A novel structure for size reduction and bandwidth enhancement of quasi-Yagi antenna using spiral resonator (SR) metamaterials is presented. The basic resonance is produced through excitation of simple quasi-Yagi antenna elements through a microstrip feedline while parasitic SR metamaterials augment bandwidth. The antenna is designed on an glass-reinforced epoxy laminate sheets (FR4) substrate with a dielectric constant of 4.4 and a thickness of 1.6 mm. Compared to original printed quasi-Yagi antennas, the size of the proposed quasi-Yagi antenna is reduced by ∼53%. Simulation results show that the proposed antenna has the impedance characteristics with a frequency bandwidth of 1.43–3.97 GHz (94%) for return loss more than 10 dB and a gain of 3.4–5.2 dBi in the corresponding frequency range. The designed antenna presents an end-fire radiation with a front-to-back ratio >10 dB. The antenna is fabricated, and measurement results demonstrate compactness and wide bandwidth of the antenna.

The architecture of MASH 1-1-1 digital delta–sigma modulator for lengthening minimum sequence length is proposed. The first stage of the proposed multi-stage noise-shaping (MASH) delta–sigma modulator consists of two parts for the quantisation of input and the generation of long periodic feed-forward signal. The feed-forward signal results in extending the minimum sequence length invariantly to the input of the MASH 1-1-1 delta–sigma modulator. The noise power spectrum is analysed for preserving the noise-shaping capability of the MASH architecture.

This Letter proposes a new scheme to eliminate the bit-line leakage current of static random access memory. The proposed scheme utilises a four-input sense amplifier to amplify the voltages of self-compared bit-line pairs. The bit-lines of the proposed structure have no series capacitances and are directly connected to the sense amplifier input. By this way, read delay and error caused by the leakage current of bit-lines will be eliminated. Simulation results in SMIC 28 nm CMOS process design kits show that the proposed scheme has better stability and can decrease delay time by 41.1% at 0.9 V supply voltage compared with the X-Calibration technology.

A new edge-aware filter called the empirical Bayes filter (EBF) is presented. It is shown that the bilateral filter (BF), being a special case of the EBF, is an optimal filter in terms of Bayesian linear least square estimation. An adaptive EBF (AEBF), which is an adaptive combination of the BF output and the original image, is developed. Experimental results demonstrated that the AEBF outperforms the boosting algorithm in terms of improving the contrast of the bilateral filtered image.

Most of depth up-sampling algorithms are based on the consistent hypothesis, i.e. the object boundaries in the colour image are consistent with depth discontinuity regions in the depth map. However, the hypothesis is not always correct. Under the combined guidance of high-resolution (HR) depth edge map and HR colour image gradient map, a simple and efficient depth up-sampler is presented. Firstly, the consistent regions are distinguished from the other regions and more accurate depth edge points are found. Then, the initial up-sampled depth map from traditional bilinear interpolation is refined by an effective depth-assignment scheme. Extensive experiments demonstrate that the proposed method outperforms conventional interpolation algorithms and some other edge-based depth up-sampling methods.

Finding the median of a set of data within a window of finite size is computationally challenging on account of the complexity in sorting. Compared with the established nine-stage systolic arrays, an eight-stage systolic array to find the median of a fixed 3 × 3 window of n bit integers is proposed. The proposed array requires a fewer number of signal paths, and is faster for fixed resource. The method employed uses selective comparators for finding the median by avoiding comparators required to obtain fully sorted list. This reduces the partial sorting to eight-stage systolic array. However, this is applicable only to median sorting of 3 × 3 fixed window. The method employs combinatorial circuit implementation; consequently there is 12% gain in speed and 7% fewer signal paths. Circuit with memory cells at every stage and eight latency cycles results in 36% speed gain over the state-of-the-art non-sorting based methods. This method provides superior performance in comparison with the methods available for fixed 3 × 3 window-based median filters.

A fog level estimation method using intensity curves arranged with geometrical information is proposed. The curves, extracted from pixels in the road region and reflecting the tendency of intensity convergence under foggy conditions, are provided to the stacked auto-encoders and the encoded features are classified into four fog levels by a neural network. Experimental results with clear and foggy road images of various places show that the intensity curve feature of the proposed method is effectively working not only in detecting the presence of fog, but also in estimating the fog level accurately.

Vehicle detection in aerial images is of great interest in the field of remote sensing. Many methods such as the sliding-window-based detection have been successfully developed. A simple and effective mechanism to improve the existing methods is proposed. Vehicle in aerial images usually appears in arbitrary directions. Previous algorithms need to repeat the search at a pixel with all the possible orientations, which often bring the problem of increasing false alarms and computational complexity. To solve this problem, image local orientation is introduced into detection that provides a proper search direction for each pixel. Experimental results on a public database, unmanned aerial vehicle (UAV) and satellite images demonstrate the effectiveness and promising improvements in comparison with existing techniques.

The Epanechnikov kernel (EK) is a popular kernel function that has achieved promising results in many machine learning applications. Although the EK is widely used, its basic formulation requires fully observed input feature vectors. A method is proposed to estimate the EK when these input vectors are only partially observed, i.e. some of its features are missing. In the proposed method, named expected EK, the expected value of the kernel function is estimated given the distribution of the data and the observed values of the feature vectors.

A compact diplexer is implemented in Low-Temperature-Cofired-Ceramic (LTCC) technology and consists of six coupled substrate-integrated-waveguide (SIW) cavity resonators stacked in two layers. No transmission-line based junction is used. The couplings between the cavities are achieved through both SIW irises and slots placed in metal layers. The diplexer has two third-order filtering channels, centred at 2.7 and 3.3 GHz with 120 MHz bandwidths. The overall size of the diplexer is 27.74 mm (2.3λ_g at 3 GHz) × 10.4 mm (0.86λ_g at 3 GHz) × 0.84 mm, achieved by using an LTCC material of a high dielectric constant of 68. Simulations and measurements are in good agreement to demonstrate a compact diplexer based on an all-resonator structure using high dielectric constant LTCC material.

A novel bandpass filter (BPF) design based on vertical split-ring resonators (VSRRs) was developed for single- and dual-band applications. The filter is composed of VSRRs, transmission lines, and apertures. The characteristics of single- and dual-band BPFs using a single VSRR and dual VSRRs, respectively, were investigated. The bandpass characteristics arising from VSSR resonance can be controlled by the VSRR dimensions, and the independent bandpass characteristics of dual VSRRs can be used to implement a dual-band BPF. A full-wave simulation and experimental measurements were used to measure their performance. The simulated results for the single- and dual-band BPFs were in good agreement with the experimental results.

A design of broadband power amplifier (PA) which uses harmonic-optimised matching network (MN) is designed to maintain high efficiency. The load–pull data is used to construct the optimal impedance areas in fundamental and harmonic parts. Then, the modified simplified real frequency technique algorithm is employed to design output-MN through constructing the defined harmonic-error functions. A 10 W Cree gallium nitride high-electron-mobility transistor device CGH40010F is used to validate this method. The proposed PA has a 40% bandwidth (1.8–2.7 GHz) and a 64–81% drain efficiency. The digital pre-distortion process shows the adjacent channel leakage ratio (ACLR) is <−52 dBc at 2.25 GHz.

A microstrip lowpass filter using stepped impedance resonator hexangular unit is presented. The proposed lowpass filter (LPF) has some appropriate features such as compact size, low insertion loss and wide stopband. The LPF has cut-off frequency at 2.8 GHz and stopband bandwidth from 3.15 up to 25.5 GHz with attenuation level better than −20 dB. Also, it has in-band insertion loss <0.1 dB and return loss better than 16.5 dB. Simulated and measured results are presented and relatively good agreement between them has been obtained.

The modelling of the effective dielectric constant of a planar spoof surface plasmon polariton waveguide for X-band frequencies is presented. The waveguide has a single conductor structure that is corrugated on both sides. A methodology to extract the effective dielectric constant of waveguides with complex patterns and a novel closed-form formula based on complex analysis of the structure and empirical methods are suggested. The suggested formula is a function of the corrugation depth, aperture, periodicity, thickness of the substrate material and permittivity. The worst case error between the formula and measurement result is 8.4%, which is much lower than the previously reported coplanar stripline formulation approach having an error of 14.5%.

With linear digital pre-distortion (DPD) and 8-bit digital to analogue converter (DAC), a single channel 224 Gbit/s (56-GBaud) 16-level pulse amplitude modulation (PAM-16) signal is experimentally transmitted over a 100 m standard single-mode fibre (SSMF) for the first time using intensity modulation and direct detection (IM/DD). The 3 dB bandwidth of the whole system is around 22 GHz, which is far below the bandwidth of the 56-GBuad PAM-16 signal. The strong inter-symbol interference caused by the limited system bandwidth is pre-compensated by the proposed linear DPD technique. The experimental results indicate that the linear DPD process can effectively avoid the noise enhancement by the aggressive feed-forward equalisation at the receiver, and also improves the system performance at the cost of additional finite impulse response filter at the transmitter.

An asymmetrical hybrid-controlled half-bridge LCC resonant converter which integrated a buck–boost converter and a half-bridge LCC resonant converter is proposed. It benefits with wide soft switching range, low conduction loss and high power density. By utilising an asymmetrical hybrid control strategy, its switching frequency and duty ratio can be adjusted simultaneously. The proposed LCC resonant converter maintains output voltage regulation and zero-voltage switching of switches in wide input voltage and load variation range. Experiment results of a 500 W prototype are provided to verify the theoretical analysis results.

Inverse synthetic aperture ladar (ISAL) is analogous to the inverse synthetic aperture radar but works at frequency 10^4–5 times higher. A method is proposed to process the ISAL data with stepped-frequency continuous waveform (SFCW). Due to the short wavelength used for ISAL and the relatively long transmission of the SFCW, the motion during the transmission and the relative range shift between adjacent sub-band chirps must be both taken into account while performing the bandwidth synthesis and imaging. An analytic signal model was derived to address this problem. In the proposed model, three additional terms, named the bulk range walk term, the stepped phase error term and the additional range shift, were formulated in ISAL imaging with SFCW for the first time. Based on the signal model, an effective method was proposed to coherently synthesise all the sub-band echoes and then focus the ISAL image. Experimental result was shown and the focused image of an airplane model demonstrated the effectiveness of the proposed method.

A hybrid weighted Fourier transform and relaxation (hybrid-WRELAX) method applied to Loran-C skywave delay estimation is presented. The performance of this method is demonstrated and compared with the spectrum analysis method. The hybrid-WRELAX method has been proved to provide higher accuracy to estimate the Loran-C skywave delay. Results testify this conclusion using off-air data.

Recent studies allow mainlobe interference suppression in MIMO radar systems by weighting the random phase codes at transmitter. However, the performance of interference suppression is not stable when the phase codes are generated randomly, especially in the case of the small number of the elements or a large number of interferences. A transmit phase codes optimisation method is proposed. The modified transmit steering vector is constructed by combining the transmit phase codes and the steering vector of the expected signal. The problem can be solved by minimising the projection of the modified transmit steering vector onto the interference subspace. Simulations verify the effectiveness of this method.

A novel single channel blind source separation method based on probabilistic matrix factorisation (PMF) is proposed. Compared to the conventional non-negative matrix factorisation (NMF) employing Euclidean distance or Kullback–Leibler divergence, PMF uses the log posterior probability as a cost function for optimising spectrum and activation matrices. Such cost function has an advantage that the hyperparameters are optimised numerically without cross-validation. In order to apply PMF to audio source separation, both Gaussian and Laplacian priors are considered. Exponential substitution for target matrices is also proposed to guarantee the non-negativity of the separated spectrogram. In source separation experiments, the proposed PMF-based approach provided significantly better performance than the conventional NMF.

The perceptual orthogonal matching pursuit (POMP), a sparse approximation algorithm built upon the known orthogonal matching pursuit (OMP), is introduced. It is designed for speech processing and can be of great use in speech coding applications. It can handle all types of real dictionaries, including predefined and adaptive dictionaries. Being a suboptimal method, POMP performs a series of local updates where it minimises a perceptual distortion measure involving a perceptual weighting filter. This filter is tailored for speech signals and is used in AMR 3GPP coders. Experiments show that POMP outperforms the standard OMP for predefined and adaptive dictionaries.

A new inter-carrier interference self-cancellation method with the data symbol mapping scheme of differential grouping weighted symmetry data-conjugate is studied and proposed to raise the bandwidth efficiency and further improve the system performance over fast time-varying fading channels. Comparing with the other existing self-cancellation methods, the proposed scheme can not only maintain the same bandwidth efficiency as the original orthogonal frequency division multiplexing system, but also show a better performance on carrier-to-interference ratio and bit error rate according to the final simulation results and performance analysis.

The authors formulate a blind equalisation problem minimising the residual that is difference between the received signal and the predicted signal. Since both channel impulse responses and transmitted symbols are unknown, the authors regard the problem as a kind of dictionary learning problem. The authors divide the problem into two sub-problems and iteratively find the channel impulse response and the demodulated symbols. Since the wireless channels with a large bandwidth tend to have a sparse multipath structure, the authors apply the compressive sensing technique to the channel estimation sub-problem. Numerical results show that the proposed algorithm achieves the Genie-aided lower-bound performance.

A wireless-powered heterogeneous sensor network is considered whose sensor nodes (SNs) harvest energy from a radio signal emitted from a base node (BN) communicating with user nodes and then transmit the collected information to a data collection node. In order to maximise the throughput of the sensor network under the interference limit on the BNs, an algorithm that optimises the duration of the phases and the transmit power of the SNs is proposed. By comparing to a method with a fixed time ratio for energy harvesting, the benefit of the proposed method is verified.

Parallel cyclic redundancy check (CRC) architecture for high-throughput forward error correction decoders in broadband communication systems is proposed. Large amount of data bits are needed to be transmitted in a unit of a transport block (TB) in broadband communication systems. Owing to implementation complexity, TB is segmented into multiple small units of code blocks (CBs). The parallel CRC architecture proposed recursively calculates the TB CRC using individual CB CRCs. The proposed parallel CRC architecture is used to balance optimally between memory requirement and computational complexity.