Showing papers in "Electronics Letters in 2006"
TL;DR: A new technique for using orthogonal frequency division multiplexing (OFDM) in optical systems is presented, derived from a bipolar OFDM waveform by setting the negative values to zero.
Abstract: A new technique for using orthogonal frequency division multiplexing (OFDM) in optical systems is presented. Clipped OFDM is derived from a bipolar OFDM waveform by setting the negative values to zero. It has an optical efficiency 8 dB better than DC biased OFDM. If only the odd OFDM subcarriers are modulated, the clipping noise is orthogonal to the wanted signal.
787 citations
TL;DR: In this article, a coherent optical orthogonal frequency division multiplexing (OFDM) was proposed to combat dispersion in optical media, and it was shown that optical-signal-to-noise ratio penalty at 10 Gbit/s is maintained below 2 dB for 3000 km transmission of standard-singlemode fiber without dispersion compensation.
Abstract: Coherent optical orthogonal frequency division multiplexing is proposed to combat dispersion in optical media. It is shown that optical-signal-to-noise ratio penalty at 10 Gbit/s is maintained below 2 dB for 3000 km transmission of standard-singlemode fibre without dispersion compensation.
629 citations
TL;DR: In this article, a band notch characteristic using a slot-type split ring resonator (SRR) working at microwave frequencies is used for designing a UWB antenna requiring the rejection of some frequency band, which is already in use by existing wireless services.
Abstract: A band notch characteristic using a slot-type split ring resonator (SRR) working at microwave frequencies is used for designing a UWB antenna requiring the rejection of some frequency band, which is already in use by existing wireless services. The slot-type SRR is employed effectively for notching unwanted frequency band such as that for WLAN service, since it can be implemented with a small dimension and in a high Q operation similarly to the conventional strip-type SRR. Based on the simulation and measurement results, a band notched UWB antenna using a slot-type SRR is very effective in rejecting unwanted frequency in terms of its selectivity and small real estate.
280 citations
TL;DR: In this paper, a quantum cascade laser at ∼4.4 THz (λ∼68 µm) was demonstrated, which was measured to emit 248mW peak power in pulsed mode and 138mW continuous wave power at heatsink temperatures of 10k.
Abstract: Demonstration of quantum-cascade lasers at ∼4.4 THz (λ∼68 µm), which are measured to emit 248 mW peak power in pulsed mode, and 138 mW continuous-wave power at heatsink temperatures of 10 K, is reported. These lasers are based on a resonant-phonon depopulation scheme, and use a semi-insulating surface-plasmon waveguide.
264 citations
TL;DR: In this article, a single-feed rectangular-ring textile antenna is proposed for wireless body area networks operating in the 2.45 GHz ISM band, where conductive parts of the planar antenna consist of FlecTron/spl reg/, whereas fleece fabric is used as nonconductive antenna substrate.
Abstract: A single-feed rectangular-ring textile antenna is proposed for wireless body area networks operating in the 2.45 GHz ISM band. The conductive parts of the planar antenna consist of FlecTron/spl reg/, whereas fleece fabric is used as non-conductive antenna substrate. This results in a highly efficient, flexible and wearable antenna to be integrated in garments. The robustness of the antenna characteristics with respect to bending is proven.
186 citations
TL;DR: Experimental results have confirmed that the proposed metric outperforms the standard MI metric by correlating better with the subjective quality of fused images.
Abstract: A novel image fusion performance metric using mutual information is proposed. The metric is based on Tsallis entropy, which is a one-parameter generalisation of Shannon entropy. Experimental results have confirmed that the proposed metric outperforms the standard MI metric by correlating better with the subjective quality of fused images.
179 citations
TL;DR: By combining the techniques of optical TDM with polarisation multiplexing and DQPSK modulation format, 240 km transmission of 1.28 Tbit/s and 160 km transmission was performed in a single wavelength channel as mentioned in this paper.
Abstract: By combining the techniques of optical TDM with polarisation multiplexing and DQPSK modulation format, 240 km transmission of 1.28 Tbit/s and 160 km transmission of 2.56 Tbit/s has been performed in a single wavelength channel.
161 citations
TL;DR: In this paper, two methods to fuse a 3D gyroscope with a three-dimensional accelerometer in order to measure rotations are presented, and the good reported accuracies make this system suitable for clinical evaluation.
Abstract: Two methods to fuse a 3D gyroscope with a 3D accelerometer in order to measure rotations are presented. They are compared with a method requiring only a 3D gyroscope and assessed with a reference system. The good reported accuracies make this system suitable for clinical evaluation.
156 citations
TL;DR: Use of linear frequency diverse array (FDA) is proposed, whereby each array channel operates at a different frequency and produces a range dependent pattern, suggesting detection improvement in GHTI processing.
Abstract: The ability to suppress range ambiguous clutter is difficult for forward-looking arrays in GHTI processing. Use of linear frequency diverse array (FDA) is proposed, whereby each array channel operates at a different frequency and produces a range dependent pattern. The FDA significantly increases output signal-to-interference plus noise ratio (SINR) at the range ambiguous clutter Doppler, suggesting detection improvement. Output SINR is shown to increase by as much as 40 dB when compared to a constant frequency array.
148 citations
TL;DR: In this paper, it was demonstrated that long nanowires with radii as small as 30 nm can be manufactured with a conventional coupler fabrication rig, and the temporal deterioration of nanowire optical properties has been studied and correlated with its mechanical behaviour.
Abstract: It is demonstrated for the first time that long nanowires with radii as small as 30 nm can be manufactured with a conventional coupler fabrication rig. The temporal deterioration of nanowire optical properties has been studied and correlated with its mechanical behaviour. The original transmission properties have been restored by a post-fabrication treatment.
135 citations
TL;DR: A multilayer approach to nonnegative matrix factorisation algorithms considerably improves their performance; especially if a problem is ill-conditioned, or data are badly scaled, and projected gradient algorithms are used.
Abstract: A multilayer approach to nonnegative matrix factorisation algorithms is proposed. It considerably improves their performance; especially if a problem is ill-conditioned, or data are badly scaled, and projected gradient algorithms are used. This is fully confirmed by extensive simulations with diverse types of data in application to blind source separation.
TL;DR: In this article, a novel layout for an ultra-compact arrayed-waveguide grating (AWG) demultiplexer is presented, which has two overlapped free propagation regions, and is more compact than a conventional layout.
Abstract: A novel layout for an ultra-compact arrayed-waveguide grating (AWG) demultiplexer is presented. The present layout has two overlapped free propagation regions, and is more compact than a conventional layout. Using αSi-on-SiO2 nanowire waveguides, an ultra-small 4×4 AWG (about 40×50 µm2) with channel spacing of 11 nm is fabricated and characterised.
TL;DR: In this article, a broadband printed CPW-fed circular slot antenna is proposed, which is composed of a circular slot fed with a 50'Ω CPW line through a circular patch.
Abstract: A broadband printed CPW-fed circular slot antenna is proposed. This antenna is composed of a circular slot fed with a 50 Ω CPW line through a circular patch. A parametric study was carried out to optimise the proposed structure, and the simulated and measured results show that the proposed design offers an ultra-wide bandwidth of 143.2% (from 2.3 to 13.9 GHz).
TL;DR: In this article, the realisation and characterisation of an electronically reconfigurable 35 GHz reflectarray, which is able to steer the main beam continuously between −20 and +20°, is reported.
Abstract: The realisation and characterisation of an electronically reconfigurable 35 GHz reflectarray, which is able to steer the main beam continuously between −20 and +20°, is reported. The tunable unit cells of the reflectarray are filled with nematic liquid crystal, a material that is able to change its effective permittivity as a result of an applied control voltage of up to 15 V. First, the unit cell and its performance, and then the setup of the reconfigurable reflectarray and its measured far-field patterns, are described.
TL;DR: In this article, the fabrication and characterisation of high-quality silicon membrane photonic crystals are reported, and the etching process is carefully optimized to give holes with very smooth and vertical sidewalls, resulting in propagation, with a minimum loss of 4.1 plusmn 0.9 dB/cm in a single line defect (W1) waveguide.
Abstract: The fabrication and characterisation of high-quality silicon membrane photonic crystals are reported. The etching process was carefully optimised to give holes with very smooth and vertical sidewalls, resulting in propagation, with a minimum loss of 4.1plusmn0.9 dB/cm in a single line defect (W1) waveguide
TL;DR: This Letter examines a power-interleaver generation method to alleviate the concern that the base station has to use a considerable amount of memory to store these interleavers, which may cause serious concern when the number of users is large.
Abstract: A user-specific interleaver design for interleave-division multiple-access (IDMA) systems is proposed. This method can solve the memory cost problem for chip-level interleavers, and reduce the amount of information exchange between mobile stations and base stations to specify the interleaver used as their identifications.
TL;DR: In this paper, a dual-band antenna for wearable WLAN computing applications is introduced, which consists of three discs and a coaxial post, and operates at 2400 and 5200 MHz.
Abstract: A novel dual-band antenna for wearable WLAN computing applications is introduced. This antenna comprises three discs and a coaxial post. Its appearance is of a standard metal button of the type used in denim jeans. The antenna is easily disguised and less sensitive to clothing than printed patches, which use the textile fabric as a substrate or superstrate. The antenna requires no external matching circuitry and operates at 2400 and 5200 MHz. The radiation patterns are omnidirectional around the central post of the antenna.
TL;DR: In this article, high electron mobility GaN/AlGaN transistors in the 0.2-2.5 GHz frequency range were used for detecting terahertz radiation at cryogenic and room temperatures.
Abstract: Detection of subterahertz and terahertz radiation by high electron mobility GaN/AlGaN transistors in the 0.2-2.5 THz frequency range (much higher than the cutoff frequency of the transistors) is reported. Experiments were performed in the temperature range 4-300 K. For the lowest temperatures, a resonant response was observed. The resonances were interpreted as plasma wave excitations in gated two-dimensional electron gas. Non-resonant detection was observed at temperatures above 100 K. Estimates for noise equivalent power show that these transistors can be used as efficient detectors of terahertz radiation at cryogenic and room temperatures
TL;DR: In this paper, a reflectarray antenna composed of double crossed loops of variable lengths printed on a conductor backed substrate is introduced, which demonstrates a radiation efficiency close to 55% and 1'dB gain.
Abstract: A reflectarray antenna composed of double crossed loops of variable lengths printed on a conductor backed substrate is introduced. Using this technique, a single-layer reflectarray with wider bandwidth compared to conventional single-layer reflectarrays is fabricated and measured. Measured results demonstrate a radiation efficiency close to 55% and 1 dB gain–bandwidth of 10%, centred at 22 GHz.
TL;DR: In this article, an electric field tunable microwave bandpass filter based on ferromagnetic resonance (FMR) in a bilayer of yttrium iron garnet and lead zirconate titanate has been designed and characterised.
Abstract: An electric field tunable microwave bandpass filter based on ferromagnetic resonance (FMR) in a bilayer of yttrium iron garnet and lead zirconate titanate has been designed and characterised. The filter tunability is accomplished through magnetoelectric coupling that manifests as a shift in the FMR. Studies on a microstripline filter show a 125 MHz tuning range for E=0-3 kV/cm and an insertion loss of 5 dB at 6.5 GHz.
TL;DR: In this article, a new empirical path loss model for wireless communication at 24 GHz above a flat, lossy medium, representing human tissue, was presented, which is valid for dipole antennas for heights up to 5 cm above the phantom and for distances up to 40 cm.
Abstract: A new empirical path loss model for wireless communication at 24 GHz above a flat, lossy medium, representing human tissue, is presented The model is valid for dipole antennas for heights up to 5 cm above the phantom and for distances up to 40 cm, and was applied to muscle and brain simulating media For antennas placed close to the lossy medium, it was found that antenna height has a major influence on path loss The model has been validated by measurements and simulations, which show excellent agreement
TL;DR: In this article, a mid-infrared (∼3.3µm) interband cascade laser has been demonstrated at temperatures up to 264 K with a thermoelectric cooler.
Abstract: Continuous-wave operation of a mid-infrared (∼3.3 µm) interband cascade laser has been demonstrated at temperatures up to 264 K. The laser has also been operated continuously with a thermoelectric cooler near 260 K for more than 1900 h without observable degradation.
TL;DR: In this paper, a novel CPW-fed broadband circularly polarised square slot antenna is proposed and fabricated, which is fed by a widened L-type strip along the diagonal line of the square slot.
Abstract: A novel CPW-fed broadband circularly polarised square slot antenna is proposed and fabricated. The proposed antenna is fed by a CPW with a widened L-type strip along the diagonal line of the square slot. Measured results show that the 3 dB axial-ratio bandwidth of the proposed antenna can reach 17%. The proposed antenna has simple coplanar geometry which can be easily fabricated on inexpensive substrate.
TL;DR: In this article, the authors proposed a high-speed all-optical logic operation with high extinction ratio using a parallel SOA Mach-Zehnder interferometer (MZI) structure.
Abstract: All-optical composite logic gates with XOR, NOR, OR and NAND functions using a parallel semiconductor optical amplifier (SOA) Mach-Zehnder interferometer (MZI) structure that enables simultaneous operations of various logic functions have been proposed and experimentally demonstrated. The proposed scheme is robust and feasible for high-speed all-optical logic operation with high extinction ratio.
TL;DR: Using the multipath component distance (MCD) is used to calculate the distance between individual multipath components estimated by a channel parameter estimator, such as SAGE, which significantly improved clustering performance.
Abstract: The problem of identifying clusters from MIMO measurement data is addressed. Conventionally, visual inspection has been used for cluster identification, but this approach is impractical for a large amount of measurement data. For automatic clustering, the multipath component distance (MCD) is used to calculate the distance between individual multipath components estimated by a channel parameter estimator, such as SAGE. This distance is implemented in the well-known KMeans clustering algorithm. To demonstrate the effectiveness of the choice made, the performance of the MCD and the Euclidean distance were compared by clustering synthetic data generated by the 3GPP spatial channel model (SCM). Using the MCD significantly improved clustering performance.
TL;DR: In this paper, an electro-optic intensity modulator (EOM) is used to generate an ultra-wideband (UWB) doublet using an EOM biased at a nonlinear region near the maximum or minimum point of its transfer function.
Abstract: A novel and simple method to generate an ultra-wideband (UWB) doublet using an electro-optic intensity modulator (EOM) is proposed and experimentally demonstrated. The EOM is biased at a nonlinear region near the maximum or minimum point of its transfer function. When a Gaussian pulse is applied to the EOM, the pedestal or the peak part of the pulse is inverted, leading to the generation of a UWB doublet.
TL;DR: In this article, the use of multiple layers of self-organised InAs quantum dots as a very effective dislocation filter is demonstrated, and it is shown that In0.5Ga 0.5As/GaAs quantum dot lasers grown directly on silicon substrates with the quantum dot buffer layer exhibit substantially reduced threshold currents.
Abstract: The use of multiple layers of self-organised InAs quantum dots as a very effective dislocation filter is demonstrated. In0.5Ga0.5As/GaAs quantum dot lasers grown directly on silicon substrates with the InAs quantum dot buffer layer exhibit substantially reduced threshold currents (Jth∼900 A/cm2), compared to devices grown on silicon without the dot buffer layer (Jth≥1500 A/cm2).
TL;DR: In this paper, a current-programmed, current-output active TFT image sensor suitable for real-time X-ray imaging (e.g. fluoroscopy) using hydrogenated amorphous silicon (a-Si:H) thin-film transistor (TFT) technology is introduced.
Abstract: A new current-programmed, current-output active TFT image sensor suitable for real-time X-ray imaging (e.g. fluoroscopy) using hydrogenated amorphous silicon (a-Si:H) thin-film-transistor (TFT) technology is introduced. The proposed pixel circuit can successfully compensate for characteristic variations such as mobility and threshold voltage shift in a-Si:H TFTs. Simulation and measurement results show that high on-pixel amplification can be accomplished with this pixel circuit.
TL;DR: In this article, a new class of reconfigurable antenna based on monopole structures containing liquid dielectrics is presented, and it is determined that the operating principle of this class of antenna is essentially that of a dielectric resonator, where salt (in solution) modifies the Dielectric properties.
Abstract: A new class of reconfigurable antenna based on monopole structures containing liquid dielectrics is presented. It was determined that the operating principle of this class of antenna is essentially that of a dielectric resonator, where salt (in solution) modifies the dielectric properties. The resonator column height determined the operating frequency, allowing match and frequency of operation to be fully tunable over 1–2.5 GHz while salinity mainly influences the bandwidth.
TL;DR: In this article, it was shown that the tolerance to optical filtering of a DPSK system can be increased by decreasing the differential delay of the traditional MZI-demodulator to less than one bit period.
Abstract: Tolerance to optical filtering of a DPSK system can be increased significantly by decreasing the differential delay of the traditional MZI-demodulator to less than one bit-period. It is shown that a 43 Gbit/s DPSK signal can support 50 GHz channel spacing if the delay is decreased to 65% of a bit-period.