Online ISSN
1350-911X
Print ISSN
0013-5194
Electronics Letters
Volume 10, Issue 15, 25 July 1974
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Volume 10, Issue 15
25 July 1974
New silica-based low-loss optical fibre
- Author(s): D.N. Payne and W.A. Gambling
- Source: Electronics Letters, Volume 10, Issue 15, p. 289 –290
- DOI: 10.1049/el:19740231
- Type: Article
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p.
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–290
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A new type of silica-based optical fibre has been made from relatively cheap and abundant materials. The attenuation is very low over the entire range from the near ultraviolet to the gallium-arsenide-laser wavelength. The minimum loss of 2.7 dB/km occurs at 0.83 μm.
Linear antenna arrays with broadened nulls
- Author(s): D. Caswey
- Source: Electronics Letters, Volume 10, Issue 15, p. 291 –292
- DOI: 10.1049/el:19740232
- Type: Article
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p.
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–292
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The ‘small-sine’ taper has recently been proposed as a method of broadening a null in the radiation pattern of a linear array, and this is discussed. The nulls are compared with the broad null sectors obtained from a Dolph-Chebuy̅shev array.
Experimental verification of inhomogeneous field distribution in negatively bevelled high-voltage p-n junctions by means of photomultiplication
- Author(s): M. Bakowski
- Source: Electronics Letters, Volume 10, Issue 15, p. 292 –293
- DOI: 10.1049/el:19740233
- Type: Article
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–293
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Laser-beam-excited photocurrent measurements of the space-charge layer width close to the surface of a negatively bevelled diffused p-n junction revealed the existence of a well defined region of carrier multiplication at high applied voltages. The region is located within the space-charge layer on the highly doped side of the junction and close to the surface. The laser-light wavelength was 6328 Å and the beam diameter was about 5 μm. The experimental results are consistent with the theoretically predicted existence of a field maximum in this region of negatively bevelled p-n junctions.
Nullor representation of variable-frequency RC oscillator
- Author(s): P. Williams
- Source: Electronics Letters, Volume 10, Issue 15, page: 294 –294
- DOI: 10.1049/el:19740234
- Type: Article
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A recently proposed RC oscillator is represented in nullor form. By rearranging the nullors, it is shown that only one operational amplifier is required, instead of two. Means are proposed to overcome a bias problem inherent in the original design.
Error rates for biternary frequency modulation
- Author(s): T.T. Tjhung ; B.L. Wee ; T.S. Chia ; O.H. Tan
- Source: Electronics Letters, Volume 10, Issue 15, p. 295 –296
- DOI: 10.1049/el:19740235
- Type: Article
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–296
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The performance of a biternary f.m. system is investigated in the presence of additive Gaussian noise and receiver band limitation. The receiver bandpass-filter bandwidth is varied and, for each bandwidth, the frequency-deviation index that minimises the error probability is found. Comparisons with binary frequency modulation of the same data rate show that biternary frequency modulation can offer lower error rates only for receiver bandwidths less than 0.63 times the bit rate.
Double aperture blocking by two wavelength-sized feed-support struts
- Author(s): W.V.T. Rusch
- Source: Electronics Letters, Volume 10, Issue 15, p. 296 –297
- DOI: 10.1049/el:19740236
- Type: Article
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p.
296
–297
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Some results for i.f.r. ‘double-blocking’ configurations are given.
Wavefront visualisation of acoustic surface waves
- Author(s): J.M. Rouvaen ; E. Bridoux ; N. Gremillet ; R. Torguet ; P. Hartemann
- Source: Electronics Letters, Volume 10, Issue 15, p. 297 –299
- DOI: 10.1049/el:19740237
- Type: Article
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–299
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Acoustic surface waves (a.s.w.) propagating on yz-cut lithium niobate have been visualised by two imaging techniques. The wavefronts of straight-crested and convergent a.s.w. have been rendered visible on the screen of a storage oscilloscope.
Shielded rectangular microstrip disc resonators
- Author(s): R. Jansen
- Source: Electronics Letters, Volume 10, Issue 15, p. 299 –300
- DOI: 10.1049/el:19740238
- Type: Article
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p.
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–300
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A modification of the least-squares method is employed to calculate the resonance frequencies of shielded rectangular microstrip discs. Since the approach is a rigorous one, it includes endeffects and dispersion of the open-ended line, by which the configuration-can be identified. Results are given for quasi-TEM half- and whole-wave resonators and are compared with those obtained by simple line theory.
Optimisation of digital learning networks when applied to pattern recognition of mass spectra
- Author(s): T.J. Stonham and I. Aleksander
- Source: Electronics Letters, Volume 10, Issue 15, p. 301 –302
- DOI: 10.1049/el:19740239
- Type: Article
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A pattern classifier employing n-tuple sampling digital learning networks is analysed to show that redundancy can occur both due to the common occurrence of sets of n-tuples of the sample pattern and invariant points in the patterns. Some experimental results are given for a mass-spectrum classifier, where the system has been optimised by reconnection to reduce this redundancy.
Narrowband microwave filter using exponential lines
- Author(s): R.T. Irish
- Source: Electronics Letters, Volume 10, Issue 15, p. 302 –304
- DOI: 10.1049/el:19740240
- Type: Article
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–304
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The formation of narrow passbands within the attenuating frequency range of an exponential transmission-line system is discussed theoretically and the results applied to form a small, simply tuned, bandpass filter.
Low-attenuation properties of corrugated rectangular waveguide
- Author(s): A.M.B. Al-Hariri ; A.D. Olver ; P.J.B. Clarricoats
- Source: Electronics Letters, Volume 10, Issue 15, p. 304 –305
- DOI: 10.1049/el:19740241
- Type: Article
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p.
304
–305
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The attenuation coefficient of a corrugated rectangular waveguide is determined by the power-loss method, using approximations previously found to be successful. An error in earlier predictions by other workers is corrected, and the region identified in which the corrugated waveguide exhibits an attenuation advantage over comparable smooth-wall rectangular waveguide. However, the comparable circular corrugated waveguide is shown to be superior.
F.M. click rates: a simple derivation
- Author(s): N.M. Blachman and J.H. Roberts
- Source: Electronics Letters, Volume 10, Issue 15, p. 305 –307
- DOI: 10.1049/el:19740242
- Type: Article
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–307
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A firm foundation is given to Roberts's simple calculation of Rice's results that account for the effect of modulation on the click rate in f.m. reception.
Indium-phosphide c.w. transferred-electron amplifiers
- Author(s): R.M. Corlett ; I. Griffith ; J.J. Purcell
- Source: Electronics Letters, Volume 10, Issue 15, p. 307 –308
- DOI: 10.1049/el:19740243
- Type: Article
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–308
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J band c.w. low-noise indium-phosphide reflection amplifiers are described. An integral-heatsink technology has resulted in devices that can be operated c.w. at high bias levels. C.W. noise figures as low as 10.7 dB have been obtained at 14 GHz, and voltage-gain-bandwidth products of 3.1 GHz have been obtained. Measurements of impedance, noise and the temperature sensitivity of the gain are presented.
Sensitivity considerations of Smith's method for time-delay systems
- Author(s): B. Garland and J.E. Marshall
- Source: Electronics Letters, Volume 10, Issue 15, p. 308 –309
- DOI: 10.1049/el:19740244
- Type: Article
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p.
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–309
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The changes in time-delay system dynamics, when using a Smith predictor method, are discussed for mismatch of plant and model, drawing attention to the way in which behaviour due to mismatch in the delay-free part of the plant is affected by the time delay, and vice versa.
Numerical solution of lossy waveguides: t.l.m. computer program
- Author(s): S. Akhtarzad and P.B. Johns
- Source: Electronics Letters, Volume 10, Issue 15, p. 309 –311
- DOI: 10.1049/el:19740245
- Type: Article
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p.
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–311
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The transmission-line-matrix method is a time-domain numerical method for solving wave problems. The method uses a mesh of transmission lines to represent a propagation space, and the losses in the space are accounted for by making the transmission lines lossy. Lossy boundaries are simulated by imperfect boundary reflections on the transmission lines. A FORTRAN program implementing this technique is presented.
Implementation of digital matched filters in data receivers
- Author(s): G.B. Lockhart and P.B. Johns
- Source: Electronics Letters, Volume 10, Issue 15, p. 311 –312
- DOI: 10.1049/el:19740246
- Type: Article
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It is shown that analogue-filter and analogue-detector circuits in data receivers can be replaced by simple digital networks designed from truth-table specifications. A method of compiling truth tables from given received-signal probabilities is presented. An example illustrates an application to the reception of binary raised cosine signals in the presence of Gaussian noise.
Negabinary carry-look-ahead adder and fast multiplier
- Author(s): D.P. Agrawal
- Source: Electronics Letters, Volume 10, Issue 15, p. 312 –313
- DOI: 10.1049/el:19740247
- Type: Article
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–313
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A carry-look-ahead negabinary adder is proposed in the letter. It is shown that these adders make the design of a fast negabinary multiplier feasible.
Nonreflecting broadband capacitive termination for thin-wire antennas
- Author(s): B.D. Popović and M.B. Dragović
- Source: Electronics Letters, Volume 10, Issue 15, p. 314 –315
- DOI: 10.1049/el:19740248
- Type: Article
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p.
314
–315
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An efficient nonreflecting broadband capacitive termination for thin-wire antennas has been made, and has been analysed experimentally. Only the mounting of the termination onto a cylindrical metallic monopole antenna was considered, but the termination can also be used for other thin-wire-antenna structures.
Novel technique of making graded-refractive-index slab waveguides
- Author(s): Y.C. Cheng and W.D. Westwood
- Source: Electronics Letters, Volume 10, Issue 15, p. 315 –316
- DOI: 10.1049/el:19740249
- Type: Article
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–316
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A novel technique is presented of making graded-refractive-index slab waveguides for integrated optics. Using the dependence of the optical properties on sputtering conditions, any variation in refractive-index profile in a film can be produced.
Microwave radiometric measurements of the temperature inside a body
- Author(s): B. Enander and G. Larson
- Source: Electronics Letters, Volume 10, Issue 15, page: 317 –317
- DOI: 10.1049/el:19740250
- Type: Article
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Temperatures inside a body have been measured by a radiometer at 0.9 to 1.2 GHz with an antenna on the surface of the body. This technique to measure depth temperatures may have both industrial and medical applications.
Integrated class-B end stage
- Author(s): R.G. van Vliet
- Source: Electronics Letters, Volume 10, Issue 15, p. 317 –319
- DOI: 10.1049/el:19740251
- Type: Article
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The circuit described is made by a standard integrating process and is intended to be used as a booster in combination with a low-power operational amplifier or as the endstage of a new-design opamp. It has been designed to deliver a maximum output of 1 W and has extremely low crossover distortion.
Complete disturbance isolation in linear feedback systems
- Author(s): J.L. Willems
- Source: Electronics Letters, Volume 10, Issue 15, p. 319 –320
- DOI: 10.1049/el:19740252
- Type: Article
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p.
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–320
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In the letter, we consider a single-input single-output system with disturbances. The question is investigated whether there exists a state feedback such that the effect of disturbances is completely decoupled from the output. A simple criterion is derived that yields a necessary and sufficient condition.
Treatment of constraint equations in nodal analysis
- Author(s): T.B.M. Neill
- Source: Electronics Letters, Volume 10, Issue 15, p. 320 –322
- DOI: 10.1049/el:19740253
- Type: Article
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p.
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A method is illustrated by which a singular nodal-impedance matrix may be derived from a conceptual infinite nodal-admittance matrix representing constraint equations for circuit elements such as ideal operational amplifiers. This can greatly increase the possible range of application of nodal analysis.
Realisation of generalised far fields by reflector synthesis
- Author(s): A.P. Norris and B.S. Westcott
- Source: Electronics Letters, Volume 10, Issue 15, p. 322 –323
- DOI: 10.1049/el:19740254
- Type: Article
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p.
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–323
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A method of designing reflector surfaces by the geometrical-optics approximation is introduced, in which a given generalised far field is realised when the reflector is illuminated by a point source. The problem is shown to be reduced to solving a nonlinear 2nd-order partial differential equation of the Monge-Ampère type. A computed example is given.
Computer procedure for deriving ionospheric characteristic M(3000)F2 from h′(f) data
- Author(s): P.A. Bradley
- Source: Electronics Letters, Volume 10, Issue 15, p. 323 –324
- DOI: 10.1049/el:19740255
- Type: Article
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p.
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Standard procedures used at ionospheric observatories to determine the ionospheric characteristic M(3000)F2 by means of overlays or sliders applied to vertical-incidence ionograms are examined. Equations are presented to determine the corresponding values directly from numerical h′(f) data.
Admittance of a coaxial-to-circular waveguide junction
- Author(s): M. Razaz and J.B. Davies
- Source: Electronics Letters, Volume 10, Issue 15, p. 324 –326
- DOI: 10.1049/el:19740256
- Type: Article
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p.
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–326
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A least-squares boundary residual method is applied to an abrupt coaxial-to-circular waveguide transition. The junction capacitance is calculated and numerical results are presented.
Far-field emission patterns of single heterostructure GaAs lasers
- Author(s): G.D. Henshall and J.E.A. Whiteaway
- Source: Electronics Letters, Volume 10, Issue 15, p. 326 –327
- DOI: 10.1049/el:19740257
- Type: Article
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–327
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The emission patterns of single heterostructure lasers have been calculated as a function of the refractive-index Step between the p GaAs active region and the n GaAs substrate. The conclusions that higher n doping levels should produce better optical confinement and a wider far-field pattern are supported by experimental measurements, from which the refractive index can be deduced.
Detection of synchronism slip by shortened cyclic block codes
- Author(s): J.D. Martin
- Source: Electronics Letters, Volume 10, Issue 15, p. 327 –328
- DOI: 10.1049/el:19740258
- Type: Article
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Digital telemetry systems often employ start/stop data transmission and have to use codes of arbitrary length. A study has been started of the capability to detect synchronism slip of certain cyclic block codes of arbitrary length. Initial results are reported.
Erratum: Fast b.c.d. multiplier
- Author(s): D.P. Agrawal
- Source: Electronics Letters, Volume 10, Issue 15, page: 328 –328
- DOI: 10.1049/el:19740259
- Type: Article
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