A tip-sensitive fibre-optic Bragg grating ultrasonic hydrophone (TSFBGUH) with high spatial resolution for measuring high-intensity focused ultrasound (HIFU) fields is reported. When measuring a HIFU field, the sensitive axis of the TSFBGUH with a flexible fibre-optic sensor holder should be in parallel with the acoustic axis of the HIFU transducer to ensure the measured ultrasound impinges on the tip of the TSFBGUH. The TSFBGUH system has been established and tested. The experimental results show that the acoustic pressure sensitivity of the TSFBGUH system is about 31.3 mV/MPa within the measurement range of 10 MHz and the noise equivalent pressure is about 10.4 kPa.

A novel transmission scheme called zero-pseudorandom noise training sequence orthogonal frequency division multiplexing (ZPN-OFDM) is proposed, where the frame structure of dual-pseudorandom noise (PN) padding time domain synchronous OFDM is modified by replacing the first PN sequence by a zero sequence. The new ZPN-OFDM system offers better energy efficiency than previous OFDM systems. The ZPN-OFDM system is tested for significant tap delay multipath channels. Simulation results show that ZPN-OFDM can provide significant bit error rate improvement as well as energy efficiency improvement.

The effect of different interferences on a victim wireless device in electric and magnetic near-field (NF) environments is investigated. Using a four-port transverse electromagnetic (TEM) cell, those NF environments are generated by varying wave impedance in the cell, which can be done by applying an external interference signal. As a measure of interference, the bit error rate performance of the victim device is chosen, which shows both NF environments have significant but distinctive interference effects on the victim device.

A unidirectional planar monopole ultra-wideband (UWB) antenna is presented. To realise unidirectional radiation, a new feed structure is implemented without modifications in the ground plane or the monopole. By using a wrench-shaped feeding structure, unidirectional radiation of the planar monopole antenna can be realised, especially at high frequencies. The antenna is built on a 20 × 30 mm FR4 substrate to cover a frequency bandwidth from 3.1 to over 14 GHz for a voltage standing wave ratio ≤2.

Explicit formulae and complexities of bit-parallel GF(2 ⁿ ) squarers for a new class of irreducible pentanomials xⁿ + x^{n− 1} + x^k + x + 1, where n is odd and 1 < k < (n − 1)/2 are presented. The squarer is based on the generalised polynomial basis of GF(2 ⁿ ). Its gate delay matches the best results, whereas its XOR gate complexity is n + 1, which is only about two thirds of the current best results.

A passive frequency compensation method is presented for the first time, which can be applied to two/multi-stage operational transconductance amplifier (OTA) designs, to achieve high gain-bandwidth (GBW) and high slew-rate with no increase in the overall power consumption. A nulling resistor with series compensating capacitor is applied in the first stage and extends the GBW by introducing a left-hand-plane (LHP) zero. This design is implemented in a 0.18 μm CMOS process and the measured results show a GBW of 100 MHz and average SR of 60 V/μs with a power consumption of 1.7 mW. A high figure of merit (FoM) of 94.7 GHz pF V/μs/mA is achieved.

A frequency-interleaving-based multichannel analogue-to-digitial converter (ADC) with mismatch compensation is presented, which is immune from the time skew problem that exist in the time-interleaved ADC. The channel mismatches, such as bandwidth mismatch, gain mismatch, offset mismatch and filter bank mismatch, are addressed and modelled in the reconstruction optimisation. A prototype of a four-channel 1 GS/s 12 bit frequency-interleaved ADC (FI-ADC) is designed to demonstrate the mismatch compensation. Simulation results show that the mismatches in the FI-ADC can be compensated effectively.

A compensated charge pump for use in phase-locked loops (PLLs) is presented, which reaches several of the desired design goals for this type of circuit. The measured mismatch between the source and sink currents is below 2.1% for a large output voltage headroom of 83.3% of the supply, while still having a high output resistance of 140 kΩ. This behaviour is reached with a novel dual compensation method. The circuit was implemented in a 180 nm CMOS technology using a 3 V supply.

In adaptive processing applications, the design of the adaptive filter requires estimation of the unknown interference-plus-noise covariance matrix from secondary training data. The presence of outliers in the training data can severely degrade the performance of adaptive processing. By exploiting the sparse prior of the outliers, a Bayesian framework to develop a computationally efficient outlier-resistant adaptive filter based on sparse Bayesian learning (SBL) is proposed. The expectation–maximisation (EM) algorithm is used therein to obtain a maximum a posteriori (MAP) estimate of the interference-plus-noise covariance matrix. Numerical simulations demonstrate the superiority of the proposed method over existing methods.

The noise characterisation of differential circuits is considered. A new method for the determination of the differential mode noise power at the output of these circuits is presented. It is demonstrated that this differential noise power depends not only on the output noise powers but also on the correlation of the output noise waves. An analytical expression of this correlation in terms of the S-parameters and the output noise powers is determined. Based on the presented theory, a fast and simple technique is developed for the noise figure measurement of differential circuits.

The influence of the body layout on the charged device model (CDM) failure site and the robustness of the input buffer is explored. The failure analysis results confirm that the gate oxide is damaged. The failure site can be moved from the region above the channel to the overlap region between the source and the gate once the body layout is cut from a ring into a small segment, providing direct evidence demonstrating that the CDM current flows through the gate oxide via the body and the source of the transistor, since both connect to the V _ss bus line. Otherwise, changing the body layout of the input buffer transistor does not vary the failure location.

A novel method to build a scale-free network model for template matching is proposed. The scale-free network model of the template is produced by a kernel histogram. Moreover, those special points that have much larger effects than other points can be selected by a matching algorithm. Based on the scale-free network model, the matching is implemented by minimising the sum of absolute differences. The proposed algorithm can match the potential object of varying scale in a clutter background. To the best of the authors' knowledge, this is the first template matching algorithm which uses the scale-free complex network to model template matching.

A regional hidden Markov model (RHMM) for automatic facial expression recognition in video sequences is proposed. Facial action units are described by RHMMs for the states of facial regions: eyebrows, eyes and mouth registered in a video. The tracked facial feature points in the spatial domain form observation sequences that drive the classification process. It is shown that the proposed technique outperforms other methods reported in the literature for the person-independent case tested with the extended Cohn-Kanade database.

The new high-efficiency video coding (HEVC) standard is becoming popular owing to its excellent rate-distortion performance especially for emerging high-resolution applications. In HEVC more flexible coding options and partitioning types are provided for prediction units (PUs) and consequently motion estimation (ME) is more involved than previous video-coding standards. The existing fast ME algorithms, including the test zone search provided in the HEVC reference software, cannot generate high-quality video with reasonable computational complexity. A new fast integer-pixel ME algorithm for HEVC is presented. Starting with the initial motion vector obtained by the advanced motion vector prediction, the proposed directional search extends three search paths from the initial motion vector and considers the highly probable horizontal or vertical movement. Compared to the test zone search, the proposed method saves, on average, 60% time in integer-pixel ME with negligible rate-distortion degradation.

A novel method to detect the most salient object from an image is proposed. Saliency cues such as spatial colour distribution and the saliency prior are extended to super-pixels and are integrated to compute the final saliency. The super-pixels are generated in multiple scales so that the proposed method is adaptive to objects of different sizes. Moreover, to solve the problem that many saliency detection algorithms rely on local evidences, it is proposed to propagate the saliency information based on the spectral affinities of super-pixels. Experimental results have proven that the proposed method achieves discriminative saliency maps and outperforms the state-of-the-art methods.

A novel method for sparsity estimation by means of the divide and conquer method is presented. Also, the underestimation and overestimation criteria for signal sparsity is proposed and proven. Then the blind-sparsity subspace pursuit (BSP) algorithm for sparse reconstruction is discussed. Based on the estimation, BSP combines the support set and inherits the backtracking refinement that attaches to compressive sampling matching pursuit (CoSaMP)/subspace pursuit (SP), whereas the pruning process of BSP is improved by introducing the weakly matching backtracking strategy. With the said improvement, there is no need for BSP to require the sparsity as an input parameter. Furthermore, experiments demonstrate that the divide and conquer method is effective for sparsity estimation when the isometry constant is known. In addition, the simulation results also validate the superior performance of the new algorithm and show that BSP is an excellent algorithm for blind sparse reconstruction and is robust when the estimate of sparsity is not perfectly accurate.

A novel quad-band bandpass filter with individually controllable centre frequencies and bandwidths using a folded stepped-impedance resonator (SIR) is proposed. The new filter that centres at 2.4, 3.3, 4.1 and 5.2 GHz has a measured passband insertion loss of no more than 1.6 dB, and has a miniature circuit size of 0.448λ _g × 0.027λ _g. The presented filter is fabricated and tested, and the experiment demonstrates the new design. The new quad-band bandpass filter has compact and simple circuit topology, good performance of low passband insertion loss and transmission zeros, and greatly reduced circuit size compared with the relative reports.

The first demonstration of a rolled-up InAs quantum dot tube photodetector is reported, which is fabricated by the selective release of self-organised InAs/GaAs quantum dot heterostructures from the host substrate. The device exhibits a responsivity of ∼66 mA/W and an external quantum efficiency of ∼8% under 1064 nm excitation at 300 K.

An active single balanced down-conversion mixer is implemented using InAs nanowire metal oxide semiconductor field effect transistors (MOSFETs) as both active devices and passive resistive loads. Circuits with 6 dB low-frequency voltage gain and a 3 dB bandwidth of 2 GHz are measured for a DC power consumption of 3.8 mW from a 1.5 V supply. The circuits are fabricated using contacts made with 12 μm-line-width optical lithography.

The 25 Gbaud/s 4-level pulse amplitude modulation (4-PAM) of a 1.3 μm electroabsorption modulator integrated with a distributed feedback (DFB) laser is demonstrated for the first time. The linearities of the electroabsorption DFB (EADFB) laser and the directly modulated laser are evaluated to investigate the applicability of the PAM format to these devices.

Optical-layer service-differentiation (Diff-Serv) and load-balancing abilities are achieved by collaborative implementation of OpenFlow (OF) switches and intelligent optical adapt unit (IOAU) prototypes. Experimental demonstration shows that by adapting OF-switches as edge routers, optical-layer Diff-Serv can be realised by mapping services of different priorities into different lightpaths. Thus, optical fibre is service-aware rather than merely a blind pipe. In addition, the load-balancing function of the IOAU can be used to gain reasonable wide area network (WAN) link utilisation. By combining these two abilities, many interesting experimental scenarios and meaningful upper layer applications can be devised.

There is a desire to overlay future optical access networks onto legacy passive optical networks (PONs) to provide increasingly advanced services by filling empty wavelength bands of legacy gigabit rate PONs. Nonlinear Raman crosstalk from new wavelengths onto legacy RF video services (1550–1560 nm band) and onto the legacy digital downstream at 1490 nm, however, can limit the number and the launch power of new wavelengths. As an example, straightforward physical-layer adjustments at the optical line terminal that increase the number of new, 10 Gbit/s channels launched in the 1575–1580 nm band by a factor of 16 without increasing the Raman penalty on the video signal are illustrated. A physical-layer (RF) filter modifies the on–off-keyed signal feeding each 10 Gbit/s transmitter, suppressing the RF Raman crosstalk on the video signal by 9 dB while incurring a power penalty on each 10 Gbit/s link of <0.5 (2.0) dB with (without) forward error correction. The previous Raman mitigation work used non-standard line-coding to shape the 10 Gbit/s electrical spectrum. In addition, polarisation-interleaving of new wavelengths lowers the worst-case RF DC crosstalk by ∼3 dB in fibres and it limits and stabilises DC crosstalk in low polarisation mode dispersion fibre links.

A new n-i-p-n heterostructure InP(100) optical modulator is proposed. By utilising the crystallographic orientation dependence of the electro-optic Pockels effect and electric field direction, the device, which is formed along the [011] waveguide stripe direction, has a lower half-wave voltage than one formed along the [01̄1] direction. The half-wave voltage of a [01̄1] direction phase modulator was 4.8 V, whereas that of the [011] direction was 2.9 V.

Narrow linewidth terahertz (THz) generation using a cascaded Brillouin fibre laser structure and a unitravelling carrier photodiode is investigated. Using two distributed feedback lasers separated by > 1 THz with 1 MHz initial linewidth, the use of the cascaded Brillouin laser greatly increases the linewidth reduction factor compared to a single Brillouin laser structure. The linewidth of the realised THz source is found to be < 100 Hz at 1014.7 GHz without the use of any active stabilisation of the laser cavity or any microwave reference.

A novel exclusive OR circuit with a simple configuration for binary signals, which is composed of a balanced photodetector and an intensity modulator, is proposed. Two input optical signals into the balanced detector produce an electrical signal to drive the modulator. The modulator outputs an optical exclusive OR signal of the two input optical signals. The primary operation is demonstrated by evaluating the circuit with 10 Gbit/s signals.

The change in shape of the spatial spectrum, which is a result of the interaction of a focused laser beam with a phase step structure (PSS), is investigated. As a laser beam passes through a PSS, a spatial spectrum of radiation in the form of two peaks with a deep gap in between is generated. The change in the peaks’ structure as the PSS moves relative to the optical axis of the laser beam is studied in detail. On the basis of the experimental results, a new scheme for measuring small linear and angular deviations is proposed.

A simple technique to suppress self-pulsing behaviour in a fibre laser employing a two-mirror Fabry-Pérot external feedback cavity is reported. Feedback provided by the external Fabry-Pérot cavity enforces the fibre laser to oscillate in the selected longitudinal modes, resulting in robust laser operation without self-pulsing. This technique has been successfully applied to a double-clad Yb fibre laser, yielding a stable continuous-wave output of up to 9.8 W at 1050 nm. The advantages of this technique and the prospects of further improvement are discussed.

A new particle-based distribution truncation method with a duration-dependent hidden semi-Markov model for non-intrusive appliance load monitoring is presented. Unlike earlier works, the approach keeps track of a set of states without prematurely pruning away intermediately ranked states. It also enables appliance state duration characteristics to be incorporated in a straightforward manner. Results show that the approach outperforms both the Viterbi algorithm and conventional particle-filtering methods.

A novel high pressure sodium (HPS) lamp model is proposed. The proposed model is particularised for 150 W HPS lamps, providing a powerful tool for simulating the behaviour of such lamps operating with low-frequency electromagnetic ballasts or high-frequency switching electronic ballasts. Simulations and experimental results are provided for verification of the model. The model can be easily extended to other rated wattages and kinds of discharge lamps.

To reconstruct the interior layout of a building from a through-the-wall radar image, a method based on a minimum spanning tree (MST) which comes from graph theory is proposed. The traditional MST method is introduced and the traditional method is improved by applying the MST model with restricted conditions to solve the reconstruction problem when there exist interference targets in a building. Anechoic chamber measurements are carried out to demonstrate the suitability and efficacy of the MST-based method.

A novel structure of the reverse-conducting insulated gate bipolar transistor (RC-IGBT) is proposed. The structure is connected anti-parallel with a PNP and an NPN transistor, which are in a collector-base short-circuited configuration. Bidirectional conduction capability with no snapback can be obtained by this structure and the turnoff speed can be much improved. The structure can work in two different modes in a reverse-conducting state: a diode mode and a thyristor mode. Two-dimensional numerical simulation results show that the novel RC-IGBT reduces the turnoff loss (E _off) by 26.4 and 37.7% for the thyristor mode and the diode mode, respectively, and has no current non-uniformity compared with the conventional RC-IGBT.

A multi-stage thin film transistor (TFT)-based active pixel sensor (APS), capable of successfully detecting small impulses of charge resulting from incident alpha particle strikes, is presented. Detection of alpha particles is important in the field of neutron detection, where fully integrated thin-film-based detectors are an attractive alternative to conventional ³He-based proportional counters owing to their low-cost and large-area scaling capability, combined with the use of readily available materials. A typical TFT process, however, produces only N-type devices with low electron mobilities – making high-gain CMOS amplifier designs unfeasible. The disadvantages of using a TFT-only APS design are mitigated by cascading multiple low-gain TFT amplifiers, which results in a higher overall pixel gain – subsequently allowing for the successful detection and readout of alpha particle strikes. Presented is a new APS fabricated in an indium gallium zinc oxide TFT process is presented, and successful initial alpha response measurements are reported.

Amorphous indium–gallium–zinc-oxide thin-film transistors (a-IGZO-TFTs) with the LaAlO₃/ZrO₂ gate dielectric stack employing a novel atmospheric pressure plasma jet process that results in small subthreshold swing and low threshold voltage are proposed and fabricated. The influence of post-deposition annealing (PDA) temperature on LaAlO₃/ZrO₂ gate dielectric stack and device performance was investigated. The equivalent oxide thickness of the LaAlO₃/ZrO₂ dielectric stack decreases from 11.5 nm without annealing to 7 nm after a 500°C annealing was applied. The LaAlO₃/ZrO₂/a-InGaZnO TFT with a 500°C annealing exhibits a small subthreshold swing of 77 mV·dec⁻¹, a high field-effect mobility of 9 cm²·V⁻¹·s⁻¹ and an excellent current ratio of 1.8 × 10⁷, which could be attributed to the improved gate dielectric quality by the PDA. The LaAlO₃/ZrO₂/a-InGaZnO TFTs with excellent gate control ability allow the device to operate at a low operating voltage with low power consumption.

A non-iterative, closed-form solution to the problem of statistically modelling the monotonic relationship between a dependent variable and two independent variables through a probability conservation principle is introduced.

Experimental fading measurements were performed in Cadiz Bay, Spain, for a variety of operational scenarios over the sea at the unlicensed 5.8 GHz frequency band. Measurements are based on continuous wave (CW) transmissions with both the transmitter and the receiver installed in typical low-height maritime platforms, such as oceanographic buoys, military ships and boats. Based on the measurements, large-scale and small-scale fading statistics are characterised by cumulative distribution functions (CDFs) and key wireless channel parameters are estimated and discussed. Results show, first, that large-scale fading can be modelled using classical log-normal path-loss models and, secondly, that small-scale fading statistics fits the extreme value distribution (EVD) function when they are expressed in decibel units. This study can be used for practical planning of wireless communications in maritime applications and as an experimental basis for further simulation works.

A comparison of relay power minimisation subject to received signal-to-noise ratio (SNR) at the receiver and SNR maximisation subject to the total transmitted power of relays for a typical wireless network with distributed beamforming is presented. It is desirable to maximise receiver quality-of-service (QoS) and also to minimise the cost of transmission in terms of power. Hence, these two optimisation problems are very common and have been addressed separately in the literature. It is shown that SNR maximisation subject to power constraint and power minimisation subject to SNR constraint yield the same results for a typical wireless network. It proves that either one of the optimisation approaches is sufficient.

In cognitive radio, spectrum sensing is a challenging task. Proposed is a new spectrum sensing method based on the goodness of fit test of the energy of the received samples with a chi-square distribution. The test statistic is derived and the performance of the proposed method is evaluated by Monte Carlo simulations. It is shown that the proposed spectrum sensing method outperforms the conventional energy detection method without increasing the complexity of the sensing.