Online ISSN
1350-911X
Print ISSN
0013-5194
Electronics Letters
Volume 13, Issue 12, 9 June 1977
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Volume 13, Issue 12
9 June 1977
Two-loop ternary adaptive delta modulation
- Author(s): T.S. Lamba ; M.N. Faruqui ; R. Steele
- Source: Electronics Letters, Volume 13, Issue 12, p. 337 –338
- DOI: 10.1049/el:19770247
- Type: Article
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p.
337
–338
(2)
A 2-loop ternary adaptive delta-modulation system is described which produces a peak s.n.r. of 20.5 dB, and for an s.n.r. of 15 dB, its dyamic range is 22dB when the input signal is RC shaped noise band limited to 2.5 kHz and the sampling rate is 8 kHz.
Implanation de sélénium dans le Ga1−xAlxAs (Implanation of selenium into Ga1−xAlxAs
- Author(s): P.N. Favennec ; L. Henry ; T. Janicki
- Source: Electronics Letters, Volume 13, Issue 12, p. 338 –339
- DOI: 10.1049/el:19770248
- Type: Article
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p.
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–339
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Par implantation d'ions de sélénium, de fines couches de type n sont obtenues dans le Ga0.71 Al0.29As. Pour les faibles doses, I'activité électrique est proche de 100%, et I'effet de l'implantation est comparable pour le GaAs et le Ga1−x Alx As. Les mêmes resultats sont obtenus en utilisant du Si3N4 ou de l'AIN comme film de protection.By implantation of selenium ions, thin n-type layers are obtained in Ga0.71Al0.29As. For small doses, the electrical activity is close to 100%. and the effect of the implantation is comparable for GaAs and Ga1−x AlxAs. The same results are obtained when using Si3N4 or AlN as a protective film.
Tunable Y-type waveguide power divider as standard mismatch
- Author(s): U. Stumper
- Source: Electronics Letters, Volume 13, Issue 12, p. 339 –340
- DOI: 10.1049/el:19770249
- Type: Article
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p.
339
–340
(2)
A method is proposed for generating standards of voltage standing wave ratio (v.s.w.r.) of values ≤ 2 by a waveguide device consisting of a Y-type junction matched to the input guide (power divider), with a tunable ratio of power division, an adjustable sliding short circuit and a matched load. A detailed analysis of errors is given, which considers the effects of a possible deviation of the symmetry of the junction and of the uncertainties in the determination of the reflection coefficient and of the position of the short circuit.
New codes for digital transmission
- Author(s): D. Munoz-Rodriguez and K.W. Cattermole
- Source: Electronics Letters, Volume 13, Issue 12, p. 340 –342
- DOI: 10.1049/el:19770250
- Type: Article
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p.
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–342
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Two new pseudoternary codes suitable for digital line transmission are proposed. Each is of 10B7T format. They have digital-sum variation, intersymbol interference, timing content and framing information comparable with 4B3T and MS43, respectively, but offer a higher information capacity for a given symbol rate.
Scattering amplitudes and crosspolarisation of ice particles
- Author(s): B.G. Evans and A.R. Holt
- Source: Electronics Letters, Volume 13, Issue 12, p. 342 –344
- DOI: 10.1049/el:19770251
- Type: Article
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342
–344
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The Fredholm-integral method is used to calculate accurate forward and backward scattering amplitudes of spheroidal ice particles for several frequencies in the range 4–30 GHz. Using a valuable oblique-angle rule, crosspolarisation at any elevation angle may be deduced. The implications of crosspolarisation on satellite paths are discussed.
Measurements of the close-to-carrier f.m. noise of pulsed InP t.e.o.s primed by an external oscillator
- Author(s): B.A. Prew
- Source: Electronics Letters, Volume 13, Issue 12, p. 344 –346
- DOI: 10.1049/el:19770252
- Type: Article
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344
–346
(3)
Experiments on phase-primed, pulsed InP transferred-electron oscillators show that the noise due to priming jitter can be reduced below the inherent noise level of the oscillator. Measurements are presented on the magnitude and spectrum of the oscillator noise.
Variation of attenuation and space diversity with elevation angle on 12 GHz satellite-to-ground radio paths
- Author(s): J.E. Allnutt
- Source: Electronics Letters, Volume 13, Issue 12, p. 346 –347
- DOI: 10.1049/el:19770253
- Type: Article
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p.
346
–347
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The results of a 6°-elevation-angle space-diversity experiment at a frequency of 11.6 GHz are reported, and is a comparison made with earlier results obtained by using the same sites at an elevation angle of 29.5°. For a given percentage time, more than double the path attenuation was measured at the lower elevation angle. Methods of predicting the attenuation and diversity gain at the lower elevation angle are discussed.
Modified mode propagation in optical waveguides
- Author(s): C.W. Pitt and L.M. Walpita
- Source: Electronics Letters, Volume 13, Issue 12, p. 347 –349
- DOI: 10.1049/el:19770254
- Type: Article
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–349
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The propagation constants of optical waveguides may be altered by applying a perturbing overlayer. Effectiyely-infinite-thickness superstates are compared with finite-thickness claddings; finite overlayers offer some advantages. The Langmuir-film technology is shown to meet the specification for the finite-cladding process.
Surface-acoustic-wave beam shaping with multistrip couplers
- Author(s): A. Ronnekleiv and K. Ingebrigtsen
- Source: Electronics Letters, Volume 13, Issue 12, p. 349 –351
- DOI: 10.1049/el:19770255
- Type: Article
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349
–351
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A method for tailoring surface-acoustic-wave beam profiles by using strip-length and phase-weighted multistrip couplers is presented. The design of and measurement on a 50 MHz-centre-frequency device is described.
Partial correction of transmission errors in d.p.c.m. without recourse to error correction coding
- Author(s): R. Steele ; D.J. Esdale ; D.J. Goodman
- Source: Electronics Letters, Volume 13, Issue 12, p. 351 –353
- DOI: 10.1049/el:19770256
- Type: Article
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A method for partially correcting transmission errors in a 1st-order d.p.c.m. system, without recourse to channel coding, is described. A simple detection algorithm based on the statistical properties of a sequence of differences between adjacent samples of a modified decoded sequence is used to identify the erroneous samples. Three different correcting algorithms are described. Substantial improvements in the decoded waveform are achieved, and, for a Markov input process, an error rate of 0.04% in the first and second most significant digits, an improvement in s.n.r. of 7dB is achieved.
Matrix description of scattering problems
- Author(s): R.J. Chignell and D. Munro
- Source: Electronics Letters, Volume 13, Issue 12, p. 353 –354
- DOI: 10.1049/el:19770257
- Type: Article
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p.
353
–354
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A scattering matrix is proposed that predicts the radiation patterns of antennas near to scattering objects. The method has been applied to the 2-dimensional problem of a line source adjacent to a square scatterer, and excellent agreement has been obtained with experimental results.
Algorithm for logic-circuit synthesis by using multiplexers
- Author(s): D.G. Whitehead
- Source: Electronics Letters, Volume 13, Issue 12, p. 355 –356
- DOI: 10.1049/el:19770258
- Type: Article
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p.
355
–356
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An algorithm is proposed for the synthesis of logic circuits by using multiplexers. Because the procedure described is numeric, any number of variables can be accommodated and the method is suited to computer solution.
Least-squares time-domain deconvolution for transversal-filter equalisers
- Author(s): D. Preis
- Source: Electronics Letters, Volume 13, Issue 12, p. 356 –357
- DOI: 10.1049/el:19770259
- Type: Article
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p.
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–357
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The N tap weights for a transversal-filter equaliser are calculated efficiently by solving a Toeplitz set of linear equations which represents the discrete-time convolution of filter and system impulse responses. Computation time is proportional to N2, approximately. Discrete Fourier transforms are not used. For many practical designs, the procedure is suited to small, desk-top programmable calculators, since it requires only multiplications and additions of real numbers and about 5N data storage registers.
Efficient pitch estimation for speech and music
- Author(s): W.H. Tucker and R.H.T. Bates
- Source: Electronics Letters, Volume 13, Issue 12, p. 357 –358
- DOI: 10.1049/el:19770260
- Type: Article
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p.
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–358
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An algorithm for estimating wideband pitch trajectories of acoustic signals is described. Its software implementation is fast, and real-time operation can be achieved by using inexpensive hardware. Results are presented for representative speech and music signals.
Preliminary test results on a 140 Mbit/s experimental optical-fibre transmission system
- Author(s): R.W. Berry ; R.C. Hooper ; B.R. White
- Source: Electronics Letters, Volume 13, Issue 12, p. 358 –360
- DOI: 10.1049/el:19770261
- Type: Article
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–360
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Results show that a bit rate of 140 Mbit/s should be obtainable over a 7 km link.
New type of varactor diode having strongly nonlinear C/V characteristics
- Author(s): Shozo Shirota ; Yoshiyuki Togawa ; Shigeo Kaneda
- Source: Electronics Letters, Volume 13, Issue 12, p. 360 –361
- DOI: 10.1049/el:19770262
- Type: Article
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–361
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Experimental studies of a new type of varactor diode consisting of a semiconductor multilayer structure have been performed. It is shown that such a varactor diode has much stronger nonlinearity in capacitance variation with applied bias voltage than does the conventional varactor, which will enable efficient generation of millimetre waves by direct frequency multiplication of high order.
Pulse compression in optical fibres
- Author(s): J.V. Wright and B.P. Nelson
- Source: Electronics Letters, Volume 13, Issue 12, p. 361 –363
- DOI: 10.1049/el:19770263
- Type: Article
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p.
361
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A shift in the emission wavelength of s.h. GaAs lasers has been observed during individual pulses. In conjunction with material dispersion, this leads to pulse compression after transmission through an optical fibre. The use of this device as a source in bandwidth measurements readily leads to erroneous conclusions when results are analysed.
Unidirectional transducer for lamb-wave delay lines
- Author(s): Kohji Toda and Yoshiaki Shinoda
- Source: Electronics Letters, Volume 13, Issue 12, p. 363 –364
- DOI: 10.1049/el:19770264
- Type: Article
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–364
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A new type of unidirectional transducer is proposed and demonstrated. This transducer consists of three electrode groups, one on the bottom surface. The others are interdigital electrode groups 60° out of phase and on the top surface. Better than 20 dB of directionally was obtained for the zeroth symmetrical mode of a Lamb wave.
Correlation between the optical output characteristics and the time-dependent behaviour of semiconductor lasers
- Author(s): O. Krumpholz and H. Gottsmann
- Source: Electronics Letters, Volume 13, Issue 12, p. 364 –365
- DOI: 10.1049/el:19770265
- Type: Article
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p.
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–365
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Various optical output characteristics of double-heterostructure lasers have been examined, together with the response of laser emission current pulses. Correlations between the two have been observed.
Fixed-lag smoother for digital channel equalisation
- Author(s): E. Dalle Mese ; D. Giuli ; M. Pellegrini
- Source: Electronics Letters, Volume 13, Issue 12, p. 366 –367
- DOI: 10.1049/el:19770266
- Type: Article
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p.
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–367
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A new equaliser for digital communication channels, which carries out a discrete-time fixed-lag smoothing of the state vector of the channel, modelled as a tapped delay line of finite length, is proposed. The smoothed estimate uses and improves the filtered estimate of the conventional Kalman-filter equaliser.
Optimisation of sensitivity and dynamic range of i.f.l.f. active filters
- Author(s): R. Schaumann ; R.E. Chalstrom ; K.R. Laker
- Source: Electronics Letters, Volume 13, Issue 12, p. 367 –368
- DOI: 10.1049/el:19770267
- Type: Article
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p.
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–368
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It is pointed out that the multiple-feedback topology for highorder active filters recently introduced by Perry, here labelled inverse f.l.f. (i.f.l.f.) topology, has significantly better dynamicrange properties than the otherwise equivalent ‘follow-the-leader-feedback’ (f.l.f.) structure. The procedure for optimising the signal-level capabilities and the sensitivity performance of i.f.l.f. circuits is presented.
Improved forms of threshold-logicfunction implementation
- Author(s): L.A.M. Bennett
- Source: Electronics Letters, Volume 13, Issue 12, p. 368 –370
- DOI: 10.1049/el:19770268
- Type: Article
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p.
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Improved forms of implementation for threshold-logic functions are described. These are based on a recently described cellular array, but require significantly fewer cells than previously described arrays. They could provide the basis of an economical way of producing threshold-logic elements.
Stress birefringence in single-mode fibres
- Author(s): O.G. Leminger
- Source: Electronics Letters, Volume 13, Issue 12, p. 370 –371
- DOI: 10.1049/el:19770269
- Type: Article
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p.
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The core and cladding of a glass fibre exposed to axial tension become optically uniaxial. The modified characteristic equation is presented and, for the fundamental mode, the changes in the most important propagation parameters have been calculated.
Tracking sensitivity: a practical algorithm
- Author(s): T. Neumann and D. Agnew
- Source: Electronics Letters, Volume 13, Issue 12, p. 371 –372
- DOI: 10.1049/el:19770270
- Type: Article
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p.
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A new algorithm for tracking sensitivity, based on a matrix power series, is given. It requires less computation than previous methods, but the allowable range of the global parameter is restricted.
Analogue c.c.d. correlator using monolithic m.o.s.t. multipliers
- Author(s): J. Mavor ; J.W. Arthur ; P.B. Denyer
- Source: Electronics Letters, Volume 13, Issue 12, p. 373 –374
- DOI: 10.1049/el:19770271
- Type: Article
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A 32-stage analogue correlator has been hybridised by using a multitapped c.c.d. delay line and m.o.s.t. multipliers fabricated on the same silicon chip. A multiple-port sample–hold system has been adopted for storage of the reference signal, thereby allowing it to be refreshed continuously. The viability of a design for a fully analogue monolithic c.c.d. correlator is established.
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