Showing papers in "Electronics Letters in 2003"
TL;DR: In this article, a simple formulation to compute the envelope correlation of an antenna diversity system is derived, which does not require the computation nor the measurement of the radiation pattern of the antenna system.
Abstract: A simple formulation to compute the envelope correlation of an antenna diversity system is derived. It is shown how to compute the envelope correlation from the S-parameter description of the antenna system. This approach has the advantage that it does not require the computation nor the measurement of the radiation pattern of the antenna system. It also offers the advantage of providing a clear understanding of the effects of mutual coupling and input match on the diversity performance of the antenna system.
1,004 citations
TL;DR: A novel coding technique is proposed for the quasi-static fading relay channel, which indicates a combined diversity and coding gain, which is significant even for simple constituent codes.
Abstract: A novel coding technique is proposed for the quasi-static fading relay channel. The source broadcasts a recursive code to both relay and destination. The relay decodes, interleaves, and re-encodes the message prior to forwarding. Because the destination receives both codes in parallel, a distributed turbo code is embedded in the relay channel. Results indicate a combined diversity and coding gain, which is significant even for simple constituent codes.
411 citations
TL;DR: Evidence that the ‘Kronecker’ model underestimates the channel capacity of an 8×8 multiple input, multiple output (MIMO) system in indoor non-line-of-sight (NLOS) scenarios is presented.
Abstract: Evidence that the ‘Kronecker’ model underestimates the channel capacity of an 8×8 multiple input, multiple output (MIMO) system in indoor non-line-of-sight (NLOS) scenarios is presented. Moreover, the model does not render the multipath structure correctly, which is the cause for the systematic capacity mismatch.
329 citations
TL;DR: In this paper, it was shown that the dominant factor controlling reflectarray bandwidth is the bandwidth of the radiating element, and that the effect of nonconstant path delays over the surface of the flat reflector has little significance unless the aperture is electrically very large and the f/D ratio is small.
Abstract: It is shown that the dominant factor controlling reflectarray bandwidth is the bandwidth of the radiating element, and that the effect of non-constant path delays over the surface of the flat reflector has little significance unless the aperture is electrically very large and the f/D ratio is small. An example of a polarisation-twist reflectarray using aperture coupled elements with time delay lines is used to demonstrate this conclusion.
263 citations
TL;DR: In this paper, a square planar monopole antenna with two feed points and a bevelled variant is designed to improve pattern and impedance bandwidth, and these antennas exhibit an excellent performance compared to existing planar mono-mono antennas.
Abstract: Planar monopole antennas with multiple feed points are proposed to improve pattern and impedance bandwidth. A square planar monopole antenna including two feed points and a bevelled variant are designed. These antennas exhibit an excellent performance compared to existing planar monopoles.
246 citations
TL;DR: In this article, the Douglas-Gunn algorithm is used to subdivide the update procedure into two sub-steps, at each sub-step only a tri-diagonal matrix needs to be solved for one field component, and other two field components are updated explicitly in one step.
Abstract: The Crank-Nicolson method is an unconditionally stable, implicit numerical scheme with second-order accuracy in both time and space. When applied to solve Maxwell's equations in two-dimensions, the resulting matrix is block tri-diagonal, which is very expensive to solve. The Douglas-Gunn algorithm is used to subdivide the update procedure into two sub-steps. At each sub-step only a tri-diagonal matrix needs to be solved for one field component. The other two field components are updated explicitly in one step. The numerical dispersion relations are given for the original Crank-Nicolson scheme and for the Douglas-Gunn modification. The predicted numerical dispersion is shown to agree with numerical experiments, and its numerical anisotropy is shown to be much smaller than that of the ADI-FDTD.
227 citations
TL;DR: In this paper, power scaling of continuous-wave fiber lasers with up to 0.5 kW output powers from a single fibre with nearly diffraction-limited beam quality without the limitation of nonlinear effects is reported.
Abstract: Power scaling of continuous-wave fibre lasers with up to 0.5 kW output powers from a single fibre with nearly diffraction-limited beam quality without the limitation of nonlinear effects is reported.
220 citations
TL;DR: An iterative decoding architecture based on stochastic computational elements is proposed that provides an alternative to analogue decoding for high-speed/low-power applications.
Abstract: An iterative decoding architecture based on stochastic computational elements is proposed. Simulation results for a simple low-density parity-check code demonstrate near-optimal performance with respect to a maximum likelihood decoder. The proposed method provides an alternative to analogue decoding for high-speed/low-power applications.
209 citations
TL;DR: In this paper, the effects of mutual coupling between receive elements in a multi-element antenna on multiple-input multiple-output (MIMO) system capacity were reported. But the authors focused on the effect of the mutual coupling at the receive array antenna.
Abstract: The effects of mutual coupling between receive elements in a multi-element antenna on multiple-input multiple-output (MIMO) system capacity are reported. The results are based upon analysis of mutual coupling calculated for a measured linear array of five printed dipole elements with 0.56 of a wavelength spacing. It is shown that the presence of mutual coupling at the receive array antenna leads to additional correlation between spatial channels and results in a loss of MIMO system capacity.
202 citations
TL;DR: In this paper, a solution to the problem of charge being trapped on the gate of a floating gate MOS transistor during fabrication is presented, which does not alter the floating nature of the gate since it does not use any kind of active or passive device to get rid of the accumulated charge.
Abstract: A solution to the problem of charge being trapped on the gate of a floating gate MOS transistor during fabrication is presented. The solution does not alter the floating nature of the gate of the device since it does not use any kind of active or passive device to get rid of the accumulated charge. In addition, it does not require any post-processing techniques such as exposure to UV light and does not require any extra masks.
195 citations
TL;DR: The bit error rate of the Alamouti scheme with transmit antenna selection in flat Rayleigh fading channels is presented and performance analysis reveals that this scheme achieves a full diversity order, as if all the transmit antennas were used.
Abstract: The bit error rate of the Alamouti scheme with transmit antenna selection in flat Rayleigh fading channels is presented. Performance analysis reveals that this scheme achieves a full diversity order, as if all the transmit antennas were used. This scheme has a fixed low decoding complexity and provides a systematic method to construct full-rate space-time block codes with a full diversity order.
TL;DR: In this article, a 40"Gbit/s all-optical XOR gate with a hybrid-integrated planar silica waveguide structure and semiconductor optical amplifiers is demonstrated.
Abstract: A 40 Gbit/s all-optical XOR gate that uses a novel topology to allow high-speed operation is demonstrated. The gate used is a Mach-Zehnder interferometer comprising a hybrid-integrated planar silica waveguide structure and semiconductor optical amplifiers.
TL;DR: A low complexity sub-optimal power allocation scheme among transmit antennas is proposed and results show that with the same antenna density DAS outperforms a co-located antenna system (CAS) in terms of average and outage spectral efficiency.
Abstract: The downlink capacity potential of a distributed antenna system (DAS) with random antenna layout is investigated. A low complexity sub-optimal power allocation scheme among transmit antennas is proposed. Simulation results show that with the same antenna density DAS outperforms a co-located antenna system (CAS) in terms of average and outage spectral efficiency.
TL;DR: For the reception of multicode direct sequence (DS)-CDMA signals, the MMSE frequency domain equalisation is applied instead of RAKE combining and shows only slight performance degradation compared to the MC-CDMA with minimum mean square error combining (MMSEC).
Abstract: For the reception of multicode direct sequence (DS)-CDMA signals, the MMSE frequency domain equalisation is applied instead of RAKE combining. The achievable BER performance in a frequency selective Rayleigh fading channel is evaluated by computer simulation. It is shown by computer simulation that the DS-CDMA with MMSE frequency domain equalisation outperforms the DS-CDMA with RAKE combining and shows only slight performance degradation compared to the MC-CDMA with minimum mean square error combining (MMSEC).
TL;DR: Stacked InAs/InGaAs quantum dots are used as an active media of metamorphic InGaAs-InGaAlAs lasers grown on GaAs substrates by molecular beam epitaxy as discussed by the authors.
Abstract: Stacked InAs/InGaAs quantum dots are used as an active media of metamorphic InGaAs-InGaAlAs lasers grown on GaAs substrates by molecular beam epitaxy. High quantum efficiency (/spl eta//sub i/>60%) and low internal losses (/spl alpha/<3-4 cm/sup -1/) are realised. The transparency current density per single QD layer is estimated as /spl sim/70 A/cm/sup 2/ and the characteristic temperature is 60 K (20-85/spl deg/C). The emission wavelength exceeds 1.51 /spl mu/m at temperatures above 60/spl deg/C.
TL;DR: The weaknesses of a recently proposed Smart's ID- based authenticated two-pass key agreement protocol are discussed and an efficient ID-based authenticated key agreement Protocol with the optimal number of evaluations of Weil pairing is proposed.
Abstract: The weaknesses of a recently proposed Smart's ID-based authenticated two-pass key agreement protocol are discussed. An efficient ID-based authenticated key agreement protocol with the optimal number of evaluations of Weil pairing is proposed.
TL;DR: In this paper, a genetic algorithm-based procedure for solving the optimal phasor measurement units (PMUs) placement problem is presented, which determines the minimal number of PMUs and their geographic distribution making the network observable, and shows the relationship between the number of current phasors that must be measured on each PMU and the necessary number of units for a given network.
Abstract: A genetic algorithm-based procedure for solving the optimal phasor measurement units (PMUs) placement problem is presented. It determines the minimal number of PMUs and their geographic distribution making the network observable, and it shows the relationship between the number of current phasors that must be measured on each PMU and the necessary number of PMUs for a given network.
TL;DR: In this paper, the transmission characteristics of two waveguides, one carrying a forward and the other a backward magneto-inductive wave, are investigated, and the experimental results obtained are compared with the theoretical predictions.
Abstract: The transmission characteristics of two waveguides, one carrying a forward, the other a backward magneto-inductive wave, are investigated. The experimental results obtained are compared with the theoretical predictions. It is shown that there is excellent agreement for the frequency dependence of the propagation coefficients and good agreement for the attenuation coefficients.
TL;DR: Experimental results with typical problems show that queen-bee evolution makes genetic algorithms quickly approach the global optimum by enhancing exploitation and exploration of genetic algorithms.
Abstract: A new evolution method called queen-bee evolution is proposed for enhancing the optimisation capability of genetic algorithms. This queen-bee evolution is similar to nature in that the queen-bee plays a major role in reproduction process. Experimental results with typical problems show that queen-bee evolution makes genetic algorithms quickly approach the global optimum by enhancing exploitation and exploration of genetic algorithms.
TL;DR: In this paper, the fabrication of 1.0 mm gate-length E-mode AlGaN=GaN HEMTs on SiC having a peak extrinsic transconductance of 248 mS=mm was reported.
Abstract: AlGaN=GaN high electron mobility transistors (HEMTs) are excellent candidates for high power and high frequency applications at elevated temperatures owing to their superior material properties [1–4]. To date, most of the efforts on GaN-based electronic devices have been directed towards depletion mode (D-mode) AlGaN=GaN HEMTs. However, some applications involving low-power digital circuits require the integration of both E-mode and D-mode HEMTs. Therefore, there is a great interest in the realisation of E-mode AlGaN=GaN HEMTs. Owing to the large polarisation charge in the AlGaN=GaN heterostructure, fabrication of GaN-based E-mode devices is more difficult compared to other material systems such as InP and GaAs. There have been only a few reports on these devices, and to date, the device performance is as yet unsatisfactory [5–7]. In this Letter, we report the fabrication of 1.0 mm gate-length E-mode AlGaN=GaN HEMTs grown by metal organic chemical vapour deposition (MOCVD) on SiC having a peak extrinsic transconductance of 248 mS=mm. These devices exhibited a current density of 470 mA=mm, a threshold voltage of 75 mV, an fT of 8 GHz and an fmax of 26 GHz. These results are significant improvements over previously reported GaN-based E-mode HEMTs.
TL;DR: In this article, an n-bit Toffoli gate quantum circuit based on the realisation proposed by Barenco et al., where some of the TOffoli gates in their construction are replaced with Peres gates, is presented.
Abstract: An n-bit Toffoli gate quantum circuit based on the realisation proposed by Barenco et al., where some of the Toffoli gates in their construction are replaced with Peres gates, is presented. This results in a significant cost reduction. The main contribution of this presentation is a quantum circuit which simulates the (m+1)-bit Toffoli gate with 32m−120 elementary quantum gates and one garbage bit which is passed unchanged.
TL;DR: The lossless Huffman's coding is used to increase the compression ratio and quality preservation for good compression ratios is reported.
Abstract: A new method for ECG compression is presented. After the pyramidal wavelet decomposition, the resultant coefficients are subjected to an iterative threshold until a fixed percentage target of wavelet coefficients to be zeroed is reached. Next, the lossless Huffman's coding is used to increase the compression ratio. Quality preservation for good compression ratios is reported.
TL;DR: A new packet delay analysis for the IEEE 802.11b protocol is developed by extending throughput analysis introduced by Bianchi by identifying when the RTS/CTS mechanism achieves lower packet delay with respect to the basic access mechanism and becomes highly beneficial for the performance of IEEE802.11 WLANs.
Abstract: A new packet delay analysis for the IEEE 802.11b protocol is developed by extending throughput analysis introduced by Bianchi. This analysis is validated by comparison with simulation results using the OPNETTM simulation package. Packet delay results are presented as a function of a number of stations and packet size for basic access and RTS/CTS medium access mechanisms. The proposed analysis identifies when the RTS/CTS mechanism achieves lower packet delay with respect to the basic access mechanism and becomes highly beneficial for the performance of IEEE 802.11 WLANs.
TL;DR: A new transmission scheme which uses two transmitting sensors and space-time block code to provide transmission diversity in distributed wireless sensor networks with neither antenna-array nor transmission synchronisation is proposed, which enhances power/bandwidth efficiency and reliability.
Abstract: A new transmission scheme which uses two transmitting sensors and space-time block code to provide transmission diversity in distributed wireless sensor networks with neither antenna-array nor transmission synchronisation is proposed. Full diversity and full rate are achieved which enhances power/bandwidth efficiency and reliability. Simulations demonstrate its superior performance in saving transmission energy.
TL;DR: It is shown that the proper allocation of the bandwidth for the optical network units leads to improvement in the network's performance.
Abstract: A dynamic bandwidth allocation algorithm in Ethernet passive optical networks (EPON) is proposed. Specifically, an analytic model to estimate the proper allocation of the bandwidth in EPON is introduced. In particular, it is shown that the proper allocation of the bandwidth for the optical network units leads to improvement in the network's performance.
TL;DR: A simple fragile watermarking scheme for image authentication is proposed that is secure, fast, and capable of detecting and localising modification, and is immune of the well-known quantisation attack.
Abstract: A simple fragile watermarking scheme for image authentication is proposed. The insertion of a binary watermark is accomplished by replacing the least significant bit of the host image with a random binary image obtained by random permutations and suitable XOR operations among bitplanes. The proposed scheme is secure, fast, and capable of detecting and localising modification, and is immune of the well-known quantisation attack.
TL;DR: In this paper, a two-pump parametric amplifier constructed with highly nonlinear fiber was reported to achieve a 40-dB equalised continuous-wave parametric gain over 33.8nm without any gainflattening elements.
Abstract: Record performance from a two-pump parametric amplifier constructed with highly nonlinear fibre is reported. Equalised continuous-wave parametric gain of 40 dB was achieved over 33.8 nm without any gain-flattening elements. Maximal difference between signal and idler powers was measured to be 1 dB within the equalised gain band.
TL;DR: A breast cancer detection technique using multi-static radar, using backscatter data produced from an anatomically realistic 2D MRI-derived FDTD model of the breast is proposed, although clarity of detection is dependent on mitigating antenna mutual coupling and skin reflections.
Abstract: A breast cancer detection technique using multi-static radar is proposed For the first time, images are produced using this technique, using backscatter data produced from an anatomically realistic 2D MRI-derived FDTD model of the breast Successful detection of a 2 mm-diameter tumour is demonstrated, although clarity of detection is dependent on mitigating antenna mutual coupling and skin reflections
TL;DR: In this article, the authors demonstrate single-photon interference over 100 km using a balanced gated-mode photon detector and a plug-and-play system for quantum key distribution, achieving a fidelity of more than 90% and a QBER of less than 10%.
Abstract: The authors demonstrate single-photon interference over 100 km using a balanced gated-mode photon detector and a plug and play system for quantum key distribution. The visibility with 0.1 photon/pulse was more than 80% after 100 km transmission. This corresponds to the fidelity of a quantum cryptography system of more than 90% and a QBER of less than 10%, satisfying the security criteria.
TL;DR: In this article, a modified inverted-L monopole antenna for dual-band operation is proposed, which is designed to operate in 2.4 GHz and 5 GHz bands for WLAN applications in IEEE 802.11a/b and HIPERLAN/2 systems.
Abstract: A novel compact modified inverted-L monopole antenna for dual-band operation is proposed. The proposed antenna is designed to operate in 2.4 GHz (2400–2484 MHz) and 5 GHz (5150–5825 MHz) bands for WLAN applications in IEEE 802.11a/b and HIPERLAN/2 systems. The method to realise the desired dual-band operation is by introducing a meandered wire and a conducting triangular section to a conventional inverted-L monopole, which results in a small antenna size of 7×18 mm2. Good impedance bandwidth performance is also observed.