Non-radiative modes widely exist in the perfect electric conductor systems whose boundaries are closed surfaces, and have had many engineering applications. However, the non-radiative modes cannot be constructed by traditional electric field integral equation (EFIE)-based characteristic mode theory (CMT). The EFIE-based CMT is generalised, such that it can efficiently construct non-radiative characteristic modes (CMs), and it is found out that the non-radiative CMs and traditional internal resonant eigenmodes are one-to-one correspondence.

In this Letter, a circularly polarised loop-type ground radiation antenna has been proposed for internet of things (IoT) applications that use a combination of an inductor and a capacitor in the resonance loop. The antenna has been designed within a 7 mm × 7 mm clearance near the left corner of a 60 mm × 30 mm ground plane. The resonance capacitor is placed at the corner of the radiating loop of the antenna to excite two orthogonal modes on the ground plane. The authors propose that the polarisation of the antenna can be controlled by varying the inductances of the sections of the radiating loop of the antenna. Employing this approach, an inductor is used at the left section of the radiating loop to control the phase difference of the orthogonal modes. Implementing the proposed design, the measured axial ratio bandwidth with reference to 3 dB was 300 MHz, and the matching bandwidth with reference to −6 dB was 110 MHz.

A multiple-port reader antenna for ultra-high frequency (UHF) radio-frequency identification (RFID) near-field and far-field applications which has three modes is proposed and studied. Three fed-ports are designed into the structure, which provide different radiation properties. Specially, far-field radiation for two orthogonal polarisations and near-field operation based on magnetic field coupling can be modified by feeding different corresponding port. The RFID reader antenna can work at three different operations within 820–880 MHz, including European UHF (865–868 MHz) and Chinese UHF (840–845 MHz) bands. Design details, simulation, and measured results are also presented.

In this Letter, the spectral technique that has been applied to the finite-difference-time-domain (FDTD) method is applied to the alternating-direction-implicit higher-order FDTD (ADI-HO-FDTD) method for solving periodic structures, resulting in the periodic spectral (PS) ADI-HO-FDTD. The algorithm for inversion of the block periodic tri-diagonal matrices is presented. The effectiveness and computational efficiency of the proposed method are also shown. Numerical results indicate that the PS-ADI-HO-FDTD algorithm can save computation time by more than 27% in comparison with the conventional HO-FDTD method.

Implantable neural stimulation devices have drawn attention for various clinical purposes. Capacitor-coupled stimulation inherently maintains charge-balance, allowing the use of less complex pulse-generating circuits. This Letter proposes a self-powered relaxation oscillator, which allows direct charge transfer from the energy harvester to the capacitive stimulation electrode. As the proposed circuit does not require power supply to operate the oscillator itself, it achieves high power efficiency by eliminating wasted current from the power supply to the ground. A prototype of the proposed oscillator was fabricated with a 0.35 μm standard CMOS process. The prototype chip demonstrates power efficiency of up to 94.1% at 520 Hz for 1.4 V signal swing.

Although MOS-based pseudo-resistors are capable of achieving the ultra-high resistance required to design small-area neural amplifiers, they suffer from substrate leakage currents which become dramatically higher when the devices are exposed to light. This can cause unwanted amplifier offsets and hinders the usability of these devices in the emerging optoelectrical neural applications. A solution is proposed to compensate the pseudo-resistor leakage current using a dummy deep N-well device. Experimental results show that neural amplifiers implemented with the compensated pseudo-resistor become more robust to photo-induced leakage currents.

The influence of data resampling on ensemble methods, and repeated cross-validation (RCV)-based ensemble feature selection (FS) is proposed. To evaluate the proposed method, support vector machine and its extension and recursive feature elimination were used as the underlying classification and FS techniques, respectively. Experimental evaluation was performed using four microarray datasets. The results show that especially for extremely small signature sizes, increasing ensemble size increases both classification performance and the robustness of gene selection (stability) for both RCV and bootstrap (BS). However, for ensembles of the same size, RCV outperforms BS in terms of performance and especially stability. When compared to the top results obtained by two other studies in which BS is utilised, RCV performs similar or better in terms of area under the receiver operator curve and better in terms of stability.

An adaptive continuous-time linear equaliser using the optimised spectrum balancing (SB) method is proposed. The SB method is extended with a frequency detector to promote compensation ability of an equaliser and completes the optimal equalisation decision for multi-data rates. The active inductor peaking technology is adopted to increase the bandwidth of an equaliser, save chip area and power consumption. Based on Huaili Microelectronics Corporation (HLMC) 40 nm CMOS process to achieve the overall design, the power consumption and chip area are 32.11 mW at 20 Gbit/s and 0.14 mm², respectively. And it can offer a compensation range from 6 to 18 dB for 5–20 Gbit/s of receiving data.

An adjustably transconductance enhanced bulk-driven operational transconductance amplifier (OTA) working at weak inversion region is presented. Based on the traditional positive feedback source degeneration technique, a proposed current-shunt auxiliary amplifier is employed here to modulate the gate of input differential pairs, achieving a further improvement of the effective transconductance with the CMOS technologies scaling. In addition, an adjustable transconductance enhancement factor is obtained, leading to an enhanced stability performance. Both conventional and proposed bulk-driven OTAs are designed and simulated on CSMC 180 nm process. The simulated results demonstrate that the unity gain-bandwidth of the proposed bulk-driven OTA is improved by 120% compared to that of the conventional counterpart with a little neglected increased power consumption.

Compressors are the fundamental components in the partial product reduction stage of CMOS multipliers. A new design is presented for the CMOS 5-2 compressor with 58 transistors, which is the lowest reported device count for such a circuit. Simulation results show that the proposed 5-2 compressor has significantly improved power–delay performance compared to previously proposed approaches.

Detection of the pulse signal at low signal-to-noise ratio (SNR) is difficult but meaningful. Some documents have already used coupled Duffing oscillators to detect non-periodic pulse signal, but those oscillators have a few defects. This Letter presents a type of strong coupled Duffing oscillators system, and by using the generalised time scale transformation, the system can detect signal with any sampling frequency. The system is coupled by damping force and restoring force of the oscillators and has characteristics of high synchronisation speed and high coupling degree. The simulation results show that the system can detect large amplitude signal, large time-width pulse, and plus–minus signal, and the detection SNR is lower than −27 dB.

A partial analogue-assisted (AA) digital low dropout regulator (D-LDO) with also a transient body-drive (BD) technique is proposed. The body of the power switches can be driven by the V _OUT transient spike that is high-pass coupled from the D-LDO output when a load step occurs, for a temporary threshold voltage change. The BD technique thereby manages to provide more than 10% momentary output current. In addition, since the effectiveness of the AA loop is proportional to the ratio of the coupling capacitance and the parasitic capacitance, here, only about 1/5 of the most significant bit of the power switches are connected to the AA and BD networks. Therefore, the coupling capacitors are much reduced, comparing to the previous work. A simulated 100 mV undershoot is obtained under a 2-to-12 mA load step within 1 ns edge time, using only 40 pF total capacitor. A 0.09 ps figure-of-merit (FOM) of speed is thereby achieved, which is at least 2.5× better than state-of-the-art works.

The power optimisation at circuit level of a high-speed counter and a retiming circuit aimed for ultra-low-power digital phase-locked-loops (PLLs) is presented. The high-speed counter topology is based on a well-known asynchronous type with a precise sampling phase generator. Different types of custom true single-phase clock (TSPC) logic style are briefly revised and then strategically used. It is shown that a particular TSPC flip-flop when operating as a retiming element can achieve optimal power efficiency. A prototype was fabricated in an earlier generation 0.13 μm CMOS technology and characterised with a 1 V supply. Measurements show a state-of-the-art power consumption of about 48 μW when operating with a 2.4 GHz input signal.

In this Letter, the authors propose a recursive regularisation parameter selection method for sparse recursive least squares (RLS) algorithm. The proposed RLS algorithm is regularised by a convex function, which equals the linear combination of two convex functions, one to cope with random sparsity, and the other to cope with group sparsity. The normal equations corresponding to the RLS algorithm with the proposed convex regularised penalty function are derived, and a recursive algorithm to update the regularisation parameters (i.e. the coefficients of the linear combination) is proposed. As an example, by using the linear combination of an -norm and an -norm as the penalty function, simulation results show that the proposed sparse RLS with recursive regularisation parameter selection can achieve better performance in terms of mean square error for a slowly time-varying sparse system with both random sparsity and group sparsity.

A composite robust controller is proposed for typical motor servo systems subject to control saturation and unknown disturbance. The controller contains a linear servo control law which achieves a fast response, and a non-linear control part to suppress the overshoot. The unknown disturbance is assumed to have a constant rate of change, and is treated as an extended state of the system. A reduced-order observer is then designed to estimate the unmeasurable state and disturbance for control and compensation. The controller is applied to a permanent magnet synchronous motor for position regulation, and digital simulation and experimental test are conducted to verify the superior performance and robustness of the design.

The optimised sliding mode control for a MIMO non-linear system is designed using a proportional, integral and derivative (PID)-based sliding manifold without limiting the bounds on system uncertainties/disturbances. The probabilistic particle swarm optimisation technique is used to optimise the PID coefficients of the sliding manifold and the sliding mode controller gain. The stability of the uncertain non-linear system using this controller is verified by Lyapunov analysis. Simulation results are presented to validate the proposed controller.

Estimation of 3D human pose from a single image is a challenging task because of ambiguities in projection from 3D space to the 2D image plane. A new two-stage deep convolutional neural network-based method is proposed for regressing the distance and angular difference matrices among body joints. Using the angular difference between body joints in addition to the distance between them in articulated objects such as human body can better model the structure of the shapes and increases the modelling capability of the learning method. Experimental results on HumanEva I and Human3.6M datasets show that the proposed method has substantial improvement in the mean per joint position error measure over the state-of-the-art methods.

A new feature vector based on motion structure of video sequences is proposed which can be used independently or along with motion vectors in video analysis and retrieval applications. The proposed feature vector employs size of prediction units (PUs) in P and B frames of high efficiency video coding (HEVC) coded videos. The feature vector can be extracted by partial decoding of compressed video in the same decoding stage as motion vectors. Video retrieval application is selected to evaluate the performance of the new feature vector. In experimental evaluations, the proposed temporal feature vector independently shows on average 12% improvement in performance against motion vectors and by using it along with motion vectors, the performance of motion vector improves on average by 32% in average normalised modified retrieval rank (ANMRR) measure.

Previous research on orthogonal matching pursuit (OMP) algorithm mainly focuses on the recovery performance of a sparse signal given an acquired model . A general perturbation model in addition to the above acquired model exists, where is the measurement perturbation. For this general perturbation model, the new restricted isometry constant of OMP algorithm is shown.

According to the of time series of faults in railway point machines (RPMs), forecasting approach based on the generalised linear autoregressive moving average (GLARMA) models and the integer-valued generalised autoregressive conditional heteroscedastic (INGARCH) models are presented. The conditional distribution of observed fault counts of given previous faults and weather conditions are assumed to be Poisson or negative binomial distributions. The forecasting future fault counts of RPM are obtained by one-step-ahead forecasts and the performance evaluation shows that the GLARMA method performs better than the traditional autoregressive moving-average (ARMA) model and generalised linear model (GLM).

A modified triangular loop resonator with an open-circuited stepped-impedance stub, which can generate two closely spaced passbands at 5.2 and 5.8 GHz, is analysed. For verification, the triangular loop resonators along with stub-loaded resonators (SLRs) are then employed to design a compact 2.4/3.5/5.2/5.8-GHz quad-band bandpass filter (BPF) for wireless local area networks as well as worldwide interoperability for microwave access applications. Each of the four centre frequencies in the proposed quad-band BPF is able to be controlled due to the design freedom.

The properties of highly confined and isolated surface modes in a phononic crystal based on a stripped membrane combined with disc-shaped thin films deposited on the micro-strip surface is investigated. The structure is made of an aluminium nitride (AlN) thin film membrane and gold (Au) for the disc-shaped thin film. These materials are chosen owing to the strong contrast in their elastic and density properties and to their compatibility with electroacoustic devices technology. An optimal choice of the geometrical parameters of the membrane and the grooves enables the obtaining of wide stop-band frequencies. The introduction of disc-shaped thin films on the grooved surface enables the introduction of nearly flat modes within the band gap and consequently paves the way to implement advanced design of electroacoustic filters and high-performance cavity resonators.

An evaluation of the amplitude jitter and timing jitter for a regeneratively mode-locked fibre laser via the use of the harmonic analysis approach is presented. The RF power spectrum of four harmonics derived from a 10 GHz mode-locked pulse train was measured with high resolution. From a detailed analysis of the noise pedestal present in these harmonics, an amplitude jitter of ∼0.3% and an absolute timing jitter of ∼41 fs are obtained.

The high-quality factors (Q-factors) of nanocavities in three-dimensional photonic crystals were experimentally demonstrated by increasing the in-plane area of the structure. Entire structures made of GaAs were fabricated by a micro-manipulation technique, and the nanocavities contained InAs self-assembled quantum dots that emitted near-infrared light. The obtained Q-factor was improved to 93,000, which is 2.4 times larger than that in a previous report of a three-dimensional photonic crystal nanocavity. Due to this large Q-factor, a lasing oscillation from this cavity mode was successfully observed.

To explore fibre refractive index (RI) sensing based on radiation modes, the influences of ambient RI on radiation modes are investigated by a leaky mode approximation in a two-layer fibre. Based on the analytical analysis and simulation results, it is identified that the change of ambient RI has no effect on the real part of the complex propagation constant of a leaky mode, but a remarkable effect on the imaginary part. More importantly, the influence of the medium's absorption loss on the imaginary part is almost negligible. If the medium's absorption loss is lower than 3.521 × 10³ dB/cm, the induced average deviation rate of the imaginary part is <1.91%.

This letter proposes a highly efficient inverting buck-boost converter at light-load for microdisplay applications. The proposed buck-boost converter, which operates in discontinuous conduction mode, achieves high efficiency by modulating the switch width according to the sensed on-duty of the main power switch using the full-digital method. It generates an output voltage of −4 V using an input voltage of 1.8 V for a maximum load current (I _LOAD) of 20 mA. The proposed converter was fabricated in a 0.18 μm bipolar CMOS DMOS (BCDMOS) process and measured to verify its performance. The measurement results showed that the proposed buck-boost converter achieved a maximum efficiency of 89.3% at I _LOAD of 20 mA and a high efficiency of up to 81.9% at light-load, where I _LOAD is <5 mA.

The beam system of multiple input and multiple output (MIMO) radar needs lower peak sidelobe level for reducing interference, in addition, broad nulls placed at undesired directions are also an alternative method. A hybrid method based on the whale optimisation algorithm is proposed to implement sidelobe suppression and broad nulls. To the best of the authors' knowledge, relative works based on the whale optimisation algorithm applied to MIMO radar are not reported so far. By introducing chaotic optimisation into the whale optimisation algorithm scheme, performance of origin algorithm is improved substantially in suppressing peak sidelobe level with constraint of broad nulls. Furthermore, it is found in the experiment that the proposed algorithm can avoid the premature of origin algorithm effectively, and only takes a short time during the optimum accomplishment. Finally, simulation results demonstrate the good performance of the proposed method.

GaN-based FinFET with double-channel AlGaN/GaN heterostructure is proposed. The current and transconductance characteristics of the device are simulated by Sentaurus software. The simulation results show that the GaN-based FinFET with double channel has higher saturation current and better linearity. The application of double-channel structure improves the saturation current and the control ability of the gate with the aid of triple gate. The combination of FinFET and double channel presents a novel structure for high-performance device. Furthermore, the enhancement-mode device can also be obtained by optimising the Fin width of the device.

An accelerated version of the proximal stochastic dual coordinate ascent (SDCA) algorithm in solving regularised loss minimisation with norm is presented, wherein a momentum is introduced and the strong theoretical guarantees of SDCA are shared. Moreover, it is also suitable for various key machine learning optimisation problems including support vector machine (SVM), multiclass SVM, logistic regression, and ridge regression. In particular, the Nestrov's estimate sequence technique to adjust the weight coefficient dynamically and conveniently is adopted. It is applied for training linear SVM from the large training dataset. Experimental results show that the proposed method has a competitive classification performance and faster convergence speed than state-of-the-art algorithms.

A novel approach for speech enhancement applications by applying spectral mask estimation is introduced. The new application uses the local binary patterns to estimate an ideal neighbourhood mask. This will indicate which time–frequency units of the noisy speech are dominated by the noise. The performance assessment of the proposed application in conjunction with the traditional mask techniques, i.e. ideal binary mask and ideal ratio mask, are carried out under various environments in terms of the objective speech quality measures, as well as word error rate performance in speech recognition systems using deep neural networks. Results indicated that the proposed mask yielded significantly better performance than the conventional techniques.

An ultra-low voltage and ultra-low power programmable gain amplifier (PGA) using a closed-loop single-stage operational transconductance amplifier (OTA) and an input negative transconductor is proposed. The circuits are implemented in a 180 nm CMOS process using two stacked transistors and PMOS bulk forward bias to operate well down to 0.36 V, to be robust to PVT variations and to reach the bandwidth of low energy RF receivers. The PGA measured results at 0.36 V show a programmable voltage gain from 0.2 to 18.4 dB, 15.4 μW power dissipation, 0.98 MHz bandwidth and 0.0243 mm² area.

This Letter addresses the necessity for adaptive threshold (AT) and optimum frame duration (OFD) in spectrum sensing (SS). An adaptation paradigm of Kalman filter incorporated with interacting multiple model to interrogate the channel state information and adjusting the AT and OFD algorithms is proposed. The robust multitaper method is embraced for spectrum leakage control. The analysis of augmenting these algorithms is given and corroborated with simulations, which show their perks for efficient SS applications.

Wireless multimedia sensor networks (WMSNs) have been proposed for use in many challenging applications, such as military surveillance, wildlife tracking, and security monitoring. Reducing energy and storage space consumption are challenging in WMSNs. To address this issue, the authors propose a novel low-duty-cycle WMSN (LWMSN) based on Wi-Fi. This special WMSN is especially suitable for security monitoring, which involves long invalid times in which humans do not appear in the target area. The LWMSN can be intelligently switched on and off by human detection based on channel state information provided by Wi-Fi products. The authors evaluated their design with a simulation and an experiment. Results show that the accuracy of human detection can be >97% on average. In addition, energy and storage space consumption are reduced by 53 and 40%, respectively.

A hypothesis testing based algorithm is proposed to estimate the transmit-antenna number with different space–frequency transmission schemes for multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems. The ranks of received sample covariance matrices composed by every two adjacent subcarriers can be estimated by utilising the statistical property of the largest noise eigenvalue. With a series of the estimated values of the ranks, the number of transmit antennas is determined by a decision mechanism, which is designed based on the frequencies of the rank values. Simulations demonstrate that the proposed algorithm performs well without the prior knowledge of the space–frequency transmission scheme.

A robust 400 MHz super-regenerative receiver with low susceptibility to clock jitter is proposed. The conventional un-clocked envelope detector (ED) is replaced with a synchronous peak-held ED, where its peak detection value is kept during oscillator quenching OFF time by switching off the charging path of ED, synchronously with quenching clock. In this way, the flattened peak level not only allows the use of low quality jitter in the clock but also removes a tedious timing calibration process in the conventional receiver. The proposed receiver with the novel synchronous peak-held ED and an on-chip oscillator achieves a sensitivity performance of −81 dBm@1 Mbps without the conventional ADC sampling timing calibration. The receiver in 180 nm CMOS occupies an active area of 0.51 mm² and dissipates 570 µW.