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Online ISSN 1350-911X Print ISSN 0013-5194

Electronics Letters

Volume 15, Issue 20, 27 September 1979

Volumes & issues:

Volume 15, Issue 20

27 September 1979

Digraph analysis of large-scale systems: the system primitive
Evaluation of the transient response of linear stationary systems to a class of excitations
Birefringence in elliptically deformed optical fibres
Very low OH content P2O5-doped silica fibres
  • Author(s): Yasuji Ohmori ; Hisaaki Okazaki ; Iwao Hatakeyama ; Hisao Takata
  • Source: Electronics Letters, Volume 15, Issue 20, p. 616 –618
  • DOI:  10.1049/el:19790440
  • Type: Article
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  • p. 616 –618 (3)
    Very low OH content optical fibres consisting of P2O5-doped silica core and GeO2-P2O5-B2O3-doped silica cladding were fabricated by the m.c.v.d. technique. The relation between the OH absorption loss and the deposition temperature was clarified. The OH content in this fibre could be reduced to about seven parts per billion (∼ 7 × 10−9) by using a low deposition temperature.
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Transfer functions with equiripple passband and very low Q-factor for economical active filters
Effects of ion implantation on deep levels in GaAs
  • Author(s): T.R. Jervis ; D.W. Woodard ; L.F. Eastman
  • Source: Electronics Letters, Volume 15, Issue 20, p. 619 –621
  • DOI:  10.1049/el:19790442
  • Type: Article
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  • p. 619 –621 (3)
    We have studied the effects of ion implantation in GaAs using the techniques of deep-level transient spectroscopy. Samples included an unimplanted epitaxial buffer layer, a sample implanted directly into that buffer layer and then capped with Si3N4, a sample implanted into that buffer layer through a similar cap, and a sample implanted directly into a semi-insulating substrate and then capped. All implants were with Si29 and both types of implant were annealed at 860°C for fifteen minutes. We find that the total density of deep levels is not changed significantly by direct implantation, capping and annealing but that implantation through a cap greatly in creases the total deep-level concentration. Deep levels found in implanted layers after capping and annealing are primarily characteristic of the substrate or buffer layer into which the implantation is made, unless the implant is through a cap in which case contaminants from the capping process may be evident at high densities.
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Low-threshold (Ga,In)(As,P) d.h. lasers emitting at 1.55 μm grown by l.p.e.
  • Author(s): G.D. Henshall  and  P.D. Greene
  • Source: Electronics Letters, Volume 15, Issue 20, p. 621 –622
  • DOI:  10.1049/el:19790443
  • Type: Article
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  • p. 621 –622 (2)
    Threshold current densities as low as 2.13 kA cm−2 have been achieved in broad-contact double-heterostructure lasers with an emission wavelength of 1.55 μm. The three-layer structure was grown by liquid-phase epitaxy and contained a quaternary active layer 0.6 μm thick and a p-type quaternary upper confining layer with a bandgap of 1.05 eV. The normalised threshold current density was 3.5 kA cm−2 μm−1.
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Electrochemical carrier concentration profiling in silicon
Double-sided least-squares problem
Structure simplification of optical isolator coupled with laser diode
Novel microwave GaAs field-effect transistors
Preparation and properties of GaAs layers for novel f.e.t. structures
  • Author(s): R.J.M. Griffiths ; I.D. Blenkinsop ; D.R. Wight
  • Source: Electronics Letters, Volume 15, Issue 20, p. 629 –630
  • DOI:  10.1049/el:19790448
  • Type: Article
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  • p. 629 –630 (2)
    N-type GaAs/Ga0.4Al0.6As heterostructures have been grown on semi-insulating GaAs substrates using metal-organic chemical vapour deposition. The GaAs layers were mounted on insulator supports and the substrates and Ga0.4Al0.6As removed using a preferential etching procedure. The preparation and electrical properties of submicrometre thick insulator-supported n-type GaAs layers are described.
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Coefficient correction in programmable c.c.d. recursive filters
Influence of waveguide effects on pulse-delay measurements of material dispersion in optical fibres
M.O.S. switched-capacitor amplifiers
  • Author(s): T.R. Viswanathan ; S.M. Faruque ; K. Singhal ; J. Vlach
  • Source: Electronics Letters, Volume 15, Issue 20, p. 634 –635
  • DOI:  10.1049/el:19790451
  • Type: Article
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  • p. 634 –635 (2)
    Switched-capacitor voltage gain elements, in which the gain is precisely controlled by the ratio of two capacitors, are presented. The voltage gain is obtained by means of a transconductance element operating into a switched-capacitor resistor. Circuit configurations use a single operational amplifier or a unity-gain buffer. In some of these configurations, the offset voltage of the operational amplifier or the buffer is not amplified.
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Nondestructive determination of refractive-index profile and cross-sectional geometry of optical-fibre preform
  • Author(s): P.L. Chu  and  C. Saekeang
  • Source: Electronics Letters, Volume 15, Issue 20, p. 635 –637
  • DOI:  10.1049/el:19790452
  • Type: Article
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  • p. 635 –637 (3)
    A nondestructive method is presented to determine simultaneously the refractive-index profile and the cross-sectional geometry of a preform. In this method, a plane wave is made to impinge on the preform laterally and the power distribution of the scattered pattern is recorded. From the recorded power, the ray pathlength difference is calculated. After the preform has been rotated through 360° and the necessary data collected, a numerical inversion is performed to obtain the index profile and cross-sectional geometry.
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Surface impedance of elliptical hollow conducting waveguides
  • Author(s): S.R. Rengarajan  and  J.E. Lewis
  • Source: Electronics Letters, Volume 15, Issue 20, p. 637 –639
  • DOI:  10.1049/el:19790453
  • Type: Article
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  • p. 637 –639 (3)
    Currently the literature describes two approaches to the determination of power loss in the hollow metallic elliptical waveguide. The well known perturbation method employing the intrinsic impedance of the metal has frequently been used, and an η-dependent surface impedance in two different forms has recently been proposed by several workers. In this work it is suggested that sufficient evidence exists to indicate that the η-dependent formulation is unnecessary.
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Omnidirectional s.h.f. antenna consisting of horn radiators and plane reflectors
Modulo-N counter technique for the u.h.f. band
Appraisal of the inverted-mesa AT-cut quartz resonator for achieving low-inductance high-Q single-response crystal units
  • Author(s): J. Birch  and  S.P. Marriott
  • Source: Electronics Letters, Volume 15, Issue 20, p. 641 –643
  • DOI:  10.1049/el:19790456
  • Type: Article
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  • p. 641 –643 (3)
    A novel design for v.h.f. AT-cut quartz-crystal units is described which enables optimum energy-trapping conditions to be achieved with less restriction in the choice of equivalent electrical parameters than is usual for conventional units. The good suppression of unwanted modes, low inductance values and potentially good frequency stability of this type of unit should lead to its application in both oscillators and filters.
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Variation of lange-coupler geometry with dielectric constant
Switched-capacitor filters using floating-inductance simulation circuits
Enhancement- and depletion-mode vertical-channel m.o.s. gated thyristors
Automatic electrochemical profiling of carrier concentration in indium phosphide
Automatic electrochemical profiling of Hall mobility in semiconductors
Comment: Alternative approach to the design of switched-capacitor filters
GaAs f.e.t. transimpedance front-end design for a wideband optical receiver
  • Author(s): K. Ogawa  and  E.L. Chinnock
  • Source: Electronics Letters, Volume 15, Issue 20, p. 650 –652
  • DOI:  10.1049/el:19790463
  • Type: Article
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  • p. 650 –652 (3)
    A GaAs f.e.t. transimpedance front-end amplifier was built and operated as part of a regenerator at 274 Mb/s. The noise characteristics were optimised for operation with a Ge photodiode at 1.32 μm, but were measured at 0.82 μm to compare Si and Ge photodiodes. The amplifier input capacitance was 3.2 pF with the Si p-i-n diode and 4.6 pF with the Ge diode. At 0.82 μm, we measured a sensitivity for 10−9 error rate of about −35 dBm with the Si diode and −32 dBm with the Ge diode. We predict a sensitivity of −34 dBm at 1.32 μm.
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Elliptical corrugated horn for broadcasting-satellite antennas
Seasonal variations of attenuation statistics in millimetre-wave Earth-satellite link due to bright-band height
InGaAsP p-i-n photodiodes with low dark current and small capacitance
Arbitrary polarisation microwave receiver applied to OTS reception
Exact surface impedance for a cylindrical conductor
Design of optimal controller for linear single-input system
Baseband compatible s.a.w. processors
  • Author(s): G.F. Manes  and  C. Atzeni
  • Source: Electronics Letters, Volume 15, Issue 20, p. 661 –663
  • DOI:  10.1049/el:19790470
  • Type: Article
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  • p. 661 –663 (3)
    A nonlinear acoustic tapped delay line is shown to be capable of providing signal processing at baseband data format via a classical amplitude-modulation/demodulation process; compatibility with baseband-operating analogue/digital arithmetic units is simply and directly achieved, thus resulting in a potentially attractive alternative to existing techniques for programmable transversal filtering implementation.
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Recombination in gallium phosphide via a deep state associated with nickel
  • Author(s): A.R. Peaker ; R.F. Brunwin ; P. Jordon ; B. Hamilton
  • Source: Electronics Letters, Volume 15, Issue 20, p. 663 –664
  • DOI:  10.1049/el:19790471
  • Type: Article
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  • p. 663 –664 (2)
    The properties of nickel in gallium phosphide are discussed in terms of its behaviour as a recombination centre. Although it possesses a large minority-carrier cross-section and is present in v.p.e. material in quite large concentrations, it is found to have a very low majority-carrier cross-section so that the recombination rate saturates at low excitation densities. Thus the centre is unlikely to be of importance in the recombination process in normal l.e.d. structures.
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Generalised correlation model for designing 2-dimensional image coders
Preliminary c.w. reliability measurements on GaAs-(GaAl)As stripe lasers grown by metal-organic c.v.d.
New equal-valued earthed-capacitor notch network using d.v.c.c.s./d.v.c.v.s.

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