A wideband tri-port multiple-input-multiple-output (MIMO) antenna designed for worldwide interoperability for microwave access (WiMAX) and wireless local area network (WLAN) applications is presented. The proposed antenna is composed of three printed dipoles with an integrated balun, the size of which is only 0.08λ ². By introducing ground stubs between adjacent elements, impedance matching is improved and mutual coupling is reduced. A bandwidth of 51.6% (2.30–3.90 GHz) with S ₁₁ <−10 dB and S ₁₂, S ₁₃ <−10 dB is achieved, which can cover the whole three WiMAX bands and the 2.4 GHz WLAN band. Moreover, directional radiation patterns are achieved in these bands, and the average gain reaches 3.5 dB with up to 21.4 dB front-to-back ratio. The envelope correlation coefficient is below 0.038, which can provide good pattern diversity for a MIMO system.

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 mm². 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.

A novel frequency reconfigurable bow-tie antenna array for Bluetooth, worldwide interoperability for microwave access (WiMAX) and wireless local area network (WLAN) applications is presented. This array comprises four double-sided bow-tie elements and an ultra-wideband feed network. By controlling the states of the pin diodes loaded on the radiators, the effective electrical lengths of bow-tie elements can be changed, thus the operating band of the array can be electronically switched between three different frequency bands. A prototype was fabricated and measured, and the results are in good agreement with the simulations, which shows that this array is a good candidate for multi-radio wireless applications.

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.

A compact patch antenna periodically loaded by air gaps is presented. The gaps are arranged to create EBG cells, which affect the dispersive behaviours of the patch (as a transmission line). This causes waves to travel faster along the patch, and increases the cumulative radiation from the structure. The proposed antenna is compared with its conventional counterpart, considering the efficiency, electrical/physical size and the potential to achieve an electrically small footprint. Experimental results validate the analyses.

Feature selection is important and necessary for disease classification and prediction using high-dimensional gene expression data. A hybrid method integrating sparse representation with a two-sample statistical t-test to construct features from high-throughput microarray data is presented. The approach takes account of gene interaction and reduces the variable dimension by sparse linear combination, as well as considers the discriminative power of genes using component regression. Under the recurrent independence rule for classification, the experiment results on real data demonstrate the improvements of this hybrid technique over conventional methods.

An information-enhanced sparse binary matrix (IESBM) is proposed to improve the quality of the recovered ECG signal from compressed sensing. With the detection of the area of interest and the enhanced measurement model, the IESBM increases the information entropy of the compressed signal and preserves more information during compression; thus, it guarantees a high-quality recovery. The experimental results indicate that the proposed matrix is suitable for compressed sensing of the ECG signal with small distortions in both overall and the concerned diagnostic segments.

In-vivo electromagnetic field distributions of biological systems can be imaged from the measured magnetic flux density of magnetic resonance-based electrical impedance tomography (MREIT), which was induced by the externally injected current through a pair of electrodes. Since the electromagnetic field is affected by the injected current and electrical conductivity of biological tissues, the electrode type and position are important factors for determining the voltage and current density distribution. Using a three-dimensional finite element model, the current pathway and electric field distribution to optimise the electrode configurations in liver MREIT are estimated.

Two dual memristive circuits are presented, the steady-state responses of which are periodic sequences of mixed-mode oscillations (MMOs) of type L ₁ ^S₁ L ₂ ^S₂ …L _n ^s_n where L_k and s_k are integers for k = 1, 2, …n. The L_k and s_k are the numbers of large- and small-amplitude oscillations, or LAOs and SAOs, respectively. This new feature of memristive circuits is illustrated through several MMO responses, all with the pinched hysteresis characteristics for both LAOs and SAOs. The mode-locking phenomenon for MMOs is also discussed. The MMO sequences depend on initial conditions and parameters of the circuits.

The effect of transconductor even-order nonlinearity in combination with the tank common-mode impedance on the upconversion of 1/f noise in LC-tuned oscillators is investigated. It is demonstrated that by suitably designing the imaginary part of the tank common-mode impedance, the transconductor 1/f noise upconversion is suppressed. The presented analysis is verified by simulation results, and practical implementation issues are considered.

The real-time navigation problem of a holonomic mobile robot in dynamic environments is addressed. The robot's footprint and obstacles are approximated with the smallest enclosing ellipses, known as the Löwner-John ellipses. The robot avoids collisions with obstacles by selecting a translational velocity outside of the ellipse-based velocity obstacle (EBVO) described in this Letter at each time step. Furthermore, the rotational velocity of the robot is controlled to gradually change the EBVO so that the robot can efficiently reach the destination. Finally, the proposed algorithm is demonstrated through simulations.

Automatic marker selection for watershed segmentation is a difficult problem. Most of the existing procedures are intended for specific application fields and usually require some prior knowledge about the problem at hand. A simple and general method for generating markers is proposed. The markers are obtained from the splitting of the three-dimensional (3D) colour histogram of the image and imposed as minima for watershed segmentation. The method has been tested on natural images from the Berkeley segmentation dataset (BSDS500), showing results comparable with the state-of-the-art segmentation algorithms.

An important question, that is whether for the subjective evaluation of three-dimensional (3D) video can be performed on one type of 3D monitor only or whether multiple types of displays are required in order to obtain reliable results, is answered. The experimental material used in this reported work includes mean opinion score (MOS) data collected on two types of monitors: polarisation and autostereoscopic. An analysis of this data is reported. The observed high correlation of the gathered quality metrics clearly indicates that the results obtained using the polarisation monitor are as statistically significant as the results obtained using the autostereoscopic one. Therefore, to save time, only one type of monitor can be used.

Spatial diversity assists parameter estimation in distributed networks. A sparsity-aware link combination strategy is proposed, which considers both the spatial sparsity in a network and the inherent sparsity of the system, where two types of zero-attracting adaptive combiners are proposed based on the least-mean-square the algorithm. The proposed algorithms exploit l ₁-norm regularisation through adaptive combination of neighbouring node weights such that the proposed algorithms can adaptively track the variations of the network topology. Simulation results illustrate the advantages of the proposed link combination algorithm in terms of convergence rate and steady-state performance for distributed sparse system learning.

An integrated humidity sensor capable of passive wireless sensing through inductive coupling is presented. The sensor chip consists of two stacked counter-rotating planar aluminium inductors (0.5 μm thick, 100 μm in width, 50 μm space and 6 mm outer diameter) separated by a maskless polyimide film. The two inductors are inductively and capacitively coupled together to form a resonant tank, whose resonant frequency changes with humidity. This topology eliminates the need of a connection bridge or via as used in the usual inductor–capacitor humidity sensors and offers higher sensitivity due to the inner humidity-sensitive parallel-plate capacitor in contrast with the single-layer self-resonant inductor. Three sensor devices with different inductor turns were fabricated and characterised. Measurements show a sensitivity of 45 kHz/%RH with a centre frequency of 50.5 MHz for sensor A (8 turns), 15.8 kHz/%RH, 22 MHz for sensor B (10 turns) and 65 kHz/%RH, 74 MHz for sensor C (4 turns).

Recent developments in the technology of printing magnet field domains offer a whole new field of applications. Highly customised magnetisation patterns can now be generated which enhance significantly the magnetic properties and behaviour. Magnets with specific printed magnetic field patterns can also be used for enhancing diamagnetic levitation applications. This reported work demonstrates the diamagnetic levitation of pyrolytic graphite over a monolithic NdFeB cylinder magnet with printed magnetic field domains. Using monolithic magnets instead of magnet assemblies for diamagnetic levitation allows easier, faster and cheaper production of diamagnetic levitation tracks or diamagnetic bearings. Furthermore, one can build the diamagnetic levitation tracks, which otherwise are difficult or impossible to be realised using prior art technologies.

A method to perform fast transient simulations of interconnects by modelling the impulse responses of the S-parameters as discrete impulses, and then retaining only those with significant magnitudes has recently been shown to be faster than the present state-of-the-art method of curve fitting to a rational function model. An improvement to the fast convolution method by first optimising the choice of reference impedance used in the dataset is proposed. The method is seen to yield computational savings while retaining the accuracy.

A 0.01–20 GHz inline capacitive radio frequency (RF) power sensor with a floating microelectromechanical system (MEMS) beam is proposed. It is based on sensing the capacitance change of the MEMS beam above the coplanar waveguide line due to the electrostatic force. In the design, anchors of the MEMS beam are floating for accurate capacitive detection and flexible for increasing the sensitivity, and an impedance matching technique is utilised to improve the microwave performance. The fabrication of this sensor is compatible with the GaAs monolithic microwave integrated circuits (MMICs) process. The measured reflection loss of the capacitive sensor is <−18 dB, whereas the insertion loss is better than −0.38 dB up to 20 GHz. Experiments show that approximate linear relationships between the measured capacitance change and the input RF power are obtained, and the resulting average sensitivities are 120.8, 76.7, 87.6 and 61.0 aF/mW at 5, 10, 15 and 20 GHz, respectively.

A novel pulsed depressed collector biasing scheme is proposed. This topology feeds forward energy recovered during one RF pulse for use on the following RF pulse. The presented ‘inverse’ Marx charges biasing capacitors in series, and discharges them in parallel. Simulations are shown along with experimental demonstration on a 62 kW klystron.

A bandpass filter (BPF) with a central frequency of 2.31 GHz for future worldwide interoperability for microwave access (WiMax) applications using integrated passive device technology is presented. To realise the BPF, an interdigital capacitor is integrated between the two divisions of a square-shaped spiral inductor. To achieve a compact size, the capacitor is fully embedded inside the inductor. Additionally, the coils of the inductor are intertwined to utilise enhanced mutual inductance for minimising the loss of signal transmission. The strong electromagnetic coupling between the source and load through the interdigital capacitor results in excellent bandpass skirt selectivity with a measured return loss of 26.1 dB. Moreover, it provides an improved stopband response due to the presence of a transmission zero at 5.94 GHz.

Owing to the fact that the conventional compact two-dimensional (2D) precise integration time-domain (CPITD) method ignores the attenuation along the propagation direction for lossy invariant transmission lines, the calculation results are unsatisfactory. To extract the exact attenuation constant, a novel CPITD method that considers the attenuation constant along the propagation direction and describes an iterative process to seek out the attenuation constant is proposed. Compared with previous research related to the compact 2D finite-difference time-domain (CFDTD) method, the analytical or approximate analytical solution of the attenuation constant as the initial input value is used followed by the golden division method to find the interval of the exact attenuation constant in the iterative process. Numerical experimentations validate that the results of the novel method are much more accurate than those of the conventional CPITD method. Furthermore, the proposed method is of higher computational efficiency than the CFDTD method.

The Doherty power amplifier has the most attractive architecture to improve the efficiency for amplifying a signal with a high peak-to-average power ratio. However, the ideal Doherty operation is difficult to be achieved because the g _m of the peaking amplifier should be two times larger than that of the carrier amplifier. The g _m mismatch between the carrier and peaking amplifiers hinders the proper load modulation at the peak power region. The Doherty power amplifier with an auxiliary drive cell for the peaking amplifier is introduced to solve the problem. The auxiliary peaking cell drives the main peaking amplifier with higher input power, solving the gain and output power reduction problem. Experimental results show that the proposed Doherty power amplifier can enhance gain, output power and power-added efficiency.

A sensor array employing the distributed Bragg reflector (DBR) fibre laser is presented. This array could be utilised as a multi-channel multi-functional detector for bending radius, transverse load and axial strain by simultaneously monitoring the lasing wavelength and the output beat note frequency. The measurement theory of the DBR fibre laser is explained, and it is then experimentally verified with a three-probe array. The system's detection sensitivities for curvature, transverse load and axial strain are found to be 600 MHz/cm⁻², 1.3 MHz/g and 1.263 pm/με, respectively.

The first monolithically integrated laterally coupled, multi-wavelength distributed feedback (DFB) laser array using first-order sidewall sampled gratings with equivalent quarter-wave phase shifts defined by interference lithography is experimentally demonstrated. The elements of the monolithic DFB laser array lase strongly monomode, with an average side mode suppression ratio of ∼37.3 dB and with a uniform wavelength spacing of ∼7.3 nm. The output power under 100 mA bias current ranges from 11.4 to 14.1 mW. The proposed method offers a practical and low-cost method for the fabrication of multi-wavelength monolithic DFB laser arrays without regrowth or e-beam lithography.

The magneto-optical absorption in ‘spherical’ quantum dots ‘completely’ confined by a harmonic potential and exposed to an applied magnetic field in the symmetric gauge is investigated. This is done within the framework of Bohm–Pines’ random phase approximation (RPA) that enables us to derive and discuss the full Dyson equation that takes proper account of the Coulomb interactions. Intensifying the confinement or magnetic field and reducing the dot-size yields a blue-shift in the absorption peaks. However, the size effects are seen to be predominant in this role. The magnetic field tends to maximise the localisation of the particle, but leaves the peak position of the radial distribution intact. The intra-Landau level transitions are forbidden.

The reliability of p-type ZnO thin films obtained by phosphorus implantation, using plasma-immersion ion implantation, followed by rapid thermal annealing is reported. Also reported is the fabrication of a ZnO-based homojunction light-emitting diode. Low-temperature photoluminescence measurements after six months showed a dominant free electron-to-acceptor peak for samples annealed at 900 and 1000°C, confirming the formation of p-type films. Room-temperature electroluminescence spectra for the p-ZnO:P/n-ZnO homojunction diode revealed ultraviolet (UV) emission at 3.18 eV; however, the dominant peak was observed at 1.8 eV because of a deep-level defect peak. Achieving dominant UV emission requires further optimisation of the device structure.

Dynamic power management (DPM), which exploits low-power states of the target device, has been a key research issue to overcome the limited battery life of mobile devices. For efficient power management, today's power management unit in a system-on-chip for mobile devices supports multiple low-power states for embedded processors. Unfortunately, the DPM policies implemented in modern operating systems are not appropriate for processors because they may not understand the idleness of the processor accurately. There may be significant performance degradation if the DPM policy module misunderstands that the processor is idle even when there are many interrupt requests to handle. A novel DPM scheme for embedded processors considering the system response time as well as power reduction is proposed. Experimental results show that the proposed DPM policy achieves performance improvement by up to 25% compared to a conventional DPM policy with a similar amount of power reduction.

An average current-sensing circuit integrated in a hybrid DC–DC buck converter is presented. Both the high-side and the low-side switch currents are fully sensed by detecting the filtered smooth voltage of the switch node, which maintains a substantially constant mode changing point and seamless transition between pulse width modulation (PWM) and pulse frequency modulation (PFM) under various duty cycles. The achieved mode changing point is almost independent of temperature and supply voltage. The proposed circuit is suitable for high-frequency hybrid DC–DC applications.

Wind power plants connected to power systems are often unable to utilise all available power due to transmission constraints. This problem is illustrated in an optimal power flow problem to schedule power from two different wind plants in a 6-bus system. A cost function is proposed to schedule wind power in an unbiased manner.

Proposed is a speckle reduction method for synthetic aperture radar (SAR) images. This method can be considered as a new adaptive non-local (NL) means filtering technique since different weights based on Euclidean distance and coefficient variation (CV) of SAR images are applied. The Euclidean distance of similarity windows and CV of the search window can be calculated first; next, the decay parameter will be adjusted by the CV; then, the speckled-image pixel will be restored by weighted averaging based on the new weight. The visual and numerical experimental results show that the proposed filter can suppress speckle effectively and keep details (such as edge and texture) simultaneously. The proposed filter outperforms the existing state-of-the-art de-speckling filters based on NL means in terms of runtime.

New methods for reducing signal distortion in interferometric angular velocity measurements are introduced. Two waveform approaches are proposed: long-wavelength signals and short-pulse signals. The source of nonlinear distortion is derived and analysed, and the strengths and drawbacks of each method are discussed. Although the focus is on the distortion generated when measuring the angular velocity of walking humans, the results are applicable to interferometric measurements of the angular velocity of non-rigid or multiple objects in general.

Based on the kernel canonical correlation analysis (KCCA) and the ambiguity function (AF) description of radar signals, a novel hybrid fusion method for specific radar emitter identification is proposed. The near-zero Doppler slices of the AF are firstly encoded by the corresponding kernel matrices. Then, these kernels are divided into two groups and a uniform combined kernel is calculated for each group, which contains the idea of kernel-level fusion. Given the two integrated kernels, KCCA is employed to extract the discriminative features for classification, which is a common feature-level fusion method. The proposed method can not only avoid searching for the representative Doppler slice of the AF (AFR), but also obtain better performance than the AFR because of the information fusion strategy. Finally, the experimental results on two real radar data demonstrate the validity of the proposed method.

A subspace-based auto-paired range and direction-of-arrival (DOA) estimation algorithm without joint diagonalisation for multi-target detection of dual-channel frequency modulated continuous-wave (FMCW) radar are proposed. The proposed method, which is based on signal subspace, exploits the shift invariant structure of the stacked Hankel matrix for the paired range and DOA estimation of multiple targets. To verify the effectiveness of the proposed method, the dual-channel FMCW radar is implemented and its effectiveness verified in an anechoic chamber environment.

An AlGaN/GaN metal–oxide semiconductor (MOS) high-electron mobility transistor (HEMT) on silicon substrate was obtained with 8 nm Al₂O₃ gate dielectric films grown using atomic layer deposition. The MOS-HEMT shows a low specific on-resistance of 0.57 Ω·mm², a large maximum saturate drain current of 12.5 A and a minimal threshold hysteresis of 0.05 V. Low specific on-resistance, large maximum saturate drain current and minimal threshold hysteresis show that the fabricated MOS-HEMT is very suitable for power switching applications.

A stepped-impedance cross-structure (SICS), consisting of a centre rectangular patch loaded with two pairs of stubs, is proposed for the designing of a wideband superconducting diplexer. Each pair of the stubs is designed for one channel of the diplexer, and is coupled by the centre rectangular patch with a strong coupling property required by the wide bandwidths. The frequencies and the coupling strengths of the two pairs of the stubs can be controlled independently. A superconducting diplexer has been successfully designed and fabricated with the proposed structure. The two channels are centred at 2.9 and 5.8 GHz with fractional bandwidths of 26.9 and 24.5%. The measured results of the fabricated device show low insertion losses and high isolations and agree well with the simulated ones.

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.