Online ISSN
1350-911X
Print ISSN
0013-5194
Electronics Letters
Volume 23, Issue 13, 18 June 1987
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Volume 23, Issue 13
18 June 1987
Multiplexing of interferometric sensors using phase-generated carrier techniques
- Author(s): A. Dandridge ; A.B. Tveten ; A.D. Kersey ; A.M. Yurek
- Source: Electronics Letters, Volume 23, Issue 13, p. 665 –666
- DOI: 10.1049/el:19870475
- Type: Article
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The multiplexing of four interferometric sensor outputs on a single optical fibre using a phase-generated carrier technique is demonstrated. Low crosstalk ( – 60 dB) and high performance (minimum detectable phase shifts of 2–18 μrad) were achieved with this configuration. This technique is expandable to large numbers of sensors.
Fizeau fringe interferometer for fibre outside diameter measurements
- Author(s): M.S. O'Sullivan and D.W. Gransden
- Source: Electronics Letters, Volume 23, Issue 13, p. 666 –668
- DOI: 10.1049/el:19870476
- Type: Article
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A simple interferometer for making accurate outside diameter measurements of optical fibre is described. The apparatus, which measures the diameter in terms of Fizeau fringes, is easy to implement, requires minimal alignment and can be constructed from low-cost components. The device has a precision of ±0.03 μm and an ultimate accuracy of 1 part in 106.
New design concept for a narrowband wavelength-selective optical tap and combiner
- Author(s): D.C. Johnson ; K.O. Hill ; F. Bilodeau ; S. Faucher
- Source: Electronics Letters, Volume 23, Issue 13, p. 668 –669
- DOI: 10.1049/el:19870477
- Type: Article
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A novel design is proposed for a four-port optical tap that extracts efficiently from a fibre in which light containing several discrete wavelength bands is propagating only that light within one such band. The same device can be used simultaneously to combine light of the same wavelength as the extracted light with the other, unselected, wavelength bands.
370 mW, 1.06 μm, CW TEM00 output from an Nd:YAG laser rod end-pumped by a monolithic diode array
- Author(s): J. Berger ; D.F. Welch ; D.R. Scifres ; W. Streifer ; P.S. Cross
- Source: Electronics Letters, Volume 23, Issue 13, p. 669 –670
- DOI: 10.1049/el:19870478
- Type: Article
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We report 370 mW CW output at 1.06 μm in the TEM∞ mode with 9.1% electrical to optical (wall-plug) conversion efficiency from an Nd:YAG laser rod end-pumped by a monolithic 100 μm-wide diode laser array.
Double diffraction by wedges in nonperfectly conducting surfaces
- Author(s): G. Manara ; R. Tiberio ; G. Pelosi ; P.H. Pathak ; R.G. Kouyoumjian
- Source: Electronics Letters, Volume 23, Issue 13, p. 671 –672
- DOI: 10.1049/el:19870479
- Type: Article
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A high-frequency solution is obtained via an extended ray method for the field doubly diffracted in the far zone by a pair of parallel wedges with impedance faces, when they are illuminated by a plane wave perpendicularly incident on the edges. Except for a multiplying special function, this solution is expressed in closed form, which is valid for any incidence and observation aspects.
High-power CW operation of 780 nm T3 laser diodes
- Author(s): A. Shima ; T. Yamawaki ; H. Saito ; H. Matsubara ; T. Murakami ; K. Ohtaki ; H. Kumabe ; W. Susaki
- Source: Electronics Letters, Volume 23, Issue 13, p. 672 –674
- DOI: 10.1049/el:19870480
- Type: Article
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Stable laser operation at over 100 mW in the wavelength range of 780nm has been achieved by the T3 structure. The CW light output power at room temperature was over 160mW. The narrow beam divergence of low ellipticity has been realised. The lasers have been in operation for more than 800h at 40mW at 60°C with no significant degradation.
Iterative method for obtaining the argument of the dominant complex pole-pair
- Author(s): S. Puthenpura and N.K. Sinha
- Source: Electronics Letters, Volume 23, Issue 13, p. 674 –675
- DOI: 10.1049/el:19870481
- Type: Article
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A simple and efficient method is presented for obtaining the argument of the dominant complex pole-pair of a discrete-time system. This new method can be directly applied to either the system characteristic polynomial or the state transition matrix, whichever is available. Moreover, it can easily be extended to extract the values of the arguments of all complex pole-pairs of the system under consideration.
Broadband continuously variable microwave phase shifter employing a distributed Schottky contact on silicon
- Author(s): V.M. Hietala ; Y.R. Kwon ; K.S. Champlin
- Source: Electronics Letters, Volume 23, Issue 13, p. 675 –677
- DOI: 10.1049/el:19870482
- Type: Article
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Fabrication details and microwave measurements are presented for the first realisation of a silicon, broadband, voltage-controlled, microwave phase shifter comprising a coplanar, slow-wave, Schottky-contact transmission line. This structure exhibits very little dispersion over the measured frequency range of 1–20 GHz. A voltage-dependent ‘wave compression’ factor is observed that can be varied from 11.7 to 17.0 by varying the bias between −6 and +0.1 V. Even though the device is fabricated on a ‘true’ (lossy) semiconducting substrate, the attenuation per unit length is smaller than that reported for a similar structure fabricated on semi-insulating GaAs.
Simple method for analysing finlines with extremely narrow slotwidth and thick fins
- Author(s): Xu Shanjia
- Source: Electronics Letters, Volume 23, Issue 13, p. 677 –678
- DOI: 10.1049/el:19870483
- Type: Article
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Most numerical methods suffer from serious convergence problems when they are used in analysing finlines with extremely narrow slotwidth, and often do not consider the effect of fin thickness. The method presented can solve these problems successfully, and is proved to be effective and useful.
Modelling microstrip step discontiuities by the transmission matrix
- Author(s): J.S. Hong and J.M. Shi
- Source: Electronics Letters, Volume 23, Issue 13, p. 678 –679
- DOI: 10.1049/el:19870484
- Type: Article
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The transmission matrix is applied to characterise general microstrip step discontinuities based on the waveguide model. Considerably more CPU time can be saved compared to the scattering matrix.
Optical feed for a phased array microwave antenna
- Author(s): M. Tamburrini ; M. Parent ; L. Goldberg ; D. Stillwell
- Source: Electronics Letters, Volume 23, Issue 13, p. 680 –681
- DOI: 10.1049/el:19870485
- Type: Article
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p.
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Microwave signals for all array elements in a phared array microwave antenna are simultaneously generated by spatial sampling of a moving sinusoidal interference pattern formed between two frequency-offset injection-locked laser diodes. The offset and radar frequency of 3.2 GHz were generated by a Bragg cell. A nearly distortionless antenna beam pattern and 180° steering are demonstrated in a linear seven-element array.
Capacities of sequences of currently used ternary line codes
- Author(s): J.F. Hope ; H.C. Ferreira ; A.L. Nel
- Source: Electronics Letters, Volume 23, Issue 13, p. 681 –683
- DOI: 10.1049/el:19870486
- Type: Article
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The sequences generated by the ternary line codes of PCM systems and digital networks are constrained in order to satisfy the modulation requirements of the channels on which these codes are used. We present the capacities, in bits/symbol, of such constrained sequences corresponding to the HDB3, B6ZS, 4B3T and MS43 codes.
Novel type of fibre-optic ring resonator
- Author(s): E. Meissner
- Source: Electronics Letters, Volume 23, Issue 13, p. 683 –684
- DOI: 10.1049/el:19870487
- Type: Article
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A fibre-optic ring resonator with highly wavelength-selective input reflection coefficient was realised by introducing a small local reflection in the ring. The influence of the local reflectivity on the input reflection coefficient is demonstrated. Maximum values for the input reflectivity and finesse are 55% and 10, respectively, using a fibre directional coupler (FDC) with a coupling ratio of 30%/70%.
Nondiffusion and 1.54/μm luminescence of erbium implanted in InP
- Author(s): P.N. Favennec ; H. L'Haridon ; A. le Corre ; M. Salvi ; M. Gauneau
- Source: Electronics Letters, Volume 23, Issue 13, p. 684 –686
- DOI: 10.1049/el:19870488
- Type: Article
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Erbium impurities were implanted in indium phosphide. The Er depth distributions are given for nonannealed and annealed substrates. It is shown that erbium has a very small diffusion coefficient, if any, in InP. The photoluminescence spectra show, after annealing at high temperature, the main erbium emission centred at 1.536μm. This emission is stronger after annealing at 700°C. Our results are the first evidence showing l.54μm emission at room temperature.
Narrow pulse measurement of drain characteristics of GaAs MESFETs
- Author(s): T.M. Barton ; C.M. Snowden ; J.R. Richardson ; P.H. Ladbrooke
- Source: Electronics Letters, Volume 23, Issue 13, p. 686 –687
- DOI: 10.1049/el:19870489
- Type: Article
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A measurement technique is presented which uses narrow, fast-rise-time pulses applied to both the gate and the drain of a GaAs MESFET to obtain the drain characteristics of the device. This allows the characteristics of the device to be obtained which correspond to frequencies above those at which surface and substrate traps can respond. The resulting characteristics show significant departures from those obtained using conventional long pulse and DC measurement techniques.
Coherent transmission using an external waveguide Bragg reflector laser with direct frequency modulation
- Author(s): N.A. Olsson ; B.H. Johnson ; H.J. Lee ; C.H. Henry ; R.F. Kazarinov ; D.A. Ackerman ; P.J. Anthony
- Source: Electronics Letters, Volume 23, Issue 13, p. 687 –689
- DOI: 10.1049/el:19870490
- Type: Article
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Single-frequency l.5μm semiconductor lasers, formed by butt-coupling of a regular Fabry—Perot laser to an external waveguide Bragg reflector, are shown to have very uniform frequency modulation characteristics under direct current modulation. The laser's frequency modulation characteristics, together with its narrow linewidth (̃ 1 MHz), make coherent transmission possible without external modulators. The laser performance was evaluated in a 417Mbit/s, 102 km, frequency-shift-keying coherent transmission experiment.
Alignment of polarisation-maintaining fibres by temperature modulation
- Author(s): G.R. Walker and N.G. Walker
- Source: Electronics Letters, Volume 23, Issue 13, p. 689 –691
- DOI: 10.1049/el:19870491
- Type: Article
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A novel nondestructive technique for rapidly aligning the input state of polarisation to a stress-effect polarisation-maintaining fibre has been implemented using temperature modulation. It can be applied easily on to a short length of fibre, gives alignment to better than 0.5°, and can identify the fast and slow axes.
Experimental determination of finline post discontinuity parameters: application to stopband and lowpass filters
- Author(s): P. Saguet and A. Essebar
- Source: Electronics Letters, Volume 23, Issue 13, p. 691 –692
- DOI: 10.1049/el:19870492
- Type: Article
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The shunt reactance of a finline post discontinuity is shown to be of resonant type. By using an experimental transmission procedure, we have determined accurately the parameters R, L and C of its equivalent circuit. These parameters, in the first approximation, can be considered as frequency-independent. Thus the use of the equivalent circuit in CAD is very easy. Applications to stopband and lowpass filters are described.
Bidirectional optical transmission using polarised light waves
- Author(s): Y. Sasaki ; K. Tajima ; I. Yokohama
- Source: Electronics Letters, Volume 23, Issue 13, p. 692 –694
- DOI: 10.1049/el:19870493
- Type: Article
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Bidirectional optical transmission using polarised light waves is demonstrated for the first time. Transmission of 100 Mbit/s signals over 13.6 km of polarisation-maintaining fibre occurs simultaneously in both directions at 1.55/μm. LD transmitters with polarisation-maintaining fibre pigtails, polarisation-maintaining fibre couplers, fibre polarisers and Ge-APD receivers are used.
Analysis of microstripline coupled to microstrip antenna
- Author(s): X.Z. Gao and K. Chang
- Source: Electronics Letters, Volume 23, Issue 13, p. 694 –695
- DOI: 10.1049/el:19870494
- Type: Article
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An analytical method based on the aperture coupling theory and S-parameter matrix has been developed for modelling a microstripline coupled to a microstrip antenna using a circular coupling aperture. The theoretical results agree fairly well with the measurements. The analysis should have many applications in active array developments.
Fast CMOS current amplifier and buffer stage
- Author(s): G.C. Temes and W.H. Ki
- Source: Electronics Letters, Volume 23, Issue 13, p. 696 –697
- DOI: 10.1049/el:19870495
- Type: Article
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A novel CMOS current amplifier stage is described which provides a low impedance and an accurately controlled DC bias voltage at its input terminal, as well as an accurate current gain in a wide frequency range.
Zero-crossing estimation in signal generation of narrowband digital angle-modulated signals
- Author(s): K.S. Chung
- Source: Electronics Letters, Volume 23, Issue 13, p. 697 –699
- DOI: 10.1049/el:19870496
- Type: Article
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It is shown that a zero-crossing estimator (ZCE), based on sinusoidal interpolation and realised with digital circuitry, can be used in place of a conventional DAC in signal generation of narrowband digital angle-modulated signals. An example of generating a GTFM signal with this ZCE is described.
Laser interferometer using a dual interference method
- Author(s): K.H. Yang ; L. Chen ; S.Y. Zhang
- Source: Electronics Letters, Volume 23, Issue 13, p. 699 –700
- DOI: 10.1049/el:19870497
- Type: Article
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A stabilised Michelson interferometer system using a new interference mode has been developed, in which a specially designed beam-splitter produces two complementary interference patterns. With differential detection, the laser intensity noise is efficiently eliminated, and the system is simpler and stabler. The measured displacement sensitivity is 10−2 Ȧ/ √(HZ).
Efficient frequency-doubling in a poled PVDF copolymer guest/host composite
- Author(s): J.R. Hill ; P.L. Dunn ; G.J Davies ; S.N Oliver ; P. Pantelis ; J.D. Rush
- Source: Electronics Letters, Volume 23, Issue 13, p. 700 –701
- DOI: 10.1049/el:19870498
- Type: Article
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We describe the linear and nonlinear properties of a new polymer composite, which uses a ferroelectric PVDF copolymer host in which an optically nonlinear low-molecularweight guest is dissolved and subsequently aligned using a room-temperature poling process. We have measured the frequency-doubling coefficient d33 of these poled composites at 1-064/mi to be as high as 2-6 × 10−12m/V. In addition, we have shown that this material may be formed into waveguiding structures with an acceptable optical loss (̃5dB/cm), as is needed in many signal processing systems.
Low-loss single-mode InP/InGaAsP waveguides grown by MOVPE
- Author(s): P.W.A. McIlroy ; P.M. Rodgers ; J.S. Singh ; P.C. Spurdens ; I.D. Henning
- Source: Electronics Letters, Volume 23, Issue 13, p. 701 –703
- DOI: 10.1049/el:19870499
- Type: Article
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Losses as low as 0.4 ± 0.1 dB/cm for TE- and 0.65 ± 0.1 dB/ cm for TM-polarised light have been observed in tightly confined single-mode InP/lnGaAsP waveguides grown by MOVPE and processed using RIE. These are the lowest losses reported for InP-based waveguides. The structure could be used to make low-loss modulators for communications wavelengths.
8.8 Gbit/s travelling-pulse word generator
- Author(s): N. Mulombe ; J. Kahlert ; W. Piscalar ; G. Seehausen
- Source: Electronics Letters, Volume 23, Issue 13, p. 703 –704
- DOI: 10.1049/el:19870500
- Type: Article
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A word generator using a delay-line travelling-pulse concept similar to the well known travelling-wave amplifier is presented. Operation up to 8.8 Gbit/s has been demonstrated experimentally. The circuits are realised in the hybrid microstrip technique using discrete normally-on GaAs MESFETs.
Boundary conditions of the electromagnetic field
- Author(s): M. Idemen and A.H. Serbest
- Source: Electronics Letters, Volume 23, Issue 13, p. 704 –705
- DOI: 10.1049/el:19870501
- Type: Article
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The classical boundary conditions describing the discontinuities of the electromagnetic field across a surface supporting ordinary surface charges and currents are discussed in the case where nontangential currents and polarisations of higher orders are possible.
Improved negative feedback technique to reduce drain conductance of GaAs MESFETs for precision analogue ICs
- Author(s): W.S. Lee and J. Mun
- Source: Electronics Letters, Volume 23, Issue 13, p. 705 –707
- DOI: 10.1049/el:19870502
- Type: Article
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An improved negative feedback technique to reduce the absolute magnitude of the frequency-dependent drain conductance inherent in GaAs MESFETs has been demonstrated for low-threshold (less than −1 V) devices. The new dual-threshold arrangement guarantees that the primary device of the self-bootstrapping pair operates at the current saturation region without relying on the existence of early saturation. A factor of 11 reduction in the drain conductance was realised. A simple inverter amplifier of identical composite driver and load has demonstrated 21 dB improvement in voltage gain over that using single FETs.
Cramer-Rao lower bound for cascaded adaptive notch filtering
- Author(s): J.F. Chicharo and T.S. Ng
- Source: Electronics Letters, Volume 23, Issue 13, p. 707 –708
- DOI: 10.1049/el:19870503
- Type: Article
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A minimal parameter infinite-impulse-response (IIR) cascaded adaptive notch filter is presented for the estimation of a single sinusoid embedded in noise. The Cramer-Rao lower bound (CRLB) is derived for the suggested filter which takes into account both the sinusoid and noise components. This leads to a more precise performance evaluation of the filter.
Equivalent circuit for aperture antennas
- Author(s): A.W. Love
- Source: Electronics Letters, Volume 23, Issue 13, p. 708 –710
- DOI: 10.1049/el:19870504
- Type: Article
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The commonly used equivalent circuit based on a constant voltage generator does not correctly characterise scattering by an aperture antenna, nor does its dual, the constant current generator. This long-standing dilemma has been resolved by combining voltage and current sources to form a constant-power source. The power generated by this source is equated to the available power in a plane wave incident on the aperture. The voltage and current of the two sources and their respective internal impedances are then completely determined from a knowledge of the aperture area A0, the impedance ZA, the aperture efficiency η0 and the relative power pattern p(θ, Φ) of the antenna.
Erratum: Front-to-back ratio of a smooth metallic-wall conical horn
- Author(s): C.M. Knop
- Source: Electronics Letters, Volume 23, Issue 13, page: 710 –710
- DOI: 10.1049/el:19870505
- Type: Article
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