Online ISSN
1350-911X
Print ISSN
0013-5194
Electronics Letters
Volume 15, Issue 22, 25 October 1979
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Volume 15, Issue 22
25 October 1979
D.F.T. computation by fast polynomial transform algorithms
- Author(s): H.J. Nussbaumer
- Source: Electronics Letters, Volume 15, Issue 22, p. 701 –702
- DOI: 10.1049/el:19790498
- Type: Article
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A new method is introduced for the fast computation of multidimensional discrete Fourier transforms (d.f.t.). We show that some multidimensional d.f.t.s are mapped efficiently into one-dimensional d.f.t.s by using a single polynomial transform and some auxiliary calculations. Since polynomial transforms can be computed without multiplications, this approach reduces significantly the number of operations over the conventional fast Fourier transform (f.f.t.) and is therefore attractive for image-processing applications.
Mg-doped InGaAsP/InP l.e.d.s for high-bit-rate optical-communication systems
- Author(s): H. Grothe ; W. Proebster ; W. Harth
- Source: Electronics Letters, Volume 15, Issue 22, p. 702 –703
- DOI: 10.1049/el:19790499
- Type: Article
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The design criteria for high-speed luminescent diodes are applied to realise InGaAsP/InP l.e.d.s at 1.26 μm wavelength. By highly doping the active region with Mg, a modulation bandwidth in excess of 1 GHz is achieved.
Rain attenuation of 12/14 GHz satellite video transmissions
- Author(s): O.G. Nackoney and D. Davidson
- Source: Electronics Letters, Volume 15, Issue 22, p. 703 –704
- DOI: 10.1049/el:19790500
- Type: Article
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Concurrent beacon and wideband f.m. video rainfall fades were measured utilising the Communications Technology Satellite (CTS). Results indicate picture signal/noise ratio during rain attenuation follows that expected for pure attenuation, and video/beacon attenuation ratio is 11–22% higher than theoretical predictions.
Double-alkali effect: influence on index profile of ion-exchanged waveguides
- Author(s): V. Neuman ; O. Parriaux ; L.M. Walpita
- Source: Electronics Letters, Volume 15, Issue 22, p. 704 –706
- DOI: 10.1049/el:19790501
- Type: Article
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Optical waveguides approximating a step-index profile have been fabricated in soda-lime glass by ion-exchanging rubidium or caesium for sodium. We show that the low propagation losses and the diffusion profile are related to the interaction between the two alkalis.
Wavelength-dependent transmission at fibre connectors
- Author(s): K. Petermann
- Source: Electronics Letters, Volume 15, Issue 22, p. 706 –708
- DOI: 10.1049/el:19790502
- Type: Article
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It is shown that the transmission loss of a fibre connector with a preceding fibre is extremely wavelength-dependent. A change of laser wavelength by only 0.01 Å may suffice to change the transmission by 10% when using typical multi-mode fibres.
Rapidly converging observers involve high-order differentiations
- Author(s): M. Zeitz
- Source: Electronics Letters, Volume 15, Issue 22, p. 708 –709
- DOI: 10.1049/el:19790503
- Type: Article
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It has frequently been noticed that rapidly converging observers also act as differentiators and thus amplify noise in the input. This property is proved mathematically for the special case of a single output system.
Synthesis of matched b.j.t. cascode broadband amplifiers
- Author(s): D.J. Ahlgren
- Source: Electronics Letters, Volume 15, Issue 22, p. 709 –710
- DOI: 10.1049/el:19790504
- Type: Article
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The letter describes a way to determine gain-bandwidth limitations of high-gain matched broadband amplifiers that are based on a cascode connection of bipolar junction transistors (b.j.t.s). An example is included to illustrate the method.
Monolithic 256-point programmable transversal filter
- Author(s): P.B. Denyer and J. Mavor
- Source: Electronics Letters, Volume 15, Issue 22, p. 710 –712
- DOI: 10.1049/el:19790505
- Type: Article
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A 256-point programmable transversal filter has been integrated and assembled for use within a 16-pin d.i.l. package. The filter is realised in n-channel c.c.d./m.o.s. technology and incorporates novel operational amplifiers and other peripheral circuitry on-chip.
Spectral characterisation of ternary threshold functions
- Author(s): Claudio Moraga
- Source: Electronics Letters, Volume 15, Issue 22, p. 712 –713
- DOI: 10.1049/el:19790506
- Type: Article
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In this communication, the question of characterising a ternary threshold function by a few coefficients of its series expansion in terms of Chrestenson functions is examined. It is shown that an n-place ternary threshold function may be uniquely characterised by (n+2) coefficients; (n+1) of them correspond to particular elements of the Chrestenson spectrum of the function and the n+2nd is the summation over all magnitude-squared spectral elements.
In0.53Ga0.47As p-i-n photodiodes for long-wavelength fibre-optic systems
- Author(s): R.F. Leheny ; R.E. Nahory ; M.A. Pollack
- Source: Electronics Letters, Volume 15, Issue 22, p. 713 –715
- DOI: 10.1049/el:19790507
- Type: Article
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We describe p-i-n photodiodes fabricated from In0.53Ga0.47As grown lattice-matched on InP substrates. These diodes exhibit low junction capacitance (C<1 pF at 20 V reverse bias), low dark current (≈10 nA), high break-down voltage (110 V) and wide photoresponse extending beyond 1.7 μm.
Recursive linear estimation of linearly constrained parameters
- Author(s): J.P. Norton
- Source: Electronics Letters, Volume 15, Issue 22, p. 715 –716
- DOI: 10.1049/el:19790508
- Type: Article
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Recursive linear estimation of a parameter vector subject to a linear equality constraint is discussed with reference to a recently proposed Kalman-filter method derived using pseudo-inverses to solve an undetermined least-squares problem. The action of the method is compared with that of an alternative which treats the constraint as an observation, and the circumstances favouring each, or neither, are considered.
Combination of complex rectangular transforms and f.n.t. to implement fast convolution
- Author(s): N. Sridhar Reddy and V. Umapathi Reddy
- Source: Electronics Letters, Volume 15, Issue 22, p. 716 –718
- DOI: 10.1049/el:19790509
- Type: Article
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Recently, complex rectangular transforms (c.x.r.t.s) have been derived which can be shown to be more efficient than rectangular transforms (r.t.s) for computing convolution of complex sequences. This letter proposes the combination of complex rectangular transforms with the Fermat number transform (f.n.t.) to devise efficient algorithms for computing error-free convolutions of both real and complex sequences. The results show that the combination of c.x.r.t. and f.n.t. requires fewer multiplications compared to that of r.t. and f.n.t.
Ultraviolet photoconductive detectors in Zn3P2
- Author(s): K.G. Irwin ; N.S. Kopeika ; R.G. Hunsperger
- Source: Electronics Letters, Volume 15, Issue 22, page: 718 –718
- DOI: 10.1049/el:19790510
- Type: Article
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Photoconductive detectors with relatively flat response to wavelengths as short as 2500 Å have been fabricated in thin films of zinc phosphide deposited by the close-space-transport method on to mica substrates. Responsivity at 2527 Å was 0.13 A/W.
Explicit solution of calibration equations for a dual 6-port network analyser
- Author(s): D. Woods
- Source: Electronics Letters, Volume 15, Issue 22, p. 718 –720
- DOI: 10.1049/el:19790511
- Type: Article
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Application of the 6-port reflectometer for the measurement of complex reflection coefficient, without the direct measurement of phase, is extended to a dual 6-port system for the characterisation of 2-port networks in terms of S-parameters. The system is self-calibrating and no additional standards are needed if the two reflectometers are first calibrated individually by measurements referred to calculated standards of impedance.
Fast technique for computing syndromes of B.C.H. and Reed-Solomon codes
- Author(s): T.K. Truong ; R.L. Miller ; I.S. Reed
- Source: Electronics Letters, Volume 15, Issue 22, p. 720 –721
- DOI: 10.1049/el:19790512
- Type: Article
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A new scheme for reducing the numerical complexity of the standard B.C.H. and Reed–Solomon (R.S.) decoding algorithms is developed. Specifically, the process of calculating syndromes over GF(2m) is shown to require only a small fraction of the number of multiplications and additions that is required by using standard methods. As an example, the calculation of the 32 syndromes of the (255, 223, 33) Reed–Solomon code (NASA standard for concatenation with convolutional codes) is shown to require 90% fewer multiplications and 78% fewer additions than the conventional method of computation. A computer simulation also verifies these results.
Analytical relations between modal power distribution and near-field intensity in graded-index fibres
- Author(s): S. Piazzola and G. de Marchis
- Source: Electronics Letters, Volume 15, Issue 22, p. 721 –722
- DOI: 10.1049/el:19790513
- Type: Article
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Modal power distribution is an important characteristic of optical fibres. Under the assumption that modes belonging to the same degenerate mode group carry the same amount of power, simple expressions are derived relating near-field intensity and modal power distribution in α-exponent index-profile optical fibres.
Fault-tolerant digital clocking systems
- Author(s): W.R. Moore
- Source: Electronics Letters, Volume 15, Issue 22, p. 722 –724
- DOI: 10.1049/el:19790514
- Type: Article
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The conflict between two published fault-tolerant digital clocking systems is resolved and a new design is given.
High-resolution analysis of exponentially decaying transients for physics d.l.t.s. experiments
- Author(s): M.S. Hodgart
- Source: Electronics Letters, Volume 15, Issue 22, p. 724 –725
- DOI: 10.1049/el:19790515
- Type: Article
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A class of analysing functions is proposed to improve the resolution of the measurement of exponential transients in d.l.t.s. experiments. These functions offer a trade-off between resolution and sensitivity to noise as measured by a signal/noise ratio. Implementation may be by either analogue or digital (point sampling) correlation.
Active C realisation for the general biquadratic voltage transfer functions
- Author(s): F. Anday
- Source: Electronics Letters, Volume 15, Issue 22, p. 725 –726
- DOI: 10.1049/el:19790516
- Type: Article
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An active C filter realizing the general biquadratic transfer function is given, using signal flow graphs.
Phosphor-doped silica cladding v.a.d. fibres
- Author(s): T. Edahiro ; S. Sudo ; M. Kawachi ; K. Jinguji ; N. Inagaki
- Source: Electronics Letters, Volume 15, Issue 22, p. 726 –728
- DOI: 10.1049/el:19790517
- Type: Article
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Loss reduction of v.a.d. (vapour-phase axial deposition) fibres at wavelengths of 1.3 μm and 1.6 μm was investigated. The infrared absorption loss was reduced by applying SiO2-P2O5 cladding instead of SiO2-B2O3 cladding and by minimising the waveguide imperfection loss. The minimum losses of the fabricated v.a.d. fibre were 0.5 dB/km and 0.28 dB/km at wavelengths of 1.3 μm and 1.6 μm, respectively. This fact indicates that fibres fabricated by the soot process, like those made by the vapour-phase axial-deposition process, can be used as long-wavelength optical transmission media. We have also found the OH absorption abnormality at wavelengths of 0.95, 1.24 and 1.39 μm, and the loss peak values are different from those reported.
Effect of finite size of ground plane on the impedance of a monopole immersed in a lossy medium
- Author(s): I.J. Bahl and S.S. Stuchly
- Source: Electronics Letters, Volume 15, Issue 22, p. 728 –729
- DOI: 10.1049/el:19790518
- Type: Article
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The effect of finite size of the ground plane on the impedance of a monopole immersed in a lossy medium is studied. The theoretical results show that for water medium and for the ratio of the ground-plane radius to free-space wavelength equal to and greater than 0.2, the effect of ground plane on the monopole impedance is negligible.
Dispersion minimisation in single-mode fibres over a wide spectral range
- Author(s): K. Okamoto ; T. Edahiro ; A. Kawana ; T. Miya
- Source: Electronics Letters, Volume 15, Issue 22, p. 729 –731
- DOI: 10.1049/el:19790519
- Type: Article
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The waveguide and material dispersion are investigated for various silica-based single-mode optical fibres with arbitrary refractive-index profiles. It is shown that in the case of the doubly clad optical fibre with an index difference between the core and the outer cladding Δ1=1% and that between the inner cladding and the outer Δ2=−1%, the diameter of the core 2a=7.2 μm, and the thickness of the inner cladding t=0.3a, the total dispersion is reduced within ± 1 ps/km/nm over a wide spectral range of λ=1.35–1.67 μm.
Erratum: Fourier-series representation for phase density of sum of signal, noise and interference
- Author(s): I.M. Kostic
- Source: Electronics Letters, Volume 15, Issue 22, page: 731 –731
- DOI: 10.1049/el:19790520
- Type: Article
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Erratum: Another method for the RC active simulation of doubly-terminated LC ladder filters
- Author(s): M.S. Piedade
- Source: Electronics Letters, Volume 15, Issue 22, page: 731 –731
- DOI: 10.1049/el:19790521
- Type: Article
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Erratum: Novel microwave GaAs field-effect transistors
- Author(s): J.C. Vokes ; B.T. Hughes ; D.R. Wight ; J.R. Dawsey ; S.J.W. Shrubb
- Source: Electronics Letters, Volume 15, Issue 22, page: 731 –731
- DOI: 10.1049/el:19790522
- Type: Article
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Erratum: Preparation and properties of GaAs layers for novel f.e.t. structures
- Author(s): R.J.M. Griffiths ; I.D. Blenkinsop ; D.R. Wight
- Source: Electronics Letters, Volume 15, Issue 22, page: 731 –731
- DOI: 10.1049/el:19790523
- Type: Article
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