A novel 60 GHz high-gain planar artificial magnetic conductor (AMC) antenna is proposed. The prototype of the antenna is a dipole structure with a broadband input impedance match. Parasitic patches and a novel AMC plane are successively used to enhance its broadside gain. The antenna has a compact size of 7.5 mm × 8 mm, including the modified AMC plane. Simulated and measured results both show the antenna has good properties of return losses better than 10 dB, stable peak gains up to 10.9 dBi and favourable radiation patterns from 57 to 64 GHz, which all denote that it is fit for 60 GHz wireless portable communication systems.

A new method is proposed to estimate the direction-of-arrivals (DOAs) of multiple narrow-band signals using a co-prime array (CPA). The CPA is divided into two uniform linear arrays (ULAs) and two polynomials are derived by utilising the unitary transformation technique on the covariance matrices of these two ULAs. Rather than rooting the two polynomials straightforwardly, their first-order derivatives are exploited to construct a new difference polynomial, and DOAs are uniquely estimated without ambiguity by finding the roots of this difference polynomial that lie closest to the unit circle. The new technique shows improved accuracy with reduced complexity as compared to most state-of-the-art methods, which are verified by numerical simulations.

In this work, a high-gain circularly polarised (CP) substrate integrated waveguide (SIW) bow-tie antenna is presented. The proposed antenna includes a pair of bow-tie radiators. To centralisation radiated pattern and recede side lobe and back lobe level two tilted rows of metalised via hole at the end of the SIW feed line is used. The methods of increasing the antenna gain and generating the CP are discussed. The proposed antenna was fabricated to validate simulated results. The designed structure operates across 40–68 GHz and exhibits a gain of 10–12.5 dBic. In addition, the proposed antenna exhibits a 3-dB axial ratio bandwidth from 54 to 64.3 GHz.

Steady-state visual evoked potential (SSVEP) has been widely used in electroencephalogram (EEG)-based brain–computer interfaces (BCIs) due to its high information transfer rate (ITR) and short training time. Current methods usually measure SSVEP from electrodes on the scalp, which is an uncomfortable and time-consuming method. Furthermore, most research relies on expensive and non-portable EEG devices. To utilise BCIs in daily life, however, these are critical issues to address. Hence, a wearable EEG device for in-ear SSVEP detection is proposed. The system is 40 × 21 × 10.5 mm³ and weighs 14.2 g, thus being light weight and wearable. Moreover, the system has a noise level of 0.11 µV_rms, which is comparable with commercial EEG systems. Six subjects participated in an offline BCI experiment that consisted of six visual targets using the developed in-the-ear EEG system. The results showed a highest ITR of 11.03 ± 4.18 bits/min with an accuracy of 79.9 ± 13.1%, and the experiments demonstrated that the system can be utilised for unobtrusive monitoring of SSVEP in BCI applications.

A calibrated 10 b 5 MS/s 28 nm CMOS successive-approximation-register ADC based on an integer-based split capacitor array is presented. The proposed ADC employs a split capacitor array to optimise the overall power consumption, chip area and linearity performance. An attenuation capacitor between two capacitor arrays is implemented with an integer multiple of unit capacitors rather than a fraction of unit capacitors. The proposed calibration of capacitors reduces the non-linearity error caused by device mismatches in the conventional split capacitor array. The measured prototype ADC which has an active die area of 0.063 mm² shows a maximum signal-to-noise-and-distortion ratio and spurious-free dynamic range of 59.25 and 70.44 dB, respectively, and consumes 42.5 μW at 0.7 V and 5 MS/s. Moreover, the measured differential non-linearity (NL) and integral NL are within 0.36 and 0.52 least significant bit, respectively, after calibration.

The quantised inverter amplifier concept is introduced, where an input signal is sliced and amplified by an array of amplifiers. This strategy expands the dynamic range of the amplifier and relaxes the power demand of the following stages as the total output swing can virtually exceed the supply voltage. Moreover, using multiple amplifiers helps to linearise the input–output transfer characteristic. Simulations results confirm the presented theory.

Spin-wave (SW) logic cell with a parallel 2-port excitation configuration that operates in XOR and OR logic regimes is described. The peculiarity of the solution is that magnetic field of lateral excitation electrodes couples to magnetic field component of SW resulting from its 2D confinement. The operation principle of the device can be interpreted as single channel multiport interference-based element.

This Letter presents the architecture implementation and testing of an single instruction multiple data (SIMD) processor for energy aware embedded morphological visual processing using the simplicial piece-wise linear approximation. The architecture comprises a linear array of 48 × 48 processing elements, each connected to an eight-neighbour clique operating on binary input and state data. The architecture is synthesised from a custom designed ultra low-voltage CMOS library and fabricated in a 55 nm CMOS technology. The chip is capable of dynamic voltage/frequency scaling with power supplies between 0.5 and 1.2 V. The fabricated chip achieves an overall performance of 293 TOPS/W with dynamic energy dissipation efficiency of 3.4 fJ per output operation at 0.6 V.

This Letter proposes an effective approach for the scaling registration of point sets. By imposing the emphasis on the scale factor, the authors design a novel objective function, which can avoid the phenomenon that the scale factor converges to zero. Subsequently, the well-designed function is optimised by the proposed scaling iterative closest point algorithm, which can calculate the optimal scaling transformation by iterations. The proposed approach is validated on public data sets, demonstrating its superiority over previous approaches on efficiency and robustness.

Recently, convolutional neural networks (CNNs) have shown great performance in different problems of computer vision including object detection and localisation. A novel training approach is proposed for CNNs to localise some animal species whose bodies have distinctive patterns such as leopards and zebras. To learn characteristic patterns, small patches which are taken from different body parts of animals are used to train models. To find object location, in a test image, all locations are visited in a sliding window fashion. Crops are fed into trained CNN and their classification scores are combined into a heat map. Later on, heat maps are converted to bounding box estimates for varying confidence scores. The localisation performance of the patch-based training approach is compared with Faster R-CNN – a state-of-the-art CNN-based object detection and localisation method. Experimental results reveal that the patch-based training outperforms Faster R-CNN, especially for classes with distinctive patterns.

The synthesis of thinned planar arrays with two-fold redundancy in microwave interferometric radiometers (MIRs) is discussed. Based on (double) difference bases, a deterministic method is proposed for constructing two-fold redundancy planar arrays (TFRPAs). The resulting TFRPAs sample the spatial frequencies at least twice within a given baseline coverage, which contributes to the reliability of MIR systems. A comparative study with two typical TFRPAs (i.e. the open-ended ‘Cross’ and the closed ‘’ array configurations) is carried out, concerning array sampling efficiency in the spatial frequency domain. The numerical examples are presented to demonstrate the effectiveness of the proposed synthesis method.

Previously-reported purely-organic microelectromechanical relays suffer from a high on-state resistance above 1 GΩ, which makes them unsuitable for relay-based organic integrated circuits. This letter demonstrates partially-organic relays that employ a metal and/or a metal oxide for their contacts to alleviate the issue.

A record output power of 16.1 W with a direct-bonded dual-SiC-heatspreader distributed Bragg reflector (DBR)-free active region at 10.5°C coolant temperature is reported. A comparison in laser performance confirms the dual-heatspreader DBR-free configuration dissipates heat more effectively than the single-heatspreader geometry.

We demonstrate, for the first time, a single section passively mode-locked InAs/InGaAs quantum dot laser directly grown on on-axis (001) GaP/Si substrate. The laser has a continuous-wave threshold current of 34 mA at 20°C. By forward biasing the laser gain section current at 470 mA, 490 fs pulse generation with 31 GHz repetition rate can be obtained. This simple femtosecond pulse generation structure with CMOS fabrication compatibility makes the laser a promising light source candidate in future large-scale silicon photonic applications.

Based on the idea of virtual synchronous machine, a control strategy of traction rectifier is proposed. The proposed strategy provides the voltage and frequency support for the traction grid, damps oscillation, which helps to improve the stability of the power system. In this way, the electrical energy can be fed back to the traction grid more friendly in the regenerative braking condition. The experiment proves that the control strategy has good control effect both on traction and regeneration braking conditions.

The letter deals with the methodology for determining the optimal number of phases of a multi-phase DC to DC buck converter from the point of view of its maximum efficiency. It also analyses the impact of individual parameters of the converter and the used components on the number of these phases.

A correction to an error in the equation of a paper published by the authors in the Electronics Letters entitled ‘General SVPWM strategy for three different four-switch three-phase inverters’ is given. The errors are analysed and two modification methods are proposed.

An average current controller (ACC) that can accurately regulate the light-emitting diode (LED) forward current for lighting applications is proposed. The proposed ACC employs a charge sharing method to achieve a highly accurate average LED forward current by compensating for an error occurred when the LED forward current is sampled. It was fabricated using a 0.35 μm CMOS process technology and occupied a small chip area of 1028 μm × 728 μm. The measurement results showed that the proposed ACC achieved a deviation in the average LED forward current of <0.6% over the entire input voltage range while achieving a maximum power efficiency of 93.6%. Therefore, the proposed ACC is suitable for high-quality LED lighting systems requiring an accurate LED forward current.

Many studies have demonstrated the capability of radar micro-Doppler signature for classifying micro-drones. However, most existing works on radar classification of drones are based on the assumption that the received signal is only reflected from a single drone. When multiple drones are present simultaneously, the existing methods of drone classification fail due to the superimposition of the micro-Doppler features of multiple drones. In this Letter, a method for detection of multiple drones is proposed. First the time–frequency spectrogram is converted into the cadence-velocity diagram (CVD), which expresses how the curves in the time-frequency-domain repeat. Then the cadence frequency spectrum (CFS), as the basis vector of the training data from each class, of the CVD is extracted. Finally, the K-means classifier is used to recognise the component of multiple micro-drones based on the CFS. The experimental results on real radar data demonstrate that the proposed method is capable of dealing with multiple drones with satisfactory classification accuracy.

The attitude of synthetic aperture radar (SAR) antenna cannot be fully controlled or precisely measured, which causes the ambiguity of Doppler centroid and thus degrades the image quality. A few Doppler ambiguity resolvers (DARs) have been developed by evaluating image quality, which focus on the data with all possible ambiguity numbers until the maximum image contrast or the minimum image entropy is found. Despite of their robustness on various cases, these approaches rely on repeatedly focusing the data, resulting in a heavy computational load. A new DAR that successfully employs the property of range profiles is proposed, and this approach greatly improves the efficiency while keeping robustness.

A precise obstacle localisation method for automatic parking systems is proposed. The proposed method improves the obstacle localisation accuracy by fusing only the sensors already installed on mass-produced vehicles. This method finds the initial obstacle location using ultrasonic sensors. On the basis of the initial obstacle location, it detects the obstacle's vertical outlines using images provided by an around view monitor system while the ego-vehicle is moving. The sequentially detected vertical outlines are combined based on the ego-vehicle positions estimated by built-in motion sensors. Finally, the obstacle location is refined by calculating the intersection point of the combined vertical outlines. In experiments, the proposed method was quantitatively evaluated and outperformed the previous method.

An initial condition-index chaos shift keying modulation is proposed. This design aims to increase the spectral and energy efficiencies to unprecedented levels. The proposed scheme exploits the initial conditions to generate different chaotic sequences to convey extra bits per transmission. In the proposed design, the input data stream is formed in blocks of bits. In this architecture, n bits are mapped into predetermined initial conditions that are used to generate unique chaotic sequences at the transmitter. At the receiver side, the predetermined initial conditions are used to generate a set of N chaotic sequences that are correlated with the received signal. The index of the initial condition for which the chaotic sequence produces a maximum correlation with the received signal is selected to recover the mapped bits, and the corresponding sequence is used to despread the transmitted modulated bit. To validate the proposed scheme, the bit error rate over fading channels is analysed and formulated and the proposed system performance is compared with other conventional and index modulation schemes. In comparison to rival modulation schemes, the results obtained in the proposed work show a competitive performance.

A new selected mapping orthogonal frequency division multiplexing modulation (SLM-OFDM) that generates symbol candidates using U inverse fast Fourier transform is presented. The complementary cumulative distribution function of peak-to-average power ratio (PAPR) of the so-called GreenOFDM is derived and computer simulations show that the proposed method outperforms any other SLM-OFDM proposed method so far. Also, GreenOFDM is compared with localised single carrier frequency division multiple access as it is a well-known PAPR reduction technique standardised for long-term evolution advanced.

A frequency-selective limiter (FSL) using an injection locked oscillator (ILO) is proposed for a blocker cancellation, which employs an ILO in the feedforward path as a high-Q notch filter to select and amplify the blocker from the input signal. The ILO also functions as a phase shifter providing a proper phase delay so that two blockers in the feedforward and thru paths cancel each other out in the combining node. The proposed FSL is fabricated in a commercial 0.15 μm GaAs pHEMT process with a maximum blocker suppression of 27 dB in the 50 MHz spacing two-tone measurement at the K-band. Thus, it provides a blocker suppression higher than 20 dB over the 250 MHz blocker bandwidth.

Quasi-cyclic low-density parity check (QC-LDPC) codes are being widely used in communication standards, and the decoder of QC-LDPC codes requires a unique type of rotator. The unique rotator, called a multi-size cyclic-shifter (MSCS), should be able to rotate data with various sizes, and many structures have been proposed for the operation. A low-complexity, high-speed MSCS structure is proposed, in which a part of the previous smallest structure is replaced with a structure with less delay and comparable area. The synthesis results present that the proposed structure achieves not only the highest speed but also the lowest complexity after synthesis.

Optimal power allocation (PA) scheme for distributed antenna systems with orthogonal frequency division multiplexing (DAS-OFDM) over frequency-selective fading channels is presented. The PA design is to optimise the transmit powers of subcarriers to maximise the capacity subject to the total power constraint. Based on the Karush–Kuhn–Tucker optimality conditions, the optimal PA to the distributed nodes for a subcarrier can be simplified to allocating the power to the node of the largest channel gain. With this result, an efficient algorithm is derived to obtain the optimal PA to the nodes for all the subcarriers of the DAS-OFDM. Compared with an existing suboptimal scheme, the developed scheme can obtain higher capacity and has lower complexity. By computer simulations, the effectiveness of the proposed scheme is verified.

A novel algorithm for parameter estimation of cubic frequency modulated (CFM) signals, known as a modified integrated cubic phase function high-order ambiguity function (MICPF-HAF), is introduced. The MICPF-HAF demodulates CFM signals to quadratic FM (QFM) signals via phase differentiation, and then the MICPF is applied to realise the parameter estimation of QFM signals. The analyses and simulations show that the proposed MICPF-HAF achieves a great improvement in anti-noise performance in comparison with the HAF and the CPF-HAF-based methods.

A transmit antenna shuffling method is proposed for a power efficient 2 × 1 space–time block code (STBC) system. Unlike a conventional STBC system that has identical power amplifiers (PAs), an asymmetric STBC (A-STBC) transmitter considered in this Letter has two asymmetric PAs, i.e. low-power and high-PAs. Considering the asymmetric PAs, the authors propose an antenna shuffling method with 1-bit feedback to improve the power efficiency (PE) of the STBC system. Numerical results verify that the proposed A-STBC system with 1-bit feedback antenna shuffling achieves a better PE-and-rate tradeoff and the potential ability of the small amount of feedback information for the power efficient systems.

Tunable surface-acoustic-wave-(SAW)-based bandpass filters (BPFs) with flat in-band group delay (τ _g) and variable passband bandwidth (BW) are reported. They are based on N hybrid acoustic-wave-lumped-element-resonator (AWLR) modules shaped by one lumped-element resonator and K RF-switched SAW resonators that are arranged in a Gaussian-type source-to-load impedance-inverter network. Fractional bandwidth (FBW) tuning is achieved by reconfiguring the number of SAW resonators within the AWLR modules. Major advantages of the proposed filter concept when compared to conventional SAW BPFs are as follows: (i) they do not depend on the electromechanical coupling coefficient (k_t ²) of the SAW resonators – FBW>k_t ² can be realised –, (ii) they do not require lossy elements or SAW resonators with different frequencies, and (iii) they can be tuned. For experimental-validation purposes, a 433.9 MHz two-pole/four-transmission-zero prototype was built and measured. It exhibited flat-in-band-τ _g passbands with discretely-tunable BW between 0.18 and 0.45 MHz (i.e. 2.5:1 tuning ratio).