Online ISSN
1350-911X
Print ISSN
0013-5194
Electronics Letters
Volume 17, Issue 19, 17 September 1981
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Volume 17, Issue 19
17 September 1981
Noise characteristics in line-narrowed semiconductor lasers with optical feedback
- Author(s): L. Goldberg ; A. Dandridge ; R.O. Miles ; T.G. Giallorenzi ; J.F. Weller
- Source: Electronics Letters, Volume 17, Issue 19, p. 677 –678
- DOI: 10.1049/el:19810473
- Type: Article
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Effects of optical-feedback-induced line-narrowing on low-frequency amplitude and phase noise of semiconductor lasers are reported. Free-running laser noise is compared with that of lasers operating with external mirror feedback. While less than 1 dB difference in the amplitude noise with and without feedback is observed, line-narrowed lasers exhibit 15–20 dB reduction in low-frequency wavelength instability, or phase noise.
Characteristics of phase-matched sum-frequency light in optical fibres
- Author(s): Y. Ohmori and Y. Sasaki
- Source: Electronics Letters, Volume 17, Issue 19, p. 678 –680
- DOI: 10.1049/el:19810474
- Type: Article
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Characteristics of phase-matched sum-frequency light in optical fibres is investigated to determine the input power dependence and fibre length dependence. The output power at 0.54 μm increases in proportion to the square root of the input power, increasing almost exponentially with increases in the fibre length from 4 m to 17 m and becoming nearly constant above 17 m.
Cochannel interference immunity of high capacity QAM
- Author(s): V.K. Prabhu
- Source: Electronics Letters, Volume 17, Issue 19, p. 680 –681
- DOI: 10.1049/el:19810475
- Type: Article
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To achieve very high bandwidth efficiencies in digital-radio large-level quadrature amplitude modulation (QAM) is an attractive modulation scheme. In the letter, the cochannel interference immunity of such high capacity QAM is determined.
Simple design of x-junction microstrip circulators
- Author(s): A.-M. Khilla
- Source: Electronics Letters, Volume 17, Issue 19, p. 681 –682
- DOI: 10.1049/el:19810476
- Type: Article
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The modes used in the construction of x-junction microstrip circulators are a pair of radial TM±3,1,0 degenerate modes and a radial TM0,1,0 mode. A direct magnetic field is applied to split the degeneracy between the former modes. A micro-strip ring resonator is chosen to immediately satisfy the first two of the three circulation conditions for this type of junction. Experimental results support theoretical designs.
Effect of threshold offsets in zero-crossing speech detector
- Author(s): M.R.L. Hodges
- Source: Electronics Letters, Volume 17, Issue 19, p. 682 –684
- DOI: 10.1049/el:19810477
- Type: Article
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Detectors based on the zero-crossing distribution of a signal can be used to detect speech in a background of noise. The letter shows how, with a low noise level, this type of detector will not operate successfully, and proposes a novel solution to the problem.
Original improvements of TLM method
- Author(s): M. Leroy
- Source: Electronics Letters, Volume 17, Issue 19, p. 684 –685
- DOI: 10.1049/el:19810478
- Type: Article
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The use of the three-dimensional-TLM method is limited, first, by an excessive computation time and, secondly, by the variability of the results when the position of the point of observation varies. An original approach is described which improves the first point and avoids the second one. The resonant frequencies of the studied cavity are computed by applying Prony's method to time variations of the electric energy located inside the cavity. Numerical results are given in the case of the ridged waveguide cavity.
Deep hole traps in VPE p-type InP
- Author(s): M. Inuishi and B.W. Wessels
- Source: Electronics Letters, Volume 17, Issue 19, p. 685 –686
- DOI: 10.1049/el:19810479
- Type: Article
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Deep hole traps were investigated in vapour phase epitaxial p-type InP by transient capacitance spectroscopy. A total of five hole traps were observed with activation energies of 0.09, 0.22, 0.29, 0.41 and 0.50 eV in Al-InP Schottky barriers and p-n+ junctions. Trap concentrations ranged from 1013 to 1014 cm−3.
Electron concentration and alloy composition dependence of Hall factor in GaxIn1−xAsyP1−y
- Author(s): Y. Takeda ; M.A. Littlejohn ; J.A. Hutchby ; R.J. Trew
- Source: Electronics Letters, Volume 17, Issue 19, p. 686 –688
- DOI: 10.1049/el:19810480
- Type: Article
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The Hall factor is calculated by the iterative method over whole composition range of GaxIn1−xAsyP1−y lattice-matched to InP. The electron concentrations used are 1×1016 cm−3 and 1×1017 cm−3, with carrier compensation ratios (ND+NA/n 1, 2, and 5, which are commonly observed in grown GaInAsP alloys. The Hall factor decreases with increasing alloy content y for relatively low electron concentrations, but this is not the case in compensated alloys because of varying predominance of scattering mechanisms with composition and ionised impurity concentration.
Symmetrical Mott barrier as a fast photodetector
- Author(s): C.J. Wei ; H.-J. Klein ; H. Beneking
- Source: Electronics Letters, Volume 17, Issue 19, p. 688 –690
- DOI: 10.1049/el:19810481
- Type: Article
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A novel surface-oriented GaAs punch-through photodetector possessing a fast photoresponse and a moderate internal gain is described. The device has a simple planar MnM structure consisting of two Schottky contacts which thereby facilitate the fabrication. The detector exhibits an internal rise time as fast as 20 ps with a full width at half maximum (FWHM) of 35 ps. The internal gain of the detector was estimated to be 3. The noise equivalent power was measured to be 4×10−11 W/√Hz. The detector represents one of the fastest GaAs photodetectors reported to date.
Dielectric measurements in the X-band of mamma tissue from cattle
- Author(s): Y. Yamamoto and K. Fujisawa
- Source: Electronics Letters, Volume 17, Issue 19, p. 690 –691
- DOI: 10.1049/el:19810482
- Type: Article
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Dielectric measurements of mamma tissue from cattle were carried out by inserting it in the X-band waveguide. Comparing the experimentally obtained values of the attenuation constants in mamma, muscle and fat, the muscle content in mamma was determined.
Phase-lock-loop operating ranges measurement
- Author(s): R.C. Den dulk and M.P.I. Huisman
- Source: Electronics Letters, Volume 17, Issue 19, p. 691 –693
- DOI: 10.1049/el:19810483
- Type: Article
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A measurement method is presented that quickly displays the operating ranges of phase-lock loops (PLLs) and acquisition aids under various input conditions such as noise and interference. The PLL measurement set-up is based on the use of normally available spectrum analyser/tracking generator equipment rather than on the common display of the control voltage of the oscillator. It is shown that in case of a narrow-band PLL the spectrum-analyser display can be more easily interpreted than the control-voltage display.
Novel CMOS Schmitt trigger
- Author(s): K. Nagaraj and M. Satyam
- Source: Electronics Letters, Volume 17, Issue 19, p. 693 –694
- DOI: 10.1049/el:19810484
- Type: Article
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A novel CMOS Schmitt trigger using only four MOS transistors is discussed. This circuit, which works on the principle of load-coupled regenerative feedback, can be implemented using conventional CMOS technology with only one extra fabrication step. It can be implemented even more easily in CMOS/SOS (silicon-on-sapphire) integrated circuits. The hysteresis of this Schmitt trigger can be controlled by a proper choice of the transistor geometries.
Fusion mass-splicing for optical fibres by discharge heating
- Author(s): M. Tachikura
- Source: Electronics Letters, Volume 17, Issue 19, p. 694 –695
- DOI: 10.1049/el:19810485
- Type: Article
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A mass-splicing technique for tape-unit silica fibres based on discharge fusion is demonstrated. Five pairs of fibres are simultaneously fused and spliced together by the heat from the electric discharge between two pairs of electrodes. The average splice loss for 50 μm-core graded-index fibres is 0.22 dB.
Schmitt trigger circuit with picosecond risetimes
- Author(s): L. Bickers
- Source: Electronics Letters, Volume 17, Issue 19, p. 695 –697
- DOI: 10.1049/el:19810486
- Type: Article
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A Schmitt trigger circuit is described which overcomes some of the stability problems associated with the wide hysteresis loop of more conventional arrangements. A low level of hysteresis is achieved, thereby reducing the threshold voltage while also affording increased stability during switching. Operational risetimes of 200 ps are demonstrated.
Wide-sense nonblocking network made of square switches
- Author(s): V.E. Beneš and R.P. Kurshan
- Source: Electronics Letters, Volume 17, Issue 19, page: 697 –697
- DOI: 10.1049/el:19810487
- Type: Article
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An example of theoretical interest is given, of a connecting network with no expansion which is nonblocking in the wide sense, i.e. if and only if the right routing algorithm is used.
Improved mobility in OM-VPE-grown Ga1−xInxAs
- Author(s): W.T. Dietze ; M.J. Ludowise ; C.B. Cooper
- Source: Electronics Letters, Volume 17, Issue 19, p. 698 –699
- DOI: 10.1049/el:19810488
- Type: Article
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The use of a tirmethylindium-trimethylarsenic adduct, which is synthesised in the gas phase, as the In source, and AsH3 as the primary As source is reported for the growth of high-quality Ga1−xInxAs (x<0.20). The improved epitaxial layers have higher mobilities and lower background doping than those grown with trimethylarsenic as the sole As source. The effects of elevated growth temperatures are also reported.
Radar echoes near a dielectric resonance
- Author(s): J. van Bladel
- Source: Electronics Letters, Volume 17, Issue 19, p. 699 –700
- DOI: 10.1049/el:19810489
- Type: Article
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The power of the radar echo from a dielectric body of high εr is evaluated in the vicinity of the target's lowest resonant frequency, at which the body radiates like a magnetic dipole. The formula shows the dependence of the power on the polarisation of the incident wave and on the characteristics of the body, e.g. εr and the orientation.
Fast calculation of impulse responses without multiplications
- Author(s): J. Justesen
- Source: Electronics Letters, Volume 17, Issue 19, p. 700 –701
- DOI: 10.1049/el:19810490
- Type: Article
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The impulse response of a linear system may be calculated from the response to a pseudorandom sequence. If the calculation is based on the fast Hadamard transform, only additions and subtractions are required.
E-type circulator for fin lines
- Author(s): M. Braas and C. Schieblich
- Source: Electronics Letters, Volume 17, Issue 19, p. 701 –702
- DOI: 10.1049/el:19810491
- Type: Article
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A simple fin-line circulator is described showing an isolation in excess of 20 dB over 10% bandwidth in X-band. The insertion loss is about 0.5 dB.
PIN diodes in meander-line filters for multiplexing applications
- Author(s): G.N.O. Ugwuagu and H.V. Shurmer
- Source: Electronics Letters, Volume 17, Issue 19, p. 702 –703
- DOI: 10.1049/el:19810492
- Type: Article
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A new application of PIN diodes is described in terms of a meander-line switchable filter. With the diodes forward-biased, bandpass properties result, but under reverse bias the passband is converted into a stopband. These filters are intended for use in multiplexing systems.
In0.53Ga0.47As contact layer for 1.3 μm light-emitting diodes
- Author(s): H. Temkin ; A.K. Chin ; M.A. Digiuseppe
- Source: Electronics Letters, Volume 17, Issue 19, p. 703 –705
- DOI: 10.1049/el:19810493
- Type: Article
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Measurements of the specific contact resistance on epitaxially grown layers of p-In1−xGaxAsyP1−y as a function of composition demonstrate the resistance minimum of 7×10−6 Ωcm2 for In0.53Ga0.47As. Growth procedures for the preparation of InGaAsP/InP double-heterostructure LED wafers incorporating such a ternary InGaAs contact layer are described. This contacting technique allows fabrication of high-performance devices with reproducibly low series resistance.
Pseudoactive bridge for separation of R and C in a practical capacitive/conductive transducer
- Author(s): K. Padmanabhan and G.S. Somayajulu Sarma
- Source: Electronics Letters, Volume 17, Issue 19, p. 705 –706
- DOI: 10.1049/el:19810494
- Type: Article
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An effective and unique method of measuring independently the variations of resistive and capacitive constituents of a practical capacitive transducer using an improved pseudo-active bridge is described. The impedance change in some types of transducers may be due to changes in resistance and/or capacitance either way. Separation of changes in resistance and capacitance results in a better understanding of the transduced variable. The active bridge which separates the changes is suitable for online determination of the two changes.
Method of fabricating high-Q silicon varactor diodes
- Author(s): A. Rosen ; C.P. Wu ; M. Caulton ; A. Gombar ; P. Stabile
- Source: Electronics Letters, Volume 17, Issue 19, p. 707 –708
- DOI: 10.1049/el:19810495
- Type: Article
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A new processing technique has been developed for the fabrication of high-Q and high-voltage varactor diodes. The process utilises ion implantation and laser annealing for heavily-doped p++ and n++ layers and epitaxial growth for low impurity concentrations. The technique provides good yield and repeatability, and it has allowed fabrication of varactor diodes which have breakdown voltages of 120 V and a Q as high as 600 at −8 V bias and 50 MHz frequency.
InP Gunn oscillators in V-band
- Author(s): J.J. Sowers ; B.A. Janis ; J.D. Crowley ; F.B. Fank
- Source: Electronics Letters, Volume 17, Issue 19, p. 708 –709
- DOI: 10.1049/el:19810496
- Type: Article
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Output powers of 200 mW and efficiencies up to 6.5% have been achieved with CW InP Gunn oscillators in V-band (50–75 GHz). Fixed frequency as well as frequency tunable oscillators have been developed. Tuning bandwidths of 19% and 6.1% have been achieved with mechanical and varactor tuning, respectively.
Method for direct multiway branching in microprogram control
- Author(s): C.A. Papachristou
- Source: Electronics Letters, Volume 17, Issue 19, p. 709 –710
- DOI: 10.1049/el:19810497
- Type: Article
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A new technique is proposed for simultaneously executing multiway branching with PLAs. The basic structure consists of three units: the microcode ROM, the microsequencer PLA and a register counter. The main idea is to store only branching information in PLA, exploiting the associative addressing properties of the latter. Benefits in speed and memory space are obtained.
Comment: Algorithm for sampled data signal flow graphs
- Author(s): S.V. Salehi
- Source: Electronics Letters, Volume 17, Issue 19, p. 710 –711
- DOI: 10.1049/el:19810498
- Type: Article
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Spectral calculation of partial response multi-h phase codes
- Author(s): L.F. Lind and A.A. de Albuquerque
- Source: Electronics Letters, Volume 17, Issue 19, p. 711 –713
- DOI: 10.1049/el:19810499
- Type: Article
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A computationally efficient method is given to find power spectra for this bandwidth efficient modulation process. A numerical example of this method is included.
Dielectric properties of blood plasma
- Author(s): S.C. Kashyap
- Source: Electronics Letters, Volume 17, Issue 19, p. 713 –714
- DOI: 10.1049/el:19810500
- Type: Article
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The letter is concerned with the determination of complex permittivity of blood plasma.
Low-threshold stripe geometry lasers by metalorganic chemical vapour deposition (MO-CVD)
- Author(s): R.D. Burnham ; D.R. Scifres ; W. Streifer
- Source: Electronics Letters, Volume 17, Issue 19, p. 714 –715
- DOI: 10.1049/el:19810501
- Type: Article
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We report low-threshold MO-CVD-grown GaAlAs DH (8260 Å) lasers with shallow proton implantation delineated stripe widths of 4, 6 and 8 mm. At room temperature, a 125 μm device with a 6 μm stripe exhibited a 31 mA threshold and operated kink-free up to 15 mW/facet with a differential efficiency of 76%.
Modulation characteristic and intensity noise of CW superluminescent diodes
- Author(s): R. Schimpe and J. Boeck
- Source: Electronics Letters, Volume 17, Issue 19, p. 715 –717
- DOI: 10.1049/el:19810502
- Type: Article
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Index-guided superluminescent diodes for CW operation have been fabricated. Threshold current densities below 3 kA/cm2 have been achieved. The low-frequency intensity noise and modulation sensitivity of this device have been investigated.
Stability test for multidimensional digital filters
- Author(s): J.L. Brown ; J. Delansky ; E. Plotkin ; L.M. Roytman ; M.N.S. Swamy
- Source: Electronics Letters, Volume 17, Issue 19, p. 717 –718
- DOI: 10.1049/el:19810503
- Type: Article
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An implementation procedure for a new stability test for n-dimensional digital filters is developed. The procedure is based on the computation of a sequence of polynomials (resultants) in a decreasing number of complex variables and use of the resultant method.
Reflection analysis of flanged circular waveguide radiating through small aperture into absorbing medium
- Author(s): C. Fray ; K. Chandrasekhar ; A. Papiernik
- Source: Electronics Letters, Volume 17, Issue 19, p. 718 –720
- DOI: 10.1049/el:19810504
- Type: Article
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A flanged circular waveguide in dominant-mode operation, radiating through a small circular aperture into an absorbing medium, has been studied from the point of view of reflections caused in the guide. The effect of varying the aperture size in modifying the reflections in amplitude and phase has been determined; the proper choice needed to realise matched conditions have been determined for a few selected media.
Spectral distribution of a sampled 1st-order lowpass filtered white noise
- Author(s): C.A. Gobet
- Source: Electronics Letters, Volume 17, Issue 19, p. 720 –721
- DOI: 10.1049/el:19810505
- Type: Article
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In the letter, the spectrum of a sampled 1st-order lowpass filtered white noise is calculated, and theoretical results are compared with measurements made on a laboratory model. In this context, the effect of undersampling appears clearly for noise bandwidths exceeding the sampling rate. This analysis contributes to the study of noise in switched capacitor networks.
Comment: Voltage transfer function shift theorem
- Author(s): R. Palomera-Garcia
- Source: Electronics Letters, Volume 17, Issue 19, p. 721 –722
- DOI: 10.1049/el:19810506
- Type: Article
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Erratum: Low-distortion high-output class B current convertor using error feedforward
- Author(s): B. Wilson
- Source: Electronics Letters, Volume 17, Issue 19, page: 722 –722
- DOI: 10.1049/el:19810507
- Type: Article
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Erratum: Time-dependent thermal effects in current-modulated semiconductor lasers
- Author(s): L. Goldberg ; H.F. Taylor ; J.F. Weller
- Source: Electronics Letters, Volume 17, Issue 19, page: 722 –722
- DOI: 10.1049/el:19810508
- Type: Article
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