A triple band-notched UWB monopole antennas is presented for flexible electronics. To enhance the flexibility, ultra-thin liquid crystal polymer with 50 μm thickness is used as the substrate. The antennas are constituted by swallow tail radiation patch and trapezoid ground. Moreover, band-notched characteristic is realised by etching different sized elliptic single complementary split-ring resonators on the radiation patch. An improved triple band-notched UWB antenna with notched-frequency bands at 3.7–4.2 GHz, 5.15–5.35 GHz, and 5.725–5.825 GHz are designed by a novel capacitance compensation method. The measured radiation patterns indicate that the antennas are an omni-directional antenna both at flat and bent circumstances. The occupied area of antenna is 27 × 21 mm.

A tunable multiband folded printed quadrifilar helical antenna (FPQHA) is proposed. Creating slot on the arms of FPQHA is a simple approach for designing multiband helical antenna. Also varying width and length of the slot can cause to tune the interested frequency bands. The operating frequency ranges in L/S/C band that covers L1 GPS band and most of the commercial wireless communication systems, such as WLAN [IEEE 802.11 (2.4/3.6/5 GHz)], LTE and WiMAX (2.5/3.5 GHz).

Application of direct radiation pattern estimation in finite difference time domain (FDTD) simulation environment as an alternative to cumbersome near-to-far field transformation is considered. With the proposed improvement, direct estimation of the radiation pattern from the field strength samples in FDTD method becomes significantly less sensitive to the antenna geometry and thus more applicable to practically relevant cases. The main idea is to use field samples taken at two different radii to account for antenna geometry. The samples are taken at radii that are as close as possible to the antenna but still not too close to spoil the correctness of the results. The introduced improvement, combined with multigrid simulation domain and higher order accuracy FDTD formulations, reduces the necessary size of the computational domain, which directly leads to reduced memory consumption and a smaller error due to numerical dispersion.

A 2 × VDD output buffer using leakage current compensation is demonstrated. With the proposed leakage current compensation circuit, the SR (slew rate) is improved 36.4–101.89% based on on-silicon measurement results given different VDDIO (1.0/1.2/1.8 V) and temperatures (from 0 to 100°C). The data rate is 510/630/400 MHz for VDDIO at 1.8/1.2/1.0 V, respectively. Moreover, the reliability problem, the gate oxide overstress and the hot carrier degradation is avoided. The proposed design is implemented using a typical 90 nm CMOS process. The active area is 0.425 × 0.0563 mm. The SR is measured in the range from 0.766 to 2.585 V/ns.

A lock-detector for the digital phase interpolator based clock and dada recovery circuit (PI-CDR) is proposed. The simple method could commendably lock the PI-control code when the CDR is locked, which eliminates the systematic phase noise of the recovered clock without reducing the jitter tolerance ability. The proposed architecture is implemented in 0.13 μm CMOS and occupies area of 0.18 mm².

An energy-efficient switching scheme for successive approximation register (SAR) analogue-to-digital converter (ADC) is proposed. Based on closed-loop charge recycling method, the proposed switching scheme achieves 100% less switching energy over the conventional switching scheme. Furthermore, the common-mode voltage of the comparator is always V _cm and only two reference voltages are used.

A novel technique for detecting duty cycles of noisy arbitrary waveforms by employing artificial neural networks trained with empirical moments of asynchronously sampled waveforms’ amplitudes is presented. The proposed technique is software-based and hence can be applied flexibly to numerous waveform types without requiring any hardware changes. Furthermore, in contrast to existing duty-cycle detection methods, this technique is capable of detecting duty cycles of noisy waveforms. Results obtained for square and sawtooth waveforms demonstrate wide duty-cycle detection range of 10–95% with mean absolute percentage errors < 0.4%.

A low-cost two-step delay locked loop (DLL) with a 20–80% input duty cycle is presented. For eliminating harmonic and zero-trap locking issues along the whole range of digital controlled delay line, a hierarchy phase detector (HPD) is proposed to compare the phase difference between input reference clock and two phase-isotonic clocks generated by sharing a common delay line. By monitoring of HPD's output, state controller can solve harmonic and zero-trap locking issues while being naturally immune to the wide range of input duty cycle. With an asymmetric edge combiner, high duty cycle correction accuracy can be achieved. The proposed DLL is implemented in 55 nm CMOS technology with a 0.00574 mm² chip area. Simulation results show that the operation range of the proposed DLL is 0.3–1.6 GHz without the occurrence of harmonic and zero-trap locking, and the range of input duty cycle is 20–80%. The power consumption is 0.76 mW at 1.6 GHz.

The effect of a dielectric liquid on the tunability of capacitor operating in RF domains is evaluated. The RF measurement shows a high variation of the resonant frequency accompanied with a low insertion loss. Moreover, the fluid positions between electrodes modify the capacitance value up to Tr = 6660% at 600 MHz. The quality factor decreases in response of water filling from Q _max = 51.9 when it is empty to Q _min = 1.49 when it is fully filled. According to the finite-element method analysis, the change of the dielectric permittivity influences the capacitor performances. Essentially, the tuning range of the capacitance and the quality factor could reach, respectively: Tr = 7660% and Q _min = 35.

Zeroing dynamics (ZD), as a powerful method proposed for time-varying problems solving, has found successful applications in motion control of serial manipulators. Compared with serial manipulators, parallel manipulators possess some attractive advantages such as high carrying capacity and high operation accuracy. However, the inherent differences between parallel and serial manipulators set great difficulties on the applications of ZD to the control of parallel manipulators. Making progress along this direction, the first ZD based motion controller of parallel manipulators is proposed and the design procedure of the ZD based scheme is presented. As a typical application, the proposed scheme is utilised to control a Stewart platform for tracking a quatrefoil-shaped path, which illustrates the effectiveness of the ZD based scheme.

A Bouc–Wen model is presented and identified based on the bat-inspired algorithm to describe the hysteresis of the piezo-actuated stage. Based on the established Bouc–Wen model, a sliding mode controller is proposed to suppress the hysteresis non-linearity of the piezo-actuated stages. In order to solve the buffeting problem in the process of control, the sign function is replaced by the sigmoid function. Experiment is performed to validate the effectiveness of the proposed sliding mode controller, and the results show that the maximum error of the motion tracking control of the piezo-actuated stage is 0.3264 μm.

A 28 nm CMOS-bulk lowpass analogue filter architecture is hereby proposed. The filter is based on an improved Active-G_m -RC structure, where both poles of a Miller-compensated operational amplifier (OPAMP) have been used for synthesising a third-order filter. Several well-known issues related to the 28 nm process node have been hereby mitigated by proper circuit/design techniques, enabling large signal-to-noise ratio (SNR) and 13.5 dBm IIP3. The proposed circuital solution performs 59 dB-SNR at 340 µW power consumption from a single 0.9 V supply-voltage. This allows one of the higher figure-of-merit (156 dB) in sub-1 V analogue filters state of the art.

Binary descriptors have been shown to be computationally efficient while their recognition rate is poorer than that of floating-point descriptors. A method of improving both the recognition rate and the speed of computation for thresholded intensity rank descriptor, one of the binary descriptors is proposed. In experiments, our descriptor shows better performance than other binary descriptors in terms of both the recognition rate and the speed of computation.

Faster-than-Nyquist (FTN) signalling, as a bandwidth-efficient modulation format, attracts many researchers’ attention. However, the symbol rates of FTN signal are increasing when the packing ratios decreases. Moreover, the FTN signal with small packing ratios requires a high-rate analogue-to-digital converter. Since the bandwidth of FTN signal remains the same, the samples taken at Nyquist sampling rate do not suffer information loss. However, the variable packing ratios induce extra memory-consumption when the FTN signal is sampled at Nyquist sampling rate. To reduce the sampling rate and the memory-consumption, a new receiver of FTN signal with oversampling is proposed. Simulation results show that the receiver can perform close to the convolution code line. At the same time, the sampling rate and the memory-consumption can be reduced by adjusting the oversampling factors according to the packing ratios.

The performance of energy detection over κ − μ shadowed fading is analysed. The analysis is then extended to include the maximal ratio combining and square law combining schemes with non-identically distributed branches. Moreover, the analysis over κ − μ extreme shadowed fading channel, that is utilised to model the wireless communications scenarios in enclosed areas, is also investigated. To this end, exact closed-form expressions of the average area under the receiver operating characteristics curve are derived.

Frame error rate bound is a useful tool to predict the performance behaviour of coded faster than Nyquist system (FTN). In this Letter, the Euclidean distance distribution (EDD) of FTN signalling is assumed continuous and obeys the Gaussian distribution for its long memory length. By using the autocorrelation properties of the error sequences, the EDD of FTN is estimated and the simplified bound is further derived which indicates that the performance of coded FTN system is bounded by the performance of employed coding scheme. Simulation results show that the bound is well matched with the simulated performance in high SNR regime.

An extension of the generalised eigenvalue decomposition (GEVD) to polynomial matrices, that is, a polynomial GEVD is proposed. A method for its application to convolutive blind signal separation is then introduced. The author shows that the source signals can be estimated using two related, but different, ‘target’ polynomial matrices. These polynomial matrices are parahermitian matrices, corresponding to two different signal time intervals, which capture the non-stationarity of the sources. The validity of our method in separating the sources from their convolutive mixtures is demonstrated with computer simulations.

Digital predistortion has become an attractive technique for power amplifier linearisation whose limiting factor for using Volterra series as the underlying model is its computational complexity, since the number of components rapidly grows with the non-linear order and memory. Based on a previous reference algorithm, which consists on applying the orthogonal matching pursuit for the sorting of the model components and a Bayesian information criterion for the selection of the optimum number of components, a new technique to reduce the size of the support set taking into account the structural information within a model is presented. Experimental results of the predistortion of a commercial power amplifier are given as a proof of its capabilities, showing equivalent performance to the pruning with the reference algorithm while further reducing the number of components.

A fast detection system based on a terahertz quantum-well photodetector (QWP) and a fast modulated terahertz quantum-cascade laser is presented. Response waveforms and eye diagrams under different modulation frequencies are acquired. Employing the current measurement system without any high speed optimisation obtains the highest response rate of 0.5 GHz. The experiment demonstrates that the QWP is potentially useful for fast detection and high speed communication applications.

The modal properties of a novel vertical-external-cavity surface-emitting laser with (GaIn)As/Ga(AsSb)/(GaIn)As type-II quantum wells are analysed. The device, emitting at a wavelength around 1175 nm, is operated in TEM₀₀ mode and optimised for a high beam quality. The M ² factors are measured at various pump powers. An excellent beam quality is observed for up to 350 mW with an M ² < 1.2.

A novel chirped metal structure (CMS) is developed for polarimetric enhanced detection of both mid-wave (MW) (3–5 µm) and long-wave (LW) infrared (IR) wavelength bands (8–14 µm). The nano-scale structure consists of parallel sub-wavelength chirped-width stripes together with graded-width separating gaps. The CMS allows plasmonically enhanced polarisation-sensitive absorption of dual-bands simultaneously in underneath IR detection device. The finite-difference-time-domain method is utilised to numerically evaluate gold CMS structure on an IR detector. Simulations show an excellent performance with high plasmonic absorption enhancement and polarisation extinction-ratio over the continuous wavelength range 3–14 µm. The maximum recorded extinction-ratios are 2900:1 and 400:1 in the LW and MW bands, respectively. The maximum estimated plasmonic absorption enhancements for TM-polarisation in the LW and MW bands are 96 and 16%, respectively. The suppression of TE-polarisation absorption is almost 100% over both bands.

Polarisation independent silicon waveguide wavelength filter using Bragg grating with chirped period is reported. The polarisation rotation and filter peak with wide flat top response is obtained. An antisymmetric grating structure and rib waveguide is used. We experimentally obtained polarisation independent flat-top band-pass filter consisting of polarisation beam splitter (PBS) and Bragg grating.

Spectral profile control method of a dispersion-tuned fibre laser is demonstrated. A dispersion-tuned fibre laser is a fast and widely tunable wavelength-swept laser without mechanical tunable filters. The lasing centre wavelength is tuned by changing the active mode-locking modulation frequency to that of the corresponding operating wavelength matching the fundamental repetition rate of the cavity. The sweep spectra profile can be controlled by modulation frequency sweep. By applying a pre-calculated modulation frequency sweep, the flatness of the wavelength-swept spectral profile can be improved. We applied the dispersion-tuned wavelength-swept laser to a spectral-domain optical coherence tomography system as a wideband light source and successfully obtained OCT images. The image resolution is enhanced by applying a nonlinear modulation frequency sweep to the laser instead of linear modulation frequency sweep. The potential of the proposed dispersion-tuned wavelength-swept laser as a spectrally flexible laser source is demonstrated.

In this Letter, a novel 1200 V FS- insulated gate bipolar transistors (IGBT) is proposed to improve the trade-off between avalanche ruggedness and on-state voltage drop. The proposed IGBT features the high doping and thin n-layer under trench gates and we call it the electric field modulation layer (EFM layer). Under the avalanche condition, the EFM layer can form the sharp electric filed distribution in the EFM layer and the avalanche multiplication is constrained in the thin EFM layer. The difference between the holes and electrons due to the avalanche multiplication effect at the emitter side of the IGBT is minished. Therefore, the negative difference resistance in the avalanche I–V curve caused by the difference between the holes and electrons is eliminated. As a consequence, the avalanche ruggedness of the EFM-IGBT is improved. In the on-state, the high doping EFM layer can store the carriers and the on-state voltage drop of the EFM-IGBT is reduced to 1.48 V at 200 A/cm². Finally, the EFM-IGBT improves the trade-off between avalanche ruggedness and on-state voltage drop.

When the batteries of electrical vehicles are used to provide vehicle-to-grid (V2G) ancillary service, battery life is shortened due to additional battery usage. To consider battery degradation, cycle life-based approach with degradation density function (DDF) is popular. However, the previous modelling cannot capture the well-known fact that battery may severely degrade at both ends of battery, i.e. when full or empty. A novel method of obtaining DDF using the curve fitting over average degradation function is proposed. The proposed method tightly fits the empirical measurements and thus provides a better way of operating V2G considering battery degradation. The results show that the proposed method reduces battery degradation by up to 28.9% while achieving the same revenue.

A soft switching converter is presented with the advantages of wide zero-voltage switching range, low primary conduction loss, less output inductance and power transfer within the whole switching cycle. Half-bridge circuit is connected to the lagging-leg power switches of full-bridge converter to improve the soft switching load range. One positive rectified voltage is generated on the secondary side to reduce the primary current to zero during the freewheeling state. Therefore, the primary conduction loss is reduced. The performance of the proposed converter is verified by the experimental verifications with a 1.92 kW prototype.

Adding the Z-source inverter into wireless power transfer systems helps to offer more control strategies due to its extra state than the traditional inverter. However, the parameters of the system should be strictly designed, otherwise the system will malfunction. The malfunction issue and factor's causing it are described accordingly. Suggestions on the design parameters of the system are provided. To verify the analysis, simulation results of the proposed system are added.

A reconfigurable switched-capacitor DC–DC converter is presented for indoor photovoltaic energy harvesting. A uniform hysteresis controller regulates the PV cell voltage at 1.5 V to extract the maximum power from the PV cell and regulates the load voltage at 0.9 V. To minimise the conversion loss, the energy is transferred from the PV cell to the load directly whenever energy is available in the PV cell. When the load voltage is high, the excess energy in the PV cell is stored in the buffer of 1.8 V. The load draws energy from the buffer when energy is not available in the PV cell. The proposed converter was fabricated in 0.18 μm CMOS process and achieves peak efficiencies of 87, 88 and 78% while delivering energy from the PV cell to the load, from the PV cell to the buffer and from the buffer to the load, respectively.

A fast and interpolation-free algorithm for near-field cross-section imaging is presented. First a two-dimensional (2D) compensated non-uniform spatial spectrum in wavenumber domain is obtained by fast Fourier transform (FFT) and phase compensation. Then the non-uniform wavenumber grid is approximated to a newly constructed uniform grid which can be considered as perturbation basis. By doing first-order Taylor expansion, 2D inverse FFT can be performed on the perturbation basis to obtain the cross-section image. Experiment demonstrates the effectiveness and efficiency of the proposed method.

A computationally efficient direction-of-arrival (DOA) estimation algorithm for monostatic multiple-input multiple-output (MIMO) radar based on covariance matrix reconstruction is presented. By reduced-dimension transformation, the transformed covariance matrix is reconstructed in the Toeplitz structure and then the DOAs are estimated by employing MUSIC. The proposed reduced-complexity denosing covariance matrix reconstruction approach provides lower computational complexity compared with conventional two-dimension multiple signal classification (2D-MUSIC). Moreover, in contrast to the subspace-based methods, the proposed method can be carried out without knowing the number of targets. Simulation results demonstrate the outperformance of the proposed method.

The aim is to present a new direction-of-arrival (DOA) estimation algorithm, which is better suited for dealing with unknown non-uniform noise, as well as estimating more sources with less sensors. To achieve this goal, three key steps are exploited: a first step is to extend the array aperture by using coprime array and conjugate symmetry strategy, a second step is to avoid phase ambiguity via vector element reorganisation and a third step is to obtain a full-rank covariance matrix through subvector division, which has the same form with the covariance matrix obtained in uniform Gaussian white noise. Simulation results show that the proposed algorithm can provide better DOA estimation performance than the compared algorithms.

Sparse reconstruction has been recently proposed to overcome many challenges in radar imaging applications. In sparse reconstruction framework, the basis matrix of high-resolution radar image demonstrates high mutual coherence, which is inversely proportional to the quality of the reconstructed image. The high mutual coherence, also, weakens the noise immunity in the sparse reconstruction. A technique for building a basis matrix with low mutual coherence is proposed which preserves the high quality of the resultant radar image. The proposed technique groups the columns of the original basis matrix that share the same range of time delay into one column with the average time delay of the group. The resultant basis matrix is used in a sparse reconstruction algorithm to reconstruct the pixel values of a radar image. The technique was validated over realistic and simulated radar measurements and was shown to be computationally efficient with improved noise immunity.

The shift register of display panel employing double-gate oxide thin-film transistors (TFTs) to compensate the severe degradation of the threshold voltage (V _TH) is proposed. In double-gate TFTs, V _TH is controlled by adjusting top-gate bias, so that V _TH degradation can be stabilised by top-gate bias control. However, an optimum top-gate voltage varies from product to product due to process–voltage–temperature variation. To overcome this variation, a feedback system is designed and fabricated in a 0.18 μm BCDMOS process. The system consists of the shift register current sensing and the searching algorithm for finding optimal top-gate bias of double-gate TFTs. It is verified that proposed system successfully stabilised the operation of the shift register up to 80°C.

We investigated the stress-induced resistance drift and breakdown characteristics in MgAl₂O₄ (MAO)-based magnetic tunnel junctions (MTJs) with the MAO thickness of ∼0.9 nm. The occurrence of trap sites around the tunnel barrier–electrode interfaces was characterised via interval voltage stress (IVS) and constant voltage stress (CVS) experiments, in which the occurrence of trap sites affects the resistance drift in IVS and time-dependent dielectric breakdown in CVS. The observed resistance drift ratios were almost the same for positive and negative applied voltages, indicating that the difference in the interface structure was negligibly small between the top and bottom MAO/CoFe interfaces in the MAO-based MTJs. More interestingly, the resistance drift ratios were very low compared with the results of a previous study on MgO-based MTJs. MAO-based MTJs is likely to be an effective alternative that can be used to improve MTJ device reliability.

A formula for the optimal relation between the width of a planar conductor (w ₀), the total width of parallel straight planar conductors (W), and the number of the parallel conductors (N) for the minimum ohmic resistance is presented. The formula is verified for the frequency range between 2 and 27.12 MHz according to N by using the finite element method. By experimentation, it is also shown that the proposed formula can be applied to design low-loss circular planar coils.