A new kind of broadband dielectric resonator antenna with a lattice structure is presented. The top dielectric resonator broken up into a lattice structure is adopted to achieve a wide operating bandwidth in a compact size, which makes it suitable to be arrayed. A backed cavity based on substrate integrated waveguide technology is introduced to reduce the unwanted radiation from the surface wave. The antenna is excited through a slot feeding structure. Measured results show that the prototype can achieve an impedance bandwidth of 39% and a peak gain of 9.6 dBi.

A strategy for enhancing the common-mode (CM) suppression of a band-notched UWB closed-aperture antenna is proposed. The antenna circuit consists of a differentially coplanar-waveguide-fed hexagonal-aperture antenna and a pair of wave-trapping slotline resonators for producing a 5.5 GHz notch band. The enhancement of the CM suppression was achieved by setting the dimension of the aperture along the longitudinal direction (i.e. the direction parallel to the feedlines) small enough, so that the first resonant mode of the CM half-circuit of the aperture antenna can be pushed beyond the differential-mode (DM) UWB passband. A fabricated balanced band-notched UWB antenna was measured to have a 10 dB DM passband of 3–11.2 GHz with a notch band of 5.1–6.1 GHz. Good measured CM suppression was observed with a maximum return loss of 2.9 dB in the DM UWB passband.

If epidemic contact detection using smartphones can be done with sufficiently fine resolution in outdoor environments, so that those who were within the transmissible distance from an infected person may be identified as a potential infected is explored. The smartphone GPS, at least in its current capacity, is not useful to determine the coexistence within a couple meters that is critical for infectious disease transmission is shown. As an alternative, the usage of magnetometers is proposed, which enables the coexistence determination with the required precision, with much less energy consumption than GPS, and with an added bonus of indoor usability.

A method for implementing a hardware-efficient multi-channel digital sigma-delta modulator is presented for processing field sequential multiple inputs. Compared to a conventional one, which processes the inputs in a time-multiplexed manner without sharing integrator memory for the multiple sequential inputs, the proposed method significantly reduces the number of storage bits in the integrator memory by partially sharing the integrator memory for the inputs. Simulation results on modulator noise power spectral density and overall signal-to-noise ratio match well with those based on quantitative noise analysis.

A method for the implementation of the atan2 operator based on the coordinate rotation digital computer algorithm is described. In the proposal, the computation of the z-path takes advantage of the look-up table-based FPGA resources to reduce by between 17 and 25%, without performance deterioration, the overall area of the unrolled architecture.

A class AB one-stage fully differential amplifier is described. It includes adaptive biasing techniques to the conventional class A differential amplifier that improve linearity, gain-bandwidth product and slew rate, maintaining the same DC bias currents and supply voltage requirements. Boosting of dynamic currents for large input signals takes place at the output branches, without internal replication of these currents. This leads to a nearly 100% current efficiency. Measurement results for a 0.5 μm CMOS test chip prototype validate the proposal.

A planar U-shaped resonator for measuring relative permittivity of the liquid mediums is developed. To improve the sensitivity of the proposed sensor, gap sections, coupled lines and central ring resonators (RRs) are used to enhance electric fields interact with liquid under test (LUT). Further to increase the resonance sharpness, a tapered double-sided spiral split RR is presented. As the permittivity of the LUT is increased from 26 to 79, the measured resonance frequency of the described sensor is varied in the 166.4–287.5 MHz range. The developed sensor exhibits an improvement in sensitivity of about 45% compared with the other work.

The proposed method is a watermarking method for high-quality images that achieves high invisibility and good robustness using a curvelet domain. Recently, there has been a demand for a watermarking technique that does not impair image quality, as interest in high-quality images has increased. To meet this demand, the authors adopted a method of minimising the watermark-embedding energy by using the multi-directional decomposition technique, curvelet transformation. However, if a watermark is inserted into the curvelet domain with the watermarking technique of the conventional domains, it is distorted during the forward and inverse curvelet transform. To solve this problem, they designed a watermarking method by considering the characteristics of the curvelet filter. By minimising the watermark distortion caused by the curvelet transform, high robustness is achieved with small watermarking energy. The proposed method shows very good invisibility and is difficult to distinguish the original. In terms of robustness, the correlation value increased by >80% and BER decreased by >20% compared with previous methods.

A real-time scheme for detecting object entities in real-time among a set of objects contained in the same class category is proposed. Building a unified framework for real-time object entity detection system without an additional training process to distinguish the object entities while minimising the loss of accuracy is focused. The experimental results on a benchmark dataset demonstrate that the method shows outstanding precision performance while achieving state-of-the-art object detection speed.

Practical acquisition of compressed sensing measurements involves a finite-range finite-precision quantisation step. To solve the sparse recovery problem and handle the quantisation distortion, this Letter proposes a non-smooth graduated-non-convexity approach that follows a path of gradually improved solutions along a sequence of non-smooth non-convex optimisation problems that progressively promote quantisation consistency (QC) and sparsity. We consider two classes of multi-scale continuous approximation functions to depict intermediate QC degrees and sparsity-inducing strengths, respectively, and apply recent proximal splitting methods to solve the resulting subproblem at each refinement scale. The simulations demonstrate the convergence of intermediate solutions to a nearly optimal estimation, in terms of accuracy and support recovery.

Using forward-biased base–collector voltage (V _BC) in high-speed circuits is usually not attractive due to the performance degradation compared with biasing heterojunction bipolar transistors (HBTs) in the forward-active region. However, the use of ultra-low supply voltage in millimetre-wave circuits provides an interesting application scenario not only for demonstrating the potential of modern silicon germanium (SiGe) HBT technologies in implementing severely power-constrained wireless circuits on silicon but also for verifying the accuracy of compact models beyond standard characteristics typically measured by foundries. The results of a 96 GHz frequency tripler deliberately designed with a reduced supply voltage (0.5 V) in a 130 nm SiGe HBT technology are presented. With only 4.7 mW DC power consumption, this frequency tripler achieves a conversion loss of 3.8 dB, generating a 96 GHz output signal with only −10 dBm input signal at 32 GHz. The impact of transistor series resistances on the tripler performance is also analysed.

A fully integrated broadband E-band power amplifier (PA) is implemented in 28 nm CMOS process. To enhance the output power (P _OUT), an 8-way differential series-parallel power combiner is used together with the neutralised bootstrapped cascode amplifier topology. The unit PAs are realised by both NMOS and PMOS transistors, respectively, which cancel the amplitude-to-phase modulation (AM-PM) distortion due to non-linear gate-to-source capacitance (C _GS) of NMOS and PMOS transistors under large input voltage amplitude. The presented PA achieves a saturated output power (P _SAT) of 21.3 dBm with more than 18.5 GHz −3 dB small-signal bandwidth (BW_{−3 dB}).

A novel structure that can operate as an in-phase and out-of-phase power divider across 100% fractional bandwidth is presented. The proposed structure adopts two pairs of parallel-coupled lines to enable changing the operation from in-phase to out-of-phase while improving the return loss and isolation of a traditional Wilkinson power divider. Moreover, the device includes a stepped impedance T-junction for input port impedance matching. Changing the status of two terminals of one pair of coupled lines from open-ended to short-ended allows achieving changing the operation from in-phase to out-of-phase performance. Using a chip capacitor between the coupled lines enables realising the needed tight coupling without the need to have narrow gaps. A prototype is fabricated and measured. Simulated and measured results show more than 10 dB of return loss and more than 15 dB of isolation across the investigated band 1–3 GHz. In addition, the device provides <1° phase imbalance and 0.2 dB amplitude imbalance in the in-phase and out-of-phase states across the whole frequency band.

A filtering power divider (FPD) with high selectivity is presented. Initially, by elaborately introducing two different types of microstrip-to-slotline transition structures and a pair of dual-mode stub-loaded resonators, dual-mode bandpass response is attained in this design. Afterwards, the resistor R is utilised to achieve high in-band isolation between two output ports of the FPD. Moreover, four transmission zeros are generated outside the passband for high selectivity performance. To validate the feasibility of the new approach, a prototype FPD operating at 3.62 GHz (f ₀) is designed, fabricated and measured. Both simulated and measured results are provided in good agreement indicating that the proposed FPD exhibits a better than 20 dB isolation inside the passband and extended upper stopband up to 10 GHz.

A method aimed at dielectric parameters measurement of small samples using a coaxial re-entrant cavity is proposed. After introducing grooves in the cavity structure to suppress parasitic modes, the operating frequency range has been broadened to 0.6–13 GHz for only one cavity. Compared to the traditional structure, the working bandwidth has expanded to 344% of the original one. The cavity perturbation technique is applied to detect the complex permittivity. The proposed method features two advantages over existing techniques, high sensitivity and more convenience for placing the sample.

A multi-feed Ka-band sin-shape corrugation antipodal Fermi-linear tapered slot antenna subarray is presented. The proposed prototype consists of four antenna elements excited by multimode beamforming network as an efficient method to perform beamforming operation without any use of couplers and phase shifters. It is implemented using substrate integrated waveguide technology. The four-element subarray has a measured gain of 11.45–13.86 dB along with beam scanning range of 24° and a narrow beamwidth (11.85°–13.05°) over 29–36 GHz. The measured mutual coupling between the four antenna ports is better than – 20 dB over the frequency range 29–36 GHz. The proposed multibeam antenna can be implemented for applications related to target tracking and imaging systems.

In this Letter, a new design scheme for wideband balun bandpass filter (BPF) is presented originating from the conventional Marchand-type balun prototype. The designed balun BPF is basically composed of three microstrip lines on the top side of the substrate and two half-wavelength slotline resonators etched in the ground plane. A distinctive wideband performance is attained by utilising the broadside coupling between these microstrip lines and slotline resonators. For demonstration, one fabricated prototype balun BPF operating at 3.75 GHz shows a broad bandwidth of 93% with nice in-band balanced performance. Final results from simulation and experiment are both recorded in good agreement.

Canonical logic units (CLUs) are basic building blocks for complex all-optical logic operations, and multicast of CLUs can improve the computing capacity and operating flexibility. The authors thus propose and experimentally demonstrate all-optical reconfigurable multicast two-input CLUs (i.e. minterms) at 40 Gb/s by using four-wave mixing in a single highly non-linear fibre. Each type of CLUs with clear temporal waveform and wide eye opening is achieved in five parallel channels simultaneously. The extinction ratios are >10.3 dB, while the optical signal-to-noise ratios are >21 dB. Based on the demonstrated scheme, a method of realising simultaneous full set of two-input logic operations is proposed and discussed. The proposed scheme can be extended to higher data rates and transferred to on-chip platforms.

The breakdown and optical response of perimeter gated single-photon avalanche diodes fabricated in a standard 0.5 μm 2-poly 3-metal CMOS process is presented. These diodes prevent premature edge breakdown through the addition of a polysilicon gate. The fabricated devices feature varying size, shape (square, octagonal, and circular), and junction types (nwell-p⁺ and psub-nwell) with a perimeter gate located on top of the junction. Voltage applied to the gate modulates the electric field and its effect on the breakdown voltage and optical response is discussed. Experimental results are supported by physical device simulations where applicable.

Optical links in datacentres operate mainly in burst mode. The utilisation might be as low as 10%, i.e. most of the time the link is idle, but still consumes power. It would therefore be desirable to put these links into a low-power sleep mode during idle signal by reducing the bias, and to operate the electronics and laser only when data is actually being transmitted. The laser is typically implemented with vertical cavity surface-emitting lasers (VCSELs). VCSELs should not be biased below their threshold current as otherwise an extensive turn-on delay will be incurred. A significant wake-up time is still observed in VCSELs even if the bias is not reduced during idle and only logic zeros are transmitted. With reduced bias, an unacceptable wake-up time is observed. The authors present measured data and propose a high-amplitude wake-up pulse at the beginning of the data burst, to significantly speed up the wake-up time. Measurements show the effectiveness of this pulse.

High-power density is required in power conversion systems used in various applications, especially in electric vehicles. Driving the power devices with high frequency is one of the successful solutions to downsize a circuit's magnetic components, and hence an overall high-power density of the circuit can be realised. Therefore, GaN high electron mobility transistor (HEMT) is widely used in many applications, owing to its high-speed switching characteristics, low power losses, and high heat and radiation resistances. However, the high-speed switching of GaN HEMT comes with a drawback. For instance, in a full-bridge inverter configuration, high-speed turn-on of one device may cause a false turn-on of the complementary device. If a power device has encountered a false turn-on, the GaN HEMT devices will suffer from overcurrent, excessive heat and is eventually destructed due to the short circuit. This phenomenon can be tackled by modifying the circuit conditions. In this Letter, the theoretical analysis of a three-phase full-bridge inverter is developed to figure out the behaviour of the GaN HEMT gate voltage, which is the key-factor parameter causing a false turn-on. On the basis of the proposed theoretical analysis, the circuit conditions which minimise the gate voltage spike are derived.

The design of unimodular sequence train with low central and recurrent autocorrelation sidelobes is considered. The design problem is formulated as a minimisation of the integrated energy in central and recurrent autocorrelations with user-supplied weights and an iterative method is proposed for it. The proposed method is computationally efficient, as its main computation can be implemented using FFT. Numeric results are reported to validate the proposed method.

The beampattern of a conventional frequency diverse array (FDA) with linear frequency pattern (i.e. the centre frequency of each antenna element is linearly increasing) is coupled in range and angle. FDA with random frequency pattern can decouple the range and angle with high probability only when the number of elements is sufficiently large. The ambiguity of frequency patterns that are random permutations of a linear FDA is examined. An eigenvector-based criterion to identify possible ambiguity in target localisation using such arrays is proposed. Numerous results are presented to verify the effectiveness of the proposed ambiguity identification criterion.

Spectrally efficient FDM (SEFDM) was proposed as a spectrally efficient scheme. An iterative fast Fourier transform (FFT) detector jointly operating with a channel decoder was also proposed for coded SEFDM. Unfortunately, the iterative FFT detector requires relatively high complexity for some bandwidth compression factors. A new detection scheme for the coded SEFDM is proposed. In the proposed scheme, the inter-carrier interference is iteratively estimated and cancelled in frequency domain. The proposed scheme not only offers virtually identical performance but also requires less complexity compared with the iterative FFT detector.

Adaptation of sensing period for licensed channel is one of the key requirements to maximise the utilisation of transmission opportunities by a secondary user. A novel objective function evaluation method for sensing period optimisation in cognitive radio network is formulated. A recently introduced optimisation technique, namely Jaya algorithm has been used for achieving the optimum value of sensing period in order to maximise the discovery of spectrum opportunities while maintaining the sensing overhead and interference time within user defined value. This multiobjective optimisation problem involving different constraints is solved using an objective function that introduces penalty for violation of constraints. Results show that the proposed scheme leads to quick adaptation and efficient discovery of spectrum opportunities while satisfying the different QoS constraints, thus making it a better choice for real-time applications.