A reflectarray composed of elements with electromagnetic bandgap (EBG) characteristics to improve radiation performances is proposed. The EBG elements are composed of patches and multiple via-holes to provide required reflection phase and bandgap characteristics at target frequency of 10 GHz. Compared with a normal patch reflectarray without EBG elements, the gain is improved by 1.4 dB, and the SLLs are suppressed by 1.5 dB (E-plane) and 5.3 dB (H-plane), respectively.

A broadband circularly polarised square slot antenna fed by a coplanar waveguide (CPW) from a corner of the slot is proposed. A check-shaped strip with its vertex connected to the protruded signal strip of the CPW is used to achieve circular polarisation. The measured 3 and 1 dB axial ratio bandwidths are 48 and 21.3%, respectively, and the input impedance bandwidth (|S ₁₁| ≤ − 10 dB) is 73.9%, which covers the entire circular polarisation band.

Proposed is an ultra-low-profile loop antenna backed by an electromagnetic bandgap (EBG) surface reflector, where the EBG surface can effectively exhibit the property of a perfect magnetic conductor (PMC) inside a deliberately designed bandwidth. It is shown that, assisted by the effective PMC bandwidth, while the proposed antenna is with a 0.07-λ spacing between the loops and the EBG reflector, its axial ratio (AR) and voltage standing wave ratio (VSWR) performances are significantly improved. Experimental measurements show that the prototype antenna has a 3 dB AR bandwidth of 17% with an input VSWR less than 1.6. The proposed approach can find a wide range of low-profile circularly polarised (CP) antenna applications.

A new technique to achieve high front-to-back radiation ratios of slot antennas is presented. A 0.8 mm thin metasurface is loaded onto a circularly-polarised slot antenna and backed by a metallic reflector at close distances. The antenna has an overall height of ∼ 0.1 wavelengths. However, it exhibits wideband characteristics with a measured impedance bandwidth (voltage standing-wave ratio ≤ 2) of 73.3% and a 3 dB axial-ratio bandwidth of 29.1%. A broadside gain of 7 dBic with a front-to-back ratio of 23.7 dB is achieved at 2.7 GHz.

Three-dimensional (3D) optical coherence tomography (3D-OCT) has attracted attention for visualising complex structures in the biomedical field. In this reported work, a high-speed 3D-OCT system is developed, which is based on a high-speed swept light source and a Mach-Zehnder interferometer with a high-speed photodetector. The light source, incorporating a KTa_1–x Nb _x O₃ electro-optic deflector, operates at a repetition rate of 200 kHz and enables high-speed data acquisition. As a preliminary study, images of a strawberry's surface have been obtained, two- and three-dimensionally. The 3D-OCT system has potential for the construction of a four-dimensional OCT image to dynamically display 3D-OCT images.

A power-efficient, process, voltage and temperature (PVT) robust g_ds cancellation method for gain enhancement is proposed. The method generates a negative conductance, which matches and cancels the positive conductance. This makes the g_ds cancellation method effective over process and wide temperature variation without the aid of external calibration or a tuning circuit. The method senses signals from cascode nodes instead of output nodes, making the method insensitive to output voltage swing. The simulation results of an example implementation in IBM 0.13 µm process show at least 22 dB DC gain enhancement over all process corners and temperatures ranging from − 20 to 80°C, with less than 9% power consumption overhead.

A floating-voltage DC source is proposed for simple AC–DC conversion. A conventional V _GS-multiplier circuit is modified with an additional control current signal in order to achieve variable output voltage. By modulating this control signal, the output voltage can track the input one so that the difference between the input and output voltages can be maintained to be constant with respect to varying the rectified input voltage. The proposed circuit is easily adopted for driving a light-emitting diode (LED) string, which provides a cost-effective solution for LED lighting applications.

The design of compensation filters for comb decimators using amplitude transformation is introduced. It is shown that the transformation of cosine-squared filters provides good compensation characteristics. For a first-degree polynomial, the slope of the transformation line is explicitly set as the unique compensator's multiplierless coefficient. This coefficient changes proportionally with the increase of the comb passband droop. Thus, the proposed approach provides an intuitive and easy way of designing compensation filters.

Image quality assessment (IQA) research strongly depends upon subjective experiments to provide ground truth to train and evaluate the IQA algorithms. These subjective experiments are cumbersome and expensive. An objective method based on human visual characteristics is proposed to generate the ground truth for distortion images. The proposed metric called Normalised Objective Distortion Score (NODS), using the logarithm of distortion parameter as the image quality score, is easily realised so that much manpower and time cost can be saved. The effectiveness of NODS has been analysed through experiments on five state-of-the-art IQA algorithms, and the result shows that the NODS is stable and can work as well as the subjective score when evaluating the performance of the IQA algorithms.

A new description method is proposed for sketched symbol recognition. It incorporates local direction information into the Zernike moments which represent only the spatial distribution of sample points. A symbol is decomposed into several component patterns according to the local direction of sample points before Zernike moments computation. The resulting descriptor inherits from the traditional Zernike moments descriptor the invariability to stroke number, stroke order and symbol rotation. Moreover, the fusion of both types of data makes it more informative and discriminative, resulting in better performances in both rotation-invariant classification and rotation angle estimation.

A novel decoding method is proposed to improve the decoding quality of both compressed sensing (CS) frames and key frames in distributed compressive video sensing at low CS frames sampling rate. Results manifest that the decoding performance of the proposed approach at low sampling rate outperforms the state-of-the-art block-based compressed sensing-based codecs.

A new algorithm for lossless compression of hyperspectral imagery is proposed. First, the average value of four neighbour pixels of the current pixel is calculated as local mean, which is subtracted by the current pixel to eliminate correlation in the current band image. The residual produced by this step is called local difference. The local differences of the pixels which co-locate with the current pixel in previous bands form the input vector of the recursive least square (RLS) filter, by which the prediction value of the current local difference is produced. Then, the prediction residual is sent to the adaptive arithmetic encoder. Experiment results show that the proposed algorithm produces state-of-the-art performance with relatively low complexity, and it is suitable for real-time compression on satellites.

Early termination techniques are widely used in low-density party-check (LDPC) decoding since the decoding operations can be tremendously reduced. A layer stopping criterion is proposed to reduce further the operations within iterative layered LDPC decoding. The proposed criterion detects the high reliability of the soft log-likelihood ratio with a threshold in each layer. Then the layer operations can be stopped when the reliable layers are detected. The proposed criterion combined with early termination techniques can efficiently reduce the layer operations by up to 60% with a negligible loss of coding gain at E_b /N ₀ of 3.2 dB.

A novel switching scheme using multiple shared memories is proposed. It has low implementation complexity and ideal performance for both uniform traffic and non-uniform traffic without speedup. The proposed algorithm assigns an output time for each incoming data according to its destination and distributes them into 2N shared memories that can be addressable by output time, where N is the number of input/output ports. Experimental results show that the proposed scheme has good performance for both uniform traffic and non-uniform traffic.

Symmetries in the encoding of balanced sequences are exploited to simplify a tabular approach for constructing balanced codes, and it is shown that with appropriate assignment of source word probabilities, these symmetries ensure the absence of discrete components in the spectrum of the encoded signal. He is further shown that assigning appropriate priorities to codewords during table construction results in superior low-frequency performance, and the use of these techniques is demonstrated in the construction of a balanced QPSK code.

A passive position orientation measurement method is presented which leverages the spatial variation of the reflected magnetoquasistatic field from a mobile loop to determine the loop's spatial orientation. The azimuthal orientation was measured from 0° to 360° at a distance of 1 m from the fixed measurement loop. Inverting the theoretical expressions to estimate orientation from measured field values resulted in an average and RMS error of 3.15° and 4.55°, respectively. This technique offers a means to accurately determine the orientation of the mobile loop through purely passive methods.

A dual-band bandpass filter with quasi-elliptic response using a substrate integrated waveguide for 60 GHz dual-band wireless communication systems is proposed. It is fabricated with standard low-temperature co-fired ceramic (LTCC) technology. The measured results indicate that the filter is operating at 59.78 and 61.56 GHz with fractional bandwidths of 2.1 and 2.2%, and minimum in-band insertion losses of 3.61 and 3.55 dB, respectively. Furthermore, the proposed filter exhibits an electrical size (including the CPW measurement pads) of 2.38λ _g × 3.14λ _g, where λ _g is the guided wavelength at 60 GHz.

A compact upper wideband unequal power divider with planar configuration is proposed. This power divider includes two-section asymmetric coupled transmission lines and non-uniform microstrip. The measured results of the prototype divider show that the 12.1 dB return loss and ports-isolation band is in the range from 3.1 to 10.6 GHz, the unequal power division coefficient is almost in the range 4.03–5 dB (the simulated result: 4.3–4.75 dB).

A new switchable bandpass filter using switchable connected-coupling lines (SCCLs) is presented. The SCCL is embedded in a bandpass filter and treated as an admittance inverter to provide adequate coupling coefficient to form a bandpass response in an on state. The passband of the bandpass filter is centerd at 1.5 GHz with 12.8% 3-dB fractional bandwidth. In the off state, the switchable line acts as a travelling-wave switch to cut off the coupling path to achieve a high isolation. The measured isolation of the circuit is greater than 48 dB over the operating bandwidth.

A novel short waveguide terminal load (patent pending) with broad bandwidth is proposed and demonstrated. A simple design procedure is developed for the proposed terminal load. For verification purposes, a terminal load over the frequency range from 6.57 to 9.99 GHz was designed, manufactured and measured. The simulated results are compared with the measured data, and good agreement is reported. The measured return loss is greater than 20 dB over the full waveguide operating band (R84 standard waveguide), its total length is less than 35 mm, which is about a half of a commercial load with the same performance.

A compact tunable bandpass filter (BPF) with wide tuning range and enhanced stopband characteristics based on low-temperature co-fired ceramic technique is proposed. The wide tuning range is realised by properly introducing an axial coupling structure. Three transmission zeros are obtained near the passband for enhanced frequency selectivity by introducing mixed electric/magnetic (E/M) coupling between the source/load and the taped inductor. Back-to-back varactor diodes are adopted to improve linearity characteristics. A tunable BPF with a 120% tuning range from 370 to 850 MHz has been designed and fabricated to verify the proposed design concept. The measured results are in good agreement with the electromagnetic simulation. The circuit occupies only 4.0 × 3.0 × 1.6 mm³.

A compact circular resonator for a microwave plasma lamp is designed. A disc-shaped metal sheet is loaded in the coaxial resonant cavity to reduce the volume by increasing its equivalent capacitance. The operating centre frequency of the proposed circular resonator is 444.5 MHz with a radius of 25 mm and height of 40 mm. The proposed compact resonator does not need to be filled with dielectric material, therefore it is very easy to manufacture with low cost. The test results show that the proposed resonator exhibits good performance.

A simple wideband bandstop filter which yields equal ripples in the stopband is described. The filter comprises only two resonators and a connecting transmission line. Ultra-wide stopband characteristic is achieved by realising three transmission zeros near the passband edges. Stopband rejection depth and bandwidth can be controlled by impedances of the configuration. The defected ground structure is chosen to realise the high impedance line. To validate the proposed topology, a compact microstrip bandstop filter centred at 1.5 GHz with a measured 20 dB rejection bandwidth of about 139% is fabricated.

Multimode bandpass filters are proposed by using a hairpin resonator and two multimode resonators. The proposed bandpass filter has five-mode resonance in a passband and transmission zeros at both the lower and higher stopbands near the cutoff frequencies. Because the steep characteristics at the edge of the passband and the high attenuation level at the stopbands can be obtained due to the multimode resonance and transmission zeros, a frequency diplexer with adjacent passbands can be comprised of the proposed bandpass filters by using an open-matching methodology.

A surface passivation technique of high electron mobility transistor (HEMT) devices is reported. The passivated HEMT device has a much higher RF performance of F_T and F _max than a non-passivated one. The AlGaN/GaN HEMT has a short gate length of 0.15 µm using an E-beam lithography system and very low ohmic contact resistance of 1.3 × 10⁻⁶ Ωcm⁻² using a rapid thermal processing alloy system. In addition, to protect the active layer from the surface trap, an SiO₂ thin film passivation process is applied by the plasma-enhanced chemical vapour deposition system. The fabricated AlGaN/GaN HEMT exhibits a maximum drain current of 900 mA/mm and a maximum transconductance of 320 mS/mm. In particular, this device produces excellent RF performance of small-signal characteristics, such as a current gain cut-off frequency (f_T ) of 55 GHz and maximum oscillation frequencies (f _max) of 130 GHz.

The technique of dual transmission lines is applied to replace quarter wave transformers for a compact Bagley polygon power divider. The developed Bagley polygon power divider not only can be easily fabricated on the planar printed circuit board without a lumped element, but also has the characteristics of compact size and wide bandwidth. For verification, a proposed three-way microstrip power divider is designed and fabricated at 2.0 GHz. Simulated and measured frequency responses both validate the proposed power divider with dual transmission lines. Furthermore, the developed power divider only occupies a 23% circuit size of the conventional one.

A circuit for single-photon avalanche diode (SPAD) current read-out, for photon timing applications, is proposed. The circuit consists of a single-transistor transimpedance amplifier with a gigahertz bandwidth: the feedback loop fixes the SPAD anode voltage and allows obtaining a high time resolution with a very high equivalent current threshold (almost 700 µA). The transimpedance stage is followed by a lowpass filter that reduces the crosstalk of other on-chip detectors and makes the designed structure suitable for multi-detector systems. The presented discrete components prototype achieves a state-of-the-art resolution of 34.4 ps full width at half maximum, has negligible crosstalk between the different pixels and opens the way for the development of an integrated structure with a large number of channels.

Hybrid infrared (IR) focal plane arrays consist of an array of IR photo-detectors, bump-bonded to a silicon CMOS readout integrated circuit (ROIC) chip. Design and optimisation of ROIC for quantum dot IR detectors is a multidimensional problem. The major design challenge is to select appropriate readout circuit topology to meet the large dynamic range requirement of quantum dot IR photo-detectors within the area dictated by the matched pixel size. Proposed is an efficient design optimisation for ROIC. The optimisation is based on a proposed decision matrix, which leads to a decision merit for ROIC design. Four main specifications, i.e. charge handling capacity, noise, power dissipation and detector bias voltage variations, have been considered. Various architectures have been compared using circuit design, simulation and implementation. The targeted ROIC specifications for a test chip containing a 4 × 4 array are: 5 Mē charge handling capacity, 30 × 30 µm maximum pixel size, snapshot mode of operation, variable integration time, 5 megapixels/s (Mpps) readout rate and readout noise of 600ē at ambient temperature. Also presented is a design with 5 Mē charge handling capacity, which has not been reported for 180 nm CMOS process earlier.

A flat super-continuum (SC) generated by a 1.5 µm passively fibre modelocked laser incorporating a single-walled carbon-nanotube-based saturable absorber and a normal dispersion highly nonlinear photonic crystal fibre (PCF) is demonstrated. A compressed 620 fs pulse train from the modelocked laser is obtained and launched into the PCF. Since the pulses propagate in the normal dispersion regime of the PCF, linear frequency chirp is induced by self-phase modulation which leads to a flat SC. An SC covering 200 nm with less than 7 dB power fluctuation is achieved. The experimental results are consistent with the theoretical analysis based on the nonlinear Schrödinger equation.

Error-free transmission is demonstrated at bit rates up to 57 Gbit/s back-to-back, up to 55 Gbit/s over 50 m fibre and up to 43 Gbit/s over 100 m fibre using an oxide-confined 850 nm high-speed vertical cavity surface-emitting laser with a photon lifetime optimised for high-speed data transmission.

A single-stage battery charger for light electric vehicles to improve lifetime by removing high-voltage electrolytic capacitors is suggested. The proposed charger is based on a diode-clamped series resonant converter equipped with a current-boosting circuit, which increases the power factor by removing dead zones in the line current. The feasibility of the proposed charger has been verified with a 1.7 kW prototype.

Onshore high-frequency surface wave radar (HFSWR) has been successfully deployed for early warning and ocean remote sensing. However, there remain potential gaps in ocean remote sensing for shipborne HFSWR. Based on the first-order bistatic field equation, the first-order ocean surface cross-section for shipborne HFSWR is derived, whose validity is verified by experimental results. Consequently, studies on ocean surface information extraction with shipborne HFSWR could be conducted. The simulation results demonstrate that shipborne HFSWR has the potential of sea surface wind direction extraction with a single receiving sensor rather than a receiving array, and in addition wind direction ambiguity existing in onshore HFSWR disappears.

The successful fabrication of InAlSb/InAs and InAlSb/InAsSb HFETs using recessed gate technology is reported. Epitaxial growth, device fabrication and characterisation are discussed in this Letter. A comparison of the two kinds of HFETs shows that the use of Sb in the InAs channel layer can effectively reduce the gate leakage resulting from the band-to-band tunnelling. This improvement is primarily because of increased separation between the conduction band edge of the InAsSb channel layer and the valence band edge of the InAlSb top barrier layer. An InAlSb/InAsSb HFET with 2 μm gate length and 50 μm gate width shows I _D = 596 mA/mm and g_m = 1 S/mm.

Three-dimensional (3D) integration of coaxial through silicon vias (TSVs) is becoming an area of considerable interest owing to their superior high-frequency performance in comparison to standard 3D interconnects. However, in contrast to standard TSVs, coaxial TSVs require more processing to integrate the ground shield surrounding the copper via. Cost-effective methods for implementing coaxial TSV technology with CMOS processing are challenging. Demonstrated is a low-cost fabrication method for integrating coaxial TSVs within the confines of a standard CMOS process is demonstrated.

The influence of carrier concentration and oxygen vacancy on the performance of amorphous-indium–tin–zinc-oxide (a-ITZO) thin-film transistors (TFTs) is reported. The ITZO TFT with lowest carrier concentration and oxygen vacancy has a high field-effect mobility (μ _FE) of 37.2 cm²/V•s, a high on/off current ratio (I _ON/I _OFF) of ∼1 × 10⁷ and a low subthreshold swing (SS) of 0.93 V/decade. By increasing the carrier concentration and oxygen vacancy, μ _FE, I _ON/OFF and SS were surprisingly degraded to 14.4 cm²/V•s, ∼4 × 10⁴ and 4.01 V/decade, respectively. By controlling the carrier concentration and oxygen vacancies of ITZO bulk, improvement of the performance in TFT devices can be achieved. The proposed high μ _FE of 37.2 cm²/V•s is enough for the application of next-generation displays requiring ultra-high resolution and high-frame-rate displays.

A detailed study of a tunnelling field-effect transistor using a SOI substrate with raised buried oxide in the drain is reported. The simulated device exhibits improved ON current, lower OFF current, high transconductance and better subthreshold swing with variations to gate length scaling. Moreover, it is immune to short channel effects such as drain-induced barrier narrowing, threshold voltage roll-off etc. The hetero-gate dielectric is used to reduce the parasitic bipolar current at the drain side and to increase the tunnelling generation rate at the source side. The study was carried out using the two-dimensional Synopsys TCAD tool.

As an implementation of the static random access memory (SRAM), the tunnelling SRAM (TSRAM) uses the negative differential resistance of resonant (interband) tunnelling diodes (R(I)TDs) and potentially offers improved standby power dissipation and integration density compared with the conventional CMOS SRAM. TSRAM has not yet been realised with a useful bit capacity mainly because the level of reproducibility required of the nanoscale R(I)TDs has been demanding and difficult to achieve. In this reported work, the design of TSRAM cells is approached from the perspective of maximising their yield and specific results are presented for an RITD-based cell. With advances in the control of semiconductor multilayer growth, it is shown that achieving acceptable yields is now within sight.

The independent vector analysis algorithm can theoretically avoid the permutation problem in frequency domain blind source separation by using a multivariate source prior to retain the dependency between different frequency bins of each source. A super-Gaussian multivariate Student's t-distribution is adopted as the source prior to model the spectrum of speech signals and to mitigate imprecise variance knowledge as is commonplace in non-stationary signal processing. Moreover, the new multivariate source prior can be interpreted as a joint distribution constructed by a t-copula, which can describe the nonlinear inter-frequency dependency. Experimental results using 50 speech mixtures formed from the TIMIT database confirm the advantages of the proposed algorithm.

In the case of a low-field nuclear magnetic resonance (NMR) system, the sensible magnetic sensor can be screened or even damaged by the large magnetic field produced during the polarisation phase. A switch is then necessary to preserve this sophisticated sensor. A simple and efficient switch is described here. It is made of a twisted and wound wire heated by a laser beam, in which the alignment is simple by construction. The switch can be used without any additional contact in sensing coils, has a low inductance and flips within milliseconds. It is shown that the switch resistance in open conditions is sufficient for low-field NMR applications and that a memory behaviour can be exhibited.

An area-efficient CMOS impulse radio ultra-wideband (IR-UWB) transmitter capable of generating variable orders of Gaussian pulses is presented. The core of the pulse generator is constructed using the cascade connection of RC differentiator networks separated by tunable amplifiers. Tuning the bias current of the amplifier using a voltage-controlled current-source allows for generation of varying orders of Gaussian pulses, which in turn allows for controlling the power and spectral mask of transmitted signals. Fabricated in a TSMC 90 nm digital CMOS process, the measurement shows that the fully integrated transmitter can generate fifth- to sixth-order Gaussian pulses. The core transmitter consumes 10.0–12.0 mW at 200 MHz pulse repeating frequency and occupies a chip area of 0.008 mm² only.

A mechanism for deploying a minimum number of sensors to cover all targets that are randomly placed in a grid environment is discussed. The sensors are deployed at grid points that do not have targets. In the presented method, condideration is given to a grid point, called the sink, to start deploying the sensors. From the sink location, movement is in one of four possible directions (up, down, left, right) to find the next grid point for placing the sensor depending on the maximum number of targets covered by the new sensor. In case there is no path to move due to target placement, a random grid point is chosen as the next location. This is done till all targets are covered. This process is carried out for each possible sink location and the sink location corresponding to the minimum number of sensors is noted.