Online ISSN
1350-911X
Print ISSN
0013-5194
Electronics Letters
Volume 28, Issue 2, 16 January 1992
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Volume 28, Issue 2
16 January 1992
Simplified parallel recision feedback equalisation for CCITT V.32/V.32 bis coded modems
- Author(s): P.B. Rapajić and B.S. Vucetić
- Source: Electronics Letters, Volume 28, Issue 2, p. 105 –106
- DOI: 10.1049/el:19920064
- Type: Article
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–106
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A simplified parallel decsion feedback equaliser (SPDFE) with the 32/64/128 AMPM CCITT trellis code is considered. The SPDEF detector consists of a whitened matched filter (WMF) and a reduced parallel decision feedback equaliser incorporated in the Viterbi decoder. The bit error rate simulation results show substantial improvement over the conventional detector with a linear equaliser and a separate Viterbi algorithm (LE & VA), although the implemation complexity remain the same.
Renewal theory validation of burst level technique for ATM simulation
- Author(s): J.M. Pitts and J.A. Schormans
- Source: Electronics Letters, Volume 28, Issue 2, p. 106 –107
- DOI: 10.1049/el:19920065
- Type: Article
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–107
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Renewal arrival processes are shown to be equivalent to a special class of general modulated deterministic process. This equivalence allows a direct comparsion of cell loss probability result obtained from renewal theory and from burst-level simulation. A case study is presented which shows excellent agreement between the two approaches, confirming the accuracy of the burst level method for ATM simulation studies.
Finite-state trellis representation of CPM
- Author(s): R. Liyanapathirana and N. Ekanayake
- Source: Electronics Letters, Volume 28, Issue 2, p. 108 –109
- DOI: 10.1049/el:19920066
- Type: Article
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–109
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In most of the literature it is claimed that the number of phase states in CPM is equal to q if p is even, and 2q if p is odd, where the modulation index h = p/q. In the Letter it is shown that a simple assumption due to Fornery leads to a simplified finite-state representation and also easily shows that CPM has q phase states.
Landscape reshaping algorithm for additive neural networks with application to graph mapping problems
- Author(s): K.V.K. Iyer ; H. Öǧmen ; Ç.K. Koç
- Source: Electronics Letters, Volume 28, Issue 2, p. 109 –111
- DOI: 10.1049/el:19920067
- Type: Article
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–111
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A neural network based algorithm for problems in nonconvex optimisation is described. The algorithm restricts the search by exploiting the properties of the parameter space. It keeps the initial point fixed and reshapes the energy function so that, in the neighbourhood of an arbitrary initial condition, basins of attraction are formed corresponding to valid solutions first and then these basins are made deeper to improve the quality. This algorithm was applied to both the travelling salesman problem (TSP) and the graph mapping problem (GMP) and good results were obtained.
Tunable green upconversion erbium fibre laser
- Author(s): J.Y. Allain ; M. Monerie ; H. Poignant
- Source: Electronics Letters, Volume 28, Issue 2, p. 111 –113
- DOI: 10.1049/el:19920068
- Type: Article
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–113
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50mW of green power and slope efficiency against launched pump power of 15% have been obtained at room temperature in an erbium doped fluorozirconate fibre pumped at 0.97μm. Lasing tunability domain, pump wavelength tunability and the role of colasing at 1.55μm are described.
Frequency dependent negative resistor in four phase network
- Author(s): J. Mikula
- Source: Electronics Letters, Volume 28, Issue 2, p. 113 –114
- DOI: 10.1049/el:19920069
- Type: Article
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–114
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A new frequency dependent negative resistor (FDNR) derived using the bilinear s-z transformation in a four phase switched capacitor (SC) network with one operational amplifier and four capacitors is presented. An SC inductor is obtained by a small alteration of the network.
‘Chirplets’ and ‘warblets’: novel time–frequency methods
- Author(s): S. Mann and S. Haykin
- Source: Electronics Letters, Volume 28, Issue 2, p. 114 –116
- DOI: 10.1049/el:19920070
- Type: Article
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–116
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A novel transform is proposed, which is an expanison of an arbitrary function onto a localised basis of multiscale chirps (swept frequency wave packets) for which the term ‘chirplets’ has been used. The wavelet transform is an expansion onto a basis of functions which are affine in the physical domain (e.g. time). In other words they are translates and dilates of one mother wavelet. The proposed basis is an extension of affinity, from the physical (time) domain, to the time-frequency domain. The basis includes both the wavelet and the short-time Fourier transform (STFT) as special cases (the degree of freedom modulation is simply attained through a translation in frequency). Furthermore, the basis include shear in time, and shear in frequency, leading to a broader class of chirping bases. Numerous practical applications of the chirplet have been found, such as in Doppler radar signal processing.
Performance comparison of subcarrier multiplexed coherent systems using optical intensity and phase modulators
- Author(s): Q. Jiang and M. Kavehrad
- Source: Electronics Letters, Volume 28, Issue 2, p. 116 –117
- DOI: 10.1049/el:19920071
- Type: Article
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–117
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The performance of subcarrier multiplexed coherent systems is compared theoretically using optical intensity and phase modulators. The results show that a subcarrier multiplexed coherent system with a symmetrical optical intensity modulator can offer a receiver sensitivity improvement as high as 9.1 dB over that with an optical phase modulator.
Nonlinear transmission of 20 Gbit/s optical time-division-multiplexed data, over 205 km of dispersion shifted fibre
- Author(s): G.E. Wickens ; D.M. Spirit ; L.C. Blank
- Source: Electronics Letters, Volume 28, Issue 2, p. 117 –118
- DOI: 10.1049/el:19920072
- Type: Article
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–118
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Nonlinear pulse compression has been used to achieve transmission beyond the linear dispersion limit for 20 Gbit/s optical time-division-multiplexed data. Error free system operation has been achieved over an operating wavelength range of 10nm above the wavelength of zero dispersion, in the anomalous dispersion regime.
Fast algorithm for finding primitive polynomials over GF(q)
- Author(s): A. Di Porto ; F. Guida ; E. Montolivo
- Source: Electronics Letters, Volume 28, Issue 2, p. 118 –120
- DOI: 10.1049/el:19920073
- Type: Article
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–120
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An efficient algorithm for the construction of primitive polynomials of degree m over GF(q) is proposed. The algorithm runs in time 0(km2), where k is an integer such that gcd (k, qm−1) = 1.
High performance 10 Gbit/s pin-FET optical receiver
- Author(s): E.M Kimber ; B.L. Patel ; I. Hardcastle ; A. Hadjifotiou
- Source: Electronics Letters, Volume 28, Issue 2, p. 120 –122
- DOI: 10.1049/el:19920074
- Type: Article
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–122
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An optical receiver suitable for a 10 Gbit/s direct detection optical transmission system is described. It uses a pin diode, commercial GaAs MESFETs and hybrid construction techniques on a coplanar substrate. The measured sensitivity of the receiver is –20.4 dBm, which is the best reported sensitivity at 10 Gbit/s for a pin-FET optical receiver to date.
Design of multiplierless FIR filters by multiple use of the same filter
- Author(s): Y.-L. Tai and T.-P. Lin
- Source: Electronics Letters, Volume 28, Issue 2, p. 122 –123
- DOI: 10.1049/el:19920075
- Type: Article
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–123
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A novel approach to the design of multiplierless filters, based on the ACF (amplitude change function) [1], is discussed. The prototype filter chosen is a CCOS (the cascade of the cosine functions) which requires no multipliers and only some adders. The required filter specifications are met by multiple use of the same CCOS filter. Effects due to coefficient quantisation do not arise when using the new approach. No multipliers are required to implement this filter.
Optical switching characteristics of a bistable resonant tunnelling light emitting diode
- Author(s): C. van Hoof ; J. Genoe ; R.P. Mertens ; E. Goovaerts ; G. Borghs
- Source: Electronics Letters, Volume 28, Issue 2, p. 123 –124
- DOI: 10.1049/el:19920076
- Type: Article
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–124
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The electrical and optical characteristics of a bistable resonant tunnelling light emitting diode are reported. The maximum frequency of operation is determined by electron tunnelling escape rather than by radiative recombination. Switching time constants of less than 200 ps are measured, limited by the duration of the electrical excitation.
Broadband tunable single frequency diode-pumped erbium doped fibre laser
- Author(s): C.R.Á Cochláin and R.J. Mears
- Source: Electronics Letters, Volume 28, Issue 2, p. 124 –126
- DOI: 10.1049/el:19920077
- Type: Article
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–126
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A single frequency erbium fibre laser with continuous wavelength tuning over the range 1525–1568 nm has been demonstrated using a unidirectional loop mirror (ULM) configuration. The fibre laser is diode pumped at 1480 nm with a threshold of 9mW, slope efficiency of 12% and has a linewidth of less than 295 kHz.
Scattering from finite array of microstrip patches on uniaxial substrate
- Author(s): W.J. Bow ; A.S. King ; C.E. Lee
- Source: Electronics Letters, Volume 28, Issue 2, p. 126 –127
- DOI: 10.1049/el:19920078
- Type: Article
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–127
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The problem of plane wave scattering by a finite size array of rectangular microstrip patches printed on a uniaxially anisotropic substrate is considered. Computed radar cross-section data for microstrip patch antenna arrays are presented as a function of array size, incident signal frequency, and anisotropy.
High-power 0.82μm superluminescent diodes with extremely low Fabry–Perot modulation depth
- Author(s): S.A. Safin ; A.T. Semenov ; V.R. Shidlovski ; N.A. Zhuchkov ; Yu.V. Kurnyavko
- Source: Electronics Letters, Volume 28, Issue 2, p. 127 –129
- DOI: 10.1049/el:19920079
- Type: Article
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–129
(3)
Superluminescent AlGaAs/GaAs diodes with 15mW output power and 1% Fabry–Perot modulation depth and modules with 3mW polarisation maintaining fibre output have been developed. At output powers of more than 8 mW the effect of saturation on power fluctuations was observed.
Analysis of multiport rectangular waveguide devices using pulsed finite-difference time-domain (FDTD) technique
- Author(s): J.C. Olivier and D.A. McNamara
- Source: Electronics Letters, Volume 28, Issue 2, p. 129 –131
- DOI: 10.1049/el:19920080
- Type: Article
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–131
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The pulsed FDTD method is used to analyse multiport junctions in recgtangular waveguide. Two representative examples are considered, namely the H-plane tee junction and the folded H-plane tee junction. Computed results for the scattering parameters are compared to measurements performed by the authors.
D-fibre filter for erbium gain spectrum flattening
- Author(s): M. Wilkinson ; A. Bebbington ; S.A. Cassidy ; P. McKee
- Source: Electronics Letters, Volume 28, Issue 2, p. 131 –132
- DOI: 10.1049/el:19920081
- Type: Article
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A novel type of filter based on D fibre with an overlay grating is proposed. The fabrication and characterisation of the device are described and its use in an erbium doped fibre amplifier to obtain a flatter gain spectrum is discussed.
Very wide spectrum multiquantum well superluminescent diode at 1.5 μm
- Author(s): S. Kondo ; H. Yasaka ; Y. Noguchi ; K. Magari ; M. Sugo ; O. Mikami
- Source: Electronics Letters, Volume 28, Issue 2, p. 132 –133
- DOI: 10.1049/el:19920082
- Type: Article
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–133
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An InGaAs/InGaAsP multiquantum well superluminescent diode (SLD) emitting at 1-5 μm has been studied. Broad spectral widths exceeding 100 nm are achieved under a wide injection current range. The maximum spectral width is 170nm, which gives a calculated coherence length of 13 μm, approximately one third that of 1.5 μm conventionally available bulk SLDs.
New canonical state-variable structure and its application in digital filtering
- Author(s): V. Tavsanoglu
- Source: Electronics Letters, Volume 28, Issue 2, p. 133 –135
- DOI: 10.1049/el:19920083
- Type: Article
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A new state-variable structure with minimum number of multipliers is introduced. It is obtained by the application of the bilinear transformation to the direct form structure. It is also shown that the roundoff-noise gain is invariant under LP-LP transformation for the new structure.
Proportion of primes generated by strong prime methods
- Author(s): J. Shawe-Taylor
- Source: Electronics Letters, Volume 28, Issue 2, p. 135 –137
- DOI: 10.1049/el:19920084
- Type: Article
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The numbers of primes generated by two prime generation methods are evaluated. The methods considered generate strong primes for cryptographic use in the RSA public-key cryptosystem. The results show that they generate sufficiently many primes to resist cryptanalytic attack by prime enumeration for the sizes of primes used to guard against factorisation attack.
Some new runlength constrained binary modulation codes with error-correcting capabilities
- Author(s): A.S.J. Helberg and H.C. Ferreira
- Source: Electronics Letters, Volume 28, Issue 2, p. 137 –139
- DOI: 10.1049/el:19920085
- Type: Article
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Five new combined error-correcting (d, k) codes for use on bandwidth limited channels are presented. These new codes are compared to known codes with similar parameters. The error behaviour of the new codes after Viterbi decoding on the binary symmetric channel is evaluated by simulation. The power spectral densities are also measured and the results presented.
First order quasiphase matching in LiNbO3
- Author(s): F. Armani ; D. Delacourt ; E. Lallier ; M. Papuchon ; Q. He ; M. de Micheli ; D.B. Ostrowsky
- Source: Electronics Letters, Volume 28, Issue 2, p. 139 –140
- DOI: 10.1049/el:19920086
- Type: Article
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First order quasiphase matched second harmonic generation in LiNbO3 channel waveguides is experimentally demonstrated and compared with theoretical estimation. Conversion efficiencies of 11%/W for l cm long interaction length were measured for the generation of 435 and 450 nm blue light, which is the same order of magnitude as calculated for the structure.
New empirical nonlinear model for HEMT devices
- Author(s): I. Angelov and H. Zirath
- Source: Electronics Letters, Volume 28, Issue 2, p. 140 –142
- DOI: 10.1049/el:19920087
- Type: Article
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–142
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A new large signal model for HEMTs, capable of modelling the current–voltage characteristic and its derivatives, including the characteristic transconductance peak, is described. Model parameter extraction is straightforward and is made for a submicrometre gatelength δ-doped pseudomorphic HEMT. Measured and modelled DC and S parameters are compared.
Thermal stability of indium-tin-oxide/n-GaAs Schottky diodes
- Author(s): Y.H. Aliyu ; D.V. Morgan ; R.W. Bunce
- Source: Electronics Letters, Volume 28, Issue 2, p. 142 –144
- DOI: 10.1049/el:19920088
- Type: Article
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The thermal degradation of ITO Schottky contacts on GaAs has been studied. The rectifying contacts show rapid degradation with heating and could have serious implications for optoelectronic devices that operate at elevated temperatures.
Low threshold current density (760 A/cm2) and high power (45 mW) operation of strained Ga0.42In0.58P multiquantum well laser diodes emitting at 632 nm
- Author(s): A. Valster ; C.J. van der Poel ; M.N. Finke ; M.J.B. Boermans
- Source: Electronics Letters, Volume 28, Issue 2, p. 144 –145
- DOI: 10.1049/el:19920089
- Type: Article
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–145
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A record low threshold current density of 760 A/cm2 has been obtained for a compressively strained multiquantum well laser emitting at 632 nm. Narrow stripe gain guided lasers show a maximum continuous output power of 45 mW with normally passivated mirrors. Stable laser operation over more than 3000 h at 40°C and 2 mW output power is reported for the first time.
Quasiballistic electron transport in InP/InGaAs heterojunction bipolar transistors
- Author(s): Y.F. Yang ; P.A. Houston ; M. Hopkinson
- Source: Electronics Letters, Volume 28, Issue 2, p. 145 –147
- DOI: 10.1049/el:19920090
- Type: Article
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–147
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Quasiballistic electron transport in the InGaAs base of an npn HBT with an InP tunnel injector has been observed for the first time using the technique of hot-electron spectroscopy. Electrons injected from the emitter which are not scattered retain a narrow energy distribution after traversing the base. The contribution of the quasiballistic electrons to the total collector current has also been estimated.
M3-NET: demonstration of HD WDM optical network using two-electrode DFB-LD filter as tunable narrowband FM receiver
- Author(s): M.J. Chawki ; R. Auffret ; E. Le Coquil ; L. Berthou ; J. Le Rouzic ; L. Demeure
- Source: Electronics Letters, Volume 28, Issue 2, p. 147 –149
- DOI: 10.1049/el:19920091
- Type: Article
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M3-NET is a multiwavelength optical network configuration for broadband communications. It uses multielectrode DFB LDs as both transmitter and receiver acting as a multifunction device. The selection of either spaced or dense wavelengths transmitting a high and low bit rate was successfully achieved. First experimental results of a fully connected three channel M3-NET are presented.
Tapered optical fibre dye laser
- Author(s): G. Pendock ; H.S. Mackenzie ; F.P. Payne
- Source: Electronics Letters, Volume 28, Issue 2, p. 149 –150
- DOI: 10.1049/el:19920092
- Type: Article
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The fabrication of an optical fibre dye laser with a pump threshold of only 28 mW using DCM dye is reported. The laser relies on the interaction between the evanescent field of a tapered single optical mode fibre and a surrounding laser dye solution.
High temperature (90°C) CW operation of 646 nm InGaAlP laser containing multiquantum barrier
- Author(s): J. Rennie ; M. Watanabe ; M. Okajima ; G. Hatakoshi
- Source: Electronics Letters, Volume 28, Issue 2, p. 150 –151
- DOI: 10.1049/el:19920093
- Type: Article
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CW laser operation of a 646 nm InGaAlP laser, incorporating a multiquantum barrier (MQB), is shown for the first time. The maximum temperature of operation was raised by 20°C, in comparison to an identical laser without an MQB layer, to 90°C. This increase is taken as direct evidence of the authenticity of the MQB effect.
Construction of neural networks to approximate arbitrary continuous functions of one variable
- Author(s): C.-H. Choi and J.Y. Choi
- Source: Electronics Letters, Volume 28, Issue 2, p. 151 –153
- DOI: 10.1049/el:19920094
- Type: Article
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A novel method is introduced for determining the connection weights of three layer neural networks which approximate any continuous functions of one variable. The derived formulas to calculate the weights explain the roles of hidden neurons and connection weights of three layer neural networks. It is demonstrated, by examples, that this method yields an easy and efficient construction of neural networks without needing training to approximate a function of one variable.
DFB-LD/modulator integrated light source by bandgap energy controlled selective MOVPE
- Author(s): T. Kato ; T. Sasaki ; K. Komatsu ; I. Mito
- Source: Electronics Letters, Volume 28, Issue 2, p. 153 –154
- DOI: 10.1049/el:19920095
- Type: Article
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The bandgap energy of an In/InP multiquantum well structure, selectively grown by MOVPE, was controlled along the waveguide direction by controlling the mask stripe width. A butt-jointless DFB-LD/modulator light source was fabricated by using this technique.
Extremely low threshold current, buried-heterostructure strained InGaAs-GaAs multiquantum well lasers
- Author(s): J.W. Xiao ; J.Y. Xu ; G.W. Yang ; J.M. Zhang ; Z.T. Xu ; L.H. Chen
- Source: Electronics Letters, Volume 28, Issue 2, p. 154 –156
- DOI: 10.1049/el:19920096
- Type: Article
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A very low CW threshold current of l.65 mA at room temperature was obtained for an uncoated burie-dheterostructure strained layer multiquantum well InGaAs-GaAs laser fabricated using hybrid molecular beam epitaxy and liquid phase epitaxy crystal growth technique. External differential quantum efficiency as high as 446% (0.53 mW/mA) and output power of more than 30mW per facet were achieved in the same laser.
New technique for measuring electromagnetic fields
- Author(s): S.Q. Zhang and D.J. Edwards
- Source: Electronics Letters, Volume 28, Issue 2, p. 156 –157
- DOI: 10.1049/el:19920097
- Type: Article
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A new light modulated array technique for measuring electromagnetic fields is described. The array element used is a dipole made using a photodiode. A modulated laser scanning system is used to scan the array. When the photodiode element is illuminated by the modulated laser beam, the selfimpedance of the dipole is itself modulated, and the secondary wave is detected by a remote receiver. Because the array is isolated and of small scatter cross-section, the disturbance to the measured field is minimised. An example measurement at 8.5 GHz is described. The results indicate that the technique provides a rapid method of imaging electromagnetic fields. The limitations of this approach are also discussed.
Cryptanalysis and modification of digital signature scheme based on error-correcting code
- Author(s): L. Ham and D.-C. Wang
- Source: Electronics Letters, Volume 28, Issue 2, p. 157 –159
- DOI: 10.1049/el:19920098
- Type: Article
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W. Xinmei proposed a digital signature scheme based on the error-correcting code. The Letter points out that in the Xinmei scheme it is possible to combine valid signatures of messages into a valid signature of another message in polynomial time even when the factoring of large matrices is unknown. Some modifications are suggested to improve the security and performance
Silicon germanium optical waveguides with 0-5 dB/cm losses for singlemode fibre optic systems
- Author(s): S.F. Pesarcik ; G.V. Treyz ; S.S. Iyer ; J.M. Halbout
- Source: Electronics Letters, Volume 28, Issue 2, p. 159 –160
- DOI: 10.1049/el:19920099
- Type: Article
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Silicon germanium waveguides with losses of less than 1 dB/cm have been fabricated and characterised at 1-32/nn. Propagation losses are as low as 0-62dB/cm for TM polarised light and 0-50dB/cm for TE polarised light.
Enhancement mode n-channel Si/SiGe MODFET with high intrinsic transconductance
- Author(s): U. König ; A.J. Boers ; F. Schäffler ; E. Kasper
- Source: Electronics Letters, Volume 28, Issue 2, p. 160 –162
- DOI: 10.1049/el:19920100
- Type: Article
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n-channel Si/SiGe MODFETs with quantum wells grown on a thick (1.5μm) graded buffer (Ge 5–30%) are realised. MODFETs with a surface gate work in the depletion mode due to a large gate-to-2-DEG channel distance of 75 nm. MODFETs with a recessed gate 10–15 nm above the channel exhibit enhancement mode operation with significantly high extrinsic transconductances of 340 mS/mm or 670 mS/mm at 300 K or 77 K and corresponding intrinsic transconductances of 38O mS/mm or 800 m S7/mm. The performance indicates the improved layer quality on graded buffers.
Ring laser operation at 1.3μ of Pr3+-doped fluoride singlemode fibre
- Author(s): Y. Ohishi and T. Kanamori
- Source: Electronics Letters, Volume 28, Issue 2, p. 162 –164
- DOI: 10.1049/el:19920101
- Type: Article
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Ring laser operation is performed at 1.3μm using Pr3+-doped fluoride singlemode fibre with a high numerical aperture. The operating wavelength, laser threshold and slope efficiency are 1.2994μm, 60mW and 0.16%, respectively.
Infra-red surface plasmons on platinum silicide
- Author(s): A. Sellai ; P. Dawson ; W.R. Hendren ; S.H.S. Magill ; H.S. Gamble
- Source: Electronics Letters, Volume 28, Issue 2, p. 164 –165
- DOI: 10.1049/el:19920102
- Type: Article
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It is shown that surface plasmons (SPs) are supported on thin PtSi films. Using a prism-air gap-sample configuration, p-polarised infra-red light (3.39 μm) has been coupled with ̃95% efficiency to SPs on the silicide electrode of PtSi-Si Schottky barrier structures. Stimulating SPs offers both a means of optically characterising silicide films and of enhancing optical absorption with a view to significantly increasing the Schottky barrier photoresponse.
Determination of equivalent circuit parameters of porous dielectric humidity sensors
- Author(s): A.E. Falk ; B.M. Lacquet ; P.L. Swart
- Source: Electronics Letters, Volume 28, Issue 2, p. 166 –167
- DOI: 10.1049/el:19920103
- Type: Article
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A humidity sensitive porous dielectric is modelled by an equivalent electrical circuit consisting of four passive elements. The model parameters are obtained by applying a nonlinear curvefit procedure on the frequency dependence of the measured capacitance and parallel resistance as a function of relative humidity.
1 GHz CMOS 1/8 static frequency divider operating at 1V
- Author(s): Y. Kado ; M. Suzuki ; Y. Okazaki ; T. Kobayashi
- Source: Electronics Letters, Volume 28, Issue 2, p. 167 –169
- DOI: 10.1049/el:19920104
- Type: Article
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A CMOS divide-by-eight static frequency divider operating at 1.0 GHz and dissipating only 1.7mW at a supply voltage of 1.0 V is described. The corresponding power and power-delay products for the first stage toggle-type flipflop (T-F/F) are 0.32mW and 0.32 pJ, which are the best yet reported for any CMOS flipflop. The divider owes its high performance to 0.2 μm gate CMOS process technology and a new differential static T-F/F circuit. This divider is particularly suitable for dividing communication band frequencies in the front end of a battery-operated wireless hand-held terminal for personal communication.
Detection scheme of coherence multiplexed sensor signals by using optical loop incorporating frequency shifter
- Author(s): K. Iiyama ; M. Harano ; K. Hayashi ; Y. Ida ; T. Kadoshima ; Y. Kurasawa
- Source: Electronics Letters, Volume 28, Issue 2, p. 169 –171
- DOI: 10.1049/el:19920105
- Type: Article
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A detection scheme of coherence multiplexed sensor signals by using an optical loop incorporating a frequency shifter is proposed and demonstrated. The sensor signals are frequency-multiplexed, and consequently, the numbers of the receiving interferometers and the photodetectors can be reduced.
Novel technique for determining internal loss of individual semiconductor lasers
- Author(s): P.A. Andrekson ; N.A. Olsson ; T. Tanbun-Ek ; R.A. Logan ; D. Coblentz ; H. Temkin
- Source: Electronics Letters, Volume 28, Issue 2, p. 171 –172
- DOI: 10.1049/el:19920106
- Type: Article
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A novel and accurate technique for measuring the internal losses of semiconductor lasers is demonstrated. The technique is based on two measurements: the injection current required for reaching material transparency and the corresponding ripple in the spontaneous emission spectrum. This method, which is independent of the internal quantum efficiency, allows the measurement of individual laser chips rather than an ensemble of chips, and can also be used to determine the loss dependence on wavelength and temperature.
Modified SAW diode convolver
- Author(s): J.H. Yin ; K.X. Shen ; Y. Shui ; Z.L. Jiang ; S.P. He
- Source: Electronics Letters, Volume 28, Issue 2, p. 172 –174
- DOI: 10.1049/el:19920107
- Type: Article
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A modified SAW diode convolver is presented which works with backward biased diodes, so that no bias resistor is needed and taps are isolated from one another. The new distribution of taps makes it possible for the convolver to operate at lower frequencies and enables a relatively wide bandwidth. The experimental results of a device with 28 taps have been given.
Suboptimal model reduction VIA least-square approximation of time-response by its derivatives and integrals
- Author(s): P. Vilbé ; L.C. Calvez ; M. Sévellec
- Source: Electronics Letters, Volume 28, Issue 2, p. 174 –175
- DOI: 10.1049/el:19920108
- Type: Article
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The reduction of an SISO system is formulated as the minimisation of the l2 criterion. Expansions of a time-response function in terms of its derivatives and integrals are proposed. Approximation of the quadratic criterion reduces the nonlinear determination of the denominator to a simple linear system resolution. An efficient method for evaluation of the required scalar products of repeated integrals and derivatives is proposed.
Actively mode-locked and passively Q-switched operation of thulium-doped fibre laser using multiquantum well asymmetric Fabry-Perot modulator
- Author(s): N. Kishi ; J.N. Carter ; R. Mottahedeh ; P.R. Morkel ; R.G. Smart ; A.J. Seeds ; D.N. Payne ; A.C. Tropper ; D.C. Hanna ; J.S. Roberts ; C.C. Button
- Source: Electronics Letters, Volume 28, Issue 2, p. 175 –177
- DOI: 10.1049/el:19920109
- Type: Article
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An actively mode-locked and passively Q-switched thulium-doped fluorozirconate fibre laser using an AlGaAs/GaAs multiquantum well (MQW) asymmetric Fabry-Perot modulator (AFPM) is reported. This is the first demonstration of active mode locking of fibre lasers using MQW modulators. Mode locked pulse trains of 6 ns pulsewidth are obtained within a Q-switched envelope of 400 ns duration.
HF peak limiting for transmission of HDMAC via FSS satellites
- Author(s): W. Dobbie ; G. Horst ; M. Harverson ; D. Praetzas
- Source: Electronics Letters, Volume 28, Issue 2, p. 177 –178
- DOI: 10.1049/el:19920110
- Type: Article
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The use of HF peak limiting to allow increased FM deviation without unacceptable truncation noise is described for two typical FSS satellite channel bandwidths. The results of subjective tests with a typical picture are then presented for the case with a channel bandwidth of 36 MHz.
20 W CW monolithic AlGaAs (810 nm) laser diode arrays
- Author(s): M. Sakamoto ; J.G. Endriz ; D.R. Scifres
- Source: Electronics Letters, Volume 28, Issue 2, p. 178 –180
- DOI: 10.1049/el:19920111
- Type: Article
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Good continuous-wave (CW) lifetimes have been demonstrated for 1 cm wide monolithic AIGaAs laser diode arrays (810 nm) with a 4800 μm total aperture width at a power level of 20 W. This represents the highest CW power level at which long lifetimes have been obtained.
2-D adaptive Volterra filter for 2-D nonlinear channel equalisation and image restoration
- Author(s): J.-N. Lin and R. Unbehauen
- Source: Electronics Letters, Volume 28, Issue 2, p. 180 –182
- DOI: 10.1049/el:19920112
- Type: Article
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A 2-D adaptive nonlinear filter, namely the 2-D adaptive Volterra filter, is developed with an LMS type of adaptation algorithm. This adaptive filter is used for equalising an unknown 2-D channel with some pointwise nonlinearity and restoring images degraded by this channel. Improvements over a 2-D adaptive linear equaliser are demonstrated by experimental results.
Stabilising er fibre soliton laser with pulse phase locking
- Author(s): X. Shan ; D. Cleland ; A. Ellis
- Source: Electronics Letters, Volume 28, Issue 2, p. 182 –184
- DOI: 10.1049/el:19920113
- Type: Article
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A stabilisation scheme for a mode-locked erbium fibre laser which relies on locking the pulse phase with that of the drive source is reported. Using this scheme, the first bit-error-rate (BER) measurement on such a laser has been demonstrated. Stable error free operation at 2Gbit/s and a received power of 26dBm has been observed over a period of >0.5h showing the potential suitability of the laser as a transmission source.
Beam-steerable active array antenna
- Author(s): R. Fralich and J. Litva
- Source: Electronics Letters, Volume 28, Issue 2, p. 184 –185
- DOI: 10.1049/el:19920114
- Type: Article
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An integrated beam-steerable antenna configuration is presented in which an active resonant patch provides a simple and compact source of surface waves that radiate from a periodic surface along a dielectric waveguide. An X-band antenna has been developed and measurements carried out to determine its performance. A simple passive leaky-wave antenna model has also been developed. Comparisons between the measurements and the model indicate that the main lobe of the far-field pattern remains robust over the 0.6 GHz tuning bandwidth of the active source.
Scattering solution of oblong, dielectric coated, metallic scatterers by recursive algorithm
- Author(s): J.-H. Lin and W.C. Chew
- Source: Electronics Letters, Volume 28, Issue 2, p. 185 –187
- DOI: 10.1049/el:19920115
- Type: Article
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The recursive aggregate T-matrix algorithm is used for the scattering solution of an oblong, multilayer, dielectric coated ogive body. Because the recursive algorithm has reduced computational complexity and memory requirement, the scattering solution of a 10-wavelength long ogive coated with dielectric layers can be calculated on a PC and the solution agrees well with the method of moments.
Simple analytical model for power DMOS transistors
- Author(s): P. Kuivalainen ; M. Grönlund ; H. Ronkainen
- Source: Electronics Letters, Volume 28, Issue 2, p. 187 –188
- DOI: 10.1049/el:19920116
- Type: Article
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A simple analytical DC model has been developed for power DMOS transistors in a strong inversion. The model takes into account some special features of the new short channel DMOSTs such as local heating effects, a large voltage drop in the drift region and a mobility degradation at large drain source voltages. The model provides a good agreement with the measured data even when only a small number of fitting parameters are used.
Gain-switching of dbr laser monolithically integrated with electroabsorption modulator for RZ transmission
- Author(s): G. Raybon ; P.B. Hansen ; U. Koren ; B.I. Miller ; M.G. Young ; R.M. Jopson ; J.D. Evankow ; C.A. Burrus
- Source: Electronics Letters, Volume 28, Issue 2, p. 188 –190
- DOI: 10.1049/el:19920117
- Type: Article
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A photonic integrated transmitter for RZ transmission provides 50 ps optical pulses on-off modulated at a bit rate of 3Gbit/s. BER performance is measured in a back-to-back transmission experiment and compared to NRZ transmission using the same photonic circuit with the laser operated CW. A 2.8 dB improvement in receiver sensitivity is obtained for the RZ case.
Novel technique for time-delay beamforming
- Author(s): D.G. Powell and A.G.J. Holt
- Source: Electronics Letters, Volume 28, Issue 2, p. 190 –192
- DOI: 10.1049/el:19920118
- Type: Article
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An approach is presented to sampling rate reduction in a digital time-delay beamforming system. Beam pattern shape is retained at low sampling frequencies while involving only a small amount of additional hardware, unlike conventional reduced sampling rate systems. The technique is applied to an underwater acoustic beam-forming system.
Effect of finite substrate width on higher-order mode generation of electrically shielded symmetric microstrip
- Author(s): J.-D. Tseng and C.-K.C. Tzuang
- Source: Electronics Letters, Volume 28, Issue 2, p. 192 –193
- DOI: 10.1049/el:19920119
- Type: Article
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The effect of finite substrate width on the higher-order mode generation of an electrically shielded microstrip is investigated. By employing the full-wave mixed potential modematching method the microstrip on a finite-width substrate can be accurately analysed. The dispersion characteristics of microstrip on two different substrate widths were compared in the frequency range of interest. The results indicated that the use of conventional three-dimensional simulators assuming homogeneous layered (stratified) multi-dielectric substrates may not work well above the first cutoff frequency of microstrip on a finite-width substrate.
Slot-coupled excitation of microstrip dipole antennas
- Author(s): A. Ittipiboon ; D. Roscoe ; M. Cuhaci ; Y.M.M. Antar
- Source: Electronics Letters, Volume 28, Issue 2, p. 193 –194
- DOI: 10.1049/el:19920120
- Type: Article
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The slot-coupled method is proposed as an alternative to the popular electromagnetically coupled technique (EMC) for feeding microstrip dipole antennas. This Letter describes the basic design procedure and some key advantages of this method over EMC. Experimental results confirm the effective and practical performance of the proposed structure.
Modelling the capacitance of microstrip line using spice
- Author(s): T. Vu Dinh ; B. Cabon ; J. Chilo
- Source: Electronics Letters, Volume 28, Issue 2, p. 194 –196
- DOI: 10.1049/el:19920121
- Type: Article
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An original concept for calculating the line capacitance of a microstrip line is presented. An equivalent circuit is created and analysed using the electrical software SPICE; the line capacitance on the inhomogeneous lossless dielectrical layer is deduced by using one impedance–admittance transformation. The numerical results agree well with those of other standard published methods.
Optical amplifier dynamic range improvement with all-fibre optical image-rejection mixer in 2.5 Gbit/s CP-FSK system experiment
- Author(s): B.F. Jergensen and C.J. Mahon
- Source: Electronics Letters, Volume 28, Issue 2, p. 196 –197
- DOI: 10.1049/el:19920122
- Type: Article
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The dynamic range of an optical amplifier is increased by 2.6 dB in a 2.5 Gbit/s CP-FSK system experiment. This is achieved by reducing the local oscillator spontaneous beat noise contribution in the heterodyne receiver correspondingly with an all-fibre optical image rejection mixer.
120 W CW output power from monolithic AlGaAs (800 nm) laser diode array mounted on diamond heatsink
- Author(s): M. Sakamoto ; J.G. Endriz ; D.R. Scifres
- Source: Electronics Letters, Volume 28, Issue 2, p. 197 –199
- DOI: 10.1049/el:19920123
- Type: Article
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Continuous-wave output power levels of 120 W at 2°C and 100 W at room temperature are reported from 1cm wide monolithic AlGaAs (800 nm) laser diode arrays with a 7200 μm total aperture width by using diamond heatsinks. Additionally, 25 W CW operation up to 90°C has been demonstrated.
Simple fast median filtering algorithm, with application to corner detection
- Author(s): E.R. Davies
- Source: Electronics Letters, Volume 28, Issue 2, p. 199 –201
- DOI: 10.1049/el:19920124
- Type: Article
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The Letter studies the speed of operaton of median filtering algorithms. An iterative approach is investigated, and then simplified to take the local neighbourhood centre pixel as a starting approximation. Overall speedup factors of 2–4 are obtained. The method is useful when the ‘running median’ technique cannot be used, as for ‘skimmed’ median-based corner detectors.
Amplified fibre delay line with 27 000 recirculations
- Author(s): J.T. Kringlebotn ; P.R. Morkel ; C.N. Pannell ; D.N. Payne ; R.I. Laming
- Source: Electronics Letters, Volume 28, Issue 2, p. 201 –202
- DOI: 10.1049/el:19920125
- Type: Article
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An active recirculating-ring fibre delay line with 27 000 recirculations is reported, corresponding to a feedback coefficient of 0.99996 or a finesse as high as 150 000. This is the highest value ever reported and indicates the potential for long optical storage times in such devices.
Zeros of linear phase FIR filter with piecewise constant frequency response
- Author(s): Y. Lian and Y.C. Lim
- Source: Electronics Letters, Volume 28, Issue 2, p. 203 –204
- DOI: 10.1049/el:19920126
- Type: Article
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The evaluation of the zeros of a high order FIR filter using the successive search and deflate technique suffers from very severe numerical problems. Such methods often fail if the filter length is larger than 100 even if double precision arithmetic is used. A new robust method is presented for evaluating the zeros of a high order FIR filter.
Fused polished singlemode fibre couplers
- Author(s): C.V. Cryan and C.D. Hussey
- Source: Electronics Letters, Volume 28, Issue 2, p. 204 –205
- DOI: 10.1049/el:19920127
- Type: Article
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The successful fabrication of stable low-loss fused polished couplers with standard singlemode fibres is reported for the first time. The ease of fabrication is comparable to that of tapered couplers and should lead to low-cost devices.
Evaluating ASP computer for vision tasks using Abingdon Cross benchmark
- Author(s): G. Tambouratzis and A. Krikelis
- Source: Electronics Letters, Volume 28, Issue 2, p. 205 –207
- DOI: 10.1049/el:19920128
- Type: Article
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The suitability of the ASP computer for image processing tasks has been evaluated by implementing the Abingdon Cross benchmark. The results obtained indicatet that the ASP is among the fastes and most cost effective processors available.
Electrical loss mechanisms in travelling wave LiNbO3 optical modulators
- Author(s): G.K. Gopalakrishnan ; W.K. Burns ; C.H. Bulmer
- Source: Electronics Letters, Volume 28, Issue 2, p. 207 –208
- DOI: 10.1049/el:19920129
- Type: Article
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Anomalous electrical losses in travelling wave LiNbO3 optical modulators are attributes of phase matched mode coupling between the coplanar waveguide mode and off-axis substrate modes. Experimental results support the model.
Interpolation using Hartley transform
- Author(s): D. Liu ; D. Wang ; Z. Wang
- Source: Electronics Letters, Volume 28, Issue 2, p. 209 –210
- DOI: 10.1049/el:19920130
- Type: Article
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The revised interpolation method for a 1-D signal via the fast Hartley transform (FHT) is presented and a new interpolation algorithm for a 2-D signal by using the 1-D FHT is suggested. Results show that the proposed algorithm is superior to the FFT method both in accuracy and in computational time for interpolating discrete bandlimited 2-D signals.
Erratum: New prediction method of cloud attenuation
- Author(s): E. Salonen and S. Uppala
- Source: Electronics Letters, Volume 28, Issue 2, page: 210 –210
- DOI: 10.1049/el:19920131
- Type: Article
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