The theory of time-modulated circular arrays in respect of generating orbital angular momentum (OAM) beams at harmonic frequencies is analysed. Without using expensive phase shifters in phased arrays, beam steering for OAM beams is achieved using switches connected to array elements. The model of an eight-element time-controlled circular array is derived with the method of time-modulation beam steering techniques. Simulation results show that beam steering for OAM beams is realised, which indicates the effectiveness of the proposed method.

A fully-voltage-controlled oscillator (VCO)-based continuous-time (CT) Delta-Sigma (ΔΣ) analogue-to-digital converter (ADC) is reported, implementing second-order noise shaping without any analogue integrators. Traditional power-hungry front-end analogue integrator is replaced by a highly-digital power-efficient VCO-based integrator, which is constructed by a VCO, a phase detector and a charge pump. The quantisation is executed by a VCO-based quantiser with intrinsic noise shaping. Taking advantage of the mostly-digital and high-order structure, a spurious-free dynamic range of 74 dB and a figure-of-merit of 52 fJ/step over a 40 MHz bandwidth are achieved by a 0-2 multi-stage shaping (MASH) demonstration in 40 nm CMOS.

A hardware-efficient slope-error (SE) algorithm based four-level pulse amplitude modulation (PAM4) baud rate clock and data recovery (CDR) scheme is proposed. The algorithm uses three adjacent data information to obtain slope information, thus reduces the required error samplers by 75% compared to the widely used baud rate CDR, namely, Mueller Müller (MM) CDR when working at same phase detector (PD) gain. The power efficiency of the CDR loop is improved by 36% compared to MM CDR. The proposed PAM4 baud rate CDR does not bring in extra block except for PD, which makes it easy to be extended from adaptive decision feedback equalisation. A 40 Gb/s PAM4 receiver with the proposed CDR is designed in 55 nm CMOS process. The simulated jitter tolerance of the CDR at high frequency exceeds the SONET OC-768 JTOL mask by at least 0.35 UI at the bit error rate of 10⁻¹². The CDR loop consumes 106 mW from a 1.2 V supply and occupies an active area of 0.1 mm².

The authors present a spike-triggered adaptive neuron circuit with input current modulation. Unlike adaptive neuron circuits where adaptation is realised by leakage modulation, the circuit presented in this Letter modulates the input current to membrane capacitor. Therefore, it is possible to reduce extra power consumption originating from increased leakage. Threshold voltage modulation of silicon on insulator (SOI) MOSFET by back gate effect is used to change the amount of injected current for the same input voltage. Through this method, the circuit in this work consumed 25.9% less power than the one modulating leakage.

A novel 3D dynamic barcode that can easily and effectively be captured, and decoded utilising inexpensive and mobile camera devices is presented. The primary expectation of the authors’ approach is that users will have the ability to transfer large packets of information without the necessity for customary electromagnetic techniques such as Bluetooth or Wi-Fi. Designing an algorithm that successfully extracts the frames from the recorded dynamic barcode enables the end user to video capture the dynamic barcode, rather than taking multiple snapshots of each barcode frame. The results indicate that the optimum setting for the capturing device is 720p at 30 frames per second with an efficiency of 99% and transmission rate of 622 bytes/s.

Iris centre is widely used in feature-based gaze estimation system. However, the performance of various existing iris centre localisation methods is degraded in low-resolution images. To address the problem, an accurate regression-based gaze estimation system is proposed by replacing the iris centre with a novel average-binary-connected-component-centroid (ABCCC) feature. First, ABCCC is obtained by averaging a series of binary connected component centroids, which are calculated by different percentile grey thresholds in the normalised eye region of interest. Then, head pose is estimated by employing the OpenCV iterative algorithm. Thereafter, ABCCC and head pose are mapped to compute the gaze using a linear mapping functions, which are regressed in calibration phase. Compared with traditional methods using iris centre, ABCCC is easier to calculate and shows a stronger correlation with the change of gaze, which improves the accuracy of the gaze estimation system. Experimental results on EYEDIAP database verify the effectiveness of the proposed method.

A new algorithm based on learning vector quantisation classifier is presented based on a modified proximity-measure, which enforces a predetermined correct classification level in training while using sliding-mode approach for stable variation in weight updates towards convergence. The proposed algorithm and some well-known counterparts are implemented by using Python libraries and compared in a task of text classification for document categorisation. Results reveal that the new classifier is a successful contender to those algorithms in terms of testing and training performances.

A simple yet robust reduced-reference quality metric based on local sharpness measure for blurred images in discrete cosine transform (DCT) domain is introduced. As a single feature to represent the quantification of blur in an image, a global image sharpness is quantified from the local sharpness with a selected optimal subset of DCT coefficients in each overlapped block in the feature extraction process. Then, the final objective quality score is simply calculated by division by the reference value in the quality analysis process. The experimental results on three public quality assessment databases demonstrate the proposed method correlates highly with human subjective judgements and outperform other methods consistently in terms of prediction accuracy and monotonicity for a wide range of blurriness.

A novel residual-error prediction method based on deep learning with application in lossless image compression is introduced. The proposed method employs machine learning tools to minimise the residual error of the employed prediction tools. Experimental results demonstrate average bitrate savings of 32% over the state-of-the-art in lossless image compression. To the best of the authors’ knowledge, this Letter is the first to propose a deep-learning based method for residual-error prediction.

Sparse signal representation showed promising results in the field of face recognition in the past few years. An algorithm based on a sparsifying transform is considered. It mainly learns a dictionary that can transform the image into sparse vectors. In the transformation domain, the images of the same class should have similar non-zero coefficients pattern that can be used for identification. The classification process of this method only requires to transform the image and make norm comparisons to determine the class of the image. The proposed method shows a comparable performance with the other known methods in the literature by means of accuracy. A novel method in sparsity-based image identification that uses analysis dictionaries is proposed, unlike the conventional sparsity-based methods. One advantage of the proposed algorithm is the low computational cost of the classification process.

For the path loss prediction in mountainous areas, a method is proposed to adjust the Lee model with diffraction methods using a variable step-size least mean square algorithm. Measurements were conducted in mountain areas to compare the prediction performances. The prediction performances were improved by up to 2.76 dB in the average error and 0.96 dB in the standard deviation of errors by the proposed method when compared to non-tuned Lee and Joint Radio Company (JRC) models with diffraction methods.

Since irregular low-density parity-check (LDPC) codes are known to perform better than regular ones, and to exhibit, like them, the so-called ‘threshold phenomenon’, this Letter investigates a low-complexity upper bound on belief-propagation decoding thresholds for this class of codes on memoryless binary input additive white Gaussian noise channels, with sum-product decoding. A simplified analysis of the belief-propagation decoding algorithm is used, i.e. consider a Gaussian approximation for message densities under density evolution, and a simple algorithmic method, defined recently, to estimate the decoding thresholds for regular and irregular LDPC codes.

A switched delay line phase shifter implemented in a 90 nm SiGe BiCMOS process utilising PIN diodes is presented. The 4-bit phase shifter utilises four SP4T switches for a simplified architecture. The frequency of operation is from 75 to 100 GHz, and the simulated input referred P1dB is 28.5 dBm. This type of phase shifter is especially suitable for high power transmit linear phased arrays. The chip occupies an area of 2.76 mm² including the pads.

An MEMS microwave power sensor with thermovoltage compensation and transformation is presented. The sensor obtains a thermovoltage which is linear to the input power, thanks to the Seebeck effect. However, the thermovoltage decreases as the frequency of input power increases due to the loss. The novelty is that the variation of thermovoltage has been compensated by an algorithm, and a transformation line is obtained to transform the thermovoltage to measured power displayed on liquid crystal display. The result indicates that the relative error is smaller than 1.5%. This system has practical applications in precise power measuring instruments.

A new method is reported to grow polycrystalline germanium (Ge) on silicon (Si) at low temperatures by direct current magnetron sputtering. The method is based on first sputtering a nanometre scale thickness Si layer on a Si substrate, followed by sputtering a Ge layer of the desired thickness. Using this approach, polycrystalline Ge has been deposited on Si substrate at 300°C, the lowest reported process temperature for polycrystalline Ge on Si by sputter coating. Characterisation by X-ray diffraction and Raman spectroscopy showed polycrystalline Ge in the presence of a Si interfacial layer. In the absence of the interfacial Si layer, amorphous Ge was obtained under the same process conditions. These observations indicate that depositing a Si interfacial layer helps in improving the Ge film quality in low-temperature deposition conditions. The approach developed here makes it possible to achieve post-CMOS integration in applications that have low thermal budget, such as flexible electronics based on Si/Ge devices. The increased process flexibility offered by this method is also expected to enable new applications.

The InAs/AlSb quantum cascade lasers (QCLs) operating ∼11 µm in the continuous wave (cw) regime at room temperature are reported. The lasers with cleaved Fabry–Perot resonators demonstrated pulsed threshold current densities below 1 kA/cm² at 300 K and operated in a cw up to 320 K that is the maximum temperature of such regime of operation for InAs-based QCLs. Distributed feedback lasers fabricated from the same wafer exhibited single frequency emission near 11 µm and operated in the cw regime up to 295 K.

The issue of reliability in power electronic converters (PECs) has received comparatively less attention by researchers. Among PECs, the multilevel inverter is a favourite choice of industry in the area of medium-voltage and high-power uses. To study the reliability of PECs, first, the failure rates of elements such as diodes, capacitors, and switches are introduced based on a relevant standard. Then, the reliability indices of two converters, 3-level and 5-level neutral point clamped, are calculated and compared. The results of the reliability study indicate an appropriate converter for sensitive application in industry.

It is generally assumed that better and more effective decisions can be made in radar sensor processing if more ‘information’ is available. However, this is not always the case since more information may not necessarily translate to better sensor performance due to information overload. The concept of information elasticity is useful in determining the relationship and role of information, in both qualitative and quantitative terms, to its interactions with the surroundings. While Shannon's well-known theory describes information in quantitative terms by assigning information value based on event probabilities, there are several instances where information obtained can only be described in fuzzy and qualitative terms. In this letter, the application of information elasticity to radar system performance is introduced.

Radar observation and signature identification of human motions have a variety of applications in social security and rescue operations. Both simulation and real radar experiment are conducted to investigate the polarimetric micro-Doppler signatures (MDSs) of a pedestrian. In the simulation, the motion-captured dataset developed by Carnegie Mellon University motion graphic laboratory is first used, then both Feldberechnung bei Korpern mit beliebiger Oberflache (FEKO) and MATLAB are used to calculate the radar scattering of pedestrian’ arms, based on which, horizontal-horizontal (HH) and horizontal-vertical (HV) polarimetric MDSs are analysed. Simulation results clearly show that in the time–frequency diagram, HH micro-Doppler (m-D) of arms is rising, whereas HV m-D is falling, which is verified by practical Ka-band radar experiment on a pedestrian. The work shows that by using polarimetric radar the m-D signature of human motion can be much well detected and identified which can be further explored for classification of different people.

Micro-Doppler of a rotor is of great importance in classifying and identifying a helicopter. In the past, the blade of a rotor was modelled as a rod. However, the blade has different tip shapes, which can be supplementary information for helicopter identification. The signal model of blades with three different tip types is derived. By analysing the theoretical and experimental data in the time–frequency domain, the potential of the tip shape in helicopter identification is shown.