A wideband planar endfire circularly polarised loop antenna is proposed. The antenna is fed by a microstrip line with a novel ground plane instead of a coaxial probe. The microstrip line part and the loop part generate the vertical polarisation and the horizontal polarisation, respectively. Two stubs added on the loop contribute to the bandwidth improvement. The proposed antenna achieves wide impedance bandwidth (|S11| < −10 dB) and wide 3-dB axial ratio bandwidth, both of which can cover the frequency range from 8.0 to 12.5 GHz (43.9%).

The performance of a loop-type ground radiation antenna was analysed based on its impedance level for an arbitrary location on the ground plane. At the corner of the ground plane, the open capacitor configuration (i.e. the PIFA type antenna) shows better performance, whereas the loop-type antenna with a capacitor and shorted inductor is a better choice at the middle of the ground plane. The optimum value of the impedance level of the antenna determines the antenna performance for an arbitrary location on the ground plane is proposed. The idea was demonstrated using a 10 × 4.5 mm loop-type antenna, which was fabricated on the 50 × 25 mm ground plane. The design is intended for mobile device applications operating in the Bluetooth band.

A new design of a circularly polarised antenna based on the tightly coupled mechanism is presented. The proposed antenna consists of four tightly coupled dipoles, four impedance transforming networks and a wideband feeding network. Owing to the strong mutual coupling between coupled dipole elements, the proposed antenna realises a wide operating bandwidth. A prototype is manufactured and measured to validate the method. The measured results indicate that the proposed design provides a 10 dB return loss bandwidth of 101% (1.7–5.2 GHz) and a 3 dB axial ratio bandwidth of 77% (2.0–4.5 GHz). The design has a 3 dB gain bandwidth of 56% from 2.6 to 4.6 GHz with a peak gain of 10.4 dBic. Acceptable agreements can be obtained between the simulated and measured results.

The lack of models for automatic control of mean arterial pressure (MAP), in real-time, associated with variability in response to sodium nitroprusside infusion, makes it impossible to validate automatic MAP controllers. Therefore, this Letter presents a low-cost innovative real-time model to MAP. Therefore, the authors used a variation of the mathematical model of Slate, implemented in MATLAB^®. The system was developed with the capabilities of Simulink^® and deployed to a single-board computer. The results showed that the embedded model presented an error <3% for a target MAP of 100 mmHg, allowing the use of this model, in real time, for validation of embedded MAP controllers.

An area efficient non-fractional binary-weighted capacitive-array with attenuation capacitor (NFBWA) digital-to-analogue converter (DAC) is presented for successive-approximation-register ADC. Based on linearity and matching requirement, the segmentation degrees (i.e. the number of bits in each split capacitive sub-array) are optimised to minimise the switching power and area. The proposed DAC improves the Walden figure-of-merit performance by 1.67 and 5.45 times, respectively, compared with that of fractional binary-weighted capacitive-array with attenuation capacitor (FBWA) DAC and conventional NFBWA DAC at the same unit capacitor size and linearity requirement.

A class AB differential difference amplifier for continuous-time common-mode feedback (CMFB) is presented. It employs local CMFB to improve gain-bandwidth product and dynamic performance of the CMFB loop, without increasing static power consumption or supply voltage requirements. Measurement results for a 0.5 μm CMOS test chip prototype validate the proposal.

A variation-resilient single-ended six-input lookup table circuit, which makes it possible to implement any arbitrary six-input logic gates, is proposed. Since operating point is optimally tuned by the redundant magnetic tunnel junction devices after chip fabrication, adequate p-channel metal-oxide semiconductor (PMOS) feedback can be performed, which results in variation-resilient, energy-efficient operation. In fact, the energy consumption of the proposed circuit is 66% smaller than that of the conventional single-ended circuit.

An energy-efficient DAC scheme with most significant bit (MSB) split structure is proposed for successive approximation register (SAR) ADCs. The proposed scheme consumes no switching energy in the first three conversion cycles, and the switching energy for the rest cycles is further optimised using the single-side switching method. Furthermore, the proposed capacitor-swapping reset scheme eliminates the reset energy. Taking the reset energy into consideration, the proposed scheme reduces the total average energy by 99.23% compared with the conventional SAR ADC architecture and hence achieves high energy-efficiency.

A new Schmitt trigger circuit comprises of single multiple output current follower differential input transconductance amplifier and one grounded resistor is presented. The presented circuit provides both clockwise and anticlockwise hysteresis simultaneously with independent and electronic control of threshold levels. The amplitudes of output currents are also independent and electronically controllable. Experimental results using commercial ICs have been depicted to confirm theoretical analyses.

Highly accurate and power-efficient hybrid battery charger is proposed which includes the switching and linear chargers as well as a charging current compensator. The proposed current compensator operates the switching charger in the constant current (CC) mode to achieve high power efficiency and to improve the charging current accuracy with a small-sized inductor. It also operates the linear charger to minimise the charging current variation in the trickle current (TC) mode and to reduce the battery charging voltage error in the constant voltage (CV) mode. The proposed battery charger was fabricated using a 0.18 μm CMOS process and occupies a chip area of 1.63 mm². The measurement results show that the proposed battery charger achieves a charging current accuracy of 96.2% in the CC mode, which is improved by 15.8% at a target current of 500 mA, as well as a power dissipation of 0.26 W. In addition, the charging current variation and charging voltage error are measured to be <2 mA_P−P in the TC mode and 0.48% in the CV mode.

A memristor crossbar-based technique for highly parallel string matching is presented. An input string can be simultaneously compared against a bank of stored words, each having a different length, due to the self-biasing nature of the crossbar circuit. This string matching system essentially acts as a ternary content-addressable memory (TCAM). Owing to the high-density nature of nanoscale memristor crossbars, this system can provide a significant area reduction when compared alternative TCAM designs while remaining competitive in terms of timing and energy.

Game theory, optimal control theory and adaptive dynamic programming (ADP) to deal with the optimal tracking control issue for unknown non-affine multi-player systems are integrated. It is known that non-zero-sum games of non-linear multi-player systems rely on solving a set of Hamilton–Jacobi equations, which are generally difficult to be computed analytically due to the non-linear nature. Traditional ADP methods require the knowledge of accurate system models, and only consider the simple affine system version. A novel data-driven Q-learning approach, which only needs the measurable data generated by running systems, is proposed. To implement this method, neural networks (NNs) are utilised, and NN weights are updated through the least-square form.

The two-layer motion estimation (TME) algorithm searches the motion vectors on the layers with partial distortion measures to boost the computational speed of motion estimation. An efficient motion estimation algorithm is presented in which a fast partial distortion calculation method (FPDCM) has been developed to speed up the motion estimation process on the layers without affecting motion prediction quality. This FPDCM efficiently calculates the partial distortions on the layers faster by removing the redundant computations involved in the partial distortion calculation. As a result, the speed with motion estimation on the layers by using FPDCM is increased when compared with the TME algorithm. Experimental results are given to show the superiority of the proposed algorithm over TME as well as the state-of-the-art fast block matching algorithms.

To improve the availability of the software-defined networking (SDN) under distributed denial of service (DDoS) attacks, a multi-queue SDN controller scheduling algorithm based on time slice allocation strategy is proposed. The proposed algorithm can take different time slice allocation strategies according to the intensity of DDoS attacks and use SDN controller to schedule processing flow request from different switches (including the switches suffering from different degrees of attacks and normal switches) to ensure better protection to the normal switch in the network under DDoS attacks. Simulation results are presented to show the effectiveness of the proposed algorithm.

For the first time, 3D printed metal-pipe rectangular waveguides (MPRWGs) have been demonstrated in the WM-380 (500–750 GHz) and WM-250 (750 GHz–1.1 THz) waveguide bands. The ultra-high spatial resolution offered by the new RECILS additive manufacturing technology enables the precision fabrication of these prototype MPRWGs at such high frequencies. This enabling technology avoids the need for access to expensive microfabrication resources and, thus, opens up the terahertz spectrum to the low-cost manufacture of passive components.

A broadband E-plane right-angle transition from a substrate integrated waveguide (SIW) to a rectangular waveguide (RWG) is proposed. A stepped waveguide, a coupling aperture, and two inductive posts are applied to provide a good impedance matching between the SIW and the RWG. A back-to-back transition prototype is designed, fabricated, and measured at Ka-band. Measured results show a good agreement with the simulated one: the insertion loss of a single transition is <0.6 dB and the return loss better than 15 dB is obtained from 32.6 to 38.1 GHz. The broadband transition can be used in front-end circuits of millimetre-wave communication, radar, and measurement systems.

A compact lowpass filter (LPF) using a lattice-shaped resonator is presented with a wide rejection band and sharp roll-off. The designed LPF has −3 dB cut-off frequency at 4.34 GHz. The fabricated LPF is simulated and tested; there is a good agreement between the simulation and experimental results. Experimental results show that the maximum variation of flat group delay is only 0.3 ns in the passband. Also, the measured return-loss and insertion loss are more than 19 dB and <0.1 dB in 88% of the passband region, respectively. The size of the designed filter is only 22.5 × 8.65 mm².

A novel circuit is presented for the design of transmission-type negative group delay circuit (NGDC) with low signal attenuation. By loading a lumped resistor at a specific point on the loose-coupling microstrip (MS) resonator, a lossy coupled-line resonator is proposed, the size of which is effectively reduced by employing an open radial patch. A cascaded two-stage NGDC scheme is presented to realise an enhanced negative group delay (NGD) value and better reflection coefficients. The layout of the two-stage NGDC is designed in an anti-symmetrical back-to-back manner. To validate the performance of the proposed circuit scheme, a prototype of the two-stage NGDC has been designed, the working bandwidth of which is 35 MHz with a centre frequency of 1.79 GHz. This circuit is fabricated on Rogers RO4350B substrate with a thickness of 20 mil. A measured maximum NGD of −7.7 ns and a corresponding signal attenuation of as low as 8.6 dB have been obtained. Reflection coefficients are better than −20 dB. This NGDC occupies a compact size of 0.3λ _g × 0.18λ _g, which is much smaller compared to the previously reported NGDCs with distributed elements.

The design and results of a D-band frequency doubler using two parallelly mounted Schottky dual-diode chips are presented, which is considered as a unit in the doubler design. The doubler features four Schottky anodes closely located at a compact region, being no need for additional power dividing and combining circuit. The purpose is to verify the feasibility of a simple and compact hybrid microwave integrated circuit (HMIC) circuitry for frequency doubling with a higher power-handling capability in this band, and an effective fast method for designing the matching networks of the doubler. With an input driving power of about 20 dBm at the E-band and bias voltage of 0 V, it delivers an output power of 6 ± 1 dBm across the band of 140–152 GHz and 2–4.7 dBm over the bands of 152–160 and 135–140 GHz.

A 3D printed microfluidically-controlled metal-coated waveguide single-pole double-throw (SPDT) switch is presented, which is both light weight and has low power consumption, exhibiting good performance at K-band. Oil (ON state) and EGaIn metal (OFF state) liquids are used for switching control. The proposed switch exhibits its best performance at 18 GHz, with insertion loss below 0.2 dB, return loss of 19.5 dB, and isolation better than 25 dB.

A dual-mode dual-band microstrip bandpass filter using the hybrid structure resonator derived from microstrip patch is proposed. Microstrip rectangular rings are used to excite the TE₂₀₀ mode and TE₀₀₂ mode of microstrip patch resonator, forming the high-frequency passband while it also works as a resonator which provides the low-frequency passband. The designed filter has 11 transmission zeros, resulting in good selectivity and good out-band rejection, extending the stopband, with a size of 0.45λ _g × 0.41λ _g. The measured results are in a good agreement with simulated results.

A hybrid full-wave and circuit model for spark gaps was constructed. The spark channel was modelled as a non-linear time-dependent resistor based on Rompe–Weizel's spark formula in SPICE. The linear full-wave model of an air gap and other structures were simulated by the semi-implicit finite-difference time-domain scheme based on the Newmark-beta method. These two models were coupled and simultaneously solved in time domain. The coupled model was tested for different charged voltages and spark lengths, and also validated in comparison with measurements.

A substantial reduction of substrate integrated waveguide (SIW) insertion loss can be achieved through the use of air as dielectric instead of usual dielectric material. However, air-filled SIW (AFSIW) circuits exhibit larger footprint compared with their dielectric-filled counterparts. A compact multilayer AFSIW bandpass filter is proposed to realise both high-performance and small footprint. For demonstration purpose, a Ka-band multilayer fourth-order AFSIW bandpass filter has been designed and fabricated. Measured and simulated results are in good agreement. Retro-simulations, taking into account fabrication tolerances, are also presented. Finally, a performance comparison with other multilayer technologies is presented.

A W-band waveguide bandpass filter, based on coupled TM₁₂₀ resonators, fabricated using CNC milling, is presented. TM₁₂₀ resonators are superior to conventional TE₁₀₁ resonators, in terms of having a larger size and reduced aspect ratio, which facilitates the fabrication process as well as allowing larger tolerances in the milling process. This type of resonator also offers a high unloaded quality factor, and ultimately yields a small insertion loss for the filter. A W-band filter, with a centre frequency of 100 GHz and a fractional bandwidth of 6%, is designed using four TM₁₂₀ resonators and constructed from three brass shims which directly fit to the waveguide flanges. This filter is measured to have a median passband insertion loss of 0.5 dB and a return loss better than 13 dB across the whole passband.

A novel wideband waveguide-to-microstrip transition realised by inserting asymmetric fin line probe into metallic rectangular waveguide is presented. One back-to-back transition covering the Ka band is designed, fabricated and tested to show the advantages of such asymmetric fin line-probe inspired transition structure, and measured results consist well with simulations. An insertion loss less than 0.8 dB and a return loss better than 15 dB over 24–40 GHz are obtained for the back-to-back structure. This broadband fin line-probe transition between rectangular waveguide and microstrip can be used widely in microwave and millimetre-wave circuit and system.

A compact 12-channel 480 Gbit/s optical receiver analogue front-end (AFE) for parallel optical transmission systems has been implemented in 0.13 μm SiGe BiCMOS technology. The transimpedance amplifier of AFE employed common-gate amplifier and negative feedback structure to decrease input impedance and broaden bandwidth. The limiting amplifier adopted modified Cherry–Hooper amplifier with active feedback technique to stabilise current and acquire high gain simultaneously. Without on-chip spiral inductors, the spacing of adjacent channels is constricted to 250 μm and the chip area is only 3350 × 700 μm. With the psuedo-random binary sequence (PRBS) input data, the maximum operating rate of the AFE is 38.7 Gbit/s; meanwhile, the root mean square (RMS) jitter is 2.16 ps and the single-ended output amplitude of 183.7 mV is achieved. The power consumption of each channel is 150 mW from a 3.3 V supply.

A 100-Gbit/s PAM-4 (pulse amplitude modulation) transmission over 4-km standard single-mode fibre (SSMF) and a C-band 4 × 80-Gbit/s PAM-4 transmission over 8-km standard SSMF experimentally demonstrated. A digital Wiener filter (WF) at the receiver side is utilised to compensate the impairments introduced by the transmission link. Bit error rate below 7% forward error correction threshold (3.8 × 10⁻³) is achieved with received optical power of 0 dBm for the single lane 100-Gbit/s transmission and around −4 dBm for the four channels after 8-km transmission with WF, which is over one order of magnitude better than that without equalisation. The results indicate that WF is a good enough option for practical application in short reach optical interconnect.

To manage thousands of battery cells effectively, a reconfigurable battery system has emerged where each battery cell is equipped with a set of switches for controlling connectivity (i.e. series, parallel, bypass or combinations thereof). While most studies have focused on maximising operation-time or life-time of a reconfigurable battery system, few studies have addressed how to quickly balance voltage of cells, which affects both efficiency and safety of a battery system. A new discharge scheduling policy for battery cell voltage balancing for a reconfigurable battery system is proposed. Based on the analysis why existing naive approaches are not effective for voltage balancing, a new approach consisting of three steps is designed: determination of a set of battery cells to be discharged, calculation of a target voltage, and distribution of the system load to each battery. The present simulation results show that the proposed approach outperforms three alternative ones up to 45.6% in terms of voltage balancing.

Induction heating appliances use control algorithms to regulate the power delivered to the vessel in a wide range [50 W–3.5 kW]. Switching frequency is commonly used to control the delivered power, hence an accurate identification of the power–frequency function would be useful, especially in multiple-output power converters. However, this function exhibits a severe variability due to temperature or vessel-inductor geometrical alignment, what reduces the performance of the open-loop control strategies. A method is presented to estimate the power–frequency function in just half a period of the utility voltage. The method packs several switching frequencies in the short identification period. The load is modelled as an equivalent series resistance–inductance, where both parameters vary linearly with respect to the switching frequency. The method is able to safely estimate the function using only switching frequencies well above resonance, but crucially, it is able to extrapolate accurately the delivered power levels even close to resonance.

A new feature named ‘2D comb’ to improve ship classification is proposed. The proposed feature presents added value to distinguish between container ship, tank ship and cargo ship. It is based on radar cross-section (RCS) statistic of the ship target related to the ship structure. Besides, related local RCS is proposed to classify three kinds of ships. Experimental results based on TerraSAR-X images show that the proposed feature can abstract and describe the ship structure in high-resolution synthetic aperture radar (SAR) imagery. It establishes relationship between RCS and ship structure, which is very useful to distinguish different kinds of ships.

A novel and effective speech enhancement method is proposed for suppressing the white noise as well as non-stationary acoustic noises. The proposed method employs the combination of variational mode decomposition (VMD) and empirical mode decomposition (EMD) methods. In this method, first EMD is used to decompose the noisy speech signal into intrinsic mode functions (IMFs). Further, the VMD is applied on summation of selected IMFs. The main contribution of the proposed method is the selection of IMFs based on Hurst exponent and further applying steps of VMD method. The proposed modified EMD-VMD (mEMD-VMD) method is suitable to reduce the low-frequency noise as well as high-frequency noise. The proposed method gives the better results in terms of speech quality and composite measures. The proposed study is performed on eight speech signals under additive white Gaussian noise, street noise, babble noise, and airport noise taken from NOIZEUS database.

This Letter presents a RFID-based sensor system targeting internet of everything (IOE) application. The system consists of a sensor tag with time-domain sensor interface and a software defined radio receiver as the reader. In the proposed tag, a dual slope modulation (DSM) sensor interface combined with UWB transmitter (TX) is used to convert and transmit the sensing information in time domain. The sensor interface employs the DSM to reduce the output deviation caused by process variations. Moreover, the approach removes the need of time-to-digital converter (TDC) on tag and only three pulses are sent for each sample, resulting in significant power saving. On the reader side, the UWB pulses are detected and the intervals corresponding to the input signal are measured by a TDC. The UWB TX and DSM block of sensor tag is implemented in 0.18 μm CMOS process and FPGA, respectively. The system demonstrates 8-bit ENOB at 98 kS/s sampling rate. The mean percentage error of output results is less than ±0.5% under ±10% process variation. The power consumption of the tag is 127 μW with an figures of merit (FoM) of 5 pJ/conv.step, which is suitable for wirelessly powered IOE application.

A reconfigurable bandpass time-interleaved sigma–delta modulator to achieve a wide tuning range is presented. With the calculated control parameters, the interleaving mismatch tones can always be shifted out of the interesting band during the whole tuning range, allowing always a mismatch-free implementation. The proposed method adopts a look-up table to obtain the various parameters including path numbers, path sampling frequencies, and tuning coefficients. With higher levels of reconfigurability the design meets the requirements of a multiband receiver for software defined radio systems, and the technique verified by behavioural simulations that also confirm the performance.

A novel differential substrate integrated waveguide bandpass filter is proposed. The TE₁₀₂-mode cavities arranged on the symmetrical plane could efficiently reduce the common-mode (CM) signal, meanwhile, transmitting the differential-mode signal. Additional transmission zeros have been obtained by using cross coupling in the dual-mode cavities. Moreover, by symmetrically etching complementary split-ring resonators on the bottom layer of the substrate, the CM could be suppressed whereas differential signals are not affected. To verify the above design concept, a prototype operating at 8.07 GHz has been realised and shows the desired filtering performance.

This Letter presents a methodology, which contains resistive-reactive series of continuous inverse modes (Res.-Rea. SCIMs), for the second octave power amplifier (PA) design. The bandwidth was extended by multiplying the current waveform of SCIMs with a cosine factor. The measurement of the proposed Res.-Rea. SCIMs PA showed 67–78.8% drain efficiency and ∼10 W output power across a band of 0.5–2 GHz.