch antenna coupled with a director. In the particular case of the circular shape the theoretical results are in good agreement with experiments.
Rigorous closed-form expressions for the surface wave loss of printed antennas
- Author(s): D.M. Pozar
- Source: Electronics Letters, Volume 26, Issue 13, p. 954 –956
- DOI: 10.1049/el:19900622
- Type: Article
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Rigorous closed-form expressions are presented for the radiation efficiency of an arbitrary printed antenna element. These results are an improvement over those which have previously appeared.
Asymptotic method in prediction of E plane radiation pattern of rectangular microstrip patch antennas on finite ground
- Author(s): P. Vaudon ; A. Reineix ; B. Jecko
- Source: Electronics Letters, Volume 26, Issue 13, p. 956 –957
- DOI: 10.1049/el:19900623
- Type: Article
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Limited ground effect on the radiation pattern of microstrip antenna is already known. A simple method to predict E plane radiation, except in the neighbourhood of the geometrical optical boundary that is 8 = 90°, is presented. A very good value of the field on this boundary is given: it means that the leaving pattern could be constructed by interpolation. Good agreement is obtained between the theoretical results and the experimental measurements in the validity domain of the method.
Low-phase-error offset-compensated switched-capacitor integrator
- Author(s): W-H. Ki and G.C. Temes
- Source: Electronics Letters, Volume 26, Issue 13, p. 957 –959
- DOI: 10.1049/el:19900624
- Type: Article
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A modification of the offset-compensated switched-capacitor integrator is described. The resulting circuit has a reduced delay and low gain distortion. It also retains the simplicity and low phase errors of earlier schemes.
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- Type: Article
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54 Gbit/s OOK transmission using single-mode VCSEL up to 2.2 km MMF
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