The frequency selectivity of an array of triple cross elements fabricated using an additive manufacturing technique is assessed, to demonstrate the feasibility of using three-dimensional (3D) printing techniques in frequency selective structure production. The process is a candidate for the fabrication of frequency sensitive components in buildings, in situations where the electromagnetic architecture is an important consideration. As a simple symmetrical 3D element, the triple cross is part of a class of elements suitable for crystal-like configurations. The basic performance of the array is summarised through simulations and experimental results.

A compact triple-band coplanar waveguide (CPW)-fed antenna for WLAN/WiMAX applications is proposed. The radiation patch is fed by capacitive coupling of the top transmission line. By only using one metallic strip etched on the bottom of the substrate, tri-band resonances of the antenna are generated. The proposed antenna has a compact size of 30 × 27 mm², which can provide stable omnidirectional radiation patterns in three bands. The measured − 10 dB impedance bandwidths are 150 MHz (2.39–2.54 GHz), 360 MHz (3.37–3.73 GHz) and 1170 MHz (5.02–6.19 GHz), which is suitable for WLAN/WiMAX applications.

A double-slot structure is proposed to design a new Vivaldi antenna with improved gain. The two slots are excited in uniform amplitude and phase by using a T-junction power divider. The double-slot structure can generate plane-like waves across the slot aperture of the antenna. As a result, the gain of the double-slot Vivaldi antenna is significantly improved compared with that of a typical Vivaldi antenna of the same size. The measured results show that the impedance bandwidth of the double-slot Vivaldi antenna is from 2.5 to 15 GHz. The gain of the proposed antenna is considerably higher than the typical antenna at frequencies above 6 GHz. What is more, the structure proposed is far simpler than those designed before.

A miniaturised double-layer slit-patch structure is introduced for decoupling two closely spaced co-planar waveguide-fed printed monopoles with a common ground. The double-layer structure consists of a slit etched on the common ground between the antennas and a conducting dipole element printed on a very thin dielectric film separating the two layers. Simulated results of the antennas’ performance as well as measurements of fabricated prototypes are presented.

A magnetoencephalography (MEG) multivariate data exploratory analysis is described and implemented that combines the variance criterion used in principal component analysis with some prior knowledge about the sensory experimental task. By using the idea of rearranging the data matrix in classification pairs that correspond to the time-varying representation of either stable or stimulus phases of the specific task, the feature extraction method is constrained reducing significantly the number of principal components necessary to represent most of the total variance explained by the MEG signals.

A high-performance wide-V _DDH-range level converter (LC) is presented for mixed-signal systems. The proposed LC achieves a low power-delay product over a wide range of V _DDH with V _DDL in the near-threshold region. The proposed LC uses a feed-forward signal to pull down the output voltage at low V _DDH, without increasing the size of the nMOS diode for the pseudo-V _DDL. A comparison with conventional LCs shows that the proposed LC not only supports high V _DDH but is also robust at low V _DDH while exhibiting high performance.

A broadband low-noise amplifier (LNA) is proposed. The active g_m -boosting technique is utilised to reduce the common-gate (CG) LNA noise figure and improve gain. An implemented prototype using 0.13 μm CMOS technology is evaluated using on-wafer probing. S ₁₁ and S ₂₂ are below − 10 dB across 0.1–5 GHz. Measurements show a power gain of 18.3 dB with a − 3 dB bandwidth from 100 MHz to 2.1 GHz and an IIP3 of − 7 dBm at 2 GHz. The measured noise figure is better than 2.5 dB below 2.1 GHz, better than 4.5 dB below 5 GHz and at 500 MHz it obtains its minimum value 1.8 dB. The LNA consumes 14 mW from 1.5 V supply and occupies an area of 0.04 mm².

A robust and fully integrated solution to calibrate the voltage controlled oscillator frequency to the data rate frequency in a clock and data recovery is described. As such, no external reference frequency or a separate reference phase-locked loop is required. The proposed calibration circuit has been designed in a 130 nm CMOS technology. It shows a very low temperature dependency below 100 ppm °C⁻¹.

A simple circuit that actively compensates supply noise and reduces period jitter in CMOS clock buffers is presented. The locally sensed supply noise modulates a current injected in the buffer output node during transitions. By injecting the current in opposite phase to the supply noise, the transient variations are counterbalanced and the jitter removed. Designed in a 28 nm CMOS technology, a chain of 16 inverters using the proposed circuit shows a period jitter up to three times smaller than that of an equally long chain of basic inverters. Conventional local supply noise filtering would require approximately 70 times the area used by the proposed circuit to achieve similar performance.

Quaternary logic can be implemented using quantum dot gate-quantum dot channel field effect transistors (QDG-QDCFETs) which produce four states in their transfer characteristics. A circuit model is used to simulate a four-state state inverter which is the basic building block of any multi-valued logic (MVL) circuit design. A basic problem of MVL implementation is the noise margin. The stable nature of the transfer characteristics of the QDG-QDCFET can make them a promising circuit element in future MVL circuit design. Comparison of fabricated device characteristics and the model data is shown.

A new class of lowpass linear-phase FIR filter function given in an explicit compact form is introduced. First, the general form of a new class of nth-order difference equations with all real coefficients equals one is proposed, and after that the simple frequency sampling structure for any odd and even orders of the filter is designed. Finally, several simulation experiments have been performed in order to compare this filter with other known filters for the same values of free real integer parameters. It should be highlighted that the new filters compare favourably even with the already existing filters, because they have an insert attenuation of 158 dB, 15.1681% lower cutoff frequency of the passband of the filter, and 18.5313% lower cutoff frequency of the stopband of the filter, for an insert loss of 100 dB.

Based on the use of auxiliary differential equations, a unified split-step precise integration time-domain (SS-PITD) method is proposed for modelling wave propagation in linear dispersive media. The unification of this method is achieved by using a general expression to represent the Debye, Lorentz and Drude dielectric medium models. Moreover, due to the introduction of the SS scheme, the original two-dimensional (2D) or 3D electromagnetic problem reduces to a set of 1D sub-problems which can be efficiently solved by using the conventional PITD algorithm. It leads to a great reduction in the requirement of computation time and storage space. The proposed method is verified with a numerical example and compared with the finite-difference time-domain method.

A fast and efficient method [fast efficient blind (FEB)] for no-reference image quality assessment (IQA) is presented. Two new features, log-energy and variance, are proposed in the spatial domain, which make the IQA algorithm faster and more efficient. FEB obviates the training process of distortion images and subjective opinion scores due to the properties of the new features. The experiment shows that the proposed method outperforms conventional methods in terms of both accuracy and execution speed and is also consistent with the subjective assessment of human beings. Owing to the simplicity of the features proposed, FEB can realise real-time IQA completely.

A new algorithm for specularity detection using a single image, which is based on the maximally stable extremal regions (MSER) detector, is presented. This algorithm takes full advantage of the characteristics of specularity and requires no assumptions. For this reason, it separates specularities very well regardless of the illumination condition and the surface material. To illustrate the effectiveness of the prposed algorithm, experiments are performed using the images of both dielectric and metal surfaces. Experimental results show that the presented approach outperforms the traditional methods from the point of view of sensitivity to correctness.

A novel approach is proposed for automatic foreground extraction which aims to segment out all foreground objects from the background in the image. The segmentation problem is formulated as an iterative energy minimisation of the conditional random field (CRF), which can be efficiently optimised by graph-cuts. The energy minimisation is initialised and modulated by a soft location map predicted by a discriminative classifier which is learned on-the-fly from a set of segmented exemplar images. Iteratively minimising the CRF energy leads to optimal segmentation. Experimental results on the Pascal visual object classes (VOC) 2010 segmentation dataset, a widely acknowledged difficult dataset, show that the proposed approach outperforms the state-of-the-art techniques.

A design for an integer motion estimator of high-efficiency video coding (HEVC) is presented. HEVC supports the 64 × 64 coding tree unit, the recursive quad-tree coding unit structure and the asymmetric motion-partitioning mode in a high compression ratio. These features require a structure of integer motion estimation that is more complex than that of H.264/AVC. The new structures of a memory read controller and a sum of absolute difference (SAD) summation block are proposed. The new memory read controller reduces the internal memory read time, and the new SAD summation block structure supports the recursive quad-tree coding unit structure and the asymmetric motion-partitioning mode. The proposed design is implemented in Verilog HDL and synthesised using the 65 nm CMOS technology. The gate count is 3.56 M, and the internal static random access memory is about 20 kbyte. The operation frequency is 250 MHz when a 4 K-Ultra high definition (UHD) (3840 × 2160P at 30 Hz) sized video is encoded.

The problem of foreground detection in real-time video surveillance applications is addressed. Proposes is a framework, which is computationally cheap and has low memory requirements. It combines two simple processing blocks, both of which are essentially background subtraction algorithms. The main novelty of the approach is a combination of an autoregressive moving average filter with two background models having different adaptation speeds. The first model, having a lower adaptation speed, models long-term background and detects foreground objects by finding areas in the current frame which significantly differ from the proposed background model. The second model, with a higher adaptation speed, models the short-term background and is responsible for finding regions in the scene with a high foreground object activity. The final foreground detection is built by combining the outputs from these building blocks. The foreground obtained by the long-term modelling block is verified by the output of the short-term modelling block, i.e. only the objects exhibiting significant motion are detected as real foreground objects. The proposed method results in a very good foreground detection performance at a low computational cost.

A VLSI architecture of a context adaptive binary arithmetic coding (CABAC) entropy codec for high-efficiency video coding (HEVC), the next generation video coding standard, is presented and analysis of its performance in terms of effective processing throughput, i.e. bin/s, is provided. For high throughput, the architecture is designed to process up to two regular bins per unit time while minimising pipeline stall due to inherent dependencies of CABAC through various optimisations including context forwarding and speculative decoding. The experiments show that the effective throughput is achieved up to 1.60 bins or 1.41 bits per cycle, which corresponds to 469.5 Mbit/s at the operating frequency of 333 MHz, under practical video coding environments.

A parametric model to estimate the degradation of objective video quality over error-prone networks is proposed. The model estimates an expected quality degradation in terms of one of the most reliable perceptual quality metrics, structural similarities (SSIMs), for a given encoded video and network condition described by a packet loss rate. The simulation results demonstrate that the proposed model can estimate the expected SSIM degradation of H.264/ advanced video coding encoded videos with high accuracy.

An algorithm that introduces a novel scheme for the combination of the two adaptation terms of the affine projection algorithm with different step sizes is proposed. The mixing parameter of the proposed algorithm is determined by minimising the mean-square deviation. The simulation results show that the proposed algorithm has a faster convergence rate and a smaller steady-state error than other existing combination algorithms.

Subband transformation coefficients are typically computed by first filtering and downsampling of an input uncompressed signal and then subsequently filtering and downsampling the result intermediate signals with a set of lowpass and highpass filters. State-of-the-art subband transformers are complex, which increases consumed power. A novel method for significantly decreasing the complexity of subband transformers to a minimum is presented. This solution was implemented in a field programmable gate array, together with various methods for compression and decompression.

An expression of the minimum mean square error (MMSE) of the linear MMSE channel estimation is given in the case of a non-invertible channel covariance matrix, as in single-input single-output (SISO) OFDM system. A matrix expression, already proposed for a multi-input multi-output OFDM system in a previous article, is not valid in SISO. A new proof is then proposed, by deriving a scalar expression of the MMSE, which leads to solve an optimisation problem. Furthermore, we show that the proposed solution is the global minimum. Simulations validate the proposed development.

A new post-processing approach which aims at reducing the dispersion effect of the wave travelling inside a waveguide is presented. The main objective is to improve the time domain reflectometry measurements performed over long-distance cables, relative to the wavelength λ. A real-case scenario is presented so that the gain of this method can be appreciated.

A compact ultra-wideband differential bandpass filter (BPF) based on a self-coupled ring resonator is proposed. The self-coupled line contributes to not only three poles in differential-mode (DM) but also three zeros in common-mode (CM) offering both a wide differential passband and good CM suppression. A fabricated filter with a 3 dB fractional bandwidth of 118% for the DM and insertion loss greater than 18 dB for the CM has been designed and measured. This filter is only 30.4 × 1.0 mm (1.0λ ₀ × 0.03λ ₀) and it is only 15% of the size of the most reported differential BPFs. The simulated and measured results are in good agreement.

A dual-band bandpass filter in a millimetre-wave band that uses 0.5 μm GaAs pHEMT technology with two sets of stepped-impedance resonators, which results in a reduction in size, is presented. The two passband frequencies can be flexibly controlled by adjusting the lengths of the two sets of resonators. Two bandwidths can be tuned independently, using external quality factors and coupling coefficients. The fractional 1-dB bandwidths at 60 and 77 GHz are 8.6 and 4.1%, respectively. The measured S ₂₁ values at 60 and 77 GHz are − 2.26 and − 3.9 dB. Good performance is obtained in terms of the excellent microwave properties of the semi-insulating GaAs substrate, which makes this system attractive for wireless communication applications.

A compact microstrip lowpass filter (LPF) with sharp roll-off and ultra-wide stop-band bandwidth is presented. The structure consists of high-impedance meandered transmission lines loaded by triangular and polygonal resonant patches. The cutoff frequency of the proposed LPF is 2.44 GHz and the measured results show good performance such as sharp roll-off, good insertion loss and an ultra-wide stop-band from 2.53 to 35 GHz with the insertion-loss higher than 20 dB. There is a good agreement between the electromagnetic-simulation and measurement results.

A novel millimetre-wave quasi-optical low-loss power divider based on the dipole antenna is presented. This dipole antenna array is inserted in the E-plane of the rectangular waveguide to implement the power-dividing function. A Ka-band four-way passive power combiner is designed, fabricated and measured. The measured results show that the minimum insertion loss is about 0.4 dB from 32.1 to 34 GHz, whereas the return loss is less than 10 dB from 31.5 to 35.9 GHz. The measured results agree with the simulated ones closely.

A novel dual-wideband bandpass filter (BPF) by using the proposed dual-band open stub-loaded coupled-line section is presented. The proposed dual-band BPF has a symmetrical frequency response along the designing frequency f ₀, and the transmission zero at f ₀ improves the filter band-to-band isolation significantly. As an example, a dual-wideband BPF for 2.4 GHz WLAN and 6.8 GHz RFID applications is designed, fabricated and measured. The fabricated filter has the merits of simple topology, compact size, good return loss, low insertion loss and high isolation. The measurement agrees well with the simulation.

A two-dimensional crest factor reduction (2D-CFR) is proposed to improve the performance of concurrent dual-band power amplifiers (PAs). Experimental measurements are performed on a 1.9–2.6 GHz concurrent dual-band LTE PA by using the proposed 2D-CFR and conventional 1D-CFR, respectively. Measured results after 2D digital predistortion (2D-DPD) show that the output power with the proposed 2D-CFR is increased by 10%, the efficiency is improved from 28.1 to 30.6% and the error vector magnitude is reduced from 3.46 to 2.67%, indicating a significant performance improvement.

A technique is proposed and demonstrated to simultaneously measure the phase noise of four-wave mixing components, using a combination of heterodyning and delayed self-heterodyning techniques.

A novel inertial micro-switch capable of prolonging contact time and reducing the contact-bouncing effect is proposed. Based on the nonlinear-spring shock stop, both the moveable and the fixed electrodes are made flexible by using a moveable contact point and a cascaded beam, respectively. The switch was successfully fabricated by bulk micromachining process. From the drop hammer test, the switch-on time increased with an increase of the input acceleration and reached a maximum of 335 μs, which is over 30 times larger than that of the traditional switch; and no bounce occurred.

A thin film of silica aerogel has been spin coated on silicon wafers to investigate its super thermal insulating capability. The temperature of the thin film heaters fabricated on the aerogel coated wafer is measured at different applied powers. Simulations are performed to compare the aerogel coated wafers with the micromachined wafers. Both experimental and simulation results show better heat insulation for aerogel coated wafers as compared with simulated micromachined wafers. The measurement and simulation results of aerogel coated wafers are in good agreement. The aerogel film can replace the air cavity created by conventional micromachining of wafers to save power and chip area in metal oxide gas sensor arrays.

A self-adaptive load technology for multiple-string LED drivers is presented. Directly operating from an AC voltage, the proposed technology realises soft switching with a self-adaptive load resistor, so that the LED avoids the current glitch during current switching. Thus, the quality of lighting, the lifetime and the performance of the LED are improved. An AC LED driver using the proposed technology was fabricated in a 0.25 µm BCDMOS process and tested with a five-string LED. The measured results show that the power factor is 0.998 (0.997) with 5.1% (7.2%) total harmonic distortion under 19 W 110 V/AC (220 V/AC) condition.

A new method to generate ultra-wideband (UWB) pulses based on direct modulation of laser and optical filtering is demonstrated. The intensity modulation and the frequency modulation of the directly modulated laser are combined by the optical filter, which performs a photonic electro-optical derivative operation. Gaussian driving pulses are used in order to generate monocycles for ultra-wideband systems. In association with laser power oscillation, doublet waveforms could also be obtained. Monocycle and doublet pulses are experimentally generated with fractional bandwidths of 139 and 105%, respectively.

A report is presented on the tuning of the frequency envelope of a broadband comb source generated from a semiconductor-based modelocked ring laser with an intracavity high finesse Fabry-Pérot etalon (FPE). By deliberately adjusting the matching condition between FPE transmission peaks and lasing optical comb frequencies, ∼ 7 nm tuning of more than 200 optical frequency comb lines spaced by 10 GHz is achieved.

A novel rectifier with a considerably extended operating input power range is presented for wireless power transmission applications. The rectifier utilises a depletion-mode to enhance the diode's breakdown voltage while its built-in voltage is preserved. As a result, in comparison with traditional rectifiers, this proposed rectifier can achieve a high RF-to-DC conversion efficiency in a much wider input power range. Measurement results show that a conversion efficiency of more than 50% can be obtained over the input power range from − 13.5 to 16.7 dBm, proving that this rectifier is suitable for the wireless power transmission applications with varying input power levels.

A fast algorithm based on the self-resonant frequency for decoupling capacitor (decap) selection is proposed and verified experimentally. The proposed algorithm has been compared with the genetic algorithm (GA). Results show that they both give quality and similar decoupling solutions, but the proposed algorithm is superior to the GA in computation speed.

Analogue VHF waveforms have been used extensively as signals of opportunity in passive radar concepts. They have time-varying ambiguity properties determined by the instantaneous nature of the broadcast content and correspondingly this results in a time-varying radar performance. In this reported work, the ambiguity properties of high definition (HD) FM signals are examined. It is shown that the digital modulation imposed on these transmissions results in more stable ambiguity properties better suited to reliable and consistent passive radar performance.

A computational-efficient estimated rule of clutter rank for multiple-input multiple-output (MIMO) radar with arbitrary transmitted waveform synthetic strategies is presented and proved. It is suitable for both conventional phased array radar and MIMO radar with a uniform sparse or non-uniform sparse transmitting subarray, and is also valuable for the design of optimal waveform synthetic strategies and space–time adaptive processing algorithms. The effectiveness of the proposed rule is verified by simulation results.

The backscattering measurement of a rectangular solid volume of polystyrene foam (width: 0.92 m; height: 0.9 m; depth: 1.82 m) carried out at frequencies ranging from 59 to 60 GHz is described with horizontal polarisation for both transmission and reception antennas. The volume fraction of polystyrene in the measured material is about 0.01. The normalised radar cross-section of the measured polystyrene foam sample is estimated as 2.9 × 10 ^{− 3}(±3 × 10 ^{− 4}) m²/m³ by using the range-resolved data of the backscattered power arising from inside of the polystyrene foam volume. When using polystyrene foam as a support for radar targets in radar measurements, this result is considered useful for quantitatively estimating the intensity of the unwanted backscattered waves due to the foam.

A directionlet transform (DT)-based multiscale products thresholding is presented which uses a generalised cross-validation (GCV) technique for synthetic aperture radar image despeckling. DT has gained popularity over the past few years as an anisotropic, critically sampled and perfect reconstruction transform with directional vanishing moments along any two directions. In this reported work, the multiscale correlation of DT is exploited by multiplying the adjacent scale coefficients to enhance edge structures while weakening noise. An optimal subband adaptive threshold based on GCV is then computed using this multiscale product. The despeckled image is finally synthesised by using the threshold applied DT coefficients. The employment of DT results in the significant features in images evolving with high magnitudes across scales, while the noise decays rapidly. The proposed scheme outperforms many of the traditional despeckling schemes in terms of speckle reduction and edge preservation.

Magnitude modulation (MM) envelope control is an efficient way of reducing the peak-to-average power ratio (PAPR) of single-carrier (SC) signals and improves an SC system's overall power efficiency. However, MM techniques reduce the PAPR at the cost of introducing distortion, highlighting a need to characterise the symbol error rate (SER) performance loss due to MM. This reported work focuses on the M-PSK case. An exact probability density function (PDF) based on the generalised extreme value distribution is proposed to model the statistical distribution of MM factors generated by MM techniques applied to SC constant amplitude constellations. By considering MM distortion as a form of fading, it is shown that this PDF may be used to derive an accurate union bound of the SER of M-PSK transmission on the additive white Gaussian channel channel when using MM envelope control.

The outage probability of an efficient signal space cooperative (SSC) scheme is investigated over general independent and non-identically distributed Nakagami-m fading channels. In particular, the exact outage probability expression is derived for arbitrary values of the fading parameter m (m ≥ 0.5). Furthermore, an asymptotic approximation for the outage probability is obtained, which clearly shows the diversity and coding gains of the SSC scheme, and therefore can offer important theoretical guidance to scheme designers. Simulation results are provided to verify the theoretical analysis.

Recovering a distance from ambiguous phase measurements observed at multiple signal frequencies involves the estimation of both integer and scalar quantities simultaneously. The problem is optimally addressed by existing methods only when the measurement noise is IID. A noise ‘whitening’ procedure is derived with a least-square estimation structure inherent to the Lattice method proposed previously which thus extends this Lattice-based algorithm to cope with coloured phase measurement noise in an optimal manner demonstrated via simulation.