Showing papers in "Electronics Letters in 2014"
TL;DR: In this article, a terahertz (THz) frequency quantum cascade laser with peak powers of > 1 W from a single facet in the pulsed mode is demonstrated.
Abstract: Terahertz (THz) frequency quantum cascade lasers emitting peak powers of >1 W from a single facet in the pulsed mode are demonstrated. The active region is based on a bound-to-continuum transition with a one-well injector, and is embedded into a surface-plasmon waveguide. The lasers emit at a frequency of ∼3.4 THz and have a maximum operating temperature of 123 K. The maximum measured emitted powers are ∼1.01 W at 10 K and ∼420 mW at 77 K, with no correction made to allow for the optical collection efficiency of the apparatus.
249 citations
TL;DR: In this paper, a circular phased array antenna that can generate orbital angular momentum (OAM) radio beams in the 10 GHz band is described, which consists of eight inset-fed patch elements and a microstrip corporate feeding network.
Abstract: A circular phased array antenna that can generate orbital angular momentum (OAM) radio beams in the 10 GHz band is described. The antenna consists of eight inset-fed patch elements and a microstrip corporate feeding network. A full-wave electromagnetic simulator is used to aid the antenna design and theoretical simulations are confirmed by measurements.
245 citations
TL;DR: In this article, a two-dimensional displacement and alignment sensor is proposed based on two open-ended transmission lines, each loaded with a split ring resonator (SRR), which can be used to sense a displacement of the loading SRRs in two orthogonal directions.
Abstract: A two-dimensional displacement and alignment sensor is proposed based on two open-ended transmission lines, each loaded with a split ring resonator (SRR). In this arrangement, the depth of resonance-induced notches in the reflection coefficients can be used to sense a displacement of the loading SRRs in two orthogonal directions. Since the operation principle of the sensor is based on the symmetry properties of SRR-loaded transmission lines, the proposed sensor benefits from immunity to variations in ambient conditions. More importantly, it is shown that in contrast to previously published metamaterial-inspired two-dimensional displacement and alignment sensors, the proposed sensor can be operated at a single fixed frequency. The concept and simulation results are validated through measurement.
129 citations
TL;DR: Experiments show that the proposed three-step parallel framework for HEVC dramatically accelerates more than the state-of-the-art parallel method.
Abstract: High-efficiency video coding (HEVC) is the next generation standard of video coding. The deblocking filter (DF) constitutes a significant part of the HEVC decoder complexity. A three-step parallel framework (TPF) is proposed for the H.264/AVC DF, which is also suitable for HEVC except the third step. The third step of the TPF is replaced with a directed acyclic graph-based order. Experiments show that the proposed method dramatically accelerates more than the state-of-the-art parallel method.
118 citations
TL;DR: A spectrum-efficient superimposed pilot design for downlink large-scale MIMO scenarios is proposed, where frequency-domain pilots of different transmit antennas occupy completely the same subcarriers in the frequency domain, where the proposed scheme performs well and can approach the performance bound.
Abstract: Large-scale multiple-input multiple-output (MIMO) with high spectrum and energy efficiency is a very promising key technology for future 5G wireless communications. For large-scale MIMO systems, accurate channel state information (CSI) acquisition is a challenging problem, especially when each user has to distinguish and estimate numerous channels coming from a large number of transmit antennas in the downlink. Unlike the conventional orthogonal pilots whose pilot overhead prohibitively increases with the number of transmit antennas, a spectrum-efficient superimposed pilot design for downlink large-scale MIMO scenarios is proposed, where frequency-domain pilots of different transmit antennas occupy completely the same subcarriers in the frequency domain. Meanwhile, spatial-temporal common sparsity of large-scale MIMO channels motivates us to exploit the emerging theory of structured compressive sensing (CS) for reliable MIMO channel estimation, which is realised by the proposed structured subspace pursuit (SSP) algorithm to simultaneously recover multiple channels with low pilot overhead. Simulation results demonstrate that the proposed scheme performs well and can approach the performance bound.
106 citations
TL;DR: The proposed multi-UAV-based system with a movable baseline overcomes the limitations of a single-Uav-based stereo vision system withA fixed baseline and the performance of the proposed system does not degrade significantly based on the altitude of UAVs.
Abstract: A multi-unmanned aerial vehicle (UAV)-based stereo vision system is proposed to assist global path planning of an unmanned ground vehicle (UGV) even in GPS-denied environments. The proposed system can optimally generate the depth map of ground objects and robustly detect obstacles. The proposed multi-UAV-based system with a movable baseline overcomes the limitations of a single-UAV-based stereo vision system with a fixed baseline. Thus, the performance of the proposed system does not degrade significantly based on the altitude of UAVs. The relative position and altitude estimation, multi-agent formation control and image processing techniques are considered to implement a prototype system. The experimental results demonstrate the performance of the implemented system for various baseline conditions between UAVs.
95 citations
TL;DR: In this article, the Gaussian and Poisson approximations of the binomial model of the molecule arrival process have been analyzed, and the regions in which the Poisson or Gaussian model is better in terms of root mean squared error of CDFs are investigated and confirmed using numerical simulations.
Abstract: The arrival of molecules in molecular communication via diffusion obeys, by its nature, the binomial distribution, considering the hitting probability as the success probability. It is, however, hard to work with the binomial cumulative distribution function (CDF) when considering consecutively sent symbols as it is necessary to add the distribution. Therefore, in the literature, two approximations of the binomial distribution are used. In the present reported work, the Gaussian and Poisson approximations of the binomial model of the molecule arrival process have been analysed. Considering the distance and the number of emitted molecules, the regions in which the Poisson or Gaussian model is better in terms of root mean squared error of CDFs are investigated and the regions using numerical simulations are confirmed.
94 citations
TL;DR: Simulation results show that the proposed signal detection algorithm converges fast, and achieves the near-optimal performance of the classical MMSE algorithm.
Abstract: The minimum mean square error (MMSE) signal detection algorithm is near-optimal for uplink multi-user large-scale multiple-input-multiple-output (MIMO) systems, but involves matrix inversion with high complexity. It is firstly proved that the MMSE filtering matrix for large-scale MIMO is symmetric positive definite, based on which a low-complexity near-optimal signal detection algorithm by exploiting the Richardson method to avoid the matrix inversion is proposed. The complexity can be reduced from O(K 3 ) to O(K 2 ), where K is the number of users. The convergence proof of the proposed algorithm is also provided. Simulation results show that the proposed signal detection algorithm converges fast, and achieves the near-optimal performance of the classical MMSE algorithm.
93 citations
TL;DR: Experiments show that the proposed method dramatically accelerates more than the state-of-the-art parallel method for HEVC IP.
Abstract: High-efficiency video coding (HEVC) is the state-of-the-art video coding standard, which adopts more complicated and time-consuming intra-prediction (IP) modes. Many-core processors are good candidates for speeding up HEVC IP in the case that HEVC IP can provide sufficient parallelism. Proposed is an efficient parallel framework for HEVC IP. Experiments show that the proposed method dramatically accelerates more than the state-of-the-art parallel method.
91 citations
TL;DR: In this paper, a microstrip-fed compact multi-band slot antenna using a single split-ring resonator (SRR) acting as a loading element introduces multiple lower-order resonances in the antenna, which can be controlled by varying the SRR's dimensions as well as its position with respect to the arm of the slot.
Abstract: A microstrip-fed compact multi-band slot antenna using a single split-ring resonator (SRR) is proposed. The SRR acting as a loading element introduces multiple lower-order resonances in the antenna, which can be controlled by varying the SRR's dimensions as well as its position with respect to the arm of the slot, without altering the geometry of the radiating slot. The concept is validated by a full-wave simulation study and by measurement on a fabricated prototype. The proposed antenna has satisfactory gain and monopolar radiation patterns in all the operating bands.
88 citations
TL;DR: In this paper, a 1.3 μm InAs/GaAs quantum-dot laser directly grown on Si substrates has been achieved by using InAlAs/GAAs strained-layer superlattice serving as dislocation filter layers (DFLs).
Abstract: A high-performance 1.3 μm InAs/GaAs quantum-dot laser directly grown on Si substrates has been achieved by using InAlAs/GaAs strained-layer superlattice serving as dislocation filter layers (DFLs). The Si-based laser achieves lasing operation up to 111°C with a threshold current density of 200 A/cm 2 and an output power exceeding 100 mW at room temperature.
TL;DR: In this article, a multicycle Rapid Thermal Annealing (RTA) process is presented that is capable of achieving up to 8% activation of the Mg-implanted GaN.
Abstract: A long-standing goal of GaN device research has been the development of a reliable, well-controlled process for p-GaN formation by ion implantation. Results to date have indicated an activation of 1% or less using high-temperature rapid thermal annealing (RTA) techniques and coimplantation. Although Mg is a relatively deep acceptor, this is still much less than the theoretically achievable value (8.2% based on the 160 meV acceptor level). A multicycle RTA process is presented that is capable of achieving up to 8% activation of the Mg-implanted GaN. This approaches the theoretical value, and represents a significant step in GaN device research.
TL;DR: In this article, a defected ground structure (DGS) for improving isolation between four ports in a collocated multiple-input-multiple-output (MIMO) antenna is proposed.
Abstract: A defected ground structure (DGS) for improving isolation between four ports in a collocated multiple-input–multiple-output (MIMO) antenna is proposed. Isolation improvement by 7 dB is achieved by reducing surface waves within the dielectric substrate. Mutual coupling values as low as −25 dB are obtained along both the E- and H-planes. The MIMO antenna includes a square patch antenna surrounded by a square ring patch antenna with the DGS etched in the form of a square ring. The DGS effectively suppresses the cross-polarisation levels for all radiating modes. The design and effectiveness of the DGS in improving isolation for a fabricated 4-port antenna are discussed.
TL;DR: In this paper, a novel and compact wideband multiple input multiple output (MIMO) antenna for mobile terminals is presented, which operates over a wide frequency range of 1.79-3.77 GHz suitable for longterm evolution (LTE), worldwide interoperability for microwave access (WiMAX) and wireless local area network (WLAN) handheld devices.
Abstract: A novel and compact wideband multiple input multiple output (MIMO) antenna for mobile terminals is presented. The proposed antenna operates over a wide frequency range of 1.79-3.77 GHz suitable for long-term evolution (LTE), worldwide interoperability for microwave access (WiMAX) and wireless local area network (WLAN) handheld devices. The MIMO antenna structure consists of two identical radiators with a small size of 10 × 17.7 mm 2 and a parasitic element with a T-shape. The radiators, which comprise four branches with a meandered strip feed, are symmetrically located with respect to the T-shaped parasitic element. The parasitic element is a novel design appended at the ground plane. By using this parasitic element, a better isolation performance has been achieved between the two radiators. The overall performance of the antenna in terms of s -parameters, radiation pattern, gain and envelope correlation coefficient is investigated and verified through measurements. The results obtained show that the proposed antenna has attractive physical properties due to being small, compact and embeddable in mobile handsets, and has good characteristics of wideband, isolation, gain and radiation pattern.
TL;DR: In this paper, a low-energy hybrid capacitor switching scheme for a low power successive approximation register (SAR) analogue-to-digital converter (ADC) is presented, which combines a new switch method and the monotonic technique.
Abstract: A novel low-energy hybrid capacitor switching scheme for a low-power successive approximation register (SAR) analogue-to-digital converter (ADC) is presented. The proposed switching scheme combines a new switch method and the monotonic technique. The new switch method can achieve no switching energy consumption in the first three comparison cycles. Furthermore, a low-energy monotonic procedure is performed for the rest of the comparisons. The average switching energy is reduced by 98.83% compared with the conventional architecture, resulting in the most energy-efficient switching scheme among the existing switching techniques. Besides the significant energy saving, the proposed switching scheme also achieves a 75% reduction of the capacitors over the conventional scheme.
TL;DR: A wireless indoor positioning system using white LED lights is proposed and it is identified that the optimum receiver height where localisation error gets minimised is between 2.5 and 3 m from the ceiling which corresponds well with the typical dimensions of a room.
Abstract: A wireless indoor positioning system using white LED lights is proposed. The time difference of arrival technique is employed and the phase differences between the received signals are determined to develop a positioning algorithm which can estimate the receiver location with a mean localisation error as low as 1 mm in a room of dimensions 5 × 5 × 3 m. Through simulations, it is identified that the optimum receiver height where localisation error gets minimised is between 2.5 and 3 m from the ceiling which corresponds well with the typical dimensions of a room.
TL;DR: A means of encoding and decoding data using wireless orbital angular momentum modes is proposed and analysed and the results are presented in terms of mode estimation error.
Abstract: A means of encoding and decoding data using wireless orbital angular momentum (OAM) modes is proposed and analysed. Source data symbols are used to select an OAM mode, which is generated using an 8-element circular array. A 2-element array is used to detect the mode by estimating the phase gradient of the received signal, and hence identifying the transmitted data symbol. The results are presented in terms of mode estimation error.
TL;DR: An efficient and effective algorithm which online exploits informative features for visual tracking and an online feature selection technique to design an adaptive appearance model, which explores the most informative features from the projections via maximising entropy energy.
Abstract: An efficient and effective algorithm which online exploits informative features for visual tracking is presented. First, a high-dimensional multi-scale spatio-colour image feature vector is developed, which takes into account both appearance and spatial layout information; secondly, this feature vector is randomly projected onto a low-dimensional feature space, where its projections preserve intrinsic information of the high-dimensional feature vector but effectively avoid the curse of dimensionality; and finally, an online feature selection technique to design an adaptive appearance model is proposed, which explores the most informative features from the projections via maximising entropy energy. Experiments on extensive challenging sequences demonstrate the superiority of the proposed method over some state-of-the-art algorithms.
TL;DR: In this article, an AlN/AlGaN high-electron-mobility transistor (HEMT) fabricated on a free-standing AlN substrate is demonstrated.
Abstract: An AlN/AlGaN high-electron-mobility transistor (HEMT) fabricated on a free-standing AlN substrate is demonstrated. A metal stack, composed of Zr/Al/Mo/Au, was found to show low contact resistivity for source and drain ohmic contacts. The fabricated AlN/AlGaN HEMT exhibited a maximum drain current of 38 mA/mm with a threshold voltage of -3.4 V. Negligible drain current degradation was observed at temperatures from 300 to 573 K, demonstrating that an AlN/AlGaN approach on an AlN substrate is promising for stable high-temperature operation.
TL;DR: In this article, a compact asymmetric coplanar strip (ACS)-fed ultra-wideband (UWB) monopole antenna with extra Bluetooth band for various wireless applications is presented.
Abstract: A compact asymmetric coplanar strip (ACS)-fed ultra-wideband (UWB) monopole antenna with extra Bluetooth band for various wireless applications is presented. The proposed antenna is composed of a modified ACS-fed structure and a staircase-shaped patch for covering the UWB band (3.1-10.6 GHz), which occupies a very compact size of 32.5 × 10 mm 2 . By etching a snake-shaped slot in the staircase-shaped patch, an additional band can be realised covering the Bluetooth band (2.4-2.484 GHz). Furthermore, the proposed antenna has been fabricated and measured, and good results obtained. The proposed antenna shows nearly omnidirectional radiation characteristics, relatively consistent group delays and stable gains in the operating bands. The simple feeding structure, compact size and uniplanar design make it easy to be integrated within portable devices for wireless communication.
TL;DR: An integrated one-class support vector machine (OCSVM) mechanism that is distributed in a SCADA network is presented, as a part of an intrusion detection system, providing accurate information about the origin and the time of an intrusions.
Abstract: Intrusion detection in real-time systems is a problem without a profound solution. In supervisory control and data acquisition (SCADA) systems the absence of a defence mechanism that can cope with different types of intrusions is of great importance. False positive alarms or mistakes regarding the origin of the intrusion mean severe costs for the system. An integrated one-class support vector machine (OCSVM) mechanism that is distributed in a SCADA network is presented, as a part of an intrusion detection system, providing accurate information about the origin and the time of an intrusion. The module reads the network traffic, splits traffic according to the source of the packets and creates a cluster of OCSVM models. These trained models run in parallel and can accurately and fast recognise different types of attacks.
TL;DR: A new tri-level switching method for successive approximation register (SAR) analogue-to-digital converters (ADCs) is presented and achieves a 75% reduction in the total capacitor size, compared with the conventional SAR ADC.
Abstract: A new tri-level switching method for successive approximation register (SAR) analogue-to-digital converters (ADCs) is presented. The proposed switching method enhances the efficiency of digital-to-analogue converter switching energy by 93.7% and achieves a 75% reduction in the total capacitor size, compared with the conventional SAR ADC. In addition, the accuracy of the proposed SAR ADC has no dependency on the accuracy of the mid-level reference voltage (V cm) except in the least significant bit, and the common-mode voltage at the input of the comparator will remain approximately unchanged. Analytical calculations and behavioural simulation results are provided to demonstrate the effectiveness of the proposed switching scheme.
TL;DR: In this paper, a new temperature-stable high bit rate VCSEL was achieved up to a record-high temperature of 85°C with error-free data transmission at 46 Gbit/s and -3 dB bandwidth at room temperature.
Abstract: A new design of oxide-confined 980 nm vertical-cavity surface-emitting lasers (VCSELs) particularly well-suited for very-short-reach (~2 m and shorter) optical interconnects is presented. A new record for temperature-stable high bit rate VCSELs is achieved. Error-free data transmission at 46 Gbit/s is achieved up to a record-high temperature of 85°C. The maximum bit rate and -3 dB bandwidth at room temperature are 50 Gbit/s and 24.7 GHz, respectively.
TL;DR: Simulation shows that the optimal system capacity boundary is achieved by the proposed scheme and D2D communication shows its great potential in increasing system capacity.
Abstract: The bipartite matching strategy is first applied in the graph theory to optimise the resource allocation in a device-to-device (D2D) underlaying cellular network. With each D2D group reusing the resource of one particular cellular user, the proposed scheme minimises the cross-interference between D2D users and traditional cellular users with polynomial complexity. Simulation shows that the optimal system capacity boundary is achieved by the proposed scheme and D2D communication shows its great potential in increasing system capacity.
TL;DR: In this article, a triple-band planar antenna with a compact radiator is proposed for 2.3/3.5 GHz WiMAX and 5.2/5.8 GHz WLAN applications simultaneously.
Abstract: A triple-band planar antenna with a compact radiator is proposed for 2.3/3.5/5.5 GHz WiMAX and 5.2/5.8 GHz WLAN applications simultaneously. The proposed antenna consists of an inverted-L (IL)-shaped radiating element and a parasitic element in the ground plane to generate three resonant modes for triple-band operations. Each of the three resonant bands can be tuned separately to cover other wireless applications also. Owing to the coupling of the IL-driven element and the parasitic element, a compact radiator of 10 × 17.3 mm 2 is realised for triple-band operations. Some key parameters affecting the antenna performance have been analysed using computer simulations. To validate the simulation results, the prototypes of the proposed antenna are fabricated on an inexpensive FR-4 substrate and tested. Good radiation characteristics of the proposed antenna have been obtained. The simulated and measured results are in good agreement.
TL;DR: In this paper, the dependence of oscillation frequency on antenna length in resonant-tunnelling-diode terahertz (THz) oscillators integrated with slot antennas was investigated.
Abstract: A report is presented on the dependence of oscillation frequency on antenna length in resonant-tunnelling-diode terahertz (THz) oscillators integrated with slot antennas. The upper limit of the oscillation frequency was maximised at an optimum antenna length. The highest oscillation frequency obtained in the experiment was 1.55 THz for a 16 μm-long antenna at room temperature.
TL;DR: In this paper, a novel technique for inkjet printing frequency selective surfaces (FSSs) on textiles is introduced, where a screen mask was used so that the interface layer was only printed directly below the conducting ink.
Abstract: A novel technique for inkjet printing frequency selective surfaces (FSSs) on textiles is introduced. The challenge of printing an inkjet layer of 3 μm thickness on polyester cotton with a surface roughness of the order of 150 μm is achieved with a screen-printed interface layer. The conducting inkjet layer is then printed directly on top of the interface layer. A screen mask was used so that the interface layer was only printed directly below the conducting ink. A square FSS structure has been fabricated and the measured shielding has been compared to simulations.
TL;DR: In this paper, a wideband circularly polarised (CP) rectangular dielectric resonator antenna (DRA) based on the concept of a hybrid antenna is presented.
Abstract: A wideband circularly polarised (CP) rectangular dielectric resonator antenna (DRA) based on the concept of a hybrid antenna is presented. In this design, the modified cross-slot simultaneously performs the functions of an effective radiator and the feeding structure of the rectangular dielectric resonator (DR). By properly designing the structure parameters of the DRA, the resonances of the modified cross-slot and the DR can be merged to obtain a wide CP bandwidth. A prototype antenna is designed, fabricated and measured, and a wide 3 dB axial ratio bandwidth of 24.6% is achieved.
TL;DR: In this article, a single-cell tri-band composite right/left-handed (CRLH) resonant antenna is presented, which is designed on a single layer coplanar waveguide-fed based on the T-junction discontinuity equivalent circuit.
Abstract: A single-cell tri-band composite right/left-handed (CRLH) resonant antenna is presented. The antenna is designed on a single-layer coplanar waveguide-fed based on the T-junction discontinuity equivalent circuit. The proposed antenna provides compact size, easy fabrication process, multi-band feature and higher efficiency in comparison with the previously reported CRLH resonant antennas. The single-cell CRLH resonant antenna is fabricated and the measurements are consistent with the simulation result.
TL;DR: In this paper, a metamaterial-based novel compact microstrip antenna is presented for ultra-wideband (UWB) applications, which consists of two layers of metammaterials made by etching a π-shaped slot and crossed-shaped slots, on the radiating patch and the ground plane, respectively.
Abstract: A metamaterial-based novel compact microstrip antenna is presented for ultra-wideband (UWB) applications. The antenna consists of two layers of metamaterials made by etching a π-shaped slot and crossed-shaped slots, on the radiating patch and the ground plane, respectively. The series capacitance and shunt inductance developed due to the patterned radiating patch and ground plane lead to the left-handed behaviour of the metamaterial. The proposed antenna has a compact size of 30.8 × 27.6 × 0.8 mm3 and is fed by a 50 Ω microstrip line. The impedance bandwidth (−10 dB) is from 3 GHz to more than 14 GHz with maximum radiation in the horizontal plane and tends towards a directional pattern as the frequency increases.