Conformal metal reflectarray antennas on the surface of a cylinder are designed for millimetre-wave applications. All depths of metal grooves in the reflectarrays are specially manipulated for high-gain conformal reflectarray antennas. There is a good agreement between simulated and experimental radiation performance results for two different ‘sagittas’. The proposed conformal reflectarray antennas can be a helpful choice for applications requiring high-gain antennas on curved platforms.

The design results of an H-shaped fractal antenna for application in multi-band microbolometers and the thermal performance estimation result of the microbolometer are reported. The H-shaped fractal antenna has been designed for wavelengths of 25 and 150 μm based on a dipole antenna formula and finite element method (FEM) simulation. Simulation results show that the absorption peaks exist at 27 and 150 μm. To verify the absorption characteristics of the designed antenna, the antenna was fabricated and the absorption characteristics for the x-polarised incident wave radiated from the + z-direction were measured. The measured transmittance dips at 27 and 146 μm almost agreed with the absorption peaks of the simulation results. The thermal performance estimation of an H-shaped fractal antenna-coupled VO₂ microbolometer and obtained voltage sensitivities of 0.63 and 4.81 mV/(W/m²) at 27 and 150 μm absorption peaks, respectively, are also presented.

A differential-fed microstrip antenna, which is characterised with an ultra-wideband (UWB) of 120% (3–12 GHz), improved radiation patterns, stable gains and compact size, is proposed. Two symmetrical trapezoid-shaped slots and four triangle-cut corners on the ground are used to improve the impedance matching over the UWB frequency band. To clarify the improved radiation characteristics, the simulated 3D radiation patterns of the proposed antenna are also shown. The measured results show that, in the entire frequency band, the designed antenna exhibits a stable radiation pattern and the gain variation is < 2.5 dB. Furthermore, the polarisation purity is increased compared with the conventional ones, especially in the high-frequency band.

A circular phased array antenna that can generate orbital angular momentum (OAM) radio beams in the 10 GHz band is described. The antenna consists of eight inset-fed patch elements and a microstrip corporate feeding network. A full-wave electromagnetic simulator is used to aid the antenna design and theoretical simulations are confirmed by measurements.

A genetic algorithm (GA)-based pattern optimisation of active array antenna (AA) vertical cell splitting system is proposed. In the proposed algorithm, a joint optimisation method of inner cell pattern and outer cell pattern is designed, and GA is applied to optimise the array's amplitude excitations for reducing the interference in AA vertical cell splitting system. The simulation results and performance analysis demonstrate the feasibility and validity of the proposed algorithm. In comparison to the conventional identical-excitation active AA patterns, the optimised results show that significant gain in both cell average throughput and cell edge throughput is obtained.

For dual-arm robot systems, which continue to become more common in the field of industrial robotics, a redundant shoulder complex could be very important to new developments. However, constructing a kinematically redundant shoulder complex is difficult because of spatial constraints. A novel redundant shoulder complex for a human-like robot that is driven by flexible wire tendons against spatial constraints is proposed. The kinematically redundant shoulder complex allows the human-like robot to generate more natural motions because of the availability of redundant degrees of freedom (DOFs), i.e. six DOFs per side. To control the proposed shoulder complex, a hybrid control scheme is used; the positioning precision was considered, and the ability of the shoulder complex to perform several human-like motions was verified.

Electroencephalography (EEG) and deep brain stimulation (DBS), as specific instrument and tool, respectively, for reading and changing the electrical activities of the human brain, are milestones in the history of neuroscience and brain research. Although scientists have gone very far in exploring the brain, the mechanisms of many neurological diseases and therapies are not clear yet. Therefore, an implanted rechargeable EEG device, adding the recording function to conventional DBS to make it not only a therapy device but a scientific research tool has been developed. The EEG performance of the device is good compared with the SynAmps2 of NeuroScan. Radio-frequency (RF) communication at 403 MHz is used for data transmission, which has a high speed and long transmission distance and enables mass quantity data transmission. A rechargeable battery is used for power supply, making the system life longer and lowering the requirement of low-power design. This device is a good platform for neuroscience research by being implanted in animal models of different nervous system disorders or patients with diseases such as Parkinson's disease (PD). The recorded data will help to better understand the brain and the mechanisms of brain disorders and also help to optimise clinical therapy.

An energy-efficient capacitive digital-to-analogue converter (DAC) switching method for a reconfigurable successive-approximation register (SAR) analogue-to-digital converter (ADC) is proposed. The proposed method can achieve a variable resolution starting from 1 bit with 1 bit resolution increments. The proposed method achieves the energy savings due to the fact that the binary-weighted capacitors are merged with the main-DAC, as and when required. When sized for the same thermal noise as the traditional SAR ADC, the proposed method achieves 96.9% reduction in switching energy and a factor of 2 improvement in static linearity performance. If sized for the same static linearity as the conventional SAR ADC, the DAC area could be reduced by a factor of 4, which further improves the switching energy savings to 99.2%.

A foreground digital self-calibration technique that improves capacitor matching of a digital-to-analogue converter (DAC) employed in successive approximation register (SAR) analogue-to-digital converters (ADCs) is presented. By exploiting an antisymmetric behaviour of capacitor mismatch errors in SAR ADCs and the proposed DAC switching scheme, the calibration technique significantly reduces capacitor mismatch errors without resorting to extensive computation or dedicated circuits.

In digital phase-locked loops (PLLs), the finite resolution of digital representation (quantisation) could pose problems, including jitter peaking and limit-cycle behaviour; both could ruin the frequency stability of a PLL. The resolution of the digitally controlled oscillator (DCO) in the PLL is limited by the smallest dimension available in a given process technology. Currently, one resorts to exhaustive time-domain simulations to ensure correct operation of a PLL. Using a behavioural model of a PLL as verification, how to choose the DCO resolution without resorting to time-domain simulations is investigated. The conditions on signal statistics for correct behaviour are repeated and the analysis to estimate the required resolution is provided. As it turns out, the root-mean-square value of the frequency deviation – neglecting quantisation – is the coarsest possible DCO resolution. One can estimate this value accurately by the integration of its power-spectral density, derived from the well-known phase-domain model of a PLL.

The bit cell is a key component that determines the VDD_min and power consumption of a sub-threshold static random access memory (SRAM). A new bit cell with a pnn-type latch structure is proposed. The analysis and measurement results indicate that the pnn bit cell outperforms the conventional bit cells in terms of VDD_min and power reduction.

A one-dimensional (1D) virtual force field (VFF) algorithm for real-time reflexive local path planning of mobile robots is proposed. The 1D-VFF is composed of the virtual steering, obstacle and integrated force fields (IFFs). The steering force field (SFF) is generated by the local or global goal position. This SFF leads a mobile robot to the goal. The obstacle force field (OFF) is created by the raw data of a range measurement sensor (RMS). By this OFF, a mobile robot avoids obstacles. The IFF is produced by combining the steering and OFFs in which weights between 0 and 1 are multiplied. Through this IFF, a final steering command by which a mobile robot reaches a goal by avoiding obstacles is generated. Various simulations compare the performance of the proposed 1D-VFF with the weighted virtual tangential vector (WVTV), which is the recently suggested local path planning method to overcome the U-shaped enclosure problem.

A multi-unmanned aerial vehicle (UAV)-based stereo vision system is proposed to assist global path planning of an unmanned ground vehicle (UGV) even in GPS-denied environments. The proposed system can optimally generate the depth map of ground objects and robustly detect obstacles. The proposed multi-UAV-based system with a movable baseline overcomes the limitations of a single-UAV-based stereo vision system with a fixed baseline. Thus, the performance of the proposed system does not degrade significantly based on the altitude of UAVs. The relative position and altitude estimation, multi-agent formation control and image processing techniques are considered to implement a prototype system. The experimental results demonstrate the performance of the implemented system for various baseline conditions between UAVs.

The bilateral filter (BF) as an edge-preserving lowpass filter is a valuable tool in various image processing tasks, including noise reduction and dynamic range compression. However, its computational cost is too high to apply in the real-time processing tasks as the range kernel, which acts on the pixel intensities, making the averaging process nonlinear and computationally intensive, particularly when the spatial filter is large. Using the well-known Hermite polynomials, a BF accelerating method is proposed, which reduces the computational complexity from O(r ² n) to O(n), where r denotes the filter size of a BF and n is the total number of pixels in an image.

A full-reference image quality assessment (FR-IQA) metric, with emphasis on semantic information changes in different image content areas, is presented. The changes on edge information, that can represent semantic information changes, are calculated based on the characteristics of different image content areas. Considering that edge changes cannot account for luminance changes while luminance changes does affect visual quality of images, the luminance changes are also incorporated into the design of the perceptual quality metric. Experimental results confirm that the proposed metric is consistent with human judgments of quality, and outperforms relevant state-of-the-art metrics across various distortion types.

A method for human action recognition in depth sequence by discovering latent attributes is proposed. Specifically, a latent attribute model to take advantage of the partwise and bodywise action attributes and their concurrence for action modelling is presented. This model can avoid the explicit definition of a completed action attribute set by designing a hidden layer as latent attributes. Moreover, the relationship between pairwise attributes can be adaptively learned in terms of the specific graphical structure without human intervention. Extensive experiments on two popular datasets and a new dataset TJU show the superiority of the proposed method over the state-of-the-arts.

A layer-based random early detection (RED) forward error correction (FEC) method for scalable video streaming over wireless networks is proposed. The proposed method determines the FEC rate in accordance with the layer-based error propagation effect as well as network traffic load. Furthermore, a packet importance model based on layer information of scalable video coding (SVC) has been developed for efficient FEC assignment considering the video quality. Simulation results show that the proposed method achieves higher peak signal-to-noise ratio (PSNR) values compared with the conventional FEC schemes under various network conditions.

A new method for detecting drivable regions in an unrehearsed and unstructured outdoor environment using multi-sensor information is presented. To achieve this goal, two key methods are developed: (i) robust and effective feature definition using colour and geometry and (ii) online learning algorithm using positive samples for detecting drivable regions. With real data sets, the effect of sensor modality is evaluated and is compared the performance of the algorithm to a cluster-based approach.

Single image dehazing using an estimated transmission map for evaluation is proposed. When estimating the transmission map using the conventional dark channel prior (DCP) algorithm and then detecting the haze regions using a matting algorithm, the resulting transmission map invariably includes some block artefacts, as the DCP algorithm is based on patch-based processing. Therefore, a modified transmission map is proposed based on the hidden Markov random field (HMRF) and expectation–maximisation (EM) algorithm. Experimental results confirm that the proposed algorithm is superior to conventional algorithms in image haze removal.

Data outsourcing can make data-integrity protection a challenging task, especially when the trustworthiness of a third-party is unproven. A novel auditing process for integrity verification of data stream, whose storage and handling is outsourced to a third-party, is explored. For this purpose, the hidden information within this data that provides support for in-network data aggregation environments, such as sensor networks is masked. This mask is achieved by simultaneous embedding of several shifted watermark patterns into multiple data streams. The nature of this watermark allows it to be aggregated into a single data stream with minimal loss of this information. A great benefit of the proposed scheme is that the embedded watermarks are invariant to linear time-sequential or cross-stream aggregation operations, such as summation or averaging. Therefore, multiple data streams can be merged and at the same time, and the existence of each individual watermark within allowable bounds can still be verified. The simulation results show that the embedded watermarks can successfully be recovered with high confidence if proper hiding codes are chosen.

When the training snapshots are contaminated by the desired signal, the performance of the orthogonal projection (OP) approach degrades significantly. Therefore, an improved OP adaptive beamforming is proposed by reconstructing interference covariance matrix to eliminate the desired signal cancellation effect. In the proposed method, by integrating the Capon spatial spectrum over a region separated from the desired signal direction, the interference-plus-noise covariance matrix is reconstructed first to remove the desired signal component from the sample covariance matrix. Subsequently, the interference subspace is estimated by eigenvalue decomposition, and then the adaptive weight vector is calculated using the OP algorithm to eliminate the noise perturbation. Simulation results show that the performance of the proposed algorithm is almost the same as the optimum beamforming.

A new approach to greatly reduce the cross-sensitivity of a quartz crystal microbalance (QCM) humidity sensor is proposed. A graphene oxide (GO) membrane, which acts as a filter layer, is added to the sensor structure. Since the GO membrane enables selective permeation of water molecules, the introduction of the GO filter membrane into the sensor structure greatly reduces the cross-sensitivity of the humidity sensor to other gases.

An 80 GHz double-balanced down-conversion mixer for automotive radars using standard 90 nm complementary metal oxide semiconductor (CMOS) technology is reported. The mixer comprises a double-balanced Gilbert cell with inductive source-degeneration radio-frequency (RF) transconductance stage for wideband RF-port input impedance matching and conversion gain (CG) enhancement, a Marchand balun for converting the single RF input signal to differential signal, a Marchand balun for converting the single local oscillator (LO) input signal to differential signal and a baseband amplifier. The mixer consumes 13 mW and achieves excellent RF-port input reflection coefficient of −13.1 ∼ −19.4 dB and LO-port input reflection coefficient of −9.1 ∼ −11.8 dB for frequencies in the range 75–85 GHz. In addition, for frequencies of 75–85 GHz, the mixer achieves CG of −1 ∼1.5 dB, LO–RF isolation of 43.5–49.2 dB and LO–intermediate frequency (IF) isolation of 56.5–64.5 dB, one of the best CG and port-to-port isolation results ever reported for a CMOS down-conversion mixer with operation frequency about 80 GHz.

A 60 GHz power amplifier (PA) based on a 28 nm CMOS technology is presented for WiGig applications. It consists of a two-stage pseudo-differential common-source structure using low-power and low-V _t transistors, capacitive neutralisation for isolation enhancement and integrated transformers for impedance matching, power splitting, power combining and balanced-to-unbalanced transformation purposes. The output-stage transistors have a measured 1 dB output compression point (OCP_{1 dB}) of 10.2 dBm, a 10.2 dB gain and a peak power added efficiency (PAE) as high as 35%. The fabricated PA achieves a 12 dBm OCP_{1 dB}, a 15.3 dB gain and a peak PAE better than 20% while occupying a silicon active area of only 0.037 mm².

A simple transition between a circular waveguide and a coaxial cable having mode-free operation over more than an octave bandwidth is presented. The transition consists of a conical coaxial probe, a rectangular waveguide section and a linearly tapered transformer from the rectangular to circular waveguide. The transition shows a reflection coefficient of < –20 dB, a transmission coefficient of >–0.57 dB and a higher-order mode level of < −25 dB over a frequency range 1.04–2.53 times the TE₁₁ mode cutoff frequency.

A compact ultra-wideband 90° phase shifter based on a short-circuited stub and a weak coupled line (WCL) is proposed. The circuit configuration and derivation of S-parameters and phase difference are presented. The analysis result indicates that the phase deviation (PD) bandwidth can be extended to 200% by adjusting the coupling coefficient of the WCL. The fabricated phase shifter exhibits a bandwidth of 118% from 0.66 to 2.56 GHz for return loss >10 dB, insertion loss (IL) <0.5 dB and a PD of ±3.9°. Comparison shows that the proposed phase shifter not only has the most compact size with single-layer structures but also achieves the largest bandwidth and lowest IL. The design features low-cost, good design portability and convenient installation. Thus it is a good candidate for wideband and ultra-wideband applications.

A compact tri-band bandpass filter is designed by combining a dual-band sub-filter and a single-band one. The dual-band sub-filter comprises four stub-loaded resonators. The single-band sub-filter is inserted into the gaps of the dual-band sub-filter for size miniaturisation. Both the centre frequencies and the bandwidths of the three passbands can be independently controlled. The measurements of the fabricated superconducting filter exhibit high performance and match well with the simulations.

A predistortion method using the adaptive normalised least mean square (NLMS) algorithm is proposed for the estimation of light-emitting diode distortion. The light emission characteristic could change nonlinearly depending on conditions of the physical environment, such as temperature variation, which cannot be ignored, especially in the case of high-power emissions. Instead of using the fixed values of the conventional memory look-up-table (LUT) for nonlinearity compensation, the proposed adaptive NLMS-based predistorter immediately estimates the distortion change according to environmental changes. The simulation results show that the proposed method has better performance than the conventional predistorter employing an LUT.

An inversely aggregated networking with programmable protection (i-ANP²) architecture is proposed to provide a cost-effective and robust optical network. It is shown to reduce more than 50% of capital expenditure (CAPEX) for protected services and the operational cost by several orders of magnitude.

A novel symmetric structure of bipolar charge-plasma transistor (BCPT) is presented. It consists of symmetrical gates with platinum on top of a thin intrinsic silicon film, which forms hole plasma in emitter and collector regions. The base contact is formed with hafnium metal to induce electron plasma; hence, a p–n–p charge-plasma transistor is formed without any doping. The collector area that is chosen is the same as an emitter to make the device symmetrical. 2D simulation results revealed that the proposed BCPT possesses higher collector current and higher current gain than conventional p–n–p bipolar junction transistor (BJT) and almost the same characteristics such as asymmetrical p–n–p BCPT for different geometries. The major challenge of poor cut-off frequency (f_T ) of BCPT is also addressed by optimising the silicon film thickness and intrinsic gaps.

High-performance full transparent bottom-gate type tin-doped zinc oxide thin-film transistors (TZO TFTs) had been successfully fabricated by RF magnetron sputtering on glass substrates at low temperatures. The effect of O₂/Ar gas flow ratio during channel deposition on the electrical properties of TZO TFTs was investigated and an optimised growing condition (O₂/Ar gas flow ratio: 8/92) for TZO film as the channel layer was acheived. Excellent device performance was obtained, with a low off-state current (I _off) of 10⁻¹² A, a high on/off current ratio of 5 × 10⁷, a high saturation mobility (μ _s) of 57 cm²/Vs, a steep subthreshold slope of 0.507 V/decade and a threshold voltage (V _th) of 3.5 V. These results highlight that excellent device performance can be realised in TZO film and TZO TFT is a promising candidate for transparent flat panel display.

The fabrication of metal-base transistors (MBTs) based on InGaZnO at room temperature is reported for the first time. With a suitable oxygen doping to the sputtering-deposited InGaZnO film and an HfSiO interlayer, improved diode performances with enhanced Schottky barrier heights of 0.70 and 0.66 eV are obtained for the base/collector (Ti/InGaZnO) and base/emitter (Au/HfSiO/InGaZnO) junctions, respectively. InGaZnO MBT using a Ti(10 nm)/Au(10 m)/HfSiO(5 nm) dual metal base shows a high common-emitter current gain (β) 840–310 at V _CE = 2 V and I _B ranging from 1 to 10 nA.

A high-performance 1.3 μm InAs/GaAs quantum-dot laser directly grown on Si substrates has been achieved by using InAlAs/GaAs strained-layer superlattice serving as dislocation filter layers (DFLs). The Si-based laser achieves lasing operation up to 111°C with a threshold current density of 200 A/cm² and an output power exceeding 100 mW at room temperature.

The first light source with a broadband spectrum in the 1800 nm wavelength region has been developed by employing a cascade configuration with a 1.65 μm band super luminescent diode and a Tm³⁺-doped fibre amplification unit. The achieved bandwidth where the intensity exceeded -20 dBm/nm was 247 nm (from 1611 to 1858 nm) with a low ripple, whose peak-to-peak value was <0.15 dB.

Orange laser pulses were successfully generated in a Pr-doped waterproof fluoride glass fibre (Pr:WPFGF) using a graphene thin film as a saturable absorber (SA). Two pulse generation modes were observed: a continuous mode with 0.47 µs pulse duration with a 2.61 µs repetition period and a single giant pulse mode with 9.7 ns pulse duration. The peak wavelength was 603 nm. This result shows that a graphene thin film can be effective as an SA in the visible region, and in the future a visible ultra-short pulse laser with a modelocking technique may be demonstrated.

The first demonstration of InSb photodetector with nBn design is reported. The nBn structure, grown by molecular beam epitaxy (MBE) on InSb substrate, is built by using n-type InSb as absorber layer and InAlSb alloy as barrier layer. The nBn detector, showing cut-off wavelength of 5.4 µm at 77 K in photovoltaic mode, exhibits dark current density as low as 10⁻⁹A/cm² at −50 mV reverse bias, at least two decades lower than usual InSb photodiode.

Data are presented showing that lithographic vertical-cavity surface-emitting lasers (VCSELs) produce minimal junction temperature rise compared to oxide VCSELs. Eliminating the thermal block caused by internal oxides combined with improved mirror materials reduces the junction temperature. The elimination of internal oxide, lower junction temperature and reduced internal strain promise increased reliability in the new VCSELs. Power conversion efficiencies in excess of ∼50% are reported, even for very small lithographic VCSELs.

A two-and-a-half-dimensional (2.5D) platform for enabling silicon nano-photonics and dense electrical interconnections between interposers in a tile-like configuration is presented. Three 20 × 20 mm silicon interposer tiles are assembled directly on an FR4 printed wiring board (PWB), and two 6 × 20 mm silicon bridges are assembled on top of the interposer tiles. Accurate alignment of interposer tiles to bridges, an important metric in enabling highly efficient optical coupling, is provided using positive self-alignment structures (PSASs). It is demonstrated that by using PSAS on two silicon substrates, sub-micron alignment between substrates is possible; in the cascaded configuration involving FR4, <5 μm alignment accuracy is obtained. In addition, electrical interconnection via a bridge using mechanically flexible interconnects (MFIs) is demonstrated, which made non-bonding interconnections from one interposer tile to another via a silicon bridge, allowing silicon bridges as well as the interposer tiles to be replaced. Total silicon interposer area available is 960 mm².

A polarisation-independent Bragg grating wavelength filter using polarisation rotation is reported. A rib waveguide Bragg grating structure and second-order mode are used to generate the polarisation rotation. A device connected to polarisation beam splitter (PBS) to obtain a polarisation-independent device is fabricated. The measured diffraction wavelength peaks were almost the same for both input polarisations.

Distributed wind generation (DWG) with increasing permeability has brought an adverse effect to grid security. The battery energy storage system (BESS) can solve this problem. However, the system reliability may be limited by the improper locations of switches. To make full use of BESS, a coordinated planning model of BESS and controllable switches (CSs) is developed for distribution networks. The objective is to minimise overall cost including investment cost, operation cost, network loss, insufficient power supply cost and energy price arbitrage, while satisfying security and BESS limitations. The simulation results show that the model proposed is effective.

On the basis of the technique of time reversal (TR), a new method for low dielectric contrast target detection in clutter by adding dispersive delay lines (DDLs) to each element of the TR mirror (TRM) is proposed. When compared with a conventional TR system, the proposed method improves refocusing to a target by reducing the impact of other scatterers in the environment. The proposed method makes it unnecessary to estimate the position of the target and removes the need for subsequent subtraction as traditionally required. Theoretical and numerical simulated results demonstrate the proposed method.

A 1.8 mW wideband common-gate (CG) low-noise amplifier (LNA) with double capacitor-cross-coupled (CCC) feedback is presented for multiband wireless communication standards. To achieve a low-noise figure (NF) and high-voltage gain under low power consumption, the CG LNA is based on the double CCC feedback and current-reuse techniques. Post-layout simulated results for 0.18 μm CMOS implementations show that the voltage gain is 18.1 dB with a 3 dB bandwidth from 100 MHz to 1.7 GHz and the IIP3 is −4.9 dBm at 1 GHz. The average NF is 2.4 dB within the entire 3 dB bandwidth. The LNA consumes 1.8 mW from a 1.8 V DC supply and the active size is 0.15 × 0.14 mm².

Today, the vast majority of personal communication devices, such as laptops, smartphones, and logically wireless fidelity (Wi-Fi) access points feature IEEE 802.11 chipsets. In turn, wake-up radio (WuR) systems are used to reduce the significant energy waste that wireless devices cause during their idle communication mode. A novel WuR system is introduced that enables any IEEE 802.11-enabled device to be used as a WuR transmitter without requiring any hardware modification. The corresponding developed WuR receiver achieves a remarkably low power consumption of 10.8 μW and operates in the Wi-Fi 2.4 GHz band. By means of thorough physical tests, it is shown that the proposed IEEE 802.11-based WuR system enables important energy savings.

A novel microstrip diplexer for global system of mobile (GSM) and wireless local area network (WLAN) bands using common shorted stubs is proposed. Two transmission zeros on both sides of the passband response can be easily realised for each passband. Additional transmission zeros created by the shorted stubs are introduced to suppress the harmonic of the microstrip diplexer. A microstrip diplexer with high isolation and selectivity can be achieved by locating the transmission zeros of each channel. A microstrip diplexer prototype with 30 dB isolation from 0.1 to 6.0 GHz has been designed and fabricated.