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1350-911X
Print ISSN
0013-5194
Electronics Letters
Volume 19, Issue 16, 4 August 1983
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Volume 19, Issue 16
4 August 1983
Polarisation-holding directional coupler made from elliptically cored fibre having a D section
- Author(s): R.B. Dyott and J. Bello
- Source: Electronics Letters, Volume 19, Issue 16, page: 601 –601
- DOI: 10.1049/el:19830409
- Type: Article
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A polarisation-holding directional coupler has been made using single-mode fibre having an elliptical core. An isolation of 21 dB between polarisation has been achieved together with an estimated insertion loss < 0.2 dB.
4-layer inductive grid FSS at 45° incidence
- Author(s): M.A.A. El-Morsy ; E.A. Parker ; R.J. Langley
- Source: Electronics Letters, Volume 19, Issue 16, p. 602 –603
- DOI: 10.1049/el:19830410
- Type: Article
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Transmission/reflection-band centre ratios of about 1.3 can be attained with multiple layers of inductive or capacitive grids, or with single-layer arrays of more complex elements. The copolar losses and the linear crosspolar performance of a 4-layer inductive grid and a 2-layer array of concentric rings are compared to illustrate some of the problems that can arise experimentally.
Canonical extremal vertices of a switching function and its dual
- Author(s): A.K. Sarje
- Source: Electronics Letters, Volume 19, Issue 16, p. 603 –604
- DOI: 10.1049/el:19830411
- Type: Article
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A relationship is known that holds for the extremal vertices of a function and its dual, and also for the boundary points of a threshold function and its dual. If the given functional is canonical, then the canonical extremal vertices form a subset of extremal vertices. It is the purpose of the letter to show that a similar relationship is true also for the canonical extremal vertices of a switching function.
Acousto-optic phase modulator for single-mode fibres
- Author(s): K. Nosu ; H.F. Taylor ; S.C. Rashleigh ; J.F. Weller
- Source: Electronics Letters, Volume 19, Issue 16, p. 605 –607
- DOI: 10.1049/el:19830412
- Type: Article
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A compact fibre-optic phase modulator with a single-mode fibre positioned along the axis of a cylindrical PZT acoustic transducer is investigated. The fibre is bonded inside a glass capillary tube, which is in turn epoxied inside the transducing cylinder to give a solid, mechanically stable structure. The maximum sensitivity of the phase shifter is 0.058 rad/V cm at 6.02 MHz. No polarisation modulation is observed.
Anodic oxide gate a-Si:H MOSFET
- Author(s): H. Yamamoto ; T. Sawada ; S. Arimoto ; H. Hasegawa ; H. Ohno
- Source: Electronics Letters, Volume 19, Issue 16, p. 607 –608
- DOI: 10.1049/el:19830413
- Type: Article
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–608
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The first a-Si:H MOSFET having native oxide at the insulator/a-Si:H interface is reported. Anodic oxidation in the AGW electrolyte is applied to Al/a-Si:H structures to form Al2O3/native oxide/a-Si:H gate structures. Resulting FETs show typical effective mobilities of 0.02 cm2/V s after proper low-temperature annealing in H2. Anodic oxidation is thus proved to be applicable to a-Si:H device technology as a low-temperature oxidation process.
Digital complex sampling
- Author(s): V. Considine
- Source: Electronics Letters, Volume 19, Issue 16, p. 608 –609
- DOI: 10.1049/el:19830414
- Type: Article
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Complex sampling is often employed in digital signal processing schemes where the input signal is bandpass in origin and is to be processed using lowpass techniques. Conventionally the signal is first mixed to zero centre frequency in two quadrature channels, filtered to remove the high-frequency mixing products and then digitised in two A/D convertors. A method is proposed that employs only one A/D convertor followed by digital mixing to produce the required pair of signals, thus allowing a considerable saving in hardware.
Annealing behaviour of gamma-ray-induced electron traps in LEC n-InP
- Author(s): J. Koyama ; J. Shirafuji ; Y. Inuishi
- Source: Electronics Letters, Volume 19, Issue 16, p. 609 –611
- DOI: 10.1049/el:19830415
- Type: Article
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The annealing behaviour of a gamma-ray-induced dominant electron trap (Ec − 0.79 eV) in LEC undoped n-InP is studied by means of the DLTS technique. The isothermal annealing experiment shows it is a first-order process with an activation energy of 0.98 eV; this value is much smaller than those found in room-temperature-irradiated n-GaAs.
GaInAs/InP large bandwidth (> 2 GHz) PIN detectors
- Author(s): T.P. Pearsall ; R.A. Logan ; C.G. Bethea
- Source: Electronics Letters, Volume 19, Issue 16, p. 611 –612
- DOI: 10.1049/el:19830416
- Type: Article
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Ga0.47In0.53As/InP heterophotodiodes are demonstrated with a bandwidth greater than 2 GHz, less than 0.5 pF capacitance, and subnanoampere dark current at the operating bias. These photodiodes satisfy criteria for both low noise and high speed in the 1 MHz–2 GHz bit-rate range for optical fibre telecommunications
Integrated optical polariser on LiNbO3:Ti channel waveguides using proton exchange
- Author(s): M. Papuchon and S. Vatoux
- Source: Electronics Letters, Volume 19, Issue 16, p. 612 –613
- DOI: 10.1049/el:19830417
- Type: Article
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A polariser on a Ti:LiNbO3 channel waveguide has been realised using a double fabrication process (Ti indiffusion and proton exchange). A region is created where the extraordinary polarisation experiences a leaky propagation leading to an extinction ratio of 30 dB and excess loss of about 1 dB.
Experimental realisation of a full adder by substrate fed threshold logic structure
- Author(s): C.H. Han and C.K. Kim
- Source: Electronics Letters, Volume 19, Issue 16, p. 613 –615
- DOI: 10.1049/el:19830418
- Type: Article
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A full adder has been designed and fabricated utilising substrate fed threshold logic. The internal operation is performed by four-valued threshold currents while the input and output signals are of binary form. The delay times of the experimental circuit operating with 10 μA per injection window have been measured as 5 μs for the sums and 1 μs for the carry.
Novel stray-insensitive SC bandpass filter
- Author(s): P.V. Ananda Mohan ; V. Ramachandran ; M.N.S. Swamy
- Source: Electronics Letters, Volume 19, Issue 16, p. 615 –616
- DOI: 10.1049/el:19830419
- Type: Article
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–616
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A new stray-insensitive SC bandpass filter derived from Moschytz's modified Tarmy-Ghausi configuration is described. Design equations and comparison with the Fleischer-Laker biquad are presented.
New absorption bands in pure and F-doped silica optical fibres
- Author(s): W. Heitmann ; H.U. Bonewitz ; A. Mühlich
- Source: Electronics Letters, Volume 19, Issue 16, p. 616 –617
- DOI: 10.1049/el:19830420
- Type: Article
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Two very narrow absorption bands positioned at 765 nm and at 1273 nm have been found in pure silica and fluorinedoped silica optical fibres. Their origin is probably connected with the preform production technique. Annealing of the preform and different fibre drawing conditions did not influence the absorption bands.
Assessment of principal planes orientation in a terrestrial link at 18 GHz during intense rainfall
- Author(s): D. Maggiori ; P. Migliorini ; A. Paraboni
- Source: Electronics Letters, Volume 19, Issue 16, p. 617 –619
- DOI: 10.1049/el:19830421
- Type: Article
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Simultaneous measurements of attenuation and depolarisation at 18 GHz collected during a propagation experiment on a 9.5 km terrestrial link have been employed to extract information about the angle formed by the principal planes with respect to the vertical-horizontal orientations (canting angle). Tilted polarisation planes have been adopted in order to increase the system sensitivity and to detect the sign of the angle according to a new technique recently devised.
Field ionised impurity scattering in an AlGaAs/GaAs two-dimensional electron gas
- Author(s): A. Livingstone ; K. Tsubaki ; M. Kawashima ; H. Okamoto ; K. Kumabe
- Source: Electronics Letters, Volume 19, Issue 16, p. 619 –620
- DOI: 10.1049/el:19830422
- Type: Article
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–620
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Low field-mobility saturation has been observed in AlGaAs/GaAs heterostructures. Under illumination, the mobility decreases and the carrier concentration increases at high fields. Both effects are thought to be due to ionisation of a centre in the GaAs, probably oxygen. The experimental results are explained in terms of a simple trap model.
Efficient backward and forward pumping CW Raman amplification for InGaAsP laser light in silica fibres
- Author(s): Y. Aoki ; S. Kishida ; H. Honmou ; K. Washio ; M. Sugimoto
- Source: Electronics Letters, Volume 19, Issue 16, p. 620 –622
- DOI: 10.1049/el:19830423
- Type: Article
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–622
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By pumping a small-core single-mode silica fibre with a 1.32 μm CW Nd:YAG laser, continuous-wave Raman amplification of InGaAsP laser diode light, with unsaturated gain as high as 21 dB, has been obtained in both backward as well as forward pumping configurations.
Radiation-hardened pure silica-core fibre optics
- Author(s): R.H. West and A.P. Lenham
- Source: Electronics Letters, Volume 19, Issue 16, p. 622 –623
- DOI: 10.1049/el:19830424
- Type: Article
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Transmission losses induced by ionising radiation in fibre opties having cores drawn from pure synthetic silica may be reduced by pre-exposure to large hardening doses. Characteristics of the hardened fibres are described and the necessary features of the hardening irradiations identified.
Radiation characteristics of coaxial waveguides as a small primary feed
- Author(s): L. Shafai ; A.A. Kishk ; A. Ittipiboon
- Source: Electronics Letters, Volume 19, Issue 16, p. 623 –625
- DOI: 10.1049/el:19830425
- Type: Article
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–625
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The radiation patterns of coaxial waveguides with a TE11 exciting mode are computed numerically. It is shown that by a proper selection of the coaxial aperture dimensions the symmetry of the copolar patterns can be improved considerably. Coaxial radiators can therefore be designed as a useful small primary feed for paraboloid reflector antennas.
Measurement of small optically pulse-modulated reflection coefficients
- Author(s): W. Platte and W. Renz
- Source: Electronics Letters, Volume 19, Issue 16, p. 625 –627
- DOI: 10.1049/el:19830426
- Type: Article
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The letter presents a new method for measuring small pulse modulated complex reflection coefficients of which both phase and magnitude are a rapidly varying function of time. The method is based on a single-point dynamic balance of two differently pulse-modulated signals produced in a modified reflection coefficient bridge. The measuring procedure is described in detail, and the first experimental results are discussed.
Influence of spectral hole-burning on quaternary laser transients
- Author(s): M.J. Adams and M. Osiński
- Source: Electronics Letters, Volume 19, Issue 16, p. 627 –628
- DOI: 10.1049/el:19830427
- Type: Article
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–628
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Multimode rate equations including inhomogeneous gain saturation have been solved both numerically and by an analytic small-signal analysis. The results indicate that the principal effect of spectral hole-burning on transient behaviour is to reduce the damping time of relaxation oscillations.
a-Si:H MIS position sensitive detector by anodic oxidation processes
- Author(s): S. Arimoto ; H. Yamamoto ; H. Ohno ; H. Hasegawa
- Source: Electronics Letters, Volume 19, Issue 16, p. 628 –629
- DOI: 10.1049/el:19830428
- Type: Article
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The first fabrication of an amorphous silicon position-sensitive detector using an MIS structure by anodic oxidation processes is reported. The fabricated 3 mm × 26 mm one-dimensional position-sensitive detectors show excellent linearity with lateral photocurrent response, having a correlation coefficient of 0.996.
Evaluation of feature-extracted images for deaf communication
- Author(s): D.E. Pearson
- Source: Electronics Letters, Volume 19, Issue 16, p. 629 –631
- DOI: 10.1049/el:19830429
- Type: Article
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Tests of the intelligibility of two types of feature-extracted images for deaf communication are reported, at data rates around 10 kbit/s. A mean score of 34% (based on word count) was obtained for 4 sequences; however, individual scores on some sequences were 100% correct. The results point to the need for better form identification and two-way system evaluations.
Enhanced regenerative switching circuit for power transistors
- Author(s): A. Akademir
- Source: Electronics Letters, Volume 19, Issue 16, p. 631 –632
- DOI: 10.1049/el:19830430
- Type: Article
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The letter describes a novel combination of the conventional regenerative base drive circuit and the snubber circuit, which utilises the snubber current to accelerate the switching performance of a power transistor. The technique is particularly useful in high-frequency switch mode power supply applications.
Growth of Al0.3Ga0.7As by molecular beam epitaxy in the forbidden temperature range using As2
- Author(s): L.P. Erickson ; T.J. Mattord ; P.W. Palmberg ; R. Fischer ; H. Morkoc
- Source: Electronics Letters, Volume 19, Issue 16, p. 632 –633
- DOI: 10.1049/el:19830431
- Type: Article
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Using a thermal cracker and polycrystalline arsenic source material, dimeric arsenic was obtained and utilised to grow Al0.3Ga0.7As layers in the temperature range of 600–700°C with excellent surface morphologies. It has been previously found that, with tetrameric arsenic, excellent surface morphologies were possible only below 630°C and above 690°. Based on these observations, it is postulated that above 630°C tetrameric arsenic has a surface lifetime that is too short to provide enough coverage even when the beam flux is increased dramatically. At and above 700°C, tetrameric arsenic is cracked more effectively by the surface energy gained from the substrate leading to a good surface coverage and to good surface morphologies.
Mixed measure error function for nonlinear mapping algorithms
- Author(s): Da-Kai Wang
- Source: Electronics Letters, Volume 19, Issue 16, p. 634 –635
- DOI: 10.1049/el:19830432
- Type: Article
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p.
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–635
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A new mixed measure error function is presented and tested.
Optimisation in linear system reduction
- Author(s): Sau-Man Yang and Rein Luus
- Source: Electronics Letters, Volume 19, Issue 16, p. 635 –637
- DOI: 10.1049/el:19830433
- Type: Article
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The ease of using optimisation in model reduction is demonstrated. When direct search optimisation is used to minimise the error between the time response of the original system and the time response of the reduced model, all types of constraints can be handled, such as the stability property and zero steady-state error.
Syndrome-testable internally unate combinational networks
- Author(s): E. Eris and D.M. Miller
- Source: Electronics Letters, Volume 19, Issue 16, p. 637 –638
- DOI: 10.1049/el:19830434
- Type: Article
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A combinational network is syndrome-testable with respect to a particular fault if the faulty network realises a function with a different number of ones from the function realised by the fault-free network. Here we investigate the syndrometestability of single stuck-at faults in internally unate combinational networks. We show how such a network can be made syndrome-testable for single stuck-at faults by the addition of a single control line. In the case of a two-level network, at most one additional first-level gate is added to the network.
Design of lowpass two-section generalised FLF active filters
- Author(s): M. Biey
- Source: Electronics Letters, Volume 19, Issue 16, p. 639 –640
- DOI: 10.1049/el:19830435
- Type: Article
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–640
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The letter presents results on the realisation of highly selective lowpass filters employing a cascade connection of biquads and 4th-order blocks realised as two-section generalised follow-the-leader feedback (GFLF) structures.
Dielectric image line leaky wave antenna for broadside radiation
- Author(s): K. Solbach and B. Adelseck
- Source: Electronics Letters, Volume 19, Issue 16, p. 640 –641
- DOI: 10.1049/el:19830436
- Type: Article
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A dielectric image line leaky wave antenna is presented, capable of efficient operation at broadside. The stopband phenomenon at broadside is avoided by using pairs of radiator elements at 90° phase quadrature (quarter-wave spacing).
Performance degradation due to stimulated Raman scattering in wavelength-division-multiplexed optical-fibre systems
- Author(s): A.R. Chraplyvy and P.S. Henry
- Source: Electronics Letters, Volume 19, Issue 16, p. 641 –643
- DOI: 10.1049/el:19830437
- Type: Article
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The effects of stimulated Raman scattering (SRS) on a two-channel wavelength-division-multiplexed optical-fibre communication system are analysed. For both amplitude and angle modulation the most important effect of SRS is increased loss for the short-wavelength channel, which in the worst case limits the maximum usable transmitter power to ∼ 50 mW.
Effects of loss on equivalent-step-index fibre determination
- Author(s): C. Pask and F. Rühl
- Source: Electronics Letters, Volume 19, Issue 16, p. 643 –644
- DOI: 10.1049/el:19830438
- Type: Article
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The effects of waveguide losses on equivalent-step-index (ESI) determination are investigated with Millar's method as an example. The fitting of spot-size data when the second-mode cutoff wavelength is underestimated leads to the use of an inappropriate formula or the deduction of a too-small ESI radius. In the latter case the ESI numerical aperture will still be given with good accuracy.
New approach towards frequency stabilisation of linewidth-narrowed semiconductor lasers
- Author(s): C.J. Nielsen and J.H. Osmundsen
- Source: Electronics Letters, Volume 19, Issue 16, p. 644 –646
- DOI: 10.1049/el:19830439
- Type: Article
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By means of controlling the injection current and the phase of optical feedback, simultaneous frequency stabilisation and line-width reduction of a semiconductor laser are demonstrated. Line-width reduction from 24 MHz to 300 kHz and mean frequency stability better than 800 Hz relative to a Fabry-Perot etalon were obtained.
Digitally controlled amplifiers with fewer resistors and sensitivities
- Author(s): T.S. Rathore
- Source: Electronics Letters, Volume 19, Issue 16, p. 646 –647
- DOI: 10.1049/el:19830440
- Type: Article
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New digitally controlled amplifiers are proposed. They have fewer resistors and reduced sensitivities compared to Koutzarov's amplifiers.
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