Online ISSN
1350-911X
Print ISSN
0013-5194
Electronics Letters
Volume 29, Issue 19, 16 September 1993
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Volume 29, Issue 19
16 September 1993
Time-interleaved oversampling convertors
- Author(s): R. Khoini-Poorfard and D.A. Johns
- Source: Electronics Letters, Volume 29, Issue 19, p. 1673 –1674
- DOI: 10.1049/el:19931112
- Type: Article
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A new architecture is proposed which exploits the time-interleaving concept to increase the oversampling ratio in delta-sigma modulators. It is shown that the effective oversampling ratio is increased by a factor M through the use of M interconnected modulators. Although a high speed sample-and-hold circuit is still required for an analogue-to-digital convertor, speed constraints are significantly reduced for the majority of analogue parts such as loop filters, A/D and D/A blocks.
Optimal design of contiguous-band output multiplexers (COMUX)
- Author(s): G. Tanne ; S. Toutain ; J.F. Favennec ; P. Jarry ; C. Boschet
- Source: Electronics Letters, Volume 29, Issue 19, p. 1674 –1675
- DOI: 10.1049/el:19931113
- Type: Article
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A general multiplexer design procedure without dummy channels is described. The formulas are applied to the optimal design of practical contiguous or non-contiguous band multiplexers consisting of multicavity filters distributed along a waveguide manifold. All design parameters can be directly optimised. An example of a practical 12 channel, 12 GHz contiguous band multiplexer is presented.
Signal transform covariant to scale changes
- Author(s): R.G. Baraniuk
- Source: Electronics Letters, Volume 29, Issue 19, p. 1675 –1676
- DOI: 10.1049/el:19931114
- Type: Article
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A unitary signal transformation that is covariant by translation scale changes (dilations and compressions) in the signal is formulated and justified. Unlike the Mellin transform, which is invariant to scale changes, this new transform is a true indicator of the scale content of a signal.
Interfacial polarisation in Al-Y2O3-SiO2-Si capacitor
- Author(s): C.H. Ling
- Source: Electronics Letters, Volume 29, Issue 19, p. 1676 –1678
- DOI: 10.1049/el:19931115
- Type: Article
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The variation by a factor of 2 in the observed permittivity of yttrium oxide film is explained in terms of interfacial polarisation based on the Y2O3/SiO2 double-layer model. Provided the dielectric relaxation time constants of the two layers are grossly dissimilar, the model can also explain the frequency independence of the composite capacitor.
Combined-field integral equation
- Author(s): A. Helaly and H.M. Fahmy
- Source: Electronics Letters, Volume 29, Issue 19, p. 1678 –1679
- DOI: 10.1049/el:19931116
- Type: Article
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The combined-field integral equation (CFIE) is a linear combination of the H-field and the E-field integral equations. Previously, the weighting parameter of the E-field equation in the CFIE had been assumed constant along the generating curve of the body of revolution. However, in the Letter it is shown that the weighting parameter can take a variable distribution along the generating curve or on a part of it only. In the latter case, a reduction in the computational time of 40–50% is achieved.
Multimode chamber excited by an array of antennas
- Author(s): J.S. Hong
- Source: Electronics Letters, Volume 29, Issue 19, p. 1679 –1680
- DOI: 10.1049/el:19931117
- Type: Article
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The field distribution of a multimode chamber excited by an array of antennas consisting of rectangular waveguide apertures has been investigated. It is found that by controlling the locations, polarisations and phases of the sources (i.e. the aperture fields) the uniformity of field distribution in the chamber can be improved.
Improved design of CMOS multiple-input Muller-C-elements
- Author(s): S.L. Lu
- Source: Electronics Letters, Volume 29, Issue 19, p. 1680 –1682
- DOI: 10.1049/el:19931118
- Type: Article
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The Muller-C-element is a basic building block for selftimed digital circuits. It is used to realise the AND function for events (signal transitions). This Letter presents an improved n-input Muller C-element design which provides tighter conditions for hazard-free operation with reduced hardware cost.
Large nonlinear optical effect in an InGaAs/InAlAs multiquantum well waveguide
- Author(s): T. Kanetake ; H. Inoue ; S. Tanaka ; K. Ishida
- Source: Electronics Letters, Volume 29, Issue 19, p. 1682 –1684
- DOI: 10.1049/el:19931119
- Type: Article
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All-optical refractive nonlinearity in a passive InGaAs/InAlAs multiquantum well waveguide is evaluated for TE and TM modes at 1.55 μm wavelength and room temperature. A quarter wavelength change in the optical path length is observed at an input pump light power of 6.5 mW for 1.47 μm wavelength in a 960 μm long device. Nonlinear refractive index n2 is evaluated to be 1.2×10−6 and −0.5×10.6 cm2/W for the TE and the TM modes, respectively.
Surface-relief type Bragg grating reflector fabricated after overcladding removal
- Author(s): M. Ishii ; Y. Hibino ; A. Sugita ; T. Tamamura
- Source: Electronics Letters, Volume 29, Issue 19, p. 1684 –1685
- DOI: 10.1049/el:19931120
- Type: Article
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A novel silica-based Bragg grating reflector on Si substrate is described. The reflector is formed on a core whose overcladding layer is removed by RIE until it is level with the core surface. The reflector which comprises a rectangular relief type grating only 1.6 mm long has the advantages of a highly controllable Bragg wavelength and a high reflectivity of 76% for the TE mode.
α-factor improvements in high-speed p-doped In0.35Ga0.65As/GaAs MQW lasers
- Author(s): A. Schönfelder ; S. Weisser ; J.D. Ralston ; J. Rosenzweig
- Source: Electronics Letters, Volume 29, Issue 19, p. 1685 –1686
- DOI: 10.1049/el:19931121
- Type: Article
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The authors investigate experimentally for the first time the improvements in the linewidth enhancement factor, α, resulting from simultaneous addition of strain and p-doping in high-speed GaAs-based multiquantum well lasers. The α factor is determined from measured changes in both gain and refractive index as a function of CW bias current, yielding α 3.1 and 1.4 at the threshold lasing wavelength for unstrained GaAs/Al0.25Ga0.75As and p-doped strained In0.35Ga0.65As/GaAs devices, respectively.
Er-fibre lasers: suppression of spatial hole burning by internal modulation
- Author(s): R. Stolte and R. Ulrich
- Source: Electronics Letters, Volume 29, Issue 19, p. 1686 –1688
- DOI: 10.1049/el:19931122
- Type: Article
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Spatial hole burning is suppressed in linear Er3+ fibre lasers by two alternative modulation schemes. They move the standing wave pattern, formed by the two counterpropagating waves, along the gain medium in an oscillatory or continuous way. Output bandwidths <5kHz result.
Experimental evidence for hole transport limited intensity modulation response in quantum well lasers
- Author(s): R. Nagarajan ; R.P. Mirin ; T.E. Reynolds ; J.E. Bowers
- Source: Electronics Letters, Volume 29, Issue 19, p. 1688 –1690
- DOI: 10.1049/el:19931123
- Type: Article
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Direct experimental evidence is presented to show that it is the hole transport across wide separate confinement heterostructures and not the electron quantum capture that leads to the low frequency rolloff in the intensity modulation response of quantum well lasers.
GaInP/AlGaInP index waveguide-type visible laser diodes with dry-etched mesa stripes
- Author(s): T. Yoshikawa ; Y. Sugimoto ; H. Hotta ; K. Tada ; K. Kobayashi ; S. Kohmoto ; K. Asakawa ; H. Yoshii ; H. Kawano
- Source: Electronics Letters, Volume 29, Issue 19, p. 1690 –1691
- DOI: 10.1049/el:19931124
- Type: Article
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GaInP/AlGaInP index waveguide-type visible-light laser diodes with dry-etched mesa stripes have been fabricated by Cl2-reactive ion beam etching for the first time. The AlGaInP cladding layer, which is normally very difficult to dry etch due to problems with Al oxidation and the low volatility of In and its reaction products, was etched smoothly with high depth accuracy. The etched mesa stripes were buried by metal organic vapour-phase epitaxy with-out crystal discontinuity at the regrown surface. The threshold current under room-temperature pulsed operation is 35 mA (L = 300 μm), which is almost the same value as that for wet-etched lasers.
High-temperature (130°C) CW operation of 1.53 μm InGaAsP ridge-waveguide lasers using strained quaternary quantum wells
- Author(s): B. Stegmüller ; E. Veuhoff ; J. Rieger ; H. Hedrich
- Source: Electronics Letters, Volume 29, Issue 19, p. 1691 –1693
- DOI: 10.1049/el:19931125
- Type: Article
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Minimum threshold current density of 0.57kA/cm2 and high T0 values up to 74K were obtained from 400μm long broad area lasers with MOVPE grown compressively strained all-quaternary GaInAsP SCH-MQW layer structures for 1.53μm emission wavelength. With 3μm×400μm RW laserdiodes (T0>90K) high-temperature CW operation up to 130°C was achieved.
Room temperature continuous wave operation of red vertical cavity surface emitting laser diodes
- Author(s): J.A. Lott ; R.P. Schneider ; K.D. Choquette ; S.P. Kilcoyne ; J.J. Figiel ; J.A. Lott
- Source: Electronics Letters, Volume 29, Issue 19, p. 1693 –1694
- DOI: 10.1049/el:19931126
- Type: Article
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The first room temperature (23°C) continuous wave visible vertical cavity surface emitting laser diodes are reported. Annular contact devices with a 5 μm optical aperture in a 15 μm diameter mesa emit at 670.4 nm with a threshold current of 5 mA at 2.4V. Devices with 20–60 μm diameter mesas operate continuous wave below −13°C.
7.4 Gbit/s monolithically integrated GaAs/AlGaAs laser diode-laser driver structure
- Author(s): J. Hornung ; Z.-G. Wang ; W. Bronner ; E. Olander ; K. Köhler ; P. Ganser ; B. Raynor ; W. Benz ; M. Ludwig
- Source: Electronics Letters, Volume 29, Issue 19, p. 1694 –1696
- DOI: 10.1049/el:19931127
- Type: Article
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A molecular beam epitaxy (MBE) grown (GaAs/AlGaAs multi-quantum well laser, monolithically integrated with a laser driver, was realised on 2 inch GaAs substrate wafers. In an optical data communication setup, performance up to data rates of 7.4 Gbit/s was demonstrated.
Strained multiquantum-well corrugation-pitch-modulated distributed feedback laser with ultranarrow (3.6 kHz) spectral linewidth
- Author(s): M. Okai ; M. Suzuki ; T. Taniwatari
- Source: Electronics Letters, Volume 29, Issue 19, p. 1696 –1697
- DOI: 10.1049/el:19931128
- Type: Article
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Introducing a 1% compressive strained multiquantum-well (MQW) active layer into a corrugation-pitch-modulated distributed feedback (CPM-DFB) laser reduces the linewidth floor (residual linewidth for extrapolated infinite output power) to 2 kHz and results in a linewidth-power product of 140 kHz mW. Strained MQW CPM-DFB lasers produced a 55 mW output with a spectral linewidth of only 3.6 kHz.
Miniaturised L-band MIC LNA design
- Author(s): E. Bayar and A.H. Aghvami
- Source: Electronics Letters, Volume 29, Issue 19, p. 1698 –1699
- DOI: 10.1049/el:19931129
- Type: Article
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A design technique for LNA size miniaturisation is described which does not compromise electrical performance. The method has been applied to the design of an L-band LNA and results in a measured noise figure of 0.25 dB and 15 dB associated gain. The circuit it realised in MIC technology with a total surface area of less than 4.8 × 8.8 mm2. The reduced size allows the LNA to be cascaded with MMIC gain blocks with little or no volume impact and considerably improved electrical performance compared with a complete MMIC solution.
Planar MESFET transmission wave amplifier
- Author(s): T. Mader ; J. Schoenberg ; L. Harmon ; Z.B. Popović
- Source: Electronics Letters, Volume 29, Issue 19, p. 1699 –1701
- DOI: 10.1049/el:19931130
- Type: Article
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The authors present a quasioptical power combining transmission amplifier for increasing the power level available from solid-state circuits. Receiving and transmitting arrays of patch antennas, input/output isolation, MESFETs, bias and matching circuitry are contained on a single substrate, making monolithic millimetre-wave integration possible. The flexibility of selecting input polarisation with respect to the output while maintaining amplifier stability is demonstrated. A 24-MESFET patch antenna amplifier array is presented.
Extended backpropagation algorithm
- Author(s): Y.F. Yam and T.W.S. Chow
- Source: Electronics Letters, Volume 29, Issue 19, p. 1701 –1702
- DOI: 10.1049/el:19931131
- Type: Article
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A fast learning algorithm for feedforward neural networks is described. This algorithm is based on modifications to the backpropagation algorithm. The learning rate and momentum coefficient are adapted according to the coefficient of correlation between the downhill gradient and the previous weight update.
Novel technique to combine BWS and FWS classifiers
- Author(s): K.P. Lam and E. Home
- Source: Electronics Letters, Volume 29, Issue 19, p. 1702 –1704
- DOI: 10.1049/el:19931132
- Type: Article
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A novel approach to combining the binary weighted and frequency weighted schemes (BWS and FWS) for pattern classification is described. The method presented employs a well established statistical procedure and offers good performance. The principal advantages of the technique are that only a single layer is required and it avoids the serious problem of choosing optimal values for the zero-frequency components which occur in the FWS. Preliminary experiments demonstrate that the choice of operational parameters required is straightforward. Furthermore, the technique is intrinsically parallel and lends itself naturally to parallel implementation.
Design consideration of singlemode interconnectable star coupler
- Author(s): T. Ota
- Source: Electronics Letters, Volume 29, Issue 19, p. 1704 –1705
- DOI: 10.1049/el:19931133
- Type: Article
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The Letter reports design considerations for singlemode interconnectable star couplers which consist of directional couplers. The Letter describes a loss peculiar to this design consideration which arises from the reciprocity of the directional couplers.
Fast wavelength detection technique for multi-wavelength photonic packet networks
- Author(s): A.J. Keating and A.J. Lowery
- Source: Electronics Letters, Volume 29, Issue 19, p. 1705 –1706
- DOI: 10.1049/el:19931134
- Type: Article
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A wavelength detection technique for the control of transmitter wavelengths in WDM/FDM optical packet networks is demonstrated. The wavelength of a transmitter can be determined within a single packet duration (1.6 μs). We demonstrate optical frequency detection to an accuracy of ±75 MHz over a capture range of 6GHz.
Influence of simulated Brillouin scattering on nonlinear distortion in SCM video transmission
- Author(s): H. Yoshinaga
- Source: Electronics Letters, Volume 29, Issue 19, p. 1707 –1708
- DOI: 10.1049/el:19931135
- Type: Article
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It is shown analytically that nonlinear distortions are induced by stimulated Brillouin scattering in subcarrier multiplexed systems. They are expressed as a function of the additional loss of the transmission fibre which is induced by stimulated Brillouin scattering. Experimental results well support the theoretical conclusions.
Multichannel frequency conversion experiment using fibre four-wave mixing
- Author(s): K. Inoue ; T. Hasegawa ; K. Oda ; H. Toba
- Source: Electronics Letters, Volume 29, Issue 19, p. 1708 –1710
- DOI: 10.1049/el:19931136
- Type: Article
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Multichannel frequency conversion is demonstrated using fourwave mixing. A polarisation independent configuration is employed, by which polarisation control for each signal is not necessary. By setting the pump light frequency at the zero-dispersion wavelength of the fibre, three FSK modulated signals with a frequency spacing of 70 GHz are simultaneously converted with an equal efficiency of −27.5dB. Bit error rate measurements confirm the feasibility of this conversion scheme.
Nonlinear switching in InGaAsP laser amplifier directional couplers biased at transparency
- Author(s): D.A.O. Davies ; M.A. Fisher ; D.J. Elton ; S.D. Perrin ; M.J Adams ; G.T. Kennedy ; R.S. Grant ; P.D. Roberts ; W. Sibbett
- Source: Electronics Letters, Volume 29, Issue 19, p. 1710 –1711
- DOI: 10.1049/el:19931137
- Type: Article
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Ridge waveguide laser amplifier directional couplers have been developed to exploit recent observations of ultrafast refractive index changes in amplifiers biased at transparency. All-optical self-switching has been observed in a device with a bulk active region.
Suppression of soliton interactions by phase modulation
- Author(s): S. Wabnitz
- Source: Electronics Letters, Volume 29, Issue 19, p. 1711 –1713
- DOI: 10.1049/el:19931138
- Type: Article
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The Letter shows that the interactions of closely packed solitons in a long distance transmission system with bandwidth limited amplification may be suppressed by phase modulation. This removes the limitation to the maximum transmission distance that is set by the collision of adjacent solitons.
2.5 ps soliton pulse generation at 15 GHz with monolithically integrated MQW-DFBLD/MQW-EA modulator and dispersion decreasing fibre
- Author(s): K. Suzuki ; K. Iwatsuki ; S. Nishi ; M. Saruwatari ; K. Sato ; K. Wakita
- Source: Electronics Letters, Volume 29, Issue 19, p. 1713 –1714
- DOI: 10.1049/el:19931139
- Type: Article
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A soliton transmitter for an ultrahigh-speed optically time-division multiplexed soliton transmission is proposed that combines a monolithically integrated MQW-DFB-LD/MQW-EA modulator light source with a dispersion decreasing fibre. The resultant pulse width and time-bandwidth product are 2.5 ps and 0.33, respectively, at 15 GHz repetition rate.
Ultrahigh-speed phaselocked-loop-type clock recovery circuit using a travelling-wave laser diode amplifier as a 50 GHz phase detector
- Author(s): S. Kawanishi ; H. Takara ; M. Saruwatari ; T. Kitoh
- Source: Electronics Letters, Volume 29, Issue 19, p. 1714 –1716
- DOI: 10.1049/el:19931140
- Type: Article
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Successful operation of a phaselocked loop is demonstrated using travelling-wave laser-diode amplifier as a 50 GHz phase detector. Optical gain modulation in the laser diode amplifier and an optical clock multiplication technique using a silica-based guided-wave optical circuit are used to achieve the extremely highspeed operation. Also discussed is the possibility of more than 100 GHz operation.
Wavelength conversion of high speed data signals
- Author(s): B. Mikkelsen ; R.J.S. Pedersen ; T. Durhuus ; C. Braagaard ; M. Joergensen ; K.E. Stubkjaer
- Source: Electronics Letters, Volume 29, Issue 19, p. 1716 –1718
- DOI: 10.1049/el:19931141
- Type: Article
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Wavelength conversion of 5–10Gbit/s data channels is demonstrated by use of a DFB laser. A penalty free wavelength shift of 5 nm is obtained for data rates up to 8Gbit/s. The coupled optical input power is −1dBm and converted output power is l5dBm at the facet.
Linear optical path modulation with λ/200 accuracy using a fibre stretcher
- Author(s): F. Reynaud and E. Delaire
- Source: Electronics Letters, Volume 29, Issue 19, p. 1718 –1719
- DOI: 10.1049/el:19931142
- Type: Article
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The Letter reports the experimental generation of a linear optical path modulation of 20 λ range with an accuracy of λ/200 (λ = 633 nm) using a servo control system driving an optical fibre stretcher. The error signal is provided by mixing interferometric signals with an electronic oscillator.
Novel mid-infrared LED as a source for optical fibre gas sensing
- Author(s): S. McCabe and B.D. MacCraith
- Source: Electronics Letters, Volume 29, Issue 19, p. 1719 –1721
- DOI: 10.1049/el:19931143
- Type: Article
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A mid-infra-red LED emitting at 3.36μm (FWHM 400nm) is used as a source for evanescent wave flammable gas sensing with fluoride fibre. The system described has a detection limit for propane of 1.5%. These preliminary data demonstrate the potential for distributed gas sensing using novel LED sources.
Less than 3 pA/√Hz over 1–800 MHz noise current spectral density optical receiver for SCM-CATV systems
- Author(s): L. Pophillat and R. David
- Source: Electronics Letters, Volume 29, Issue 19, p. 1721 –1722
- DOI: 10.1049/el:19931144
- Type: Article
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A low noise optical receiver for SCM-CATV systems is described which uses discrete, commercial devices. By using a symmetrical resonance tuned input configuration, the equivalent input noise current spectral density, measured according to an accurate method, is less than 3 pA/√Hz in the frequency range 1–800 MHz.
21 Gbits/s/cm2 throughput density two-dimensional array optical interconnection construction
- Author(s): T. Kato ; F. Yuuki ; K. Tanaka ; H. Tanaka ; H. Masuda ; T. Tanoue ; A. Oishi ; K. Ito ; K. Murakami ; T. Teraoka
- Source: Electronics Letters, Volume 29, Issue 19, p. 1722 –1723
- DOI: 10.1049/el:19931145
- Type: Article
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A new two-dimensional array optical interconnection construction is developed for the board-to-board level. A high throughput density of 21 Gbit/s/cm2 over the electric coaxial cable limit is achieved by the direct hybridisation of an 8 × 2-channel LD/PD array onto the transmitter/receiver IC and surface-mount packaging of a microlens array and a fibre-connector receptacle.
High elevation angle propagation results, applied to a statistical model and an enhanced empirical model
- Author(s): M.A.N. Parks ; B.G. Evans ; G. Butt
- Source: Electronics Letters, Volume 29, Issue 19, p. 1723 –1725
- DOI: 10.1049/el:19931146
- Type: Article
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The results of a recent narrowband propagation experiment at high elevation angles have been further analysed to determine fit coefficients for the model proposed by Lutz et al. Results for the suburban and wooded environmental categories for elevation angles greater than 60° are reported. An empirical model for L and S bands covering elevation angles from 20 to 80° has been developed. The model combines the empirical roadside shadowing model, and the empirical fading model derived from the results of a narrowband propagation campaign, and improves the existing CCIR model.
Effect of base dopants on the bias stress stability of AlGaAs/GaAs HBTs
- Author(s): T. Ahmad ; A.A. Rezazadeh ; S.S. Gill
- Source: Electronics Letters, Volume 29, Issue 19, p. 1725 –1726
- DOI: 10.1049/el:19931147
- Type: Article
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The effect of three base dopants C, Be and Zn on the bias stress stability of npn AlGaAs/GaAs HBTs has been investigated for the first time. In this study 3 × 30μm2 HBTs were fabricated under identical process technology, emitter-base geometry and layout design. Following 24 h of identical bias stress, it is found that both Be- and Zn-doped devices exhibited current gain degradation as high as 68 and 57%, respectively, compared with only 7% for the C-doped device. The superior bias stress stability of C-doped HBTs is demonstrated.
Observation of new vibronic luminescence band in semiconducting diamond
- Author(s): J.A. Freitas ; P.B. Klein ; A.T. Collins
- Source: Electronics Letters, Volume 29, Issue 19, p. 1727 –1728
- DOI: 10.1049/el:19931148
- Type: Article
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Steady state and time-resolved photoluminescence studies have been carried out for a new vibronic emission band, with a zero phonon line at 2.395eV, that is observed in type IIb semiconducting diamond. This band exhibits a relatively slow (228ns) photoluminescence decay that is exponential, and is believed to be due to an internal transition at a defect site.
High temperature superconductor lumped element resonator
- Author(s): M.J. Lancaster ; J.C. Li ; A. Porch ; N.G. Chew
- Source: Electronics Letters, Volume 29, Issue 19, p. 1728 –1729
- DOI: 10.1049/el:19931149
- Type: Article
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The authors have studied a high temperature superconducting (HTS) lumped element resonator consisting of an inductance and capacitance in parallel. It has a low power unloaded quality factor Qo in excess of 9000 at 5.7GHz and 1K. The resonator is just over 1 mm square significantly smaller than any other device with comparable Q at this centre frequency. The authors also investigate the implementation of the resonator in a bandstop filter.
Elimination of all grating lobes in ultrasonic synthetic focusing using a linear array
- Author(s): C.Y. Rew ; S.B. Park ; J.B. Ra
- Source: Electronics Letters, Volume 29, Issue 19, p. 1729 –1731
- DOI: 10.1049/el:19931150
- Type: Article
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The Letter proposes a general scheme for eliminating all grating lobes in ultrasonic synthetic focusing using a linear array. The Letter also discusses the relationship between the element spacing, the generated grating lobes and the elimination scheme. Simulation results show the validity of the scheme.
Erratum: Optical short pulse generation by double gate operation of tandem connected electroabsorption modulators driven by sinusoidal voltages
- Author(s): H. Tanaka ; S. Takagi ; M. Suzuki ; Y. Matsushima
- Source: Electronics Letters, Volume 29, Issue 19, page: 1731 –1731
- DOI: 10.1049/el:19931151
- Type: Article
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Erratum: Level, downhill and uphill walking identification using neural networks
- Author(s): K. Aminian ; Ph. Robert ; E. Jequier ; Y. Schutz
- Source: Electronics Letters, Volume 29, Issue 19, page: 1731 –1731
- DOI: 10.1049/el:19931152
- Type: Article
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