Online ISSN
1350-911X
Print ISSN
0013-5194
Electronics Letters
Volume 12, Issue 21, 14 October 1976
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Volume 12, Issue 21
14 October 1976
Surface-acoustic-wave parametric amplifier
- Author(s): F.W. Smith
- Source: Electronics Letters, Volume 12, Issue 21, p. 545 –546
- DOI: 10.1049/el:19760415
- Type: Article
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p.
545
–546
(2)
Parametric amplification and oscillation of surface acoustic waves has been observed on lithium niobate by varying the stiffness of the surface within a resonator cavity.
Routine characterisation of single-mode fibres
- Author(s): W.A. Gambling ; D.N. Payne ; H. Matsumura ; R.B. Dyott
- Source: Electronics Letters, Volume 12, Issue 21, p. 546 –547
- DOI: 10.1049/el:19760416
- Type: Article
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p.
546
–547
(2)
In single-mode fibres, the core diameter and refractive-index difference between core and cladding may be found from the widths of (a) the halfpower points and (b) the first minimum of the far-field radiation. The technique has been used to study the effect of heat treatment.
Interdiffusion of metallic contact layers on silicon IMPATT diodes
- Author(s): D.V. Morgan ; M.J. Howes ; D.J. Taylor ; P. Brook
- Source: Electronics Letters, Volume 12, Issue 21, p. 547 –548
- DOI: 10.1049/el:19760417
- Type: Article
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p.
547
–548
(2)
A comparative study, using Rutherford backscattering of He ions, of Ag/Pt/Cr and Au/Pt/Cr metallisations on silicon substrates has shown that significant interdiffusion takes place for Ag/Pt/Cr at temperatures around 350°C, resulting in the removal of the platinum barrier layer. No such effect takes place at the same temperature for Au/Pt/Cr. These results are consistent with the observed life-test performance of devices with these metallisations.
Effect of dopants on transmission loss of low-OH-content optical fibres
- Author(s): H. Osanai ; T. Shioda ; T. Moriyama ; S. Araki ; M. Horiguchi ; T. Izawa ; H. Takata
- Source: Electronics Letters, Volume 12, Issue 21, p. 549 –550
- DOI: 10.1049/el:19760418
- Type: Article
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p.
549
–550
(2)
We formerly developed very-low-OH-content optical fibres consisting of a borosilicate cladding and a phosphosilicate core. The transmission loss of the fibre was 0.47 dB/km at 1.2 μm. We have further investigated the effects of dopants in pure silica on the losses of fibres. The letter clarifies the effects of dopants on the loss in the near-infrared region.
Combined frequency and phase-shift keying
- Author(s): M.J. O'Mahony
- Source: Electronics Letters, Volume 12, Issue 21, p. 550 –551
- DOI: 10.1049/el:19760419
- Type: Article
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p.
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–551
(2)
In previous letters, the constraints necessary for the elimination of i.s.i. in both binary and multilevel f.s.k. were discussed. It is now shown that a system with simultaneous phase and frequency modulation is possible, both modulations being detected with zero i.s.i. In terms of energy per bit required at the receiver input for a given error rate, a 4-phase 2-frequency system is shown to be superior to an equivalent 8-state multiphase or combined phase/amplitude system.
Reduction of linear systems by canonical forms
- Author(s): J. Hickin and N.K. Sinha
- Source: Electronics Letters, Volume 12, Issue 21, p. 551 –553
- DOI: 10.1049/el:19760420
- Type: Article
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–553
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A new companion-type realisation of a rational transfer function is introduced. This form is then used for obtaining a reduced-order model. It is possible, using this approach, to simultaneously match time moments, Markov parameters and to retain desired poles, thus combining the methods of partial realisation (Padé approximation) and aggregation.
Light-emitting diodes with a modulation bandwidth of more than 1 GHz
- Author(s): J. Heinen ; W. Huber ; W. Harth
- Source: Electronics Letters, Volume 12, Issue 21, p. 553 –554
- DOI: 10.1049/el:19760421
- Type: Article
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–554
(2)
The design principle and the fabrication of high-speed l.e.d.s with a 3dB modulation bandwidth in the gigahertz range is described. The modulation characteristic, radiance and spectrum have been measured. The results demonstrate that these l.e.d.s are suited as light generators in optical transmission systems with a bandwidth in excess of 1 GHz.
Frequency response of a digital network
- Author(s): K.P. Prasad and P.S. Reddy
- Source: Electronics Letters, Volume 12, Issue 21, p. 554 –555
- DOI: 10.1049/el:19760422
- Type: Article
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p.
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–555
(2)
To compute the frequency response of a multi-input multi-output digital network, an efficient method is to calculate from a knowledge of the poles and zeros of its transfer function. While poles can be obtained as eigenvalues of the state matrix, a simple method is presented for determining the zeros, too, as eigenvalues of a matrix.
Design of uncorrelated signals
- Author(s): P.A.N. Briggs and K.R. Godfrey
- Source: Electronics Letters, Volume 12, Issue 21, p. 555 –556
- DOI: 10.1049/el:19760423
- Type: Article
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–556
(2)
By considering the identification of a multi-input single-output process, it is shown that it is not possible to design uncorrelated sequences (of the same period) with autocorrelation functions of delta-function form This result is of importance not only in process identification, but also in the field of communication, where much effort has gone into trying to design uncorrelated sequences.
S.A.W. reflecting arrays
- Author(s): G.L. Matthaei ; F. Barman ; E.B. Savage
- Source: Electronics Letters, Volume 12, Issue 21, p. 556 –557
- DOI: 10.1049/el:19760424
- Type: Article
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p.
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–557
(2)
It is shown that metal surface-acoustic-wave reflecting arrays on piezoelectric substrates with a range of ratios t of electrode width to period can be modelled by a cascade of equal-length transmission-line sections. Measurements were made on short- and open-circuited arrays with various t ratios; impedance ratio r and average velocity data are presented against t.
Nonagreement of forward echo and return loss
- Author(s): P. Cochrane and R.M. Brooks
- Source: Electronics Letters, Volume 12, Issue 21, p. 558 –559
- DOI: 10.1049/el:19760425
- Type: Article
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p.
558
–559
(2)
Mathematical models of coaxial cables allow the derivation of relationships between the forward echo and return loss due to the periodic nature of the structure. Experimentation has served to demonstrate that the prediction of forward echo from return-loss information is limited in its application for practical cables. This is mainly due to the fact that coaxial cables do not always exhibit truly periodic structures. In the letter, we present results that indicate the disagreement that can occur in practice.
Raising the crossover level of dual-beam parabolic antennas
- Author(s): B.H.C. Liesenkötter
- Source: Electronics Letters, Volume 12, Issue 21, p. 559 –560
- DOI: 10.1049/el:19760426
- Type: Article
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p.
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–560
(2)
A method for raising the crossover level of dual-beam parabolic antennas is shown. Controlled coupling between the primary radiators, with the input ports almost decoupled simultaneously, can be applied to front-fed linearly polarised parabolic antennas of about 10° beamwidth. Mention is also made of a second method with lossy directional couplers.
Attenuation and wavelength measurement of lossy waveguides
- Author(s): R.J. King and R. Knudsen
- Source: Electronics Letters, Volume 12, Issue 21, p. 560 –562
- DOI: 10.1049/el:19760427
- Type: Article
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–562
(3)
A simple coherent detection system can accurately measure the attenuation and phase constants of an e.m. wave propagating in a lossy waveguide. The main advantages of the system are its great linearity, sensitivity and versatility. This allows precise measurements on a wide variety of waveguides, even when the losses are very large.
Low-frequency intensity fluctuations of c.w. d.h. GaAlAs-diode lasers
- Author(s): G. Tenchio
- Source: Electronics Letters, Volume 12, Issue 21, p. 562 –563
- DOI: 10.1049/el:19760428
- Type: Article
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p.
562
–563
(2)
The optical-emission fluctuations and the current noise of c.w. d.h. GaAlAs junction lasers have been investigated for the first time in the low-frequency range. In both the optical noise spectra and the current noise spectra, a l/f behaviour has been observed. It was found that a strong crosscorrelation exists between optical-emission noise and forward-current noise. Finally, an optoelectronic feedback method that practically eliminated the relative excess light noise has been demonstrated.
Incremental efficiency enhancement and r.f. response of GaAs-GaAlAs double-heterostructure stripe lasers
- Author(s): J.E. Carroll ; S.G. Eldon ; G.H.B. Thompson
- Source: Electronics Letters, Volume 12, Issue 21, p. 564 –565
- DOI: 10.1049/el:19760429
- Type: Article
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p.
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–565
(2)
Measurements of the photon-electron resonance frequency ωr on stripe lasers with nonlinear light-output/current characteristics have been made. It is found that ωr2 is not proportional to the steady bias light, as conventional theory states, but is approximately proportional to the current above threshold. A new theory is presented which accounts for the nonlinear light/current characteristics, including incremental efficiency enhancement and the changes of the resonance frequency with current.
Efficient method for trimming allpass sections
- Author(s): J.-P. Martens
- Source: Electronics Letters, Volume 12, Issue 21, p. 565 –567
- DOI: 10.1049/el:19760430
- Type: Article
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p.
565
–567
(3)
It is shown how excitation by triangular waves can be used to construct a very efficient method for trimming 2nd-order allpass sections. An oscilloscope is used as the measuring instrument.
Radiation from curved single-mode fibres
- Author(s): W.A. Gambling ; D.N. Payne ; H. Matsumura
- Source: Electronics Letters, Volume 12, Issue 21, p. 567 –569
- DOI: 10.1049/el:19760431
- Type: Article
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p.
567
–569
(3)
A study of propagation in curved single-mode fibres shows that the transmission loss increases sharply below a critical bend radius. However the radiation does not leak away uniformly with distance but in a series of discrete well-defined rays.
Efficient generation technique for polynomial codesets
- Author(s): L.F. Lind
- Source: Electronics Letters, Volume 12, Issue 21, page: 569 –569
- DOI: 10.1049/el:19760432
- Type: Article
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p.
569
(1)
The letter introduces a new technique for the generation of a set of polynomial codewords. Each word is generated with a single modulo-2 addition, rather than by using the conventional polynomial multiplication technique. The method is simple to apply and can form the basis for set generation by a minicomputer or microprocessor.
Technique for jointing small-core optical fibres
- Author(s): J.H. Stewart and P. Hensel
- Source: Electronics Letters, Volume 12, Issue 21, page: 570 –570
- DOI: 10.1049/el:19760433
- Type: Article
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p.
570
(1)
A simple technique for making permanent joints between optical fibres is described. The technique is suitable for small-core fibres, as well as those in which the core is not well centred in the cladding. Because the precision components required to make the alignment are reused, the cost per joint is low.
Two aspects of electro-optical-correlator implementation
- Author(s): B.A. Horwitz
- Source: Electronics Letters, Volume 12, Issue 21, p. 570 –572
- DOI: 10.1049/el:19760434
- Type: Article
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p.
570
–572
(3)
The form of reference mask functions and choice of c.c.d. clocking are considered for real implementations of an electro-optical correlator. The prefiltering of reference functions (with an inverse sine filter) is described, as is a clocking system which utilises all receptor sites in an interlaced, interline transfer c.c.d.
Erratum: Errors-and-erasures decoding of binary majority-logic-decodable codes
- Author(s): D.V. Sarwate
- Source: Electronics Letters, Volume 12, Issue 21, page: 572 –572
- DOI: 10.1049/el:19760435
- Type: Article
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Erratum: Optimum sufficient conditions for the stability of linear multivariable systems
- Author(s): J.M. Valenca
- Source: Electronics Letters, Volume 12, Issue 21, page: 572 –572
- DOI: 10.1049/el:19760436
- Type: Article
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