An innovative way to manufacture a sectoral horn antenna with a biconvex dielectric lens is presented. The antenna focuses on the near-field signal in the H-plane to illuminate a linear array for example. It is made of only two symmetrical pieces of foam and a metallic support. A prototype is manufactured and measured at 60 GHz to verify its focusing properties and validate the technological process.

A compact, planar antenna operating at 433 MHz is proposed for wireless smart systems with dimensions of 51 × 28 mm² including a ground plane, and printed on a low-cost FR4 material. Significant size reduction is achieved using the variation of an inverted-F antenna configuration with a square-spiral section and rectangular patch element. Fine-tuning of the antenna's resonant frequency is possible using a small capacitive stub. Sensor and radio transceiver electronics can be accommodated above the ground plane. The measured results indicate a 10 dB return loss bandwidth of 4.5 MHz, and a peak realised gain of −13 dBi with omnidirectional radiation characteristics.

A single-layer reflectarray with a combination of element types is proposed. Three element types—square patch, square ring and ring-loaded patch (RLP)—are used together to design the reflectarray by compensating for the drawbacks of one type by the others. The gain of the proposed reflectarray is 29.1 dBi, which is 1.9 dB higher than that of the reference reflectarray that was designed with only the RLP.

Characterisation results of the complex permittivity of select dielectric cooling fluids at room temperature and over a broad frequency range found using a low-loss printed circuit board microstrip ring resonator technique are presented. ANSYS HFSS, a finite-element full-wave electromagnetic simulation environment, was used to fit the simulated insertion loss to the calibrated measurements of the microstrip ring resonator in air and submerged in different dielectric fluids. The resulting frequency-dependent relative permittivity and loss tangent are provided up to 50 GHz for three dielectric cooling fluids: 3M™ Novec™ 649, 3M™ Novec™ HFE-7100 and 3M™ Fluorinert™ FC-72.

A low-noise area-efficient potentiostat design for nanopore applications is presented. By adopting a cascode amplifier and a Wilson current mirror, the input resistance is drastically decreased, which enables one to obtain a desirable bandwidth to detect DNA translocation events in nanopore sensors. A novel compensation technique is also proposed to relieve a deleterious effect by the input parasitic capacitances.

A multichannel high-resolution single-slope analogue-to-digital converter (SS ADC) is presented that automatically compensates for process, voltage and temperature variations, as well as for radiation effects, in order to be used in extreme environmental conditions. The design combines an efficient implementation by using a feedback loop that ensures an inherently monotonic and very accurate ramp generation, with high levels of configurability in terms of resolution and conversion rate, as well as input voltage range. The SS ADC was designed in a standard 0.35 µm CMOS technology. Experimental measurements of the performance and stability against radiation and temperature are presented to verify the proposed approach.

A simple method that reduces congestion in the bufferless network-on-chip (NoC) is proposed. The method uses the time average of link utilisation as its congestion measure, and is applicable to deflection routing algorithms. A cycle-based NoC simulator is used to evaluate a bufferless NoC with and without the congestion reduction, and the performance and energy consumption are found to improve under heavy load.

A novel two-stage amplifier topology and ultra-low power design strategy for two-stage amplifiers that utilises pole zero cancellation to address the additional power requirements for stability are presented. For a 288 nA total bias, the presented amplifier achieves a 1.07 MHz unity gain frequency with a 8560 pF MHz/mA figure of merit.

The spin-orbit-torque magnetic tunnel junction (SOT-MTJ) is a promising device for data storage. Most of the issues encountered with scalable spin transfer-torque (STT) devices are visibly moved. Thanks to a three-terminal architecture, the reliability is increased by separating the read and the write paths. Furthermore, SOT-induced magnetisation switching can be very fast, thanks to a low-resistive writing path. The writing operation is symmetrical. Thus, it requires the same current density to switch between the parallel and antiparallel states. All these advantages make the SOT-MTJ device an ultimate candidate for introducing non-volatility in ultra-fast and power-efficient integrated circuits. A mixed CMOS/magnetic non-volatile flip-flop (NVFF) is described. The proposed architecture offers the possibility to use the usual CMOS flip-flop functionality with possible magnetic data store and restore operations while keeping non-volatility when the circuit is powered off. With a 135 nm dimension, the SOT-MTJ-based NVFF demonstrated a very high switching with a 5× decrease in terms of writing energy/bit when compared with an STT device.

A simple method for dynamically adjusting the tap-length adaptation step-size of a variable tap-length linear equaliser based on the fractional tap-length algorithm is presented. Simulations show that the technique provides a fast convergence of tap-length and small steady-state tap-length fluctuation.

A low-power analogue readout circuit for quanta image sensors is reported. A modified charge-transfer amplifier is used in column-parallel circuits to reduce the internal readout circuit power 50-fold compared to the state of the art, and will achieve 2 mW total power dissipation (all columns) when applied to a 1 Mpixel binary image sensor operating at 1000 fields per second.

A new compressive sensing (CS) scheme using the structured random matrix and the discrete periodic Radon transform (DPRT) is proposed. The new scheme first pre-randomises the sensing image and the DPRT is applied to the randomised samples to generate the so-called DPRT projections. They are then randomly selected to obtain the final sensing measurements. As the DPRT is friendly to hardware/optics implementation, it improves the operability and lowers the cost for real-time CS applications. Compared with other similar transforms such as the Walsh–Hadamard transform, the proposed DPRT scheme gives much better reconstructed images as shown in the simulation results.

A robust method to detect foreground regions in video sequences is presented. For each pixel, the time series of pixel intensity is represented as symbol sequences that are trained and modelled using the Markov model to obtain the anomaly detection threshold. The foreground extraction is performed by comparing the anomaly transition probability of each pixel and its detection threshold. The experimental results demonstrate that the proposed method outperforms the traditional methods.

A blind/no-reference (NR) image quality assessment (IQA) algorithm based on natural scenes is developed. The proposed algorithm does not need training on databases of human judgments of distorted images or even prior knowledge about expected distortions (as is the case in most general NR IQA algorithms). To measure the image quality, the introduced approach uses a set of novel features in a spatial domain. The devised features are formed using the Weibull statistics of log-derivatives. When testing the proposed algorithm on the LIVE database, experiments showed that it correlates well with subjective opinion scores. In addition, they indicated that the new method has a good performance when compared with the state-of-the-art methods.

A novel three-dimensional (3D) surface texture measure (3DSTM) is presented based on the micro-geometry of paper surfaces to classify different paper substrates. This is useful to automatically determine whether a document is printed on the correct paper substrate to help identify fraud. We use a 4-light source photometric stereo (PS) method to recover the dense 3D geometry of paper surfaces captured using a high-resolution sensing device. We derive a unique 3DSTM for each paper type based on the shape index (SI) map generated from the surface normals of the 3D data. We show that the proposed 3DSTM can robustly and accurately classify paper substrates with different physical properties and different surface textures. The accuracy of the proposed method is validated over a dataset comprising of 21 printed and 22 non-printed paper types and a measure of success over 92% is achieved.

A novel scheme for separable data hiding in an encrypted image based on compressive sensing (CS) is presented. In the first phase, the content owner encrypts the original image with an encryption key and leaves some space for the data-hider to embed data. Therefore the image is enlarged. The data-hider embeds additional data to the image for a specific purpose in a fixed location. As the image is enlarged, the data-hider can compress the image to the original size using CS with the data-hiding key. Thus, the encrypted image with embedded data is generated. The way to obtain image content and additional data is separable. If a receiver has the encryption key, he can decrypt the unintelligent data to obtain an image similar to the original one, but cannot extract the additional data. Similarly, if a receiver has the data-hiding key, he can extract the watermark without seeing the content of the image. If the receiver has both the encryption key and the data-hiding key, he can extract the additional data and recover the original image by exploiting CS recovery algorithms.

A multisensor fusion-based unknown object detection and tracking approach is presented. The approach consists of two new algorithms: (i) object segmentation by boundary detection and (ii) data association by integer programming. The proposed approach tightly combines the information from a single-line scanning lidar and a camera. The performance of the proposed algorithm is evaluated by comparing with a state-of-the-art method and is demonstrated with real datasets obtained from a moving platform.

A non-algorithmic physical random bit generator is introduced, using a graphic processing unit (GPU) as a random source. The generator takes randomness from parallel threads executing atomic instructions. The generator in terms of pass rates from the National Institute of Standards and Technology (NIST)’s statistical test suite and bit generation throughput is evaluated. The generator compares favourably with pseudorandom bit generators known to have fine statistical properties. The test bed Nvidia's GPU GTX 680 can generate random bits at the rate of hundreds of megabits per second. The cost-effectiveness of GPUs as random key generators can be increased, as GPUs are now readily available in most desktop computers, and even in smart phones.

Sequences with an optimal autocorrelation property and with large linear complexity are needed in certain communication systems and cryptography. Tang and Ding obtained new classes of almost balanced binary sequences with an optimal autocorrelation value. In this reported work, it is explored as to when interleaved binary sequences of period 4p obtained by Tang and Ding's technique from Hall sequences or Legendre and Hall sequences possess high linear complexity.

An 89 GHz waveguide coupled direct detector based on a low-barrier Schottky diode is presented. The main focus is to reduce white and 1/f noise to achieve high signal-to-noise ratio values above 35 dB. The design also addresses the Schottky barrier height deviation over temperature and its compensation within the RF circuit. The fabricated detector is characterised and compared with simulation results, proving a high accuracy level of the design and fabrication process, as well as good knowledge of the applied Schottky diode. The results prove the suitability of the detector to be considered for the second European meteorological operational satellite programme (MetOp-SG).

A novel filtering power divider (PD) with an extended isolation bandwidth is proposed. Adopting a frequency-dependent resistor–inductor–capacitor isolation network enabled designing and improving isolation performance. An embedded 90° filtering line was realised by employing two coupled quarter-wavelength resonators to achieve a bandpass response and a compact circuit size. The filtering PD was designed and implemented at a centre frequency of 1 GHz, and the isolation bandwidth (> 20 dB) was extended from DC to 2.2f ₀.

A novel bandpass filter with multiple transmission zeros using open/shorted dual-behaviour resonators (DBRs) is proposed. Three transmission zeros on both sides of the bandpass responses can be easily realised. Three additional transmission zeros without bandstop/lowpass networks are used to suppress the second harmonic. A bandpass filter prototype with 15 dB rejection level in the upper stopband from 1.1f ₀ to 2.72f ₀ (3 dB fractional bandwidth 7.3%) has been designed and fabricated.

A dual-band bandpass filter (BPF) using a novel stepped-impedance stub resonator (SISR) is presented. The proposed SISR is found to have the advantage that the even-mode resonant frequencies can be flexibly controlled, whereas the odd-mode resonant frequencies are fixed. Based on the proposed SISR, a dual-band filter is implemented by tuning its geometric parameters. To improve the selectivity, a filter with four transmission zeros on either side of both passbands is designed by introducing a 0° feeding structure. A prototype of a dual-band BPF centred at 1.84 and 2.65 GHz has been designed and fabricated. The measured results validate the full-wave EM simulated results.

A novel multilayer in-phase slotline power divider with bandpass response and one tunable notched band is proposed. The presented power divider employs the structure of microstrip-to-slotline transition to split the input signals over the frequency range 3.5–10 GHz. A wide upper stopband is obtained by using an interdigital configuration and introducing a defected ground structure. A quarter-wavelength short-circuited stub is utilised to obtain the tunable notched band in the passband. The experimental results indicate that the proposed power divider has good phase balance, high isolation between output ports, good return losses at all ports and flat group delay over a wide frequency range.

A terahertz (THz) waveguide-fed antipodal tapered slot antenna (ATSA) based on silicon micromachined technology is proposed. The ATSA is composed of an antipodal tapered slots structure and a WR2.2 feeding waveguide, monolithically fabricated by deep reactive-ion etching, and sputtering gold and gold–gold thermo-compression bonding. The input return loss is tested and shows a level below −15 dB within 480 to 500 GHz. The gaussicity of radiation patterns at the working band is calculated to be 90%. Through further experiment, at 492 GHz, the ATSA exhibits asymmetric beamwidths of 25.5° and 25° in the E- and H- planes, respectively, and sidelobes below −8 dB, along with a 14.6 dB gain, which agree well with the simulated results. The proposed THz waveguide-fed ATSA is suitable for use as a feeder of THz imaging and detection systems.

A wideband six-port-based demodulator is proposed and applied as a quadrature phase shift keying (QPSK) demodulator for optimal K-band multiport amplifier (MPA) calibration circuitry. The proposed six-port demodulator adopts wideband ring hybrids for optimal 180° phase balance in local oscillator signal paths. In addition, a voltage-controlled reflection-type phase shifter and an attenuator are integrated into the six-port structure to ensure accurate magnitude and phase balance over broadband operation, resulting in optimal phase and amplitude error detection for the MPA system. To verify the proposed structure, RF demodulation of the K-band QPSK modulated signal was demonstrated for purpose of MPA calibration.

Several phantoms have been fabricated for reflection measurements from human tissues in the range of 26.5–40 GHz. For the first time, a novel composition is introduced for fabrication of low-cost simple tissue-equivalent phantoms. The effective medium theory is applied to estimate the dielectric properties of phantoms consisting of polyethylene (PE) powder and the results are verified by dielectric properties measurement on the proposed phantoms. It is shown that mixing theory can estimate the dielectric properties of the PE-based phantoms with minimum error. Therefore, the amount of the ingredients can be estimated theoretically.

A two-dimensional displacement and alignment sensor is proposed based on two open-ended transmission lines, each loaded with a split ring resonator (SRR). In this arrangement, the depth of resonance-induced notches in the reflection coefficients can be used to sense a displacement of the loading SRRs in two orthogonal directions. Since the operation principle of the sensor is based on the symmetry properties of SRR-loaded transmission lines, the proposed sensor benefits from immunity to variations in ambient conditions. More importantly, it is shown that in contrast to previously published metamaterial-inspired two-dimensional displacement and alignment sensors, the proposed sensor can be operated at a single fixed frequency. The concept and simulation results are validated through measurement.

Films of Ag nanoislands (NIs) were successfully grown on two different transparent conducting oxide coated substrates (indium tin oxide (ITO) coated glass and indium oxide (In₂O₃) coated polyethylene terephthalate (PET) flexible film) by direct current (DC) magnetron sputtering. The morphology of the Ag NIs was studied using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Both SEM and TEM confirm the formation of silver NIs. To amplify the localised surface plasmon resonance (SPR) effect, post-deposition annealing was performed at 200°C for 30 minutes in a nitrogen atmosphere, resulting in tuning the shape and size of the NIs. Optical transmission spectroscopy was performed in the ultraviolet–visible–near-infrared spectral region to examine the SPR characteristics of the Ag NIs deposited on ITO-glass and In₂O₃-PET. Post-deposition annealing is found to tune the SPR wavelength and results in strong enhancement of the SPR of the Ag NIs on both ITO-glass and In₂O₃-PET. DC magnetron sputtering and the post-deposition annealing technique can be applied for the growth of size-controlled Ag NIs. The result can be applied to the enhancement of the efficiency of organic light emitting diodes and solar cells.

Based on a photonic crystal fibre (PCF) pumped by an ytterbium-doped fibre laser, a high-efficiency all-fibre optical parametric oscillator (OPO) is demonstrated. The high conversion efficiency is guaranteed by the relatively low intra-cavity loss of the all-fibre configuration. In the experiment, an internal conversion efficiency of up to 36% is achieved, which is believed to be the largest value for PCF-based OPOs.

Current sensing based on the Faraday effect in optical fibres is a well-established area in the landscape of sensor technologies. However, the optical behaviour that sets an upper limit on the detection bandwidth is often overlooked. The underlying mechanisms are explored in this reported analysis to raise awareness about their impact on the measurement results. The findings show that the Faraday effect cancellation and pulse broadening grow with increasing signal frequency, which result in suppression and distortion of the optical response. A correction factor is proposed for alternating and pulsed signals when using the simplified equation, to maintain an accurate measure of the peak current.

It is 18 years since the V ² control was proposed in 1996. Many publications have shown that the V ² controlled switching converter exhibits an ultra-fast load transient response. Recently, it has been reported that the conventional V ² control is inherently a peak V ² control, based on which V ² control can be classified as peak V ² and valley V ² controls. However, till now the switching converter with V ² control is almost a buck converter. This leads to the investigation of whether the V ² control can be applied to a boost converter.

The optimal capacitive load condition is derived for a passive bridge rectifier to harvest the maximum amount of energy when a piezoelectric generator (PG) receives a single vibration pulse (e.g. a button press). When the PG is modelled as a current pulse generator with an internal shunt capacitance (C_P ), it is shown that an ideal bridge rectifier collects the maximum energy when its output capacitance is set to 3·C_P . The impacts of the nonzero turn-on voltage and on-resistance of the diodes are also discussed. The experimental results with a 300 mm² lead magnesium niobate-lead titanate PG and a Schottky-bridge rectifier with 0.22 V turn-on voltage demonstrate that the maximum energy transfer occurs at a capacitance ratio of 3.3, collecting 117 μJ from a single button press.

Carrier-based modulation has been widely adopted since it offers some benefits compared to space-vector modulation in both two-level and in multilevel three-phase inverters, such as inherent simplicity, flexibility, reduced computational times and easy implementation on industrial DSPs. Among the numerous types of pulse width modulation (PWM) techniques, the centred PWM (CPWM) is nearly optimal modulation since it minimises the RMS of the output current harmonics. Despite optimised CPWM being easy to implement in two-level inverters, the complexity increases in the case of three-level and multilevel inverters. A straightforward and simplified procedure to implement optimised CPWM in carried-based modulation for the three-level inverter is proposed and numerically verified.

High-performance fully transparent bottom-gate type dual-layer (ITO/TZO) channel thin-film transistors (ITO/TZO TFTs) have been successfully fabricated on a glass substrate at low temperature (below 100°C). The results show that dual-layer channel (ITO/TZO) TFTs, compared to the single channel TZO TFTs and ITO TFTs, exhibit better electrical properties, with a low I _off of 1.5 × 10⁻¹¹ A, a high on/off ratio of 5.78 × 10⁷, a high saturation mobility μ _s of 292 cm²/V·s, a high linear mobility μ _l of 105.4 cm²/V·s, a steep subthreshold swing of 0.33 V/decade and a threshold voltage V _th of 3.16 V. The results show that excellent device performance can be realised in ITO/TZO TFTs.

Many digital delta–sigma radio frequency (RF) upconverters exhibit poor performance when the carrier frequency is tuned away from the centre of the band. The offsetting of signals from the nominal carrier frequency position generates unwanted distortion products which are dominated by the image and third harmonics. It is shown that these products can be moved out of the band by the correct choice of intermediate frequency. A novel technique for shifting both the signal and the noise null to the new frequency position is described.

A new hybrid automatic repeat request (HARQ) scheme is proposed for multiple-input multiple-output (MIMO) systems when the acknowledgment (ACK) bundling is applied for packet retransmissions. In the proposed HARQ scheme, both Chase combining (CC) and incremental redundancy (IR) are utilised for a retransmission request, and the proposed HARQ scheme is called a multiple retransmission strategy-based HARQ (MRS-HARQ). During the reception process of the MRS-HARQ, IR packets obtain signal-to-noise ratio gains using the extended detection with CC packets and the improved IR packets are utilised to eliminate the interference from the CC packets. This sequential reliability improvement allows the MRS-HARQ to decrease the occurrence of the deficient transmissions, and the proposed MRS-HARQ can achieve an improved error performance and throughput over the conventional CC-based and IR-based HARQ schemes with the ACK bundling.

A novel coverage radius-based downlink power control scheme to mitigate interference in densely deployed femtocells is presented. A femtocell access point (FAP) self-update algorithm is implemented, which determines the coverage radius of the femtocell with respect to its farthest served femtocell user equipment (FUE). Based on varying coverage radii, a max/min function is used to adjust the downlink transmit power value of a FAP. System-level simulations are performed to compare the performance of the presented scheme with the existing fixed coverage radius schemes. Even though the proposed scheme results in better cross-tier signal to interference plus noise ratio (SINR) values, due to a low co-tier SINR it is found that the efficacy of adaptive power control schemes based on the pilot power of a FAP is less significant if FUEs are located close to the neighbouring FAPs in densely deployed urban femtocells.