A wideband planar unidirectional circularly polarised slot array is proposed. The slot array has a truly planar structure where the feeding network is integrated with the radiating elements on the same substrate, which makes it low cost and easy to fabricate. The measured result shows that the proposed array obtains an impedance bandwidth of 33.8% and an axial ratio bandwidth of 24.5%. The proposed array has a good unidirectional pattern and can be used in base station applications.

Wide-band (WB) and narrow-band (NB) antennas in terms of performance are compared, when interacting with the user's right head and hand (RHH). The investigations are done through experimental measurements, using standardised head phantom and hand. It is shown that WB antennas detune more than NB antennas, but the drop in efficiency, when placed in RHH position, is similar for both antennas.

The design of a high-frequency radiating element plus a broadband shifting circuit for reflectarray device cells is provided. The cell design is based on modified broadband 3 dB/90° reflecting circuit interlacing polarisation, along with a multilayered planar radiating element. The basics of the structure are to capture the signal at each cell of the reflectarray, to introduce the proper phase shift by means of the modified 3 dB/90° shifter and to re-radiate the signal again towards the radiating direction. This device reduces the complexity of the reflectarray cells in terms of design and manufacturing, enabling it to deal with circular polarisation in an easily affordable manner. The complete design of the unitary cell is provided.

A circularly polarised (CP) wideband hook-shaped microstrip fed patch antenna is presented. The wideband CP property for the proposed antenna is achieved by the hook-shaped branch in the ground plane and inverted asymmetric arm L-shaped microstrip fed. With an optimised dimension of the proposed antenna parameter, the experimental results show that the antenna has a 10 dB impedance bandwidth of 1.41 GHz (1.84–3.25 GHz) and 3 dB axial ratio bandwidth of 1.67 GHz (1.86–3.53 GHz).

Deep brain stimulation (DBS) is widely used for the treatment of various neurological diseases such as Parkinson's disease and tremors. Owing to the inherent limitations of the imaging modalities, physicians have a difficulty in the diagnosis of the exact response to the brain tissues during stimulation. Recent magnetic resonance (MR)-based electrical impedance tomography (MREIT) enables estimation of the current density distribution from the measured magnetic flux density data. Applying MREIT to DBS, one can predict the current pathway and electric field distribution which could be useful information for proving the therapeutic effects of electrical stimulation.

Measuring the relative motion of the femur and tibia in a knee joint currently requires tantalum beads to be implanted into the bones. These beads appear as high-intensity features in radiographs and can be used for precise kinematic measurements. This procedure imposes a strong coupling between accuracy and invasiveness. Advances in ultrasound (US) sensor technology and the availability of micro-drives mean that it is now possible to construct a small and lightweight US sensor which can be placed on the skin above the tibia and femur. Such a sensor could determine the relative movement of the underlying bone with respect to the sensor. This would then allow the position of the femur and tibia to be measured more accurately than with an optical tracking system that does not take into account the movement of the marker with respect to the bone. For satisfactory performance, the precision of the US sensor should be in the order of 1 mm or less. The experimental results prove that this sub-millimetre precision is achievable.

A sensing probe for medical imaging diagnostic systems is presented. The proposed probe consists of a double-ridged waveguide (DRWG) filled with dielectric ceramic and an aperture with a tapered ridge. The DRWG is used to suppress higher-order mode radiations in the rectangular waveguide. The proposed probe is designed for broadband sensing in an immersion liquid with a complex dielectric constant. The performance of the fabricated probe successfully covers the frequency band of 3–6 GHz. The probe suppresses higher-order modes and provides symmetric and similar radiation patterns within the operating frequency range.

A new constant twiddle factor multiplier sharing method in parallel pipelined fast Fourier transform (FFT) processors based on a multi-path delay feedback architecture which consists of multiple single-path delay feedback datapaths is presented. The proposed method exploits constant twiddle factor multiplier relocation which moves a constant twiddle factor multiplier into a feedback path based on twiddle factor decomposition. By relocating a twiddle factor multiplier, the timing of twiddle factor multiplications is changed so that the multiplications with a twiddle factor are performed at different clock cycles in two datapaths, which makes it possible that the two datapaths share a multiplier operating with the twiddle factor. A reduction of 50% in the number of constant twiddle factor multipliers in the first two stages of a 128-point four-parallel pipelined FFT processor is achieved using the proposed method.

A ternary clock generator (TCG) is proposed to settle its shortage. The TCG is implemented at the switch level with a simple structure of 24 MOS transistors and simulated at the layout level using the HSPICE software with TSMC 0.18 μm CMOS technology, showing that it works properly. The analyses show that the proposed TCG not only can output a ternary clock of high quality, meeting the clock's design requirements, but also can be fabricated with standard CMOS technology.

A new small-swing domino logic that reduces the signal amplitude by adding twist-connected PMOS and NMOS transistors in the conventional domino logic is presented. The circuit lowers the voltage level of a logic ‘1’ and increases the voltage level of a logic ‘0’ while maintaining the logic threshold at half of the supply voltage. The output swing range of the proposed circuit can be modulated by varying the size of the twist-connected transistors and the load capacitance. The 32-bit ripple carry adders designed with the proposed circuit technique reduce power consumption by 37% and the power-delay product (PDP) performance by 43%, as compared with the power consumption and PDP performance of the domino CMOS logic. Thus, the proposed circuit effectively reduces power consumption with the use of the new small-swing domino logic.

The generalised discrete geometric method (DGM) derived from the discrete exterior calculus is an attractive method to solve partial differential equations. Moreover, the energy complementarity of corresponding dual formulations and dual meshes has been exploited to approximate the extra solutions efficiently. Based on the thinking of duality, this reported work investigated the geometrically projective transformations or mapping operations between the interlocked dual meshes, and combined the two sets of dual formulations or algebraic equation systems into a hybrid one through the mapping matrix, which leads to a hybrid DGM featured with energy complementarity. The proposed method offers an effective and elegant solution. In particular, there is only one matrix system to be solved instead of two in the dual methods. The example of capacitance extraction of the integrated circuit, which is a typical electrostatic system problem governed by the Poisson equation, is studied. The results show that the hybrid method is available, fast and robust. Considering that geometric computation and interpolation are broadly used in physical field analyses and computer graphics, the proposed hybrid method is expected to provide a rapid approach and to greatly benefit relevant applications.

Among the image features for object recognition, speeded up robust features (SURF) have been widely implemented due to their hardware-friendly characteristics and high accuracy. However, because of adopting a fully internal memory-based architecture and a field programmable gate array having large memories for a high performance, most of them are infeasible to the application specific integrated chip (ASIC). A memory-efficient architecture for implementing SURF in ASIC by analysing the characteristics of memory accesses of SURF is presented. In addition, a strategy of dividing an entire image into multiple sub-images, processing them sequentially and overlapping each other to reduce the size of the internal memory while minimising the loss of information is proposed. The proposed architecture was implemented with 767 kb-sized internal memories and 1.2 M logic gates while processing 60 frames per second.

Prior to the large-scale deployment of any biometric system it is necessary to have a realistic estimation of its performance. In the domain of fingerprint biometrics, three-dimensional (3D) fingerprint scan technology has been developing very fast. However, there is no 3D fingerprint database publicly available for research purposes. To evaluate the matching performance of 3D fingerprints and the compatibility of 2D and 3D fingerprints comprehensively, a large fingerprint database using two commercial fingerprint sensors is established. The database consists of both 3D fingerprints and their corresponding 2D fingerprints. Several verification experiments using a commercial fingerprint identification software are carried out. The results serve as the performance criterion of the database, which will be released publicly together with the database in late 2014.

One of the serious challenges facing smartphones and other portable devices nowadays is battery life. A typical smartphone user will be running several applications on the device at any given time, and most of these applications consume plenty of energy. In fact, some of the most energy-consuming applications are those related to video conferencing and streaming. There is a lot of work to improve the energy efficiency of such applications by improving the energy efficiency of the underlying encoders. However, to accomplish that, full profiling of the encoder must be performed first. The results of profiling the High Efficiency Video Coding (HEVC) are presented. Results are presented in terms of types of assembly level instructions in every function of the encoder. Thus, depending on the environment on which the encoder is running, the energy consumed for any type of instruction can be obtained. The results show that, in an HEVC encoding process, about 48% of the instructions are memory related and about 18–20% are arithmetic operations. This result is very important for any work in energy analysis and optimisation of the HEVC encoder.

A detailed study is presented on the robustness of the Radon transform to additive white noise for the general case of a rectangular grey-level image.

A compact bandpass filter (BPF) with a wide upper stopband using a short-circuited microstrip coupled-line hairpin resonator is presented. The equivalent transmission-line circuit model is developed to analyse the performances of the proposed filter. The feeding lines are capacitively coupled to the resonator at the point which divides the fingers of the hairpin into two segments at a ratio of 1:2. As a result, the first harmonic appears at the frequency which is five times the fundamental frequency. In the final design with a grounding via hole, three transmission zeros are generated to improve the skirt effect. Therefore, a compact BPF with a wide upper stopband could be achieved. Finally, the proposed filter is fabricated to verify the design principles, and the measured results agree well with the predicted ones.

A 25.4–33.5 GHz wideband CMOS programmable multi-modulus divider with low power consumption is demonstrated. For a high operating frequency and low power consumption, a direct injection-locked frequency divider is used as the prescaler and followed directly by a dual-modulus divided-by-8/9 divider without any driving circuits. The dynamic-loading CML D flip-flips are utilised in the dual-modulus divider which further reduces the power consumption. Implemented in a 90 nm CMOS process, a frequency division from 542 to 654 in steps of 2 is achieved. Measurements show that the self-resonant frequency of the divider is 14.76 GHz, and the locking range is from 25.4 to 33.5 GHz for the total frequency division ratio at an input power of 0 dBm. The power consumption for the maximum division ratio and 0 dBm input power is 15.48 mW at a supply voltage of 1.2 V. The total chip size is 0.72 × 0.47 mm.

A coupled line schematic is proposed to build the differential filter featuring broadband, low insertion loss and good common-mode suppression. The proposed filter is composed of four quarter-wavelength coupled lines and four quarter-wavelength microstrip lines. The calculated, simulated and measured results are in good agreement with each other. The differential-mode signal can propagate with low insertion loss, whereas the common-mode signal will be suppressed below −10 dB. The fractional bandwidth of the proposed filter is 82% centred at 3 GHz.

Load impedance variations were obtained using an innovative integrated tuner at G-band. The 200 GHz load-pull measurements on a silicon–germanium (SiGe) heterojunction bipolar transistor (HBT) are presented. First, the linearity of the integrated tuner is checked. Then, the main load-pull characteristics are extracted from a 0.13 × 3 µm² emitter area SiGe HBT. The aim of this study is to provide a solution to avoid losses related to probes and commercial tuners. Thereby, from design to measurements, power setup architecture, calibration and performances at 200 GHz are performed in a non-50 Ω environment. Finally, comparisons between measurements and simulation from a high current model (HICUM) show good agreement, demonstrating the capability of the measurement approach.

The guidelines for mapping rectangular waveguide structures to substrate integrated waveguide (SIW) technology are well understood for structures with straight walls. However, the mapping of a smooth profile structure from rectangular waveguide to SIW technology is not trivial and it needs to be carefully studied. A general procedure for mapping any smooth profile H-plane rectangular waveguide structure to SIW technology is proposed. A practical example is also provided and experimentally validated.

A novel metamaterial sensor, integrated with an X-band waveguide, is proposed for high-resolution measurements of variations in the dielectric constant and/or the thickness of a superstrate layer that covers a pair of absorber unit cells. Variations in superstrate parameters are potentially caused by physical, chemical or biological factors, and can be detected by measuring the corresponding shifts in the resonance frequency of the metamaterial sensor. It is estimated by simulation results that resolution levels as good as 1.1 μm change in thickness or 0.023 absolute change in relative permittivity of the sensing layer are feasible for a 10 MHz measurable shift in resonance frequency. Simulation results obtained for the fabricated prototype are verified experimentally with good agreement.

Ultimately, the research presented will lead to the development of a microwave integrated circuit that is analogous to a field programmable gate array. An early step towards the development of this technology is presented. Specifically, a 3-port device, based on a single resonant element, namely a microstrip square patch, is described. The device operates simultaneously as a filter and an antenna. Filter performance is obtained between ports 1 and 2. Antenna performance is obtained on port 3.

A novel ultra-wideband (UWB) bandpass filter with sharp rejection and a narrow notched band is presented. This filter is designed using a multiple-mode resonator (MMR) which consists of a ring resonator and a stepped-impedance stub. The MMR has six resonance frequencies and three transmission zeros (TZs). All three TZs are close to the resonance frequencies, thus creating sharp roll-off and narrow notched bands. Different passband bandwidths and notched bands can be obtained by tuning the stepped-impedance admittance ratios. The simulated and measured results demonstrate that this simple bandpass filter has 97.3 and 30.6 dB/GHz attenuation slope at the lower and upper transition bands, respectively. The 3 dB notched band is from 5.6 to 5.8 GHz with 10.3 dB insertion loss at 5.7 GHz.

A new continuously tunable optoelectronic oscillator based on shifted dispersion-induced RF-fading is proposed and experimentally demonstrated. The design provides wideband continuously all-optical tunability by incorporating the shifted RF-fading based on a Mach-Zehnder structure in an optoelectronic feedback loop. By simply varying the path difference between the two arms of the Mach-Zehnder configuration via an adjustable variable delay line, the fundamental frequency of the oscillator can achieve extremely high and continuous tuning with a frequency upper bound dependent on the delay properties of the variable optical delay line.

A compact ultra-wideband in-phase power divider using a three-line coupled structure is proposed. The power division of the device depends on the coupling factors between the centreline and the two sidelines. For an enhanced isolation between the output ports, a 100 Ω chip resistor is connected between the ends of the two sidelines, whereas the end of the centre line is grounded. To verify the design, a prototype with 2:1 power division was fabricated and tested. The measured results validate the ultra-wideband performance with more than 12 dB return loss, more than 13 dB isolation and <0.2 dB and 4° amplitude and phase imbalances, respectively, across the band 3.1–10.6 GHz.

A buffer stripped high birefringent photonic crystal fibre based polarimetric sensor is developed for monitoring the curing process of magnetorheological elastomer (MRE) smart composite material. Using the developed sensor, different phases of the MRE curing process are clearly visible from the phase shift variation of the embedded polarisation maintaining photonic crystal fibre (PM-PCF) sensor. During the curing process, the buffer stripped PM-PCF exhibits a stress/strain induced phase shift variation from 0 to 1.98 rad. This is a significantly large phase change, which can be used to very clearly identify the different stages in the curing process. For comparison, a fibre Bragg grating sensor is also used for monitoring the internal strain during the curing process and its response does not allow one to reliably distinguish all the curing stages. The present investigation offers a simple non-destructive method to monitor the curing process of MRE smart composite material.

Three-element in-phase coherently coupled arrays of vertical cavity surface-emitting lasers (VCSELs) were fabricated using proton implantation. The arrays show excellent beam quality with a far-field divergence of 4°, while maintaining a stable in-phase mode until a maximum output power of 4 mW under continuous-wave condition. The process for the arrays is simple and the cost is low.

A drive converter for light emitting diodes is presented, which is able to add the constant current operation mode and power factor correction without any control feedback or special control algorithm while obtaining very good performances regarding high efficiency, good reliability and most importantly, low cost. The converter is based on a half bridge resonant topology, controlled with a discrete self-oscillating drive circuit, with an output parallel resonant tank. The working principle is based on the inherent current source behaviour of these kinds of converters, allowing a high power factor and low harmonic distortions. One topology uses no electrolytic high or low voltage filtering capacitors, thus obtaining a longer working lifetime for the driver. In addition, a second topology with output non-electrolytic condenser filtering for higher performances in dimming applications is proposed.

A capacitor current feedback pulse train (CCF-PT) control technique for switching DC–DC converters is proposed and applied to the control of a buck converter operating in continuous conduction mode (CCM). The analysis and experimental results show that the CCF-PT control technique can effectively eliminate the low-frequency oscillation phenomenon that exists in conventional pulse train (PT)-controlled CCM switching DC–DC converters.

A new method for three-dimensional (3D) imaging via a narrowband bistatic multiple-input–multiple-output (MIMO) radar with two uniform rectangular arrays is presented. After matched filtering and phase compensation, the method utilises the 2D cross-range images measured by the transmit and receive arrays to reconstruct the 3D image of the target. Compared with the 3D wideband monostatic MIMO imaging, lower hardware cost can be achieved since the narrowband waveforms are employed. In addition, the range alignment in wideband imaging can be avoided for the poor range resolution of the narrowband waveforms.

The well-known detail-preserving anisotropic diffusion (DPAD) for smoothing speckle noise in synthetic aperture radar (SAR) images suffers from poor despeckling performance near edges and serious blocking artefacts in homogeneous regions. The DPAD is extended to effectively alleviate the aforementioned problems by embedding the mean curvature motion controlled by an adaptive coupling function into the DPAD's diffusion equation.

The anomalous drain-induced barrier lowering (DIBL) effect of long-channel thin-film transistors (TFTs) with a light shield (LS) is investigated by two-dimensional (2D) device simulation. In long-channel TFTs with a LS, which is long enough to neglect the DIBL effect and the floating body effect, a decrease of threshold voltage (V _th) was observed at high drain voltages. The V _th lowering is due to the large potential of the LS induced by the high drain voltage, which lowers the height of the source potential barrier. It is found that the LS-induced DIBL effect can be larger as the length of the LS increases or the thickness of the buried oxide decreases.

Cu wire bonding research has exploded exponentially in the past few years. Many studies have been carried out to understand the different behaviours of Cu wire and Au wire. One of the observations on Cu wire bonding is the excessive formation of aluminium (Al) splash on the bond pad due to a higher bond force. This leads to pad peeling and bond failure resulting in poor reliability performance of Cu and PdCu wire semiconductor devices. It is known that the Al splash is influenced by the front-end pad metal process and back-end wire bond process. Reported is the design of an experiment carried out to study a few factors that could influence the Al splash. The characterisation work is implemented to understand the bond pad structure using the focused ion beam (FIB) followed by a hardness test of bond pad metallisation. Then the mechanical cross-section is taken to measure the Al splash in three different directions. The results show that Al splash can be controlled by optimising the bond pad thickness, hardness and additive for reliable Cu and PdCu wire bonding.

An off-line segmentation of a continuous-time signal is proposed, which changes at unknown transition times and where each segment is modelled as a polynomial with known order but unknown parameters. A model order method based on the maximum likelihood principle is suggested, by imposing the constraint that the complete signal is continuous, for jointly determining the number of segments, the transition times and the parameters of each polynomial. Simulation results show that the proposed approach outperforms the unconstrained segmentation.

Speaker detection is a very interesting machine learning task for which the latest i-vector challenge has been coordinated by the National Institute of Standards and Technology (NIST). A simple late fusion approach for the speaker detection task on the i-vector challenge is presented. The approach is based on the late fusion of scores from the cosine distance method (the baseline) and the scores obtained from linear discriminant analysis. The results show that by adapting the simple late fusion approach, the framework can outperform the baseline score for the decision cost function on the NIST i-vector machine learning challenge.

In IEEE 802.11 wireless local area network (WLAN) environments, handovers occur when a mobile node (client) moves from the coverage area of one access point (AP) to that of another AP. In particular, a handover in multimedia streaming settings requires a series of tasks to be executed – recognising the disconnection to the currently associated AP, searching for other APs in client visibility and so on. The time taken to perform these tasks gives rise to an interruption of service for about 6 s, which greatly decreases users’ quality of experience (QoE). To reduce service disruptions caused by handovers in IEEE 802.11 networks, a soft proactive handover scheme that exploits the received signal strength indicator (RSSI) and scalable video coding (SVC) is proposed. The proposed scheme predicts the time that a handover process is going to start using the RSSI values and receives the lightweight base layer code of the SVC-encoded video during a certain interval before the predicted handover starts. Experimental results show that the proposed scheme can minimise service interruption times during the 802.11 handover operations, thereby increasing QoE.

In orthogonal frequency division multiplexing (OFDM) signals, the usage of large size fast Fourier transforms (FFTs) reduces the guard interval percentage, and therefore increases the data throughput reducing the data overhead. In addition, for the same pilot pattern, the distance between adjacent pilots is smaller, which will improve the channel estimation. Nevertheless, up to now, they have not been considered for delivering mobile services as the inter-carrier interference (ICI) due to the Doppler effect is very critical. The main objective is to show that taking advantage of the latest improvements in error correction techniques, it is feasible to use large size FFTs for time-varying channels. Furthermore, there is also presented a theoretical estimation for quantifying the loss due to the ICI, and finally several simulation results that reinforce the idea that large OFDM symbols are suitable for mobile channels.