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image of Volume 23, Issue 17
Online ISSN 1350-911X Print ISSN 0013-5194

Electronics Letters

Volume 23, Issue 17, 13 August 1987

Volumes & issues:

Volume 23, Issue 17

13 August 1987

Efficient probabilistic algorithm for solving quadratic equations over finite fields
Resonant-tunnelling hot-electron transistor (RHET) using a GaInAs/(AlGa)InAs heterostructure
  • Author(s): K. Imamura ; S. Muto ; H. Ohnishi ; T. Fujii ; N. Yokoyama
  • Source: Electronics Letters, Volume 23, Issue 17, p. 870 –871
  • DOI:  10.1049/el:19870616
  • Type: Article
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  • p. 870 –871 (2)
    A common-emitter current gain of 10 has been measured at 77 K for a 100 nm-base resonant-tunnelling hot-electron transistor (RHET) using a GaInAs/(AlGa)InAs heterostructure. The current gain for 25 nm-base RHETs has reached 25, which is the highest value yet reported for hot-electron transistors, and the collector current peak-to-valley ratio has reached 15.0 for the same device.
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Impact of laser intensity noise on ASK two-port optical homodyne receivers
  • Author(s): L.G. Kazovsky ; A.F. Elrefaie ; P. Meissnert ; R. Welter ; P. Crespo ; J. Gimlett ; R.W. Smith
  • Source: Electronics Letters, Volume 23, Issue 17, p. 871 –873
  • DOI:  10.1049/el:19870617
  • Type: Article
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  • p. 871 –873 (3)
    The letter describes initial experimental results obtained with a multiport optical homodyne receiver employing a DFB laser. The receiver performance is found to be limited by the intensity noise of the local oscillator rather than by the phase noise, even when the product of the IF linewidth and the bit duration is as large as 0.56. A relative intensity noise level of at least — 140dB/Hz will be required for a satisfactory receiver performance with — 15dBm local oscillator power.
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New structure of three-terminal GaAs p+−n−−δ(p+)−n−−n+ switching device prepared by molecular beam epitaxy
  • Author(s): Y.H. Wang ; K.F. Yarn ; C.Y. Chan ; M.S. Jame
  • Source: Electronics Letters, Volume 23, Issue 17, p. 873 –874
  • DOI:  10.1049/el:19870618
  • Type: Article
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  • p. 873 –874 (2)
    The concept to modulate the internal barrier of a regenerative switching device is proposed. A new structure of three-terminal GaAs p+−n−−δ(p+)−n−−n+ switching device prepared by molecular beam epitaxy is successfully developed. The third terminal was directly contacted to the δ(p+) barrier using the V-groove etching technique, in which the δ(p+) barrier height can be directly modulated by the external voltage. It is a voltage-controlled device.
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Densely spaced WDM coherent optical star network
  • Author(s): B. Glance ; K. Pollock ; C.A. Burrus ; B.L. Kasper ; G. Eisenstein ; L.W. Stulz
  • Source: Electronics Letters, Volume 23, Issue 17, p. 875 –876
  • DOI:  10.1049/el:19870619
  • Type: Article
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  • p. 875 –876 (2)
    An optical WDM star network consisting of three lasers transmitting at about 234 000 GHz, spaced by 300 MHz, has been used to demonstrate dense packing of WDM signals. The three optical signals, FSK-modulated at 45Mbit/s, are multiplexed by a 4 × 4 star coupler and demultiplexed by a balanced heterodyned receiver. Receiver sensitivity is -61dBm for a BER of 10−9, or 113 photons/bit, which is 4.5dB from the shot noise limit and represents the best sensitivity yet reported for FSK modulation. The results indicate that 100 000 users in a 10km radius could be interconnected with such a system.
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Feed radiation effects in sequentially rotated microstrip patch arrays
Linearising method for nonlinear properties in a liquid-crystal lens
Nonuniform phased arrays of diode lasers for fundamental supermode operation
  • Author(s): E. Kapon
  • Source: Electronics Letters, Volume 23, Issue 17, p. 879 –881
  • DOI:  10.1049/el:19870622
  • Type: Article
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  • p. 879 –881 (3)
    A new design of nonuniform phased arrays of diode lasers is described. In these nonuniform arrays both the channel widths and the channel spacings are properly varied across the array. This design results both in effective discrimination against the higher-order supermodes as well as in a more uniform near-field distribution. Such nonuniform arrays should therefore yield single-lobe, diffraction-limited beams up to higher output power levels.
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22 GHz 1/4 frequency divider using AlGaAs/GaAs HBTs
Transmission-line model for two-port rectangular microstrip patches with ports at the nonradiating edges
Diode-laser-pumped Nd3+-doped fibre laser operating at 938 nm
Impact of 1/f-type FM noise on coherent optical communications
Single-mode guided-wave optical gate matrix switch using Mach-Zehnder interferometer gates
Offset dual-reflector multiple-beam antennas using circularly symmetric main reflectors
  • Author(s): S.G. Hay
  • Source: Electronics Letters, Volume 23, Issue 17, p. 888 –890
  • DOI:  10.1049/el:19870628
  • Type: Article
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  • p. 888 –890 (3)
    An investigation into the multiple-beam capability of offset antennas using circularly symmetric main reflectors is described. The efficiency and sidelobe performance of systems designed to produce beams up to 4.6° either side of boresight with reflector diameters ranging from 100 to 300 wavelengths are shown to make the antennas suitable for multiple-satellite-access earth stations. Comparison is made with a nonsymmetrical main-reflector antenna designed for the same requirements.
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Temperature compensation of OTA-based filters and amplifiers
Effect of photochemical etching on interface state density of Ga0.47In0.53As metal/insulator/semiconductor diodes
  • Author(s): A. Aoki ; S. Miyoshi ; J. Shirafuji
  • Source: Electronics Letters, Volume 23, Issue 17, p. 891 –892
  • DOI:  10.1049/el:19870630
  • Type: Article
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  • p. 891 –892 (2)
    A metal/insulator/semiconductor (MIS) structure of Ga0.47In0.53As has been prepared by applying an excimer laser photo-CVD process to depositing an SiNx insulating layer. It is found that interface state densities can be remarkably reduced by in situ photochemical etching with CC14 or CH3Br gases prior to SiNx deposition. A minimum value of the U-shape profile of the interface state density as low as 5 × 1011 cm-2eV-1is attained.
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Performance characteristics of high-brightness, CW, diode laser arrays
  • Author(s): D.F. Welch ; M. Devito ; M. Cardinal ; M. Abraham ; H. Kung ; G. Harnagel ; P. Cross ; D. Scifres ; W. Streifer
  • Source: Electronics Letters, Volume 23, Issue 17, p. 892 –893
  • DOI:  10.1049/el:19870631
  • Type: Article
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  • p. 892 –893 (2)
    Recently developed, high-brightness diode laser arrays have been tested at 50°C at output powers of 0.5 W CW and 1.0W CW from 100μm- and 200μm-wide active regions, respectively. The extrapolated lifetimes at room temperature exceed 40000 h. The maximum CW power output prior to catastrophic degradation of the facets is 2.0 W for the 100μm device and greater than 3 W for the 200μm-aperture device.
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Very low threshold current density of a GaInP/AlGaInP double-heterostructure laser grown by MOCVD
Analysis of a PIN photodiode with integrated waveguide
Directivity of linear microstrip arrays
GaAs lateral bipolar transistor with field-separated carriers
  • Author(s): D. Ueda ; H. Takagi ; G. Kano ; I. Teramoto
  • Source: Electronics Letters, Volume 23, Issue 17, p. 899 –900
  • DOI:  10.1049/el:19870635
  • Type: Article
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  • p. 899 –900 (2)
    A new type of GaAs lateral bipolar transistor has been developed by introducing an n-i-p-i-n structure where the electric field is applied perpendicular to the direction of carrier injection in order for the carriers to be separated. The diffusion length is increased owing to the increase of lifetime due to the spatial separation of injected carriers, resulting in the increase of current gain.
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New clustering approach to chip floorplan using functional data
  • Author(s): I. Harada  and  T. Adachi
  • Source: Electronics Letters, Volume 23, Issue 17, p. 900 –902
  • DOI:  10.1049/el:19870636
  • Type: Article
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  • p. 900 –902 (3)
    An approach to chip floorplanning utilising hierarchical and functional information derived using LSI logic design is described. The proposed approach adopts a methodological design process similar to that of expert designers. A new clustering method that can be divided into three phases, namely clustering, cluster classification and placement, is employed in this process. The prototype system is implemented based on AI techniques.
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Method for synthesis of MOSFET logic networks
  • Author(s): S.G. Smith  and  M. Keightley
  • Source: Electronics Letters, Volume 23, Issue 17, p. 902 –903
  • DOI:  10.1049/el:19870637
  • Type: Article
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  • p. 902 –903 (2)
    A method is described for synthesis of single-output MOSFET logic networks from functional specifications (including ‘don't-cares’), based on the restriction that circuit inputs connect only to MOSFET gates (and vice versa). Every distinct combination of input terminal orderings is assessed in the search for an optimal solution. As the potential search space is factorial in the input dimension, heuristics are employed to bypass the synthesis of inefficient circuits. The ability to override these heuristics and force terminal orderings allows external as well as internal issues to influence selection.
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Application of the simplex technique in motion estimation
Low backscattered TM-polarised strip gratings
  • Author(s): K.A. Jose ; C.K. Aanandan ; K.G. Nair
  • Source: Electronics Letters, Volume 23, Issue 17, p. 905 –906
  • DOI:  10.1049/el:19870639
  • Type: Article
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  • p. 905 –906 (2)
    The development of reflector-backed strip gratings exhibiting properties like the elimination of specular reflections from a conducting surface for normal and near-normal incidence is reported. This is not possibly by conventional corrugated metallic surfaces. Perfect blazing to n = −1 spectral order is also provided by the developed system. This technique offers a simple and inexpensive method for the simulation of corrugated horns.
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Evaluation of crosstalk penalty in multichannel ASK heterodyne optical communication systems
  • Author(s): G.P. Agrawal
  • Source: Electronics Letters, Volume 23, Issue 17, p. 906 –908
  • DOI:  10.1049/el:19870640
  • Type: Article
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  • p. 906 –908 (3)
    The bit error rate (BER) of a two-channel ASK heterodyne lightwave system employing envelope detection is evaluated analytically. The result is used to calculate the power penalty resulting from intrachannel crosstalk. To main a BER below 10−9, the power penalty increases from 0.2 to 1 dB when the level of crosstalk increases from −15 to −10 dB. The theory predicts a minimum channel spacing of three times the bit rate if the design criterion is to keep the crosstalk penalty below 0.1 dB. The minimum channel spacing increases to five times the bit rate for multichannel systems when crosstalk from the nearest neighbours on both sides is included.
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Birefringent-fibre polarisation splitters
Systematic design of D flip-flops using two state variables
Monolithic 2–6 GHz limiting amplifier
  • Author(s): R. Majidi-Ahy ; M. Omori ; E. Stoneham
  • Source: Electronics Letters, Volume 23, Issue 17, p. 910 –912
  • DOI:  10.1049/el:19870643
  • Type: Article
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  • p. 910 –912 (3)
    A four-stage 2–6 GHz limiting amplifier has been developed based on a single-stage GaAs MMIC amplifier chip. The limiting amplifier is optimised for sharp linear-to-saturation power characteristics with less than 4 dB difference between minimum P1 dB (1 dB gain compression point) and maximum Psat (saturated output power) over frequency and temperature (−55°C to 85°C). The small-signal gain of the limiting amplifier at room temperature is 22.5 dB with gain flatness of ±0.5 dB, with less than 1.7:1 input and output VSWR over the band.
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Microstrip log-periodic antenna array with endfire beam
  • Author(s): P.S. Hall  and  A. Sparrow
  • Source: Electronics Letters, Volume 23, Issue 17, p. 912 –913
  • DOI:  10.1049/el:19870644
  • Type: Article
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  • p. 912 –913 (2)
    Endfire action with a very wide-bandwidth, low-profile antenna array has not yet been achieved. After showing that a conventional microstrip log-periodic array cannot be successfully scanned from broadside to endfire, a new configuration involving quarter-wavelength shorted patches is described. First-order theory indicates that good endfire action should be possible, and this is confirmed by preliminary measurements on an array designed for a 25% bandwidth. Radiation pattern control is seen to be the most critical performance parameter.
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Comment: Independent tuning of quality factor and unity-gain frequency in a transconductance-capacitance integrator
InGaAs/InP SAGM avalanche photodiodes incorporating a pseudoquaternary superlattice graded heterojunction grown by atmospheric-pressure MOCVD
  • Author(s): A.J. Moseley ; J. Urquhart ; P.D. Hodson ; J.R. Riffat ; J.I. Davies
  • Source: Electronics Letters, Volume 23, Issue 17, p. 914 –916
  • DOI:  10.1049/el:19870646
  • Type: Article
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  • p. 914 –916 (3)
    We have demonstrated a high-speed GaInAs/InP SAGM avalanche photodiode grown by atmospheric-pressure MOCVD which incorporates a graded-bandgap GaInAs/InP superlattice layer to overcome hole pile-up effects inherent in the basic SAM devices. This approach offers considerable interface design flexibility without recourse to GaInAsP quaternary compositions. High-speed operation has been demonstrated without compromising the dark current or gain by the inclusion of the multiple heterojunctions of the superlattice.
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High-speed 2 × 2 electrically driven spatial light modulator made with GaAs/AlGaAs multiple quantum wells(MQWs)
Electron transport of (Al,Ga)Sb/InAs heterojunctions prepared by molecular beam epitaxy
  • Author(s): T.H. Chiu ; W.T. Tsang ; A.F.J. Levi
  • Source: Electronics Letters, Volume 23, Issue 17, p. 917 –919
  • DOI:  10.1049/el:19870648
  • Type: Article
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  • p. 917 –919 (3)
    Molecular beam epitaxial growth of (Al,Ga)Sb/InAs hetero-structures is described. Electron transport studies indicate that these heterojunctions are of high quality. Shubnikov-de Haas measurement of the AlSb/InAs/GaSb quantum well shows a two-dimensional electron gas of concentration 2×1012cm2 and a low-temperature mobility approaching 105cm2/Vs. Low-temperature capacitance/voltage measurement indicates that the thin AlSb barrier is a classical Mott-type barrier.
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