A circular polarised antenna array based on the recursive application of the sequential rotation architecture is presented. The first level sequential arrangement is applied to a set of four non-identical slightly detuned patches, resulting in a broadband improper array. At the second level, the sequential arrangement is applied to four identical first-level sub-arrays, regularising the structure. Experimental validations confirm a gain exceeding 10 dB from 5.35 to 7.25 GHz, with a maximum of 13 dB. Global bandwidth is 30% despite an area of only

A coupled-fed dual-patch antenna with vias, stubs and a metallic shield is proposed. The proposed design shows all the key features of multi-radiation nulls, low cross-polarisation, wide bandwidth, high and flat gain, while the reported single-patch and multi-patch antennas have part of the features. One prototype operated at 10.3 GHz has been fabricated and measured. The measured results show a 10-dB fractional bandwidth of 12.1%, the gain at the centre frequency is 8.7 dBi, and three radiation nulls appear at 7.6, 8.15 and 12.25 GHz, respectively. The cross-polarisation is less than −25 dB. The gain ripple is 0.36 dB.

A linearly polarised antenna with wide beam-width is proposed. This antenna is based on substrate integrated waveguide (SIW) cavity. The half-power beam-width is about 145° in the E-plane, and 140° in the H-plane. This proposed antenna has a low profile of 0.03λ ₀ (λ ₀ denotes to the space wavelength corresponding to the operating frequency centre) and a compact size of 0.31λ ₀ × 0.31λ ₀, which is very suitable for modern communication systems. The maximum gain is about 6 dBi, and the radiation efficiency is about 90% at the working frequency band. The cross polarisation is very small.

A three-dimensional printing technology that can be applied to stereo antennas fabrication is presented. The main steps of the fabrication include printing antenna model by dual materials fused deposition modelling and the following selective chemical plating. As a demonstration of this powerful technology, a typical stereo antenna, the Yagi-Uda antenna, is designed and fabricated. Measured results show the printed antenna has good performances and agree well with simulated results. The technology provides a simple, straightforward way for antenna fabrication, and is especially suitable for the fabrication of stereo structure antennas.

A compact multiband antenna is presented by using a metal–insulator–metal (MIM) ring resonator in its ground plane. Two arrays of corrugated MIM are served as ring resonator and surround the radiating patch. The localised surface plasmons of the resonator are excited by the patch to show multi-band operation of antenna. Design procedure of ring resonators and its impact on the impedance matching in multi-band operation is studied and the results are validated by experimental analysis of fabricated structure. The presented CPW-fed antenna operates at five bands, WLAN in 2.4-GHz (2.4–2.484 GHz), 5.2-GHz (5.15–5.35 GHz), C-Band in 6.5-GHz (6–7 GHz) and X-Band in 9-GHz (8.5–10 GHz), 9.8 GHz (9.7–9.9 GHz).

A compact broadband circularly polarised (CP) aperture antenna is proposed. In order to broaden the CP bandwidth, a pair of perturbation slots is introduced to generate a higher order mode (quasi-TE₃₁) for CP radiation. With three resonant modes working simultaneously a wider CP bandwidth is obtained. Besides, with some modifications to the ground plane, the antenna is miniaturised while keeping its wideband CP performance. The measured CP working bandwidth is 76.6% (2.9–6.5 GHz) with the antenna size of 43 mm × 43 mm, which means a 71% CP bandwidth increment and a 47% size reduction compared with the original CP aperture antenna.

A fully differential Gm-C lowpass filter for wireless and biomedical applications is introduced in this Letter. The proposed filter is based on a highly linear CMOS digital programmable operational transconductance amplifier (DPOTA).The filter consists of a parallel connection of three fourth-order Butterworth sections. Each section is optimised for a specific band of frequencies which can be tuned digitally. Switching between the different sections is achieved by controlling the corresponding DPOTAs' transconductance values, hence, this filter design eliminates the need for switches. Simulation results for a 90 nm CMOS technology are given. The third-order harmonic distortion (HD3) of the DPOTA remains below −60 dB up to 0.5 V differential input voltage at 1.2 V supply voltage. The proposed filter exhibits a wide cutoff frequency tuning range, from 100 Hz to 12 MHz, thus it covers many biomedical and wireless communication standards.

A dual-purpose probe applicable both to permittivity measurements and ablation of biological materials has been developed. For these purposes, a planar-type open-ended coaxial probe was used as an applicator due to its capabilities of broadband permittivity measurements and near-field ablation. In order to maintain highly efficient power transfer during ablation, an impedance matching network is designed. To verify the dual-purpose probe, the complex permittivity of several biological materials was measured, and a block of pork muscle was ablated. As a result, permittivity measurements were successfully achieved nearly up to 20 GHz, and the surface temperature of pork muscle was raised up to 70°C with only 31 dBm of incident power at 18 GHz.

This Letter proposes an operational-amplifier free with an embedded passive gain technique to implement an oversampling, noise shaping successive approximation register (SAR) ADCs. In the proposed scheme, the comparator noise, quantisation noise, settling errors and DAC thermal noise are alleviated. A third-order noise shaping SAR ADC with inserted passive gain design in 40 nm CMOS technology is well suited for low power application because of using passive elements like capacitors and switches. Due to the oversampling and shaping scheme, the structure can be used for high-speed and high-resolution operation.

An ultra-low-LO (local oscillator)-power X-band down-conversion ring mixer in 0.18-μm CMOS process is presented. By using the weak-inversion biasing technique, the proposed X-band ring mixer exhibits low-dc-power consumption and low-LO-drive power while maintaining a reasonable conversion gain (CG). The measurement results show that the proposed mixer demonstrates a maximum CG of 1.75 dB with ultra-low-LO-power of −8 dBm at RF of 12 GHz and IF of 100 MHz. The dc power is only 2 mW. The 3-dB RF bandwidth is from 9 to 15 GHz and the output 1-dB compression point (OP_{1 dB}) is −14 dBm.

This Letter presents a 0.35–1.5 GHz 5 × 5 switch matrix chip with a chessboard structure. In the proposed structure, by reassigning the position and switch mode of 25 passive switch grids which almost consume no DC power, the switch matrix can choose and transmit any eight of 16 input signals to the output ports on four directions at the same time. Throughput and the expansion ability of the switch matrix are markedly improved by flexibly choosing a signal path and reusing the switch grids. Besides, wideband gain compensation circuit modules and gain equalisers are used to compensate for insertion loss and gain flatness of the switch matrix. Fabricated by 0.18 μm SiGe BiCMOS technology, the measured highest insertion gain of a signal path is 10 dB. Meanwhile, insertion gains of all signal paths are higher than −6 dB, and isolations of all signal paths are better than 40 dB.

A novel ocular-features-combining method, called short-time Fourier transform (STFT) feature-combined image, and a simple convolutional neural networks (CNNs) model are proposed for arousal-valence recognition. The STFT feature-combined image aims to represent information on two ocular features (pupil size and eye movements) as a single image. The CNN model consists of two convolutional layers and uses STFT feature-combined image as an input. The experimental results demonstrate the effectiveness of the proposed method, and show that CNN model is not only effective for emotion-recognition methods based on other modalities, but also effective for ocular-feature-based emotion recognition.

Identifying moving objects is considered a difficult problem owing to camera motion, motion blur and appearance changes. To solve these problems, a moving object segmentation method based on a convolutional neural network is presented. The proposed network takes successive image pairs as input, and predicts the per-pixel motion status. This process consists of three streams: one that learns appearance features, another that learns motion features and a third that combines both features. Therefore, a joint model is learned for segmenting a moving object, because appearance and motion features complement each other. Experimental results, based on a challenging dataset, demonstrate that the proposed method has superior performance over state-of-the-art methods, with respect to intersection over union and F-measure scores.

Kernelised correlation filter (KCF) has demonstrated its superior performance in visual tracking. The strength of the approach stems from its ability to efficiently learn the object appearance variations over time. A fundamental drawback to KCF, however, is that the objective function is modelled as a ridge regression problem that is sensitive to outliers, thereby resulting in suboptimal performance when the target appearance during tracking suffers from severe variations due to illumination variation, partial occlusion, background clutter, and so on. To address this issue, the KCF as a least absolute deviations regression (LADR) that is robust to outliers is reformulated, and then an efficient and effective approach to solve it via the alternating direction method of multipliers (ADMM) is presented. The ADMM splits the LADR into a ridge regression problem as the conventional KCF and a soft-thresholding one, and hence the proposed approach is still extremely efficient as the conventional KCF. Evaluations are conducted on the CVPR2013 tracking benchmark dataset with 50 sequences, which demonstrate the superior performance of the proposed method over the state-of-the-art trackers.

The problem of simultaneously recovering multiple sparse signals bearing a common sparsity pattern is addressed. Specifically, a common Gaussian prior to all the sparse signals under consideration is assigned. This can make that the signals share the same sparsity pattern. Then, an expectation maximisation (EM)-based approach to learn the priori parameters from measurements, thereby leading to the recovery of sparse signals is adopted. Simulations verify that the proposed EM approach outperforms the state-of-the-art counterparts.

Dynamic random access memory (DRAM) is mainly used as the main memory in modern computers. Since data is stored in a memory cell that is composed of a capacitor and a transistor, the cell must be periodically refreshed to prevent data loss due to charge leakage. The refresh operation dissipates energy and degrades system performance. Existing DRAM devices determine the refresh interval based on the retention time of the weakest memory cell. However, most DRAM memory cells retain data much longer than the weakest cell. In this Letter, the authors propose a refresh method with early termination that stops the refresh operations early before the completion depending on the retention time. To minimise changes in the existing auto-refresh (AR) operation, the proposed early termination refresh (ETR) uses the same refresh granularity as AR, which is a row group, and marks different retention times for each row group in the memory array. While refreshing a row group in a DRAM device, ETR reads the retention time marked in the memory array and stops the refresh operation if the remaining refresh operations are redundant. ETR improves the average system throughput by 3.1% and reduces the refresh power by 65.4% over AR.

A novel low-complexity minimum amplitude difference (MAD) decoder is proposed for selected mapping (SLM)-based asymmetrically clipped optical orthogonal frequency division multiplexing (ACO-OFDM) visible light communication (VLC) system. With the proposed scheme, a specific set of symmetric vectors is designed to minimise the peak-to-average power ratio (PAPR) of signal without the transmission of side information (SI) and recover SI blindly by the proposed MAD decoder. Simulation results show that the proposed scheme reduces the PAPR effectively and the bit error rate performance of ACO-OFDM system with MAD decoder is very close to that of conventional selected mapping (CSLM) scheme with maximum likelihood decoder, but at much lower complexity.

Uniform constant composition (UCC) codes are introduced, which are p-ary constant composition codes with block length mp where each p-ary symbol appears exactly m times in each codeword, being m a positive integer and p a prime. UCC codes are derived from a new class of p-ary repeated-root cyclic codes and two constructions are presented. Both constructions are at least asymptotically optimal with increasing p when compared with known best bounds for constant composition codes.

Unlike laboratory calibration methods, filed calibration methods are not time consuming, costly and do not need laboratory equipment, so they can be used in any environment for calibration of low-cost MEMS accelerometers. The magnitude of gravity vector in static state is used as a reference in the calibration process. Then a cost function is defined which is non-linear and complex. So, in order to simplify this equation, a novel change of variables is proposed which converts this non-linear optimisation problem to a linear least square (LLS) method and a non-linear equation solving. After minimisation of this cost function using LLS method, bias, scale factor and non-orthogonality of the accelerometer are estimated and it is compared with two other field calibration methods. The results of simulations show good performance of proposed method. For online estimation of these coefficients, recursive least squares method is also utilised. Finally, simulations in MATLAB have shown that they converge to the true values.

The remote reading of high-resolution microfluidic and passive (i.e. batteryless and chipless) temperature sensors is focused. These sensors are remotely interrogated from a 24 GHz frequency-modulated continuous-wave radar performing a mechanical beam scanning for locating the sensors and measuring the variation of sensors electromagnetic echo level due to temperature fluctuation. From radar measurement data, an estimator is proposed here for determining the meniscus position of the fluid inside the sensors microchannel and for deriving the temperature at the sensors location. It is shown that the estimator presents a convenient linear dependence with the meniscus position at the sensor location. The smallest measurable variation of the meniscus position is of 40 µm.

A new method is presented for actuating liquid metals, based on the physical deformation of ferrofluid in response to an applied magnetic field. Using this ferrofluidic actuation, a liquid-metal slug was moved through a channel at an average velocity of 15.6 mm/s. The hydrocarbon-based ferrofluid exhibits negligible loss from 50 MHz to 20 GHz, and can thus serve as an alternative carrier fluid to hydrochloric acid or sodium hydroxide for liquid-metal-based reconfigurable radio-frequency circuits.

A simple formalism is presented as a basis to analyse planar microwave structures with uniaxial anisotropic materials having either electric or magnetic anisotropy or both. It involves a generalised relation of the field components of the multilayered structure, which can be represented by a full-wave hybrid matrix for each layer. Thus, for stratified structures, the system equation can be obtained by using a full-wave equivalent circuit. The application is demonstrated by analysing the well-known example of a two-layer waveguide filled with different uniaxial anisotropic dielectric material.

Data centre optical links are migrating to four-level pulse amplitude modulation (PAM-4) as a method to extend the data rate while covering longer distances. Vertical-cavity surface-emitting lasers (VCSELs) enable the integration of low-power transmitters, but their non-linear and bias-dependent behaviour makes conventional feed-forward equalisation less effective. This Letter presents a SiGe BiCMOS PAM-4 driver that boosts the falling-edge to the bottom level through a selective pre-emphasis technique. Experiments at 25 GBd (50 Gb/s) reveal that adding selective pre-emphasis to a 4-tap equalised current driving a 20.6 GHz VCSEL, relaxes the critical PAM-4 link budget requirements by >1 dB at the KP4 forward error correction threshold of . The potential of PAM-4 VCSEL transmitters can be significantly enhanced by including selective pre-emphasis to the equalisation topology while requiring minimal overhead.

It is a common practice in the LLC resonant converter to utilise the transformer leakage inductance as an inductive component in the resonant tank. Nonetheless, the leakage does not exist only on the primary side but also on the secondary side. This Letter proposes a winding orientation method to minimise the undesirable secondary leakage in the transformer. The basic theory of the proposed method relies on Dowell's model and Ampere's law to minimise the stored magnetic energy originated from the secondary windings. Along with the theoretical analysis, experimental tests have been conducted to evaluate the proposed method. The measurements of the leakage inductance are consistent with the expectations of the proposed winding orientation method.

Fully polarimetric synthetic aperture radar (PolSAR) data are represented by four channels and the coherences between two arbitrary channels are important descriptors for the interpretation of polarimetric scattering mechanisms. However, there exists a scattering ambiguity between oriented urban and natural areas since they both contribute to the cross-polarised (HV) scattering. A polarimetric correlation coefficient ratio is proposed to overcome this scattering ambiguity in PolSAR imagery. First, the polarimetric coherences of urban areas with various orientation angles were analysed. Subsequently, it was found that the proposed coherence parameter considers the reflection asymmetry of buildings and also the scattering divergence between co-polarised and cross-polarised channels, which is beneficial to the scattering analysis in urban areas. The effectiveness of the proposed parameter is demonstrated using the Phased Array type L-band Synthetic Aperture Radar dataset.

A novel cross-polarisation () estimation approach is proposed, which can be used to calculate the real part of co-polarisation cross-product value. The term is well known and widely used in full-polarimetric (full-pol) decomposition techniques. Its role in the hybrid-pol analysis is investigated. Using , a maximum-likelihood-based classifier is proposed. For performance evaluation, the classification results obtained using the proposed algorithm is compared with that of conventional and modified techniques. Pixel-wise comparisons of these three techniques are carried out over two different datasets, by considering full-pol as the standard basis.

To provide an optimised implementation aimed at calculating the chirp scaling (CS) coefficients used in state-of-the-art spaceborne synthetic aperture radar (SAR) imaging systems. Built on the core concept of breaking down the CS coefficient calculation into basic operations, we propose a new architecture that adopts a dual-operator engine as the basic processing unit and seeks to optimise the switching network of operator engines through an appropriately interconnected grouping of various calculations. A wide variety of SAR imaging architectures based on fast Fourier transformation-CS operations may benefit from this work. The proposed architecture is implemented in a Xilinx Virtex-7 FPGA process; a comparison between test results and results obtained from an off-the-shelf counterpart confirms the efficacy of the proposed architecture.

Wide-band interference (WBI) can severely degrade synthetic aperture radar image quality. This Letter proposes a new WBI suppression technique using time-varying filtering method and sparse recovery. In this method, a time-varying filter is firstly set up in the short-time Fourier transform domain as a pre-processing step to suppress the major power of WBI, and then, an adaptive dictionary-based sparse recovery algorithm is developed to recover the useful target echo loss resulting from time-varying filtering. Finally, traditional SAR imaging algorithms can be performed to obtain a well-focused image. Simulation results demonstrate the validity of the proposed method.

A 4H-SiC trench metal–oxide–semiconductor field-effect-transistor (MOSFET) design with an integrated merged PiN Schottky (MPS) diode is proposed. The Schottky contact is embedded on the bottom of the trench structure for the first time. The low electric field in the oxide and Schottky contact surface can be achieved simultaneously using the proposed integration design which enhances the oxide reliability and reduces leakage from the Schottky diode. The integration of the MPS diode reduces the total chip area and the required number of dies compared with the conventional method of using an external Schottky diode.

On the basis of Ag/In₂Te₅/W asymmetrical hetero-structures, the memristive samples were prepared by the magnetron sputtering method. The current–voltage (I–V) measurements show the bipolar resistive switching characteristics at the room temperature. The underlying mechanism can be well interpreted by the space–charge-limited conduction effect with redistribution and migration of charged defects responsible for the switching effect. The memristive possesses the properties of reversible switching, reproducible resistance, non-destructive readout, good cycling performance and non-volatile. It seems to be a promising candidate in the prospective non-volatile memory and neuromorphic circuit applications.

A simple scheme for compressing sparse representation of melodic music is outlined. The method is designed to store the output of sparse approximation (SA) of that class of signals. Sparsity is achieved using a trigonometric dictionary and a dedicated greedy strategy aiming at approximating the signal at the good point-wise quality. Comparisons to the popular MP3 standard illustrate the suitability of the scheme for storing, in a small file, SA of melodic music.

This Letter proposes a deep neural network (DNN) adaptation method, herein referred to as the hidden variability subspace (HVS) method, to achieve improved robustness under diverse acoustic environments arising due to differences in conditions, e.g. speaker, channel, duration and environmental noise. In the proposed approach, a set of condition-dependent parameters is estimated to adapt the hidden layer weights of the DNN in the HVS to reduce the condition mismatch. These condition-dependent parameters are then connected to various layers through a new set of adaptively trained weights. The authors evaluate the proposed hidden variability learning method on a language identification task and show that significant performance gains can be obtained by discriminatively estimating a set of adaptation parameters to compensate the mismatch in the trained model.

A compact CMOS linear transconductance (LiT) voltage-controlled oscillator (VCO) in 65 nm CMOS process is presented. The proposed LiT technique is realised using NP core without a choke inductor to reduce die area and avoid dual resonance problem. The measured output frequency of the proposed VCO shows 11.18–11.98 GHz and phase noise is −112.62 dBc/Hz at 1 MHz offset frequency. DC power consumption of the VCO core and the buffer is 5.86 and 6 mW, respectively. It achieves a high figure of merit normalised to the area of 198.6 dBc/Hz.

In this Letter, the authors consider device-to-device (D2D) communications over block fading channels. Both D2D user and cellular user (CU) have an outage probability constrain. The power is optimised for maximisation of the averaged energy efficiency (EE) of D2D communications under outage probability constraints and average transmit power constraint. Based on Dinkelbach algorithm and Lagrange dual method, an efficient power allocation algorithm is proposed to solve the above problem. Simulation results demonstrate the improvements in terms of EE by using the proposed power allocation scheme.

An effective and reliable indoor positioning is a highly needed service. A bi-iterative algorithm for mobile user localisation in an indoor space is presented based on the multipath measurements exploited by a single sensor. The bi-iterative algorithm calculates the locations of the mobile user and the so-called virtual sensors, which are mirror images of the physical sensors, alternatively. Notably, this algorithm does not require any a priori knowledge about the environment. Simulation results show that the location of virtual sensors can be accurately estimated after a couple of iterations, and in return, they enhance the accuracy of user localisation. The proposed algorithm can localise a user with sub-metre accuracy in most cases. Moreover, it even outperforms the positioning algorithms that require full information about the environment.