A 3D optimised hybrid implicit–explicit finite-difference time-domain (HIE-FDTD) method aimed at suppressing the numerical dispersion is proposed. Compared with the original HIE-FDTD method, the optimised parameters are introduced without costing any additional computational resource. In addition, the proposed algorithm sacrifices Courant–Friedrichs–Lewy condition and just requires a modest amount of reprogramming. The update equations of the proposed HIE-FDTD method are given and numerical results demonstrate that the proposed method performs better in the numerical dispersion.

The authors propose a WLAN with a distributed smart antenna system (D-SAS) that can suppress interference and improve the system throughput in high-density scenarios such as stadiums and shopping malls. The authors also demonstrate a prototype of the WLAN with D-SAS and show experimental results in which the proposed system achieves more than twice the throughput of a conventional WLAN system with a centralised antenna system.

Flexible electronics combined with new materials and fabrication processes offer unique characteristics such as mechanical flexibility, thin-form factor, large area scaling feasibility, and adaptability to irregular surfaces. In this work, a smart electronic skin adopting the hybrid system-in-foil concept is designed to monitor the uniaxial bending of a robotic gripper. The newly designed smart skin contains an array of printed strain gauges, organic thin-film transistor (TFT) addressing circuits and a 20 μm ultra-thin silicon readout chip, all integrated on the same polymeric foil. The silver-ink printed strain gauges achieve a relative resistance sensitivity ΔR/R of 2% and a gauge factor of 2. In addition, the organic TFT multiplexer containing a three-stage shift register and analogue switches operate at a frequency of 100 Hz and a supply voltage of 3 V. The ultra-thin silicon chip provides the functions of system control, strain gauge readout, analogue-to-digital conversion and serial communication.

A new method of estimating the antepartum foetal electrocardiogram (ECG) signal by kernel principal component analysis (PCA) is presented. For ECG signals collected from the body surface of the pregnant woman, the powerful maternal ECG is the most PC, compared with the foetal ECG and other noises. Utilising the correlation between the maternal components in different lead ECG signals, the maternal components can be removed from the abdominal signal to obtain the foetal ECG estimation. However, it shows a strong non-linearity between the maternal components in every collected signal due to the diversity of propagation path. Kernel PCA can be seen as a non-linear form of PCA which can extract the non-linear PCs from multidimensional data. Thus, it can be applied to the multiple leads ECG signals to eliminate the maternal ECG components and estimate the foetal ECG signal precisely. The effectiveness of the proposed method is verified by the real data experiment and compared with the existing work.

A linearly frequency-tunable and low-phase noise ring voltage-controlled oscillator (VCO) is presented. Using multiple varactors, of which the bias voltages can be optimally controlled, the voltage-to-frequency gain, K _VCO, can be kept constant over control voltages in all frequency bands. Since the noise contribution and the power consumption of the proposed frequency-tuning method are minimal, the ring VCO also can achieve low phase noise and an excellent figure-of-merit (FOM). The prototype ring VCO was fabricated in a 180-nm CMOS technology. In measurements, the variation of K _VCO over the full range of control voltages was restricted to less than ±12%, even in the worst case. The 1-MHz phase noise and the FOM of a 1.22-GHz signal were –108.7 dBc/Hz and 161.3 dB, respectively, when the power consumption was 8.5 mW.

The quest continues for microelectronic implementations with higher throughput and reduced power consumption, particularly for digital signal processing, graphic processing unit and CPU portable applications. This Letter focuses on the digital multiplier circuit, which is a key component in determining the power-delay-product for numerous battery powered applications. A proposed radix-4 8 × 8 Booth multiplier is implemented using four stages with a unique optimised stage-1 architecture. Instead of using adder/subtractor in stage-1, it is replaced with a novel binary-to-2's complement converter and a 2:1 MUX to reduce the delay and power consumption by 7.08 and 49.46%, respectively, compared to the other stages. The proposed design is implemented using CMOS 90 nm technology with 1.2 V supply to demonstrate performance.

An open-loop per-pin skew compensation with lock fault detection is presented. The proposed circuit employs an open-loop reference selector, a two-stage open-loop delay lock method which is separated by a coarse and fine lock for fast lock-in time, and a fault lock detecting scheme to prevent lock fault by dead zone of samplers. A unidirectional scan method ahead the fine lock stage to minimise pin-to-pin skew errors after calibration is also applied. The circuit was fabricated with 55 nm CMOS technology with a 1 V supply voltage and an area of 0.0036 mm² for one de-skewing module. The measured result shows that the skew error at 1 GHz operation was reduced to <6 ps after skew calibration when the skew between input/output (IO) pins was 230 ps, and the lock-in time was 11 clock cycles.

A four-stage fundamental ring oscillator based on 130 nm SiGe HBT technology is reported. By utilising a novel ground wall decoupling structure as well as a step impedance conversion structure, the generated output power is optimised. The fundamental VCO has a measured peak output power of −1.4 dBm at 243 GHz. The output frequency could be tuned from 237.2 to 249.8 GHz with a tuning range of 5.18%. The core size of the oscillator is only 40 × 80 μm². The peak DC-to-RF efficiency is 1.95% at a 0.94 V power supply. To the best of our knowledge, the proposed VCO achieves the highest output power compared with the other silicon-based fundamental oscillators over 200 GHz.

We measured the impact of the thermoelectric effect, especially the Peltier effect, upon the operation of phase change memory (PCM) in which the contact resistance between the phase change material and the electrode dominates the total resistance. A PCM device having a pillar structure of diameter 500 nm was fabricated using GeCu₂Te₃ (GCT) material. During read operation, the set state (with crystalline PCM) showed ohmic contact between the PCM and the electrode, whereas the reset state (with amorphous PCM) showed Schottky contact. The Schottky contact between the amorphous GCT and the electrode showed a bias polarity dependence of set operation owing to the Peltier effect, which is one of the thermoelectric effects. As PCM devices scale down to the nanometre scale, research on contact resistance and various related effects will become more important.

Due to the heavy computation cost, the bilateral filter cannot be applied to real-time applications. To deal with this problem, many range kernel approximation based acceleration schemes have been proposed. However, all these methods use predefined basis function and assign the same penalisation for all range values to fulfil range kernel approximation. These constraints block from further improving the filtering accuracy and speed. Employing weighted variable projection, a new acceleration method which achieves state-of-the-art performance is proposed. This is done by: (i) unleashing the constraint of using fixed basis function; (ii) exploiting the colour distribution information of the input image to perform a weighted approximation of the range kernel. Experiments demonstrate the superiority of the proposed method in gaining more accurate filtering results efficiently.

With the rapid spread of image editing software, anyone can easily create, distribute, and forge images. Although techniques to detect image forgery have been widely studied, current techniques have significant limitations, such as specific file formats, manipulations, or compression qualities. Although deep learning techniques have been introduced to detect various manipulations, such as blurring, median filtering, and Gaussian noise, these techniques are only suitable to detect forgeries of uncompressed images, and are difficult to apply in practice because most images are compressed for distribution. Therefore, a two-stream neural network approach for image forensics that is robust to compression is proposed. The two-stream neural network is based on constrained convolutional neural network and Markov characteristics to consider compression. Experimental results show that the proposed method overcomes current technique limitations.

Instance expansion of micro-service consumes time for constructing new instances, it cannot satisfy the requirement of low latency service, such as scientific calculation workflows. In order to reduce the time for expanding instances, an instance expansion algorithm for micro-service with prediction is proposed in this letter, which sets correntropy as cost function and uses maximum correntropy criteria to filter the burst service requirements to improve the accuracy of prediction, and use stochastic gradient descent algorithm to train the data set to predict the required micro-service instances in the next time. The performance of the proposed algorithm is analysed in a real experiment telecom office with the compared ones using A/B test, and the experimental results show that the proposed algorithm has 70% less time of instance expansion than the compared ones, and the accuracy of the proposed algorithm is 20% more than the compared one which uses least mean square as the cost function.

A novel method to characterise the efficacy and efficiency of different sequential Bayesian processor implementations is proposed. This method is based on concepts of probably approximately correct computation and information theory measures. The proposed approach is used to compare the performance of three different Bayesian estimation algorithms (particle filter, unscented Kalman filter (UKF), and UKF with outer feedback correction loops) in the context of lithium-ion battery state-of-charge monitoring.

Twill-weave carbon fibre reinforced polymer is measured as a reflector material for electromagnetic waves at 60 GHz. The reflectivity at millimetre wavelength shows a predominant direction, which coincides with the diagonal pattern of the twill's top layer. In the remaining directions, the investigated 2/2 twill-weave composite's reflectivity is almost isotropic.

A novel design approach of three-dimensional filtering balun with inherent complete ground and enhanced stopband rejection is proposed. The whole structure consists of a horizontal feeding plane, a vertically mounted plane, and three ports. By arranging the double-sided parallel-strip line filter symmetrically on the two sides of the vertical plane, the frequency selectivity and complete ground are effectively synthesised. By inserting a rectangular conductor plane with two crossed slots into the middle of the vertical plane, the balanced-to-unbalanced conversion and stopband rejection are significantly enhanced. For demonstration, an experimental filtering balun is fabricated. The measurement agrees well with the simulation, achieving a wide upper stopband under −15 dB from 3.77 to 9.74 GHz.

A bandpass filter (BPF) with improved upper-stopband performance has been studied and implemented with the aid of a ground plane based on high impedance structures (HIS). The microstrip structure of the filter on the top layer consists of three-order cascaded cross-shaped resonators loaded by folded split ring slots. The ground plane contains two groups of 2 × 5 lattice metallic mushroom array, showing high impedance at the spurious band so that the upper-stopband bandwidth of the BPF can be effectively broadened. The HIS-based ground can independently control the stopband without affecting passband performance. Experimental results demonstrate that the BPF exhibits an extremely broad stopband region from 15.5 to 49.2 GHz with a rejection level above 20 dB.

A technique is experimentally demonstrated to double the frequency of a microwave signal by synchronising and polarisation multiplexing the optical signals from a dual-output Mach–Zehnder modulator. The frequency-doubled tone at 4 GHz is 41.2 dB stronger than the residual fundamental-frequency tone. The strongest side tone is found at 12 GHz (sixth order) and is suppressed by 32.7 dB. The phase noise of the frequency-doubled signal is −104.1 dBc/Hz at an offset of 10 kHz, an increase of 6.7 dB over that of the initial signal. This technique does not rely on electronic or optical filters or amplifiers and is demonstrated using commercial off-the-shelf components.

A novel narrow-band balanced filtering network using coupled lines loaded with stubs is proposed in this letter. Two Wilkinson power dividers using coupled lines are used to realise the six-port balanced network. Wideband common mode suppression and power division isolation can be achieved due to the loaded open/shorted stubs. A narrow-band balanced filtering network for the WLAN band is designed. Good agreements can be found between the simulation and measurement results.

A wideband filtering impedance transformer (WFIT) based on transversal interaction concept is presented. The proposed WFIT has four reflection zeros in the passband to broaden the operating bandwidth. Moreover, two transmission zeros are generated to enhance the selectivity. For verification, a prototype is designed, simulated and measured. The measured results show that the proposed WFIT has about 60% bandwidth in terms of S ₁₁ larger than 20 dB and the rejection out-of-band is better than 30 dB.

The influence of gold nanoparticles on the antireflection properties of a thin film of zeolite 3A has been investigated. A low-temperature technique combining zeolite deposition with pulsed-laser gold deposition was used for the fabrication of a composite thin film on a silicon substrate. Experimental results obtained by modulation-polarisation spectroscopy showed that the antireflection effects in polarised electromagnetic radiation can achieve a decreased degree of reflectivity in a wide spectral range due to the presence of plasmonic nanoparticles on the surface of the film.

This Letter presents the design, fabrication and characterisation of an array of electrostatically actuated clamped–clamped microbeams. A large bottom actuation electrode and long beams with lengths ranging from 1 to 3.4 mm are the major features of the present device. The novelty of this Letter lies in the realisation of suspended and undeformed microstructures by controlling the process-induced stress during the fabrication process. This has been achieved by compensating the influence of the compressive and tensile stress components of the different deposited layers, resulting in ultralong beams with a relatively straight mechanical profile and an aspect ratio of ∼1:3400 of vertical deflection to the beam length. For the first time, ultralong microbeams of tantalum have been actuated electrostatically with AC and DC driving voltages to drive them into resonance and characterise their resonant frequencies. The lowest resonant frequency of 1.4 kHz is obtained for a 3.4 mm-long beam. The shift of the resonant frequency due to the effect of different DC biasing has been investigated experimentally. A spring softening effect has been induced through electrostatic tuning. A downward shift in the resonant frequency to 35,000 ppm for DC bias voltages increasing from 1 to 5 V has been demonstrated.

The pulse repetition rate (RR) tuning and locking range (LR) as well as the pulse train timing stability of passively mode-locked quantum-well (QW) semiconductor lasers (SCLs) subject to single-cavity optical self-feedback (OFB) are investigated experimentally and by simulations. A simple and universal stochastic time-domain model confirms the experimentally observed RR control and LR as well as timing jitter (TJ) improvement in QW SCLs subject to very long OFB cavities with lengths up to 73.1 m. In particular, the model allows predicting control potential and limits of the RR tuning, locking and TJ improvement depending on the choice of OFB delay length for time-delay mode-locked semiconductor laser stabilisation experiments.

Inductor DC resistance (DCR) measurement is the standard technique used to measure the current in a single- or multi-phase voltage regulators in computing applications. It is well noted that variations in operating conditions such as temperature cause a mismatch of time constants of the inductor and its DCR, and the RC sensing network. This mismatch affects everything from transient response to safety by affecting the performance of peak current protection features. A digital filter with temperature-adaptive coefficients is presented to correct the DCR measurement across the operating temperature range. Experimental results of a 12 V/1.8 V converter validate the analysis and prove the feasibility of the approach.

In this Letter, the authors introduce for the first time how a Bennet's doubler conditioning circuit will boost the extracted energy from an electrostatic kinetic energy harvester based on triboelectricity. With zero initial bias on all capacitors, after 1000 charging cycles, the harvested power is amplified by more than 2 orders of magnitude by the Bennet's doubler in comparison to a half-wave diode bridge. The harvested energy derived from a 3 × 3 cm² device made of polymer PFA and aluminium is at least 4.6 μJ per tap with the Bennet's doubler conditioning circuit, and only 30 nJ per tap with the half-wave bridge.

A sense-FET-based inductor current sensor for a buck converter operating in 10 MHz switching frequency is reported in this Letter. The proposed sensor utilises an adaptive g_m -boosting amplifier to maintain stable current sensing loop gain and bandwidth over a wide range of load current. Moreover, a mirrored source-degeneration output stage is introduced to further eliminate the bandwidth variation by loading change and achieves full-wave current sensing with smooth transition between the sensed peak and valley currents as the inductor is energised and de-energised. Simulation results show high sensing accuracy better than 96.8% with inductor current varying from 200 mA to 2 A. Furthermore, the settling time is <6 ns during the state transition between peak and valley current sensing with low-voltage spikes.

For original 2D time-of-arrival (TOA) target localisation, since the unknown parameters containing a specific time of the signal that the target transmits, the unknown vector to be estimated is inherently with 3D frame, which makes the analytical characterisation of the geometric dilution of precision (GDOP) more challenging and the problem remains unresolved. A general concise analytical formula of GDOP with closed form for this case is proposed, which can be used to analytically evaluate the accuracy of TOA target localisation for most general application scenarios.

In a passive radar system, the bearing of the target is difficult to measure for the signal-to-noise ratio of the target's echo signal is generally very low in practise. A novel method to estimate the echo signal's angle is proposed. The cross-ambiguity function of direct-path signal and each antenna's receiving signal is calculated to form a virtual array signal, in which the desired echo signal can be enhanced at a certain time delay and Doppler shift, so it is able to estimate its angle. We make the theoretical analysis about how the desired echo signal is enhanced. Some experimental results of an amplitude modulation (AM) radio-based passive radar are presented to verify the effectiveness of the proposed method.

The Letter aims to investigate the polarisation diversity for passive radar system. Digital television signal is used as the illuminator of opportunity in this experiment. Dual-polarised Yagi-Uda antennas have been independently designed as surveillance array antennas, which can receive horizontal (H) and vertical (V) polarisation simultaneously. The experimental results showed that the detection performance after polarisation processing depends on the difference between target polarisation state and interference polarisation state. The target detection performance will be improved if the technology of polarisation diversity is used.

Speckle noise, inherent in synthetic aperture radar (SAR) images, degrades the performance of the various SAR image analysis tasks. Thus, speckle noise reduction is a critical preprocessing step for smoothing homogeneous regions while preserving details. This Letter proposes a variational despeckling approach where -norm total variation regularisation term is approximated in a quadratic and linear manner to increase accuracy while decreasing the computation time. Despeckling performance and computational efficiency of the proposed method are shown using synthetic and real-world SAR images.

The spinning, wide bandwidth antenna remains the most cost-effective technique for finding the direction of arrival of emitters’ signals. The beam is broadest at the low edge of the monitored band, resulting in poor angular resolution at low frequencies. A parameter-free angular super-resolution algorithm is proposed to find the direction of arrival of signals impinging on a spinning antenna based system that does not require tuning by the user. The proposed algorithm was constructed by using the sparse Bayesian learning technique. Using Monte Carlo simulation, the performance of the proposed algorithm is evaluated and shows that it outperforms the iterative adaptive approach algorithm.

A covariance between the Wigner distribution-based instantaneous frequency (IF) estimates is calculated. Derived expression impacts design of IF estimation algorithms both for moderate and emphatic noise influence. Obtained results are confirmed by Monte Carlo simulations.

This letter proposes a set-membership normalised least M-estimate algorithm based on Wiener spline adaptive filter (SAF). The proposed algorithm combines the set-membership framework and least-M estimate scheme, thus achieving faster convergence rate and effective suppression of impulsive noise on the filter weight and control point adaptation. Simulation results demonstrate that the proposed one exhibits more robust performance compared to the conventional SAF algorithms in an impulsive noise environment.

In passive keyless entry and start (PKES) systems, the car unlocks or starts the car when the key is in the proximity of the car. In conventional PKES systems, the car determines the physical proximity of the key on the basis of the received signal strength or the round-trip time (RTT). However, the conventional schemes are vulnerable to relay attacks because the relay amplifies the signal and minimises the processing time. A solution to avoid the relay attacks in PKES systems is proposed, where the car verifies the proximity of the key on the basis of the correlation of the channel state information as well as the RTT.

A novel discrete artificial bee colony algorithm-based partial transmit sequences (DisABC-PTS) scheme is proposed to reduce peak-to-average power ratio (PAPR) of orthogonal frequency division multiplexing signals. Compared to ABC algorithm-based PTS scheme (ABC-PTS) proposed previously, the DisABC-PTS scheme works directly in discrete space, which has a high computational efficiency. Simulation results indicate that DisABC-PTS scheme can obtain lower PAPR than existing PTS schemes and has a low computational complexity.

A design method for rate-compatible (RC) accumulate repeat accumulate check accumulate (ARACA) codes as protograph-based RC low-density parity-check codes is presented. The proposed RC-ARACA codes provide not only good iterative decoding thresholds with the linear minimum distance growth property but also efficient encoder/decoder structures with low complexities, so that they are appropriate to ultra-reliable and low latency communication services for fifth generation.