A metamodelling technique for the efficient design optimisation of the electromagnetic response of metasurfaces is proposed. Metamodels are built starting from data samples of design performance parameters properly extracted from a few electromagnetic simulations using a system identification approach. The metamodels are then used to optimise the metasurface electromagnetic response with respect to some design specifications. Numerical results validate the efficiency and accuracy of the proposed metamodelling technique.

A novel multilayer bidirectional linear array with the same sense circularly polarised (CP) radiation patterns are proposed. The CP resonant unit consists of a pair of loops and two square patches added on their opposite corners. With a feeding slotted substrate integrated waveguide (SIW) sandwiched between two back-to-back mirror rotated resonant units, a radiating element is designed, and same sense bidirectional CP waves are generated. Along the longitude direction, the radiating elements are arranged alternately from the centre line of the slotted SIW. Then, an 8-element linear array with uniform distribution is designed. Identical right-hand CP waves are achieved in both front and back directions. The array is fabricated, and measured results are in good agreement with simulated ones.

A new approach on improving the efficiency of a frequency reconfigurable rectangular microstrip patch antenna using magneto-static responsive structures (MRSs) is proposed. In particular, a 1.5 mm × 1.5 mm × 0.508 mm volumetric structure consisting of two parallel conducting plates separated by a dielectric material summarises the overall MRS embodiment. The dielectric material has a cylindrical cavity (i.e. drilled cavity) with a diameter of 0.9 mm and is partially filled with conducting particles (i.e. silver-coated nickel-based cores) that respond to magneto-static fields. Then, when a small permanent magnet is placed close to the MRS, the conducting particles form columns orientated in the direction of the field lines and connect the two conducting plates, acting as an RF switch. Next, to demonstrate the benefits of the MRS, the efficiency of a reconfigurable patch antenna is investigated. Finally, for comparison, the MRS-based reconfigurable antenna is compared with the measured and simulated efficiency of a reconfigurable patch antenna with the same geometry that uses P-region Intrinsic-region N-region (PIN) diodes. It was shown that the MRS-based design had a much better efficiency (50% larger).

To design a slot antenna intended to work at four bandwidth frequency groups, which meet the specifications of (DO,1xRTT-3G), (WiMAX-IEEE802.11e), (WiMAX-IEEE802.16m) and (Wi-Fi.802.11b,g, & n) communications. The slot in the proposed antenna taken the form of the character (Q) that was feed by step impedance micro strip line design open mouth ended. The surface current distribution at resonant frequencies and the effect of varying the dimensions of the parameters on impedance bandwidth had been studied carefully in this research to enhance the performance of resonant frequency.

Automated electrocardiogram (ECG) beat classification is an important component of heart monitoring systems used for raising an emergency call during sudden cardiac disorder of patients. An automatic ECG beat classifier is proposed to exploit the bandwidth features that are exclusively extracted from analytic intrinsic mode functions (IMFs). The proposed methodology employs artificial bee colony (ABC) algorithm-based least-squares support vector machines (LSSVM) classifier to classify ECG beat types using radial basis function kernel. Simulation results illustrate that proposed classifier gives the best results with second IMF. This novelty lies in its unique combination of ABC with LSSVM classifier that efficiently exploits bandwidth features for automatic classification of ECG beats.

The affine-projection-like (APL) algorithm is reported to achieve lower computations than affine-projection algorithm (APA) without compromising the steady-state performance. Further, the performance accuracy of the adaptive feedback canceller (AFC) in hearing aids is enhanced using an improved proportionate APL (IPAPL) algorithm. Two new learning algorithms are proposed for AFC, which apply the memory of previous gain factors and μ-law proportionate technique to the IPAPL, termed as memorised IPAPL (MIPAPL) and μ-law MIPAPL (MMIPAPL), respectively. In addition, a segmented approach is also suggested which offers computational advantage over MMIPAPL. The results obtained from simulation-based experiments demonstrate that the proposed methods achieve faster convergence rate than the existing methods.

In this Letter a new compensation strategy for a class of three-stage operational transconductance amplifiers is proposed. The proposed approach reduces the original third-order transfer function of the loop gain to that of a pure two-pole amplifier thus allowing the designer to use well-known and consolidated design rules. The approach, suitable for high-speed switched-capacitor circuits, is validated by means of intensive Monte Carlo simulations on a 65-nm three-stage CMOS amplifier.

A novel purely VCO-based architecture for a second-order ΔΣ ADC is presented. The proposed architecture achieves in-band second-order quantisation noise shaping. The proposed ADC is highly digital and well suited for design in scaled technologies. The architecture has been validated with MATLAB Simulink based models.

A novel comparator offset calibration using unbalanced clocks is proposed. The new technique avoids loading the comparator core with trimming elements, thus maximising the comparator speed and power efficiency. Simulations show that a comparator utilising the proposed calibration achieves near-native speed and noise performance. It also achieves superior energy-delay-noise product over comparators with conventional calibrations.

An improved self-blocking flip-flop design is proposed. With smaller clock load and simpler structure, the proposed design is compared with previous flip-flop structures. In the same size of input/output transistors and load capacitance, the proposed structure shows a better performance in speed improvement and power saving by simulation.

An ultra-efficient switching method for successive approximation register ADCs is proposed. In this method, the input signals are sampled in a special fashion to reduce the switching energy. Owing to the sampling method, only one reference voltage (V _q = V _ref/4) is required to implement the switching steps. Therefore, in addition to reduction in the switching energy (due to the lower supply voltage), the precision of the DAC is improved. The proposed method reduces the switching energy and area by 99.41 and 50%, respectively, compared with the conventional method.

A source-switched charge pump (SSCP) with reverse leakage compensation technique is proposed to reduce spur level of wideband PLL induced by the reverse sub-threshold leakage of the charge pump. This technique can set the source–drain voltage of current-source N-type MOS (NMOS)/P-type MOS to be close to zero at off-state of the charge pump and thus reduce the reverse leakage. Compared with the conventional SSCP, only one NMOS capacitor, two CMOS switches and two inverters are added in the proposed charge pump. So, there is negligible extra power and extra area cost. A 0.7–1.6 GHz PLL is designed with the conventional and the proposed charge pumps in 65 nm CMOS process. Simulation results show the proposed SSCP can reduce orders of the magnitude of the reverse leakage without the penalty of current matching, compared with the conventional charge pump. The PLL with the proposed charge pump achieves up to 28 dB spur level reduction.

Multi-robot map merging without inter-robot observations, common landmarks, and the knowledge of initial relative poses is a challenging problem due to lack of features or local maxima. This Letter proposes a multi-hypothesis map merging algorithm with sinogram-based particle swarm optimisation to solve the problem. Experimental results show that the proposed algorithm can merge individual robot maps much more accurately than the existing algorithms.

This research work presents an innovative tensorial analysis of network (TAN) model of asymmetrical 1:2 Y-tree interconnects. The modelling methodology is built with Kron–Branin formalism. The analytical Z -matrix equivalent to the assumed multi-port system is fundamentally established from the transmission line Kron–Branin topology. Then, the equivalent S-parameters of the two-level Y-tree system are established. The developed model is validated with S-parameter simulations of microstrip Y-tree interconnects structure from DC to 8 GHz.

After a short review of the main optimisation methods used in electromagnetic design, the wind-driven optimisation algorithm is focused on. Its generalisation to the multi-objective case is proposed as the original contribution. The relevant algorithm is able to approximate the Pareto front of a design problem characterised by two or more objective functions which are in conflict. The optimal synthesis of current in a solenoid, trading off field residual minimisation and power loss minimisation, is considered as the case study.

This communication introduces a very simple generalisation of the familiar spectral angle mapper (SAM) distance. SAM is perhaps the most widely used distance in chemometrics, hyperspectral imaging, and remote sensing applications. It is shown that a nonlinear version of SAM can be readily obtained by measuring the angle between pairs of vectors in a reproducing kernel Hilbert spaces. The kernel SAM generalises the angle measure to higher-order statistics, it is a valid reproducing kernel, it is universal, and it has consistent geometrical properties that permit deriving a metric easily. We illustrate its performance in a target detection problem using very high resolution imagery. Excellent results and insensitivity to parameter tuning over competing methods make it a valuable choice for many applications.

Fast-match is a fast and effective algorithm for template matching. However, when matching colour images, the images are converted into greyscale images. The colour information is lost in this process, resulting in errors in areas with distinctive colours but similar greyscale values An improved fast-match algorithm that utilises all three RGB channels to construct colour sum-of-absolute-differences (CSAD) is proposed, thus improving the sum-of-absolute-differences distance used in fast-match. In this algorithm, each pixel in the image is categorised by clustering them using density-based spatial clustering of applications with noise (DBSCAN) algorithm over the RGB vector, then the number of pixels in each category and the cumulative RGB values for each RGB channel are calculated to identify the centroid of each category. The RGB vector centroid is used as the CSAD decision criteria, and inverse of number of pixels in each category is used as the differentiating coefficient to construct a new similarity measure. Experiment results demonstrate that this algorithm has significant higher accuracy for matching colour images than the original fast-match algorithm.

The millimetre-wave (mmW) linear polarisation property of a typical stereoscopic object is investigated theoretically. The mmW brightness temperatures (BTs) of the target at different linear polarisations are simulated using ray tracing. Based on the distribution characteristics of linear polarisation images, a linear polarisation fusion (LPF) method is presented to improve the BT contrast between the target area and the background area. The simulation results indicate that the LPF method is capable for achieving good image quality to improve the ability of recognising the target.

A novel and efficient method for person re-identification based on mahalabobis distance feature is proposed. This feature is built on the existing features but exhibits extraordinary discriminative power. With an additional lightweight PCA, it can be cascaded to greatly enhance the overall discrimination. Then Keep It Simple and Straightforward (KISS) metric learning is conducted on such enhanced features. The approach has been evaluated against current methods on a benchmark dataset and can reach outstanding performance.

A fast mutual information (MI) based stereo matching method is proposed that estimates the optimal intensity transfer function in a Bayesian framework. Previous MI-based stereo matching methods require several iterations, where each iteration includes both data cost computation and global energy optimisation such as dynamic programming and graph-cuts. These computations are redundant and time-consuming. In this Letter, a fast two-step MI-based stereo matching method by combining local feature correspondences and global statistics constraints is proposed. Experimental results show that the method is fast, yet generates results comparable with the original MI-based method.

High efficient video coding (HEVC), the latest coding standard, has an encoding complexity much higher compared with H.264/advanced video coding (AVC). The greater efficiency in HEVC is obtained at much greater computational cost compared with AVC. A fast coding unit (CU) splitting algorithm is proposed for the HEVC encoder, which early terminates the CU partitioning process based on an adaptive classification model. This model is generated by an online learning method based on a Pegasos (primal estimated sub-gradient solver for SVM) algorithm. The proposed method is implemented over the HEVC reference implementation on its version 16.7. Experimental results show that the proposed method reduces the computational complexity of HEVC encoder to 35% without any loss, resulting in a 1% of Bjøntegaard Delta-rate gain in the low delay B configuration without any offline training phase.

A novel balanced differential bandpass filter implemented in coplanar waveguide (CPW) technology is presented. The filter is based on the use of two magnetically coupled CPW folded-stepped impedance resonators. The use of magnetic coupling, instead of the more common electric coupling, provides inherent common-mode rejection. Measured and simulated results demonstrate the benefits of the proposed balanced filter.

A novel topology for designing dual-band couplers with −3 dB coupling and a wide range of dual-band frequency ratios is presented. The proposed structure consists of two coupled-line sections connected by two uncoupled lines and four tapped stubs. This coupler can achieve a high frequency ratio of up to 5 by adjusting the impedance of tapped stubs. An experiment coupler operating at 0.7/2.6 GHz with a frequency ratio of 3.71 and −3 dB coupling was fabricated for demonstration.

A non-degenerate dual-mode resonator derived from circular substrate integrated waveguide is proposed, and two pseudoelliptic bandpass filters with non-resonant mode based on the dual-mode resonators are presented. Two resonant modes (higher order modes) are employed to degenerate a passband, while a non-resonant mode (fundamental mode) is designed to provide a direct input-to-output coupling. Owning to an additional path provided by non-resonant mode, the filters have good selectivity and very compact size. The presented simulation and measurement results are in good agreement.

A novel microfluidically tunable bandpass filter (BPF) is proposed and it consists of a second-order microstrip BPF with five plastic tubes placed above the coupled quarter-wavelength resonators. The tubes can be filled with high-permittivity water. By properly choosing the locations of the tubes and the water-filling sequence, the electrical length of the resonator can be tuned, and thus the passband centre frequency of the filter can be precisely adjusted. A demonstration example is designed, and the simulated and measured results of the filter are given for verifying the theoretical prediction.

This Letter studies novel signal interference between composite right/left-handed transmission line (CRLH-TL) and right-handed transmission line (RH-TL). Theoretical study reveals that proposed innovative structure could not only realise conventional three transmission zeros bandstop response in minimised size but also provide bandpass and highpass filtering characteristic. Finally, a bandpass filter having a wide fractional bandwidth of 142% is implemented with very compact size of 42.27 mm × 26.76 mm. Theoretical predictions are well validated by corresponding measurements.

To simplify power-gating requirements in ultra-low-power architectures, design strategies for low-power non-volatile flip-flops (F/Fs) are sought, for which the utilisation of spintronic devices offers a promising option. A D F/F that utilises a five-terminal spintronic device for non-volatile state holding in an intrinsically self-complementing fashion is introduced. This self-complementing device can be exploited to reduce overhead interfacing circuitry in order to realise a compact ten transistors with one spintronic device D F/F with instant store and restore functionality, while consuming <9 µW of power.

Voltage-controlled photoluminescence (PL) switching is demonstrated for single site-controlled InAs quantum dots (QDs) embedded in Schottky–i–n diodes grown by molecular beam epitaxy on nanoimprint lithography patterned GaAs templates. The PL emission was quenched by applying a voltage over the diode structure due to the increased tunnelling rate of charge carriers out of the QDs.

To solve the start-up inrush current existing in the three-phase grid-connected inverter, a soft-start control strategy for the three-phase grid-connected inverter with LCL filter is proposed. The analysis of start-up inrush current is illustrated in detail. The capacitor current of the LCL filter is used to detect the closure of the grid-connected switch, so the closing time of the grid-connected switch does not need to be known. The detailed procedure and flowchart of the proposed soft-start control method are provided. Finally, experimental results of a LCL-type three-phase grid-connected inverter verify the theoretical analysis. The control strategy is easy to implement. The start-up inrush current does not exist in the grid-connected inverter.

This Letter presents a novel modeless predictive current control (PCC) based on two vectors for a synchronous reluctance motor (SynRM) drive system fed by a four-switch three-phase (FSTP) inverter. In each sampling period, two voltage vectors generated by the FSTP inverter are applied to emulate the operation of a six-switch three-phase inverter. Unlike model-based approaches, the proposed method is modeless, meaning that it does not require a system model or its parameters nor the capacitor voltage. For comparison purpose, both model-based and modeless PCCs are realised on a FSTP inverter-fed SynRM drive system via a 32-bit digital signal controller to contrast their current-tracking performances.

The surface passivation for InGaN/GaN multilayer solar cells was investigated, and it was confirmed that the device with an atomic-layer-deposited (ALD) Al₂O₃ passivation film showed high internal and external quantum efficiencies of 99 and 84%, respectively, along with a high energy conversion efficiency of 1.31% under a 1-sun air-mass 1.5 global illumination. The current−voltage characteristics indicated that the ALD Al₂O₃ film improved the surface electrical stability. The carrier lifetime measurements revealed that the ALD Al₂O₃ film reduced the surface carrier recombination rate and thereby contributed to the improvement of the solar cell performance in a short wavelength region.

A model predictive control (MPC) strategy for a three-phase three-level neutral point clamped (NPC) grid-connected inverter is discussed. Conventional two-level inverters are effective when a symmetric fault occurs. But when a three-phase unbalanced fault occurs, they will generate errors and introduce delay in the power system because of the complex design or the neglected negative-sequence component of the grid. To solve this problem, a new method to control a NPC grid-connected inverter is proposed, which combines an MPC strategy with a decoupling double synchronous reference frame phase-locked loop technique. The proposed method reduces the use of PI controllers and enhances the system's response speed. Using simulations and experiments, the proposed MPC strategy for a three-level NPC grid-connected inverter is proven to be accurate and reliable.

Based on soft-switched continuous conduction mode boost converter, a zero-voltage zero-current switching DC/DC converter is proposed by introducing a flyback-unit and a voltage-double-unit. The proposed converter can achieve high voltage gain without operating at extreme high duty cycle. Moreover, by replacing the output diode of conventional boost converter with an active switch, zero-voltage-switched turn-on of switches and zero-current-switched turn-off of diodes can be achieved, which reduce switching loss and alleviate reverse-recovery problem of diodes. Furthermore, the energy in leakage inductor can be transferred into the output of the converter to improve the efficiency. The operating characteristics and the voltage gain of the proposed converter are analysed. Experimental results of a 100 W prototype are provided to verify the theoretical analysis results.

In the imagery of synthetic aperture radar with curved track, the traditional hyperbolic range model (HRM) is inaccurate due to the existence of acceleration. Thus, the traditional imaging algorithms of high precision based on HRM such as Omega-K algorithm are no longer available. For this problem, an equivalent HRM which can precisely take the curved track into account is proposed. Then, Omega-K algorithm with some refinements based on this new range model could be used. Simulation results validate the effectiveness of the proposed range model.

A novel broadband chessboard surfaces with double layer structure to reduce the radar cross-section (RCS) of an object is presented. By combining two artificial magnetic conductor (AMC) cells and a novel structure, 73% frequency bandwidth of −10 dB RCS reduction compared with a metallic plate has been obtained. In order to increase the bandwidth in chessboard structures, boards with high thickness are required, cheaper boards’ thickness are limited. An RO4003 board on an air substrate has been used. This technique, in addition to accommodating the designer with a new parameter, decreases the costs and increases the bandwidth greatly and also simulation results and measurements are in good correspondence.

For better using of the inverse synthetic aperture radar (ISAR) images, it is more desirable to estimate the rotational velocity (RV) for image cross-range scaling. To solve this problem, an algorithm based on affine projection matrix is proposed. This method consists of two parts. The first part is to transform the two sequenced sub-aperture images by affine matrix. The aim is to eliminate the negative effects caused by ‘scaled–stretched’ transformation between the two images. In the second part, the processed images are mapped into polar coordinates system. In polar coordinates, the rotational motion in ISAR image is converted into the translation in the angle dimension. The correlation coefficient is used to search the right RV which provides the maximum correlation between the two processed images. Finally, experimental results based on simulated and real ISAR data are used to prove the effectiveness and practicability of the proposed method.

Pulsed time division multiple access is recommended for psedudolite satellite signal to eliminate the near-far effect, which is different from global navigation satellite system signal design. However, in this case, the initial frequency bias obtained from acquisition is not precise enough for the carrier tracking loop to converge due to the signal's pulse modulation, as the rolling-off of auto-correlation function is insensitive to slight frequency changes. This Letter proposes an approach to narrowing the initial frequency error by mapping from code Doppler to carrier Doppler, in which the former one can be obtained from a delay lock loop (DLL). Simulation results demonstrate the validity of the proposed method in the initialisation of frequency pull-in process owing to the fixed proportion existed in the code and carrier Doppler.

The Global Navigation Satellite System (GNSS) adaptive array suffers from phase distortions owing to beam forming processing which in turn affect the navigation precision. In high precision GNSS applications, the distortions must be evaluated. Traditional phase performance evaluation approach is based on the fixed reception pattern antenna. A new approach to evaluate phase performance of adaptive array is presented. The method takes into account the interfering scenes and the average phase centre variation performance for different adaptive algorithm and array geometry can be obtained.

A high-speed low power multi-phase clock generator with a simple duty-cycle correction circuit is presented. By adding tail transistors driven by the out-phase signal as a discharge path to correct the phase overlapping in the conventional design, 25% duty cycle multi-phase clocks are obtained with <1° phase error. Thanks to this simple topology, the proposed work is featured with fast-speed, low power with a small silicon area. Fabricated in a 0.13 µm RF CMOS process, the proposed clock generator has a measured operating frequency up to 2.73 GHz with a maximum power consumption of 2.5 mW from a 1.2 V supply.

Initial electrical characterisation of epitaxial AlN/Nb₂N heterostructures grown by molecular beam epitaxy on 6H-SiC substrates is presented. Metal–insulator–metal (MIM) devices of varying diameter were used for current–voltage and capacitance–voltage (C–V) measurements at various temperatures. From C–V measurements, a dielectric constant of 10.1 was extracted along with a linear dependence of capacitance on temperature of 0.02 nF/cm²/°C. Leakage current was determined to be consistent with a Poole–Frenkel conduction mechanism at electric fields >1.25 MV/cm with an extracted trap ionisation energy of 0.82 eV. Electric field breakdown ranged between 3.4 and 5.6 MV/cm with some dependence on the diameter of the MIM device. These initial findings demonstrate the potential for high-power devices based on AlN.

An effective algorithm for a more accurate estimation of relative transfer function (RTF) to improve the directional-blind source separation-based RTF estimation is presented. The peaks in time-domain RTF (PTDR) as a feature of time-domain RTF to improve the conventional algorithm are utilised. The PTDRs contain important characteristics of RTF; however, they are smoothed due to the geometric constraint in the conventional algorithm. In the proposed algorithm, the PTDRs are recovered by employing the semi-non-negative matrix factorisation algorithm to effectively find the PTDRs from other peaks. A series of experiments using interfere and various noises demonstrates effectiveness of the proposed RTF estimation algorithm utilising the PTDR.

This Letter describes the design of a broadband testset which measures the reflection coefficient of an arbitrary load. The designed testset has four ports. The first port is for an RF input and the second is for the unknown load, while the remaining two ports are for a reflected power detector and a reference power detector, respectively. The testset adopts a divider-combiner configuration and makes use of differential amplifier and compact, broadband two section power combiners to realise port matching networks at the intermediate stage and for phase cancellation at the last stage. The good phase cancellation is shown to result in high isolation over a broad frequency range. The testset achieves high load dynamic range from 28 to 35 dB in the frequency range of 500 MHz to 3 GHz. The high dynamic range over a broad bandwidth makes the designed testset suitable for use in network analysers.

In millimetre wave (mm-wave) communications, hybrid precoding is preferred which uses much less number of RF chains compared with the number of antenna elements. The conventional method selects the beamforming vectors at base station (BS) and the combining vectors at user equipments (UEs) to maximise the received signal power. However, in some specific scenarios, when UEs have strong and highly correlated paths, referred to as collided UEs, they might share the same beamforming vector at the BS leading to severe inter-user interference. An enhanced beam selection algorithm is proposed to eliminate the severe inter-user interference by reselecting the beamforming/combining vector pairs for the collided UEs. Simulation results demonstrate that the proposed scheme could increase the achievable rates of the collided UEs under sparse mm-wave wireless channels.

An incremental least-mean M-estimate algorithm is proposed for distributed network, which minimises a robust M-estimator-based cost function against impulsive noise via the gradient descent method. Moreover, based on the same frame for implementation, an incremental distributed least-mean p-power algorithm is presented for combating impulsive noise. Simulations verify the superiority of the proposed algorithms in the presence of impulsive noise relative to some existing incremental distributed algorithms.

A novel algorithm for simultaneous modulation format/bit-rate classification and non-data-aided (NDA) signal-to-noise ratio (SNR) estimation in multipath fading channels by applying deep machine learning-based pattern recognition on signals’ asynchronous delay-tap plots (ADTPs) is proposed. The results for three widely-used modulation formats at two different bit-rates demonstrate classification accuracy of 99.8%. In addition, NDA SNR estimation over a wide range of 0−30 dB is shown with mean error of 1 dB. The proposed method requires low-speed, asynchronous sampling of signal and is thus ideal for low-cost multiparameter estimation under real-world channel conditions.

A decode-and-forward (DF) relay-assisted RF-powered cooperative communication between an RF energy harvesting source and an information sink is considered. DF relay aids the communication between these two distant wireless nodes by (i) RF energy transfer to the source, and (ii) relaying source data to the sink. To enable efficient RF-powered delay-constrained information transfer to the sink under Rayleigh fading, joint global-optimal time allocations for information and energy transfer are derived. Impact of relay position on throughput and optimality of the analytical solutions are numerically investigated.