A novel non-negative matrix factorisation (NMF)-based subband decomposition in frequency–spatial domain for acoustic source localisation using a microphone array is introduced. The proposed method decomposes source and noise subband and emphasises source dominant frequency bins for more accurate source representation. By employing NMF, delay basis vectors and their subband information in frequency–spatial domain for each frame is extracted. The proposed algorithm is evaluated in both simulated noise and real noise with a speech corpus database. Experimental results clearly indicate that the algorithm performs more accurately than other conventional algorithms under both reverberant and noisy acoustic environments.

A frequency-reconfigurable antenna based on aperture tuning using a coupled aperture structure on which a digital variable capacitor (DVC) is connected is presented. The coupled aperture structure is used to avoid electrical contact between the antenna radiator and the DVC in order to reduce antenna efficiency degradation due to ohmic losses at the DVC. The operating frequency is 700 MHz where the antenna efficiency is sensitive to the ohmic loss in the DVC. Analysis based on measurements and simulation confirm the benefits of using the coupled aperture structure over the conventional aperture tuning. It is shown that the coupled aperture plays a key role in reducing the impact of the equivalent series resistance of the DVC component on the antenna efficiency at 700 MHz.

The design of a small printed slot antenna for ultra-wideband application is presented. The antenna is simply formed by an L-shaped slot embedded at the centre of the ground plane, a 50 Ω microstrip-fed line, a rectangular slit connected with the L-shaped slot and another rectangular slit at the bottom of the ground plane. The antenna has small dimensions of 16 × 28 × 0.8 mm³. The impedance bandwidth with 10 dB return loss of the antenna is from 3.1 to 10.6 GHz, in which there is two rejected bands which cover 3.3–3.73 and 5.15–5.9 GHz.

A differential-fed ultra-wideband patch antenna with triple band-notched characteristics is proposed. The antenna consists of an octagonal slot ground and two quasi-square radiating patches. By employing split-ring resonators (SRRs) etched on the radiating patch and complementary SRRs etched on the ground plane, triple-notched bands are obtained to filter the 3.5 GHz WiMAX, 5.5 GHz WLAN and 8 GHz ITU bands. The measured 10 dB impedance bandwidth is from 2.55 to 10.86 GHz, along with triple-notched bands of 3.21–3.86, 4.93–6.13 and 7.87–8.89 GHz. In addition, the proposed antenna achieves relatively low cross-polarisation and stable gain. Good agreement is achieved between the simulated and the measured results.

A Fabry-Pérot cavity antenna based on a dual-layer partially reflected surface (PRS) structure is designed, fabricated and measured at 80 GHz (band-E). The PRS is composed of two frequency selective surfaces, each comprising a periodic array of square metallic patches. When excited by a single primary source, the antenna's gain and directivity increase by ∼10 dB from 81 to 86 GHz. The dimensions of the prototype compact antenna are 100 × 100 × 4 mm³.

A low-profile omnidirectional patch antenna operating in the dependent surveillance – broadcast band is designed for unmanned aerial vehicles. The antenna works at zero-order resonance mode and has an omnidirectional radiation pattern. By loading with vias and double split ring resonator slots, a compact size (0.218 × 0.218 × 0.031 λ ₀ ³) is achieved at 1.09 GHz. The antenna is fabricated and measured. The measured results agree well with the simulated ones. A 20 MHz bandwidth is obtained.

A new method for the wireless monitoring of a battery-free threshold temperature sensor based on a passive ultra-high-frequency radio-frequency identification (RFID) tag integrated with a bimetal thermostat switch is presented. The strategic placement of the switch brings about a strong modification in the tag antenna impedance as the temperature crosses over a threshold value. Optimisation of the narrow-band tag antenna to operate at the edges of the 902–928 MHz frequency-hopping spread spectrum RFID in the different switch states provides separate sub-bands for the readout above and below a threshold temperature. The results show that this enables an unambiguous sensor readout by monitoring the backscattered signal strength.

The common mode rejection ratio (CMRR) strongly depends on matching and this effect is clearly visible in multichannel recording systems. Therefore, a method for improving the CMRR in multichannel recording integrated circuits (ICs) dedicated to biomedical experiments is reported. The method is based on balancing the amplifier's inputs using leakage currents. The proposed technique was verified in the 64 channel IC processed in CMOS 180 nm. The measurement results show that with use of the proposed balancing technique the CMRR is increased by more than 30 dB. Additionally, in comparison to conventional CMRR measurement methods, the proposed solution is attractive in three ways: its on-chip implementation simplicity, fast operation, and it is especially suitable for modern nanometre processes.

The design, implementation, and verification of a signal simulator for the generation of patho-physiological records of foetal electrocardiograms (fECGs) during the prenatal period are briefly reported. The simulator enables users to model the patho-physiological changes that occur within the foetus’ myocardium under hypoxic conditions (hypoxemia, hypoxia, asphyxia, etc.) during the 20th to 42nd week of pregnancy. The simulator deploys a dynamic fECG model including an actual fECG record taken from clinical practice, patho-physiological cardiotocography (CTG), and ST-analysis (STAN) records along with the ratio of T waves to the QRS complex; as well as clinical recommendations by FIGO (International Federation of Gynecology and Obstetrics) for classifying these records. By comparing synthesised and real patho-physiological CTG and STAN records, the functionality of the simulator, which effectively captured significant indicators of the foetus’ condition during the prenatal period including fECG morphology, dynamic fECG characteristics, and others is evaluated and validated. The simulator enables users to test both current and emerging approaches in a very challenging area of gynaecology, namely the identification/classification of hypoxic conditions in the foetus during labour. Obstetricians can also use the simulator as a reference tool during the evaluation of suspect fECG abnormalities.

Total variance-(TV) based compressed sensing MRI (CS-MRI) reconstruction methods are effective in restoring a magnetic resonance (MR) image structure from undersampled k-space data. However, the local details of MR images are usually oversmoothed such that block effects are easily caused. Fortunately, the problem can be overcome by the non-local total variation (NLTV), which is highly effective in keeping fine details and sharping image edges. Nevertheless, NLTV is not good at finding similar patches. Considering TV and NLTV are complementary, it is proposed to use them alternatively instead of combining them in one objective function for CS-MRI. In one alternation, the objective function containing the TV and the wavelet regularisations is firstly used to build the structure of the reconstructed MR image through running several iterations of the optimisation method and then the objective function including the NLTV and the wavelet constraints is used to remove the blocking effects and to preserve the image details through running only one iteration of the optimisation method. A number of alternations are run to find the final reconstruction image. Experimental results validate the effectiveness of the method regarding both reconstruction accuracy and computation complexity.

Non-rigid registration of lung computed tomography (CT) images is a valuable tool for various clinical applications. Many methods such as bilateral filters and census transform have been used to deal with discontinuity of lung motion and local intensity variation. However, census transform cannot distinguish between low and high contrast regions, which may lead to negative influence to differential-based registration methods. A novel distinctive local binary pattern that can generate distinctive representations of high contrast images is proposed. Combing the novel local binary pattern, bilateral filters, the inverse-consistent symmetrical method and the Lucas–Kanade method, a novel accurate image registration method is developed. The experiments are performed on the publicly available 4D CT lung dataset from DIR-Lab. Compared with the census transform, the proposed distinctive local binary pattern can achieve relatively better results. The proposed image registration method greatly improves the accuracy of the classical Lucas–Kanade method and the bilateral filters-based Demons. In addition, the proposed registration method is most accurate among all unmasked methods tested on this dataset.

Here the authors explore, implement and verify the potential utility of hybrid intelligent adaptive systems for processing and analysis of multi-channel non-invasive abdominal foetal electrocardiogram (fECG) signals. This approach allows clinicians to enhance non-invasive cardiotocography (CTG) with continuous ST waveform analysis (STAN) of fECG signals to improve intrapartum monitoring during labuor. The system uses a multi-channel adaptive neuro-fuzzy interference system with a new hybrid learning algorithm based on uniquely synthesised data, which comports well with real data acquired from clinical practice. The system allows the user to obtain a reference signal for objective verification. The functionality of the system has been evaluated not only by subjective criteria (an fECG morphology study by a gynaecologist), but also by objective criteria using quantitative performance metrics such as input and output signal-to-noise ratios, root mean square error, sensitivity S ⁺, and positive predictive value among others. Experimental results indicate that hybrid neuro-fuzzy systems have the potential to improve the diagnostic and monitoring qualities (sensitivity and specificity) of fECG signals while preserving their clinically important features by leveraging the combined utility of non-invasive CTG and STAN.

The detection and quantification of protein on a laser written flexible substrate for point-of-care applications are described. A unique way of etching gold on polyethylene terephthalate (PET) substrate is demonstrated by reducing the damage that may be caused on PET sheets otherwise. On the basis of the quantity of the C-reactive protein (CRP) present in the sample, the risk of cardiac disease can be assessed. This hsCRP test is incorporated to detect the presence of CRP on a PET laser patterned biosensor. Concentrations of 1, 2, and 10 mg/l were chosen to assess the risk of cardiac diseases as per the limits set by the American Heart Association.

Polymerase chain reaction (PCR) chips consume less power and reagent, and are cheaper and easily integrated. In most PCR chips, the heater and the thermometer are placed on the same surface, which causes significant temperature sensing error caused by radiation from the heater. Most microchannels are fabricated through expensive processes of polymer mould-replication, etching or lithography. Some polymers used to form the chamber have bad bio-compatibility and suffer air bubbles when heating. A novel PCR chip with a glass structure is proposed. Grooves are machined on top of the glass substrate, and the glass capillaries are embedded in the grooves to form the static chamber. On the bottom of the glass substrate, the heater is patterned. The substrate with capillaries embedded is covered by a glass slice. The thermometer is fabricated on the bottom surface of the slice. The glass substrate and slice are joined by thermal conductive adhesive. In the PCR chip, the parts except the glass capillaries are reusable. DNA amplification experiments show that the PCR chip works fairly well. The proposed PCR chip has the characteristics of better temperature sensing precision, low cost, no air bubbles, good tightness and bio-compatibility. It is very suitable for home diagnosis use.

A prototype of phonetics learning application based on neurofeedback is presented. The learner's auditive discrimination of chosen phonemes is evaluated using his EEG response to auditory contrasts in an oddball paradigm experiment. When auditory contrasts distinction takes place, the well-known mismatch negativity (MMN) potential registered presents a negative amplitude while zero or positive amplitudes indicate that the participant is not able to discriminate among phonemes. MMN can be processed or directly presented as user feedback, depending on the target-user profile (age, special needs, learning abilities etc.). The paradigm of application presented has many potential usages as phonetics learning tool given its capacity to automatically (i) evaluate the phonetic discrimination providing feedback, (ii) adapt to the individual needs/challenges of the user based on that feedback and (iii) keep track of the improvements achieved.

A new blind calibration scheme for M time-interleaved analogue-to-digital converters (ADCs), which models gain, time-skew and bandwidth mismatches as components of a transfer function mismatch, is proposed. Numerical results on the emerging generation of WiFI IEEE 802.11.ac with 12-bit ADCs show the effectiveness of the method.

A new architecture to multiply signals with time-mode representations is proposed. The exponential relationship between voltage and time in an RC circuit is utilised to implement the time-mode logarithmic and exponential functions needed to realise a time-mode analogue of the translinear principle. The addition of time-mode variables is achieved through the natural progression of time equal to the sum of the input times. By combining these two techniques, an analogue multiplier can be implemented almost exclusively with passive circuits and digital primitives. Therefore, the circuit performance could benefit from CMOS scaling trends. The architecture is described, and simulation results are presented for an operational circuit implementing this approach.

The use of bidirectional temperature sweeping methods in a standard circuit simulator to determine the presence or absence of multiple equilibrium points in analogue circuits is discussed along with the need for start-up circuits to eliminate undesired stable equilibrium points. Signatures in the temperature characteristics of circuits that may have more than one equilibrium state in their resistive circuit and that are indicative of specific types of performance are identified. It is shown that circuits with some of these signatures present significant challenges for circuit simulation and verification when designed to operate at a single equilibrium point. It is also observed that circuits with some of these signatures can exhibit useful circuit properties but also provide vulnerability to harbour analogue hardware Trojans that can be very difficult to detect.

A transconductance improvement technique for a bulk-driven operational transconductance amplifier (OTA) working in the weak inversion region is presented. Using the quasi-floating gate method, the proposed technique achieves larger transconductance improvement than conventional approaches with the CMOS technologies scaling. Moreover, its enhanced performance is at no expense of the power budget. Simulated on UMC 180 nm technology, the results demonstrate that the proposed bulk-driven OTA achieves more than two times gain–bandwidth improvement than that of the traditional counterpart with the same power.

In processor power management research, workload prediction is a requisite for adjusting frequency without performance loss, and previous studies have proposed various prediction algorithms. Among them, methods based on the workload history table are lightweight and have high prediction accuracy for a variable workload. However, such prediction algorithms lose their prediction accuracy in the case of repeated workload. An improved workload prediction method using run-length encoding is proposed, which handles workload repetition. Evaluation results show that the proposed algorithm improves the prediction of repeated workload by up to 14% and also improves 4% of energy saving.

This Letter proposes an extended disturbance observer (EDO) based adaptive robust control method for motion control of DC motors. An adaptive part for structured uncertainties, an EDO for unstructured uncertainties and a feedback robust law for global robustness are designed in this method. The theoretical analysis guarantees a prescribed tracking performance under various uncertainties and comparative numerical simulation shows the excellent high-precision performance of proposed method on DC motor motion control.

A novel vertical channel damping loop design method that uses not only a depth sensor but also a Doppler velocity log (DVL) for underwater vehicles is proposed. In the proposed method, the loop gains are calculated by adopting the steady-state Kalman filter gain with consideration of characteristics of the depth sensor and the DVL. The simulation results demonstrate that the proposed method achieves better performance than the conventional method.

Variable speed systems have been widely applied to home appliances. One of the applications is vector control scheme of a washing machine using low-resolution hall sensors. Vector controller with binary-type hall sensors is cost effective. However, due to electrical and mechanical non-uniformity related to hall sensors, the position obtained by hall sensors does not change linearly, and resultant bumps in the position information degrade control performance. To solve this problem, a new position observer that generates linearly changing position signal is proposed. The proposed scheme removes necessity of knowing mechanical parameters and additional calculation process by utilising a Kalman filter for speed detection. The feasibility and effectiveness of the proposed algorithm are verified through experimental results carried out with a washing machine.

In today's state of the art compact vapour-cell atomic clocks relying on the pulsed Ramsey-type interrogation, optical detection noise is a major limitation to the achievable short-term stability. In this communication, the influence of the optical detection time on the clock's short-term stability is investigated and a new analytical expression is developed to precisely predict the stability performance, taking into account the details of the optical detection phase of a Ramsey-type atomic clock. The theory is in good agreement with the experimental results. It is applied for evaluating the clock's shot-noise limit.

Stationary frame (AC) currents behaviour of three-phase converters with synchronous frame (DC) controllers shaping is explicitly linked. It is revealed that closed-loop synchronous frame dynamics determines amplitude behaviour of stationary frame signals without affecting their frequency and phase. Consequently, synchronous frame current controllers design should actually be based on desired stationary frame amplitude transient performance.

A multi-wavelength channel distributed feedback laser diode array (DFB-LDA) for the low-cost and low-power consumption applications of WDM-based datacentre networks is reported. The gain spectrum and lasing wavelength of each channel are controlled by using selective area growth and E-beam lithography techniques, respectively. To reduce the operation current and parasitic capacitance of the proposed array, an etched mesa buried hetero-structure (EMBH) is introduced. From this study, it was found that an eight-channel 300 μm long λ/4-shifted DFB-LDA has a threshold current of 10 ± 1.5 mA and a side mode suppression ratio of over 50 dB at a current of 50 mA for all channels. A transmission test for this LDA showed a clear eye opening with a dynamic extinction ratio of over 4.5 dB at 10 Gb/s after a 2 km transmission.

A novel robust diagonal loading (DL) algorithm against steering vector mismatch is proposed. The beam-to-reference ratio is estimated first and then used as a weighting factor for variable DL. The Bayesian framework is applied eventually to obtain the weight vector. In contrast to traditional methods, the proposed method achieves good performance without using any optimisation toolboxes or matrix eigendecomposition operations.

Radar cross-section (RCS) measurements of complex, large objects are usually performed on scale models so that the measurement is carried out in a well-controlled environment. The feasibility of RCS measurement using a terahertz (THz) quantum cascade laser (QCL) via laser feedback interferometry is explored. Numerical simulations show that the RCS information embedded in the nonlinear interferometric signals obtained from simple targets can be retrieved through numerical fitting of the well-known excess phase equation. The method is validated experimentally using a THz QCL and the results are well matched with those obtained from numerical simulations.

Existing single image dehazing techniques have limitations on estimating accurate transmission maps for pixels which do not meet the assumption of the dark channel prior. A combined constraint is presented for single image dehazing by taking both geometric and natural characteristics of outdoor images into consideration. The combined constraint can be applied to various regularisation-based optimisation frameworks. Both qualitative and quantitative comparisons with the state-of-the-art dehazing approaches indicate the superiority of the proposed constraint.

Among thriving cyber physical systems, smart camera applications require to run both image sensors and image signal processors (ISPs) to capture images whenever necessary. Owing to the nature of such applications (i.e. constantly capturing images and analysing the images to detect any event of interest), the image sensor and ISP become the two most energy consuming components in smart camera applications. It is started with the intuition that the perceptive quality of images is not strongly correlated with the accuracy of object detection algorithms and a technique that requires only minor modifications to the baseline ISP is proposed but notably reduces the ISP energy consumption in object detection mode for smart camera applications. It is demonstrated that the ISP reduces energy consumption by 33% compared with the baseline ISP energy while degrading face detection accuracy by only 3%.

To achieve efficient coding while maintaining the quality of rendered views, a frame-compatible coding scheme for two-view depth video is proposed. The idea is to remove the redundancy within the inter-view depth video before packing and encoding. The content in two views is analysed after performing view warping from the primary view to the secondary view. The uncovered region is defined as the missing region where no corresponding information can be found in the primary view. Only the uncovered region is retained in the secondary view and will be combined with the primary view to form a frame-compatible video. The experimental results indicate that the proposed scheme outperforms the conventional frame-compatible technology in providing better objective and subjective quality.

Two novel approaches for depth map upsampling are presented. A depth upsampling method using image decomposition is first proposed. Most of previous depth upsampling techniques have suggested the use of colour image as a guide. Unlike the conventional algorithms, the method decomposes the colour image into its structure and texture layers, and then makes use of the structure component instead of the colour image in the reconstruction of depth values. Furthermore, the structure information-based method is extended to a hybrid depth upsampling approach, which takes the advantages of both structure and colour maps. Experimental results demonstrate that the proposed depth map upsampling methods perform better than the previous algorithms in terms of the bad pixel rate.

Segmentation from document images with a complex background is presented. The background component is estimated by low-rank modelling. With the estimated background component, the original image is further transformed into a compensated image which is easily segmented with Otsu's thresholding algorithm to obtain a good binarisation result. Experiments on the Bickley diary and the DIBCO 2013 datasets validate the feasibility of the proposed method.

Existing dehazing methods sometimes produce bluish artefact when the transmission is wavelength-dependent. In this Letter, a single image dehazing method in which transmissions of RGB colour channels are estimated using inter-channel correlations is proposed. The proposed method estimates a particle size parameter in the atmosphere using the correlation between red and blue channels. The proposed method adjusts the transmissions of red and blue colour channels with respect to the reference (green) colour transmission that is obtained by the existing dehazing method. Experimental results with a number of foggy and thin hazy images show that the proposed method effectively reduces the bluish artefact.

Reconstructing a three-dimensional (3D) structure from a single image sequence to provide relevant contextual information for better human visual perception is a fundamental problem in computer vision. A 3D scene estimation methodology from a segmented image sequence that is learned from semantic priors is proposed. In particular, semantic information including 3D geometric characteristics can very efficiently predict the 3D structure of the scene from a given semantic region. The approach, which utilises semantic priors to estimate a 3D scene, is very robust for direct 3D scene reconstruction from an ambiguous depth map. The efficiency and effectiveness of the proposed approach has been proven experimentally with a large database.

A new method for supervoxel segmentation based on a weighted graph in complex urban environment is proposed. The proposed algorithm is designed to minimise the cost of the shortest path in the weighted graph with consideration of characteristics of the sensor for complex urban environment. We collected point clouds in a complex urban environment to evaluate the proposed method. The performance of the proposed algorithm was evaluated using boundary recall and under-segmentation errors.

Two iris bandpass filters implemented by three-dimensional (3D) printing technology for millimetre-wave applications are demonstrated for the first time. The filters are designed at the E-band (60–90 GHz), and fabricated by selective laser melting using CuSn₁₅ alloy powder. A shifted passband and increased insertion loss are observed, which is caused by the fabrication tolerance of dimensional control and surface roughness. Methods to compensate the fabrication tolerance are proposed and the design procedures are provided. The presented results prove the great potential of 3D printing technology for millimetre wave applications.

A broadband low-cost waveguide window for millimetre-wave component sealing is proposed. The waveguide window includes two RT/Duroid5880 substrates and a quarter-wavelength waveguide. The back-to-back waveguide sealed windows are designed and tested. From 75 to 100 GHz, the return loss is higher than 15 dB, insertion loss is lower than 0.7 dB, and the leakage rate is <8 × 10⁻⁸ Pa. m³/s.

A new design method for a compact dual-mode dual-band filtering power divider is proposed. To achieve two transmission poles in both of the two passbands, the odd- and even-mode resonant properties of the dual-mode resonator are employed in the design. By symmetrically locating four dual-mode resonators at both sides of the main transmission line and choosing the proper output topology, the introduced circuit can successfully realise the dual-band power division and filtering selectivity property. Two resistors are utilised to achieve good in-band isolation performance of the filtering power divider. For demonstration, a dual-band filtering power divider with two passbands centred at 2.2 and 2.7 GHz was designed and measured. Simulated and measured results are provided which show a good agreement.

A full Ka-band right-angle transition from a substrate integrated waveguide (SIW) to an air-filled rectangular waveguide is proposed. A two-step ridged waveguide and the SIW with an etched slot are jointly designed to obtain a better electric field and impedance matching between the SIW and the air-filled rectangular waveguide. To verify the method, a back-to-back transition prototype at Ka-band is designed, fabricated and measured. The measured results show that the insertion loss of a single transition is <0.55 dB over the entire Ka-band from 26.5 to 40 GHz. Moreover, the 15 dB fractional bandwidth is increased from 25.7 to 40.9% compared with conventional right-angle SIW-to-waveguide transition. This broadband transition can be a good candidate for broadband millimetre-wave applications.

The high-power up to 4 W characteristic of a capacitive microwave power sensor with grounded MEMS beam is investigated. This device is fabricated by GaAs MMIC (microwave monolithic integrated circuit) technology. Experimental results indicate that the sensitivity of power sensor gradually degenerates with input power increasing continually. The measurement results are divided into three regions: pre-saturated, saturated and over-saturated regions. The corresponding sensitivities are 0.95, 0.76 and 0.56 fF/W at 10 GHz, respectively. This effect is caused by the device's capacitive mismatch at high-power, and the modified formula is calculated in sections.

The in-plane magnetic logic device is a spin-based technology which offers several advantages over charged-based devices such as non-volatility, ultra-low power and greater integration density. A novel low-power digital latch circuit is proposed by using various shaped nanomagnets. Specifically, a pipelined clocking layout is effectively constructed to ensure sequential and reliable operation. The simulation results show that the magnetic logic latch performs well. The proposed circuit is promising in building future ultra-low power magnetic memories, and may inspire new applications (i.e. magnetic arithmetic circuits).

A hybrid optical frequency division multiplexing (OFDM) system based on the electrical generation of the OFDM signal at the transmitter and on the all-optical demultiplexing of the OFDM subcarriers is experimentally demonstrated by exploiting a purposely designed arrayed waveguide grating (AWG) with 12.5 GHz frequency spacing. The AWG passively and all-optically processes a 3-subcarrier OFDM signal with fast Fourier transform functionalities, demultiplexing it into three 12.5 Gbit/s on–off keyed data at the corresponding output ports, which are then connected to the optical network users. Transmission over a 40 km feeder link is experimentally demonstrated. Taking into account the AWG's available 16 ports and four 3-subcarrier OFDM signal generators modulating independent wavelength carriers, a passive optical network (PON) architecture can be realised serving 12 optical network units with 150 Gbit/s total aggregate downstream capacity.

A two-phase driving approach for light-emitting diode (LED) power supply is proposed. The approach uses two rectangular current sources working complementarily to supply a constant current to the LED string so that the output current can contain very low ripple even without the use of any electrolytic capacitor in the driver circuit. A dual asymmetrical half-bridge converter with power factor correction is used to realise the approach. A 60 W prototype is built and tested to validate the idea.

Capacitive power transfer (CPT) based on electric field coupling has been proposed recently as an alternative technology for wireless power transfer, and a good understanding of the capacitive coupling is of great importance in the design and evaluation of CPT systems. A new term named capacitive coupling coefficient k_E is introduced to provide a quantitative measure of the coupling condition between the coupling plates. The term is derived by modelling the capacitive coupling plates based on electric charge balance, and its physical meaning is explained clearly in relation to the equivalent primary/secondary and mutual capacitances, which is also experimentally demonstrated by comparing two CPT systems with different cross-coupling configurations.

It is often challenging to supply high alternating currents at high frequency to inductive loads, because it demands very high voltages at the load terminals. Usually, in such a scenario, the use of large, heavy and expensive high-voltage/power active devices is mandatory. However, the set of requirements of an ongoing project, demanding portability, low cost and electrical efficiency, led to the necessity of working on that issue. An original method that enables the use of low-voltage active devices and a low-voltage source to supply high currents to inductive loads is described. The basic principle used was the reduction of the equivalent impedance seen by the active devices at the desired frequency, leading to lower terminal voltages. Further adaptations were made, including measures to improve power dissipation and protection from transients. The respective developed electronic circuit is shown and experimentally analysed.

By exploiting the sparsity and data structure of the received signals of airborne radar, the two-dimensional (2D) signal sparse representation (SR) model that is suitable for moving targets parameters estimation after clutter suppression is built. A novel 2D orthogonal matching pursuit (OMP) algorithm is also proposed to solve the 2D SR problem directly. The spatial parameters and temporal parameters of targets are first estimated separately based on two subdictionaries, i.e. space dictionary and time dictionary. The joint space–time parameter of each target is then obtained based on a very small space–time dictionary. The numerical results indicate that the proposed algorithm can achieve closely approximate parameters estimation performance with significant computational saving compared with the one-dimension (1D) method using traditional 1D OMP algorithm.

In the inverse synthetic aperture radar imaging, the autofocus is a required step for generating high-quality images. However, due to many factors, the aperture data may be sparse so that the classical motion compensation approaches and imaging algorithms are not proper. On the basis of the compressed sensing technique and two optimisation methods (the gradient projection method and the conjugate gradient method), a novel autofocus algorithm, which can be used in sparse aperture imaging, is proposed in this Letter. The phase errors induced by the translational Doppler frequency are estimated and the focused image is reconstructed simultaneously by dual iterative computation. This approach is verified by real data processing.

Preliminary results on the use of multistatic radar and micro-Doppler analysis to detect and discriminate between micro-drones hovering carrying different payloads are presented. Two suitable features related to the centroid of the micro-Doppler signature have been identified and used to perform classification, investigating also the added benefit of using information from a multistatic radar as opposed to a conventional monostatic system. Very good performance with accuracy above 90% has been demonstrated for the classification of hovering micro-drones.

This is a feasibility study for developing low-cost synthetic aperture radar (SAR) systems based on the IEEE 802.11ac protocol. The baseband module of IEEE 802.11ac is found to be similar to SAR, and its frequency coverage is wide enough to meet the requirement of high-resolution SAR imaging. By using the subbands merging technique, the spatial resolution can reach 0.5 m × 0.5 m.

Indoor positioning and life detection using radio frequency has been widely researched; however, to achieve both indoor positioning and life detection has been a very challenging task until now. By careful design of the waveform and a novel detection algorithm, asynchronous multiple frequency shift keying (A-MFSK) is proposed to solve this task for the first time, which can operate between an MFSK mode and a single tone continuous wave mode, providing a possibility of A-MFSK for this task. Detailed explanation about the detection algorithm is given. Simulations and measurements results of both modes demonstrate that A-MFSK has the capability of indoor positioning and life detection.

Design guidelines to suppress the work-function variation (WFV) effects of tunnelling field-effect transistors (TFETs) have been discussed in comparison with metal–oxide–semiconductor FETs for the first time. The effects of metal-gate materials and their grain size on the WFV have been investigated. The simulation results show that the selection of appropriate gate material and the reduction of metal grain size are the effective solutions to the WFV of TFETs.

A novel straightforward methodology for extracting bias-dependent small-signal equivalent circuit model parameters (SSECMPs) of silicon/silicon–germanium heterojunction bipolar transistors is presented. The inverse mapping between SSECMPs and scattering (S) parameters is established and fitted using simulated data of the SSECM. Since the problem has large input space, S-parameters at many frequency points, the least squares support vector machines concept is used as regression technique. Physical SSECMPs values are obtained using the proposed methodology. Moreover, an excellent agreement is noted between the S-parameters measurements and their simulated counterpart using the extracted SSECMPs in the frequency range from 40 MHz to 40 GHz at different bias conditions.

Ohmic contacts to an n-type GaN layer using an electron cyclotron resonance (ECR)-sputtered AlN (thickness of 3 nm)/Ti/Pt/Au electrode without an Al metal layer were investigated. Ohmic characteristics were achieved when annealed at a temperature of 400°C or more. Contact resistance reached a minimum (7.67 × 10⁻¹ Ω-mm) at an annealing temperature of 500°C.

Massive multiple-input multiple-output (MIMO) is becoming a key technology for future 5G wireless communications. Channel feedback for massive MIMO is challenging due to the substantially increased dimension of MIMO channel matrix. A compressive sensing (CS)-based differential channel feedback scheme to reduce the feedback overhead is proposed. Specifically, the temporal correlation of time-varying channels is exploited to generate the differential channel impulse response (CIR) between two CIRs in neighbouring time slots, which enjoys a much stronger sparsity than the original sparse CIRs. Thus, the base station can recover the differential CIR from the highly compressed differential CIR under the framework of CS theory. Simulations show that the proposed scheme reduces the feedback overhead by about 20% compared with the direct CS-based scheme.

In cellular systems, maintaining data rate at the cell edge has been a challenging task due to strong co-channel interference from neighbouring cells. Several techniques have been proposed to tackle the issue, among which soft frequency reuse (SFR) is the most widely used. A novel multi-layer SFR scheme combined with cell sectoring is proposed to improve the performance in cell-edge region. Then, a spectrum allocation scheme in a three-cell reuse system is designed to ensure the maximisation of the efficiency. A generic expression for power allocation in different regions along with the signal-to-noise ratio of multi-layer SFR in sectored cell is derived. Finally, system-level simulation has been carried out to demonstrate the efficiency of the proposed resource allocation scheme. It is shown that the spectral efficiency at cell-edge area improves by ∼10% which is significant for the cell-edge region.

In this Letter, the compressed sensing is introduced into multi-source and multi-relay cooperative system. The compressed process is executed by the linear combination in the air of the transmitted signal. The cooperative compressed sensing and amplify-and-forward (CCS-AF) scheme is investigated. It is firstly proved that CCS-AF transmission matrix can be regarded as the measurement matrix. The channel capacity is improved greatly by cooperative compression. The numerical results validate the effectiveness of the model and the scheme.

The performance analysis of a multi-user multi-cell massive multiple-input multiple-output system that applies a conventional channel estimation technique, namely the linear minimum mean square error over correlated Rician fading is investigated. Based on the analysis, it is found that increasing the line-of-sight component can enhance the estimation accuracy.

In the multi-tiered spectrum sharing systems, the exact closed-form expression of the outage probability is derived. It is assumed that the secondary users have different priority to access spectrum. A weighing factor is introduced to identify the intra-tier and inter-tier interference effects. It is observed that the analytical results are well matched with the simulated results.

The mean achievable rate of downlink in multicell networks, where coordinated beamforming is applied to mitigate inter-cell interference, is investigated. The upper and lower bounds for the mean achievable rate are derived by using Gamma distribution to characterise the probability distributions of the signal and interference power. A closed-form expression for the mean achievable rate is proposed to approximate the theoretical value. Analysis and simulation results show that the bounds are tight and the approximation is effective. The mean achievable rate increases with the number of transmit antennas while it first increases with the transmit power and then keeps a constant.