The frequency delta-sigma modulation (FDSM) technique was applied to the microphone sensors. The FDSM is a superior analogue-to-digital conversion technique, which outputs wide band, large dynamic range digital signals without precision analogue components. In this implementation, a microwave cavity resonator having movable membrane on its one end, together with a gain block consisting of a heterojunction field effect transistor, was used for sound-frequency converter. The output of this converter (frequency modulated intermediate signal) was sampled and converted to 1-bit delta sigma modulated digital signals. The noise shaping behaviour with a clear signal peak was demonstrated for the fabricated devices.

A dual-polarised phase-correcting microwave transmitarray that is based on an ultrathin phase-shifting surface (PSS) has been developed at 22 GHz. The FSS element in this array has a square shape with the rotationally symmetrical geometry. It consists of two identical metallic layers etched on the two sides of a single dielectric layer. A phase-shifting range of about 330° is achieved. A planar slot-fed patch antenna was developed as the feed source for the compact structure. The transmitarray prototype, which is fed by a planar antenna, as well as a standard horn, was measured separately. The results show that peak gains of 25.82 and 27.45 dBi and 1 dB gain bandwidths of 6.8 and 9.5% are achieved for the two feed cases.

A planar broadband circular tag antenna operated at ultra-high frequency (UHF) band for radio-frequency identification (RFID) system is proposed. By adding a pair of T-arc-shaped strips and parasitic step strips, excitation of multi-resonant modes can approximate reach with the operating half-power band from 848 to 963 MHz, which covers the required bandwidth for worldwide UHF RFID (860–960 MHz) system. Moreover, the measured read distance of this design can reach 3.8 m, and exhibits good unidirectional radiation patterns in the X–Z and X–Yplanes.

High-frequency characterisation of the wood-fill filament for three-dimensional (3D) printing technology and its feasibility in small-size antenna manufacturing based on additive manufacturing (AM) technology is focused. A Keysight 85070E high performance dielectric probe was utilised to characterise the wood-fill material for a wide frequency range. The real and imaginary parts of the complex permittivity for the various 3D printed samples were measured from 20 MHz to 20 GHz, and the corresponding loss tangent was calculated accordingly. A dipole antenna embedded on the wood-fill 3D printed substrate was designed, simulated, and fabricated at the centre frequency of 2.4 GHz. Three different conductive materials were utilised for the conductor part of the antenna.

This Letter proposes the use of a modal pattern stability factor (MPSF) parameter to quantify the pattern stability associated to characteristic modes (CM). The proposed parameter can be used as a figure of merit for CM associated to arbitrary-shaped structures, aiding the antenna design process. This parameter can be used (together with other modal parameters) to optimise the geometry of a radiating element in order to improve the radiation pattern stability in a desired range of frequencies. Two examples are presented for analysis. First, MPSF for the CM of three ring antennas with different width are analysed, showing how pattern stability of CM depend on this geometrical parameter. Secondly, three metallic plates with different shapes are analysed in terms of MPSF, in order to assess the stability of the CM for each geometry.

A wireless stress sensor integrated circuit (IC) has been implemented in 0.18 μm CMOS technology. The IC is composed of a 256-cell stress sensing array, the current-based sensor readout circuit, a 12 bit successive approximation (SAR) ADC and a 432 MHz wireless transmitter. The stress sensor employs orthogonally placed current source pair to measure the normal and shear stresses. The chip is backlapped to 35 μm for ultra-thin applications such as human skin stress distribution measurement. The measured sensing nonlinearity is below 0.7%. Experiments show that the implemented IC can be used to detect the facial expression changes.

MRI has the potential to produce clear anatomic, as well as functional, images of the human body. However, the ability to diagnose is limited by signal-to-noise ratio (SNR) and the resolution of current medical systems. To remove the challenges prevalent due to the use of high-field scanners, dedicated RF coils are used. Transverse electromagnetic (TEM) coils have the advantage of providing a homogeneous magnetic field throughout the region, but with a low SNR, while surface coils have the advantage of providing a higher SNR, but with low homogeneity. The research discussed combines both advantages into one by utilising transmit-only TEM RF coils (8-channel) along with receive-only surface coils (varying in number) to obtain good homogeneity, as well as significant SNR improvements, from MRI throughout the human brain.

The mHealth wearable devices have been adopted in the last few years and have improved the human well-being. However, mobile devices are still quite resource constrained and mHealth applications require high availability. Mobile cloud computing (MCC) is one alternative to aid mobile devices by providing remote powerful infrastructure. The objective is twofold: (i) to identify the most important components of a mHealth system through parametric sensitivity analysis; (ii) to propose and design an extended mHealth architecture with higher system availability and lower downtime period. The proposed solution reduced the downtime in 41% compared with the baseline architecture.

A vision-based tactile sensor has been implemented to build an artificial fingers capable of grasping for the hand prosthesis. The tactile sensor hardware is composed of an elastomer sensing part with one layer of markers and an image sensor. By employing the depth from defocus technique, three-dimensional contact force distribution can be reconstructed from the 2D images of only one layer of markers. The proposed hardware and algorithm have been validated through experiments.

A highly reconfigurable charge-domain switched-g _m-C complex bandpass filter (CBPF) topology that utilises a semi-passive charge-sharing technique is proposed. It uses only switches, capacitors, digital circuitry for three-phase non-overlapping clock generation and efficient g _m-stages. Simulated in a 65 nm CMOS, a first-order CBPF operating at 1 GS/s sampling rate demonstrates flexible tunability of the centre frequency and bandwidth with a highly passive/digital implementation. The presented filter architecture features excellent power efficiency and compatibility with process scaling.

The classical fingerprint of the ideal memristor with differentiable constitutive relation has recently been extended with a piece of knowledge that the area of the pinched hysteresis loop of a memristor driven by sinusoidal signal with fixed amplitude and increasing frequency disappears with an integer power of the frequency. This fingerprint is extended to the memcapacitor and meminductor, and it is also shown that the way the hysteresis disappears can be determined directly from the behaviour of the parameter versus state map (PSM) of the element in the neighbourhood of the initial operating point.

This Letter presents a self-controlled physical unclonable function (PUF) circuit and its application in encrypting on-chip memories of IC bank cards. The PUF circuit is based on cross-coupled NAND gates. Voting and Hamming code address the stability of its outputs. The Monte Carlo simulation and field-programmable gate array board are used for verification. The Voting method improves the error rate 79%. The Hamming codes and convertor can correct every error bits of PUF outputs. The PUF outputs, data address and time-stamp are encrypted by SM4 (Chinese block cipher algorithm standard) to generate KEY. The data does XOR with the KEY.

Memristor crossbars are capable of implementing learning algorithms in a much more energy- and area-efficient manner compared with traditional systems. However, the programmable nature of memristor crossbars must first be explored on a smaller scale to see if physical devices are suitable for applications of reconfigurable computing. The reconfigurability of these devices through small scale memristor crossbar implementations is demonstrated. It is shown that a crossbar containing eight memristors is capable of learning several different two-input Boolean logic functions. A strong foundation is provided to build on demonstrating that physical memristor crossbars can be programmed as linear classifiers.

Three-axis spacecraft simulators are widely used to verify spacecraft control strategies. Designing a simulator whose moment of inertia are similar to the spacecraft's is important for control research. Moreover, to reduce the disturbance of gravity torque, the centre of mass of the simulator attitude stage must be exactly aligned with the centre of rotation. Various sensors and actuators are on the simulator. An optimisation method for the locations of these devices on the simulator is presented. In this method, these devices are described as rectangles and circles. Their spatial relationship are expressed by a series of inequalities. The total inertia parameters of these devices are optimised.

Pose estimation is a critical problem in the challenge of visual object recognition. An alternative model, agreement function (AF), is proposed to solve this problem, which is essentially a generative model since it is learned to represent the joint probability distribution of the inputs and their poses. Estimated poses of unseen samples can be obtained by maximising the AF conditional on the given samples. Extensive experiments are performed on several challenging datasets to validate the authors’ model, and achieved state-of-the-art experimental results.

Alpha-numeric gesture refers to writing in air of alphabet and numeric characters. With prevalent usage of vision enabled smart devices, these gestures are considered as an alternative user interface. As each individual has a unique handwriting style, it has been observed that alpha-numeric gesturing also exhibits different individualistic styles, posing a challenge to the vision based gesture recognition. In this Letter, a simple but effective method of modelling alpha-numeric hand gestures by fusing temporal-feature-state modelling and total-trajectory-shape modelling is proposed. The proposed method employs a convolution neural network that represents total-trajectory-shapes, and combines it with conventional conditional random fields based temporal-feature-state modelling. The proposed algorithm is evaluated in public database of both alphabet and numeric hand gestures. Experimental results show a performance improvement of the proposed algorithm compared with the state-of-the art methods.

The rate–distortion optimisation criterion of depth maps coding is evaluated by virtual view distortion, which motivates research modelling the distortion and corresponding Lagrange multiplier for depth maps coding. Current studies follow the assumption that the virtual view distortion introduced by texture videos distortion and depth maps distortion can be explored separately. Then the texture-videos-distortion-induced virtual view distortion is considered as a constant value during depth maps coding. A relationship between the optimal Lagrange multiplier of depth maps and texture videos distortion is investigated. Based on this relationship, an efficient Lagrange multiplier selection algorithm is proposed for depth maps coding based on quantisation parameters of texture videos and depth maps. With the proposed Lagrange multiplier, 1.36% bitrate saving with the same virtual view quality can be achieved compared with 3D high efficiency video coding reference software.

A new feature for image retrieval based on edge orientation patterns (EOPs) by classifying image blocks into nine classes according to their EOs. Each input colour image is decomposed into Y, Cb and Cr components, and each component image is divided into non-overlapping 4 × 4 blocks. For each block, eight EO templates of size 4 × 4 are performed to determine its EO. On the other hand, vector quantisation (VQ) is an efficient clustering and classification technique for high-dimensional spaces, and thus VQ is also used to extract the texture features. The retrieval simulation results show that the EOP-histogram-based features combined with the traditional VQ-index-histogram-based features can largely improve the recall and precision performance.

A simple and efficient method for lossy colour image compression is proposed. Here, the discrete cosine transform (DCT) is applied to the YCbCr image obtained from the original RGB image. The bisection method is used to define the required threshold for a prefixed user peak signal to noise ratio as a controlled quality criterion. The thresholded and quantised DCT coefficients are encoded with a new technique. The proposed technique uses the difference of the indexes of the retained coefficients in coordination with DCT block adaptive scanning to encode efficiently the coefficients. The difference of the indexes is stored in a lookup table called (dLUT). When compared with recent methods, the obtained results show that the proposed algorithm achieves high performance.

A robust active contour model is proposed for fast image segmentation. By introducing the intensity fitting energy in a local region, the proposed model can segment the images with intensity inhomogeneity efficiently. Since the local fitting functions are computed before curve evolution, the proposed model is insensitive to initialisation and has a high segmentation efficiency. Experiments on several synthetic and real images have proved the effectiveness of the proposed model.

The task of automatically configuring classifier ensembles as a multi-label classification problem and investigate a meta-learning approach to cope with it is modelled. More specifically, the role of the meta-learner is to recommend the types of components that should comprise the best ensemble model for coping with a given classification problem. Since different component types may be appropriate for each case, advocate that modelling the meta-learner's task as a multi-label classification problem can be useful. To systematically validate this hypothesis and the results confirm the suitability of configuring classifier ensembles via multi-label meta-learners.

Using uniform circular array, a passive localisation algorithm is presented for the scenarios where both far-field and near-field narrow-band signals may exist synchronously. The differencing matrix and the orthogonal projection matrix of the signal subspace are built to classify the mixed signals and to estimate the 2D direction-of-arrivals (DOAs) of the near-field signals (NFSs). Then, the covariance matrix of signals is decomposed to obtain the noise subspace. Meanwhile, 1D multiple signal classification (MUSIC) is used to estimate the ranges of the NFSs and 2D MUSIC is used to estimate the DOAs of far-field signals (FFSs). Compared with two-stage MUSIC (TSMUSIC), the proposed algorithm can provide higher resolution for the DOAs so that the signals can be separated. In addition, compared with TSMUSIC and four-order cumulant MUSIC, the proposed algorithm has higher accuracy for localisation of both FFSs and NFSs. Simulation results are carried out to verify the performance of the proposed algorithm.

The heterodyne laser interferometer is an ultra-precise measurement apparatus. However, its susceptibility to environmental error is an obstacle to improve its nanometre-scale measurement accuracy. To minimise the environmental error factor, a compensation algorithm using a Lagrange multiplier method is proposed. The improved accuracy of the proposed method was verified by means of experiments using nanometre-scale measurements of a capacitive displacement sensor.

A broadband transition from microstrip line to spoof surface plasmon (SP) waveguide is proposed. The transition transforms the guided wave into a spoof SP polariton in a broad microwave frequency band. A back-to-back transition sample is fabricated using the proposed method. Good agreement between the measurement and simulation is obtained. The measured results show an insertion loss <2 dB and a return loss below −11 dB from 2.2 to 10 GHz. The proposed broadband transition may pave a way for advanced conventional plasmonic integrated microwave devices and circuits.

A stacked plate-capacitor design technique for filters constructed on multilayer substrates is proposed. With this technique, the parasitic effects between capacitors and grounds as well as the parasitic effects between different capacitors can be significantly reduced. The proposed layout can be used in multlayered filters design as a block and the design procedure for filters can be simplified. The proposed layout is analysed in detail. A multilayered filter is designed to demonstrate the design procedure. Both simulation results and measurement results show the effectiveness of the proposed technique.

The potential of an intrinsically microwave tunable resonator consisting in a switchable diode and a stub directly co-designed on the same silicon substrate is presented. Thanks to this substrate, the semiconductors properties can be associated directly to the electromagnetic wave propagation. Compared with the current technology, the absence of soldered components offers a great flexibility in the design of microwave tunable devices. The active element is based on an integrated and distributed N⁺PP⁺ junction which allows the tunability of the resonator by simply applying a low bias voltage. It is demonstrated that high doping levels of the diode and resonator can lead to good performances. Two stubs, switchable from open-ended (λ/2 at 4 and 3 GHz) to short-ended (λ/4 at 2.1 GHz) using a low bias voltage, were designed, fabricated and characterised. A good agreement was obtained between simulations and measurements and each resonator presents insertion losses lesser than 2 dB.

Two innovative single-ridge waveguide to rectangular waveguide transitions with integrated 90° E-plane bend are proposed. Since a single-ridge waveguide standard is not available, such components become necessary whenever this technology is employed. Wideband performance, extreme compactness and easy manufacturing are core characteristics. The presented devices operate at Ku band, though the designs are fully scalable to any other frequency band of interest.

Spatial division multiplexing elastic optical networks (SDM-EONs) will become the most important form of future optical transport networks, because it can break the physical limit of achievable capacity in single-mode and single-core fibre. However, spectrum fragmentation issue becomes more serious in SDM-EONs compared with in single EON. Crosstalk-aware cross-core virtual concatenation (CCVC) scheme is first proposed to solve the spectrum fragmentation issue in SDM-EONs. Simulation results show that CCVC can achieve lower blocking probability and higher spectrum utilisation compared with single-core virtual concatenation scheme.

Electro-optic (EO) properties at 7 K of a guest–host type nonlinear poled polymer system consisting of AJLZ53 chromophores in an amorphous polycarbonate host are reported for the first time. A modified attenuated total reflection method that takes into account multilayer structure is used to accurately characterise linear and nonlinear optical properties. At the telecommunication wavelength of 1550 nm, <10% drop of the EO coefficient r ₃₃ at 7 K is observed compared with that at 300 K, while n ³ r ₃₃ only decreases <5% because of increased anisotropic indices of refraction at low temperatures. This decrease of the r ₃₃ at 7 K indicates that the EO activity of nonlinear polymers at room temperatures is not of pure electronic origin because of vibrational mode contributions to the first-order hyperpolarisability.

Infrared light detection capability of a hydrogenated amorphous silicon waveguide with a vertically stacked pin structure by utilising defect absorption, i.e. transition between dangling bond defect and extended states is demonstrated. The responsivities for a 0.6 mm-long device are ∼6.2 and ∼0.22 mA/W at 1300 and 1550 nm wavelength, respectively.

A triple p–n junction Si photodetector using 0.25-μm standard CMOS process at 650- and 850-nm wavelengths is presented and investigated. Triple p–n junctions are formed vertically by n⁺-implant/p-well (N+/HVPW), p-well/n⁺-buried layer (HVPW/NBL), and n⁺-buried layer/p-substrate (NBL/P-sub) junctions to attain a wavelength-dependent response. The responsivity and pulse response were characterised in different bias schemes. Measured photocurrents from HVPW/NBL and NBL/P-sub junctions under reverse biasing and a floating electrode on N+-HVPW showed the smallest FWHM values. The −3 dB bandwidth of 1.9 GHz converted from pulse measurement is the highest result ever reported in 654-nm wavelength using standard CMOS technology. The proposed triple p–n junction Si photodetector with bias schemes shows combined excellent performance in 650- and 850-nm wavelengths.

A 10 GHz mode-locked fibre laser has been treated to improve its stability and the quality of generated pulses. An unpumped 3 m erbium-doped fibre (EDF) is incorporated outside the cavity at the output of the mode-locked laser and a setup is designed so as to form the strong standing waves inside the EDF that leads to spatial hole burning effect. This reduces the phase noise of the mode-locked laser, resulting in the timing jitter reduction from 260 to 130 fs.

Bi-frequency (BF) control for LLC resonant converter is proposed and studied. Compared with conventional voltage mode control of LLC resonant converter, which realises output voltage regulation by adjusting control pulse frequency cycle by cycle, BF control of LLC resonant converter realises its output voltage regulation by adjusting the combination of two preset control pulses with 50% duty ratio and different switching frequencies. BF controlled LLC resonant converter benefits from simple controller design and fast transient response. A 130 W prototype is presented to verify the analysis results of BF control method.

A design of controllable power limiter (CPL) using parallel reverse polarities Schotty diode is introduced. The main characteristic of the proposed PL are controllable, be difference with traditional PLs, the turning point is controllable and depend on the applied bias voltages on the diodes. For verification, a CPL using symmetry structure, with two controllable bias voltages, operating range from 1.9 to 2.7 GHz is fabricated. The measured results proved the feasibility of design, with <3 dB small signal insertion loss during the whole bandwidth the PL can limit output power at the level under 12 dBm while the large input power ranges over 30 dBm.

The main challenge associated with the grid-connected inverter (GCI) in distributed generation systems is keeping the harmonic content of the output current below the specified value and compensating for unbalanced loads even when the grid is subject to disturbances such as harmonic distortion and unbalanced loads. To overcome these challenges, a current control strategy for a three-phase GCI under unbalanced and nonlinear load conditions is presented. The proposed control method enables the GCI to inject balanced and clean currents to the grid even when the local loads are unbalanced and/or nonlinear; it also compensates for the harmonic currents and controls the active and reactive powers. The main advantage and objective of this method is to effectively compensate for the harmonic current content of the grid current and microgrid without the use of any compensation devices such as active, passive and LCL filters.

A high voltage conversion ratio interleaved boost converter is proposed with connecting input in parallel and output in series. By introducing coupled-inductor and diode-capacitor techniques, the converter can further extend the voltage gain. Because of the interleaved structure, the input current ripple can be reduced significantly, alleviating the electromagnetic interference problem. The test results of a 200 W prototype are provided and high efficiency above 93.5% is achieved.

Based on analysing the load currents, a current sensor fault diagnosis method for three-phase voltage source inverters in high-speed railway electrical traction drive system is presented. Then, a fault-tolerant algorithm is applied to reconstruct the three-phase currents. This fault diagnosis and tolerant control approach is an extension of the normalised average currents method, which requires no additional hardware and permits much more robust diagnostics. Experimental results confirm the effectiveness and accuracy of the proposed algorithm. It is shown that such diagnosis method can locate the faulty sensor, identify the fault modes, and recover the drive system in a fundamental period which is important to avoid catastrophic consequences.

A new Doppler ambiguity resolver (DAR) is proposed for ground moving targets of synthetic aperture radar. After range migration correction in range–Doppler domain based on a static target, it is found that the absolute value and the sign of Doppler ambiguity integer can be determined according to the range blur and the inclination direction of a moving target signal response, respectively. The range blur based DAR is computationally efficient and works better in many scenarios compared with the existing Radon transform based DAR in 2D time domain. Finally, some numerical experimental results are provided to demonstrate the effectiveness of the proposed method.

A general two-phase segmentation model (beta-CCV) for synthetic aperture radar (SAR) images is introduced. The proposed model is based on the beta-divergence similarity measure and the convex-relaxed Chan–Vese model. The main advantage of beta-divergence with non-positive value of beta is that it is an expedient similarity measure for high dynamic range SAR images with strong scatterers. In addition, due to the global optimum property of beta-divergence, naturally merge the beta-divergence similarity measure into the convex-relaxed Chan–Vese model. Hence, we can find solutions of beta-CCV in a more stable way through convex optimisation. The proposed beta-CCV model shows overall better performance than the state-of-the-art segmentation method.

An improved algorithm for power-inversion adaptive antenna arrays used in global navigation satellite systems (GNSS) receivers is proposed. Compared with traditional methods which select the reference element arbitrarily, the proposed method is capable of selecting the optimum reference element at signal acquisition stage. The criterion of the reference element selection is to maximise the acquisition test statistic results by developing the generalised likelihood ratio test detector. Monte Carlo simulation results show that the proposed method can improve the array performance significantly.

A novel radar high resolution range profile (HRRP) recognition method based on discriminant deep autoencoders is proposed to enhance the classification performance with limited training samples. Compared with the conventional models, the proposed method not only extracts high-level feature which can reflect physical structure of HRRP, but also trains HRRP samples globally to reduce the requirement of the training data. The experiment based on the measured data demonstrates the physical meanings of the extracted feature. Moreover, the recognition performance of the proposed method consistently outperforms the conventional models, and the improvement become more significant with smaller training data size.

Moving relays (MRs) have been proposed as a promising technology to improve the coverage performance of vehicular users. However, how MRs can influence non-vehicular users is not yet studied. Using stochastic geometry, statistical analyses on the coverage performance of non-vehicular users in the MR enabled cellular networks are made. An analytical framework for analysing downlink signal-to-interference ratio under the presence of MRs is developed. Based on the proposed framework, tractable expressions for coverage probability of non-vehicular users connecting to MRs and macro base stations are derived, respectively. Simulation results verify the derived expressions. These analytical results show that non-vehicular users can also improve their coverage performance by the MRs.

Quadrature spatial modulation (QSM) is a recently proposed multiple-input multiple-output transmission scheme which improves the spectral efficiency of classical spatial modulation (SM) by increasing the number of information bits transmitted by antenna indices. In QSM, a complex data symbol is decomposed into its real and imaginary components; then, these two components are independently transmitted using the SM principle. A low-complexity, near-maximum likelihood (ML) error performance achieving detection scheme is proposed for QSM to reduce the overall computational complexity of the ML detector. First, the proposed detector determines the set of most probable active transmit antennas and the corresponding possible transmission patterns. Then, ML-based detection is used to determine the transmitted complex data vector by performing a search over these transmission patterns and M-ary constellation symbols. It has been shown via computer simulations that the proposed detection algorithm exhibits near-ML bit error rate performance with considerably lower decoding complexity.

The multiple-input multiple-output (MIMO) cooperative networks with selective orthogonal frequency division multiplexing access (OFDMA) relaying, where transmit beamforming and maximum ratio combining are carried out at source transmission and destination reception, respectively, are considered. The closed-form expression of outage probability is investigated to statistically assess the performance of systems. The impact of number of relays on the outage performance under arbitrary Nakagmi-m fading channels is analysed. Results reveal that increasing the number of relays is not always necessary for the improvement of outage performance and there has been the right relay configuration to guarantee the outage performance and reduce the complexity for relay networks.