A compact, wideband and high gain anisotropic rectangular dielectric resonator antenna is reported. This antenna consists of a multilayer dielectric structure which emulates uniaxial anisotropy and a relatively tall feed probe that acts both as a perfect electric conductor symmetry plane and the excitation of the higher order radiating mode. The multilayer structure and the tall feed probe are responsible for producing wide impedance bandwidth and size reduction, respectively. Measured results indicate that more than 50% size reduction is achieved without complicating the dielectric resonator antennas structure. Moreover, a wide impedance bandwidth of 19.4% along with a maximum gain of 8.1 dB is measured.

An antipodal Vivaldi antenna is presented that can be switched between an UWB mode and a tuneable very narrowband mode where the 3.3–10.6 GHz band can be covered by 30 different sub-bands. To achieve this high-frequency resolution, a gap is inserted in the Vivaldi feedline and a split-ring-resonator (SRR) is disposed close to it to serve as a coupling-bridge. By doing so, only frequencies whose quarter-wavelengths correspond to the SRR electrical length get coupled, before being coupled again to the other side of the feedline causing thus the antenna operation. Moreover, by capacitively loading the SRR and varying the load, the frequencies that can bridge the gap are varied, which allows tuning the antenna operating band. Now, to be able to efficiently cover the whole UWB, two SRRs of different sizes are alternatively used. Each SRR can be deactivated by disrupting its structure by means of switches. Finally, to operate the antenna in the UWB mode, the two SRR's are deactivated and the gap in the feedline is closed by means of a switch. To present the Letter, simulated and measured results are presented and discussed.

Possessing outstanding miniaturisation potentialities and ability to produce strong electromagnetic resonance, split-ring resonators (SRRs) are used to design an electrically small antenna (ESA). Here, a triple-band ESA is constructed by integrating three different sized in-plane SRRs. The resonant frequencies of these SRRs are tuned to be nearly equal. Shifting these SRRs to be non-concentric, as a way to decrease the mutual interaction between them, a broadband ESA can be achieved by simply adding up the three SRRs’ respective impedance bandwidth. Numerical and experimental results for the ESA of 0.129λ ₀ × 0.129λ ₀ are presented. The relative bandwidth of the ESA fabricated in experiment is 7.21%, a number approximately three times than that of the usual single SRR-based ESA.

A novel robust adaptive beamforming technique is proposed to solve the problem of performance degradation with one single snapshot. A sparse signal recovery model under the non-convex optimisation framework is first established, which dispenses with the mismatched sample covariance matrix, an indispensable part of most existing beamformers. Then, an iterative algorithm is designed to solve the optimisation problem by using the p-shrinkage operator and the alternating direction method of multipliers. The iteration steps are closed form and convenient to apply in practice. Simulation results demonstrate the effectiveness and robustness of the proposed algorithm.

The front-end amplifier (FEA) for neural signal applications forms the critical element for signal detection and pre-processing, which determines not only the fidelity of the biosignal, but also impacts power consumption and detector size. A back-gate current neutralisation feedback technique is proposed to compensate for input leakage currents generated by low-noise amplifiers alongside signal leakage into the input bias network when in integrated circuit (IC) form. Significantly, this topology ensures the FEA maintains a high-input impedance across the wide range of manufacturing and operational variations seen in ICs.

A new electrocardiogram (ECG) compression method based on the combination of the empirical mode decomposition (EMD) and the wavelet transform is presented. ECG signal can be decomposed into a set of intrinsic mode functions by the EMD. The proposed method recomposes the intrinsic mode functions into two groups, and compresses each group separately to fully utilise their data characteristics. The first group can be completely described by its extrema with negligible reconstruction error, while the second group is further decomposed by wavelet transform. With appropriate threshold selecting and the using of the run length coding and the Huffman coding, the proposed method exhibits competitive performances compared with other compressors for ECG compression.

A compact size and low-power multi-bit energy discriminator circuit is presented for X-ray spectrometry CMOS photon-counting detector (PCD) pixels. Because the circuit design is based on an asynchronous linear search, the discriminator with only a single-comparator classifies a sporadically incoming photon into multiple energy-bins, resulting in high spatial resolution and functionality of material-selective imaging. The proposed pixel power required to perform a minimal linear search is significantly less than the power of a conventional parallel search implemented in a flash-type discriminator. A prototype is fabricated in a 130-nm CMOS, and a 3-bit discriminator occupies only 23 × 60 μm². The circuit dissipates a static power of 1 μW with a power supply of 3.3 V (analogue) and 1.2 V (digital). The inaccuracy of energy-binning is measured to be 2.6–3.3 mV rms.

A novel complex-pole switched-capacitor lowpass filter topology is presented. The proposed scheme features sharper roll-off in the frequency response and reduced in-band loss compared with a real-pole filter. It provides higher stop-band rejection for the same bandwidth. Hence, the required filter order and chip area are reduced. These improvements are achieved without adding more active blocks to the real-pole filter, and with minimal added complexity. The proposed filter has the same low-output thermal noise level as the real-pole filter. These features, combined with a wide-frequency tuning range, make the filter suitable for high-speed, low-noise, and low-power applications. A fourth-order 200 MS/s filter prototype was designed in 0.18 µm Asahi Kasei Microdevices Corporation CMOS technology. Simulations verify that the average in-band loss is reduced by 3.2 dB compared with the real-pole filter. The 3 dB cut-off frequency can be tuned from 470 kHz to 17.5 MHz with 100 dB maximum stop-band rejection.

Asynchronous NULL convention logic (NCL) circuits are dual-rail quasi-delay-insensitive circuits that have many applications in high radiation and extreme temperature fluctuation environments such as space exploration. Two abstraction techniques are proposed that can be used to drastically improve the efficiency and scalability of formal equivalence verification targeted at NCL circuits. The effectiveness of the abstraction techniques have been demonstrated using a number of multiply and accumulate circuit benchmarks.

A multichannel bandwidth-interleaved (BI) framework with digital back-end correction of mismatch errors is explored to simultaneously increase the sample-rate and bandwidth of the ADCs. In addition to the consideration of channel frequency-response mismatch and aliasing error associated with sampling, the autocorrelation matrix of magnitude response is introduced to evaluate the performance of overlapping cancellation between the nearby subbands. Simulation results and analytical calculations are provided to verify the efficacy of the proposed correction approach.

A novel dithering-based calibration technique to correct capacitor mismatch in digital-to-analogue converter (DAC) used in successive approximation register analogue-to-digital converters is proposed. With dithering, weights of most significant bit capacitors can be measured accurately, which relaxes matching requirement in capacitive DAC. In addition, the bypass window technique is used to detect whether the output voltage of the DAC is within a predefined small window, which determines whether to inject the dithering signal. As a result, the proposed calibration can operate in the background. According to the simulation, the proposed calibration technique significantly improves capacitor matching without resorting to extensive computation or dedicated circuits.

A novel sensorless control for switched reluctance motor based on gradient of phase inductance is presented. In this method, current chopped control is adopted during the un-energised period. For chopping at currents near zero, continuous monitoring of phase inductance is possible. This proposed method uses the change of the gradient of the phase inductance to detect the un-aligned position. Experimental results demonstrate the validity of the proposed method.

An all printed actively actuated thermochromic (TC) smart fabric device is reported for the first time using a state of the art dispenser printing technique. The device consists of an ultraviolet curable TC ink with an activation temperature of 33°C actuated by conductive track-based printed heater. The device is printed on untreated polyester cotton fabric. It offers a significant improvement in flexibility and design freedom over the state of the art TC fabric devices. The printed device changes colour from black to green in 10.8 s using 1.46 W DC power. It is shown that the time required for the device to change colour reduces tenfold with only a threefold increase in input power. It can be fabricated on other fabric or flexible substrates and in a range of colours and activation temperatures depending on the formulation chosen. The printed device is 30 × 21.5 mm which can be scaled up or down to suit the application. It can be used as an indicator in combination with sensors for smart fabric applications.

A unified awareness-based cosegmentation model is presented. In contrast with existing cosegmentation methods, awareness information is introduced as a global constraint in a combinatorial auction-style energy model. The approach consists of an awareness-based segmentation model followed by a ‘structural forest’ optimisation framework and this approach aims to take full advantage of awareness prior in both the initial process and segmentation process. Experimental results show that it is comparable with the state-of-the-art methods. Furthermore, it opens interesting perspectives to fuse awareness and structural constraints in an unsupervised manner.

The image fusion plays a crucial role in many fields such as remote sensing, medical and robotics applications. In this Letter, a novel Hilbert vibration decomposition (HVD) based image fusion scheme is proposed. The HVD decomposes the source images into instantaneous amplitude and frequency components with decreasing energy values. Amplitude components of the first and second signals in the decomposition of the source images are used to generate the fused images using appropriate fusion rule. Performance evaluation of fused images is done by computing fusion quality metrics and the fusion results are compared with other existing fusion schemes. It is seen that the performance of the proposed scheme is better as compared with the existing fusion schemes.

An approach for clustering multivariate time series (MTS) is presented in cases of variable length, noisy data or mix of different type variables. First the covariance matrices are estimated which is used as a feature to represent the MTS, then project the covariance matrices from a Riemannian manifold into a tangent space and finally carry out the clustering based on a distance matrix. In this procedure, a geodesic-based distance is also introduced for measuring the similarity between the MTS samples. The proposed approach on a chaotic MTS with known clustering structure, namely Lorenz system is evaluated.

A new humidity sensor based on graphene oxide quantum dots (GOQDs)/polyelectrolyte [polymer (diallylimethyammonium chloride) (PDDA)] composite sensing films was proposed. A few layers of GOQDs anchor on PDDA were prepared on the substrate via covalent bonds. A 0D scale, hydrophilicity, and super-permeation of GOQDs endow the sensor an ultrafast response with about 32 ms response time and 48 ms recovery time. Meanwhile, the response was hardly affected due to covalent anchor of the composite film even after the sensor was soaked in water for several times.

A 5-bit digital controlled switch-type passive phase shifter realised in a 40 nm digital CMOS technology without ultra-thick metals for the 60 GHz Industrial, Scientific and Medical (ISM) band is presented. A patterned shielding with electromagnetic bandgap structure and a stacked metals method to increase the on-chip inductor quality factor are proposed. To reduce the insertion loss from the transistors, the transistor switches are implemented with a body–source connection. For all 32 states, the minimum phase error is 1.5°, and the maximum phase error is 6.8°. The measured insertion loss is −20.9 ± 1 dB including pad loss at 60 GHz and the return loss is >10 dB over 57–64 GHz. The total chip size is 0.24 mm² with 0 mW DC power consumption.

This Letter presents a compact microstrip diplexer. The high-frequency signal path is constructed by two electrically-coupling half-wavelength resonators, its external coupling adopts the tapped line structure. The low-frequency signal path is formed by two magnetically-coupling quarter-wavelength resonators, its external coupling is accomplished by microstrip coupling lines, which are formed from the tapped line structure and resonator of the high-frequency signal paths. The novel combination of the two signal path removes the need of T-junction in conventional diplexers. Meantime, the coupling strength of the two pass bands at the input port can be separately designed. A diplexer with Chebyshev frequency response at both signal paths with the central frequencies of 1.8/2.4 GHz is designed, fabricated and measured. The measured results give a good agreement with the simulated ones, which verifies the effectiveness of the diplexer.

A novel dual-wideband bandpass filter (BPF) using shorted stepped-impedance stub-loaded lowpass filter is proposed. The stub introduces two transmission zeros (TZs) to divide the low passband into dual-passband. By tuning the stub dimension parameters to control the TZs, the centre frequency and bandwidth (BW) for each passband can be tuned flexibly, and wide upper stopband can be realised. For demonstration, a dual-wideband BPF operating at 1.08 and 3.05 GHz is designed, fabricated, and measured, and its 3 dB fractional BWs are 103.2 and 48.5%, respectively. The measured results are in good agreement with the simulated ones.

A novel multilayered wideband microwave absorber based on lossy Sierpinski carpet array has been proposed. The absorber consists of four layers of Sierpinski carpet arrays composed of lossy materials with varying conductivities. The absorber has −10 dB absorption bandwidth of more than two octaves for normally incident wave and p-polarised obliquely incident wave, from 6 to 40 GHz. The thickness of the absorber is 7.2 mm. The structure does not contain any lumped elements and hence can be realised using 3D printing technology.

Implementation of a five-input majority gate, full adder, and full subtractor using multiple layers in nanomagnetic logic is proposed. Correct functionality of the designs was verified through the use of a special purpose Verilog library.

A novel method to fabricate microchannels into fused silica capillaries and hollow fibres by a high-voltage high-frequency corona discharge induced by a Tesla coil is demonstrated. Channels as narrow as 2.2 μm are successfully made in capillaries with 2 μm inner and 125 µm outer diameters.

In visible light communication (VLC), on–off keying (OOK) is able to achieve the best BER performance as compared with variable pulse position modulation. However, OOK has a significant defect that the dimming levels (i.e. brightness) of illumination are greatly affected by the input ratio of 0 and 1 bits. To overcome this drawback, OOK with run length limited (RLL) line codes such as Manchester code or 8B10B block code has been studied in IEEE 802.15.7 VLC standard. However, those mechanisms cannot support the dimming levels more than 50%. Also, spectral efficiency of those mechanisms is reduced and then it is causative of BER performance degradation. An effective RLL line coding scheme is proposed in order to enhance the brightness and BER performance as compared with conventional RLL coding schemes. The simulation results demonstrate that the proposed coding scheme is superior to Manchester code and 8B10B block code in terms of the brightness and BER performance.

200G/400G systems based on 16QAM and 8QAM are studied over three China Telecom links with different distances and span lengths. Ultra-low loss and ultra-low loss + large Aeff fibres were shown to support high-order modulation with sufficient industrial margin.

The first practical demonstration of readily useable fibre Bragg gratings in long lengths (>20 m) of polymer optical fibres (POFs) is reported; this is an increase in fibre length that exceeds two orders of magnitude for use in the C-band. A low loss perfluorinated fibre and a femtosecond-laser, direct-write method to inscribe gratings at two different wavelengths are used. Gratings are fabricated to operate at ∼800 nm, where the optical loss is minimal, and in the C-band, commonly used with traditional optical fibres for the majority of telecommunication applications. The development of POF Bragg gratings inscribed in long fibre lengths is the first important step for the integration of practical sensing devices and could promote the use of multiplexed POF sensors. The sensors were tested and characterised and demonstrate their compatibility with a commercial Bragg grating demodulator.

An undoped GaSb epitaxial layer has been grown on a GaAs substrate by molecular beam epitaxy. It has been found that GaSb could be a potential surface terahertz (THz) emitter photoexcited by 1.55 μm femtosecond laser pulses since the maximum optical-to-THz power conversion efficiency is at around this wavelength. The THz field strength is 10 dB weaker as compared with that generated from narrow-gap InAs at these energies of quanta. Furthermore, the samples were exposed to a constant magnetic field which enhances THz emission and allows signal registration in the line-of-sight geometry.

A method to control the frequency of a self-sustained push-pull converter at megahertz (MHz) level is proposed by utilising the parasitic capacitances of the circuit. As the equivalent parasitic capacitance and the frequency of the converter can be controlled by a DC voltage, the converter works as a voltage-controlled oscillator and a phase locked loop (PLL) controller is developed to lock in the zero-voltage switching frequency under circuit parameter variations such as the load, the coupling coefficient etc. The effect of the parasitic capacitances on the operating frequency and why the DC voltage can control it are analysed in details with equivalent circuit analysis and simulation study. Practical experiments demonstrate that the PLL controller can lock the operating frequency within 20–30 MHz with relatively good waveforms.

The Iridium L band downlink signals from a radar viewpoint are studied. The signal is modelled and its ambiguity function is analysed and the ambiguity function with that of the real recorded signal is compared. It is shown that the spectrum and ambiguity diagram of the Iridium signal are independent of the signal content, making it a very suitable signal of opportunity for passive radar. The interference floor of the ambiguity function of a single Iridium burst with a length of 8.28 ms is about 22 dB lower than the main peak.

Optimal solutions for multiple gyros configurations based on fault detection and isolation (FDI) and guidance, navigation and control (GNC) performance are confirmed analytically. To derive the solutions, a modified index for FDI performance of multiple gyros is presented and applied. The result shows that the analytic optimal solution of the configuration improves FDI performance while the optimal GNC performance is satisfied. The same result is also confirmed by experiments using 3D-printed sensor frames.

To measure vital signs using Doppler radar, a common approach involves the use of time-varying echo phase. To acquire these measurements, clutter rejection is necessary because clutter power is often larger than echo power. To reject static clutter, several techniques have been proposed that assume relatively large phase rotation angles because many studies assume the measurement of the upper torso, where displacement is mainly caused by respiration. However, signals from other parts of the human body are known to have smaller displacements that exhibit small phase rotation angles, which make clutter rejection more difficult. Three clutter rejection techniques for measuring small displacements are compared and their performances are investigated. Using numerical analysis, one method is demonstrated to be the most effective, even for small displacements in noisy data. The best method successfully estimates the centre with an error of −13.4 and −24.0 dB, with a signal-to-noise ratio of 10 and 40 dB and the range of phase rotation angles of 90° and 15°.

The extended target detection problem for OFDM cognitive radar is considered. A subcarrier-modulation method is proposed to improve the detection performance under peak-to-average power ratio (PAPR) constraint. The optimised weights are designed by semi-definition relaxation followed with Gaussian randomisation. The simulation results show that the proposed method achieves great improvement in both signal-to-inference-plus-noise ratio and PAPR while striking a good balance between the two performances.

An electrostatic discharge (ESD) strengthening design of high-voltage (HV) n-channel laterally diffused metal–oxide semiconductor (nLDMOS) transistors combined with embedded-SCR anode islands is investigated. After a systematic layout implementation and analysis, the anti-ESD robustness [or secondary breakdown current (I _t2)] of drain pnp-arranged and SCR isolated-type DUTs were higher than 7-A (ESD reliability improvements of these nLDMOS-SCR devices were more than 282.5% (199.2%) higher than that of the pure nLDMOS (pnp-stripe) component. Also, it can be found that the ESD robustness of the pnp-arranged type is greater than the npn-arrangement. Therefore, an adequate architecture of an HV nLDMOS device embedded with an SCR (pnp-arranged) and SCR isolated manner can gain high ESD-reliability immunity.

A new reconfigurable field-effect transistor (RFET) named as recessed-channel RFET (RC-RFET) is introduced herein to improve scalability, current drivability and subthreshold swing (S). There are two distinct features which allow RC-RFET to show enhanced performance than conventional RFET. First, a novel structure based RC and stacked gates increases effective channel length which results in suppressed short-channel-effect without any integration density penalty. Second, the switching mechanism of RC-RFET (thermionic emission) differs from that of conventional RFET (Schottky barrier tunnelling). It enables RC-RFET to overcome the fundamental limit of S degradation as a function of gate voltage and promises higher ON–OFF current ratio (I _ON/I _OFF) and its low-power applications. As a result, the RC-RFET shows I _ON/I _OFF higher than 10⁷, small drain induced barrier lowering about 15 mV/V and ideal S (∼63 mV/decade) for 50 nm gate length.

A joint time allocation and energy beamforming method for the maximisation of the system energy efficiency (EE) in multi-user multi-cell wireless powered communication network (WPCN) with distributed massive multi-input multi-output (DM-MIMO) system is proposed. An iterative algorithm to solve the EE maximisation problem is proposed. The simulation results show that the proposed scheme can achieve a significant EE gain. Further, it reveals that the achievable sum capacity of the DM-MIMO is considerably higher than that of a conventional centralised massive multi-input multi-output system.

In a train monitoring system, the sensor data measured at the train wheel, near the axle needs to be transmitted to a receiver located within the passenger car. The condition of the wireless channel from the outside to the inside of the train is critical because there are several metal parts between the transmitter and receiver. In addition, the channel variation characteristics change according to the area in which the train is driven. Hence, analyses of the wireless channel conditions are important for the successful transmission of the sensed data. Here, the channel profiles are estimated based on the data measured during various driving scenarios. The channel variation statistics are characterised by a probability function with certain key wireless channel parameters. In all the scenarios, the extreme value distribution in the dB scale is well matched with the channel statistics. A practical research of a railroad wireless sensor network is presented in this Letter and it is expected to be the basis for further simulation studies.