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Online ISSN 1350-911X Print ISSN 0013-5194

Electronics Letters

Volume 16, Issue 9, 24 April 1980

Volumes & issues:

Volume 16, Issue 9

24 April 1980

Various approximating functions for cascade or ladder simulating RC active networks
  • Author(s): R. Leuenberger
  • Source: Electronics Letters, Volume 16, Issue 9, p. 309 –310
  • DOI:  10.1049/el:19800222
  • Type: Article
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  • p. 309 –310 (2)
    The use of m.r.p.e.r. (multiple real pole equal ripple) and m.c.p.e.r. (multiple critical pole equal ripple) approximating functions for the design of RC active filters is shown. A study of various LC ladder structures using Cauer,3 m.r.p.e.r. or m.c.p.e.r. solutions has been performed. The results indicate that no significant difference can be expected if either of these solutions is used. It is shown that more components are required for m.r.p.e.r. or m.c.p.e.r. solutions, and that no improvement over coupled sections of lower order can be observed.
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Experimental characterisation of graded-index single-mode fibres
Increasing power input to a single solar power satellite rectenna by using a pair of satellites
Shallow trap spectroscopy in InP:Fe
GaAs gigabit logic circuits using normally-off m.e.s.f.e.t.s
  • Author(s): T. Mizutani ; N. Kato ; S. Ishida ; K. Osafune ; M. Ohmori
  • Source: Electronics Letters, Volume 16, Issue 9, p. 315 –316
  • DOI:  10.1049/el:19800226
  • Type: Article
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  • p. 315 –316 (2)
    Normally-off GaAs m.e.s.f.e.t. logic circuits fabricated by electron beam lithography have exhibited excellent high speed switching characteristics. The highest switching speed evaluated from a 15-stage ring oscillator is 30 ps per gate with a power dissipation of 1.9 mW. Binary frequency dividers have been fabricated with D-type flip-flops operating up to 3 GHz. A divide-by-eight counter has also operated at 2.5 GHz.
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Increasing the clock frequency of switched-capacitor filters
  • Author(s): T.R. Viswanathan  and  T.L. Viswanathan
  • Source: Electronics Letters, Volume 16, Issue 9, p. 316 –317
  • DOI:  10.1049/el:19800227
  • Type: Article
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  • p. 316 –317 (2)
    The time constant τ of a switched-capacitor (s.c.) integrator is C/(fcCR), where CR is the value of the s.c., C the integrating capacitor and fc the clock frequency. For a given τ, if fc is to increase, C/CR must increase proportionately. Since a large capacitor ratio C/CR is inconvenient to implement in an integrated circuit, most s.c. filters are clocked at the Nyquist rate. Since higher clock rates reduce switching delays, a technique of enabling higher clock frequencies without the need for large capacitor ratios has been developed.
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Low noise GaAs varactor and mixer diodes prepared by molecular beam epitaxy
  • Author(s): J.J. Harris  and  J.M. Woodcock
  • Source: Electronics Letters, Volume 16, Issue 9, p. 317 –319
  • DOI:  10.1049/el:19800228
  • Type: Article
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  • p. 317 –319 (3)
    Schottky-barrier varactor and mixer diodes have been made from Ge-doped GaAs layers grown by molecular beam epitaxy. A microstrip parametric amplifier circuit incorporating a hyperabrupt varactor diode has given a noise temperature of 120 K and bandwidth of 180 MHz at 15 dB gain when pumped at 34 GHz, and a mixer diode mounted in a cryogenic receiver circuit had an s.s.b. noise temperature of 180 K at 90 GHz.
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Improving the speed of convex hull calculations
  • Author(s): B.K. Marlow  and  B.G. Batchelor
  • Source: Electronics Letters, Volume 16, Issue 9, p. 319 –321
  • DOI:  10.1049/el:19800229
  • Type: Article
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  • p. 319 –321 (3)
    In certain applications of image analysis (e.g. automatic visual inspection) it is possible to obtain silhouettes of isolated objects. In such situations, it is possible to use the algorithm and hardware discussed in this article. A hardware mechanism is described that is able to select points from a binary image corresponding to local changes in the direction of a black/white edge. This allows the subsequent, software-based, computational work to be reduced by a substantial amount; in the examples cited, the average savings exceeded 80%. The technique can tolerate holes in the silhouette.
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Microlens tipped on a single-mode fibre end for InGaAsP laser coupling improvement
  • Author(s): Yasuji Murakami ; Jun-ichi Yamada ; Jun-ichi Sakai ; Tatsuya Kimura
  • Source: Electronics Letters, Volume 16, Issue 9, p. 321 –322
  • DOI:  10.1049/el:19800230
  • Type: Article
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  • p. 321 –322 (2)
    A new fabrication method for a hemispherical microlens on optical fibre ends is proposed, to achieve high coupling efficiency between an InGaAsP laser with a buried heterostructure geometry and a single-mode fibre. The microlens is fabricated by attaching silica glass to the fibre end, which is then heated to form the desired shape by electric discharge. The lowest coupling loss of 2.9 dB has been achieved by selecting the optimum lens radius at 8.5 μm. Effects of misalignment are also reported.
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High index microlenses for GaAlAs laser-fibre coupling
  • Author(s): L. d'Auria ; Y. Combemale ; C. Moronvalle ; A. Jacques
  • Source: Electronics Letters, Volume 16, Issue 9, p. 322 –324
  • DOI:  10.1049/el:19800231
  • Type: Article
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  • p. 322 –324 (3)
    The best compromise between coupling efficiency, accuracy of positioning and reproducibility has been obtained for a high index hemispherical lens melted on the tip of an intermediate fibre between the GaAlAs laser and the transmission fibre. The letter describes the lens fabrication technique and gives various experimental results of coupling efficiencies and mechanical tolerances.
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Corrugated waveguide monopulse feed
  • Author(s): R.D. Elliott  and  P.J.B. Clarricoats
  • Source: Electronics Letters, Volume 16, Issue 9, p. 324 –325
  • DOI:  10.1049/el:19800232
  • Type: Article
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  • p. 324 –325 (2)
    The excitation coefficients of modes in a circular corrugated waveguide that arise when dominant modes are incident from a cluster of four square waveguides are calculated. Mono-pulse-like radiation patterns arise when modes in the input guides are appropriately phased. Factors influencing the crosspolar performance of the feed are discussed, and the dependence of the excitation coefficients on waveguide and junction parameters is predicted.
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Predicting the surge capability of power thyristors
Proton-bombardment isolated GaAlAs/GaAs charge-coupled devices
  • Author(s): Y.Z. Liu ; R.J. Anderson ; I. Deyhimy ; L.R. Tomasetta
  • Source: Electronics Letters, Volume 16, Issue 9, p. 327 –329
  • DOI:  10.1049/el:19800234
  • Type: Article
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  • p. 327 –329 (3)
    Proton bombardment is used for the first time as a channel isolation technique to fabricate buried channel homojunction charge-coupled devices (c.c.d.s) of n-GaAs channel on GaAs substrate and heterojunction c.c.d.s of n-Ga1−xAlxAs on GaAs. The c.c.d. structure is a Schottky-barrier gate buried channel 3-phase device with 30 transfer gates. The channel-stop bombardment was carried out at room temperature with an energy of 200 keV and a total dose of 1015/cm2. The c.c.d.s were tested with electrical charge injection and direct readout. The charge transfer efficiency was found to be greater than 0.999 per transfer for both GaAs and GaAlAs. The proton-bombardment isolated devices were compared with similar devices using mesa isolation and were found to perform similarly.
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Backscattering in single-mode fibres
Sampled-data recursive integrator for ultra-low-frequency wideband phase shifter
Efficient generation of near-i.r. stimulated light scattering in optical fibres pumped in low-dispersion region at 1.3 μm
Comment: Synthesis of active RC multiport voltage transfer functions with reduced number of operational amplifiers
Reply: Synthesis of active RC multiport voltage transfer functions with reduced number of operational amplifiers
Transient thermal analysis of integral-heat-sink GaAs pulsed Gunn device
  • Author(s): D.C. Smith  and  R.L. Tebbenham
  • Source: Electronics Letters, Volume 16, Issue 9, p. 334 –335
  • DOI:  10.1049/el:19800240
  • Type: Article
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  • p. 334 –335 (2)
    A technique is outlined for the estimation of the transient thermal impedance of the commonly used microwave device structure employing an integral heat sink (i.h.s.). The structure is analysed in three separate regions, approximations being made to the analytical solution of the classical heat flow equation applied to each. Theoretical predictions are compared with experimental observations on a typical i.h.s. Gunn device, and the implications on device design considered.
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Sufficient conditions for global homeomorphism of piecewise linear functions
Improvements to binary floating-point digital differential analysers
  • Author(s): G. Hannington
  • Source: Electronics Letters, Volume 16, Issue 9, p. 337 –338
  • DOI:  10.1049/el:19800242
  • Type: Article
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  • p. 337 –338 (2)
    A description is given of a novel method of providing a residue in a binary floating-point digital differential analyser. The error bounds for a sine/cosine generator utilising floating-point integrators employing Euler integration both with and without a residue are given and compared. Also described is a method for avoiding the extra delay incurred in using an Euler integrator module as a coefficient multiplier.
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Comment: Mixed time/frequency domain approach to model reduction
Reply: Mixed time/frequency domain approach to model reduction
Miniature microstrip bandpass filter with large stopbands
GaInAsP/InP laser with monolithically integrated monitoring detector
Parametric interactions when resonator reactances are varied in antiphase
  • Author(s): B.Z. Kaplan
  • Source: Electronics Letters, Volume 16, Issue 9, p. 343 –345
  • DOI:  10.1049/el:19800247
  • Type: Article
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  • p. 343 –345 (3)
    The letter considers a situation where both reactances of a resonator are pumped in exact antiphase. While a previous mode of pumping, where the reactances are pumped in unison, has been shown incapable of yielding parametric excitations, the present mode exhibits several possible interactions. Some of the interactions are similar to those in common parametric systems; other interactions seem unfamiliar and related to an aperiodic mode of pumping. The results, and especially those concerning the latter interaction, appear relevant to practical microwave, acoustic and optical systems, and may lead to new applications.
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Stable reduced-order Padé approximants using stability-equation method

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