Online ISSN
1350-911X
Print ISSN
0013-5194
Electronics Letters
Volume 20, Issue 18, 30 August 1984
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Volume 20, Issue 18
30 August 1984
Novel 2–4 PSK differential demodulator for satellite broadcast receivers using SAW technology
- Author(s): J.P. Willson ; J.T. Zubrzycki ; P. Shelswell
- Source: Electronics Letters, Volume 20, Issue 18, p. 713 –714
- DOI: 10.1049/el:19840488
- Type: Article
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A novel 2–4 PSK differential demodulator based on a three-port SAW delay line is described. A method for optimising the performance by tuning the carrier frequency using the DC output of the demodulator is outlined. The optimum performance of the demodulator was within 0.4 dB of theory for a bit error ratio of 10−3.
Optical time-domain reflectometer with a semiconductor laser amplifier
- Author(s): K. Suzuki ; T. Horiguchi ; S. Seikai
- Source: Electronics Letters, Volume 20, Issue 18, p. 714 –716
- DOI: 10.1049/el:19840489
- Type: Article
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–716
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An optical time-domain reflectometer (OTDR) using a semiconductor laser as an optical pulse generator and as a back-scattered optical signal amplifier is reported. It is found that the detectable one-way loss of the apparatus is improved by 4.5 dB compared with the conventional OTDR using direct detection.
Diffused planar InP bipolar transistor with a cadmium oxide film emitter
- Author(s): L.M. Su ; N. Grote ; F. Schmitt
- Source: Electronics Letters, Volume 20, Issue 18, p. 716 –717
- DOI: 10.1049/el:19840490
- Type: Article
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A novel bipolar InP transistor is demonstrated which comprises a Zn-diffused base and a transparent conductor widegap emitter made of sputtered cadmium oxide. Preliminary current gain was about 10. Owing to its less demanding planar technology the device is assessed to be promising for monolithic integration.
1.8 Gbit/s 65 km optical transmission experiment using a 1.478 μm DFB laser and Ge APD receiver
- Author(s): S.D. Walker ; L.C. Blank ; L. Bickers
- Source: Electronics Letters, Volume 20, Issue 18, p. 717 –719
- DOI: 10.1049/el:19840491
- Type: Article
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A 1.8 Gbit/s optical transmission system trial has been conducted over 65 km of conventional monomode fibre using a 1.478 μm DFB laser and p+n Ge APD receiver. Using a 215 −1, NRZ, PRB test sequence, a long-term BER of 2×10−10 was achieved. Dispersive effects introduced a 1 dB penalty after 65 km transmission.
Noise enhancement in laser amplifiers caused by gain nonuniformity
- Author(s): F. Coste ; J. Fesquet ; J. Arnaud
- Source: Electronics Letters, Volume 20, Issue 18, p. 719 –720
- DOI: 10.1049/el:19840492
- Type: Article
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We have calculated the noise-enhancement factor of a semiconductor laser amplifier with a very thin active region. This (somewhat academic) model exhibits large Petermann's K-factors. However, the calculated noise-enhancement factor K′ is only about half the K-value. The reason for the discrepancy is that in evaluating K′ the radiation modes of the guiding structure have been taken into account. Similar conclusions have been reached for realistic laser models. These theoretical considerations show that gain-guided laser amplifiers are not as noisy as was originally thought.
Surface-acoustic-wave propagation on a piezoelectric substrate with a periodic metal grating
- Author(s): J.B. Davies
- Source: Electronics Letters, Volume 20, Issue 18, p. 720 –722
- DOI: 10.1049/el:19840493
- Type: Article
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An analysis is presented for modes propagating via a periodic metal grating on the surface of a piezoelectric substrate. Assuming no loss in the structure, the numerical solution is exact in the limit, combining the effective permittivity function formulation with the least-squares residual applied at the surface.
1.3 μm bidirectional optical transmission over 31 km of installed single-mode fibre using optical couplers
- Author(s): A.P. McDonna ; D.J. McCartney ; D.B. Mortimore
- Source: Electronics Letters, Volume 20, Issue 18, p. 722 –723
- DOI: 10.1049/el:19840494
- Type: Article
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Results are reported of 1.3 μm bidirectional optical transmission over 31 km of installed cabled fibre at transmission rates of 34–650 Mbit/s using fused biconical tapered couplers manufactured at BTRL. With the introduction of 6 dB extra path loss it is possible to double the system capacity incurring only a small additional penalty at 34 and 140 Mbit/s and no other penalty at 320 and 650 Mbit/s.
Compact dual-polarised coaxial feed at 327 MHz
- Author(s): A. van Ardenne ; J.D. Bregman ; L.H. Sondaar ; M.H.M. Knoben
- Source: Electronics Letters, Volume 20, Issue 18, p. 723 –724
- DOI: 10.1049/el:19840495
- Type: Article
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A highly compact coaxial feed with good pattern symmetry and a crosspolar level maximum of –22 dB has been realised. Pattern symmetry is obtained by a circular plate of suitable diameter surrounding the coaxial feed aperture. The feed is successfully used in the prime focus (f/D=0.35) of an array of 25 m radio telescopes at 327 MHz.
Quadrature hybrid made from transmission line of a single characteristic impedance
- Author(s): J.E.B. Ponsonby
- Source: Electronics Letters, Volume 20, Issue 18, p. 725 –726
- DOI: 10.1049/el:19840496
- Type: Article
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A quadrature hybrid is presented which is entirely composed of lengths of transmission line of characteristic impedance equal to that of the system in which it is used. It is useable over a 10% bandwidth centred on its nominal frequency. Its theoretical frequency responses over this band are presented.
p-adic transforms
- Author(s): V. Laohakosol and W. Surakampontorn
- Source: Electronics Letters, Volume 20, Issue 18, p. 726 –727
- DOI: 10.1049/el:19840497
- Type: Article
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Two clarifications are made on the uniqueness of representation of rational numbers in a finite segmented p-adic field, and on orthogonality asserted in a recent article on p-adic transforms. One clarification also reveals a slight generalisation on dynamic range. In addition, an extension of this transform to finite-dimensional cases is also given.
1.3 μm InGaAsP DCPBH multiquantum-well lasers
- Author(s): N.K. Dutta ; S.G. Napholtz ; R. Yen ; R.L. Brown ; T.M. Shen ; N.A. Olsson ; D.C. Craft
- Source: Electronics Letters, Volume 20, Issue 18, p. 727 –728
- DOI: 10.1049/el:19840498
- Type: Article
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We report the fabrication and performance characteristics of InGaAsP double-channel planar buried heterostructure (DCPBH) lasers with multiquantum-well active layers emitting at 1.3 μm. These lasers have threshold currents in the range 40–50 mA at 30°C, external differential quantum efficiencies of ̃50% at 30°C and T0 values ̃160 to 180 K in the temperature range 10–60°C.
High-power buried coarctate mesa-structure AlGaAs lasers
- Author(s): K. Endo ; H. Kawano ; M. Ueno ; M. Nido ; Y. Kuwamura ; T. Furuse ; I. Sakuma
- Source: Electronics Letters, Volume 20, Issue 18, p. 728 –730
- DOI: 10.1049/el:19840499
- Type: Article
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A high-power mode-stabilised AlGaAs laser with a buried coarctate mesa-structure (BCM) has been developed. The threshold current and the differential quantum efficiency are typically 40 mA and 56% per front facet, respectively. Fundamental-transverse-mode single-longitudinal-mode CW operation has been achieved at up to 80 mW.
Optical polarisers of high extinction ratio integrated on oxidised silicon substrate
- Author(s): G. Grand and S. Valette
- Source: Electronics Letters, Volume 20, Issue 18, p. 730 –731
- DOI: 10.1049/el:19840500
- Type: Article
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Theoretical performances of integrated polarisers realised by metallic coating of planar waveguides on oxidised silicon substrate are discussed. Measurements are reported for aluminium and chromium-gold coatings, giving extinction ratios in excess of 40 dB, with attenuations (TE polarisation) lower than 1 dB, and interaction lengths of about 2 mm.
Offset-compensated switched-capacitor leapfrog filters
- Author(s): S. Eriksson and K. Chen
- Source: Electronics Letters, Volume 20, Issue 18, p. 731 –733
- DOI: 10.1049/el:19840501
- Type: Article
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Offset-compensated SC leapfrog filters can be realised as shown in the letter. The filters are parasitic-insensitive and the switches are controlled by a 3-phase clock. A 5th-order lowpass filter is given as an example.
Integrated quantum-well-laser transmitter compatible with ion-implanted GaAs integrated circuits
- Author(s): C.S. Hong ; D. Kasemset ; M.E. Kim ; R.A. Milano
- Source: Electronics Letters, Volume 20, Issue 18, p. 733 –735
- DOI: 10.1049/el:19840502
- Type: Article
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The fabrication of an integrated optoelectronic transmitter consisting of an MOCVD-grown quantum-well laser and ion-implanted metal-semiconductor field-effect transistors (MESFETs) is described. The transmitter is characterised by a laser threshold current of 30 mA, differential quantum efficiency of 50%, MESFET transconductance of 60 mS/mm, and operation at frequencies up to 2 GHz.
Feasibility of a 1 Gbit/s/ 565 Mbit/s bidirectional single-mode-fibre subscriber line for B-ISDN using 1279 nm/ 1315 nm wavelength division multiplexing
- Author(s): K. Fussgaenger ; R. Heidemann ; W. Koester ; H. Ohnsorge ; R. Rossberg ; T. Vollmer
- Source: Electronics Letters, Volume 20, Issue 18, p. 735 –736
- DOI: 10.1049/el:19840503
- Type: Article
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A laboratory system, transmitting 1 Gbit/s signals to a subscriber station and 565 Mbit/s signals back to a head station via one 20 km-long single-mode fibre, has been realised. Wavelength division multiplexing via two 3 dB fibre couplers of selectivity ̃0.04 dB/nm has been used. The experiment demonstrates that bidirectional single-mode-fibre transmission is applicable to a future B-ISDN subscriber network.
Transformation of continuous-time model of a linear multivariable system from its discrete-time model
- Author(s): S. Puthenpura and N.K. Sinha
- Source: Electronics Letters, Volume 20, Issue 18, p. 737 –738
- DOI: 10.1049/el:19840504
- Type: Article
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The problem of identification of the state-space model of a multivariable continuous system from the samples of its input-output data is considered. Hence, a method is suggested for determining the continuous-time model of a system from its discrete-time model obtained from the samples of its input-output data.
Picosecond optoelectronic switching in semiconductors using a partly covered gap
- Author(s): V. Brückner and F. Kerstan
- Source: Electronics Letters, Volume 20, Issue 18, p. 738 –740
- DOI: 10.1049/el:19840505
- Type: Article
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The generation of picosecond electric pulses with high-voltage transmission by an optoelectronic switch with a partly covered gap and its application to time-resolved photoconductivity measurements in an ion-beam damaged SOS sample at different excitation wavelengths is reported.
Empirical formula for groundwave field-strength calculation
- Author(s): P. Knight and J.A.W. Robson
- Source: Electronics Letters, Volume 20, Issue 18, p. 740 –742
- DOI: 10.1049/el:19840506
- Type: Article
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A well known empirical formula for groundwave field-strength calculation has been found to be inaccurate under some conditions. An alternative formula which has a wider range of validity has been derived.
Minimal realisation algorithm for impulse response matrix using modified moments
- Author(s): A.M. Eydgahi and H. Singh
- Source: Electronics Letters, Volume 20, Issue 18, p. 742 –743
- DOI: 10.1049/el:19840507
- Type: Article
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A procedure for the minimal realisation of an impulse response matrix is proposed. The procedure is based on the expansion of moments of the impulse response matrix about an arbitrary point a. The procedure is illustrated with the help of an example.
Elimination of drain I/V collapse in MODFETs through the use of thin n-GaAs/AlGaAs superlattice
- Author(s): R. Fischer ; W.T. Masselink ; J. Klem ; T. Henderson ; H. Morkoç
- Source: Electronics Letters, Volume 20, Issue 18, p. 743 –744
- DOI: 10.1049/el:19840508
- Type: Article
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We report on the elimination of collapse of drain I/V characteristics in modulation-doped field-effect transistors at 77 K by replacing the doped AlGaAs with a thin GaAs/AlGaAs superlattice where only the GaAs is doped. Such thin barriers (10 Å/15 Å) are transparent to the electrons making the electron transfer into the bulk GaAs (undoped) possible. Room-temperature transconductances of 180 mS/mm which increased to 210 mS/mm at 77 K under both dark and light conditions were obtained. Furthermore, the threshold voltage of these devices did not shift appreciably on cooling (+0.12 V), and no noticeable light sensitivity at 77 K was observed for this device structure.
Integrated-optical multichannel wavelength multiplexer for monomode systems
- Author(s): A. Neyer
- Source: Electronics Letters, Volume 20, Issue 18, p. 744 –746
- DOI: 10.1049/el:19840509
- Type: Article
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A new concept of an integrated-optical multichannel wavelength multiplexer for single-mode-fibre systems is presented. The operation principle of the cascaded multiplexer is based on the periodic wavelength dependence of the two-mode-interference (TMI) in a two-mode waveguide, which is adiabatically coupled to single-mode waveguides. The multiplexer is analysed analytically and numerically (BPM), and is realised experimentally by using Ti: LiNbO3 channel waveguides.
Asymptotic expansion of a Sommerfeld integral
- Author(s): J. Walsh
- Source: Electronics Letters, Volume 20, Issue 18, p. 746 –747
- DOI: 10.1049/el:19840510
- Type: Article
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An asymptotic form is given for the Sommerfeld integral governing the electric surface field behaviour when a vertical electric dipole is located near the interface of a plane-earth model. It is shown that the expression assumes the accepted form for the case of high electric conductivities, while becoming the exact result when the earth refractive index is unity.
Simple model to calculate repeater spacings on analogue optical fibre video transmission routes
- Author(s): D.J.T. Heatley
- Source: Electronics Letters, Volume 20, Issue 18, p. 747 –749
- DOI: 10.1049/el:19840511
- Type: Article
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Analogue video transmission over a tandem connection of optical fibre systems is examined. A simple mathematical model is presented which relates section length and fibre attenuation to route length and video SNR at the final receiver. The model takes account of any analogue modulation format and applies to direct and coherent detection.
Performance of a rectangular-waveguide-excited short backfire antenna employing a conical main reflector
- Author(s): M.S. Leong and P.S. Kooi
- Source: Electronics Letters, Volume 20, Issue 18, p. 749 –751
- DOI: 10.1049/el:19840512
- Type: Article
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The letter presents experimental results at X-band for a short backfire antenna employing a conical reflector, which is excited by a rectangular waveguide. It is shown that the use of a conical main reflector can lead to a compact antenna having a directive gain of 16.7–18.3 dB, sidelobe level below 13.8 dB and input VSWR better than 2.5 over a 20% bandwidth from 9–11 GHz.
Direct measurement of second-order dispersion in short optical fibres using white-light interferometry
- Author(s): J. Stone and D. Marcuse
- Source: Electronics Letters, Volume 20, Issue 18, p. 751 –752
- DOI: 10.1049/el:19840513
- Type: Article
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We report the first direct measurement of the second-order dispersion coefficient β. The measurement was done on a 1 m-long single-mode fibre with the help of a Mach-Zehnder interferometer and a white-light source.
High-efficiency single-drift GaAs IMPATT diodes for 72 GHz
- Author(s): X. Zhang and J. Freyer
- Source: Electronics Letters, Volume 20, Issue 18, p. 752 –754
- DOI: 10.1049/el:19840514
- Type: Article
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High-efficiency GaAs single-drift IMPATT diodes have been developed up to 72 GHz using molecular-beam epitaxy. The design of the devices is based on a lower value of the electron drift velocity at high electric fields. The diodes are bonded on diamond heat sinks. The best efficiencies are 12.5% at 63 GHz with 450 mW output power and 10% at 72 GHz with 350 mW output power.
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