Online ISSN
1350-911X
Print ISSN
0013-5194
Electronics Letters
Volume 17, Issue 23, 12 November 1981
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Volume 17, Issue 23
12 November 1981
Reduction of FM noise in impatt oscillators by optical illumination
- Author(s): A.J. Seeds and J.R. Forrest
- Source: Electronics Letters, Volume 17, Issue 23, p. 865 –866
- DOI: 10.1049/el:19810603
- Type: Article
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Experiments are described in which laser illumination of the active device has reduced the FM noise output by up to 5 dB for a GaAs impatt oscillator and 2 dB for a Si impatt oscillator. A qualitative explanation of the observed results is given, and the effect of laser amplitude noise on the maximum noise reduction obtainable is shown.
Mismatch losses in multiply tapped SAW convolvers
- Author(s): E.L. Adler
- Source: Electronics Letters, Volume 17, Issue 23, p. 866 –867
- DOI: 10.1049/el:19810604
- Type: Article
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An analysis procedure is given for calculating the output mismatch loss in a multiply tapped SAW convolver. The analysis takes into account the lossy transmission-line properties of convolvers and includes realistic values for the parasitics due to bonding pads and wires. Results illustrating trade-offs between bandwidth and insertion loss for a convolver with six taps are given, which provide guidelines for the design of broadband output matching networks.
Low-loss single-mode fibres prepared by plasma-enhanced MCVD
- Author(s): J.W. Fleming and V.R. Raju
- Source: Electronics Letters, Volume 17, Issue 23, p. 867 –868
- DOI: 10.1049/el:19810605
- Type: Article
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A series of single-mode lightguide preforms capable of yielding > 20 km of 110 μm OD fibre have been fabricated using the RF plasma-enhanced MCVD technique. The loss of kilometre lengths drawn from both ends of the preforms has been measured. At 1.3 μm, the loss ranged between 0.55 and 0.7 dB/km. The preforms were made at deposition rates of 3.5 g/min.
Properties of inverted rib-waveguide lasers operating at 1.3 μm wavelength
- Author(s): S.E.H. Turley ; G.D. Henshall ; P.D. Greene ; V.P. Knight ; D.M. Moule ; S.A. Wheeler
- Source: Electronics Letters, Volume 17, Issue 23, p. 868 –870
- DOI: 10.1049/el:19810606
- Type: Article
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The fabrication and operating characteristics of InGaAsP inverted rib-wavelength lasers emitting at 1.3 μm wavelength are described. Stable zero-order lateral mode CW operation has been achieved up to 20 mW output power and CW lasing up to 90°C has been obtained. Spectral measurements and reliability data are also presented.
Enhanced mobility in inverted AlxGa1−xAs/GaAs heterojunctions: binary on top of ternary
- Author(s): T.J. Drummond ; H. Morkoç ; S.L. Su ; R. Fischer ; A.Y. Cho
- Source: Electronics Letters, Volume 17, Issue 23, p. 870 –871
- DOI: 10.1049/el:19810607
- Type: Article
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–871
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Single-period modulation doped inverted Al0.18Ga0.82As/GaAs heterostructures having the binary on top of the ternary were grown by molecular beam epitaxy. Despite the early reports of no mobility enhancement, considerable mobility enhancement, particularly at cryogenic temperatures, were obtained in the present structures. Mobilities of about 27 600 cm2/Vs with associated sheet carrier concentrations of about 6×1011 cm−2 were obtained at 10 K. The results represent the first enhanced mobilities obtained by molecular beam epitaxy and compare with 25 600 cm2/Vs deduced from Shubnikov de Haas measurements in LPE-grown structures at 4 K.
Very broadband bipolar VCO
- Author(s): R.G. Winch
- Source: Electronics Letters, Volume 17, Issue 23, p. 871 –873
- DOI: 10.1049/el:19810608
- Type: Article
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A VCO tunable over a frequency range of 6.94 to 19.22 GHz in 20 V has been achieved by broadbanding a hyperabrupt varactor tuned bipolar oscillator. This was accomplished by introducing variable phase feedback in the form of a second hyperabrupt junction-varactor diode. The high operating frequency was attained by using a doubling mode circuit.
Selective carrier removal using oxygen implantation in GaAs
- Author(s): M. Berth ; C. Venger ; G.M. Martin
- Source: Electronics Letters, Volume 17, Issue 23, p. 873 –874
- DOI: 10.1049/el:19810609
- Type: Article
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It has been reported that free-carrier compensation can be achieved using oxygen implantation and can remain stable even after annealing at temperatures up to 900°C. It is demonstrated that carrier removal rate is drastically dependent on the initial donor species. It is very likely that carrier removal in Si-doped layers takes place via formation of Si-O complexes.
Mode power distribution in optical fibres with fluctuation in physical parameters and application to backscattering signal analysis
- Author(s): P. Di Vita
- Source: Electronics Letters, Volume 17, Issue 23, p. 874 –876
- DOI: 10.1049/el:19810610
- Type: Article
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The evolution of mode power distribution in fibres with fluctuations of physical parameters is investigated. The analysis is applied to the interpretation of backscattering trace. Rigorous expressions of backscattering power in the presence of fluctuations of fibre core radius and maximum NA are provided in many common cases.
Three-dimensional fibre preform profiling
- Author(s): P.L. Francois ; I. Sasaki ; M.J. Adams
- Source: Electronics Letters, Volume 17, Issue 23, p. 876 –878
- DOI: 10.1049/el:19810611
- Type: Article
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Results are reported of three-dimensional profiling of fibre preforms from deflection function measurements. We demonstrate the importance of performing the integration involved with a sufficient number of points and show how the systematic use of interpolation allows this number of points to be obtained from a few preform projections.
Effect of energy relaxation on injected current pulse in high-frequency IMPATT diodes
- Author(s): D. Lippens and E. Constant
- Source: Electronics Letters, Volume 17, Issue 23, p. 878 –879
- DOI: 10.1049/el:19810612
- Type: Article
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The effect of energy relaxation on carrier injection in millimetre-wave IMPATT diodes is considered. For this purpose, an approximate formula relating the current pulse injected in the transit region, including the energy relaxation, is derived. Its influence on the RF impedance of the impatt oscillator is discussed.
Low voltage high performance E/D MOS logic
- Author(s): D.H. Choi and C.A.T. Salama
- Source: Electronics Letters, Volume 17, Issue 23, p. 879 –880
- DOI: 10.1049/el:19810613
- Type: Article
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The letter describes a high performance MOS technology which produces both enhancement- and depletion-mode devices on the same substrate without using ion implantation. The enhancement mode devices, with 1–2 μm channel lengths, can be realised using regular optical lithography and simple processing techniques.
Arrays of concentric rings as frequency selective surfaces
- Author(s): E.A. Parker ; S.M.A. Hamdy ; R.J. Langley
- Source: Electronics Letters, Volume 17, Issue 23, p. 880 –881
- DOI: 10.1049/el:19810614
- Type: Article
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Concentric rings can be used as array elements in frequency selective surfaces. The transmission curves are more complex than those for simple rings, but provide more closely spaced reflection and transmission bands. In an example discussed here, a band centre frequency ratio of 1/1.3 is given by an array of compound elements with two concentric rings.
Extraction of decision level for envelope-detected amplitude-shift keying
- Author(s): W. Hodgkiss
- Source: Electronics Letters, Volume 17, Issue 23, p. 881 –883
- DOI: 10.1049/el:19810615
- Type: Article
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The optimum decision level for envelope-detected on/off amplitude-shift keying (ASK) in Gaussian noise is a complex function of the signal/noise ratio. A practical method is described which allows the decision threshold to be automatically extracted from the values at the decision instants of the binary levels.
New method for direct G/T measurement using satellite signals
- Author(s): A. Sion
- Source: Electronics Letters, Volume 17, Issue 23, p. 883 –885
- DOI: 10.1049/el:19810616
- Type: Article
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–885
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A new possible method for direct G/T measurement using satellite signals is described. A formula for calculation of G/T from Y-factor and down link EIRP measurement is developed. The potential of the method for low G/T measurement is illustrated with possible applicability to Intelsat Standard B and C and ECS earth stations. Possible disadvantages are commented on.
Mode conversion in profiled E-plane tapers and horns
- Author(s): M.T. Birand ; P. Wright ; N. Williams
- Source: Electronics Letters, Volume 17, Issue 23, p. 885 –886
- DOI: 10.1049/el:19810617
- Type: Article
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An efficient technique for determining the mode conversion in profiled E-plane tapers and radiating horns is presented. The profile is approximated by radial waveguide sections and their junction wave transfer matrices are derived applying field matching together with the method of least squares. Mode conversion levels at any point along the axis of the structure can then be determined simply by cascading these matrices. The results of numerical and experimental investigations which illustrate the validity of the proposed technique are presented.
Novel active RC building block with optimal sensitivity
- Author(s): J.C. Berka and M. Herpy
- Source: Electronics Letters, Volume 17, Issue 23, p. 887 –888
- DOI: 10.1049/el:19810618
- Type: Article
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An easily trimmed universal building block, adaptable for integrated modules and intended for realising biquadratic transfer functions, is presented. The proposed building block has sensitivities referred to passive circuit elements which are equal to the theoretical minimum value, while sensitivities referred to active circuit elements are optimal and much lower than those of known building blocks.
Power spectra of M-ary variable index CPFSK
- Author(s): K.M. Sundara Murthy and K.W. Cattermole
- Source: Electronics Letters, Volume 17, Issue 23, p. 888 –889
- DOI: 10.1049/el:19810619
- Type: Article
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A generalised closed form expression for the power spectral density (PSD) of M-ary variable index continuous phase FSK (VI CPFSK) has been derived using the Transform technique. Examples are presented for typical cases with input levels 2, 4 and 8. Approximation results are presented for comparison.
1.3 μm, 400 Mbit/s undersea optical repeater sea trial
- Author(s): Y. Nomura ; T. Morimitsu ; I. Kitazawa ; M. Washio
- Source: Electronics Letters, Volume 17, Issue 23, p. 889 –891
- DOI: 10.1049/el:19810620
- Type: Article
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A sea trial of a 1.3 μm, 400 Mbit/s undersea optical repeater1,2 connected with a 1.3 km-long undersea optical cable was conducted in Sagami Bay at about a 700 m depth in January 1981. Stable performance for the repeater was confirmed, as it withstood such external mechanical forces as heavy tension, water pressure, vibration, shock and extreme temperature change during laying and recovering.
Flat short-circuited strip of one wavelength width and acting at quarter-wave resonance
- Author(s): G. Dubost
- Source: Electronics Letters, Volume 17, Issue 23, p. 891 –893
- DOI: 10.1049/el:19810621
- Type: Article
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Properties of a large, flat short-circuited half-radiating strip acting at a quarterwave resonance are presented. It is excited by means of several feed points. The obtained bandwidth is large. When the width is about one wavelength, it appears as an antenna with excellent efficiency and high directivity. Correct agreement is obtained between theoretical and experimental results.
Influence of two-path propagation on MSK systems
- Author(s): P. Szulakiewicz
- Source: Electronics Letters, Volume 17, Issue 23, p. 893 –894
- DOI: 10.1049/el:19810622
- Type: Article
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The letter presents some analytical and numerical results relative to the performance of a minimum shift keying (MSK) system in the presence of additive Gaussian noise and of multipath fading represented by a two-ray model. The letter also compares results obtained for the MSK system with results for the 4φ CPSK system reported in Reference 1.
Polarisation behaviour fluctuations of a single-mode fibre
- Author(s): G. Garlichs
- Source: Electronics Letters, Volume 17, Issue 23, p. 894 –896
- DOI: 10.1049/el:19810623
- Type: Article
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The linear retardance and its azimuth angle of a 111 cm single-mode fibre have been measured to fluctuate with time. The amplitude and frequency of these fluctuations depend on temperature. The circular retardance of the fibre has been found to remain constant.
Solution of wave equation in graded-index optical fibres by means of multiparabolic approximation
- Author(s): G. Coppa and P. di Vita
- Source: Electronics Letters, Volume 17, Issue 23, p. 896 –897
- DOI: 10.1049/el:19810624
- Type: Article
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A new numerical method for the solution of the wave equation in fibres with any profile, consisting in approximating the profile with a suitable set of parabolas, is proposed. The method results are very powerful as regards the precision in propagation constants and group delays, and in computing speed, particularly for near optimum profiles.
Ion implanted optical waveguides in LiNbO3
- Author(s): G.D.H. King ; M.C. Bone ; B.L. Weiss ; D.W. Weeks
- Source: Electronics Letters, Volume 17, Issue 23, p. 897 –898
- DOI: 10.1049/el:19810625
- Type: Article
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The fabrication of low loss single mode integrated optical waveguides by the implantation of He+ ions in LiNbO3 is reported. An assessment is made of the processing requirements in terms of implantation energy, ion dose and annealing parameters. Consideration is also given to the use of multienergy implants as a means of improving isolation between waveguide and substrate. Results on single mode planar waveguides show propagation losses below 1 dB cm−1 for laser light of 632.8 nm wavelength.
Laser diode switch
- Author(s): M. Ikeda
- Source: Electronics Letters, Volume 17, Issue 23, p. 899 –900
- DOI: 10.1049/el:19810626
- Type: Article
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Optical switches using laser diodes are proposed. Basic switching operation using an AlGaAs CSP laser is demonstrated for the first time. Isolation is better than 71 dB, signal bandwidth is broader than 1.5 GHz, and switching time is shorter than a few nanoseconds.
Erratum: Efficient three-wavelength-output SAW multistrip beam compressor for convolver applications
- Author(s): S. Ameri and D.J. Gunton
- Source: Electronics Letters, Volume 17, Issue 23, page: 900 –900
- DOI: 10.1049/el:19810627
- Type: Article
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