A four-element dual-band MIMO configuration consisting of split-ring resonator (SRR)-loaded inverted L-monopole antenna elements is realised. In the proposed antenna, the lower-frequency mode of the unloaded MIMO configuration merges with one SRR-induced antenna resonance. This leads to antenna operation around 2.93 GHz with wide impedance bandwidth (IBW) of 35.21%, encompassing the lower WLAN, worldwide interoperability for microwave access, wireless fidelity, fourth generation (4G)-long-term evolution and sub-6 GHz 5G bands. Furthermore, due to SRR loading, the proposed MIMO antenna exhibits a resonance at 5.68 GHz (IBW 6.86%), covering the upper WLAN band. Minimum inter-element isolation of 14 dB is achieved, in spite of the compact total area (, λ ₀ = highest operating wavelength) and the presence of inter-connected ground plane. Both the working bands exhibit directional radiation patterns with average gain . Experiments on the fabricated antenna prototype confirm that the simulated and measured S-parameters, radiation patterns (envelope-correlation coefficient, channel capacity loss and total active reflection coefficient) are in good agreement.

A novel inductive ensemble clustering method is proposed. In the proposed method, kernel support matching is applied to a co-association matrix that aggregates arbitrary basic partitions in order to detect clusters of complicated shape. It also has the advantage of naturally detecting the number of clusters and assigning clusters for out-of-sample data. In the proposed method, a new similarity is learned from various clustering results of the basic partition, and a kernel support function capable of clustering learning data and test data is constructed. Experimental results demonstrated that the proposed method is effective with respect to clustering quality and has the robustness to induce clusters of out-of-sample data.

A highly compact (25 × 25 × 0.8 mm³) dual-band folded square-loop antenna is proposed for reading near-field RF identification (RFID) tags. The antenna has a strong and uniform magnetic field in the near-field zone of the square loop. The side length of the square loop (∼λ/16) generates resonant frequencies in two conventional modes (0.5λ and 1.0λ). Experimental interrogation of a small RFID button tag attached to a blood sample collection tube showed that the antenna has a small interrogation zone (15 × 15 mm²), which avoids unnecessary interrogation. Experiments also showed that with an input power of 25 dBm, the antenna can tag at a distance of up to 40 mm, which confirmed its suitability for reading button-type RFID tags attached to blood sample collection tubes and other specimen containers.

Transceivers for backplane serial links operating up to 25 Gb/s demand flexible equalisers with high accuracy in matching the channel response. A continuous time linear equaliser (CTLE) with a transversal architecture features variable DC gain and two zeros that can be tuned independently. The transversal architecture yields a paraboloid mean-square-error surface, allowing optimal adaptation through gradient descent algorithms. The CTLE was realised in a 28 nm CMOS technology and measurements are presented at data rate from 5 to 25 Gb/s across 20 dB-loss channels. Core power dissipation is 17 mW from 1 V supply and horizontal eye opening at BER 10⁻¹² is equal or larger than 50%, comparing favourably against previously reported equalisers targeting similar data-rate and channel loss.

Among resistive random access memory (RRAM) architectures, one transistor one memristor (1T1R) crossbar is the most fledged one. For 1T1R crossbar, a logic operation-based Design for Testability and parallel test algorithm, which is an improvement of March C*-1T1R test algorithm, are proposed. The pass-fail fault dictionary of the proposed test algorithm is analysed. Analytical results show that the proposed test algorithm can detect all the modelled faults caused by the parametric variation of memristors and traditional RAM. Compared with March MOM, March C* and March C*-1T1R, the test time of the proposed test algorithm is reduced with a little area overhead for a large size crossbar.

A class of the almost-maximally flat (AMF) lowpass filters with Chebyshev stopband attenuation, referred to as AMF filters, is discussed. Allpole lowpass filters’ transfer functions are first derived by using parameters and of modified Jacobi polynomials such that passband attenuation is minimised, and obtained transfer functions are then augmented by adding one or several pairs of -axis transmission zeros. The magnitude characteristics of proposed filters are compared with those of the Chebyshev II filters and are found to be superior, both in the passband and in the stopband.

Liquid metal is actuated against the force of gravity using low-voltage, low-power continuous electrowetting. The liquid metal moves from a lower reservoir to an upper reservoir, a distance of 12 mm, in 1.66 s. This demonstrates that the electrokinetic actuation of liquid metal is not limited to two-dimensional movement.

High-frequency signal injected methods are widely applied to the sensorless control of permanent magnet synchronous motor (PMSM) especially at standstill and low-speed range. Most of the methods are based on the tracking theory, which leads to an angle uncertain of π. The method proposed in this Letter is also based on the injection method and can calculate the rotor absolute position directly by introducing a virtual reference frame which rotates at a fixed frequency, which makes it possible to eliminate the angle uncertain of π with a simple deviation compensation method. Furthermore, all the PMSMs even with near-zero saliency can adopt the proposed method. Finally, the simulation results show that the proposed rotor position estimation method has a good performance even under load changes.

An analytical method is presented for calculating the shielding effectiveness (SE) of an enclosure with a horizontal curved edges aperture. Based on the transmission line theory, the horizontal curved edges aperture is treated as many short coplanar strip transmission lines connected in series. Then the equivalent impedance of the curved edges aperture is calculated by the iterative formula proposed in this Letter. Submitting the equivalent impedance into the existing equivalent circuit, the SE of the enclosure with a horizontal curved edges aperture can be calculated efficiently and precisely. The proposed method was validated with measurements and the transmission line matrix algorithm.

An improved 3D cellular automaton segmentation algorithm is proposed. The purpose is to create a tri-directional automaton in order to segment 3D volumes. The improvement is that a force is created in the RGB space in order to improve the result of the 3D algorithm. Experiments on several synthetic volumes have shown that the proposed method achieves better segmentation results and efficiency than the other methods.

A new cascade recurrent neural network (CRNN) for image caption generation is proposed. Different from the classical multimodal recurrent neural network, which only uses a single network for extracting unidirectional syntactic features, CRNN adopts a cascade network for learning visual-language interactions from forward and backward directions, which can exploit the deep semantic contexts contained in the image. In the proposed framework, two embedding layers for dense word expression are constructed. A new stacked Gated Recurrent Unit is designed for learning image-word mappings. The effectiveness of the CRNN model is verified with adopting the commonly used MSCOCO datasets, where the results indicate CRNN can achieve better performance compared with the state-of-the-art image captioning methods such as Google NIC, multimodal recurrent neural network and so on.

Image quality assessment is of fundamental importance for various image processing applications. A novel method is presented in which the joint occurrences of statistical local representation by log-Gabor filters and texture analysis by local tetra patterns and histograms of colour are considered as quality-aware features. Then the dissimilarities of these features between the distorted and reference images are quantified and mapped into quality score prediction by utilising a support vector regression. Extensive experiments on LIVE, CSIQ and TID databases show that the proposed method is remarkably consistent with human perception and outperforms many state-of-the-art methods, and also it is robust across different distortion types and different databases.

A no-reference stereoscopic image quality assessment method is proposed that takes two primary binocular effects, visual discomfort, and binocular rivalry, into consideration. The adaptive segmentation, local energy, and visual saliency are employed for estimating binocular effects and constructing a quality baseline, which together composes a comprehensive image quality description. Moreover, a compact parallel framework is designed for efficiency. Experiments have validated the high accuracy and robustness of the proposed method.

The conventional object segmentation methods often degrade their performance due to the requirement of user interaction and/or the incomplete colour appearance models. In this Letter, the authors propose a novel design method of a colour appearance model for accurate and fully-automatic object segmentation by using saliency maps. The authors initialise the Gaussian mixture models (GMMs) to describe the colour appearance of the foreground objects and the background, respectively, where the mean vectors, covariance matrices, and mixing coefficients are updated adaptively such that more salient pixels have larger weights to update the GMM for the foreground objects while less salient pixels have larger weights to update the GMM for the background, respectively. Experiments are performed on MSRC, iCoseg, and PASCAL datasets and we show that the proposed method outperforms the existing methods quantitatively and qualitatively.

In this Letter, the authors present an improved sparse recursive least squares (RLS) algorithm, which employs a novel approximation of the norm of the filter coefficient vector for regularising the RLS cost function. The proposed algorithm achieves improved performance over existing algorithms as demonstrated via numerical simulations.

The authors suggest a simple visualisation system for the surface roughness information, with being highly cost-effective, non-destructive for the surface, curved-surface measurable, and standard-compensated. This system utilises a force sensor with a flexible stylus as a scanning tip, converting the surface property into a two-dimensional grey scale image through an imaging analysis process. The authors acquire a linear coordination for standard surfaces, scan normal surfaces using the proposed novel system, and reconstruct the two-dimensional images for the surfaces on the basis of the calibration curve. The authors can experience virtual roughness of a material with a reconstructed two-dimensional image by comparing with the standard surface images.

This Letter proposes a balanced hybrid substrate-integrated waveguide (SIW)–coplanar waveguide (CPW) bandpass filter, which combines a hybrid SIW–CPW filter and a balanced structure for the first time. High performance common mode suppression can be achieved with high quality factor, compact size, and quasi-elliptic differential mode response.

A dual-band microstrip bandpass filter using the rectangular loop resonator (RLR) is proposed. A microstrip open stub is implemented to perturb modes of the RLR, and the two modes form the low-frequency passband. The stepped impendence microstrip lines are adopted to excite the RLR and the lines also work as the resonant stubs, i.e. one is 3/4-wavelength resonance stub and another is full-wavelength resonance stub. As a result, the second passband is introduced. Furthermore, each passband can be tuned independently through the corresponding resonant paths (parameters), which are discussed in detail. Without the connection stub between stepped impendence microstrip lines and RLR, this dual-band bandpass filter will degenerate to a dual-mode single-band bandpass filter and the corresponding results are also obtained and demonstrated. The measured results agree with the simulated results well.

A quasi-lumped dual-mode reconfigurable eight-way filtering power divider (FPD) is presented. Two operating modes are one eight-way tunable FPD and one all stopband filter (ASF) with high suppression. The measured eight-way FPD can be tuned from 1.0 to 2.15 GHz, corresponding to the frequency tuning range (FTR) of 73%. The ASF is obtained by misaligning resonant frequencies of LC resonators and weakening their coupling. The proposed dual-mode FPD has the advantage of wide FTR, compact size, high isolation, ultra-wide isolation BW, and high suppression.

This Letter presents a novel out-of-phase filtering power divider (FPD) with a very wide stopband by using double-sided parallel-strip line (DSPSL) and through ground via (TGV). The DSPSL structure facilitates the out-of-phase outputs of the FPD. The TGV and two complex-impedance terminations connected to the common input port are employed to achieve the isolation. By choosing proper feeding coupling region and the loading resistors at the centre of the resonators, the second, third and fourth harmonics are suppressed. For verification, a prototype FPD operating at 1.85 GHz (f ₀) with 5.2% bandwidth is designed, fabricated and measured. The experimental results show that the isolation between the output ports is better than 24 dB across the passband, and the 28 dB rejection band is extended to 4.6f ₀.

Operation of single-stage, single-pump E-band bismuth-doped fibre amplifier with gain, noise figure and efficiency comparable to the state-of-the-art erbium-doped fibre amplifier of the same complexity and the gain bandwidth of 50 nm is demonstrated. The amplification of 10 Gbit/s intensity modulation/direct detection signal with power penalty below 1.5 dB is reported.

A low-power delta–sigma modulator based on inverter operational-transconductance amplifiers (OTAs) using correlated level shifting technique (CLS) is presented. The CLS technique boosts the DC gain of inverter-based OTA from 42 to 79 dB and extends the linear output swing from 55 to 80% of the full scale. Simulation results show that design in 180 nm CMOS technology, the proposed second-order delta–sigma modulator achieves a signal-to-quantisation-noise ratio improvement of 10.4 dB compared to a conventional inverter-based modulator implementing the identical loop filter with the same oversampling ratio.

State of charge (SOC) estimation plays a critical role in the operation of an electric vehicle (EV) power battery. In this Letter, the authors propose machine learning (ML) algorithms as alternate to the existing filtering algorithms used for SOC estimation of an EV battery. The SOC estimation approach is evaluated by the simulation experiments in advanced vehicle simulator (ADVISOR). For the modelling of ML algorithms, the input parameters that affect the SOC estimation are battery current, battery module temperature, power out of the battery (available and requested), battery power loss and heat removed from the battery. Training and testing stages of the models are carried out using the data collected from ADVISOR. As the drive cycle conditions provided by ADVISOR are universal therefore present method is applicable to all kinds of batteries used in EVs including lithium ion, nickel metal hydride and lead acid batteries. Thus, the proposed models for SOC estimation provide an alternative approach in SOC estimation.

Synthetic aperture radar imaging suffers significantly from incomplete datasets, where whole pulses are missing. In this Letter, the author introduces an elastic net regularisation to imaging, reducing those artefacts and improving the signal to noise ratio of the image at the same time.

A spatial rotation technique in application to unmanned underwater vehicle (UUV) sonar arrays is proposed. The essence of the technique is to rotate the signals of interest from the array coordinates to geodetic coordinates while providing robustness against interferences and preserving the white noise property at the output. Convex formulation of the rotation matrix design problem is derived using the semi-definite relaxation technique and the optimal solution is obtained by rank-one decomposition theorems. Using the authors’ technique, the subspace-based direction of arrival estimation methods can get large snapshot support for weak sources in the UUV motion-case.

The behaviours of drain current noise of 40 nm n-MOSFETs are distinguished by comparing with 120 nm n-MOSFETs over an extended range of bias voltages and temperature. The measurement results strongly indicate that the high-frequency noise mechanism of 40 nm n-MOSFETs is changed from suppressed shot noise to thermal noise on conditions of low-voltage weak interaction.

A single-step ductile dicing process capable of manufacturing optical quality facets in lithium niobate (LiNbO₃) ridge waveguides with an average surface roughness of 0.29 nm is reported. This result is comparable with surface roughnesses achieved by lapping and polishing and represents an order of magnitude improvement over the prior state of the art in LiNbO₃ waveguide facet dicing.

A novel acoustic insect classifier on deep convolutional feature of frequency spectrum images generated by their wingbeat sounds is introduced. By visualising insect wingbeat sound, the proposed method is the first attempt to convert time-series acoustic signal processing to image recognition, which has recently gained significant improvement with convolutional neural networks. Experiments show the better accuracy of the proposed method on the public UCR flying insect datasets compared with the state-of-the-art methods.

M-ary stepped θ-QAM (θ-QAM) for M = 2^2l , l ≥ 3 based on square QAM is proposed. The signal constellation of stepped θ-QAM and the coordinates of the symbols generalised for modulation order M are presented. Then analyse the symbol error rate (SER) performance, and the optimum value of θ in terms of minimum SER for stepped θ-QAM in additive white Gaussian noise and fading channels. Through computer simulations, the theoretical results are validated and show that stepped θ-QAM offers better error performance than θ-QAM.