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Online ISSN 1350-911X Print ISSN 0013-5194

Electronics Letters

Volume 25, Issue 13, 22 June 1989

Volumes & issues:

Volume 25, Issue 13

22 June 1989

Fast algorithm for calculating alphabet-constrained rate-distortion functions
30 Hz-linewidth, diode laser-pumped, Nd:GGG nonplanar ring oscillators by active frequency stabilisation
  • Author(s): T. Day ; A.C. Nilsson ; M.M. Fejer ; A.D. Farinas ; E.K. Gustafson ; C.D. Nabors ; R.L. Byer
  • Source: Electronics Letters, Volume 25, Issue 13, p. 810 –812
  • DOI:  10.1049/el:19890545
  • Type: Article
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  • p. 810 –812 (3)
    We report a heterodyne linewidth of less than 30 Hz for the beatnote between the outputs of two 282 THz (1.062µm) Nd:GGG nonplanar ring oscillators (NPROs). The lasers were independently locked to adjacent axial modes of a highfinesse interferometer. The remnant frequency noise appears to be dominated by free spectral range fluctuations in the reference interferometer rather than by residual laser noise.
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Improved radiation hardness of MOS devices with ultrathin nitrided oxide gate dielectrics prepared by rapid thermal processing
  • Author(s): G.Q. Lo ; D.K. Shih ; W.C. Ting ; D.L. Kwong
  • Source: Electronics Letters, Volume 25, Issue 13, p. 812 –813
  • DOI:  10.1049/el:19890546
  • Type: Article
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  • p. 812 –813 (2)
    The radiation hardness of MOS devices with ultrathin nitrided oxides (~100A) prepared by rapid thermal nitridation (RTN) of thin oxides has been studied. The radiation was performed by exposing devices under X-rays of 50 keV to a dose of 0.5 Mrad(Si). Compared with conventional thermal oxides, the RTN oxide devices exhibit a much smaller increase in both the fixed charge Nf and the interface state Dit densities. In addition, it is found that higher RTN temperature and/or longer durations produce smaller ΔNf and ΔDit.
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Stationary charge domain in GaAs MESFETs: dimensional and electrical characterisation
Frequency stabilisation of λ/4-shifted DFB laser to stabilised optical resonator
Digital realisation of forward and inverse models of electromagnetic scattering
Demonstration of novel optical multichannel grating demultiplexer receiver (MGD) for HDWDM systems
  • Author(s): Y. Kanabar  and  N. Baker
  • Source: Electronics Letters, Volume 25, Issue 13, p. 817 –819
  • DOI:  10.1049/el:19890550
  • Type: Article
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  • p. 817 –819 (3)
    A novel implementation of a multichannel grating demultiplexer receiver suitable for HDWDM applications is described. The prototype receiver, capable of 10-channel operation spaced at 4nm, uses a 16-element GalnAs/InP monolithic linear photodetector array and silicon preamplifier ICs. The sensitivity at the input to the demultiplexer is – 3 1 dBm at 200Mbit/s. Optical and electrical crosstalk measurements in the receiver are presented, and limited tests have shown that there is a negligible crosstalk penalty.
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High-power grating-coupled surface emitters
Role of velocity saturation in lifting pinchoff condition in long-channel MOSFET
  • Author(s): V.K. Arora  and  M.B. Das
  • Source: Electronics Letters, Volume 25, Issue 13, p. 820 –821
  • DOI:  10.1049/el:19890552
  • Type: Article
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  • p. 820 –821 (2)
    The role of velocity saturation due to high–field mobility degradation in lifting the pinchoff condition in a longchannel MOSFET is described. The electric field on the drain end at the onset of current saturation is always extremely high leading to the velocity saturation of the carriers. This velocity saturation leads to the saturation value nsD =nsoV'g/2Vc = IDsat/qvth W on the drain end, in contrast with the well-known pinchoff behaviour, where the carrier density is shown to vanish at the saturation point. The carrier distribution, as well as the velocity distribution as a function of the channel distance along the length of the channel, is presented.
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Improved dynamics and linewidth enhancement factor in strained-layer lasers
Effects of deep-level states on current/voltage characteristics of heteroepitaxial GaAs
  • Author(s): K. Das ; T.P. Humphreys ; N.R. Parikh ; J.B. Posthill
  • Source: Electronics Letters, Volume 25, Issue 13, p. 823 –824
  • DOI:  10.1049/el:19890554
  • Type: Article
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  • p. 823 –824 (2)
    The first results pertaining to current/voltage measurements of Au contacts fabricated on molecular beam epitaxial GaAs films grown on (1012) sapphire and silicon-on-sapphire (SOS) substrates are presented. A simple analysis of the corresponding l/V characteristics indicates that the dominant transport mechanism in these films is space-charge-limited current conduction in the presence of deep-level states. The nature of these deep-level states appears to be sensitive to the type of crystallographic defects present in the GaAs heteroepitaxial layers.
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Enhanced time duration constraints in hidden Markov modelling for phoneme recognition
  • Author(s): Y. Ariki  and  M.A. Jack
  • Source: Electronics Letters, Volume 25, Issue 13, p. 824 –825
  • DOI:  10.1049/el:19890555
  • Type: Article
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  • p. 824 –825 (2)
    The use of enhanced time duration constraints for subword (phoneme) recognition in continuous speech is reported. Here the time duration constraints are modelled by a Gaussian probability distribution in the conventional Baum-Welch learning algorithm and are statistically enhanced to obtain the most probable path in the Viterbi decoding process. Experimental results to validate this approach are included.
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Modified Lu-Lee cryptosystems
Physical origin of negative differential resistance in SOI transistors
  • Author(s): L.J. McDaid ; S. Hall ; P.H. Mellor ; W. Eccleston ; J.C. Alderman
  • Source: Electronics Letters, Volume 25, Issue 13, p. 827 –828
  • DOI:  10.1049/el:19890557
  • Type: Article
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  • p. 827 –828 (2)
    From a two-dimensional solution of Laplace's equation it is shown that a significant increase in temperature occurs in the channel of SOI transistors due to the relatively poor thermal conductivity of the buried insulator. Based on this simulation an equation is derived which predicts that at small channel lengths the pinchoft point is shifted, an effect which is consistent with experimental observations. In addition, the positive 'kink' is reduced with increasing gate voltage and this effect, together with the negative differential resistance, can be explained by a temperature increase in the channel.
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100 GHz active electronic probe for on-wafer S-parameter measurements
  • Author(s): R. Majidi-Ahy ; M. Shakouri ; D.M. Bloom
  • Source: Electronics Letters, Volume 25, Issue 13, p. 828 –830
  • DOI:  10.1049/el:19890558
  • Type: Article
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  • p. 828 –830 (3)
    We report the development of an active electronic probe for 100 GHz on-wafer S-parameter measurements. Integrated on the substrate of this wafer probe were a quintupler for 100 GHz stimulus signal generation, two directional couplers for incident and reflected signals sampling, and two newly developed harmonic mixers to down-convert these 100 GHz signals to 20 MHz. We have also demonstrated all-electronic on-wafer 75-100 GHz two-port S-parameter measurements using these probes.
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Room-temperature operation of AlGaAs/GaAs resonant tunnelling structures grown by metalorganic vapour-phase epitaxy
1 Gbit/s, 32×32 high-speed space-division switching module for broadband ISDN using SST LSIs
Behaviour of circuit-switched multistage networks in presence of memory hot spot
Phase-noise-cancelling dual-frequency heterodyne optical fibre communication system
More boundary conditions at double current sheet
Continuously tunable single-frequency laser diode utilising transverse tuning scheme
Weighted overlap-add method for packet speech transmission
  • Author(s): S.N. Koh  and  P. Sivaprakasapillai
  • Source: Electronics Letters, Volume 25, Issue 13, p. 839 –840
  • DOI:  10.1049/el:19890565
  • Type: Article
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  • p. 839 –840 (2)
    A novel system which employs the filter bank analysis and synthesis method for the packetisation of speech is proposed. Preliminary computer simulation studies of the system and informal subjective listening tests indicate that significant improvement in the perceptual quality of the recovered speech can be obtained, compared with the conventional technique of straight packetisation of PCM speech.
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Second-order DFB lasers fabricated by deep UV contact lithography and GSMBE
  • Author(s): E. Goarin ; D. Bonnevie ; M. Boulou
  • Source: Electronics Letters, Volume 25, Issue 13, p. 840 –841
  • DOI:  10.1049/el:19890566
  • Type: Article
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  • p. 840 –841 (2)
    DFB ridge waveguide lasers at 1.55μm with uniform second-order gratings defined by deep UV lithography have been realised for the first time. The lasers have been fabricated using gas source molecular beam epitaxial (GSMBE) hetero-structures grown in a two-step process. The characteristics of the DFB lasers (28 mA minimum threshold current, single-mode behaviour at output power in excess of 5 mW for more than 80% of the lasers and very low dispersion (±0.6nm) of the lasing wavelength) demonstrate that deep UV lithography can be successfully used for the fabrication of DFB lasers.
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Double epitaxy improves single-photon avalanche diode performance
Measurement of transmitted power in untapered multifibre unions: oscillatory spectral behaviour
Three-beam amplification in BSO crystals
  • Author(s): D.C. Jones  and  L. Solymar
  • Source: Electronics Letters, Volume 25, Issue 13, p. 844 –845
  • DOI:  10.1049/el:19890569
  • Type: Article
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  • p. 844 –845 (2)
    It is shown that by applying the right detuning to two pump beams incident upon the BSO crystal from the same side, a third signal beam may be amplified. The maximum amplification was 12000 for a 1 cm-thick crystal which represents the highest value ever measured in BSO. It is further shown that the amplification strongly depends on the input power of the signal beam and full amplification is achieved for a beam ratio in excess of 107.
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High-speed (ft = 78 GHz) AlInAs/GaInAs single heterojunction HBT
  • Author(s): C.W. Farley ; M.F. Chang ; P.M. Asbeck ; N.H. Sheng ; R. Pierson ; G.J. Sullivan ; K.C. Wang ; R.B. Nubling
  • Source: Electronics Letters, Volume 25, Issue 13, p. 846 –847
  • DOI:  10.1049/el:19890570
  • Type: Article
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  • p. 846 –847 (2)
    High-performance AlInAs/GalnAs HBTs for low-power digital circuits have been demonstrated. Large-area devices exhibit high current gain (up to 600), observable down to low currents. Small-area devices display ft up to 78 GHz and fmax up to 45 GHz. Fitting S-parameter measurements to an equivalent circuit model shows that fmax is limited by a large RbCbc time constant in the base circuit. These transistors have been used to fabricate the first frequency divider demonstrated in this material system.
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AlGaAs Schottky reflection modulator and detector for Gbit/s optical transmission systems
Mode field profile converting optical channel waveguide with tapered refractive index and cross-section
Intermodulation and harmonic distortion in GaInAsP distributed feedback lasers
Architecture design of optical customer premises network
  • Author(s): H.J. Chao  and  L.S. Smoot
  • Source: Electronics Letters, Volume 25, Issue 13, p. 852 –853
  • DOI:  10.1049/el:19890574
  • Type: Article
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  • p. 852 –853 (2)
    A new optical customer premises network (CPN), which we call H-bus, has been designed to terminate future broadband ISDN signals and distribute the available bandwidth to terminal equipment connected to the CPN. The physical layer of the network makes use of the synchronous optical network (SONET) transmission format. The user information is carried using the asynchronous transfer mode (ATM) technique. The reliability of H-bus is improved through the use of a new optical component.
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Novel transverse electro-optic waveguide phase modulator realised in titanium-diffused and proton-exchanged LiNbO3
  • Author(s): S. McMeekin  and  R.M. de La Rue
  • Source: Electronics Letters, Volume 25, Issue 13, p. 853 –855
  • DOI:  10.1049/el:19890575
  • Type: Article
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  • p. 853 –855 (3)
    A new configuration for an electro-optic waveguide phase modulator, using electrodes transversely arranged on either side of a very thin substrate is described. The device has been tested with both titanium-indifTused and proton-exchanged waveguides in lithium niobate and used to estimate the electro-optic coefficients in the guides. Photorefractive effects have been observed in well-annealed single-mode protonexchanged waveguides at moderate power densities at λ = 0.6328 μm.
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High-efficiency pulsed GaAs pin avalanche diodes for V-band oscillators
CMOS quaternary latch
  • Author(s): K.W. Current
  • Source: Electronics Letters, Volume 25, Issue 13, p. 856 –858
  • DOI:  10.1049/el:19890577
  • Type: Article
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  • p. 856 –858 (3)
    A new CMOS current-mode quaternary threshold logic latch circuit is presented. This circuit accepts and requantises quaternary logical currents during a SETUP clock mode and latches the input value during the HOLD clock mode. Using logical current increments of 10μA, the quaternary latch has been simulated to have a worst-case, three logic level transition, total SETUP and HOLD time of about 40 ns, and single level transition total SETUP and HOLD time of about 10 ns.
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Effect of finite rectangular groundplane on near-in sidelobes of small linear slotted waveguide arrays
Capacitive coupling of floating body well to sensitive nodes prevents high-resistance CMOS circuit from latching-up
  • Author(s): M. Bafleur ; J. Buxo ; A. Elmoznine ; P. Rossel
  • Source: Electronics Letters, Volume 25, Issue 13, p. 860 –861
  • DOI:  10.1049/el:19890579
  • Type: Article
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  • p. 860 –861 (2)
    A new concept is derived whereby voltage transients occurring in the bulk substrate of a floating p− -well CMOS circuit can be conveniently decoupled near the sensitive n+/p− source-well parasitic junctions of n-channel transistors, thereby preventing latch-up occurrence. The ability of the well body to accommodate a nonequipotential situation is then taken advantage of to design a new and compact filter circuit that would certainly trigger latch-up if implemented on a grounded p−-well.
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Abrupt high hole concentration profiles in GaAs by Zn+P dual implantation
  • Author(s): A.C.T. Tang ; B.J. Sealy ; A. Rezazadeh
  • Source: Electronics Letters, Volume 25, Issue 13, p. 861 –863
  • DOI:  10.1049/el:19890580
  • Type: Article
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  • p. 861 –863 (3)
    In the letter we report that through the use of rapid thermal annealing (RTA) and the coimplantation of phosphorus an effective way of preventing the in-diffusion of zinc has been achieved. We have observed that the electrical activation characteristics of the Zn-implanted samples have been modified after the coimplantation of phosphorus. Furthermore, abrupt electrical profiles with hole concentrations of the order of 6×1019/cm3 have been achieved after annealing at 850°C for 30s.
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Reduction of optical-feedback-induced frequency noise in pigtailed laser diodes
Modelocking of AlGaAs laser diode by intracavity AlGaAs phase-modulator
Digital model for switching transistors in series-gated ECL
  • Author(s): C.S. Choy  and  C.Y. Ho
  • Source: Electronics Letters, Volume 25, Issue 13, p. 866 –867
  • DOI:  10.1049/el:19890583
  • Type: Article
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  • p. 866 –867 (2)
    A digital model is proposed that allows function verification and timing analysis of series-gated ECL to be performed on a logic simulator. Traditionally, an analogue simulator will be necessary because series-gated ECL circuits are constructed from transistors rather than primitive gates. The model is meant to replace each switching transistor in a series-gated ECL. A simulation time at least two magnitudes lower has been achieved.
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Slow-wave microcoplanar variable phase shifter
  • Author(s): A. Benghalia ; M. Ahmadpanah ; H. Baudrand
  • Source: Electronics Letters, Volume 25, Issue 13, p. 867 –868
  • DOI:  10.1049/el:19890584
  • Type: Article
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  • p. 867 –868 (2)
    The phase-shifting properties of a slow-wave microcoplanar structure are studied by means of a rigorous theoretical approach and the propagation losses are calculated. The Green function, which is used for the two-dimensional determination of the depletion layer profile, satisfies the real boundary conditions of the physical structure. The results obtained for the structure's electrical length are compared with the corresponding experimental data and a good agreement is obtained, in particular for zero-bias conditions.
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Interference resonance of microstrip patch antenna fed with coaxial probe
  • Author(s): J.P. Seaux ; A. Jecko ; A. Reineix
  • Source: Electronics Letters, Volume 25, Issue 13, p. 868 –870
  • DOI:  10.1049/el:19890585
  • Type: Article
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  • p. 868 –870 (3)
    This letter gives an interpretation of interference resonance in a microstrip patch antenna fed with coaxial probe and illuminated by electromagnetic pulses. An equivalent circuit is established over a wide frequency range. This circuit takes into account the interference resonance that we show in this study. Very good agreement is obtained between the analytical model, the numerical computation and the experimental measurements.
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Full-wave analysis of microstrip leaky-wave antenna
W-band GaAs camel-cathode Gunn devices produced by MBE
  • Author(s): R.B. Beall ; S.J. Battersby ; P.J. Grecian ; S. Jones ; G. Smith
  • Source: Electronics Letters, Volume 25, Issue 13, p. 871 –873
  • DOI:  10.1049/el:19890587
  • Type: Article
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  • p. 871 –873 (3)
    The DC and microwave performance of a novel secondharmonic W-band GaAs Gunn device incorporating a camel barrier are reported. Comparison with conventional Gunn devices shows significant improvement in power output and DC to RF conversion efficiency for the new structure. The frequency at which the maximum power is produced is lower for the camel cathode Gunn device, an observation attributed to a reduction in the length of the acceleration zone.
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Translinear class AB current amplifier
Scheme for phase-locking a local oscillator in submillimetre-wave receiver
  • Author(s): S. Padin
  • Source: Electronics Letters, Volume 25, Issue 13, p. 874 –875
  • DOI:  10.1049/el:19890589
  • Type: Article
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  • p. 874 –875 (2)
    A technique for phase-locking a low-power fundamental local oscillator in an SIS submillimetre-wave receiver is described. The arrangement uses the low-noise SIS mixer itself to downconvert the local oscillator signal from a Josephson junction or quantum well oscillator. A highfrequency phase-locked reference tone is required but for a typical SIS receiver the tone power is less than 10 nW. Even at terahertz frequencies this could easily be generated using a simple multiplier.
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Practical gain of in-line semiconductor laser amplifiers

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