A novel differentially fed double-slot structure with two metal layers is proposed for an antipodal Vivaldi antenna. When fed differentially, the slots can have their E-field vectors summed to an E-field vector parallel to the layers, which endows the antenna with a significantly lowered cross-polarisation level by comparison with a typical antipodal Vivaldi antenna whose E-field vectors in the slot are skewed to the layers. A wideband balun based on a double-sided parallel stripline is used to realise the demanded differential feeding. The simulation and measurement are carried out to validate the remarkable characteristic of a two-layer structure, which is simpler than a three-layer structure of a balanced antipodal Vivaldi antenna.

A two-dimensional (2D) high-constitutive parameter (TDHCP) substrate is designed using an artificial metamaterial with high-constitutive parameters. The planar TDHCP substrate is used for miniaturising of a circularly-polarised microstrip patch antenna. A 2D metamaterial unit cell is needed due to the fact that the electric and magnetic vectors are rotating in a circularly-polarised antenna. The proposed TDHCP substrate increases the constitutive parameters of the host substrate. It is composed of periodic split-ring resonators loop circuits embedded in a low dielectric host medium. The TDHCP substrate provides equal permittivity and permeability () at any frequency of interest, which compensates for the bandwidth reduction due to the increased permittivity. The size of the proposed TDHCP substrate antenna at 850 MHz is reduced up to about 72% compared to the conventional microstrip patch antenna. The bandwidth of the antenna is increased compared to high-electric permittivity substrates because of the increased the magnetic permeability. The proposed antenna is fabricated and measured. The simulated and measured results show a good agreement.

The nature of the squint problem in the electrically tilted phased arrays (e.g. base transceiver station antennas) is explored based on the antenna theory and array theory. The antenna elements in the horizontal, vertical, or slant polarisations are considered. It is shown that the phased arrays with vertical and horizontal polarisations do not suffer from beam squint. However, it is illustrated that the issue of the squint becomes evident when one scans the beam along the vertical plane with slant antenna elements. A solution to reduce the squint problem is proposed which reduces the squint angle by a factor of two, and also improves the symmetry of the pattern.

Spiking neural network (SNN) that converted from conventional deep neural network (DNN) has shown great potential as a solution for fast and efficient recognition. A layer-wise quantisation method based on retraining is proposed to quantise the activation of DNN, which reduces the number of time steps required by converted SNN to achieve minimal accuracy loss. Pooling function is incorporated into convolutional layers to reduce at most 20% of spiking neurons. The converted SNNs achieved 99.15% accuracy on MNIST and 82.9% on CIFAR10 by only seven time steps, and only 10–40% of spikes need to be processed compared with networks using traditional algorithms. The experimental results show that the proposed methods are able to build hardware-friendly SNNs with ultra-low-inference latency.

A new parental control method to prevent unauthorised usage of touch devices by kids is proposed. The impact of rapidly advancing technology on the developing child has seen an increase exposition to new forms of danger. Studies reveal that 97% of US children under the age of four use mobile devices. A reliable and efficient method to prevent the use of touch devices by preschool children is proposed. The proposed method is based on the analysis of the neuromotor characteristics of the users according to the decomposition of simple drag and drop tasks using the kinematic theory of rapid human movements. The experimentation is conducted on a publicly available database with samples obtained from 89 children between 3 and 6 years old and 30 adults. The results are compared with an existent system based only on task time and accuracy. Finally, both systems are combined at score level to achieve better performances. The results, with correct classification rates over 96% in the combined system, show the discriminative ability of the proposed neuromotor-inspired features and the possibility of combining this system with others to improve their final performance.

A maximum a posteriori (MAP) method to simultaneously estimate location and channel parameters for implantable medical devices is proposed. Achievable localisation accuracy is investigated and discussed based on theoretical and experimental evaluation. As for the theoretical analysis, the Cramer–Rao lower bound for the proposed MAP estimation is derived. Consequently, it is demonstrated that the proposed method achieves precious location estimation accuracy from both theoretical and experimental aspects.

A reference switching pre-emphasis (RSP) technique is proposed for successive approximation register (SAR) ADC in order to improve the SAR DAC settling time, which limits the conversion speed of conventional SAR ADCs. While SAR ADCs that employ redundancy techniques relax DAC settling requirements by overlapping search spaces, this requires more conversion steps which offsets the benefit from the DAC settling relaxation, especially for low–medium resolution SAR ADCs. The proposed RSP technique improves DAC settling by breaking its dependence on ADC resolution and achieves up to 71% speedup of DAC settling relative to a conventional DAC switching scheme without introducing additional conversion steps or significant hardware overhead.

As one of the most significant local features, corners play a fundamental role in 3D computer vision and computer graphics. Two novel corner detection algorithms for 3D mesh data are presented in this Letter, in which the authors examine the geometric properties of the surface in multi-scale space and utilise simple triangle principle to detect mesh corners. Numerical experiments show that our corner detectors outperform six state-of-the-art methods.

A novel method to extract discriminative deep feature representations of facial images for face identification is presented. A new ‘multi-class pairwise discriminant loss’ is devised and incorporated it into the general deep convolutional neural network learning framework in a novel way, leading to highly discriminative deep face features. The method shows significant improvement over existing deep feature extraction techniques relying on softmax or triplet loss. Moreover, the method achieves a level of accuracy on the widely used identification protocols, which are better and comparable results than other state-of-the-art methods.

A new tracking method based on the kernelised correlation filter (KCF) method is proposed. The tracker improves KCF-based trackers by adding seven proposed components, namely, the motion model, background subtraction, occlusion handling, hijacking handling, object proposal, bounding box modification, and object re-detection. With these components, the tracker robustly tracks multiple targets despite severe occlusion, rapid motion, and the presence of other objects with similar appearance. The visual tracking performance is evaluated by using challenging basketball game videos. Experiments demonstrate that the tracker outperforms the original KCF tracker and other state-of-the-art tracking methods.

Without doubt, one of the powerful and effective optimiser in the area of evolutionary algorithms and improved particle swarm optimisation (PSO) is the self-organising hierarchical PSO with time-varying acceleration coefficients (HPSO-TVAC) which has been implemented successfully in the many problems (cited by 2430 until now). Real-world problems are multi-variable problems with real-world different complexities. The classical HPSO-TVAC optimisation technique often converges to local optima solution for some of the real-world problems. Therefore, finding efficient modern versions of the PSO algorithm (here HPSO-TVAC) to solve the real-world problems are absorbing a growing attention in recent years. A novel HPSO-TVAC algorithm for real-world optimisation is proposed. The simulation results show that proposed HPSO-TVAC new version, NHPSO-JTVAC, is powerful and very competitive for real-world optimisation.

To solve the significant performance degradation of existing algorithms in the impulsive noise environment, a novel blind equalisation method called robust adaptive weighted multi-modulus algorithm is proposed in this Letter. The authors introduce an adaptive weight coefficient to suppress the effect of large output error in the weight updating process. Theoretical analysis indicates that the proposed algorithm can suppress the impulsive noise effectively. Moreover, it can accelerate the convergence speed. Simulation results illustrate the robust performance and fast convergence speed of the proposed algorithm under α-stable noise environment.

In this Letter, we analyse the double-sided parallel stripline to realise multi-way differential power division network. The design equations are detailed. For very high frequency/ultra high frequency (VHF/UHF) band applications, a demonstrator centred at 62.5 MHz with ten pairs of differential outputs, utilising the grounded coplanar waveguide as the output interfaces, is developed. Experimental examinations on the fabricated demonstrator match well with numerical simulations, thus verifying the studies network.

A near-band digital predistortion technique is proposed to linearise a wideband power amplifier (PA) with millimetre wave (mmWave) non-contiguous carrier aggregation (CA). The proposed method employs low-bandwidth linearisation architecture to only focus on the in-band compensation and part of the out-of-band (OOB) distortion suppression, which largely alleviate the bandwidth limitation for baseband operation. Experiments have been carried out on an mmWave PA with the centre frequency of 41 GHz. Good measurement results can be achieved when the PA is excited by a very wideband modulated signal with 1001 CA configuration and the total bandwidth of 640 MHz.

A novel coupling topology of substrate integrated waveguide filter with unequal-length slots is proposed. This filter consists of two resonators and a pair of unequal-length slots, which can be considered as two-stage bypass coupling resonators. There exist two resonant modes (TE101 and TE102) in each resonator. TE101 mode is coupled by the long slot, and TE102 mode is coupled by the short slot, which can achieve two resonant modes couplings between adjacent cavities. This structure uses TE102 mode to design the centre frequency of the passband and regards TE101 mode as spurious response. As a result, this filter leads to three transmission zeros (TZs), two TZs locate above the passband and one TZ is below the passband. The filter is fabricated and measured, the measured results agree well with simulated ones.

A very low-loss in-line rectangular waveguide-to-coaxial transition covering an octave bandwidth is presented. In order to obtain such frequency coverage, the transition employs oversized mode conversion, i.e. the rectangular waveguide dimensions are internally enlarged to modify the cavity cutoff frequency while obtaining good matching properties for a standard rectangular waveguide output port. A four-step ridge transformer is included for the TE-to-TE₁₀ mode conversion in the whole frequency range. The transition, completed with a commercial SMA connector for the coaxial port, exhibits a return loss of around 25 dB with 0.1 dB insertion loss when measured in back-to-back configuration in the 10–20 GHz frequency range. From these results, an input matching around 30 dB and an insertion loss around 0.05 dB for a stand-alone transition can be inferred.

A new method of actuating liquid metal using capillary action via paper media is presented. This actuation method uses no electrical power and is capable of moving a liquid-metal slug up to 3 mm/s. A microstrip transmission line switch was fabricated to demonstrate this new actuation method. This switch has >40 dB isolation and <2 dB insertion loss across a 5-GHz span.

For the first time, a bimorph thin film lead zirconate titanate (PZT) micro-actuator with thick polysilicon as a passive structural layer is reported. A simple micro-cantilever actuator consisting of 1000 µm long and 250 µm wide with 4 µm thick polysilicon structure flanked by a piezoelectric active layer on the top and bottom side has been fabricated to demonstrate such novel bimorph configuration. The actuator displays a flat profile with only 2 µm of tip deflection which indicates a balanced stress distribution in the structure. It is driven alternatively in both directions, demonstrating its unique suitability for micro-actuation mechanisms where a passive structural layer is required to enhance the mechanical performance and reliability of the system. The static and dynamic measurements show similar characteristics for the top and bottom actuation. The actuator has a measured resonance frequency of 6.3 kHz, and displacement voltage sensitivities of 17.9 and 25.6 nm/V in the upward and downward direction, respectively.

Quantum logic gates are the building blocks of quantum computer. Here in this Letter the authors propose a new technique of implementing quantum square root of NOT gate by phase encoding mechanism.

A two-stage carrier-based PWM (CB-PWM) strategy is proposed for a three-phase three-level neutral-point-clamped inverter to maintain its constant neutral point potential (NPP). The CB-PWM is a prevalent modulation method used to control inverters. However, the one-modulation-signal CB-PWM cannot mitigate the oscillation of the NPP. The two-modulation-signal CB-PWM, which can mitigate the oscillation of the NPP, requires many additional restrains with implicit principles. Besides, the capability to regulate the drift NPP in the second method is moderate. The proposed strategy in this Letter is to divide the modulation into two stages. The primary stage utilises the one-modulation-signal method. The secondary stage utilises the two-modulation-signal as the auxiliary to the former one. The modified strategy fixes the dc voltage imbalance and mitigates the oscillation of the NPP under any modulation index range and heavy load conditions. The results of simulations and experiments validate the proposed strategy as feasible and reliable.

A novel approach for overcoming the crosstalk noise in frequency-modulated radars is presented. The method consists in performing a crosstalk mapping for the receiver calibration in the absence of targets and computing the optimum threshold thereafter. The linearity of the transceiver has been enhanced by implementing a technique for correcting the distortion that maximises the system accuracy. The robustness and straightforwardness of the proposed approach makes it highly flexible for various radar scenarios, thus avoiding the typical minimum range restrictions due to the crosstalk noise. A radar prototype has been realised for the experimental tests with the aim of confirming the effectiveness of the proposed procedure in a real environment.

A coding metasurface is proposed for reducing radar cross section (RCS) under grazing incidence. Two elements with different reflection phases are selected for the metasurface, and 7 × 7 artificial magnetic conductor unit cells are utilised to construct a metamaterial block. Then the arrangement of blocks is optimised by particle swarm algorithm (PSA). The phase difference between two elements contributes to RCS reduction under grazing incidence. The obtained results demonstrate that a wideband RCS reduction is achieved by the coding metasurface ranging from 6 to 13 GHz. In addition, the monostatic RCS reduction is also achieved under a grazing incidence. For x-polarised incidence, the monostatic RCS reduction is >6 dB from 77° to 90°. For y-polarised incidence, the monostatic RCS reduction is >6 dB from 69° to 80°, and the maximum reduction is 17.5 dB under the 75° incident angle.

A simple closed-form expression is provided for the coverage probability of cellular systems under Hoyt (Nakagami-q) fading, which models fading scenarios more severe than Rayleigh. The accuracy of the proposed framework is validated through Monte Carlo simulations.

A novel approach for indoor localisation is presented and it is composed of two mathematical models. One is a stochastic differential equation proposed to modify time of arrival of a mobile terminal (MT) to a base station (BS). Another is a multivariate optimisation model implemented to estimate the location of the MT by a random search algorithm. Through simulations using only the time of arrivals and measured coordinates of the BSs, the performance of the proposed scheme is evaluated by the measured coordinates of the 25 MTs. Simulation results demonstrate that the mean localisation error is only 0.5138 m and this method is very effective and applicable.

High-quality factor miniaturised inductors are prerequisites of radio frequency integrated circuit applications. This Letter presents a novel fractal stacked inductor using modified Hilbert space filling curve. The proposed inductor achieves higher inductance value and good quality factor because of mutual inductance between plural metal layers and the reduced parasitic resistance. The results show that more than double improvement in L over conventional fractal inductors and more than double improvement in quality factor value over conventional series stack construction.