Online ISSN
1350-911X
Print ISSN
0013-5194
Electronics Letters
Volume 3, Issue 6, June 1967
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Volume 3, Issue 6
June 1967
Maximum and resonant gains in parametric amplifiers
- Author(s): D.S. James and F.J. Hyde
- Source: Electronics Letters, Volume 3, Issue 6, page: 229 –229
- DOI: 10.1049/el:19670176
- Type: Article
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p.
229
(1)
It has generally been assumed that, in three-frequency negative-resistance parametric amplifiers incorporating resonant circuits, maximum gain is obtained when the signal and idler circuits are resonant. It is shown that this assumption is not, in general, justified.
Distortion of speech by quantising
- Author(s): D.L. Richards
- Source: Electronics Letters, Volume 3, Issue 6, p. 230 –231
- DOI: 10.1049/el:19670177
- Type: Article
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–231
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The proper function of a communication system is to produce, at its output, any one of a number of acceptable alternatives for the exact form of the input message. Certain changes during transmission can therefore be accepted. This principle has been applied to the transmission of speech by a quantised system.
Variationally computed antenna impedances and accuracy of resulting current distributions
- Author(s): R.W.P. King and J. Galejs
- Source: Electronics Letters, Volume 3, Issue 6, p. 231 –233
- DOI: 10.1049/el:19670178
- Type: Article
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p.
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–233
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The Criterion proposed by Galejs for establishing the accuracy of a given approximate distribution of Current in an antenna is shown to be unreliable. Conclusions based on an erroneous comparison of numerical and experimental results are corrected.
Transistor transit-time oscillator
- Author(s): G.T. Wright
- Source: Electronics Letters, Volume 3, Issue 6, p. 234 –235
- DOI: 10.1049/el:19670179
- Type: Article
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p.
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–235
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The letter describes the current/voltage characteristics of a transistor structure when controlled by space-charge and transit-time effects. It is shown that large negative conductances can be obtained at high frequencies. Operation is not limited by transit-time effects, and efficient high-power working at centimetre and millimetre wavelengths should be possible.
Reciprocity in silicon Schottky-barrier diodes
- Author(s): Y. Anand and W.E. Doherty
- Source: Electronics Letters, Volume 3, Issue 6, p. 236 –237
- DOI: 10.1049/el:19670180
- Type: Article
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–237
(2)
Reciprocity has been examined at X band for low-noise silicon Schottky-barrier diodes by measuring the forward (r.f. to i.f.) and reverse (i.f. to r.f.) conversion losses by the heterodyne method. Reciprocity held for the silicon Schottky-barrier diodes, proving that their low conversion-loss behaviour is due to the nonlinear barrier resistance and not to parametric amplification caused by a nonlinear barrier capacitance. For comparison, silicon epitaxial point-contact and germanium point-contact diodes were also examined.
Binary uniform codes
- Author(s): S.M. Reddy
- Source: Electronics Letters, Volume 3, Issue 6, page: 237 –237
- DOI: 10.1049/el:19670181
- Type: Article
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An algorithm to construct all linear binary uniform codes is given. The algorithm makes use of block codes due to Macdonald.
Spectral density of random signals corrupted by multiplicative noise
- Author(s): S.G. Loo
- Source: Electronics Letters, Volume 3, Issue 6, page: 238 –238
- DOI: 10.1049/el:19670182
- Type: Article
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238
(1)
A simple method of evaluating the spectral density of stationary random signals corrupted by multiplicative noise is presented. It is assumed that the multiplicative noise is also stationary, and that it is statistically independent of the signal.
Spectral factorisation by means of augmented factors
- Author(s): S.G. Loo
- Source: Electronics Letters, Volume 3, Issue 6, p. 238 –239
- DOI: 10.1049/el:19670183
- Type: Article
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–239
(2)
A method of factorising rational spectral matrixes by means of a series of linear transformations, and by augmenting it with matrix factors, is presented. An example illustrating the method is included.
Properties of state matrixes representing time-invariant lossless nports
- Author(s): F.M. Reza and N.K. Bose
- Source: Electronics Letters, Volume 3, Issue 6, p. 239 –240
- DOI: 10.1049/el:19670184
- Type: Article
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p.
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–240
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The class of all finite, time-invariant, linear, passive, lossless networks which have state-equation representations are considered. The necessary and sufficient conditions for the state-equation matrixes to represent such networks are derived, and the consequences of reciprocity and non-reciprocity are brought out.
Sensitivity properties of linear systems
- Author(s): H. Nicholson
- Source: Electronics Letters, Volume 3, Issue 6, p. 241 –242
- DOI: 10.1049/el:19670185
- Type: Article
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p.
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–242
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The sensitivity of the properties of linear dynamic systems produced by matrix-element change is considered using Sylvester's expansion theorem. The methods illustrate the basic role of the constituent matrixes associated with the theory of linear systems. The inverse-eigenvalue-sensitivity problem relevant to control-system design is also illustrated.
Sufficient condition of the asymptotic stability of nonlinear sampling systems
- Author(s): F. Laurent
- Source: Electronics Letters, Volume 3, Issue 6, page: 242 –242
- DOI: 10.1049/el:19670186
- Type: Article
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p.
242
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The study of quadratic Lyapunov functions leads to a sufficient condition for the asymptotic stability of nonlinear sampling systems.
Charged-particle production in the electrogasdynamic generator
- Author(s): A.G. Bailey
- Source: Electronics Letters, Volume 3, Issue 6, p. 242 –243
- DOI: 10.1049/el:19670187
- Type: Article
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p.
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–243
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Experiments have been performed on an electrogasdynamic generator utilising charged water droplets produced by using an atomiser in an electric-field region. This method of charged-particle production may offer certain advantages over corona systems. The mechanism of induction charging is well understood6 and Operates with a particularly simple electrode geometry. Problems of electrode errosion do not arise.
Phase relation between offices in a mutually synchronised system
- Author(s): H. Inose ; H. Fujisaki ; T. Saito
- Source: Electronics Letters, Volume 3, Issue 6, p. 243 –244
- DOI: 10.1049/el:19670188
- Type: Article
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p.
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–244
(2)
Although a common system frequency is established in mutually synchronised system, some phase difference exists between offices. Analyses of the phase difference and the system-frequency jump due to the change in transmission delay are given, assuming the sawtooth characteristics for the phase comparators.
Wave propagation in a moving plasma
- Author(s): B.R. Chawla and H. Unz
- Source: Electronics Letters, Volume 3, Issue 6, p. 244 –246
- DOI: 10.1049/el:19670189
- Type: Article
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–246
(3)
This letter comments on previous work by Scarf on wave propagation in a moving plasma and also adds new results.
Dependence of the propagation loss in laser ranging systems on the meteorological visibility and target/receiver range
- Author(s): W.M. Nixon ; J.L. Clarke ; J.E. Copeland
- Source: Electronics Letters, Volume 3, Issue 6, p. 246 –247
- DOI: 10.1049/el:19670190
- Type: Article
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–247
(2)
The relationship between meteorological visual range and the propagation loss in laser beams has been studied at wavelengths of 0.6943 μm and 1.065 μm. For visual ranges of 1–10 km, the laser propagation loss is found to be compatible with that predicted by existing equations relating extinction coefficient to visual range and wavelength. The inverse-square law relating received signal strength to target/receiver range is confirmed.
High-frequency current oscillations in vapour-deposited CdS thin films
- Author(s): I.M. Mason and W.E.J. Farvis
- Source: Electronics Letters, Volume 3, Issue 6, p. 247 –248
- DOI: 10.1049/el:19670191
- Type: Article
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p.
247
–248
(2)
High-frequency small-amplitude current modulation has been observed in a vapour-deposited CdS thin film subjected to high electric stress in the ruby substrate plane. The possibility that this modulation may be attributed to travelling-charge domains formed by acoustoelectric interaction in the acoustic waveguide system is discussed.
200 MHz counter/shift-register stage
- Author(s): J.S. Brothers and R.C. Foss
- Source: Electronics Letters, Volume 3, Issue 6, p. 248 –250
- DOI: 10.1049/el:19670192
- Type: Article
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p.
248
–250
(3)
The letter describes the principles of operation and practical design of a 200 MHz counter/shift register with only 50mW power consumption. The performance is achieved by using stacked long-tailed pairs to realise a double-rank or master–slave logic function. It is shown that this circuit arrangement is such as to fully exploit present integrated-circuit-fabrication techniques.
Tolerance of nonlinearities in time-varying optimal systems
- Author(s): B.D. Anderson and J.B. Moore
- Source: Electronics Letters, Volume 3, Issue 6, p. 250 –251
- DOI: 10.1049/el:19670193
- Type: Article
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p.
250
–251
(2)
Nominally linear optimal-control regulating systems are examined with a view to assessing the amount of nonlinearity which can be tolerated in the input transducer. Using a suitable Lyapunov function, it is found that a large degree of nonlinearity will not disturb the stability of the system.
Radiation from surface-wave antennas
- Author(s): J.B. Andersen
- Source: Electronics Letters, Volume 3, Issue 6, p. 251 –252
- DOI: 10.1049/el:19670194
- Type: Article
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p.
251
–252
(2)
A recent paper by James on radiation from a dielectric antenna seems to contain some erroneous statements concerning the application of radiation formulas. These erroneous statements are pointed out and related to other theories of surface-wave antennas.
Wide bandwidth Butler matrix network
- Author(s): P.E.K. Chow and D.E.N. Davies
- Source: Electronics Letters, Volume 3, Issue 6, p. 252 –253
- DOI: 10.1049/el:19670195
- Type: Article
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p.
252
–253
(2)
Butler matrix networks, used for forming multiple beams from linear aerial arrays, are limited in their bandwidth of operation by their requirement for components with constant values of phase shift over this bandwidth. This letter describes a method for designing such networks for wide-bandwidth operation by employing particular combinations of directional couplers and hybrid tees, thus eliminating the need for separate phase shifts. Results are given for a 4×4port matrix operating over an octave range of frequency.
Longitudinal resonances of plasma surface waves in noble gases
- Author(s): I. Zhelyazkov ; T. Stoytchev ; N. Nikolov
- Source: Electronics Letters, Volume 3, Issue 6, p. 253 –255
- DOI: 10.1049/el:19670196
- Type: Article
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–255
(3)
The excitation and propagation of axially symmetric surface plasma waves along a plasma column are investigated at frequencies from 100 to 200MHz. There are experimentally obtained dispersion curves for such waves in gas-discharge plasmas of He, Ne and Kr at pressures of 0.03–0.20torr. The results are in good agreement with the theory of surface waves in quasistatic approximation.
Elliptic digital filters
- Author(s): A.G. Constantinides
- Source: Electronics Letters, Volume 3, Issue 6, p. 255 –256
- DOI: 10.1049/el:19670197
- Type: Article
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255
–256
(2)
A synthesis procedure is given for elliptic digital filters of order 2q, q=1, 2, 3…. The pulse transfer function is obtained in the form of biquadratic products in z−1. An example illustrates how this method is used to synthetise an elliptic digital filter.
Harmonic stabilisation of a.c. servos
- Author(s): D.R. Wilson
- Source: Electronics Letters, Volume 3, Issue 6, p. 256 –257
- DOI: 10.1049/el:19670198
- Type: Article
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p.
256
–257
(2)
A simple method of stabilising an a.c. servo has been demonstrated in a recent laboratory experiment.
Theoretical analysis of the monolithic-crystal filter
- Author(s): M. Redwood and N.H.C. Reilly
- Source: Electronics Letters, Volume 3, Issue 6, p. 257 –258
- DOI: 10.1049/el:19670199
- Type: Article
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p.
257
–258
(2)
Two or more resonant regions in a piezoelectric material may be coupled mechanically by regions operating as mechanical waveguides below cutoff. A method of analysis based on the piezoelectric and mechanical equations is described and illustrated with a typical attenuation/frequency characteristic and equivalent electrical circuit of a 3-resonator filter.
Behaviour of n-type gallium arsenide in strong microwave fields
- Author(s): G.O. Acket and H.T. Lam
- Source: Electronics Letters, Volume 3, Issue 6, p. 258 –259
- DOI: 10.1049/el:19670200
- Type: Article
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p.
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–259
(2)
Results are presented concerning the change of attenuation and generation of harmonics in n-type gallium arsenide, subjected to a strong microwave electric field.
Free oscillations in nonlinear oscillating circuit
- Author(s): A.Y. Spasov
- Source: Electronics Letters, Volume 3, Issue 6, p. 259 –261
- DOI: 10.1049/el:19670201
- Type: Article
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p.
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–261
(3)
An oscillating circuit with nonlinear capacitance in a free oscillating régime is examined. Assuming that the circuit has small losses and high Q factor, a formula is obtained for the envelope of the free oscillations which differs from the exponential. The greater the influence of the nonlinear element the greater is this difference. Satisfactory coincidence of theoretical with experimental results is obtained.
Simulation study of a two-derivative hill climber
- Author(s): D.W. Clarke and K.R. Godfrey
- Source: Electronics Letters, Volume 3, Issue 6, p. 261 –263
- DOI: 10.1049/el:19670202
- Type: Article
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p.
261
–263
(3)
A dual-estimation hill climber, using a 3-level msequence perturbation signal, has been simulated on a digital computer, and it has been demonstrated that the hill climber works as predicted theoretically under ideal conditions (i.e. on a quadratic hill without noise). The simulation has also been used to investigate the performance of the hill climber on (a) nonquadratic hills, (b) in the presence of noise and (c) for the case where the system settling time has been taken as too small, and it has been found that the hill climber still performs satisfactorily provided certain precautions are taken.
Optical breakdown thresholds in helium
- Author(s): J.W. Gardner
- Source: Electronics Letters, Volume 3, Issue 6, p. 264 –265
- DOI: 10.1049/el:19670203
- Type: Article
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p.
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–265
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The breakdown of helium gas at the focus of a Q-switched laser is considered theoretically. Calculated values of the optical breakdown flux F, for various atomic densities N, are compared with Minck's experimental values. For F>5×1030 photons per cm2s−1 results appear to be independent of the radiation coherence, and a tentative explanation is advanced for this.
Derivation of certain nonlinear circuit equations
- Author(s): J.O. Flower and F.J. Evans
- Source: Electronics Letters, Volume 3, Issue 6, page: 265 –265
- DOI: 10.1049/el:19670204
- Type: Article
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p.
265
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An alternative derivation of certain differential equations describing nonlinear electrical circuits, proposed originally by Brayton and Moser, is presented and extended to show the inclusion of Current sources.
Transmission of ultrashort coherent pulses through the ionosphere
- Author(s): A. Bramley
- Source: Electronics Letters, Volume 3, Issue 6, page: 266 –266
- DOI: 10.1049/el:19670205
- Type: Article
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p.
266
(1)
A study is made of scattering and absorption of ultrashort coherent radiation pulses when they pass through an electron gas, such as occurs in the ionised upper layers of the atmosphere.
Measurement of small phase changes with the aid of an oscilloscope with a differential input
- Author(s): M.T. Hills
- Source: Electronics Letters, Volume 3, Issue 6, page: 267 –267
- DOI: 10.1049/el:19670206
- Type: Article
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p.
267
(1)
A simple technique is described for measuring the phase difference between two sine waves with the aid of a differential input oscilloscope. If the amplitude of one of the inputs is adjusted so that the difference between the two signals is minimal, it is shown that the ratio of this amplitude to the amplitude of the other input by itself gives the sine of the phase difference.
Operational calculus of random functions and their statistics
- Author(s): H.M. Nelson
- Source: Electronics Letters, Volume 3, Issue 6, p. 267 –268
- DOI: 10.1049/el:19670207
- Type: Article
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p.
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–268
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By regarding random functions as matrixes with discrete columns and an infinity of rows, an operational calculus of random functions and their statistics can be developed. This calculus is applicable either to time-invariant or time-varying linear systems, and it greatly simplifies the derivation of relationships between either the functions themselves or their statistics.
ZnTe and InSb thin-film transistors
- Author(s): I. SpîNulescu-Carnaru
- Source: Electronics Letters, Volume 3, Issue 6, p. 268 –269
- DOI: 10.1049/el:19670208
- Type: Article
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The results of transistors on ZnTe and InSb thin films are given. The t.f.t. gm transconductance obtained varied between 5 and 12mA/V. The input impedance of t.f.t. on ZnTe and InSb is high (>109Ω).
Numerical results for diffraction by a parallel-plate waveguide
- Author(s): S.W. Lee and R. Mittra
- Source: Electronics Letters, Volume 3, Issue 6, p. 269 –270
- DOI: 10.1049/el:19670209
- Type: Article
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p.
269
–270
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In designing waveguide phased arrays, it is often found useful to have the knowledge of the diffraction pattern and excitation coefficients of a semi-infinite parallel-plate waveguide illuminated by a plane wave. To the best of these authors' knowledge, numerical results for the above quantities have not appeared elsewhere in the literature. It is the purpose of this note to present some calculated results for the above quantities, with the guide dimension and the incident angle of the plane wave as parameters.
Rhombic aerial with feedback
- Author(s): D. Taylor and R. Bukenya
- Source: Electronics Letters, Volume 3, Issue 6, p. 270 –271
- DOI: 10.1049/el:19670210
- Type: Article
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p.
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–271
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It is shown that the termination in the case of a travelling-wave aerial, e.g. a rhombic, may be removed and replaced by a feedback loop to utilise a larger proportion of the total power. This involves the use of a hybrid transformer or magic tee at the aerial input.
Cerenkov radiation in a magnetoionic medium
- Author(s): S.R. Seshadri
- Source: Electronics Letters, Volume 3, Issue 6, p. 271 –274
- DOI: 10.1049/el:19670211
- Type: Article
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p.
271
–274
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For certain values of parameters, a point charge moving with uniform velocity parallel to the magnetostatic field in an unbounded magnetoionic medium excites two modes. In a recent investigation, Kurdyumov has concluded that of these two modes, one is associated with emission of energy and the other with absorption. Theoretical arguments as well as experimental evidence are advanced in order to establish that both the modes, contrary to the conclusion of Kurdyumov, are associated with emission of energy.
Double-pumped low-noise parametric down-convertor
- Author(s): V. Kempe
- Source: Electronics Letters, Volume 3, Issue 6, p. 274 –276
- DOI: 10.1049/el:19670212
- Type: Article
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–276
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It is shown how a low-noise parametric down-convertor can be realised by using two incommensurable pumping generators. The properties of the system, such as gain-bandwidth product and minimum-noise temperature, are discussed.
Delay time between the current pulse and the light emission of GaAs laser diodes
- Author(s): G. Guekos and M.J.O. Strutt
- Source: Electronics Letters, Volume 3, Issue 6, p. 276 –277
- DOI: 10.1049/el:19670213
- Type: Article
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p.
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–277
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The delay time td between the onset of the current pulse and that of the light emission has been measured above threshold as a function of the diode current I for several GaAs laser diodes at a temperature of about 77° K. When plotted against In [I/(I—Ith)], td decreases with increasing current, but does not obey the linear relation found by others. The values of td measured near threshold are in satisfactory agreement with the spontaneous emission time calculated from theory. Although the measured curves are all of the same shape, differences of td exist among the diodes, which are supposed to be caused by the presence of traps.
Simulation of a high-order, charge-storage-diode multiplier on an analogue computer
- Author(s): P.W.C. Chilvers and K. Foster
- Source: Electronics Letters, Volume 3, Issue 6, p. 277 –278
- DOI: 10.1049/el:19670214
- Type: Article
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p.
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–278
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A harmonic generator using a charge-storage diode as the active element has been simulated on an analogue computer. Photographs have been obtained of the various waveforms in the circuit, and it has been found that under Certain Circumstances multiple transitions can occur. The method leads to a better understanding of the operation and the design criteria for these circuits.
Improved theory of propagation through slotted circular waveguide
- Author(s): P.J.B. Clarricoats and A.A. Oliner
- Source: Electronics Letters, Volume 3, Issue 6, p. 279 –281
- DOI: 10.1049/el:19670215
- Type: Article
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p.
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The letter describes two types of correction to existing expressions for the radial-line susceptance arising from a uniform slot in the wall of a circular waveguide. These expressions lead to much more accurate values for the propagation coefficients of leaky-waveguide modes. For the H11 mode, favourable comparison is made between computed results and experimental results obtained previously by Harrington. Corrections to the susceptance expressions are presented for H0, E0, H1 and E1 radial-line modes, and, for the azimuthal-dependent modes, two slot positions are considered.
Time-division multiplexer/demultiplexer for digital transmission in the gigabit per second range
- Author(s): P.M. Cashin and D.A.H. Johnson
- Source: Electronics Letters, Volume 3, Issue 6, p. 282 –283
- DOI: 10.1049/el:19670216
- Type: Article
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–283
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A multiplexer and demultiplexer are proposed that should enable serial transmission of several parallel data channels at speeds up to several gigabits per second. Novel features of the system are the elimination of gates in the high-speed data channel and the use of avalanche-pulse generators to generate the output pulse train.
Noise-threshold improvement in exalted-carrier PSK systems
- Author(s): J. Das and P.D. Sharma
- Source: Electronics Letters, Volume 3, Issue 6, p. 283 –284
- DOI: 10.1049/el:19670217
- Type: Article
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It is shown that the noise threshold of PSK systems may be improved by using certain nonlinear detectors together with exalted carriers in the receiver. In a practical exalted-carrier RWM-PSK system, a threshold improvement of 4–5dB has been obtained by using biased and saturated envelope detectors.
Some asynchronous pulse-modulation systems
- Author(s): J. Das and P.D. Sharma
- Source: Electronics Letters, Volume 3, Issue 6, p. 284 –286
- DOI: 10.1049/el:19670218
- Type: Article
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p.
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Using Step and linear segment approximations of message waveforms, some asynchronous, pulse-modulation systems have been developed. The four important types have been theoretically investigated, and, their characteristics, e.g. dynamic range, quantising noise and channel-bandwidth requirements, have been determined.
Optimised δ-δ modulation system
- Author(s): J. Das and P.K. Chatterjee
- Source: Electronics Letters, Volume 3, Issue 6, p. 286 –287
- DOI: 10.1049/el:19670219
- Type: Article
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Based on the successive approximation of message waveforms, a multidigit δM system, incorporating individual optimised δM stages, has been developed. It is shown that the coding efficiency of this system is better than that of the conventional PCM for the same information rates, and further improvements are obtained by the use of simple instantaneous compandors and suitable phase compensation.
Pulse-interval modulation
- Author(s): J. Das and P.D. Sharma
- Source: Electronics Letters, Volume 3, Issue 6, p. 288 –289
- DOI: 10.1049/el:19670220
- Type: Article
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p.
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Using a decaying step approximation of signal waveforms, a new method of coding messages with 1/0 pulses having varying intervals only has been developed. The quantising noise in the received message has been reduced considerably by making the coder self-oscillating, thus giving rise to an asynchronous system having properties similar to those of the familiar p.p.m. and p.f.m. systems.
Radiation patterns of leaky circular waveguides with eight and twelve transverse slots
- Author(s): C.J.E. Phillips and R. Wielebinski
- Source: Electronics Letters, Volume 3, Issue 6, page: 289 –289
- DOI: 10.1049/el:19670221
- Type: Article
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Uniform distribution of radiated power is a necessary requirement in many aerial applications. Radio beacons and television transmitting aerials are examples of such a requirement. Aerials made from slotted circular waveguides have found application in engineering practice. We have computed the azimuth distribution of radiation from waveguides with eight and twelve, transverse slots. Combined with existing literature, the design of aerials with extremely high azimuth uniformity is possible.
Erratum: Lyapunov estimates of oscillator transients in p.c.m. systems
- Author(s): P.C. Parks and M.R. Miller
- Source: Electronics Letters, Volume 3, Issue 6, page: 291 –291
- DOI: 10.1049/el:19670222
- Type: Article
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Erratum: Simulated inductors using differential amplifiers
- Author(s): R.H.S. Riordan
- Source: Electronics Letters, Volume 3, Issue 6, page: 291 –291
- DOI: 10.1049/el:19670223
- Type: Article
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Erratum: Accurate numerical solution of the one-dimensional p-n junction in steady state
- Author(s): A. Demari
- Source: Electronics Letters, Volume 3, Issue 6, page: 291 –291
- DOI: 10.1049/el:19670224
- Type: Article
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