A low-profile wideband dual-polarised X-band patch sub-array fed by a hybrid series/parallel network is designed for an integrated small-satellite synthetic aperture radar payload. The experimental results demonstrate that the sub-array, with 1 × 16 patch radiators, fully covers the targeted 9.65 GHz band with 14 dB bandwidths of 9–10.3 GHz for V-polarisation (VP) and 9.3–9.95 GHz for H-polarisation (HP). The isolation between the different feed ports is higher than 36 dB with a peak value of 45 dB. The sub-array achieves cross-to-co-polarisation ratios of below −32 dB within half-power beamwidth scopes of 6° for both HP and VP. The sidelobes maintain −24 dB for HP and −20 dB for VP. The average realised gains are around 17 dBi for both polarisations.

A novel frequency selective surface (FSS) exploiting 2.5D miniaturised hexagonal rings (2.5D MHR) is proposed. It can obtain an ultra-wide stopband and an improved polarisation-independent property due to the compact hexagon arrangement of 2.5D MHRs. The −10 dB bandwidth of the proposed FSS is from 1.97 to 8.08 GHz, and the deviation of resonant frequencies at 30° under transverse electric/transverse magnetic polarisations is merely 0.006f ₀. A prototype of the proposed FSS is fabricated and measured to validate the good consistency between simulations and measurements.

In deep learning architectures, rectified linear unit based functions are widely used as activation functions of hidden layers, and the softmax is used for the output layers. Two critical problems of the softmax are introduced, and an improved softmax method to resolve the problems is proposed. The proposed method minimises instability of the softmax while reducing its losses. Moreover, this method is straightforward so its computation complexity is low, but it is substantially reasonable and operates robustly. Therefore, the proposed method can replace the softmax functions.

An MIMO antenna consisting two loop elements is presented at 2.45 GHz industrial, scientific and medical band. The two elements are attached on the inner surface of the capsule, so that inner capsule space is saved to its maximum extent. Additionally, by orthogonally placing the two elements at bottom and side of the capsule, different polarisation directions are achieved; therefore, resulting in good isolation without introducing additional decoupling structures. Furthermore, communication link of the MIMO antenna with outside dipole is evaluated, revealing reliable communication performance. Finally, simulation results are validated by experimental results with good agreement.

This Letter presents the design and development of active myoelectric ankle foot prosthesis for transtibial amputees. The proposed device consists of a linear actuator mechanism, designed specifically to replicate a normal ankle joint and is controlled by user's myoelectric signal. The developed prosthesis provides active actuation during gait and is adaptive to change in walking speed. In this Letter, the authors report initial experimental characterisation of the performance of the control system. The developed device has been tested on a transtibial amputee. Results validate the adaptive trajectory control mechanism with dynamic speed change.

A new power-efficient dynamic residue amplifier for pipelined successive-approximation-register (SAR) ADCs is presented. A complementary input pair and a reference level detection technique are proposed to improve the performance of the dynamic amplifier. At a 400 MS/s sampling rate, the proposed amplifier achieves a gain of 16. The input referred noise is 57.2 μV and the total harmonic distortion is –57.1 dB. The power consumption of the proposed amplifier is 55.6 μW in 28 nm CMOS technology.

The design of ultra-low power advanced encryption standard (AES) encryption cores for emerging wireless networks and Internet of things systems by combining optimised architectures, a simple clock gating technique and an advanced 65 nm silicon on thin buried oxide (SOTB) CMOS process is presented. The implementation results show that the proposed 2-Sbox AES encryption core requires the smallest number of clock cycles and achieves the lowest power consumption of 0.4 µW/MHz which is 3.3× lower than that of the best previous presented AES encryption core, with a very small area overhead. Moreover, the proposed 1-Sbox AES encryption core consumes very low hardware resources of 2.4 kgates gate equivalent.

In-DRAM processing circuit is able to reduce operation time and power consumption than the traditional CPU + MEMORY system in performing the complicated computation such as convolution. These benefits are gained by bitwise and parallel processing of the in-DRAM convolution circuit. To realise the in-DRAM circuit, an inter-bank processing circuit is proposed with bitwise summation/comparison circuit for performing convolution inside DRAM. Compared to the intra-bank bitwise operation, the inter-bank circuit can significantly reduce the power consumption and the number of row activation cycles to accomplish convolution. For the number of cycles, the inter-bank circuit takes only 65 cycles for calculating 16 × 16 feature map. On the contrary, the intra-bank needs as many as 192 cycles. In terms of power consumption, the inter-bank circuit consumes smaller power by 35% than the intra-bank. In the proposed in-DRAM processing circuit, no complicated multiplier and adder are needed in performing the convolution. The Modified National Institute of Standards and Technology (MNIST) recognition rate of the proposed bitwise processing circuit can be as high as 97.28%, indicating very little loss due to the ternary kernels.

A novel four-output oscillator based on cross-coupled differential pairs is introduced and its validity is verified experimentally using discrete transistors as well as by simulations in a 90 nm CMOS technology. This oscillator has the unique capability of phase tunabililty where the phase shift between two of its outputs can be a design parameter while the phase shift between the other two outputs is always .

Submillimetre gaps caused by buttons, switches exist in the electronic device. IEC 61000-4-2 indicates that contact discharge method will be used if these floating metals could be touched in its normal use. Secondary discharge happens when conduct contact discharge on these floating metals. The influence of the secondary discharge on the repeatability of contact discharge method using experimental method is analysed. At same applied voltage, the secondary discharge current varies largely, causing bad repeatability. The time lag is the main parameter that influences the secondary discharge greatly. The time lag distribution is also analysed.

2D-to-3D conversion has been studied over past decades and integrated to commercial 3D displays and 3DTVs. Generally, depth cues extracted from a static image are used for generating a depth map followed by depth image-based rendering for producing a stereoscopic image. Further, the motion has been considered as an important cue for motion depth estimation. In most works, motion estimation has relied on block-based motion estimation, optical flows, and their variants even though they provide inaccurate data and high computation time, posing performance bottleneck. These problems by proposing Motion History Image-based motion depth estimation method are addressed. Experimental results show that the proposed method is not only faster than the conventional methods but also outperforms them in terms of motion depth estimation.

A method is proposed to obtain accurate disparity maps for high dynamic range (HDR) scenes using stereo image pairs acquired under different exposure times and viewpoints. In HDR scenes, saturated pixels such as too-dark or too-bright pixels are inevitable because of the limited bit-depth representations of images. These saturated regions include little information for matching images and harm the performance of conventional stereo matching methods. To address this problem, a method is proposed that generates a new cost volume by fusing cost volumes obtained using different stereo image pairs taken under different exposure times as well as different points of view. In addition, the directional semi-global matching method is proposed to efficiently optimise the cost volume. Experimental results show that the proposed method generates more accurate results for saturated regions than existing methods on various datasets.

A compact and simple differential ultra wideband (UWB) equal power divider (PD) with one narrow notch-band is presented. The proposed PD is based on slotline resonators and balanced stepped-impedance microstrip-to-slotline transition structures. A wide differential-mode (DM) impedance bandwidth covering from 1.8 to 11.5 GHz can be achieved. Besides, independent common-mode (CM) responses with a larger bandwidth and higher suppression can be obtained. It is noted that the DM passbands are independent from the CM responses, which significantly simplify the design procedure. In addition, a narrow and sharp DM notched band from 5.8 to 5.9 GHz is generated by adding one pair of quarter-wavelength short-circuited stubs next to the microstrip line symmetrically. In order to illustrate the effectiveness of the design, a prototype is fabricated and measured. A good agreement between the simulated and measured results is observed. To the best of authors’ knowledge, the proposed balanced UWB PD is the first ever reported.

A new method for achieving amplitude reconfiguration in a reflectarray antenna is presented in this Letter. An individual unit cell is a compact multilayer structure, including a silver inkjet-printed layer for rapid prototyping of the reflectarray. A small infrared light emitting diode (IR-LED) illuminating a silicon wafer provides the reconfiguration in the system. Various illumination intensities of the IR-LED allow for differing magnitudes of reflection from the unit cell. This provides the potential for radiation pattern tapering or amplitude modifications of the gain of the reflectarray. Simulation and measurement results for a single unit cell are presented here, with the matching between measurement and simulation also allowing for the change in the values of conductivity of the silicon to be extracted.

A compact quarter-mode substrate integrated waveguide (QMSIW) quasi-elliptical bandpass filter is presented based on a novel interdigital-like capacitive coupling structure. This type of electric coupling structure is very suitable for the open boundary to implement the cross-coupling in classical quadruple topology. By this characteristic, a QMSIW quasi-elliptical filter working at 5 GHz is designed to demonstrate the superiority of this structure to the electric walls. Benefitting from the QMSIW technology, the wide-stopband feature is intrinsically achieved for the filter and the first spurious resonance is occurred at around two times the centre frequency.

A novel CMOS active inductors-based Wilkinson power divider for automotive radar application is proposed and designed in a standard 45 nm CMOS technology. The proposed power divider is based on T-network of the series-MOS capacitor and active shunt-inductor which provide higher inductance tuning ranges, lower power consumption, and higher self-resonant frequency. Simulation analysis of the proposed power divider is carried out over virtuoso SpectreRF tool by Cadence. The circuit consumes a total power of 51.2 μW from a 1.5 V power supply; 11.5 × 9.5 μm² layout area and the return loss of the circuit at 76.5 GHz frequency are 43.5 dB. Moreover, the isolation between two output ports and insertion losses between input and output ports are 30 and 3.4 dB, respectively. The results show that the proposed design is efficient for long range automotive radar application.

A novel E-plane probe microstrip-to-waveguide transition for millimetre-wave application is proposed. By introducing a fin-line back-short structure, tight-tolerance machining and assembling of the waveguide back-short commonly encountered with traditional E-plane probe microstrip-to-waveguide transition are no longer necessary. A Ka-band transition prototype is designed and fabricated to validate the design concept. Simulated and measured results agree well and both of them show the proposed transition achieved good return and insertion losses over the full Ka band.

Simultaneously generating two independently tunable chirped microwave waveforms based on optical spectral shaping and wavelength-to-time mapping with an arrayed waveguide Sagnac interferometer that incorporates linearly chirped fibre Bragg gratings are demonstrated.

An innovated simple fabrication process is adopted to fabricate a novel gate self-aligned (GSA) graphene field effect transistor (GFET). First, stacked source/drain electrodes with triple-layer metal are formed. Then, after slightly etching of the second metal layer, laterally recessed profiles are formed, which leads to the self-aligned (SA) gate. A noticeable feature of the GSA-GFET is that the access resistance is not changed with the level of the lateral recessing, which leads to a very small access resistance. Compared with the non-SA-GFET with same gate length and width, the contact resistance of the GSA-GFET is reduced by 68%, the peak g_m is 3.6 times improved, the on/off ratio is increased from 1.8 to 3.2.

We report a distributed Bragg reflector-free semiconductor disc laser which emits 10 W continuous wave output power at a wavelength of 1007 nm when pumped with 40 W at 808 nm, focused into a 230 μm diameter spot on the gain chip. By introducing a birefringent filter plate in the laser cavity the wavelength could be tuned from 995 to 1020 nm. The laser consisted of a gain chip located at the beam waist of a linear concentric resonator with an output coupling of 2.15%. The gain chip consists of a 1.574-μm-thick resonant periodic gain structure, with ten In_0.13Ga_0.87As quantum wells embedded in strain-compensating GaAs_0.94P_0.06 barrier layers, van der Waals bonded to a silicon carbide intra-cavity heat spreader.

The optimisation of AlGaInP/GaInPAs MQW heterostructure metal-organic chemical vapour deposition growth as well as the improvements of active channel formation and P-contact deposition technologies is shown to enable a significantly increased external differential efficiency up to 0.5 mW/mA and catastrophic optical damage threshold up to 50 mW of spatially single-mode superluminescent diodes (SLDs) at central wavelength of 675 nm. Life time tests demonstrated high reliability of new SLDs at continuous wave output power of up to 30 mW. The dependencies of spectral and power characteristics of these SLDs on active channel dimensions are presented. To the best of knowledge, these are the most powerful and broadband SLDs at 675 nm.

An adaptive delay control method for a phase-shifted full bridge converter with a synchronous rectifier is presented. With this control, the delay time between primary and secondary switches can be optimised to reduce dead time, according to output power. Moreover, due to the poor third quadrant conduction of gallium nitride (GaN) high-electron-mobility transistors (HEMTs), the dead time needs to be optimised to utilise the benefits of a GaN HEMT. The experimental results with a 500 W prototype show that the efficiency can be improved by 0.7% with the proposed control.

In order to obtain the capability of neutral point potential balancing with low switching frequency, a novel balance control algorithm for neutral-point-clamped (NPC) three-level inverter based on Selective harmonic elimination pulse-width modulation (SHEPWM) are proposed. On the basis of the switch sequences and voltage vector action angle corresponding to the three-phase SHEPWM waveform at different modulation index, the three kinds of redundant vector adjustment schemes are designed. Then, load current and neutral point potential feedback to the controller, and the three-phase pulse-width modulation signal adjusted directly by the hysteresis controller to realise neutral point potential balance. Experimental results show that different redundant vector adjustment schemes have different neutral point potential balancing speed and average switching frequency, but do not affect the harmonic elimination ability of the line voltage.

In this Letter, the duty cycle generation scheme is presented and implemented, which can improve the input performances of the three-phase single-stage full-bridge power factor correction (PFC) converter. The analysis and discussion is aiming at the operation of the PFC converter in balanced grid condition. On the basis of the instantaneous expression of the three-phase input current, the ideal duty cycle of each phase is obtained. To achieve a good PF for each phase, a simplified duty cycle generation scheme is presented and implemented in the three-phase PFC converter. The simulating and experimental results based on a 500 W prototype show that after adoption of the presented duty cycle generation scheme, a higher PF has been achieved for each phase of the three-phase PFC converter.

The design of a 24 GHz frequency divider-by-10 for accurate indoor localisation systems is presented. It is proposed to use frequency dividers as active reflector tags in a frequency-modulated continuous wave indoor localisation system in order to reduce interferences caused by direct reflections of the interrogating signal. Since frequency dividers are subharmonic generators, this allows achieving conversion gain in the reflected signal. The frequency divider is fabricated using GLOBAL FOUNDRIES 45 nm-silicon-on-insulator technology. It consumes only 5.7 mW from a 1 V supply. It has a wide locking range of 33% and an efficiency of 3.58 GHz/mW. To the best of authors’ knowledge, the use of frequency dividers as active reflectors was not studied before.

A robust design method is proposed to optimise the measurement matrix for a compressive sensing multiple-input multiple-output (CS-MIMO) radar system in the presence of clutter. The robustness to the proposed measurement matrix design is conducted against uncertainty on the target angle using a max–min optimisation problem to maximise the worst-case signal-to-clutter-plus-noise ratio. The numerical results demonstrate the effectiveness of the proposed method in CS-MIMO radar.

A closed-form analytical solution is derived for the statistical outcome of a random walk along a return path. The random walk is generated from the cumulative sum of correlated samples in a Gaussian-distributed autoregressive sequence. The outcome exhibits a smaller variance compared with a one-way path of equivalent length due to cancellation of correlated steps along the return leg. Furthermore, the variance decreases towards zero as the correlation coefficient approaches unity. An example application for this general result is the modelling of cumulative errors in dead-reckoning navigation systems, e.g. Doppler velocity log-aided inertial navigation systems used commonly on underwater vehicles. In this particular application, it can be used to express and quantify the natural cancellation of correlated error components between subsequent opposing legs in a typical ‘lawnmower’ survey pattern.

Massive MIMO with high spectral efficiency is one of the key technologies for future 5G wireless communications. For signal detection in such systems, a decision-aided Jacobi (DA-Jacobi) iteration is proposed, which can improve the convergence speed as compared with the conventional Jacobi iteration for calculating the result of the linear minimum mean-squared error (MMSE) detection, and, at the same time, can come with lower computational complexity. Simulation results confirm these advantages and demonstrate that the error-rate performance of the proposed DA-Jacobi iteration can be even better than that of the exact linear MMSE detection.

Performance of large-scale MIMO systems is restricted by pilot contamination, coherence block length, hardware impairments and other system parameters. In this Letter, the authors aim to improve the bandwidth efficiency (BE) of massive MIMO systems in multi-cell scenarios. An improved version of the zero forcing (ZF) algorithm is proposed, based on that new expressions for BE are derived. The authors have compared the proposed algorithm with the conventional ZF algorithm and simulation results show sufficient improvement of performance in terms of BE.