Online ISSN
1350-911X
Print ISSN
0013-5194
Electronics Letters
Volume 17, Issue 11, 28 May 1981
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Volume 17, Issue 11
28 May 1981
Novel electro-optical feedback technique for noise and distortion reduction in high-quality analogue optical transmission video signals
- Author(s): A. van de Grijp ; J.C. Koopman ; L.J. Meuleman ; A.J.A. Nicia ; E. Roza ; J.H.C. van Heuven
- Source: Electronics Letters, Volume 17, Issue 11, p. 361 –362
- DOI: 10.1049/el:19810253
- Type: Article
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p.
361
–362
(2)
The use of electro-optical feedback in an analogue optical transmitter makes it possible to reduce both noise and distortion. Automatic gain control by means of an electronically controlled optical attenuator maintains linearity of the baseband amplifier. The performance of this high-quality optical video link and of the optical attenuator is presented.
Additional losses and time delay fluctuations of TE11 modes in curved circular waveguides-application to feeder antennas
- Author(s): C. Fray ; I. Andritsos ; A. Papiernik
- Source: Electronics Letters, Volume 17, Issue 11, p. 362 –364
- DOI: 10.1049/el:19810254
- Type: Article
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p.
362
–364
(3)
The additional losses and fluctuations in time delay in TE11 operating curved circular waveguides have been determined. The results obtained reveal that additional losses are less than 0.1 dB and time delay fluctuations are less than 0.5 ns at a bend exit (curvature radius one metre). This permits the use of nonrigid circular waveguides as feeders to antennas in communication systems operating at frequencies above 10 GHz.
Magnitude and phase in thermal wave imaging
- Author(s): A. Lehto ; J. Jaarinen ; T. Tiusanen ; M. Jokinen ; M. Luukkala
- Source: Electronics Letters, Volume 17, Issue 11, p. 364 –365
- DOI: 10.1049/el:19810255
- Type: Article
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p.
364
–365
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In thermal wave imaging on solids both magnitude and phase angle are used. However, a comparison between theoretical and experimental results is lacking even for the simple case of an air-backed metal plate. In the letter we present measurements and point out the difference between sinusoidal and square-wave intensity modulation.
Axial ratio of balanced helical antenna and ellipticity measurement of incident wave
- Author(s): J. Yamauchi and H. Nakano
- Source: Electronics Letters, Volume 17, Issue 11, p. 365 –366
- DOI: 10.1049/el:19810256
- Type: Article
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p.
365
–366
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The axial ratio of a balanced helical antenna shows a wavelike change with increase in the number of helical turns The ellipticity measurement of an incident wave is carried out using the balanced helical antenna with excellent axial ratio regarded as being entirely circular polarisation.
CW operation of 1.5 ~ 1.6 μm wavelength GaInAsP/InP buried-heterostructure integrated twin-guide laser with distributed Bragg reflector
- Author(s): K. Kobayashi ; K. Utaka ; Y. Abe ; Y. Suematsu
- Source: Electronics Letters, Volume 17, Issue 11, p. 366 –368
- DOI: 10.1049/el:19810257
- Type: Article
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p.
366
–368
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A 1.5 ~ 1.6 μm GaInAsP/InP buried-heterostructure integrated twin-guide laser with distributed Bragg reflector (BH-DBR-ITG laser) was realised, for the first time, and CW operation was achieved up to 255 K. Single-wavelength operation was obtained at temperatures between 228 K and 245 K with the temperature dependence of lasing wavelength of 10 Å/deg. At 233 K, the threshold current, the output power and the differential quantum efficiency were 110 mA, 2.2 mW and 4.8%/facet, respectively.
Single-wavelength operation of 1.53 μm GaInAsP/InP buried-heterostructure integrated twin-guide laser with distributed Bragg reflector under direct modulation up to 1 GHz
- Author(s): K. Utaka ; K. Kobayashi ; F. Koyama ; Y. Abe ; Y. Suematsu
- Source: Electronics Letters, Volume 17, Issue 11, p. 368 –369
- DOI: 10.1049/el:19810258
- Type: Article
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p.
368
–369
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1.53 μm GaInAsP/InP buried-heterostructure integrated twin-guide laser with distributed Bragg reflector (BH-DBR-ITG laser) was directly modulated with microwave modulation current superimposed on a DC bias which was fixed at 1.1 times the threshold current, and single-wavelength operation was experimentally confirmed with a modulation frequency up to 1 GHz and a modulation depth of 100%.
Reducing radiation loss of tilts in dielectric optical waveguides
- Author(s): E.-G. Neumann
- Source: Electronics Letters, Volume 17, Issue 11, p. 369 –371
- DOI: 10.1049/el:19810259
- Type: Article
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p.
369
–371
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It is proposed to reduce the radiation loss of an optical wave-guide tilt by increasing the refractive index on the inner side, or by decreasing it on the outer side of the tilt By microwave model experiments it is shown that the method proposed is effective.
Measurement of refractive-index profile of optical-fibre preform by means of spatial filtering
- Author(s): D. Peri and P.L. Chu
- Source: Electronics Letters, Volume 17, Issue 11, p. 371 –372
- DOI: 10.1049/el:19810260
- Type: Article
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p.
371
–372
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It is shown that a slit with appropriately designed width can be used as a spatial filter to yield the optimum resolution in the measurement of the deflection function of an optical-fibre preform
Broadbanding the quarter-wave transformer using two parallel stubs
- Author(s): A. Podcameni and L.F. Conrado
- Source: Electronics Letters, Volume 17, Issue 11, p. 372 –374
- DOI: 10.1049/el:19810261
- Type: Article
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p.
372
–374
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The quarter-wave transformer is broadbanded by including two parallel, open and short, eighth-wavelength stubs. A bandpass transfer function results and Butterworth or Cheby̅shev designs can be achieved. Tables for practical use are presented.
Stability of reduced model obtained by truncation
- Author(s): K.S. Yeung
- Source: Electronics Letters, Volume 17, Issue 11, p. 374 –375
- DOI: 10.1049/el:19810262
- Type: Article
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p.
374
–375
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It is shown that, for well-damped systems, reduced models obtained by truncating high-order terms of its characteristic polynomial are stable. For oscillatory systems this may not always be the case, as is demonstrated by an example.
Application of Routh's criterion to test for positive real functions
- Author(s): K.S. Yeung
- Source: Electronics Letters, Volume 17, Issue 11, p. 375 –376
- DOI: 10.1049/el:19810263
- Type: Article
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p.
375
–376
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The letter shows that the entire test for positive real functions can be carried out by the exclusive use of Routh's criterion.
Thermal noise emission of a lossy material for a TEM propagation
- Author(s): J.J. Fabre and Y. Leroy
- Source: Electronics Letters, Volume 17, Issue 11, p. 376 –377
- DOI: 10.1049/el:19810264
- Type: Article
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p.
376
–377
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New methods of computation of the thermal noise signals emitted by homogeneous and multilayered lossy materials, for a TEM propagation are presented. In particular, the noise contribution of the different subvolumes and the case of non-uniform temperature repartition are studied, taking into account correlation and refractive-index variation effects.
Electron Hall mobility calculations and alloy scattering in Ga0.47In0.53As
- Author(s): Y. Takeda ; M.A. Littlejohn ; J.R. Hauser
- Source: Electronics Letters, Volume 17, Issue 11, p. 377 –379
- DOI: 10.1049/el:19810265
- Type: Article
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p.
377
–379
(3)
Electron Hall mobilities are calculated by the iterative technique in Ga0.47In0.53As. From the curve fitting to the most recent experimental data over a wide range of temperature, the alloy scattering potential close to the Phillips electronegativity difference is derived. The alloy scattering-limited mobility has a temperature dependence of T−1/2 and shows no anomalous behaviour.
Maximum single frequency input power in a long optical fibre determined by stimulated Brillouin scattering
- Author(s): N. Uesugi ; M. Ikeda ; Y. Sasaki
- Source: Electronics Letters, Volume 17, Issue 11, p. 379 –380
- DOI: 10.1049/el:19810266
- Type: Article
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p.
379
–380
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The experimental results of stimulated Brilloum scattering in about a 4 km fibre are reported. The pumping wavelength is 0.71 μm. The Brilloum shift frequency was measured to be about 25 GHz. The transmitted power was found to be constant, when the input power exceeds about 14.8 dBm. The saturated transmitted power was 0.5 dBm, which corresponded with the output when 14.8 dBm input power was coupled and only linear fibre loss (about 4.0 dB/km) was assumed.
Frequency mixing in fibre-optic interferometer systems
- Author(s): K.P. Koo and E.F. Carome
- Source: Electronics Letters, Volume 17, Issue 11, p. 380 –382
- DOI: 10.1049/el:19810267
- Type: Article
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p.
380
–382
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Frequency mixing effects introduced by the photodetectors in optical fibre interferometer systems have been examined experimentally. Thin film PVF2 strips attached to the single-mode-fibre interferometer arms served as voltage-driven phase modulators. These mixing effects, while possibly limiting the dynamic range of fibre sensor systems, may be used for frequency multiplexing.
Stability of aluminium-polysilicon photovoltaic junctions
- Author(s): D.J. Thomson ; M.A. Matiowsky ; H.C. Card
- Source: Electronics Letters, Volume 17, Issue 11, p. 382 –383
- DOI: 10.1049/el:19810268
- Type: Article
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p.
382
–383
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Aluminium p-type polysilicon contacts display a rectifying behaviour which exhibits an aging towards reduced Schottky barrier heights and increased n-values or ideality factors. The time scale for this aging process increases dramatically with the thickness of the aluminium layer in the range 100–1000 Å, and the overall behaviour is in accordance with the model of Ponpon and Siffert for transport of oxygen through the aluminium film to the polysilicon surface.
Perturbation approach to design of circularly polarised microstrip antennas
- Author(s): Y.T. Lo and W.F. Richards
- Source: Electronics Letters, Volume 17, Issue 11, p. 383 –385
- DOI: 10.1049/el:19810269
- Type: Article
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p.
383
–385
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The letter describes a simple but accurate method to determine the critical dimensions needed to produce circular polarisation for nearly square and nearly circular microstrip antennas.
Far-field profiling of multimode optical fibres
- Author(s): W. Freude
- Source: Electronics Letters, Volume 17, Issue 11, p. 385 –387
- DOI: 10.1049/el:19810270
- Type: Article
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p.
385
–387
(3)
Using a recently published relation between far-field intensity and refractive index profile a monotonically decreasing equivalent profile is calculated from measured far-field data. The resulting smooth function may be fitted to composite or multiple α-profiles very well.
Low-frequency noise spectrum of GaAs FETs
- Author(s): J. Graffeuil
- Source: Electronics Letters, Volume 17, Issue 11, p. 387 –388
- DOI: 10.1049/el:19810271
- Type: Article
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p.
387
–388
(2)
In GaAs MESFETs low-frequency noise spectra of various forms are observed. In some cases they are of the form (A/f) {1−(2/π) tan−1 (ωτ0)}. The bias dependence of A and τ0 is attributed to the variation in channel thickness. Usefulness of low-frequency spectra for MESFET design and application is outlined.
Polarisation maintenance in circularly birefringent fibres
- Author(s): A.J. Barlow and D.N. Payne
- Source: Electronics Letters, Volume 17, Issue 11, p. 388 –389
- DOI: 10.1049/el:19810272
- Type: Article
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p.
388
–389
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The feasibility of twisted circularly birefringent polarisation maintaining fibres is investigated. It is shown that the twist rate required to provide immunity from external effects is excessively large.
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