Online ISSN
1350-911X
Print ISSN
0013-5194
Electronics Letters
Volume 16, Issue 24, 20 November 1980
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Volume 16, Issue 24
20 November 1980
Explicit formula for filter function of maximally flat nonrecursive digital filters
- Author(s): M.U.A. Bromba and H. Ziegler
- Source: Electronics Letters, Volume 16, Issue 24, p. 905 –906
- DOI: 10.1049/el:19800644
- Type: Article
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–906
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A general formula for the filter function of maximally flat f.i.r. digital filters using modified Krawtchouk polynomials is presented. This formula permits a direct calculation of the filter weights. It is especially advantageous for either high or low passband/stopband width ratios.
Microwave power amplification with InP f.e.t.s
- Author(s): M. Armand ; J. Chevrier ; Nuyen T. Linh
- Source: Electronics Letters, Volume 16, Issue 24, p. 906 –907
- DOI: 10.1049/el:19800645
- Type: Article
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–907
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InP f.e.t.s were fabricated from v.p.e. layers, with an Al gate of 1.5 μm × 308 μm. The power output at 9 GHz, with 4 dB gain, was 1.15 W/mm gate width. This result is believed to be higher than the best published results obtained with equivalent GaAs f.e.t. structures.
Polarisation mode dispersion measurements in long single mode fibres
- Author(s): M. Monerie ; P. Lamouler ; L. Jeunhomme
- Source: Electronics Letters, Volume 16, Issue 24, p. 907 –908
- DOI: 10.1049/el:19800646
- Type: Article
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–908
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A frequency domain determination of polarisation mode dispersion in single mode fibres is described, which allows one to obtain directly the group delay difference for long fibres. The results of such measurements are shown on a birefringent fibre with elliptical cross-section which maintains an extinction ratio between linearly polarised eigenstates greater than 10 dB over 1 km.
Design of s.a.w. convolver for processing m.s.k. modulated waveforms
- Author(s): H. Engan ; K.A. Ingebrigtsen ; A. Rønnekleiv
- Source: Electronics Letters, Volume 16, Issue 24, p. 908 –909
- DOI: 10.1049/el:19800647
- Type: Article
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–909
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An acoustic waveguide convolver designed for matched filtering of m.s.k. modulated sequences with chirp period of 10.8 ns and with a processing gain of ∼ 30 dB is reported. The device efficiency is −63.5 dBm.
Stability of linear predictive descriptions of curves used in handwriting
- Author(s): Y.K. Ha and I.H. Witten
- Source: Electronics Letters, Volume 16, Issue 24, p. 909 –911
- DOI: 10.1049/el:19800648
- Type: Article
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–911
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The technique of signal analysis by adaptive predictive filtering has previously been extended to the case of multidimensional signals, and it has been conjectured that this might be used to analyse handwriting as a cycloidal curve which is modulated to form the letter shapes. Although a second-order two-dimensional filter can model cycloids, the analysis procedure becomes unstable, and it is shown how differencing the input and applying a first-order filter rectifies this problem.
Precisely moulded plastic splices for optical fibres
- Author(s): T. Kurokawa ; T. Yoshizawa ; Y. Katayama
- Source: Electronics Letters, Volume 16, Issue 24, p. 911 –912
- DOI: 10.1049/el:19800649
- Type: Article
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–912
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Optical fibre splices having highly precise V-grooves were moulded by electroformed cavities on etched silicon chips. Splices were produced by transfer moulding, using improved phenolic resin. They showed a quite low average splicing loss of 0.05 dB and sufficient stability to withstand the ambient temperature variation.
Simple optical wavelength meter in 700–1200 nm wavelength region
- Author(s): K. Sano ; K. Okada ; K. Hashimoto
- Source: Electronics Letters, Volume 16, Issue 24, p. 912 –913
- DOI: 10.1049/el:19800650
- Type: Article
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A new type of portable optical wavelength meter using a quartz rotator has been developed, designed for fibre optic transmission systems. The peak wavelengths of both lasers and l.e.d.s in the 700–1200 nm wavelength region can be measured. The measurement error was within ±1 nm at wavelengths around 850 nm.
Approximate solution for propagation modes on lossy multiconductor transmission lines in inhomogeneous media
- Author(s): S.S. Bedair and M.I. Sobhy
- Source: Electronics Letters, Volume 16, Issue 24, p. 914 –915
- DOI: 10.1049/el:19800651
- Type: Article
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The letter gives an approximate solution for wave propagation on a system of lossy multiconductor transmission lines with small losses. The solution leads to a general expression for the attenuation factor matrix. The expression gives a correct result for the cases of two and three conductors and can be used for any number of conductors.
Compact microstrip bandpass filter using both λ/2 and λ/4 resonators
- Author(s): M.A. Flemming
- Source: Electronics Letters, Volume 16, Issue 24, p. 915 –916
- DOI: 10.1049/el:19800652
- Type: Article
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A design procedure for a composite filter having interdigital input and output sections, separated by a λ/2 resonator, is outlined. Results from a prototype filter show improved characteristics by comparison with purely interdigital or parallel coupled filters. The passband is in closer agreement with theoretical predictions than is usual for microstrip interdigital filters.
Index profile determination in transition region of optical fibre preform
- Author(s): D. Peri and P.L. Chu
- Source: Electronics Letters, Volume 16, Issue 24, p. 916 –918
- DOI: 10.1049/el:19800653
- Type: Article
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It is shown that the refractive-index profile in the transition region of an optical fibre preform can be obtained by a combination of a measurement of the deflection function and a ray-tracing procedure.
Synthesis of planar arrays based on convolution technique
- Author(s): S.R. Laxpati
- Source: Electronics Letters, Volume 16, Issue 24, p. 918 –919
- DOI: 10.1049/el:19800654
- Type: Article
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A noniterative synthesis technique for planar arrays with arbitrary triangular lattice is described. The method, using a convolution process, synthesises the pattern nulls which may be completely arbitrary. An example of a 36-element diamond array synthesis is presented.
Effect of laser noise on analogue fibre optic systems
- Author(s): H.B. Kim ; R. Maciejko ; J. Conradi
- Source: Electronics Letters, Volume 16, Issue 24, p. 919 –920
- DOI: 10.1049/el:19800655
- Type: Article
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A simple theory taking into account both source noise and receiver noise contribution to the s.n.r. performance of analogue fibre optic systems is derived and experimentally verified. Experiments indicate that high quality a.m.-v.s.b. video transmission (s.n.r. > 60 dB) is not feasible with state-of-the-art gain-guided laser diodes.
Polarisation-maintaining single-mode fibre cable design
- Author(s): L. Jeunhomme and M. Monerie
- Source: Electronics Letters, Volume 16, Issue 24, p. 921 –922
- DOI: 10.1049/el:19800656
- Type: Article
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Guidelines for the design of a circular-polarisation-maintaining single-mode fibre cable are given. The use of circular polarisation allows use of low birefringence fibres and there is no need for orienting the fibres at splices. Quarter-wave plates at input and output of the fibres achieve the desired linear-circular polarisation conversion, and vice versa.
Channelled substrate buried heterostructure InGaAsP/InP laser emitting at 1.55 μm
- Author(s): S. Takahashi ; H. Saito ; G. Iwane
- Source: Electronics Letters, Volume 16, Issue 24, p. 922 –923
- DOI: 10.1049/el:19800657
- Type: Article
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An InGaAsP/InP channelled substrate buried heterostructure (c.s.b.) laser emitting at 1.55 μm is fabricated by channel etching and single-stage l.p.e. growth without a low temperature growth technique or antimeltback layer. The c.s.b. laser shows low threshold current at room temperature c.w. operation and stable single transverse mode operation.
I.C.-compatible completely planar GaAs m.e.s.f.e.t.s. by selective diffusion
- Author(s): N. Arnold ; H. Daembkes ; K. Heime
- Source: Electronics Letters, Volume 16, Issue 24, p. 923 –924
- DOI: 10.1049/el:19800658
- Type: Article
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Completely planar GaAs m.e.s.f.e.t.s were produced by selective open tube diffusion from tin-doped spin-on SiO2 films. After the diffusion process no change in the surface morphology was observed in the doped regions. The evaluation of saturation currents of the m.e.s.f.e.t.s show very good homogeneity. Isolation between doped areas was excellent. Sample preparation and device results are presented; possible applications are outlined.
Material dispersion zero in infra-red waveguides
- Author(s): K. Nassau
- Source: Electronics Letters, Volume 16, Issue 24, p. 924 –925
- DOI: 10.1049/el:19800659
- Type: Article
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The operation of very low loss, long optical fibres implies use of a wavelength near the material dispersion zero where d2n/dλ2 = 0. Using a technique developed by Wemple, this wavelength is estimated for a large group of oxides and halides. These data can be used to locate potential infra-red waveguide materials.
Equivalent circuit of multiplying d.a.c. using R-2R ladder network
- Author(s): J. Zurada and K. Goodman
- Source: Electronics Letters, Volume 16, Issue 24, p. 925 –927
- DOI: 10.1049/el:19800660
- Type: Article
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An equivalent circuit of a multiplying digital-analogue convertor using a switched R-2R ladder is derived. This circuit consists of dependent sources, output resistance and capacitance, all digitally controlled. For a controlled voltage attenuator the multiplying d.a.c. model has been used to ensure the correct compensation of the practical multiplying d.a.c./opamp system.
Current mirror saturation sensing technique
- Author(s): B.L. Hart
- Source: Electronics Letters, Volume 16, Issue 24, p. 927 –928
- DOI: 10.1049/el:19800661
- Type: Article
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A technique for sensing the conduction state of the output transistor of a current mirror is shown to be more discriminating than a scheme previously described. The proposed circuit is applicable to the design of monolithic timers.
Depth profiling of integrated circuits with thermal wave electron microscopy
- Author(s): A. Rosencwaig
- Source: Electronics Letters, Volume 16, Issue 24, p. 928 –930
- DOI: 10.1049/el:19800662
- Type: Article
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Nondestructive depth profiling of integrated circuits is performed with thermal wave electron microscopy at 640 kHz modulation frequency.
Implementation of Mitre public key cryptographic system
- Author(s): J.E. Hershey
- Source: Electronics Letters, Volume 16, Issue 24, p. 930 –931
- DOI: 10.1049/el:19800663
- Type: Article
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The letter presents an observation of theoretical interest regarding exponentiation in a finite field. The result can be applied towards reducing the time required for the first of two exponentiations specified by the Mitre public key cryptographic system.
Photoacoustic effect in laser annealing
- Author(s): K. Hoh
- Source: Electronics Letters, Volume 16, Issue 24, p. 931 –933
- DOI: 10.1049/el:19800664
- Type: Article
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The acoustic wave generated in silicon crystal during laser annealing has been observed. The acoustic signal increases superlinearly with incident laser energy beyond the melting threshold. This can be used for monitoring the state of melting during the annealing.
Computation of multiweight
- Author(s): K. Maitree and S. Kondo
- Source: Electronics Letters, Volume 16, Issue 24, p. 933 –934
- DOI: 10.1049/el:19800665
- Type: Article
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In learning machines the key problem is to determine weight vectors satisfying linear inequalities. In two-category classification only one weight is needed, but in multicategory classification the weight vectors which have to be found are as many as the number of pattern classes. The letter shows that, for linear machines, it is necessary to find only one weight vector, which the authors call the multiweight, by applying the steepest descent method in a learning algorithm.
Edge diffraction by right-angled dielectric wedge
- Author(s): Chang-Sung Joo ; Jung-Woong Ra ; Sang-Yung Shin
- Source: Electronics Letters, Volume 16, Issue 24, p. 934 –935
- DOI: 10.1049/el:19800666
- Type: Article
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Rigorous asymptotic diffracted fields from a right-angled dielectric wedge are obtained for plane wave incidence. A correction field to the physical optics approximation is derived from a dual series equation amenable to simple numerical calculation. The edge-diffracted cylindrical wave pattern is calculated and shown.
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