Online ISSN
1350-911X
Print ISSN
0013-5194
Electronics Letters
Volume 21, Issue 14, 4 July 1985
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Volume 21, Issue 14
4 July 1985
Clock sensitivity reduction in echo cancellers
- Author(s): S.A. Cox
- Source: Electronics Letters, Volume 21, Issue 14, p. 585 –586
- DOI: 10.1049/el:19850412
- Type: Article
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An algorithm is presented which enables echo cancellers to track rapid sample phase variations.
Variable-delay, sine/cosine noncoherent detector
- Author(s): W. Rafferty and G.J. Saulnier
- Source: Electronics Letters, Volume 21, Issue 14, p. 586 –587
- DOI: 10.1049/el:19850413
- Type: Article
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The letter describes an all-digital, noncoherent demodulator suitable for the detection of CPFSK and PSK signalling schemes. A single A/D convertor demodulates the input signal and generates baseband in-phase (I) and quadrature (Q) signals. The I and Q signals are then processed with sine and cosine detectors to produce AFC information and the regenerated transmit data.
Two-dimensional impurity profiling near the mask edge using anodisation
- Author(s): C.M. Kyung
- Source: Electronics Letters, Volume 21, Issue 14, p. 587 –588
- DOI: 10.1049/el:19850414
- Type: Article
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An experimental scheme for measuring the two-dimensional impurity profile near the mask edge is described, based on forming a U-groove in silicon by anisotropic etching leaving only the sidewall resistors. 2-D impurity profiling of the sidewall resistor is achieved by constant-voltage anodisation and etching the resultant oxide. An n × m resistor array structure for simultaneously obtaining the 2-D impurity profile is also described.
Use of bilinear terminations for LDI-type SC ladder filters
- Author(s): P.V. Mohan Ananda
- Source: Electronics Letters, Volume 21, Issue 14, p. 588 –589
- DOI: 10.1049/el:19850415
- Type: Article
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The use of bilinear terminations in a class of LDI-type SC ladder filters has been shown to result in instability.
Measurement of single-mode optical-fibre spot size using strip integration of far field
- Author(s): P.J. Samson
- Source: Electronics Letters, Volume 21, Issue 14, p. 589 –591
- DOI: 10.1049/el:19850416
- Type: Article
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We present a new technique for the measurement of the far-field RMS spot size of a single-mode optical fibre based on strip integration of the far-field pattern. The method is suitable for use with a white light source and can thus measure the spectral variance of the spot size.
Noise-proof phase meter with switched lowpass filters
- Author(s): J. Siuzdak
- Source: Electronics Letters, Volume 21, Issue 14, p. 591 –592
- DOI: 10.1049/el:19850417
- Type: Article
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A noise-resistant phase meter has been described, which comprises two switched lowpass filters. It has no systematic errors, even for low SNR. Results of the measurements have been presented.
Conditions for obtaining zero polarisation mode dispersion in elliptical-core fibres
- Author(s): K.S. Chiang
- Source: Electronics Letters, Volume 21, Issue 14, p. 592 –593
- DOI: 10.1049/el:19850418
- Type: Article
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It is shown that zero polarisation mode dispersion can never be achieved in elliptical-core single-mode fibres by geometrical birefringence alone. To equalise the group delays of the two fundamental modes, stress-induced birefringence must be introduced to cancel, partly or completely, the geometrical birefringence, depending on the application.
Ultra-low-capacitance flip-chip-bonded GaInAs PIN photodetector for long-wavelength high-data-rate fibre-optic systems
- Author(s): R.S. Sussmann ; R.M. Ash ; A.J. Moseley ; R.C. Goodfellow
- Source: Electronics Letters, Volume 21, Issue 14, p. 593 –595
- DOI: 10.1049/el:19850419
- Type: Article
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A novel GaInAs substrate illuminated photodetector structure is reported for the 1.0–1.7 μm wavelength range with capacitance as low as 0.02 pF, packaging stray capacitance below 0.02 pF, 97% quantum efficiency and subnanoampere leakage current. The device is rugged, epoxy-free, does not use an integral fibre pig-tail and wire bonding to the detector chip is not required.
Numerical analysis of MOS transistor effective channel width
- Author(s): A.M. Asenov ; E.N. Stefanov ; B.Z. Antov
- Source: Electronics Letters, Volume 21, Issue 14, p. 595 –597
- DOI: 10.1049/el:19850420
- Type: Article
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The effect of modulation of the effective width of a narrow-channel MOST by the gate voltage is demonstrated using a two-dimensional integral MOS process and device similator. The realistic shapes of the ‘bird's beak’ and doping concentrations allow a numerical analysis of this effect to be made for typical enhancement- and depletion-mode devices, as well as a comparison with the experiment.
Low-loss GaAs/GaAlAs strip-loaded waveguides with high coupling efficiency to single-mode fibres
- Author(s): S.H. Lin ; S.Y. Wang ; S.A. Newton ; Y.M. Houng
- Source: Electronics Letters, Volume 21, Issue 14, p. 597 –598
- DOI: 10.1049/el:19850421
- Type: Article
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We report measurements of low-loss MOVPE-grown GaAlAs/GaAs strip-loaded waveguides with high coupling efficiency to single-mode fibres. A propagation loss of 2 dB/cm and a coupling efficiency of 70% has been achieved for a p+-i-n+-structure waveguide. A propagation loss of 0.7 dB/cm and a coupling efficiency of 61% has also been achieved for an n−-i-n−-structure waveguide.
Direct frequency modulation of a semiconductor laser by surface acoustic waves
- Author(s): P.A. Greenhalgh and P.A. Davies
- Source: Electronics Letters, Volume 21, Issue 14, p. 598 –599
- DOI: 10.1049/el:19850422
- Type: Article
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Frequency-modulated signals in the output of a semiconductor laser are generated by applying surface acoustic waves to the device. The SAW modulator is discussed and theoretical and experimental results are compared.
Degradation mechanisms induced by temperature in power MESFETs
- Author(s): C. Canali ; F. Fantini ; L. Umena ; E. Zanoni
- Source: Electronics Letters, Volume 21, Issue 14, p. 600 –601
- DOI: 10.1049/el:19850423
- Type: Article
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Two independent failure mechanisms, mainly induced by temperature, were observed in unpassivated, Au-metallised, commercially available power MESFETs. They result in a high gate/source (drain) leakage and in an increase in the open channel resistance, and may explain the ‘burn-out’ of the devices in practical applications.
Modulation scheme suitable for infra-red biotelemetry
- Author(s): C. Weller
- Source: Electronics Letters, Volume 21, Issue 14, p. 601 –602
- DOI: 10.1049/el:19850424
- Type: Article
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Telemetering physiological signals from hospital patients by time-sharing infra-red radiation of fixed wavelength means that the limited time available for encoding each data channel imposes constraints on modulation methods. Analogue and digital modulation methods are compared and an unconventional pulse code is proposed.
Reduction of absorption losses in ZrF4-based IR fibres
- Author(s): P.W. France ; S.F. Carter ; M.W. Moore ; J.R. Williams
- Source: Electronics Letters, Volume 21, Issue 14, p. 602 –603
- DOI: 10.1049/el:19850425
- Type: Article
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By incorporating oxidising gases into the melt atmosphere during the fabrication of ZrF4-based IR fibres, it has been possible to reduce absorption due to Fe2+ to extremely low levels. This was accompanied by an increase in loss from Cu2+, but this absorption tails off rapidly beyond 1.5 μm. Overall absorption losses have been reduced to the order of 2 dB/km at 2.5 μm, estimated to have arisen from other 3d transition metals and some rare earths.
High-power (575 mW) single-lobed emission from a phased-array laser
- Author(s): D.F. Welch ; D. Scifres ; P. Cross ; H. Kung ; W. Streifer ; R.D. Burnham ; J. Yaeli
- Source: Electronics Letters, Volume 21, Issue 14, p. 603 –605
- DOI: 10.1049/el:19850426
- Type: Article
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Phased-array lasers which emit up to 575 mW in a 1.9 degree (FWHM) single far-field lobe corresponding to the lowest-order supermode are described. Single-lobe operation is achieved in lasers whose stripes are offset near the facet by half a period from the stripes in the central part of the cavity and are linearly chirped across the diode. This stripe geometry tends to lower the threshold of the single-lobe mode relative to that of the undesired double-lobe mode.
High-speed GaAs SCFL divider
- Author(s): A. Tamura ; T. Sakashita ; T. Uenoyama ; K. Nishii ; T. Tambo ; K. Nagano ; T. Onuma
- Source: Electronics Letters, Volume 21, Issue 14, p. 605 –606
- DOI: 10.1049/el:19850427
- Type: Article
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A single-clocked divide-by-four circuit with a maximum operating frequency of 5.2 GHz has been developed. The circuit was fabricated using 1 μm-gatelength high-transconductance enhancement-mode GaAs MESFETs with Pt-buried gate structure. The basic building block of the circuit is a source-coupled FET logic (SCFL) master-slave flip-flop with ECL-compatible input and output.
Numerical analysis of an axial-mode zigzag antenna
- Author(s): H. Nakano ; H. Tagami ; J. Yamauchi
- Source: Electronics Letters, Volume 21, Issue 14, p. 606 –608
- DOI: 10.1049/el:19850428
- Type: Article
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The radiation characteristics of an axial-mode zigzag antenna are evaluated on the basis of the numerically determined current distribution. It is revealed that the frequency at which the maximum gain is obtained decreases as the number of zigzag cells is increased, and that an antenna of two zigzag cells has a high power gain of about 11 dB with a bandwidth of about 11%, although the number of zigzag cells is extremely small.
Easy calculation of power spectra for multi-h phase-coded signals
- Author(s): M. Luise
- Source: Electronics Letters, Volume 21, Issue 14, p. 608 –609
- DOI: 10.1049/el:19850429
- Type: Article
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The letter presents an easy method which allows a fast calculation of the spectra of M-ary multi-h phase-coded signals under very general conditions for the shape of the modulating pulse.
Effective calculation method for laser-diode/multimode-fibre coupling
- Author(s): K. Kawano ; H. Miyazawa ; O. Mitomi
- Source: Electronics Letters, Volume 21, Issue 14, p. 609 –611
- DOI: 10.1049/el:19850430
- Type: Article
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A simple and useful calculation method for obtaining an InGaAsP laser-diode/multimode-fibre coupling characteristic is presented. The attenuation effects of higher-order modes in the multimode fibre are introduced into the ray tracing. Agreement between theoretical and experimental coupling characteristics is greatly improved in comparison to that for the conventional ray tracing.
Application of maximum entropy spectral analysis to estimation of parameters of ARMA models by the ITIF method
- Author(s): R. Gómez Martín ; M.C. Carrión Perez ; S. Al Khouri Ibrahim ; B. García Olmedo
- Source: Electronics Letters, Volume 21, Issue 14, p. 611 –613
- DOI: 10.1049/el:19850431
- Type: Article
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In the letter we show how it is possible to improve the results obtained by the ITIF method, modelling a deterministic, linear, time-invariant system through a rational function in the z-domain, when the input of the system is a white-noise signal. This is achieved by using the maximum entropy method (Burg algorithm) during the deconvolution stage instead of the covariance method.
Refractometry through optical frequency-domain reflectometry
- Author(s): T.T. Tjhung ; S.K. Teo ; F.V.C. Mendis ; B. Selvan
- Source: Electronics Letters, Volume 21, Issue 14, p. 613 –614
- DOI: 10.1049/el:19850432
- Type: Article
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A refractometer for liquids, based on optical frequency-domain reflectometry, is described which uses a simple fibre probe with minimal contact area with the test liquid. The sensitivity is much better than in earlier reported fibre refractometers.
Reproducible low-resistivity AuMn ohmic contact for p-type GaAs
- Author(s): C. Dubon-Chevallier ; A.M. Duchenois ; J.F. Bresse ; D. Ankri
- Source: Electronics Letters, Volume 21, Issue 14, p. 614 –615
- DOI: 10.1049/el:19850433
- Type: Article
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A novel ohmic contact 96% Au-4% Mn has been established for p-type GaAs. A specific contact resistivity of 2 × 10−7 Ωcm2 has been obtained on 2 × 1019 cm−3 epitaxial layers after alloying, and a resistivity of 2 × 10−6 Ωcm2 has been obtained on 2 × 1020 cm−3 doped layers without alloying. The contact is stable and reproducible.
Waveguide E-plane integrated-circuit diplexer
- Author(s): F. Arndt ; J. Bornemann ; D. Grauerholz ; D. Fasold ; N. Schroeder
- Source: Electronics Letters, Volume 21, Issue 14, p. 615 –617
- DOI: 10.1049/el:19850434
- Type: Article
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A waveguide diplexer is introduced where optimised low-insertion-loss metal insert filters are directly integrated in the E-planes of the T-junction arms. The filters are designed by the exact method of field expansion into suitable eigenmodes which takes the influences of higher-order-mode interaction and finite thickness of the inserts into account. Computer optimised design data are given which provide a metaletching technique for reliable low-cost production. Measured minimum passband insertion losses of an R120-waveguide diplexer prototype are about 0.8 dB at 10.4 GHz, and 0.5 dB at 11.2 GHz. The stopband attenuation at 10.8 GHz is about 48 dB.
Crosspolarisation due to radial field components in reflector antennas
- Author(s): R.I. Henderson
- Source: Electronics Letters, Volume 21, Issue 14, p. 617 –618
- DOI: 10.1049/el:19850435
- Type: Article
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The letter stresses the importance of including the radial component of the transmit field of the feed horn when analysing reflector antennas. Omission of this component leads to errors in the prediction of crosspolar patterns similar in magnitude to those produced by diffraction effects within a dual reflector antenna.
1 × n optical fibre switch
- Author(s): A. El Fatatry
- Source: Electronics Letters, Volume 21, Issue 14, p. 618 –619
- DOI: 10.1049/el:19850436
- Type: Article
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A variety of techniques to realise optical fibre switching using multimode fibres have been reported in the literature. Most of these techniques, however, either exhibit high insertion losses or are limited in switching configurations to 1 × 2 or 2 × 2 structures. In the letter we report a mechanical 1 × 8 optical fibre switch with maximum insertion losses of 1 dB with 50 μm-core fibres. The switching technique described is suitable for expansion into larger 1 × n configurations.
1.3 Gbit/s transmission over 107 km of dispersion-shifted monomode fibre using a 1.55 μm multimode laser
- Author(s): K.L. Monham ; R. Plastow ; A.C. Carter ; R.C. Goodfellow
- Source: Electronics Letters, Volume 21, Issue 14, p. 619 –620
- DOI: 10.1049/el:19850437
- Type: Article
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1.3 Gbit/s has been transmitted over 107 km of dispersion-shifted monomode fibre using a 1.55 μm multimode laser and a GaInAs PINFET receiver, demonstrating the viability of using non-mode-stabilised lasers in long-haul high-bit-rate optical transmission systems.
Comment: Probability density function of amplitude scintillations
- Author(s): E. Vilar and T.J. Moulsley
- Source: Electronics Letters, Volume 21, Issue 14, p. 620 –621
- DOI: 10.1049/el:19850438
- Type: Article
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Reply: Probability density function of amplitude scintillations
- Author(s): G. Ortgies
- Source: Electronics Letters, Volume 21, Issue 14, p. 621 –622
- DOI: 10.1049/el:19850439
- Type: Article
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Outage probability in a mobile radio system subject to fading and shadowing
- Author(s): A.G. Williamson and J.D. Parsons
- Source: Electronics Letters, Volume 21, Issue 14, p. 622 –623
- DOI: 10.1049/el:19850440
- Type: Article
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Outage probability calculations are presented for the case when the transmission from a wanted base station is received at a mobile in the presence of an interfering cochannel signal, and reception is subject to fading and shadowing. These calculations consider the joint requirement that for satisfactory reception both an adequate signal and an acceptable signal/interference ratio are required simultaneously.
Polarising beamsplitter from fused-taper couplers
- Author(s): A.W. Snyder
- Source: Electronics Letters, Volume 21, Issue 14, p. 623 –625
- DOI: 10.1049/el:19850441
- Type: Article
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We give the theoretical principles for polarising beam splitters constructed from fused-taper couplers, including the role of stress and form birefringence, the interaction length and the spectral response, all as a function of the physical parameters.
Reduction of absorption loss due to iron ions in fluoride glasses
- Author(s): T. Nakai ; Y. Mimura ; H. Tokiwa ; O. Shinbori
- Source: Electronics Letters, Volume 21, Issue 14, p. 625 –626
- DOI: 10.1049/el:19850442
- Type: Article
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A new approach to the reduction of absorption loss due to iron ions in fluoride glasses is reported. The absorption loss has been substantially reduced by oxidising ferrous to ferric ions under an NF3 atmosphere.
Contribution of spontaneous emission to the linewidth of an injection-locked semiconductor laser
- Author(s): P. Gallion ; H. Nakajima ; G. Debarge ; C. Chabran
- Source: Electronics Letters, Volume 21, Issue 14, p. 626 –628
- DOI: 10.1049/el:19850443
- Type: Article
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We show that the spontaneous emission inside an injection-locked semiconductor laser does not alter the lasing field. For injection at the free-running frequency, the linewidth is only governed by the injected-field phase noise and may no longer follow the Schawlow-Townes dependence on emitted optical power.
Bidirectional transmission over 11 km of single-mode optical fibre at 34 Mbit/s using 1.3 μm LEDs and directional couplers
- Author(s): R.D. Hall ; R.A. Betts ; J.P. Moss
- Source: Electronics Letters, Volume 21, Issue 14, p. 628 –629
- DOI: 10.1049/el:19850444
- Type: Article
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Results of a laboratory trial are reported in which bidirectional transmission at 34 Mbit/s over 11 km of single-mode fibre was demonstrated using 1.3 μm ELEDs, single-mode fused biconical tapered couplers and GaInAs PINFET receivers.
Registration mark detection for scanning ion beam lithography
- Author(s): A.F. Evason ; J.R.A. Cleaver ; P.J. Heard ; H. Ahmed
- Source: Electronics Letters, Volume 21, Issue 14, p. 629 –630
- DOI: 10.1049/el:19850445
- Type: Article
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The application of scanning ion beam lithography techniques to microelectronic device fabrication requires an ability to register the ion beam to features on the device. Imaging procedures have been investigated, and registration marks have been imaged with good contrast and resolution.
Optical time-division space switches using tree-structured directional couplers
- Author(s): K. Habara and K. Kikuchi
- Source: Electronics Letters, Volume 21, Issue 14, p. 631 –632
- DOI: 10.1049/el:19850446
- Type: Article
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The letter proposes two optical time-division space-switch structures using tree-structured directional couplers. First-order approximations show that they have an excellent signal/crosstalk ratio and low-loss properties in a large matrix dimension. An experiment on a 4 × 4 switch using Ti:LiNbO3 directional couplers is presented under the 128 Mbit/s condition.
Erratum: Probability density function of amplitude scintillations
- Author(s): G. Ortgies
- Source: Electronics Letters, Volume 21, Issue 14, page: 632 –632
- DOI: 10.1049/el:19850447
- Type: Article
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