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Online ISSN 1350-911X Print ISSN 0013-5194

Electronics Letters

Volume 27, Issue 15, 18 July 1991

Volumes & issues:

Volume 27, Issue 15

18 July 1991

Synchronisation circuit for addition of two asynchronously changing digital values in digital motor control circuits
  • Author(s): G.M. Brown  and  B. Szabados
  • Source: Electronics Letters, Volume 27, Issue 15, p. 1313 –1314
  • DOI:  10.1049/el:19910825
  • Type: Article
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  • p. 1313 –1314 (2)
    Phased-based digital motor control circuits often require the addition of two asynchronously changing digital values, corresponding typically to the rotor angle and electrical field angle of the stator. When one angle is increasing and the other is decreasing, their sum is not monotonic and can lead to errors in subsequent circuits that rely on the edge transitions of the least significant bit of this sum. A simple circuit is described which removes these transition errors and provides a ‘synchronous’ monotonic output.
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10 Gbit/s D flipflop using AlInAs/InGaAs HBTs
Point-matching method for reduction of anomalous radiation of log-periodic dipole array
  • Author(s): M.A. Hassan ; A. Al Jabri ; K. Al-Hakbani
  • Source: Electronics Letters, Volume 27, Issue 15, p. 1315 –1317
  • DOI:  10.1049/el:19910827
  • Type: Article
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  • p. 1315 –1317 (3)
    A point matching method is developed for the evaluation of the performance of the log-periodic dipole antenna (LPDA). Based on this method, the anomalous behaviour of the LPDA is studied and found to be improved at an optimum spacing factor and by selecting a small dipole length to diameter ratio; that is, an LPDA, operating over a given frequency band, must possess an optimum dimension that gives a pattern with eliminated anomalous backlobe peaks.
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Broadband branchline coupler for S band
  • Author(s): D.K. Paul ; P. Gardner ; B.Y. Prasetyo
  • Source: Electronics Letters, Volume 27, Issue 15, p. 1318 –1319
  • DOI:  10.1049/el:19910828
  • Type: Article
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  • p. 1318 –1319 (2)
    The design of an S-band, broadband, microstrip 3 dB, 90° branchline coupler is described and measured results for a prototype version are given. The design uses broadbanding stubs and three branches, with the central branch split into two or twice the characteristic impedance and separated by half wavelength transmission lines. This is a new technique to improve the bandwidth, of which a theoretical account was given by Mayer. Measured results for the prototype coupler show return loss greater than 17 dB and isolation greater than 16.5 dB, over a percentage bandwidth of 45%.
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Planar 1/8 splitter in glass by photoresist masked silver film ion exchange
  • Author(s): P. Pöyhönen ; S. Honkanen ; A. Tervonen ; M. Tahkokorpi ; J. Albert
  • Source: Electronics Letters, Volume 27, Issue 15, p. 1319 –1320
  • DOI:  10.1049/el:19910829
  • Type: Article
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  • p. 1319 –1320 (2)
    Fabrication of singlemode glass waveguide devices by silver film ion exchange with standard photoresist as a mask for the ion exchange is proposed. The process uses the advantages of the silver film ion exchange and the simple and accurate patterning when photoresist is used directly as a mask. As a component example, a singlemode 1/8 power splitter is fabricated and measured.
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Balanced directional loop receiving antenna
Error correction technique for multivalued MOS memory
Selftuning robot control laws
Semiconductor lasers fabricated by selective area epitaxy
  • Author(s): Y.L. Wang ; H. Temkin ; R.A. Hamm ; R.D. Yadvish ; D. Ritter ; L.H. Harriott ; M.B. Panish
  • Source: Electronics Letters, Volume 27, Issue 15, p. 1324 –1326
  • DOI:  10.1049/el:19910833
  • Type: Article
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  • p. 1324 –1326 (3)
    For the first time, semiconductor lasers grown entirely by selective area epitaxy are reported. The lasers were formed by in situ processing techniques and metal organic molecular beam epitaxy (MOMBE). A 50 Å thick layer of Si deposited on the InP substrate was used as a mask for both the selective growth and etching. Laser stripes, 6 μm wide, were delineated by a focused Ga-ion beam and transferred into the substrate by Cl2 etching. These steps were performed in the vacuum chambers attached to the MBE machine. Separate confinement heterostructure GaInAsP/InP lasers were grown selectively in the stripes. The resulting devices emit at 1.3 μm and show threshold currents of 40 mA.
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Direction finding in multipath environment using method of alternating projection
Degenerate four wave mixing in polydiacetylene waveguides
Multiple fault detection using single-fault tests
GaAs/AlGaAs dynamic random access memory cell
Perfect energy efficient sequences
  • Author(s): L. Bömer  and  M. Antweiler
  • Source: Electronics Letters, Volume 27, Issue 15, p. 1332 –1334
  • DOI:  10.1049/el:19910838
  • Type: Article
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  • p. 1332 –1334 (3)
    Time discrete sequences are termed perfect if their periodic autocorrelation function sidelobes are zero. Such sequences have constant magnitude spectra in the Fourier domain. An iteration scheme is introduced for optimising the energy efficiency of perfect real valued sequences. Perfect real valued sequences are synthesised in two steps. In the first step perfect sequences are generated in the Fourier domain by combining a constant magnitude spectrum with a suitable phase spectrum. In the second step phase values are modified by an iteration scheme such that the energy efficiency of the resulting perfect sequences is increased.
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Sporadic partitions of binomial coefficients
Variable-ratio, polarisation-insensitive, 3×3 fused biconical tapered couplers
Optimum germanium profile for SiGe base HBTs
  • Author(s): S.S. Winterton ; B.M. Manning ; D.J. Walkey ; N.G. Tarr
  • Source: Electronics Letters, Volume 27, Issue 15, p. 1337 –1338
  • DOI:  10.1049/el:19910841
  • Type: Article
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  • p. 1337 –1338 (2)
    The thermal stability of an SiGe base HBT is closely related to the integrated Ge content in the base. It is therefore appropriate to consider what form the Ge profile should take to minimise the base transit time τB for a given total Ge content. It is shown that a linear increase in Ge content from the base-emitter to the base-collector junction is required to minimise τB.
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BiCMOS operational amplifier with precise and stable DC gain for high-frequency switched capacitor circuits
  • Author(s): A. Baschirotto ; R. Alini ; R. Castello
  • Source: Electronics Letters, Volume 27, Issue 15, p. 1338 –1340
  • DOI:  10.1049/el:19910842
  • Type: Article
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  • p. 1338 –1340 (3)
    A novel approach in the design of high-frequency switched capacitor (SC) circuits is presented. It is based on the use of simple and fast amplifiers with low but precisely controlled gain value. The effect of the precisely known and stable opamp gain is compensated for by changing the capacitor values during the synthesis of the SC cell. An example of an opamp with these features and the synthesis of a biquadratic filter based on this approach are given.
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Comment: Design of symmetrical polylithic crystal filters
Higher order modes in dielectric resonators
  • Author(s): N. Loechel
  • Source: Electronics Letters, Volume 27, Issue 15, p. 1340 –1342
  • DOI:  10.1049/el:19910844
  • Type: Article
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  • p. 1340 –1342 (3)
    Higher order modes excited in oversized dielectric resonators are investigated using an expansion in terms of orthogonal eigenfunctions. Radiation and material losses are taken into account. The calculated results are in excellent agreement with measurements. Different modes are easily identified by plots showing fields and energy distribution. Novel mode charts helpful for resonator design are presented. Tradeoffs between mode separation and quality factor are discussed.
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Polymer channel waveguides with low loss at 1.3 μm
Experimental study of SAW quartz cuts with low sensitivity to dynamical thermal effects
Realisation of voltage-mode biquads using CCIIs
Vector dark spatial solitons
  • Author(s): Y. Chen
  • Source: Electronics Letters, Volume 27, Issue 15, p. 1346 –1348
  • DOI:  10.1049/el:19910848
  • Type: Article
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  • p. 1346 –1348 (3)
    The dark spatial solution of TM type is shown to exist in a uniform selfdefocussing nonlinear medium in the range of the beam effective index neff from 0.82n0 to n0 of the linear refractive index of the medium. This contrasts with the dark spatial soliton of TE type which exists over all the possible values of neff ranging from 0 to n0. The field profile of this TM dark wave is also found to depend on the beam effective index, deviating from the hyperbolic tanh function of TE type with decreasing neff.
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Relation of CLSS algorithm to KT and MUSIC methods
  • Author(s): X. Yang  and  M.H. Er
  • Source: Electronics Letters, Volume 27, Issue 15, p. 1348 –1350
  • DOI:  10.1049/el:19910849
  • Type: Article
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  • p. 1348 –1350 (3)
    The relation of the constrained least square subspace (CLSS) algorithm, which was proposed for high resolution array processing previously, to the more classic subspace approaches of MUSIC and KT is shown. The MUSIC and KT algorithms are shown to be special cases of the proposed constrained least square subspace approach. This provides further insight into the new algorithm. Additional simulation results are also included to illustrate the performance of the various algorithms.
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Traffic mixes on broadband ATM link
Application of nicollian-reisman model to negative point-to-plane corona oxidation of silicon
New neural network for pattern recognition
Modelling spatially correlated K-distributed clutter
  • Author(s): B.C. Armstrong  and  H.D. Griffiths
  • Source: Electronics Letters, Volume 27, Issue 15, p. 1355 –1356
  • DOI:  10.1049/el:19910853
  • Type: Article
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  • p. 1355 –1356 (2)
    K-distributed clutter is represented as the product of a Rayleigh speckle component and the square root of a gamma distributed modulation process. A model describing the modulation process of arbitrary spatial autocorrelation function is presented. The key advantages of this model over previous models are that the spatial correlation is introduced to Gaussian processes, thus enabling well established linear filtering techniques to be used, the resulting clutter process is strictly K-distributed, and it leads to usable expressions for the multivariate description of the modulation and clutter processes.
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Property of optimal resource sharing policy in systems with N types of competing customer
  • Author(s): C.N. Stavropoulos  and  E.D. Sykas
  • Source: Electronics Letters, Volume 27, Issue 15, p. 1356 –1358
  • DOI:  10.1049/el:19910854
  • Type: Article
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  • p. 1356 –1358 (3)
    The problem of capacity allocation to a number of different types of customer is considered. The model is an N-dimensional generalisation of the Erlang loss model. Assuming infinite population for each type of customer, the problem is to improve the system performance which is measured as loss probability. A structural property of the optimal policy is derived. It follows that the optimally scheduled system will have, with nonzero probability, to use all its capacity.
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Measurement of negative differential conductance to 40 GHz for vertically integrated resonant tunnelling diodes
Reverse exchange method for burying proton exchanged waveguides
  • Author(s): J.L. Jackel  and  J.J. Johnson
  • Source: Electronics Letters, Volume 27, Issue 15, p. 1360 –1361
  • DOI:  10.1049/el:19910856
  • Type: Article
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  • p. 1360 –1361 (2)
    Reverse exchange has been used to bury proton exchanged LiNbO3 waveguides. Following initial exchange and annealing steps, which define the guides, a second exchange reintroduces lithium, thus lowering the extraordinary refractive index at the surface. The buried guides have little optical power at the surface and a more nearly symmetrical mode than unburied guides, resulting in lower propagation losses and better fibre-to-guide coupling.
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InP/InGaAsP/InGaAs SAGM avalanche photodiode with delta-doped multiplication region
  • Author(s): R. Kuchibhotla ; J.C. Campbell ; C. Tsai ; W.T. Tsang ; F.S. Choa
  • Source: Electronics Letters, Volume 27, Issue 15, p. 1361 –1363
  • DOI:  10.1049/el:19910857
  • Type: Article
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  • p. 1361 –1363 (3)
    Gain-bandwidth products as high as 86 GHz have been reported for SAGM (separate absorption, grading, and multiplication) avalanche photodiodes. However, higher performance has been severely limited by very tight design constraints emanating from fundamental material properties. Smaller multiplication widths, needed to increase the gain-bandwidth product, have been difficult to implement due to the maximum doping limit in InP brought on by the onset of tunnelling. Fabrication of a novel SAGM-APD is reported, in which the placement of change in the avalanche region is controlled through delta doping. The advantage of this approach results from the ensuing decoupling of the doping and thickness requirements of the avalanche region. Low dark currents and gain-bandwidth products of over 75 GHz have been obtained. In addition, by incorporating a surface reflector, a high quantum efficiency of 67% has been obtained with an absorption region only 1.1 μm thick.
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MQW amplifier optical bistability
Simplified evaluation of outage probability for cellular mobile radio systems
Effect of self-feedback in dynamic neural networks
  • Author(s): R. Perfetti
  • Source: Electronics Letters, Volume 27, Issue 15, p. 1367 –1369
  • DOI:  10.1049/el:19910860
  • Type: Article
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  • p. 1367 –1369 (3)
    In most neural network applications, the network outputs are required to be binary, i.e. to correspond to a vertex of the output hypercube space. It is shown how, in the presence of positive self-feedback, binary outputs can be guaranteed even with finite sigmoid slope, or with asymmetric connection matrices. An expression is derived, which gives a lower bound on the sigmoid slope, in order that equilibrium points, corresponding to nonbinary solutions, be unstable.
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Femtosecond soliton transmission in 18 km-long dispersion-shifted, distributed erbium-doped fibre amplifier
  • Author(s): M. Nakazawa  and  K. Kurokawa
  • Source: Electronics Letters, Volume 27, Issue 15, p. 1369 –1371
  • DOI:  10.1049/el:19910861
  • Type: Article
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  • p. 1369 –1371 (3)
    Femtosecond optical soliton transmission characteristics in a dispersion-shifted, distributed erbium-doped fibre amplifier as long as 18.2 km have been investigated. The erbium fibre has a dual shape core structure with a doping concentration of 0.5 ppm. Solitons (A = 0.7−1.2) with a pulse width of about 450 fs have been successfully transmitted, and even a slight narrowing was observed. When the soliton width was reduced to 260 fs, the output pulse width always broadened up to around 470 fs.
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Thermal stress and defect reduction in undercut GaAs on Si substrate
  • Author(s): S. Sakai ; K. Kawasaki ; M. Okada ; N. Wada ; Y. Shintani
  • Source: Electronics Letters, Volume 27, Issue 15, p. 1371 –1372
  • DOI:  10.1049/el:19910862
  • Type: Article
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  • p. 1371 –1372 (2)
    Results of a TCA (thermal cycle annealing) experiment on UCGAS (undercut GaAs on Si) in which the GaAs/Si interface is partially etched to separate the GaAs layer from the substrate are reported. The structure is developed to reduce the thermal stress in GaAs grown on Si. A drastic EPD (etch pit density) reduction by TCA is observed by eliminating the GaAs/Si interface which acts as a dislocation source, and a dislocation-free region about 6 μm wide is obtained at the edge of the structure. Therefore, it is possible to eliminate both the thermal stress and the dislocations at the edge of the UCGAS.
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Low threshold current lateral injection lasers on semi-insulating substrates fabricated using Si impurity-induced disordering
Experimental gain and saturation performance of GaAs/AlGaAs SCH quantum well travelling wave optical amplifier
  • Author(s): C. Tombling ; T. Saitoh ; Y. Suzuki ; H. Tanaka
  • Source: Electronics Letters, Volume 27, Issue 15, p. 1374 –1376
  • DOI:  10.1049/el:19910864
  • Type: Article
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  • p. 1374 –1376 (3)
    Successful combination of high gain and high saturation output power performance in a GaAs/AlGaAs quantum well travelling wave amplifier is reported. Comparable performance to similar 1.5 μm InGaAs/InP devices is achieved, surpassing expectations. A device with a three quantum well active region and separately confined heterostructure design has both a small signal gain of 22.9 dB and a saturation output power of 40 mW at the low drive current of 40 mA.
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New concept of asynchronous multiplexing of digital signals
Low noise tuned optical receivers using commercial 50 Ω modular microwave amplifiers
  • Author(s): M. Marin ; D.F. Hewit ; P.K. Lee ; R.S. Tucker
  • Source: Electronics Letters, Volume 27, Issue 15, p. 1378 –1379
  • DOI:  10.1049/el:19910866
  • Type: Article
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  • p. 1378 –1379 (2)
    A noise-reduction technique for low-noise optical receivers using commercial 50 Ω modulator microwave amplifiers is presented. The technique is illustrated with the design of a receiver using a high impedance transmission line as an impedance-matching circuit between a pin photodetector and a commercial 50 Ω modulator amplifier. A greater than 8 dB noise improvement relative to a 50 Ω untuned receiver over a 0.7 GHz bandwidth, and noise levels approaching those of high performance custom-mode receivers that employ packaged GaAs-FETs/HEMTs are reported.
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Optical method for detecting biphase coded signals
Discretely-tuned N-frequency laser for packet switching applications based on WDM
  • Author(s): B. Glance ; U. Koren ; C.A. Burrus ; J.D. Evankow
  • Source: Electronics Letters, Volume 27, Issue 15, p. 1381 –1383
  • DOI:  10.1049/el:19910868
  • Type: Article
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  • p. 1381 –1383 (3)
    A fast tunable laser for packet switching applications based on wavelength-division multiplexing (WDM) is presented. The laser is tunable to 16 discrete frequencies regularly spaced by 43 GHz over a tuning range of 645 GHz centred around a wavelength of 1.53 μm. It can be switched randomly in less than 5 ns among these frequencies. Importantly, the same comb of frequencies is obtained from different lasers fabricated by the same lithographic process. This greatly simplifies the implementation of optical WDM systems.
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Model reduction by generalised least-squares method
Path loss prediction in multifloored buildings at 914 MHz
  • Author(s): S.Y. Seidel  and  T.S. Rappaport
  • Source: Electronics Letters, Volume 27, Issue 15, p. 1384 –1387
  • DOI:  10.1049/el:19910870
  • Type: Article
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  • p. 1384 –1387 (4)
    Quantitative models are presented that predict the effect of walls, office partitions, floors, and building layout on path loss at 914 MHz. Average floor attenuation factors (FAF), which describe the additional path loss (in dB) caused by floors between transmitter and receiver are found for up to four floors in a typical office building. Average FAFs are 12.9 dB and 16.2 dB for one floor between the transmission and receiver in two different office buildings. For same floor measurements, attenuation factors (AF) are found to be 1.4 dB for each cloth-covered office partition and 2.4 dB for each concrete wall between transmitter and receiver.
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Effects of photoexcited carriers on dynamic response of quantum-well optical modulators
  • Author(s): S. Nojima ; P.D. Larsen ; A.-D. Larsen ; O. Mitomi ; K. Wakita ; M. Naganuma
  • Source: Electronics Letters, Volume 27, Issue 15, p. 1387 –1389
  • DOI:  10.1049/el:19910871
  • Type: Article
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  • p. 1387 –1389 (3)
    The dynamic response of quantum-well optical modulators in the intrinsic domain is discussed on the basis of a proposed simple model, characterised by the following two processes: excitonic response and photoexcited-carrier relaxation. The response is found to be enhanced in a certain region of modulation frequency and optical power density (quasiresonance phenomena). Comparison between the two most promising quantum-well materials (InGaAs/InP and InGaAs/InAlAs) indicates that the former is more liable to be affected by the photoexcited carriers than the latter.
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K-band suspended substrate stripline tapped combline filter
  • Author(s): W.-T. Lo  and  C.-K.C. Tzuang
  • Source: Electronics Letters, Volume 27, Issue 15, p. 1389 –1390
  • DOI:  10.1049/el:19910872
  • Type: Article
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  • p. 1389 –1390 (2)
    A newly developed 19.5–20.5 GHz combline bandpass filter realised by multiple coupled suspended substrate striplines (MCSSSs) and metal-insulator-metal (MIM) capacitors is presented. The filter design uses an iterative field-theory-based algorithm to account for the composite effects of multiple dominant quasi-TEM modes of the MCSSS and the couplings through the nonadjacent lines. A prototype is built and tested. The measured and theoretical filter characteristics are in good agreement for the combline filter without any tuning.
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Noise performance of distributed fibre amplifiers
Congestion control for multipoint packet voice
Erratum: Optical beam former for phased arrays with independent control of radiated frequency and phase
Erratum: Universal network realising basic piecewise-linear I/V characteristics

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