Showing papers in "Electronics Letters in 1997"
TL;DR: In this paper, the authors proposed a very effective and flexible peak power reduction scheme for orthogonal frequency division multiplexing (OFDM) with almost vanishing redundancy, which works with arbitrary numbers of subcarriers and unconstrained signal sets.
Abstract: The authors propose a very effective and flexible peak power reduction scheme for orthogonal frequency division multiplexing (OFDM) with almost vanishing redundancy. This new method works with arbitrary numbers of subcarriers and unconstrained signal sets. The core of the proposal is to combine partial transmit sequences (PTS) to minimise the peak-to-average power ratio distortion.
1,400 citations
TL;DR: In this article, a method for generating an optical carrier with single sideband modulation using a dual-electrode Mach-Zehnder modulator biased at quadrature is presented.
Abstract: The authors present a novel method for generating an optical carrier with single sideband modulation using a dual-electrode Mach-Zehnder modulator biased at quadrature. It is proposed and demonstrated experimentally that this simple technique can be used to reduce dispersion power penalties in fibre-radio systems.
464 citations
TL;DR: Tree-structured generation of orthogonal spreading codes with different lengths is presented for Orthogonal multiplexing of forward-link code-channels of different data rates in direct sequence code division multiple access DS-CDMA mobile radio.
Abstract: Tree-structured generation of orthogonal spreading codes with different lengths is presented for orthogonal multiplexing of forward-link code-channels of different data rates in direct sequence code division multiple access DS-CDMA mobile radio. The bit error rate performance under a multi-user environment suffering multipath Rayleigh fading is evaluated by computer simulation.
407 citations
TL;DR: In this paper, the piezoelectric charge density at (0001) AlGaN/GaN interfaces is estimated for both MBE and MOCVD structures on sapphire and SiC substrate.
Abstract: New estimates of the piezoelectric charge density at (0001) AlGaN/GaN interfaces are provided. Undoped HFET structures grown by both MBE and MOCVD, on sapphire and SiC substrates, exhibit electron densities of /spl sim/5/spl times/10/sup 13/ cm/sup -2/ x/sub Al/ (where x/sub Al/ is the aluminium mol fraction in the AlGaN), which can be attributed to piezoelectric effects. These have a significant influence on the design and behaviour of III-V nitride HFETs.
314 citations
TL;DR: Er3+-doped tellurite singlemode fiber is fabricated and signal amplification and laser oscillation are demonstrated for the first time in this article, where a small signal gain of 16 dB at 1560 nm is obtained for a pump power of 130 mW at 978 nm.
Abstract: Er3+-doped tellurite singlemode fibre is fabricated and signal amplification and laser oscillation are demonstrated for the first time. A small-signal gain of 16 dB at 1560 nm is obtained for a pump power of 130 mW at 978 nm. A laser oscillation is observed with a threshold pump power of 120 mW at 978 nm and a slope efficiency of 0.65% using this fibre.
294 citations
TL;DR: In this paper, an electromagnetic micro-generator based on a planar pick-up coil and flexible polyimide membrane of diameter 2 mm with attached magnet is described, where the membrane displacement characteristics become nonlinear due to the spring stiffening effect, limiting the maximum generated power to 0.3 /spl mu/W.
Abstract: An electromagnetic micro-generator is described, based on a planar pick-up coil and flexible polyimide membrane of diameter 2 mm with attached magnet. During large amplitudes of vibration of the device, the membrane displacement characteristics become nonlinear due to the spring stiffening effect, limiting the maximum generated power to 0.3 /spl mu/W.
265 citations
TL;DR: In this article, the authors discovered that there are stable nonlinear transmission pulses for periodically dispersion managed systems where the path average dispersion may be either anomalous, zero, or even normal.
Abstract: The authors have discovered from numerical modelling that there are stable nonlinear transmission pulses for periodically dispersion managed systems where the path average dispersion may be either anomalous, zero, or even normal.
251 citations
TL;DR: From extensive 2D channel measurements it is found that the shape of the power azimuth spectrum at the base station in outdoor environments is accurately described by a truncated Laplacian function in both rural and urban environments.
Abstract: From extensive 2D channel measurements it is found that the shape of the power azimuth spectrum at the base station in outdoor environments is accurately described by a truncated Laplacian function in both rural and urban environments.
227 citations
TL;DR: In this article, a broadband and gain-flattened Er/sup 3+/-doped fiber amplifier (EDFA) with a flat amplification bandwidth of 54 nm for wavelength division multiplexed signals was constructed.
Abstract: The authors construct a broadband and gain-flattened Er/sup 3+/-doped fibre amplifier (EDFA) with a flat amplification bandwidth of 54 nm for wavelength division multiplexed signals This was achieved by employing a 158 /spl mu/m-band EDFA and a 155 /spl mu/m-band EDFA in a parallel configuration Excellent flat amplification characteristics were obtained for 1530-1560 nm and 1576-1600 nm signal wavelength regions, with a gain non-uniformity of <17 dB and a signal gain of 30 dB
210 citations
TL;DR: The scheme solves the notorious problem of power control in OFDM systems by maintaining a peak-to-mean envelope power ratio of at most 3 dB while allowing simple encoding and decoding at high code rates for binary, quaternary or higher-phase signalling together with good error correction.
Abstract: A coding scheme for OFDM transmission is proposed, exploiting a previously unrecognised connection between pairs of Golay complementary sequences and second-order Reed-Muller codes. The scheme solves the notorious problem of power control in OFDM systems by maintaining a peak-to-mean envelope power ratio of at most 3 dB while allowing simple encoding and decoding at high code rates for binary, quaternary or higher-phase signalling together with good error correction.
207 citations
TL;DR: In this article, a miniature aperture-coupled microstrip antenna of very high permittivity designed at 1.66 GHz is described, where superstrates of appropriate thickness are added on the substrate for gain enhancement.
Abstract: A miniature aperture-coupled microstrip antenna of very high permittivity designed at 1.66 GHz is described. Superstrates of appropriate thickness are added on the substrate for gain enhancement. Its size is dramatically reduced and the electrical performance remains almost the same as compared with the conventional microstrip antenna of low dielectric constant. Experimental data for the return loss, radiation pattern and measured antenna gain are presented to validate the design.
TL;DR: In this paper, a single sideband optical modulation at millimetre-wave frequencies using a fibre Bragg grating eliminates the dispersion-induced penalty over modulation frequency and fibre length.
Abstract: Dispersion causes a power penalty at certain fibre distances and frequencies in conventional millimetre-wave intensity modulation. Single sideband optical modulation at millimetre-wave frequencies using a fibre Bragg grating eliminates the dispersion-induced penalty over modulation frequency and fibre length.
TL;DR: In this paper, the authors investigated the dispersion design in a single-mode fiber for generating a supercontinuum with a flatly broadened spectrum, and found that group velocity dispersion is a convex function with two zero-dispersion wavelengths and also that it decreases with fibre length.
Abstract: Dispersion design in a single-mode fibre is investigated experimentally and numerically for generating a supercontinuum with a flatly broadened spectrum. It is found to be important both that group velocity dispersion is a convex function with two zero-dispersion wavelengths and also that it decreases with fibre length. A calculated spectrum explains well that obtained experimentally. The mechanism of the spectral evolution of supercontinuum is examined.
TL;DR: In this article, GaAs-based 850 nm emission wavelength VCSELs are fabricated using solid source MBE and carbon p-type doping, achieving an operating range from -80/spl deg/C up to +185/spl/C, and threshold currents below 500 /spl mu/A.
Abstract: Vertical-cavity surface-emitting lasers with reduced effective index guiding of the optical wave show a record performance. GaAs based 850 nm emission wavelength VCSELs are fabricated using solid source MBE and carbon p-type doping. Depending on device design maximum room temperature conversion efficiencies of 57%, an operating range from -80/spl deg/C up to +185/spl deg/C, and threshold currents below 500 /spl mu/A from -40 to +80/spl deg/C have been obtained.
TL;DR: Wavelength division multiplexing is used to add a secure quantum key distribution channel to a conventional 1.2 Gbit/s data channel operating over 28 km of installed fibre in BT's London and East Anglia multiservice network testbed (LEANET).
Abstract: Wavelength division multiplexing (WDM) is used to add a secure quantum key distribution channel (/spl lambda/=1300 nm) to a conventional 1.2 Gbit/s data channel (/spl lambda//spl sim/1550 nm) operating over 28 km of installed fibre in BT's London and East Anglia multiservice network testbed (LEANET). Error-free operation of the data channel is demonstrated with no degradation of the quantum channel performance.
TL;DR: In this article, the authors have optimized MBE-grown GaAs VCSELs emitting at a wavelength of 840 nm for maximum singlemode output power of 4.8 mW and a butt-coupling efficiency into singlemode fibre of > 80%.
Abstract: The authors have optimised MBE-grown GaAs VCSELs emitting at a wavelength of 840 nm for maximum singlemode output power. Devices of 3.5 µm diameter show a record high singlemode CW output power of 4.8 mW and a butt-coupling efficiency into singlemode fibre of > 80%.
TL;DR: In this paper, the fabrication and characterisation of AlGaN/GaN HEMTs grown on SiC substrates are described, which have a transconductance of 70 mS/mm and a gate breakdown voltage in excess of 100V.
Abstract: The fabrication and characterisation of AlGaN/GaN HEMTs grown on SiC substrates are described. These devices have a transconductance of 70 mS/mm and a gate breakdown voltage in excess of 100V. The HEMTs have a hard pinch-off with nearly ideal subthreshold characteristics. An f/sub T/ of 6 GHz and an f/sub max/ of 11 GHz were measured for 1 /spl mu/m gate length devices.
TL;DR: In this article, a temperature dependent channel wavelength shift in a silica-based arrayed-waveguide grating multiplexer was successfully suppressed from 0.95 to 0.05 nm in the 0-85/spl deg/C temperature range, which can be used in practical WDM systems without the need for temperature control.
Abstract: A temperature dependent channel wavelength shift in a silica-based arrayed-waveguide grating multiplexer is successfully suppressed from 0.95 to 0.05 nm in the 0-85/spl deg/C temperature range, which means that it can be used in practical WDM systems without the need for temperature control.
TL;DR: In this article, a two-band erbium-doped silica fiber amplifier with a record optical bandwidth of 80 nm is presented, where the two bands share a common first gain section and have distinct second gain sections.
Abstract: The authors demonstrate a two band architecture for an ultrawideband erbium-doped silica fibre amplifier with a record optical bandwidth of 80 nm. To obtain a low noise figure and high output power, the two bands share a common first gain section and have distinct second gain sections.
TL;DR: In this article, a chip-resistor-loaded rectangular microstrip antenna fed using a probe feed or an inset microstrip-line feed is presented. But the advantages of small antenna size and wide antenna bandwidth, compared to a conventional rectangular micro-strip antenna, are not discussed.
Abstract: Designs of a chip-resistor-loaded rectangular microstrip antenna fed using a probe feed or an inset microstrip-line feed are presented. These antenna designs have the advantages of small antenna size and wide antenna bandwidth, compared to a conventional rectangular microstrip antenna. Details of the experimental results are given.
TL;DR: In this article, the design of a single-feed small microstrip antenna with circular polarisation (CP) radiation is described, which is achieved by cutting slits in the square patch and adjusting the lengths of the slits.
Abstract: The design of a single-feed small microstrip antenna with circular polarisation (CP) radiation is described. This design is achieved by cutting slits in the square patch and. By adjusting the lengths of the slits, the microstrip antenna can perform CP radiation with a reduced patch size at a fixed operating frequency. This design also provides a wide CP bandwidth and relaxed fabrication tolerances.
TL;DR: In this paper, a simple technique for measuring optical fiber dispersion (or pulse spectrum if fibre dispersion is known) is demonstrated, where ultra-short pulses are linearly dispersed in the fibre under test, thus mapping their spectrum to the time domain.
Abstract: A simple technique for measuring optical fibre dispersion (or pulse spectrum if fibre dispersion is known) is demonstrated. Ultra-short pulses are linearly dispersed in the fibre under test, thus mapping their spectrum to the time domain. The delay between two spikes in the dispersed pulse's temporal profile, corresponding to two spectral spikes, accurately gives the dispersion.
TL;DR: In this article, the authors presented properties of a circular patch antenna with radiation characteristics similar to those of a resonant monopole, which is easy to match to a 50 /spl Omega/ line.
Abstract: Properties of a circular patch antenna with radiation characteristics similar to those of a resonant monopole are presented. The TM/sub 01/ mode excited patch on a small ground plane radiates a null on boresight and is easy to match to a 50 /spl Omega/ line. Applications include mobile vehicle applications and wireless LANs.
TL;DR: In this article, a completely passive radio access point for future high capacity short range wireless networks is proposed based on a single component, an unbiased electroabsorption modulator, which acts as a passive transceiver at the remote side of an analogue optical link.
Abstract: A completely passive radio access point for future high capacity short range wireless networks has been demonstrated. This concept is based on a single component, an unbiased electroabsorption modulator, which acts as a passive transceiver at the remote side of an analogue optical link.
TL;DR: In this paper, a triangular microstrip antenna with a U-shaped slot was proposed and the performance of the antenna was evaluated with a foam substrate of thickness /spl sim/0.08 /spl lambda/sub 0.
Abstract: The broadband design of a triangular microstrip antenna with a U-shaped slot is demonstrated. With a foam substrate of thickness /spl sim/0.08 /spl lambda//sub 0/, a slotted triangular microstrip antenna with an operating bandwidth of /spl sim/18% is obtained, which is /spl sim/1.8 times that of a corresponding simple triangular patch antenna. Details of the antenna design and experimental results are presented.
TL;DR: In this article, an increased resonance frequency and reduced damping of the resonance peak leading to a record high modulation bandwidth of 30GHz were observed in 1.55 mm InGaAsP DBR lasers.
Abstract: An increased resonance frequency and reduced damping of theresonance peak leading to a record high modulation bandwidth of30GHz were observed in 1.55 mm InGaAsP DBR lasers. Theseresults are attributed to the mechanism of detuned loading.
TL;DR: In this paper, the characteristics of a single-feed dual-frequency compact microstrip antenna with a shorting pin are studied experimentally, which can provide a high frequency ratio of > 3.0 between the two operating frequencies.
Abstract: The characteristics of a single-feed dual-frequency compact microstrip antenna with a shorting pin are studied experimentally. Besides the compactness of the antenna, this dual-frequency design can provide a high frequency ratio of >3.0 between the two operating frequencies. Typical experimental results of the proposed antenna are presented and discussed.
TL;DR: In this paper, power transients arising from cross-saturation in erbium-doped fiber amplifiers (EDFAs) are reported to be 1 dB in <3 /spl mu/s in a chain of five EDFAs.
Abstract: Power transients arising from cross-saturation in erbium-doped fibre amplifiers (EDFAs) are generally thought to be slower than 100 /spl mu/s due to the slow gain dynamics. This is a key advantage of EDFAs. The authors report on power transients of 1 dB in <3 /spl mu/s in a chain of five EDFAs. These fast power variations result from the collective behaviour of the amplifier chain.
TL;DR: In this paper, an electrostatically controlled cantilever apparatus for continuous tuning of the resonance wavelength of a Fabry-Perot cavity is disclosed, where a resonant cavity is formed between two distributed Bragg reflector (DBR) mirrors each composed of multiple DBR layers.
Abstract: An electrostatically controlled cantilever apparatus for continuous tuning of the resonance wavelength of a Fabry-Perot cavity is disclosed. A resonant cavity is formed between two distributed Bragg reflector (DBR) mirrors each composed of multiple DBR layers. One such layer is replaced with a layer which has been fully oxidized except for a small aperture. This layer provides both optical and current confinement which allows for low threshold currents and high output power.
TL;DR: A new neural-network adaptive algorithm is proposed for performing extraction of independent source signals from a linear mixture of them with specified order according to their stochastic properties, namely, in decreasing order of absolute normalised kurtosis.
Abstract: A new neural-network adaptive algorithm is proposed for performing extraction of independent source signals from a linear mixture of them. Using a suitable nonlinear Hebbian learning rule and a new deflation technique, the developed neural network is able to extract the source signals (sub-Gaussian and/or super-Gaussian) one-by-one with specified order according to their stochastic properties, namely, in decreasing order of absolute normalised kurtosis. The validity and performance of the algorithm are confirmed through extensive computer simulations.