Online ISSN
1350-911X
Print ISSN
0013-5194
Electronics Letters
Volume 12, Issue 11, 27 May 1976
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Volume 12, Issue 11
27 May 1976
R.F. induction furnace for silica-fibre drawing
- Author(s): P.F. Checcacci ; A.M. Sheggi ; M. Brenci
- Source: Electronics Letters, Volume 12, Issue 11, p. 265 –266
- DOI: 10.1049/el:19760204
- Type: Article
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An r.f. induction furnace is described to be used in a standard-type machine for drawing silica fibres for optical communication. The furnace consists of a small induction-heated graphite element which is fitted in a ‘concentrator’ (stepdown transformer) placed directly in the tank coil of the r.f. generator, thus allowing one to maximise the matching efficiency between the generator and the heating element. The small dimensions of the graphite element make the furnace quickly responsive to input-power variations, so that it can be brought to a maximum temperature of 2180 K in 10 s. An argon atmosphere and an additional argon laminar flow are provided to avoid fibre contamination by the sublimated graphite, as well as to preserve the graphite susceptor. Successful tests of furnace operation have been carried out.
New method for wideband excitation of interdigital surface-wave transducers
- Author(s): B.T. Khuri-Yakub and R.L. Joly
- Source: Electronics Letters, Volume 12, Issue 11, p. 266 –267
- DOI: 10.1049/el:19760205
- Type: Article
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A new method of designing coupled resonator networks for wideband excitation of interdigital surface-wave transducers is described. The elements of the tuning network are chosen, using an optimisation computer program. The insertion loss is minimised over the bandwidth of interest. For interdigital transducers on a monolithic zinc-oxide-on-silicon structure with Δv/v = 0.0036, a fractional bandwidth of 20% can be obtained. For a narrow-acoustic-beam interdigital transducer on a LiNbO3 halfspace with Δv/v = 0.022, a fractional bandwidth of 40% can be obtained. The design of the coupled resonator network takes into consideration the variation of the transducer acoustic impedance with frequency.
Experimental acoustic-surface-wave-to-bulk-wave scattering by grooves
- Author(s): A. Ronnekleiv ; H.J. Shaw ; J. Souquet
- Source: Electronics Letters, Volume 12, Issue 11, p. 267 –269
- DOI: 10.1049/el:19760206
- Type: Article
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p.
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The letter describes results obtained on the conversion of acoustic surface waves into bulk waves through scattering by rectangular grooves on aluminium at 1.15 MHz, and gives a comparison with theoretical predictions.
Predicted frequency dependence of microstrip characteristic impedance using the planar-waveguide model
- Author(s): R.P. Owens
- Source: Electronics Letters, Volume 12, Issue 11, p. 269 –270
- DOI: 10.1049/el:19760207
- Type: Article
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p.
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Modifications to the equation defining the width of the planar-waveguide model for microstrip are proposed, and which predict a frequency-dependent characteristic impedance in better agreement with the results of dynamic theories of microstrip.
Optoelectronic gating of microwave signals using a silicon microstrip shunt modulator
- Author(s): W. Platte and G. Appelhans
- Source: Electronics Letters, Volume 12, Issue 11, p. 270 –271
- DOI: 10.1049/el:19760208
- Type: Article
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A new silicon microstrip modulator for optoelectronic gating of microwave signals is described. Gating infrared pulses produces a small semiconductor region of high photoconductivity, which shunts the microstrip transmission line if special strip conductor structures are used. Theoretical and experimental results were found to agree fairly well.
Monolithic waveguide zinc-oxide-on-silicon convolver
- Author(s): B.T. Khuri-Yakub and G.S. Kino
- Source: Electronics Letters, Volume 12, Issue 11, p. 271 –272
- DOI: 10.1049/el:19760209
- Type: Article
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A monolithic waveguide zinc-oxide-on-silicon convolver has been constructed and operated at a centre frequency of 125 MHz. The zinc oxide is originally deposited over the whole substrate and then etched to form the waveguide. The waveguide width is 1/10 of the beam width at the input transducers, which should yield a 20 dB improvement in efficiency over a normal convolver with a beam width equal to the transducer width, after accounting for the loss in the input tapers. Such an improvement was observed in experimental devices.
O-band fast p-i-n-diode switch
- Author(s): A.J. Paffard
- Source: Electronics Letters, Volume 12, Issue 11, page: 272 –272
- DOI: 10.1049/el:19760210
- Type: Article
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An O-band fast p-i-n-diode s.p.s.t. switch has been developed which has an insertion loss of ≤ 1.0 dB and an isolation of ≥ 25 dB over a 5% bandwidth. Switching speed is < 1 ns and estimated power handling is ≥ 1 W c.w. The unit is to be used as a modulator in a 60 GHz, 130 Mbit/s digital radio data link under development at RSRE, Malvern, England.
Computation of Thévenin and Norton equivalents
- Author(s): I.N. Hajj
- Source: Electronics Letters, Volume 12, Issue 11, p. 273 –274
- DOI: 10.1049/el:19760211
- Type: Article
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A simple method is given for obtaining Thévenin and Norton equivalents of linear networks and systems.
Recombination effects with high-pressure Langmuir probes
- Author(s): R.M. Clements ; B.M. Oliver ; A.I. Noor ; P.R. Smy
- Source: Electronics Letters, Volume 12, Issue 11, p. 274 –275
- DOI: 10.1049/el:19760212
- Type: Article
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With increasing ion density, the ion current collected by a negatively biased electric probe is eventually dominated by ions produced by reactive processes in the vicinity of the probe. Here, we derive an expression for the probe current to a cylindrical probe when all the ions collected to the probe are assumed to be generated within the sheath which surrounds the probe. Measurements of probe current in a seeded atmospheric-pressure flame are in good agreement with the theory. The significance of reaction processes is reinforced by the fact that the maximum probe current is found to be approximately three times the total current that the flame would produce with frozen chemistry, i.e. the saturation current.
Collector-base capacitance of high frequency integrated bipolar transistors
- Author(s): A.H. Kwesah and M.K. McPhun
- Source: Electronics Letters, Volume 12, Issue 11, p. 275 –276
- DOI: 10.1049/el:19760213
- Type: Article
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A method of obtaining the correct emitter junction capacitance Cb'e from the measured device parameters is presented. This method is shown to apply to integrated bipolar transistors having fT ≃ 2.5 GHz.
Linear block codes for nonindependent errors
- Author(s): A.A. Hashim
- Source: Electronics Letters, Volume 12, Issue 11, p. 276 –277
- DOI: 10.1049/el:19760214
- Type: Article
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p.
276
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A computerised search procedure based on certain properties of the parity-check matrix of those block codes capable of correcting nonindependent errors is described which yields a considerable number of linear block codes that are capable of correcting random or burst errors.
Unitary (energy-preserving) multichannel networks with feedback
- Author(s): M.A. Gerzon
- Source: Electronics Letters, Volume 12, Issue 11, p. 278 –279
- DOI: 10.1049/el:19760215
- Type: Article
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p.
278
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A unitary n-input n-output linear network preserves the total energy of all input signals. Using the functional calculus of normal matrices, it is proved that feedback round a unitary circuit plus a direct path with suitable gain yields another unitary circuit. This has applications to the design of electronic reverberation units.
Threshold logic functions in programmable logic arrays
- Author(s): L.A.M. Bennett
- Source: Electronics Letters, Volume 12, Issue 11, p. 279 –280
- DOI: 10.1049/el:19760216
- Type: Article
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p.
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Methods of implementing threshold-logic functions in programmable logic arrays are described. Use is made of the properties of the threshold functions to achieve a more efficient implementation, in terms of silicon area required, than a previously described cellular array.
Frequency response of a multiplexed charge-transfer delay line
- Author(s): S.C. Dutta Roy
- Source: Electronics Letters, Volume 12, Issue 11, p. 280 –281
- DOI: 10.1049/el:19760217
- Type: Article
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p.
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The magnitude and delay responses of a multiplexed charge-transfer delay line are shown to be equal ripple. While the magnitude ripple decreases with increase in the number of parallel channels, the delay ripple is independent of this number and is determined only by the charge-transfer inefficiency.
Correction factors for the determination of optical-fibre refractive-index profiles by the near-field scanning technique
- Author(s): M.J. Adams ; D.N. Payne ; F.M.E. Sladen
- Source: Electronics Letters, Volume 12, Issue 11, p. 281 –283
- DOI: 10.1049/el:19760218
- Type: Article
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Numerical calculations are presented of the correction factor for use with the near-field scanning method of index profile determination. It is shown that a single curve can be applied to a range of possible profiles, and a numerically obtained average curve is given.
Interconnecting solved subsystems
- Author(s): R. Marrett and P.H. Roe
- Source: Electronics Letters, Volume 12, Issue 11, p. 283 –284
- DOI: 10.1049/el:19760219
- Type: Article
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A tableau approach to the interconnection of solved sub-systems is presented which preserves their separate identity, but which allows full use of available sparse-matrix techniques.
Criterion for the optimum punchthrough factor of gallium-arsenide IMPATT diodes
- Author(s): P.A. Blakey ; B. Culshaw ; R.A. Giblin
- Source: Electronics Letters, Volume 12, Issue 11, p. 284 –286
- DOI: 10.1049/el:19760220
- Type: Article
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284
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Simple theory predicts an optimum punchthrough factor of approximately 0.7 for gallium-arsenide IMPATTs. Computer-simulation results demonstrate good general agreement with the predictions of the theory.
Self and mutual admittances/impedances of two parallel nonstaggered dipoles driven by 2-wire lines
- Author(s): J.V. Surutka and D.M. Veličković
- Source: Electronics Letters, Volume 12, Issue 11, p. 286 –287
- DOI: 10.1049/el:19760221
- Type: Article
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p.
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–287
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A new theoretical approach to the problem of two identical, parallel, nonstaggered dipole antennas, driven by 2-wire lines is presented. This contribution is an extension of earlier work dealing with the isolated dipole antenna driven by a 2-wire line. The present simple theory is limited to coupled dipoles, the distances of which are greater than one-tenth of a wavelength.
Reflection from a cylinder in a surface-wave field
- Author(s): A.L. Cullen ; A.M.J. Davis ; F.G. Leppington
- Source: Electronics Letters, Volume 12, Issue 11, p. 287 –288
- DOI: 10.1049/el:19760222
- Type: Article
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287
–288
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Refinements are made to the results of an earlier calculation, published recently, by including the effects of the magnetic source contribution arising from the magnetic polarisability along the axis of the cylinder.
Design of 2-dimensional recursive digital filters
- Author(s): F. Bernabo' ; P.L. Emiliani ; V. Cappellini
- Source: Electronics Letters, Volume 12, Issue 11, p. 288 –289
- DOI: 10.1049/el:19760223
- Type: Article
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288
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A method is proposed for designing 2-dimensional recursive digital filters with circular symmetry and zero phase. The method is based on transformations of the squared magnitude function of a 1-dimensional digital filter and on the stabilisation of the resulting digital filter. Design results are given.
High-frequency radiation intensity noise spectrum of c.w.d.h. GaAlAs-diode lasers
- Author(s): H. Jäckel
- Source: Electronics Letters, Volume 12, Issue 11, p. 289 –291
- DOI: 10.1049/el:19760224
- Type: Article
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p.
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Measurements of the intrinsic intensity noise spectrum of the radiation from c.w.d.h. GaAlAs-diode lasers at different pump currents are reported. The intensity noise spectrum was measured in the frequency range from 30 MHz to 8 GHz. Operating temperatures of the lasers were 10°C and −20°C. Stabilisation of the intensity fluctuations at currents above threshold seems to be effective at frequencies up to 8 GHz. The results are compared with computer solutions for a simple, analytical laser-noise model. A good qualitative agreement between measurements and theoretical predictions is found.
Symmetric reflectors with zero depolarisation
- Author(s): H.C. Minnett and B.Maca. Thomas
- Source: Electronics Letters, Volume 12, Issue 11, p. 291 –293
- DOI: 10.1049/el:19760225
- Type: Article
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p.
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The polarisation performance of a symmetric reflector antenna illuminated by an ideal feed is limited by depolarisation introduced by the reflector, even if other sources of cross-polarisation are negligible. It is shown that depolarisation can theoretically be eliminated by the use of anisotropic reflectors.
High-accuracy vector-difference and vector-sum circuits
- Author(s): Barrie Gilbert
- Source: Electronics Letters, Volume 12, Issue 11, p. 293 –294
- DOI: 10.1049/el:19760226
- Type: Article
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p.
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By combining the exact nonlinear capabilities of translinear circuits with the high-gain, low-input-offset, load-driving and level-shifting properties of op-amps, analogue computing structures of great power and precision can be realised. This point is illustrated by circuits which compute the root sum of squares and root difference of squares.
Digital filters using read-only memories
- Author(s): H. Nussbaumer
- Source: Electronics Letters, Volume 12, Issue 11, p. 294 –295
- DOI: 10.1049/el:19760227
- Type: Article
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p.
294
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An algorithm, based on the replacement of multiply operations by table lookup, is presented for the computation of low-order digital convolutions.
Erratum: Multipole optical-fibre connector
- Author(s): J. Guttmann ; O. Krumpholz ; E. Pfeiffer
- Source: Electronics Letters, Volume 12, Issue 11, p. 295 –296
- DOI: 10.1049/el:19760228
- Type: Article
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