A new ultra-wideband (UWB) rectangular dielectric resonator antenna (DRA) with band-stop performance is proposed. Two symmetrical short-circuited strips together with a slot etched in the feeding patch are introduced to form the notched band. The design principles of the proposed methods are described in detail. The measured result demonstrates that the proposed DRA achieves an UWB bandwidth from 3.6 to 12 GHz for a voltage standing wave ratio <2 with a notched band from 5.1 to 6.0 GHz.

A triple-band planar antenna with a compact radiator is proposed for 2.3/3.5/5.5 GHz WiMAX and 5.2/5.8 GHz WLAN applications simultaneously. The proposed antenna consists of an inverted-L (IL)-shaped radiating element and a parasitic element in the ground plane to generate three resonant modes for triple-band operations. Each of the three resonant bands can be tuned separately to cover other wireless applications also. Owing to the coupling of the IL-driven element and the parasitic element, a compact radiator of 10 × 17.3 mm² is realised for triple-band operations. Some key parameters affecting the antenna performance have been analysed using computer simulations. To validate the simulation results, the prototypes of the proposed antenna are fabricated on an inexpensive FR-4 substrate and tested. Good radiation characteristics of the proposed antenna have been obtained. The simulated and measured results are in good agreement.

To extend the Courant-Friedrichs-Lewy (CFL) limit, a discrete wavelet transform (DWT) is incorporated into the finite difference time domain (FDTD) scheme. With the Mallat algorithm for the decomposition and reconstruction of the electromagnetic components, the unstable spatial modes can be efficiently filtered out. Consequently, the original strict CFL limit of the FDTD can be significantly relaxed, and much execution time can be saved. The performance and versatility of the proposed method is demonstrated by the numerical examples.

A novel slotted cavity antenna based on substrate integrated waveguide (SIW) technology using TE₃₃₀ mode is presented for the first time. The SIW-based cavity operating at TE₃₃₀ mode is simply fed by a coaxial probe. Energy is coupled out of the cavity by a 3 × 3 slot array etched on the top surface of the cavity. An antenna prototype operating at WLAN 5.8 GHz band fabricated with standard printed circuit board (PCB) process on a single substrate is exemplified to validate the proposed concept. The overall volume of the antenna is 1.6λ ₀ × 1.6λ ₀ × 0.029λ ₀. Measured results show that the antennas achieve a bandwidth of 4.7% for 10 dB return loss and gain of up to 13.6 dBi. The proposed antenna features low profile, high gain, ease of fabrication and high efficiency, which makes it a good candidate for low-cost mass-production.

A smart antennas assisted wideband spectrum sensing algorithm for cognitive radios is presented. The proposed method operates simultaneously over the total wideband channels rather than one single channel each time. In this approach, the wideband spectrum sensing issue is transformed into estimating the number of occupied channels based on the Hannan-Quinn criterion, and then determining the occupancy status for each channel by the sample power. Neither noise power estimation nor prior knowledge of the primary user signal is required, making the proposed algorithm robust to noise uncertainty and suitable for blind detection. Simulations are presented to validate the benefits of this approach and the results show that this scheme is superior to the existing sensing algorithms.

The learning of nonlinearly separable functions in cascaded memristor crossbar circuits is described and the feasibility of using them to develop low-power neuromorphic processors is demonstrated. This is the first study evaluating the training of memristor crossbars through SPICE simulations. It is important to capture the alternate current paths and wire resistance inherent in these circuits. The simulations show that neural network learning algorithms are able to train in the presence of alternate current paths and wire resistances. The fact that the approach reduces the area by three times and power by two orders of magnitude compared with the existing approaches that use virtual ground opamps to eliminate alternate current paths is demonstrated.

A novel direct-driven and portable exoskeleton robotic system for the hand is proposed. The system design is based on the multi-parametric optimisation procedure, which considers isotropy, dexterity and exertion of perpendicular forces on the finger phalanges. Actuators for the proposed device were selected based on results of experiments with users having different hand sizes. These experiments measured various parameters including average and maximum force exertion levels of a human hand. The experimental results were used to realise the mechanical design and to develop a prototype. The device can exert force levels (of 45 N) beyond any existing hand exoskeleton. Preliminary trials carried out on the fabricated prototype dictate efficacy and potential of the proposed system.

A high sensitivity radiofrequency (RF) probe dedicated to contactless dielectric characterisations is presented. A method for the impedance measurement of a distant RF resonator is first proposed. The method is evaluated as a function of the measurement distance starting from experiments. The obtained results enable assessment of the accuracy of the method and optimisation of its implementation.

Oversampled converters based on voltage controlled ring oscillators are an attractive solution because of their digital implementation and simplicity. However, the voltage-to-frequency conversion of ring oscillators displays a poor linearity. Replacing the ring oscillator by a pulse frequency modulator (PFM) that provides improved linearity at the expense of feedback and analogue amplification is proposed. Compared to the equivalent continuous time sigma–delta modulators, the PFM may be more tolerant to circuit impairments. In addition, the output data of the proposed architecture is a multibit sequence through the use of a time-to-digital converter TDC instead of a Flash quantiser or a multibit digital-to-analogue converter. A high dynamic range can be achieved without severe constraints on analogue mismatch or clock jitter.

A new tri-level switching method for successive approximation register (SAR) analogue-to-digital converters (ADCs) is presented. The proposed switching method enhances the efficiency of digital-to-analogue converter switching energy by 93.7% and achieves a 75% reduction in the total capacitor size, compared with the conventional SAR ADC. In addition, the accuracy of the proposed SAR ADC has no dependency on the accuracy of the mid-level reference voltage (V _cm) except in the least significant bit, and the common-mode voltage at the input of the comparator will remain approximately unchanged. Analytical calculations and behavioural simulation results are provided to demonstrate the effectiveness of the proposed switching scheme.

To enhance the performance in IIR system identification scenarios, a hybrid combination of FIR and IIR adaptive filters (AFs) via a supervisor that senses which one is performing best is proposed. The FIR-LMS AF is short, providing fast and robust convergence, whereas the IIR-LMS AF is slow but accurate. The stagnation effect caused by the different convergence rates is tackled through cyclic weight transfers FIR → IIR, which also ensure good tracking properties. A design technique for the transfers cycle length is proposed, providing good convergence while keeping computational cost low.

The method of quasi-delay-insensitive logic synthesis using look-up tables (LUTs) is described. It is shown that the dual-rail sum-of-minterm function hazard-free implementation can be done using a single LUT. Namely, instead of the conventional approach based on a DIMS representation where each minterm is implemented on a C-element, the whole sum-of-minterm function is mapped into the single C-element. For Boolean network implementation, it is proved that a fork with branches to different nodes is not required to be isochronic. It simplifies technological synthesis and allows using existing placement and routine methods and tools supposed for synchronous logic. Compared to the conventional approach, the method reduces significantly circuit complexity (in terms of the number of LUTs).

A threshold-voltage-difference-based CMOS voltage reference topology derived from the basic current bias generator is proposed. The implementation in the GSMC 0.18 μm process demonstrated that a precise voltage of 516.3 mV can be generated with a minimal temperature coefficient of 4.3 ppm/°C. The reference consumes a current of 1.9 μA with a minimum supply voltage of 1.4 V. The line regulation is 0.075%/V at room temperature. It only occupies 0.013 mm² without any area optimisations because of its simple structure. Also, due to its special compound structure, the circuit can generate both a stable voltage and a relatively temperature-independent current.

An efficient intra coding method is presented for depth coding, namely edge skip. In the proposed method, the depth edge macro-block (MB) is skipped without coding. At the decoder side, the edge MB is reconstructed with the reference samples of the adjacent left and above lines, and the associated partitioning information. The partitioning information is derived from the co-located area in the corresponding reconstructed texture image by a k-means clustering. Experimental results demonstrate that the proposed method significantly improves the coding efficiency both objectively and subjectively.

A no-reference objective metric for image quality assessment by integrating the topographic independent components analysis into feature extraction is presented. By taking the topographic relationship among the initially independent features into consideration, it extracts the features of more sparsity or independency which is essentially related to inherent quality. Evaluation results demonstrate that the proposed metric is able to predict the image quality accurately across various distortion types.

A novel approach to detect an infrared small target in the compressive domain is presented. First, the original infrared image is projected on a sensing matrix to obtain the measurement vector. Then the target and the background are recovered simultaneously from the measurements based on low-rank and sparse matrix decomposition. Experimental results indicate that the proposed method not only works well under different complex backgrounds with less data storage, but also outperforms some existing methods in both subjective and objective qualities.

The need to support various recognition applications on energy-constrained mobile computing devices has steadily grown. Exploiting common characteristics of recognition algorithms, a very energy-efficient multiplier that can support a runtime trade-off between computational accuracy and energy consumption is proposed. Compared to a precise multiplier, the proposed multiplier consumes 11.6×–3.2× less energy per multiplication while achieving 82–99% of the computational accuracy with negligible negative impact on recognition accuracy for three different recognition applications.

An occlusion-adaptive bidirectional motion compensation method using pixel-based motion vectors that reduces ghost artefacts due to occlusion is proposed. The proposed method constructs each pixel in the intermediated frame as a weighted average of its motion-compensated pixel candidates. The weighting factor for each pixel candidate is determined adaptively by utilising a temporal motion consistency metric. Moreover, a local support window mechanism is presented in bidirectional interpolation to enhance the intensity transition smoothness among neighbouring pixels. Experimental results demonstrate that the proposed method can effectively improve the quality of the interpolated frames without annoying visual artefacts.

In image dehazing, the existing transmission estimators bring out the halo artefact at boundaries unless they adopt a refinement procedure with a high computational complexity. How the existing transmission estimation methods suffer from the halo artefact at the boundaries are analysed and it is found that the elaborate, high computational refinement procedure to remove the halo effect are excessive for dehazing. On the basis of the above-mentioned analysis and finding, a simple segmentation logic was embedded in an existing transmission estimator, which is sufficiently accurate for dehazing. The experiment verifies that the proposed method significantly reduces the halo artefact without requiring any refinement procedure.

An improved combining method is proposed for constructing quasi-cyclic low-density parity-check (QC-LDPC) codes with large girth and few short cycles. Large girth QC-LDPC codes can be obtained by carefully designing one component code with large girth. By properly designing the other component codes, a lot of QC-LDPC codes with very few short cycles can be designed. Simulations show that compared with Chinese remainder theorem based QC-LDPC codes and progressive edge-growth based QC-LDPC codes, the proposed QC-LDPC codes have much less short cycles and better performance.

Different signals from the various sensors of the same scene form an ensemble. Distributed compressed sensing (DCS) rests on a new concept called the joint sparsity of the ensemble. JSM-1 is a model that describes the joint sparsity by one dictionary. Previously, the generalisation of JSM-1 was proposed where the signal ensemble depends on two dictionaries. Its compressed sensing (CS) version is considered: generalised DCS (GDCS). Instead of using random projections (random Gaussian (rGauss)), a gradient method with Barzilai–Borwein stepsize (GBB) is developed to optimise the projections in the GDCS. It enhances the reconstruction performance of the GDCS. It is verified by some experiments on the synthesised signals.

A method for optimisation of IEEE 802.3az energy-efficient Ethernet networks is proposed. To overcome the timing limitations imposed by the standard, the packets are stored in a buffer until the criteria for its emptying are met. It is shown that this approach leads to greater energy savings while guaranteeing the desired level of quality of service, expressed by a maximal packet delay.

A broadband monolithic microwave integrated circuit (MMIC) quadrature phase shift keying (QPSK) modulator with low amplitude and phase errors is proposed. The presented modulator adopts two wideband reflection-type binary BPSK modulators, each consisting of a modified Lange coupler with additional λ/4 transmission lines, varactor diodes, inductors and resistors. The proposed QPSK modulator is implemented in 0.15 μm GaAs low-noise pHEMT process. The measurements show an error vector magnitude and a demodulated I/Q offset <5.8% root-mean-square and −16.1 dB, respectively, from 18 to 26.5 GHz.

A compact microwave phase shifter was designed and fabricated using highly anisotropic liquid crystals (LCs). It comprises a thin LC layer between a ground plane and a directly coupled and inverted microstrip line. The proposed folding configuration is beneficial for size reduction. Both simulation and experimental results confirm the compact size devices with reasonably good performance.

A fixed-tuned low conversion loss full E-band seventh-harmonic mixer is presented. Mixing diodes are arranged as a single balanced configuration so that the RF signal is only mixed with LO odd harmonics and the idle mixing products are reduced by half. By replacing the traditional stepped impedance resonator filter with a newly developed two-stage compact microstrip resonating cell filter, the length of the filter has declined 64%. Measurement results indicate that the conversion loss of the seventh-harmonic mixer is 21.5 ± 5 dB in the frequency range of 60–90 GHz.

The 3 dB bandwidth of a low-noise amplifier (LNA) is increased by 23% from a range of 1–6.7 GHz to a range of 1–8.25 GHz through digital assist. The LNA has a multi-stage topology and the gate bias voltages are dynamically optimised in real-time to obtain the best gain and noise figure as a function of the signal input frequency.

A 43 Gbit/s receiver optical subassembly (ROSA) module using a compact transistor outline-can (TO-can) package has been developed and successfully demonstrated at transmission over a 2 km single-mode fibre. The electrical interface of the ROSA is made of an impedance-matched flexible printed circuit board (FPCB) which is orthogonally connected to the TO-can package. The measured 3 dB optical-to-electrical bandwidth is ∼31.5 GHz and the receiver sensitivity is <−8.4 dBm at an extinction ratio of 8.2 dB and a bit error rate of 10⁻¹².

A novel lightpath rerouting technique is proposed, allowing data lossless rerouting without requiring additional optical transponders. Data lossless rerouting effectiveness is demonstrated considering a 112 Gbit/s polarisation multiplexed quadrature phase shift keying lightpath and coherent receiver.

The first compact electroabsorption modulators integrated with distributed-feedback (EADFB) laser array module using flip-chip interconnects have been fabricated for a 400 Gbit/s transceiver. Eight 50 Gbit/s EADFB lasers and an optical multiplexer were monolithically integrated on one chip in an area of only 3.2 × 4.8 mm. The flip-chip interconnects provide a higher modulation bandwidth. Clear eye opening was achieved for all eight lanes under 50 Gbit/s operation.

An innovative 10 Gbit/s single mode optical transmitter with the capacity of error-free transmission is demonstrated in the range of 0–100 km with constant biasing conditions by using a quantum dash directly modulated laser. A commercially available etalon filter is used as a passive optical filter to achieve penalty-free transmission with a dynamic extinction ratio >6 dB over a large range of fibre spans.

The operation of an extended power budget long reach access network is experimentally demonstrated using commercially available small form pluggable directly modulated transmitters and a simplified coherent receiver free from digital signal processing and phase-locked loops. An ad-hoc choice of photodiode bandwidth allows no penalty compared with external modulation based transmitters.

The possibility of a kind of industrial-grade X7R type multilayer ceramic capacitor used as an actuator is studied. By applying a DC bias voltage, the ceramic capacitors exhibit a large converse piezoelectric effect which can be used for actuating applications. The experiments show that the capacitor's thickness changes rather linearly with a voltage applied on it. Three multilayer ceramic capacitors were selected to be studied. A hysteresis <1.8% and a nonlinearity <2.0% between the displacement and the driving voltage were observed for a 10 μF capacitor over a frequency range of 0.1–20 Hz and a temperature range of 15–35°C.

Channel waveguides were written in a fluoroindate bulk glass containing thulium, with a femtosecond laser operating at 800 nm, 100 fs pulses and a repetition rate of 1 kHz. Formation of waveguides occurred for average powers from 1 to 8 mW (corresponding to energies of 1–8 μJ) and scan velocities in the range of 0.1–4 mm/s. Passive optical characterisation included visual inspection by an optical microscope, insertion loss and mode profile. Active characterisation was performed by co-propagating pumping in a dual-pump scheme that included an 808 nm and a 1054 nm laser diode for an efficient inversion of the ³H₄ level, which is responsible for stimulated emission in the 1460–1530 nm spectral range. Preliminary tests show a net gain of 2.5 dB at 1487 nm, for straight waveguides 1 cm long. Applications include the fabrication of lossless components working in the S-band region of the optical communication spectrum.

A saturable-absorber-free vertical-external-cavity surface-emitting laser is presented which is harmonically modelocked. Modelocking is initiated via fine-tuning of an aperture which is placed near one of the cavity's end mirrors. Fundamental modelocking is observed along with the second and third harmonic operations for increased optical pump powers. The system features pulse durations penetrating the femtosecond regime at a wavelength of 1014 nm.

Compared with a pulse-width modulated voltage-mode controlled switching converter, a constant on-time (COT) controlled switching converter has extensive industry application due to its fast transient response. However, the conventional COT controlled switching converter has poor output-regulation accuracy. A new control method that provides both fast transient response and high output-regulation accuracy for switching converters, called dual COT control, is proposed. The analysis results are verified by circuit simulation.

Passive radars utilising illuminators of opportunity are being actively studied in the field of radar. In the last few years, many illuminator sources have been employed for passive radar applications. However, there have been no published results on the use of the long-term evolution (LTE) signal as a novel source for passive radar applications. For the first time an experimental investigation into the feasibility of LTE-based passive radars for detecting a moving target is presented. A theoretical analysis was conducted on a captured LTE signal in the atmosphere. This was then followed by a field experiment. The preliminary results show that the LTE signal is capable of being an illuminator for passive radars.

ALOS PALSAR has provided a five-year archive of systematic global tropical forest coverage, released as slope-corrected and ortho-rectified 50 m mosaic products by JAXA, which are of great help to monitor forest changes. Based on the mosaics, a map of deforestation between the years 2007 and 2008 is built for Riau province, Indonesia, achieving a detection rate of over 86% at a false alarm rate of 20%, calculated by treating independent World Wildlife Fund (WWF) 2007 and 2008 maps as a reference. Non-forest is discriminated from forest by thresholding the HH/HV ratio in the PALSAR data. Deforestation is then estimated by detecting non-forest in the 2008 synthetic aperture radar (SAR) image (acquired close in time to the WWF 2008 reference map) within the region identified as natural forest in the WWF 2007 reference map. This reduces the errors caused by comparing the change detection between the bi-temporal SAR images with the WWF reference maps that are temporally mismatched with the SAR data, leading to more realistic estimates of the ability of PALSAR to detect deforestation than was previously reported.

A linear frequency-modulated continuous-wave (LFMCW) radar with a simplified single homodyne channel is proposed and developed in the 0.22 THz band. The transmitter employs direct digital waveform synthesiser technology to obtain a reliable fast scanning LFMCW source, the scanning speed of which is 40 µs with an instantaneous bandwidth of 14.4 GHz. To realise the nonlinearity calibration and coherent imaging, the quadrature signal is recovered by a Hilbert transform receiver to obtain the phase information of the return wave. The radar operates using the real-aperture imaging method and uses a lens to focus the Gauss beam which determines the azimuth resolution. The results of the pulse compression and imaging experiments verify the effectiveness of the proposed imaging scheme in the 0.22 THz band. The radar can be used for non-destructive testing and security checks.

A basis-based speaker adaptation technique is proposed, where basis vectors are derived using two-dimensional principal component analysis (2DPCA) and the speaker weight for the target speaker is constrained in the space of training speaker weights. During adaptation, the speaker weight that is derived in the maximum-likelihood framework is constrained by projecting the weight into the space of the weights of training speakers. In the experiments, the proposed approach shows performance improvement over the unconstrained 2DPCA-based approach.

The model-based expectation maximisation source separation and localisation (MESSL) algorithm is enhanced through the integration of robust clustering based on the Student's t-distribution. This heavy-tailed distribution, as compared with the Gaussian distribution used in MESSL, can potentially capture in a better manner the outlier values in the univariate parametric modelling of the time–frequency (T–F) points and thereby lead to more accurate probabilistic masks for source separation. In particular, the Student's t-distribution is exploited in modelling the interaural phase difference (IPD) in order to represent in a better manner the uncertainties introduced by the statistical non-stationarity of the speech signals and the associated small sample length effects. Simulation studies based on speech mixtures formed from the TIMIT database confirm the advantage of the proposed approach in terms of the signal to distortion ratio (SDR).

The effect of the imperfect channel state information (CSI) on the system performance of radio resource management is addressed for a downlink OFDMA system. Differing from the previous works, it is shown that the imperfect CSI introduces a signal-and-power dependent noise term, and then a new method is proposed to evaluate the utility function. Numerical simulations show that the signal-and-power dependent noise yields a non-negligible degradation to the system performance.

A new strategy to reduce data delivery delay for vehicle-to-infrastructure (V2I) communication systems with multiple stationary roadside units (RSUs) is proposed. With the proposed strategy, the data delivery is accomplished through vehicles possessing identical packets received via broadcasting from an RSU, and the group of the packet-possessing vehicles is refreshed at each RSU hop. Numerical results show that the proposed strategy reduces the data delivery delay compared with an existing strategy and does so more significantly for a middle-range traffic density. In addition, the proposed strategy has better performance as the broadcast duration and the RSU's coverage area increase.

Hardware implementation of decimal arithmetic operations has become a hot topic for research during the last decade. Among various operations, decimal multiplication is considered as one of the most complicated dyadic operations, which requires high-cost hardware implementation. Therefore, the processor industry has opted to use the sequential decimal multipliers to reduce the high cost of parallel architectures. However, the main drawback of iterative multipliers is their high latency. In this reported work, the focus has been on reducing the latency of decimal sequential multipliers while maintaining a low cost of area. Consequently, a high-frequency sequential decimal multiplier is proposed whose cycle time is reduced to the latency of a binary half-adder plus that of a decimal multiply-by-two operation, which overall is less than that of a decimal carry-save adder. The synthesis results reveal that the proposed sequential multiplier works with a higher clock frequency than the fastest previous decimal multiplier which in turn leads to overall latency advantage.

High computational complexity associated with maximum-likelihood (ML) data decoding in orthogonal frequency division multiplexing (OFDM) systems that use selected mapping (SLM) for the reducing peak-to-average power ratio (PAPR) can be significantly reduced using modified SLM and data decoding techniques presented in this Letter. Simulations show that the proposed method achieves similar PAPR reduction capability and data recovery performance compared with standard SLM (with perfect data recovery) and an ML detection scheme.

A simpler MIMO transmission method using orthogonal directivities is proposed. In future wireless communication systems, higher data rates will be required since large amounts of data will be transmitted and received. MIMO technology is useful for achieving higher data rates. However, since MIMO detection becomes complicated when the number of antennas becomes large, a simpler method should be considered. To solve this problem, the present authors proposed a spatial division method using orthogonal directivities. This previously proposed method to N streams is expanded transmission for application to much higher data rate systems. Furthermore, using higher order antenna modes at the same frequency to more easily obtain orthogonal directivities is proposed. To evaluate the proposed method, it is confirmed by numerical analysis that the capacity of the proposed method increases without MIMO detection when the number of antennas becomes large.