Showing papers in "Electronics Letters in 1999"
TL;DR: Using this joint space-time approach, spectral efficiencies ranging from 20-40 bit/s/Hz have been demonstrated in the laboratory under flat fading conditions at indoor fading rates.
Abstract: The signal detection algorithm of the vertical BLAST (Bell Laboratories Layered Space-Time) wireless communications architecture is briefly described. Using this joint space-time approach, spectral efficiencies ranging from 20-40 bit/s/Hz have been demonstrated in the laboratory under flat fading conditions at indoor fading rates. Early results are presented.
1,791 citations
TL;DR: A novel method for visualising the convergence behaviour of iterative decoding schemes is proposed, which describes the flow of extrinsic information through the soft in/soft out decoder.
Abstract: A novel method for visualising the convergence behaviour of iterative decoding schemes is proposed. Each constituent decoder is represented by a mutual information transfer characteristic which describes the flow of extrinsic information through the soft in/soft out decoder. The exchange of extrinsic information between constituent decoders is plotted in an extrinsic information transfer chart. The concepts are illustrated for an iterative demapping and decoding scheme.
616 citations
TL;DR: In this paper, the lowest room-temperature threshold current density, 26 A/cm/sup 2 ), of any semiconductor diode laser was reported for a quantum dot device with a single InAs dot layer contained within a strained In/sub 0.85/As quantum well.
Abstract: The lowest room-temperature threshold current density, 26 A/cm/sup 2/, of any semiconductor diode lasers is reported for a quantum dot device with a single InAs dot layer contained within a strained In/sub 0.15/Ga/sub 0.85/As quantum well. The lasers are epitaxially grown on a GaAs substrate, and the emission wavelength is 1.25 /spl mu/m.
469 citations
TL;DR: A class of binary sequences with the defined ZCZ property can be used in spread spectrum systems and CDMA systems to eliminate multipath and cochannel interference.
Abstract: Based on the idea of the zero correlation zone (ZCZ), a class of binary sequences with the defined ZCZ property is presented. The ZCZ spreading code sequences can be used in spread spectrum systems and CDMA systems to eliminate multipath and cochannel interference.
345 citations
TL;DR: In this paper, the light propagation in 2D photonic crystal waveguides with bends was observed, which were composed of densely-packed holes formed in a GaInAsP thin film.
Abstract: We observed the light propagation in 2-D photonic crystal waveguides with bends, which were composed of densely-packed holes formed in a GaInAsP thin film. Wavelength and polarization dependence of propagation characteristics was observed at λ = 1.47 - 1.60μm.
299 citations
TL;DR: In this paper, a comprehensive numerical and experimental study of 40 Gbit/s RZ transmission is presented which reveals two new forms of nonlinear interactions that limit the speed of high-speed systems.
Abstract: A comprehensive numerical and experimental study of 40 Gbit/s RZ transmission is presented which reveals two new forms of nonlinear interactions that limit the speed of high-speed systems. Both limitations originate from nonlinear interactions among neighbouring bits. The first interaction involves cross-phase modulation and leads to timing fluctuations while the second interaction originates from four-wave mixing and leads to the creation of shadow pulses.
279 citations
TL;DR: Montgomery's modular multiplication algorithm is commonly used in implementations of the RSA cryptosystem and it has been observed that there is no need for extra cleaning up at the end of an exponentiation if the method is correctly set up.
Abstract: Montgomery's modular multiplication algorithm is commonly used in implementations of the RSA cryptosystem. It has been observed that there is no need for extra cleaning up at the end of an exponentiation if the method is correctly set up.
274 citations
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TL;DR: In this paper, a Yb-doped double-clad fiber laser with a record average power output of >110 W CW in a single spatial mode beam was demonstrated and the conversion efficiency was /spl sim/58% with respect to the incident pump power.
Abstract: The authors demonstrate a Yb-doped double-clad fibre laser with a record average power output of >110 W CW in a single spatial mode beam. The conversion efficiency is /spl sim/58% with respect to the incident pump power.
214 citations
TL;DR: In this paper, an ultra-miniature duplexer (5 × 8 × 2.2 mm3) consisting of two FBAR filters and nine passive components operating at 1900 MHz is described.
Abstract: An ultra-miniature duplexer (5 × 8 × 2.2 mm3) consisting of two FBAR filters and nine passive components operating at 1900 MHz is described. The minimum insertion loss for the Tx and Rx bands is better than –3 dB. Isolation between the Tx and Rx ports exceeds 50 dB over most of the Tx band and 46 dB in the Rx band. The FBAR filters handle up to 2 W throughout the passband.
204 citations
TL;DR: In this paper, a 12-wavelength-channel WDM pumping unit with high-power GRINSCH strained layer MQW BH laser diode modules was used to achieve gain flatness less than /spl plusmn/0.5 dB, which was achieved through the asymmetric channel allocation of the pump and without the use of any gain equalisation filters.
Abstract: 100 nm bandwidth Raman amplifiers have been realised using a 12-wavelength-channel WDM pumping unit comprising high-power GRINSCH strained layer MQW BH laser diode modules. The gain flatness is less than /spl plusmn/0.5 dB, which is achieved through the asymmetric channel allocation of the pump and without the use of any gain equalisation filters.
198 citations
TL;DR: In this paper, the overlap of the optical mode in a holey fiber with the air holes is calculated using a vector modal decomposition approach, and it is shown that a significant fraction of the modal power can be made to overlap with the holes.
Abstract: The overlap of the optical mode in a holey fibre with the air holes is calculated for the first time. This is achieved using a vector modal decomposition approach. It is shown that a significant fraction of the modal power can be made to overlap with the holes, which suggests that these unusual fibres may be useful as evanescent field devices.
TL;DR: A Gabor filter-based method for directly extracting fingerprint features from grey-level images without pre-processing is introduced and shows that the recognition rate of the k-nearest neighbour classifier using the proposed Gabor Filter-based features is 97.2%.
Abstract: A Gabor filter-based method for directly extracting fingerprint features from grey-level images without pre-processing is introduced. The proposed method is more efficient and suitable than conventional methods for a small-scale fingerprint recognition system. Experimental results show that the recognition rate of the k-nearest neighbour classifier using the proposed Gabor filter-based features is 97.2%.
TL;DR: In this paper, a 3 Tbit/s (160 Gbps/s × 19 channels) optical signal has been successfully transmitted over 40 km of dispersion-shifted fibre Low noise supercontinuum signal pulse sources and 70 nm bandwidth tellurite-based optical amplifiers are used for 3 T bit/s signal generation and amplification.
Abstract: A 3 Tbit/s (160 Gbit/s × 19 channels) optical signal has been successfully transmitted over 40 km of dispersion-shifted fibre Low noise supercontinuum signal pulse sources and 70 nm bandwidth tellurite-based optical amplifiers are used for 3 Tbit/s signal generation and amplification
TL;DR: In this article, the authors applied optimized low-temperature metal organic vapour phase epitaxy (MOVPE) using the group V sources 1,1-dimethylhydrazine (UDMHy) in combination with tertiarybutylarsine (TBAs) to achieve record low threshold current densities of 0.18 and 0.16 W/A per facet, respectively, for 800 µm long broad area lasers emitting at 1.28 and 1.38 µm, respectively.
Abstract: (GaIn)(NAs)/GaAs single quantum well (SQW) broad area lasers with emission wavelengths at 1.28 and 1.38 µm at room temperature on GaAs substrates have been realised by applying optimised low-temperature metal organic vapour phase epitaxy (MOVPE) using the group V sources 1,1-dimethylhydrazine (UDMHy) in combination with tertiarybutylarsine (TBAs). Record-low threshold current densities of 0.8 and 2.2 kA/cm2, together with high differential efficiencies of 0.18 and 0.16 W/A per facet, are obtained for 800 µm long broad area lasers emitting at 1.28 and 1.38 µm, respectively.
TL;DR: In this paper, the authors report measurements of group velocity dispersion in photonic crystal fiber using low coherence techniques and confirm theoretical predictions that photonic fiber, unlike conventional step-index fiber, can exhibit anomalous waveguide dispersion while remaining singlemode.
Abstract: The authors report measurements of group velocity dispersion in photonic crystal fibre using low coherence techniques. The results confirm theoretical predictions that photonic crystal fibre, unlike conventional step-index fibre, can exhibit anomalous waveguide dispersion while remaining singlemode. This allows the design of singlemode fibres with zero dispersion points at wavelengths much shorter than is possible in standard fibre.
TL;DR: In this paper, a chirped optical supercontinuum is used to map absorption spectra into temporal waveforms and a modelocked fiber laser is used as the source of broadband radiation and a sampling oscilloscope for spectral measurement.
Abstract: A chirped optical supercontinuum is used to map absorption spectra into temporal waveforms. Time-domain spectral measurement of acetylene is demonstrated using a modelocked fibre laser as the source of broadband radiation and a sampling oscilloscope for spectral measurement.
TL;DR: In this paper, a planar monopole antenna with a shorting pin was proposed to reduce the size of the antenna by /spl sim/50% compared with an equivalent planar antenna without a short-pin.
Abstract: When a shorting pin is added to the planar monopole antenna, an additional mode is excited below the fundamental mode. By optimising the dimensions. A compact wideband antenna can be constructed. The size reduction achievable for this antenna is /spl sim/50% compared with an equivalent planar monopole without a shorting pin. Owing to its compact size and wideband performance, this antenna is suitable for use in existing and future mobile communication terminals.
TL;DR: In this paper, the authors demonstrate +11 dBm-per-channel 320 Gbit/s (8/spl times/40 Gbps) transmission over a 367 km zero-dispersion-flattened transmission line with 120 km repeater spacing using a nonlinearity-tolerant carrier-suppressed return-to-zero format.
Abstract: The authors demonstrate +11 dBm-per-channel 320 Gbit/s (8/spl times/ 40 Gbit/s) WDM transmission over a 367 km zero-dispersion-flattened transmission line with 120 km repeater spacing using a nonlinearity-tolerant carrier-suppressed return-to-zero format.
TL;DR: In this paper, a switch configuration to be used at the input of switched op amp circuits is introduced, which is an extension of the gate-source bootstrapping technique such that rail-to-rail operation of the input switch becomes possible.
Abstract: A switch configuration to be used at the input of switched op amp circuits is introduced. The circuit is an extension of the gate-source bootstrapping technique such that rail-to-rail operation of the input switch becomes possible. Simulations show the usefulness of the proposed circuit down to 0.9 V.
TL;DR: A semi-random approach to low density parity check code design is shown to achieve essentially the same performance as an existing method, but with considerably reduced complexity.
Abstract: A semi-random approach to low density parity check code design is shown to achieve essentially the same performance as an existing method, but with considerably reduced complexity.
TL;DR: In this article, a second probe feed was introduced to suppress the unwanted radiation from the probe feed of a microstrip patch, which can contribute significantly to the cross-polarisation radiation or to pattern distortion.
Abstract: The radiation from the probe feed of a microstrip patch can contribute significantly to the cross-polarisation radiation or to pattern distortion, especially if the patch is fabricated on a relatively thick, low-permittivity substrate. By introducing a second probe, which is fed out of phase with the original probe, this unwanted radiation can effectively be suppressed. To demonstrate this technique, two L-band patches were fabricated, one with and one without the extra probe. The dual probe-fed patch produced more symmetrical radiation patterns and had a reduction in the peak cross-polarisation level of nearly 20 dB. The unwanted radiation is effectively suppressed over a bandwidth of >10%.
TL;DR: Tests with car images travelling on the road and at the entrance of a car park showed extraction rates of 99 and 97.5%, respectively, suggesting that the proposed method works well with real-world situations.
Abstract: The authors present a method for locating car license plates using neural networks. Neural networks are used as filters for analysing small windows of an image and deciding whether each window contains a license plate. A post-processor combines these filtered images and gives the final location of the license plates. The method offers robustness when dealing with noisy images. Tests with car images travelling on the road and at the entrance of a car park showed extraction rates of 99 and 97.5%, respectively. These results suggest that the proposed method works well with real-world situations.
TL;DR: In this paper, a family of chaotic maps is presented which is able to generate sequences with exponential auto-correlation function with alternating signs, and the resulting DS-CDMA system is an extremely good approximation of the optimum achievable system.
Abstract: The classical estimation of co-channel interference in asynchronous direct sequence-code division multiple access (DS-CDMA) systems, obtained for a conventional receiver under the standard Gaussian approximation (SGA), is analytically minimised with respect to the auto-correlation function of spreading sequences. The optimum auto-correlation function is found to be real, with alternating signs, and extremely closely follows an exponential trend. A family of chaotic maps is presented which is able to generate sequences with exponential auto-correlation function with alternating signs. The resulting DS-CDMA system is an extremely good approximation of the optimum achievable system.
TL;DR: In this paper, the discrepancy between the measured microwave power performance of GaN MODFETs and the prediction based on the DC characteristics is caused by the trapping of mobile electrons in the channel under large-signal modulation.
Abstract: It is shown that the discrepancy between the measured microwave power performance of GaN MODFETs and the prediction based on the DC characteristics is caused by the trapping of mobile electrons in the channel under large-signal modulation. This phenomenon manifests itself in the compression of the drain current. The strong dependence of the level of current compression on the gate bias voltage indicates that carrier trapping takes place in the AlGaN barrier or at the surface of the device.
TL;DR: It is shown that quaternary codes can be advantageous, both from performance and complexity standpoints, but that higher-order codes may not bring further improvement.
Abstract: The authors consider the use of non-binary convolutional codes in turbo coding. It is shown that quaternary codes can be advantageous, both from performance and complexity standpoints, but that higher-order codes may not bring further improvement.
TL;DR: In this article, anisotropic changes of electro-optic coefficients, r/sub 33/ and r/ sub 13/ have been found between the stoichiometric and congruent LiNbO/sub 3/ crystals.
Abstract: Comparison of the electro-optic (EO) effect between stoichiometric and congruent lithium niobate (LiNbO/sub 3/) crystals has been investigated using the Mach-Zehnder interferometer at 0.633 /spl mu/m wavelength. Anisotropic changes of EO coefficients, r/sub 33/ and r/sub 13/ have been found between the stoichiometric and congruent LiNbO/sub 3/ crystals. The measured r/sub 33/ value in the stoichiometric LiNbO/sub 3/ is at least 20% larger than that of LiNbO/sub 3/ with congruent composition whereas the r/sub 13/, coefficient of stoichiometric LiNbO/sub 3/ is the same as that of congruent LiNbO/sub 3/.
TL;DR: In this article, a new optical polarisation mode dispersion compensator is proposed based on the dynamic maximisation of the degree of polarisation, which requires no variable differential group delay and has been experimentally validated.
Abstract: A new optical polarisation mode dispersion compensator is proposed which is based on the dynamic maximisation of the degree of polarisation. It requires no variable differential group delay and has been experimentally validated.
TL;DR: In this paper, low threshold current density (Jth = 65 A/cm2) operation near 1.3 µm at room temperature (RT) was realized for lasers using InAs/InGaAs/GaAs quantum dots (QDs).
Abstract: Low threshold current density (Jth = 65 A/cm2) operation near 1.3 µm at room temperature (RT) is realised for lasers using InAs/InGaAs/GaAs quantum dots (QDs). The lasing occurs via the QD ground state for cavity length L > 1 mm. The differential efficiency is 40% and internal losses are 1.5 cm–1. The characteristic temperature near RT is 160 K.
TL;DR: A novel method based on the evaluation of amplitude histograms generated by asynchronous sampling is found to detect signal degradations due to noise, crosstalk or pulse distortion with a high sensitivity.
Abstract: A novel method for performance monitoring of transparent optical systems, based on the evaluation of amplitude histograms generated by asynchronous sampling, is investigated experimentally. The method was found to detect signal degradations due to noise, crosstalk or pulse distortion with a high sensitivity.
TL;DR: In this article, a lossy dielectric layer was incorporated in a microwave AlGaN/GaN MODFET power device to enable an interpretation of the RF power compression observed in these devices.
Abstract: Microwave AlGaN/GaN MODFET power devices have been analysed with respect to their frequency dispersion in terms of transconductance, gate capacitance and large signal output current swing. A electrical equivalent circuit model consistent with all experimental findings, based on the incorporation of a lossy dielectric layer, is presented. It may also enable an interpretation to be made of the RF power compression observed in these devices.