A compact dual-band pattern reconfigurable antenna using switched parasitic array is proposed for 2.4 and 5.8 GHz wireless MIMO applications. The proposed antenna is based on dual-band driven and parasitic radiators (PR) with RF switches. The PR performs as a reflector or a director by controlling RF switches. The antenna is designed to provide nine radiation patterns in three states at the frequencies of 2.4 and 5.8 GHz bands, respectively. Two states realise eight radiation patterns in the horizontal plane. The measured peak gain of all radiation patterns ranges from 6.1 to 9.7 dBi. Another state generates omnidirectional radiation patterns in the horizontal plane and measured gains of around 4.0 and 7.5 dBi for 2.4 and 5.8 GHz bands, respectively.

This Letter presents a computer-aided methodology for automated obstructive sleep apnoea (OSA) detection using the proposed symmetrically weighted local binary pattern (SLBP)-based features. The SLBP, which is a variant of one-dimensional local binary pattern (LBP), generates a binary pattern by making comparisons in the left and right neighbourhood of a sample. However, as opposed to LBP, the generated binary information is encoded into decimal value by using a symmetric weighting scheme. The proposed encoding scheme helps to reduce the length of the feature vector significantly. Experimental evaluations on the Physionet sleep apnoea single-lead electrocardiography signals suggest that the proposed SLBP features are effective in detecting OSA with an accuracy of 89.80%. Our results also show that the proposed SLBP achieves a good trade-off between the classification and computational performance among different variants of LBP. Further, the proposed approach outperforms recently proposed methodologies for OSA detection.

A novel paradigm for building code modulated visual evoked potential (cVEP) brain–computer interfaces (BCIs) is proposed. The paradigm is based on grouping modulation of stimuli with different codes in order to increase the number of stimuli and resulting information transfer rate (ITR). In a single group, an original code and its circularly shifting codes are used for modulating 16 stimuli. To achieve good separability of stimuli, the original codes for different groups should have good autocorrelation and cross-correlation properties. A pair of Golay complementary series and an almost perfect autocorrelation sequence are used as the original codes to implement a three-group cVEP BCI with 48 targets. Four subjects participated in a simulated online experiment and a high ITR of 129.58 bits/min was achieved due to the sharp increase of the number of targets.

A novel framework based on partial least squares (PLS) and multivariate empirical mode decomposition (MEMD) is proposed to effectively evaluate heart rate from webcam videos captured during illumination changing conditions. The framework takes the assumption that both facial region of interest (ROI) and background ROI have the similar illumination variations and the background ROI can be treated as the denoising reference by using PLS to extract the underlying common illumination variation sources existing in both ROIs. Then, a number of intrinsic mode functions are decomposed by applying MEMD to the illumination-variation-suppressed facial ROI and the HR is evaluated. Compared to the experimental results obtained by the recently proposed independent component analysis and the ensemble empirical mode decomposition methods, the proposed method led to a better agreement with HR ground truth (the mean bias was 3.4 bpm with 95% limits of agreement ranging from −13.2 to 19.9 bpm), indicating a promising solution for the realistic HR estimation remotely.

Non-invasive blood glucose measurement has attracted great interest from researchers deploying various techniques where microwave sensing is one of them. Microwave resonators are utilised as sensors for measuring the glucose levels. A body part is placed on the sensor for a reading and the measurement principle lies in the change of the dielectric properties of blood with varying levels of glucose. The fingertip is a popular measurement site as there is a good amount of fresh blood supply. The position of the fingertip on the sensor has an effect on the sensor response due to the change in the propagation path of the EM field inside the finger. Moreover, fingerprints also affect the sensor response as the irregular ridges and valleys in the fingerprint introduce air gaps altering the effective permittivity seen by the sensor. The effects of fingerprints as well as finger positioning on the sensor is explored and explained.

Lung vessel segmentation of computed tomography (CT) images is important in clinical practise and challenging due to difficulties associated with minor size and blurred edges of lung vessels. A vessel segmentation method is proposed for lung images based on a random forest classifier and sparse auto-encoder features. First, the multi-scale representations of lung images are obtained using the Gaussian pyramid. Second, a sparse auto-encoder of three layers is trained using randomly selected patches of these images. Next, the trained weight of the sparse auto-encoder is used as the convolution kernel to extract features of different scale images. Finally, a random forest classifier is exploited to segment the vessels. The proposed method was evaluated on the original and noise-added VESSEL12 dataset that is publicly available. Comparison with some classical methods and existing machine learning methods shows that the proposed method reaches the state-of-the-art accuracy. The results also show that a shallow neural network is a powerful feature extraction tool.

Waveform distortions generated by exercise cause erroneous predictions in human identification based on the electrocardiogram (ECG). An approach for the ECG-based identification to achieve accurate predictions while exercising is proposed. In the proposed scheme, passband of a band-pass filter is optimised to compensate for the distortion. As a result, the proposed scheme archives 100% identification accuracy is revealed when the subject is resting and 99.7% during exercise. The investigation is an important building block in the development of robust ECG-based identification systems that are consistently accurate despite significant ECG waveform variation due to exercise.

A self-adjusting sensing circuit spin-torque transfer magnetic random access memory (STT-MRAM) is proposed. STT-MRAM is considered to be the most promising candidate among the new emerging memories. However, read performance has emerged as a new bottleneck, because of its low tunnelling magneto-resistance ratio (TMR) and low read current. The proposed self-adjusting sensing circuit shows an improved sensing margin, overcoming the weaknesses of the STT-MRAM. The proposed circuit using Verilog-A model, a 65 nm complementary metal–oxide–semiconductor process also evaluated, and Monte Carlo analysis. The results of analysis show that the proposed circuit ensures a certain sensing margin, which is more than 200 mV in TMR 150% and about 50 mV in TMR 100%.

A new four-dimensional hyperchaotic oscillator is proposed. Non-linear dynamic analysis of the hyperchaotic oscillator is presented. Furthermore, an analogue circuit of the hyperchaotic oscillator is implemented on a chip for some relevant engineering applications such as information encryption. The entire chip area occupies 0.69 × 0.84 mm in 0.35 μm CMOS process with power dissipation of 475 mW from a 3.3 V supply voltage.

Novel finite impulse response architectures for wide passband droop compensation of cascaded integrator-comb filters are presented. Compared with the recent wide-band compensators introduced in the literature, the proposed systems achieve better passband droop correction with lower power dissipation, lower hardware utilisation and higher maximum frequency of operation, as validated with post-place-and-route information from FPGA-based implementations.

Pipelining a combinational logic data-path without introducing pipeline stage delay imbalance is a key requirement for efficient digital processing. Balanced pipelining is easily achieved by simple logical effort optimisation when the interconnect and fan-out delay overhead is small and homogeneously distributed. When the target micro-architecture design includes isolated long interconnects, such as buses, optimal pipeline stage balancing becomes a tricky problem. This work formalises the solution based on the logical effort paradigm and evidences its advantage with respect to a heuristic approach.

This reported work addresses a collaborative approach to path planning in continuous space for the energy constrained robot collection problem. The objective is to minimise the overall duration the mobile robots return from where the given tasks are completed. For time- and energy-efficient collection, the authors use a large-scale ground vehicle that can load and transport relatively small mobile robots. However, determining time-optimal collection locations requires too much computation in this problem setting. Therefore, a heuristic algorithm for a set of mobile robots is proposed and verified through simulations.

An efficient approach to image segmentation that approximates the piecewise smooth (PS) functional in Vese and Chan (2002) with explicit solutions is presented. By rendering some rational constraints on the initial conditions and the final solutions of the PS functional, the authors propose two novel formulations which can be approximated to be the explicit solutions of the evolution partial differential equations (PDEs) of the PS model, in which only one PDE needs to be solved efficiently. Furthermore, an energy term that regularises the level set function to be a signed distance function is incorporated into our evolution formulation, and the time-consuming re-initialisation is avoided. Experiments on synthetic and real images show that the method is more efficient than both the PS model and the local binary fitting (LBF) model, while having similar segmentation accuracy as the LBF model.

Feature redundancy-reduced convolutional neural network (FRR-CNN) is proposed to address the problem of facial expression recognition. Different from traditional CNN, convolutional kernels of FRR-CNN is induced to be divergent by presenting a more discriminative mutual difference among feature maps of the same layer, which results in generating less redundant features and yields a more compact representation of an image. Furthermore, the transformation-invariant pooling strategy is used to extract representative features cross-transformations. Extensive experiments are conducted on two public facial expression databases and the obtained results demonstrate the efficiency of FRR-CNN comparing with the state-of-the-art expression recognition methods.

It has been demonstrated that the bilateral filter can be computed using a series of fast convolutions by approximating its Gaussian range kernel using trigonometric functions. A novel approximation that can be applied to any range kernel is proposed. Specifically speaking, an exponential sum is exploited to approximate the range kernel of the bilateral filter, where the coefficients of the exponential basis are computed by solving a set of linear equations. The major advantage of the method is that the tradeoff between the run-time and the filtering accuracy can be controlled by the cardinality of the exponential basis. Experiments show that the method achieves state-of-the-art results in terms of accuracy and speed.

For person re-identification, traditional accelerated gradient algorithm-based metric-learning approaches suffer from the fixed weight and degrade the match performance. To this end, a novel and efficient method is proposed to learn the weight and metric jointly. Moreover, an optimised proximal gradient algorithm approach is adopted to further speed up the convergence rate. Simulation results verify the superior performance of the proposed method.

The orthogonal Jacobi polynomials are not suitable for the characteristic function in the continuous- and discrete-time filter designs because they are not fulfilling the basic conditions: to be pure odd or to be pure even. A simple modification of Jacobi polynomials, proposed in this Letter, is performed to obtain a new filter approximating function. Magnitude frequency responses of obtained filters exhibit more general behaviour compared to that of classical Gegenbauer (ultraspherical) filters, due to one additional parameter available in the Jacobi polynomials. This parameter can be used to obtain magnitude response with smaller passband ripple values (nearly monotonic behaviour), smaller group delay variations or sharper cutoff slope. The proposed modified Jacobi polynomials are not orthogonal; however, many known orthogonal polynomials can be obtained as theirs special cases.

A novel statistical model for real-time traffic flow prediction is proposed. In this study, a 3D Markov random field (MRF) is used to model the temporal dynamics of the traffic flow measured by VDS sensor network. Then, the spatial and temporal relations between roads at a given location are represented by the 3D graph using cliques, then its structure is determined by clique parameters. Here, a support vector regression is adopted for estimating the correlation parameters. The technique is applied to actual traffic flow data from Gyeongbu expressway, South Korea. The experiments demonstrate that the proposed method can predict the traffic flow with an accuracy of 85.6%, which improves 17.3% of the existing state-of-the-art method.

Radio networks consisting of multiple listen before talk devices are analysed. New formulas for network throughput and success probability of a transmission are derived based on Markov renewal theory. The accuracy of our formula against the existing results is validated by simulation.

An unreliability-based information bit flipping (UIBF) decoding using cyclic redundancy check is proposed to lower the error floors of high-rate systematic low-density parity-check (LDPC) codes. Unsuccessfully decoded codeword is redecoded by the UIBF decoding with very low complexity at the end of every iteration of the sum–product (SP) decoding. The proposed scheme is applied to LDPC codes of the IEEE 802.16e standard. Simulation results show that the proposed scheme effectively lowers the error floors of systematic LDPC codes with smaller number of iterations compared with the conventional SP decoding scheme, which leads to the reduced power consumption and increased data throughput.

A passive microwave substrate-integrated waveguide (SIW) resonator humidity sensor using black phosphorus (BP) as sensitive layers has been presented. The proposed structure consists of an SIW cavity resonator operating at S-band and a folded sensing slot opened on the top plane. The humidity sensing performances of the proposed sensor were tested in the relative humidity range of 11–97%. Compared with an SIW resonator without BP sensitive layers, the sensitivity of the proposed SIW sensor with BP nanosheets significantly increased about 40 times.

A pH-sensitive sensor with a differential mode was developed to detect surface charges accumulated on the ion-sensitive layer. The device accurately monitors the relative pH value using the modified instrumentation amplifier with the DC electrode-offset compensation. The readout voltage is digitalised with the current-starved ring oscillator. The sensor achieves the DC offset compensation of 22.5 dB and the oscillating pH sensitivity of 1.3 MHz/pH. The feasibility of the sensor is demonstrated to monitor the hydrogen ion concentration comparing the oscillation frequency at differential mode with that at single mode.

A compact balanced bandpass filter (BPF) by using the isosceles right triangular patch resonator is presented. Stemming from the mode degeneration properties of the square patch resonator with single excitation located at its corner, the specific current distribution on this square patch resonator is investigated. Based on that, a new type of half-mode square patch resonator named as the isosceles right triangular patch resonator is derived and proposed. Afterwards, resonant properties of the new patch resonator under different excitation forms are also investigated. Subsequently, balanced BPF has been implemented by adopting appropriate coupling structure among four isosceles right triangular patch resonators. Finally, to verify the design concept, a second-order Chebyshev balanced BPF centred at 2.44 GHz with 3 dB fractional bandwidth of 6.15% is designed and fabricated. Good agreement can be observed between the simulated and the measured results.

A novel tri-section stepped-impedance resonator (SIR) filter with controllable mixed electric and magnetic cross coupling is proposed. Two quarter-wavelength shorted-end SIRs and one half-wavelength SIR are used to realise tri-section topology. The electric and magnetic couplings in mixed cross coupling can be controlled by the inter-digital capacitor structure and the gap between shorted lines, respectively. Then, additional transmission zeros can be obtained for better frequency selectivity and high rejected level in stopband. One filter sample is designed and fabricated with single-layer PCB. Good agreements are achieved between the measured and simulated S-parameters.

A microstrip filter element that is tunable through magnetic repositioning of a ferrofluid load is presented. A channel beneath the microstrip stub is partially filled with ferrofluid which moves in response to a DC bias field placed beneath the ground plane, resulting in a changing impedance and propagation constant for the stub section and tuning of the filter element. Benefits of this tuning method include electrical isolation between the tuning system and the filter element, retention of the device's operating mode without the need for a power source, and microfluidic reconfiguration without a pumping system.

This Letter presents a novel CMOS transceiver for short-reach multigigabit communication over step-index plastic optical fibre (SI-POF), a very interesting transmission medium for industrial and home-end applications due to its low cost, ease of handling and inherent immunity to electromagnetic interference. The transceiver uses amplitude duobinary modulation, which is added to continuous-time equalisation. For that purpose, a duobinary precoder and a duobinary decoder have been fabricated in a standard 0.18-µm CMOS technology, consuming only 28.4 mW. The system enables a 50-m SI-POF channel bandlimited to 100 MHz to operate at a data bit rate of 3.125 Gbit/s.

The performance of a typical free-space optical link using a recently proposed composite model for turbulence and pointing error effects is studied. This model offers analytical tractability in the statistical description of the above phenomena and was derived using the mixture Gamma distribution for turbulence. New analytical derivations of the outage probability and bit-error rate for some binary modulation schemes are presented in closed form.

The kink effect at a very low voltage (∼1.15 V) region is reported in the electrical characteristics of a back-gated thin film transistor fabricated by embedding a TiO₂ (T) layer between two Al₂O₃ (A) layers grown on a p-Si substrate using electron beam evaporation. A layer of ZnO quantum dots (QDs) deposited on the A–T–A structure by the sol–gel method is used for charge transportation between the source and drain electrodes grown on the ZnO QDs layer. The effect of TiO₂ is analysed for the charge trapping and possible occurrence of the kink effect.

Kerr optical frequency combs and optoelectronic oscillators are microwave photonic systems that can generate ultra-pure radio-frequency signals in the gigahertz range. We comparatively investigate the phase noise performances of both microwave generators and analyse as well their specific spectral features.

A T-slot waveguide optical interconnect is proposed that can be realised on a photonic integrated circuit with sub – wavelength silicon slot waveguides and can redirect optical power to optical devices placed perpendicular to each other. In the proposed configuration, all critical parameters of high index waveguide and low index slot of all three arms are optimised. A power splitting efficiency of 54% is achieved which is almost independent of operating International Telegraph Union (ITU) grid C Band wavelengths. By judicious modification in T-slot waveguide configuration, power splitting efficiency is enhanced up to 73%.

The characterisation of surface roughness is important in process control and metrology. A simple, low cost sensor which can be used for this measurement is one based on laser optical feedback interferometry. A target containing samples of similar abrasive paper with different levels of roughness was characterised using a sensor based on this technique, and the resulting measurements show that the standard deviation of the optical feedback signal was proportional to the roughness of the surface.

The 3-level boost (3LB) converters have the characteristics of higher-voltage conversion ratio and efficiency, lower inductor current ripples, output voltage ripples and voltage stresses on switches when compared with the conventional boost converters in continuous conduction mode (CCM). When implemented into an integrated circuit, the 3LB converter discontinuous conduction mode (DCM) operation cannot be avoided due to a smaller inductance. Its DCM operation analysis is deduced including CCM/DCM boundary, DCM voltage gain and DCM small signal transfer function. The deduced DCM operation theory is verified using MATLAB and Cadence, to obtain a feasible DCM closed-loop controller design in future.

A test circuit for modular multilevel converter (MMC)-based voltage-sourced converter valves in high-voltage direct current (HVDC) system is dealt with. The proposed scheme has an ability to provide a submodule current having DC component as well as AC component to represent real operating condition of HVDC transmission system. There is no need of extra power supply to provide the DC current component because the scheme has inherent circulating DC current between rectifier and inverter valves. Therefore, only one small power rated DC power supply is necessary. Experiments are carried out to show the validity of the proposed test circuit.

Signal acquisition has become the performance bottleneck of global navigation satellite systems (GNSS) receivers in harsh interference environments due to its low sensitivity. In this Letter, a novel anti-jamming algorithm based on the minimum mean square error criterion is proposed to protecting the acquisition stage. The key idea behind the proposed method is that the grid search process of synchronisation parameters is shared by both interference suppression and signal acquisition. Simulation results indicate that the proposed method is capable of maintaining the functionality of GNSS receivers at cold start in the presence of interfering signals. In addition to this, its performance outperforms the power inversion method significantly.

A low complexity multiple signal classification (MUSIC)-based angle estimation method in monostatic multiple-input multiple-output (MIMO) radar has been proposed. To reduce the computational burden and maintain the accuracy of solution, the beam-space reduced-complexity MUISC algorithm is developed for monostatic MIMO radar. As the results, the lower computational cost and higher angle resolution in pseudo spectral domain have been obtained. Some simulation results have been given to show the effectiveness of the proposed method.

In high-frequency hybrid sky-surface wave radars, the spread-Doppler clutter (SDC) compromise low-velocity target detection performance. Generally, adaptive filter methods achieve clutter suppression by estimating a clutter-plus-noise covariance matrix from target-free training data, which are typically obtained from neighbouring range bins. Under certain circumstances, the clutter statistics change significantly across adjacent bins. To deal with this problem, a single dataset algorithm is proposed to suppress the SDC without secondary data. Firstly, a spatial orthogonal projection matrix is introduced to block the target component in the cell under test. Afterwards, a localised processing method is derived, using previously constructed clutter samples, to suppress the SDC. According to the experimental results, the proposed method can achieve better clutter suppression performance based on real data.

This Letter presents a 60 GHz low power low noise amplifier (LNA) with high g _m × R _out transconductor stages in a 65-nm complementary metal oxide semiconductor (CMOS) technology. Different from the cascode and current-reused common source–common source (CS–CS) structure, the new transconductor proposed in this Letter comprises a CS transistor whose DC current is shared by other two transistors. With this configuration, the equivalent transconductance, g _m and output resistance, R _out of the transconductor are both high while its noise figure is deteriorated slightly comparing with CS structure, making it suitable for low-power LNA circuits. From the measurement results, the LNA gets a gain of 13.4 ± 1.5 dB and 3-dB bandwidth of 16.7 GHz (48–64.7 GHz). The average noise figure of the LNA is 6.1 dB with a power dissipation of 9.6 mW under 1 V power supply.

A cascaded integrator–comb (CIC)-based decimator is proposed, which consists of an area-efficient structure aided with an embedded simplified Chebyshev-sharpened section. Taking traditional CIC filters as a reference, the proposed scheme fulfils two important goals: (i) it improves the worst-case aliasing rejection and (ii) it preserves a low-complexity design that requires fewer hardware resources and consumes less power. The proposed system exhibits regularity, a desirable characteristic not present in other CIC-based recent methods from literature that have pursued the same goals.

In wireless communication, diversity technique is often used to combat multipath fading and improves capacity. The effect of diversity with maximal ratio combining combining technique on the received power due to a mobile transmitting node in Rayleigh fading channel is presented. An analytical expression for the probability density function of received power is derived. Further, the effect of diversity on outage probability is also analysed.

The use of a 35 GHz reflective electroabsorption modulator (REAM) monolithically integrated with a semiconductor optical amplifier (SOA) for indoor wideband analogue applications is demonstrated. Unlike REAMs, good performances over a wide range of input optical power and wavelength are observed, which mitigates the need for accurate control of the input signal, especially at remote sites where simplicity is strictly required. In addition, it provides amplification functions to compensate for the modulator insertion losses. The device exhibits an RF gain in excess of −22 dB and spurious-free dynamic range of >103 dB Hz^4/5. Implementing the rate-adaptive discrete-multitone modulation, 35 Gbit/s aggregate transmission speed is demonstrated for a short-range wideband subcarrier multiplexed radio-over-fibre system.