Broadband circularly polarised square slot antenna excited by a coplanar waveguide feed with enhanced axial ratio bandwidth (ARBW) is proposed, designed and experimentally studied. Larger than 21% 3 dB ARBW can be attained by using asymmetric feed and implementing a T-shaped grounded stub from the left side of the square slot in orthogonal direction towards the slot centre. To further enhance the 3 dB ARBW of the proposed slot antenna, a pair of equal grounded L-shaped strips with different sizes is embedded at the top right corner of the square slot. Small L-shaped grounded strip plays an important role for merging two closely spaced multi-resonant modes, generated by the combined effect of asymmetric feed with T-shaped grounded stub and with large L-shaped strip. Overall size of the proposed antenna is 40 × 40 × 1.6 mm³. Measured value shows that the impedance bandwidth and 3 dB ARBW of the designed antenna are 73.39% (5.02–10.84 GHz) and 58.08% (5.07–9.22 GHz), respectively. Good agreement is achieved between simulated and measured results.

An UWB circularly polarised (CP) slot antenna with simple structure is presented in this Letter. By etching a simple C-shaped slot on the planar ground, adopting an L-shaped strip as a radiator, and employing an off-centre-fed structure, the proposed CP antenna can easily be realised with both wideband impedance bandwidth (IBW) and 3 dB axial-ratio bandwidth (ARBW). The impedance and ARBWs of this antenna can be further expanded by adding a matching stub and cutting an L-shaped slit on the lower ground. This antenna can realise a wideband IBW (S ₁₁ < −10 dB) of about 3.62 GHz (124.4%, 1.10–4.72 GHz) and 3 dB ARBW of about 3.6 GHz (115.2%, 1.26–4.68 GHz).

A compact, planar, low profile microstrip line-fed quad-band antenna is presented with operating frequencies at 2.5/3.6/5.5/7.5 GHz. The antenna consists of a rectangular split-ring resonator (SRR), a stepped impedance resonator (SIR) inside the ring, a slot on the SIR and a pair of SRRs either side of the matching network. Each of the resonators generates its own individual band which is independently tunable. The antenna is compact in size having dimensions 0.10λ ₀ × 0.13λ ₀. The radiation patterns are omnidirectional and bilateral in the H-plane and the E-plane, respectively, at all the resonance frequencies. The simulated results are observed and reported in terms of S-parameters, gain and radiation patterns. A prototype structure is fabricated and the measured results are compared with those obtained from the simulation.

A method to reduce the mutual coupling in wide-band multilayer patch array operating in C band is presented. The proposed device use conveniently sized meander line parasites printed on the same substrate of the upper patch. Measurements on a prototype shows a measured bandwidth of about 19.6% centred at 5.1 GHz, therefore adequate to cover the whole WLAN frequency range. The meander lines allow to reduce the patch mutual coupling by about 2.4 dB.

Since a conceptor, achieving direction-selective damping of high-dimensional network signals, usually takes the form of a projection matrix and is deduced analytically, a conceptor-based neural network is thought to be untrainable with backpropagation and gradient-descent algorithms from end to end. It limits the application of conceptors. To address this issue, an algorithm is proposed to train conceptor-based neural networks from end to end with gradient-descent algorithms. To the best of the authors’ knowledge, it is the first work of such an end-to-end training algorithm. To develop this algorithm, a softmax-like loss function involved with conceptors is constructed empirically. Based on this loss function, corresponding gradients are deduced by using backpropagation method so that it is possible to train conceptor neural networks from end to end with a gradient-descent algorithm. Several experiments are conducted to show the feasibility and effectiveness of the proposed training algorithm.

A medical image registration method is proposed. An enhanced mutual information is employed as the similarity measure. A hybrid optimisation technique based on Powell's method and cuckoo search is developed as the optimiser. Experimental results show the effectiveness of the proposed method.

Maximum likelihood reconstruction of activity and attenuation (MLAA) from emission data only suffered from the inherent cross-talk between the estimated attenuation and activity distributions. The authors proposed an improved MLAA algorithm by utilising tissue prior atlas (TPA) and a Gibbs prior as prior knowledge. TPA determines the plausible region for each of the typical attenuation coefficients; hence, it imposes statistical condition as a supplement for the exclusive magnetic resonance (MR) information on the reconstruction process of attenuation map. Therefore, along with the soft tissue distribution provided by the segmentation of MR images, an air mask and a bone probability map breakdown the MR low-signal class into four subclasses in order to favour recognition of air and bone. Estimations on attenuation coefficients are realised as a mixture of pseudo-Gaussian distributions. The proposed algorithm is evaluated using the simulated 3D emission data. The proposed MLAA-TPA algorithm is compared with the MR-MLAA algorithm proposed by Heußer et al. Their results demonstrate that the MR-MLAA algorithm performance depends heavily on the MR segmentation accuracy well handled by MLAA-TPA. The quantification results illustrated that the MLAA-TPA outperformed the MR-MLAA algorithm owing to reduction of misclassification and more precise tissue detection.

A class-AB OTA (operational transconductance amplifier) topology with rail-to-rail input common-mode range is proposed for application in very low-voltage applications. High efficiency is achieved by reusing transistors both for class-AB operation and for mirroring the output currents, and a threshold lowering technique is applied to allow supply voltages less than two threshold voltages. Simulations in 40 nm CMOS technology show 41 dB gain at ±0.3 V supply voltage, a unity-gain frequency of 8.8 MHz on a 5 pF load, class-AB behaviour and full rail-to-rail operation when closed in unity-gain buffer configuration.

Many studies on 3D-stacked dynamic RAMs (DRAMs) have been conducted to overcome the shortcomings of conventional DRAM. The hybrid memory cube (HMC) is one of the most promising 3D-stacked DRAMs, thanks to its high bandwidth and expandable structure. However, a high-speed serial link that interfaces the CPU and HMC consumes significant power, primarily because of the high overhead incurred in synchronising its clock. Although the link provides low-power modes, managing them is very difficult because of their long mode transition times. An autonomous power management method for the high-speed link is proposed. The proposed method determines the optimal number of active links while satisfying the required link performance. Simulations demonstrate that the proposed method reduces link power consumption by an average of 63.06% with a performance degradation of only 1.36%. Therefore, this proposed autonomous link power management is an outstanding option for low-power HMC-based systems.

Area overhead reduction in conventional triple modular redundancy (TMR) by using approximate modules has been proposed in the literature. However, the vulnerability of approximate TMR (ATMR) in the case of a critical input, where faults can lead to errors at the output, is yet to be studied. Here, identifying critical input space through automatic test pattern generation and making it unavailable for the technique of approximating modules of TMR (ATMR) were focused, which involves a prime implicant reduction expansion. The results indicate that the proposed method provides 75–98% fault coverage, which amounts up to 43.8% improvement over that achieved previously. The input vulnerability-aware approach enables a drastic reduction in search space, ranging from 41.5 to 95.5%, for the selection of candidate ATMR modules and no compromise on the area overhead reduction is noticed.

A duobinary transmitter (TX) is presented in a single-ended topology using voltage-mode drivers to support dynamic random access memory (DRAM) interface. A four-phase parallel duobinary precoder is included. It relaxes one of the critical timing requirements of the duobinary TX by reducing the feedback step of the precoder and performing its feedback at once. Fabricated in a 55 nm CMOS process, the TX occupies 0.053 mm² active area. The TX achieves 10 Gbps operation at 6.8 pJ/b of energy efficiency and operates up to 12.8 Gbps at 7.6 pJ/b.

A new wide-input dynamic range flip-flop capable of operation at an ultra-low supply voltage of 0.16 V is presented. The proposed flip-flop named as capacitively boosted sense-amplifier flip-flop (CB-SAFF) utilises a capacitively boosted sense-amplifier master stage to sense the data signals and amplify them to a voltage higher than the supply and below the ground for driving the slave latch stage with improved strength. Using the same size of input/output transistors and load capacitance, the proposed CB-SAFF outperforms existing state-of-the-art sense-amplifier flip-flop designs at a low supply voltage operation from 0.16 to 0.6 V in terms of power delay product and clock to output propagation delay performance metrics. In addition, the proposed CB-SAFF can also sample low-swing data signals down to 0.2 V even at a 0.16 V supply voltage and 1 MHz clock frequency, thus making it highly suitable for applications that demand high speed and low power consumption such as for use in ultra-low voltage Internet of Things, wireless sensor nodes and smart motes.

A masked beamforming algorithm for a hybrid acoustic vector sensor array (AVSA) is presented. In the general literature, a full-rank AVSA, comprised entirely of an acoustic vector sensor (AVS), is known to be capable of left–right ambiguity elimination. However, a full-rank AVSA has disadvantages including rotation perturbation of sensor directivity, complexity of electrical loading, and high cost. To alleviate these disadvantages, a hybrid AVSA consisting of only a single AVS in an array of omni-directional sensors is reported in the patent with a limited performance in left–right ambiguity elimination. A masked beamforming algorithm is proposed to achieve good left–right ambiguity elimination performance in a hybrid AVSA by masking the beam output spectrum of the omni-directional sensor array with the beam output spectrum of an AVS in the frequency domain. Simulation results that validate the performance of the proposed method are also presented.

Quadrature spatial modulation (QSM) is one of the recently emerging transmission schemes to improve the throughput of the multi-input multi-output systems. QSM transmits an M-ary complex symbol whose real and imaginary parts activate an antenna index independently thus provides an extra spatial dimension compared to conventional spatial modulation (SM). A generalised QSM (GQSM) transmission is considered in which a set of M-ary complex symbols activate multiple antennas to transmit their real and imaginary parts separately, which offers higher throughput in terms of bits per channel use (bpcu) than other SM techniques. A detector is proposed, ordering-based structured orthogonal matching pursuit for GQSM using compressive sensing (CS), which performs very close to the maximum likelihood detector with significantly lesser complexity. Also, the proposed algorithm performs superior to other CS-based detectors and offers a better trade-off between complexity and performance.

A low-power G_m-C filter with the elliptic prototype targeting wireless application of the IEEE 802.15.4 (ZigBee) standard is presented. A modified inverter-based Gm cell is proposed to increase the current efficiency. Due to the tail current source, this Gm cell also shows better common-mode rejection and power supply rejection performance than traditional operational transconductance amplifier (OTA) structure. The filter is implemented in a 65 nm CMOS process. It achieves a figure of merit of 0.01 fJ with a power consumption of 0.18 mW/pole from a 1.2 V supply voltage. It provides stopband attenuation better than 40 dB, and an in-band IIP₃ of 9 dBm. An automatic frequency tuning circuit based on sine-wave PLL method is introduced to compensate for the process variations. The centre frequency and bandwidth can be simultaneously tuned to satisfy the specifications. They are also stable over the process variations with only 2.3% deviation.

Consolidation of flame hydrolysis deposition silica soot with a 9.3 µm CO₂ laser has been demonstrated. A range of laser parameters were investigated and the surface roughness of the resulting silica layers were characterised with a stylus profiler and white light interferometer. The surface roughness parameters were Ra = 68.9 nm, Rq = 83.8 nm perpendicular to the trajectory of the translated laser beam for a speed of 300 mm s⁻¹ and an average laser power of 42.5 W, and Ra = 29.5 nm, Rq = 36.18 nm along the trajectory of the translated laser beam for a speed of 250 mm s⁻¹ and an average laser power of 35.8 W.

The impact of the stress in room temperature inductively coupled plasma chemical vapour deposited (ICP-CVD) SiN _x surface passivation layers on off-state drain (I _DS-off) and gate leakage currents (I _GS) in AlGaN/GaN high electron mobility transistors (HEMTs) is reported. I _DS-off and I _GS in 2 μm gate length devices were reduced by up to four orders of magnitude to ∼10 pA/mm using a compressively stressed bilayer SiN _x passivation scheme. In addition, I _on/I _off of ∼10¹¹ and subthreshold slope of 68 mV/dec were obtained using this strain engineered surface passivation approach.

The direction of arrival (DOA) estimation problem using co-prime linear arrays is studied. By analysing the special array geometry of the co-prime array, the co-prime array is taken as a filled uniform linear array where some elements are omitted, then a modified root-multiple signal classification (MUSIC) algorithm is developed, which avoids the matching process by obtaining the true DOAs without phase ambiguity. In addition, it can detect more sources by making full use of the degrees of freedom provided by the co-prime array. Simulation results are provided to verify the effectiveness of the proposed algorithm.

Network echo path impulse response is single-block-sparse in nature. In order to obtain a single-block-sparse estimate of the unknown echo path, a new least mean squares (LMS) algorithm is proposed by introducing the penalty of single block sparsity, which is the difference between the mixed norm and norm of the uniformly partitioned filter tap-weight vector, into the original mean-square-error cost function. This is motivated by the fact that the difference between the mixed norm and norm of a vector is minimised only when there is at most one non-zero block in the vector. Numerical simulation results show that the proposed algorithm can effectively estimate and track the unknown echo path, outperforming existing block-sparsity-induced LMS algorithms.

The problem of recovering a sparse signal buried in noise from a linear observing system has been studied, via utilising statistic prior information of noise and signal, a fast matching pursuit revised maximum a posterior (MP-RMAP) estimation method is proposed. The proposed method overcomes the none-robust estimation problem that fast Bayesian matching pursuit has in high signal-to-noise ratio cases. Compared with other methods, the MP-RMAP method is able to improve the estimation accuracy with low complexity. Experimental results verify the validity of the proposed algorithm.

A highly linear and efficient CMOS power amplifier (PA) with adaptive auxiliary amplifier control (AAAC) is presented, which makes the common-gate transistor of an auxiliary amplifier operate in the saturation region for overall output powers. This leads to decrease the AM–PM distortion by reducing the variation of the output susceptance. In addition, the AAAC reduces the current consumption for all power ranges by controlling the auxiliary amplifier. The PA is fully integrated with all matching networks in a 0.18 μm CMOS process. It was measured with an 802.11n 64-QAM MCS7 signal. It achieved a maximum average power of 19.9 dBm with a power-added efficiency of 28% under an error-vector magnitude of −25 dB.

A novel method of cross-device tracking based on user typing behaviours is presented. Compared with existing methods, typing behaviours can offer greater security and efficiency. When people type on their devices, a number of different factors may be considered to identify users, such as the angle and distance of contact point to the centre of the target character, the time elapsed between two typing actions and the physical force exerted on the device (which can be measured by an accelerometer). An experiment was conducted to validate the proposed model; those data are collected through an Android App developed for the purpose of this study. By collecting a reasonable amount of this type of data, it is shown that machine learning algorithms can be employed to first classify different users and subsequently authenticate users across devices.

Due to the non-linear behaviour of the power amplifier (PA), the amplification of signals with fluctuating envelopes leads to distortion inevitably. These non-linear effects can be counteracted by the digital pre-distortion (DPD) with the adaption and updating of lookup table (LUT). In this Letter, a low-complexity LUT implemented by FPGA of pre-distortion PA lineariser is proposed to obtain more accurate linearisation. The algorithm utilises interpolation of the LUT with the method of Taylor series. The experiment shows that this method can be used to obtain the more accurate indexed value of LUT to estimate the PA behaviour for effective DPD.