A passive radio frequency identification (RFID) tag antenna providing a long recognition distance is proposed, which is mountable on various types of platforms including metallic and highly dielectric objects. To increase the reading distance, the antenna is installed in a recessed metallic cavity. To reduce further the height of the antenna, an artificial magnetic conductor is placed on the bottom face of the cavity. Consequently, the tag antenna not only can be miniaturised, but also can provide long reading distances on any type of platform objects. The measured maximum reading distance and the minimum sensitivity are 12.2 m and −17 dBm, under a reader transmitting 30 dBm with a 6 dBi antenna. Good agreement between the prediction and experimental results verifies that the approach is fairly effective and useful to substantially increase the reading distance.

A compact helical antenna with a small ground is proposed for 5.2/5.8 GHz WLAN applications. The proposed antenna can be easily mounted in the space-limited systems. Good impedance matching is achieved by a spiral-shaped microstrip line feed structure. Relatively uniform current along the helix is observed owing to the travelling-wave current on the feed structure, which contributes to high-gain performance even with a small ground. The measured 3 dB axial ratio bandwidth and impedance bandwidth for S ₁₁ ≤ −10 dB overlap over 5–6 GHz, whereas the realised gain of about 13–14 dBic is achieved over the 5.2/5.8 GHz WLAN band.

An isolation enhancement technique for a wideband (1.71–2.17 GHz) and ±45° linear dual-polarised suspended plate antenna is proposed. Isolation (S ₁₂, S ₂₁) between channels is improved by making extensions on suspended plates (SPs) 1–2 and inserting a vertical ungrounded vertical wall under SP-1. The modified T-type probes in this design provide better coupling and return losses (S ₁₁, S ₂₂) for wideband operation. Based on the numerical simulations and measurements, it is observed that 8.2 ± 0.5 dBi gain and 66° ± 6° symmetric azimuth and elevation radiation patterns are obtained. Return losses ≤ − 15 dB and isolation ≤ − 30 dB are achieved in the entire band. This antenna is suitable for base stations of mobile wireless communication systems (PCS, DCS and IMTS ).

A passive chipless radio-frequency identification (RFID) tag based on a log-periodic (LP) dipole array is proposed, where the tailorable band-rejection property of the LP aperture is utilised to realise a large number of codes. The proposed tag principle is successfully validated by measurements, where the absence and presence of the band-rejection is shown to carry the bit information. Its fabrication simplicity is also demonstrated by its implementation on a flexible substrate. Finally, two different tag formation schemes, based on a specific set of resonance suppressions, are discussed in detail.

A compact Ka-band (26.5–40 GHz) dielectric rod end-fired antenna array for the three-dimensional (3D) active holographic imaging system is presented. Without horn shape feeding, the new antenna array is specially designed with characteristics such as small size, high gain, good radiation pattern, easy realisation, low insertion loss and low mutual coupling. In the imaging system, the spacing of sending and receiving antenna units is 1.5 wavelengths with mutual coupling <−30 dB and a gain of 12–16 dB. The results and analysis provide guidelines for the design of millimetre-wave end-fired antenna arrays.

A new approach called the window increasing technique (WIT) is presented to discriminate mathematical and physical poles extracted from a noisy antenna response. The principle of the WIT is to apply a pole extraction method on several windows of the response and then to observe the stability of the extracted poles. To compare the WIT with the classical window moving technique (WMT), these two techniques are applied on the electric far-field backscattered by a dipole antenna. It is shown that, in the presence of noise, the WIT allows finding more physical poles with a good accuracy than does the WMT.

A bilateral Vivaldi antenna with reduced radar cross-section (RCS) is presented. A half-mode substrate integrated waveguide structure is first utilised in the low RCS Vivaldi antenna design. Compared with traditional antenna, the monostatic RCS of the proposed antenna can be reduced to as much as 24 dB without degradation of antenna performance.

An ultra-thin optical probe based on spatially resolved near infrared spectroscopy (NIRS) is developed and the measurement sensitivity of cerebral tissue using minimally invasive implantation of the optical probe is examined. The optical sensor head consists of bare chips of light-emitting diodes and photodiodes, which were mounted on a polyimide-based flexible substrate. The minimum and maximum thicknesses of the sensor head were 80 and 300 μm, respectively. The light propagation of the NIRS measurement with implanted optical sensor was analysed using the Monte Carlo simulation based on transport theory. The optical path lengths for brain and scalp were 2.3 times and 1/20th, respectively, as compared with generally available NIRS probes, which were attached on the body surface. The influences of the optical block on measurement sensitivity were revealed, and the volume of the sensor head was minimised. Findings also show that the sensitivity distribution is adjustable by changing the medium between sources and detectors.

Autofocusing is a key building block in the modern automated high-throughput systems for a quantitative analysis of microscopy images. For that reason, it has received great attention, and diverse autofocus algorithms have been proposed in the literature. A fast autofocus algorithm is presented in order to build a real-time system for diagnosing the sputum smear samples. The method involves transforming the sputum smear fluorescence images from a multibit to a 1 bit/pixel representation. This results in a substantial reduction in the computational cost, while maintaining a good focusing performance. Experimental results are presented to validate the feasibility and the effectiveness of the proposed method.

A new sensor interface topology is presented that is particularly attractive for integration into modern low-voltage low-power CMOS microelectronics. The new circuit is inherently linear and provides better gain, sensitivity and dynamic range than the widely used Wheatstone bridge. The proposed structure not only offers all the benefits of the current-driven Anderson loop, but also outperforms the latter in terms of output range, sensitivity and design simplicity. In addition, the new architecture is scalable to the interface with multiple sensor elements with very little or no extra circuit overhead.

A delay-based noise cancelling sturdy multi-stage noise shaping (MASH) structure that cancels the first-stage quantisation error is presented. Thus, a smaller number of bits can be used for the first-stage quantiser without degrading the overall performance. In addition, the proposed structure improves stability with respect to maximum applicable input by removing the first-stage quantisation error from the first loop.

A high boost ratio non-isolated converter with a ripple-free input current is proposed, which combines a zero-ripple boost cell and a coupled inductor to achieve a high output voltage step-up. A passive snubber is utilised to suppress voltage spike of the switch caused by the resonance of the leakage inductance of the coupled inductor and the parasitic capacitance of the switch. Therefore, a low-voltage-rated metal oxide semiconductor field effect transistor (MOSFET) with low r _DS(ON) can be used to improve the efficiency of the converter. In addition, a ripple-free input current can be achieved, making the electromagnetic interference (EMI) filter simple. Experimental results of a 100 W (40 V/200 V) prototype are presented to verify the analysis results of the proposed converter.

A new method that compensates for the low DC gain of nanometre operational amplifiers (opamps) used for high-speed continuous-time (CT) ΣΔ modulators is described. The proposed solution compensates for the integrator's phase error which is a main limitation produced by the low opamp's gain. The method uses a simple auxiliary gain stage and a resistor. Simulations of a second-order CT ΣΔ modulator utilising fast single-stage opamps with gain as low as 25 dB verify the effectiveness of the method.

A polymer dielectric film with chlorine (Cl)-containing polymer additives was fabricated to investigate the effect of additives on dielectric performance. Polychlorostyrene or polyvinyl chloride (PVC) was used as a polymer additive in the polymer film. At 0.1 V and 10 Hz, the polymer dielectric film with PVC had a dielectric constant of 23.6 with a dielectric loss of 0.04. This film exhibited a 73% increase in dielectric constant compared with the film without additives. The increment in the dielectric constant was attributed to the high polarisability of Cl atoms.

In open-ended coaxial dielectric characterisation techniques, intermediate liquid standards between air and water are necessary for precise dielectric measurements of biological samples. Calibration standards with dielectric permittivities much different from those of the measured samples will produce unreliable results. Different intermediate calibration standards are prepared and measurement results are presented. The aim is to obtain various permittivity values between 10 and 80 by diluting methanol and ethanol with distilled water. This technique can also be used for assessing the purity of alcohols.

Neurons in the primary visual cortex (V1) respond differently to a simple visual element presented in isolation from when it is embedded within a cluttered scene. The contextual influences are mediated by horizontal connections within V1. Inspired by these visual cortical mechanisms, a contour detection model is proposed. Different from previous researches, the facilitation and the suppression are unified modulated by surrounding elements in the image without separating regions of excitatory and inhibitory lateral connections specifically. The proposed model can selectively extract object contours while reducing non-meaningful texture edges and process angular visual features such as corners and T-junctions effectively. The experiments demonstrate the effectiveness of the proposed model.

A correlation study of a set of video object trackers evaluation metrics is presented. There are multiple metrics in the state-of-the-art, and the main differences between them are based on the penalties that are attributed to the errors (false positives, false negatives, target loss etc.). After defining each one of the considered metrics, a correlation study is presented showing the redundancy between all the metrics. This reported study was performed using multiple tracking algorithms, and an extensive set of video sequences that attempt to cover many different situations.

The increasing number of cameras and a handful of human operators to monitor the video inputs from hundreds of cameras leave the system ill equipped to fulfil the task of detecting anomalies. Thus, there is a dire need to automatically detect the regions that require immediate attention for more effective and proactive surveillance. A framework that utilises the temporal variations in the flow field of a crowd scene to automatically detect salient regions is proposed, while eliminating the need to have prior knowledge of the scene or training. The flow fields are deemed to be a dynamic system and adopt the stability theory of dynamic systems, to determine the motion dynamics within a given area. In this context, the salient regions refer to the areas with high motion dynamics, where the points in a particular region are unstable. The experimental results on public, crowd scenes have shown the effectiveness of the proposed method in detecting salient regions which correspond to an unstable flow, occlusions, bottlenecks, and entries and exits.

Based on the set positioning in hierarchical tree (SPIHT) algorithm, fast seismic data compression based on the high-efficiency SPIHT (HESPIHT) algorithm is presented. To verify the validity of the algorithm, 10 seismic cross-sections are selected for the experiment. The result shows that the algorithm can reserve the quality of data better, meanwhile improving the efficiency of encoding and decoding.

High-efficiency video coding (HEVC) is the next generation standard of video coding. The deblocking filter (DF) constitutes a significant part of the HEVC decoder complexity. A three-step parallel framework (TPF) is proposed for the H.264/AVC DF, which is also suitable for HEVC except the third step. The third step of the TPF is replaced with a directed acyclic graph-based order. Experiments show that the proposed method dramatically accelerates more than the state-of-the-art parallel method.

A combined method involving global and local descriptors was developed to recognise scenes for loop closure detection in low-textured environments. An omnidirectional image is divided into background regions and salient regions according to the colour distribution. To represent a scene with features that are appropriate to its characteristics, global features for background regions are calculated and scale invariant feature transform features for salient regions are extracted. The proposed method can compute a more distinct scene similarity, and this was verified by an experiment involving loop closure detection.

A side information (SI) generation method is presented for the distributed video codecs with a scalable frame rate. SI interpolation, based on a hierarchical motion estimation with an adaptive block expansion, is proposed to reduce the power of the virtual channel noise, especially in sequences with lower frame rates. Blocks are classified into subframes in descending order of the estimated sum of the absolute difference (SAD), and each subframe is encoded if the maximum SAD of its blocks is larger than the estimated distortion of the key frames. Through a simulation, the proposed scheme is shown to achieve a coding efficiency close to that of H.264 with a zero motion even for very low frame rates.

The group delay fluctuation of navigation equipment will cause signal distortion, thus bringing on ranging bias, and therfore needs to be measured and compensated. The vector network analyser method commonly adopted cannot satisfy high measuring accuracy and high frequency resolution at the same time; the higher the frequency resolution, the bigger the measuring error. To resolve this problem, a new group delay measurement method based on narrow-band spread spectrum signals is proposed. Theoretical analysis and simulation results indicate that this method can implement high measuring accuracy with any frequency resolution, and the system bias of the method is much less than 0.1 ns.

The diffusion least mean p-power (LMP) algorithm is extended with adaptive variable power p in the generalised Gaussian distribution (GGD) environments. The GGD is one of the widely used distributions in the signal processing area. For the proposed method, priori knowledge of the distribution parameters is not required. Furthermore, it is robust to the preselected initial power order. Numerical results are provided to verify the performance of the proposed method.

A novel microelectromechanical system capacitive pressure sensor with two wings, which amplify the mechanical deformation of the pressure sensing diaphragm and increase the sensor's sensitivity, is presented. This seesaw structure is available for both single and differential capacitive pressure sensors. To verify this design, a single capacitive pressure sensor is manufactured based on silicon on a insulator (SOI) wafer. The test result shows that this pressure sensor has a sensitivity of 7.75 fF/kPa.

A high-power terahertz solid-state amplifier fabricated using 0.25 μm InP heterojunction bipolar transistor (HBT) technology is reported. This amplifier utilies a novel defective-ground four-way balun to combine differential amplifier chains for a total output device periphery of 40 μm. A significant amount of power of ∼10 mW is obtained at 305 GHz with better than 20 dB small-signal gain.

A new kind of differential microstrip lines by introducing periodic subwavelength corrugation in the edge, which is able to support low-frequency spoof surface plasmon polaritions, is proposed. The surface current distribution of the subwavelength periodic corrugated microstrip is numerically analysed. A kind of differential to single-ended microstrip coupling circuit is designed to investigate the ability of suppressing the crosstalk of such a subwavelength periodic corrugated differential pair. Experimental results show that such a structure can be utilised to effectively suppress crosstalk, and to reduce the transformation between differential-mode and common-mode signals.

To simultaneously achieve a high optical-transparency and Wi-Fi bandpass filtering characteristics for optical windows, a novel mesh-coated frequency selective surface (FSS) is designed and fabricated using an ultraviolet lithography technique. Simulation and experimental results show that the resonant centre frequency of the proposed mesh-coated FSS is about 5.3 GHz with a transmittance loss of −2 dB, while its optical transmittance is above 87.5% in the infrared (IR) waveband ranging from 1.35 to 3.3 μm. Moreover, such a FSS has the merits of ameliorable electromagnetic shielding effectiveness and improvable optical transmittance by optimising the thickness of the mesh layer. Both the design procedure and experimental measuring results are presented and discussed.

A compact in-phase power divider utilising a stepped-impedance three-line coupled structure and microstrip-to-slotline transitions is presented. The equivalent circuit of the structure is used to predict the required dimensions for ultra-wideband performance. The length of the structure, excluding the input/output ports needed for the measurements, is around a quarter guided wavelength. The simulated and measured results for the two developed devices indicate equal in-phase power division with less than 0.1 dB and 2° amplitude and phase imbalances, respectively. The return loss at the three ports is more than 15 dB in one prototype, whereas the isolation is more than 13 dB in the other across the band from 3.1 to 10.6 GHz.

A high-selectivity wideband bandpass filter consisting of a ring resonator and stepped impedance resonators is proposed. A wideband bandpass filter with multiple transmission poles and transmission zeros is obtained. For demonstration, a prototype operating at the frequency band of 4.14–9.56 GHz (with a fractional bandwidth of 79.1%) is designed and fabricated. Good agreements between the simulated and the measured results have been observed, indicating a very sharp out-of-band rejection.

A coherent terahertz (THz) link at 200 GHz , with a variable data rate up to 11 Gbit/s, featuring a very high sensitivity at the receiver, is investigated. The system uses a quasi-optic unitravelling carrier photodiode (UTC-PD) emitter and an electronic receiver. The coherent link relies on an optical frequency comb generator at the emission to produce an optical beat note with 200 GHz separation, phase-locked with the receiver. Bit error ratio testing has been carried out using an indoor link configuration, and error-free operation is obtained up to 10 Gbit/s with a received power <2 µW.

A wavelength filter using Si wire waveguide Bragg grating and multimode interference couplers is reported. The device is designed for the optical network unit of the fibre to the home system. All the components are designed to achieve polarisation independence.

A reflection imaging system based on the terahertz quantum-well photodetector is presented. Reflected terahertz imaging of a logo on a universal serial bus (USB) flash disk is demonstrated. A spatial resolution better than 0.4 mm is achieved. This experiment demonstrates that the quantum-well photodetector is potentially useful for reflection imaging applications.

A multi-branch current sensing technique for three-phase current reconstruction with a non-contact-type current sensor is introduced. In the proposed method, the non-contact-type current sensor measures two branches’ current simultaneously in a three-phase inverter, and all phases’ current information is obtained in a single switching cycle. The proposed method completely takes the advantages of the previous multi-branch current sensing technique, and even further accuracy improvement is achieved. The proposed method is verified through experiments.

A secondary coil design is reported for the stable transmission of wireless power in a misalignment situation. A coil array is applied to a secondary coil instead of typical single coil. When a misalignment occurs, the misalignment distance between an individual coil in the array and the primary coil is decreased relatively. Therefore, the sudden reduction in the inductive wireless power transmission (WPT) efficiency is mitigated. When the fabricated coil array transmits power, the maximum WPT efficiency improves by 56.45% compared with the typical single coil. The frequency band of the proposed array is wider, and this system can stably transmit power.

Recently, nonlocal filtering methods for synthetic aperture radar (SAR) despeckling have attracted a lot of attention. In general, a suitable similarity measure well suited to SAR images is derived by incorporating the noise statistics. One important nonlocal framework is the probabilistic patch-based (PPB) filter, which derives the similarity measure in a data-driven way and provides promising results. A drawback of this filter is the suppression of thin and dark details since the PPB method takes into account the photometrically similar patches, yet it ignores the geometric structure of image patches. To overcome these disadvantages, a new patch-based despeckling method is presented which exploits both geometrical and photometrical similarities. Numerical experiments suggest that the proposed method is on a par with or exceeds the state-of-the-art PPB method, both visually and quantitatively.

A sub-bandgap circuit architecture employed to achieve a precision reference in 28 nm CMOS technology is described. The 500 mV voltage reference exhibits < 10 ppm/°C drift from −40 to 125°C and 5.5 μV of root-mean-square (RMS) noise in a 0.1–10 Hz bandwidth, dissipates 500 μW of power on a 1.2 V supply and occupies 0.09 mm².

A way to improve the metal–oxide–semiconductor field effect transistor (MOSFET) analogue electrical performance, still little explored, is to modify their aspect form or ratio (AR) by the use of innovative layout styles. The diamond MOSFET (DM) is an example of this approach. It presents hexagonal gate geometry. This new layout structure for MOSFET induces two additional effects in comparison with the conventional (i.e. rectangular gate geometry) MOSFET (CM) counterpart, which improves the device's electrical performance: the longitudinal corner effect (LCE) and parallel association of MOSFET with different channel length effect (PAMDLE). How the diamond layout style (DLS) can significantly enhance the device's frequency response (FR) by using two different integrated circuits’ (IC) complementary metal–oxide–semiconductor (CMOS) manufacturing process technologies (bulk and silicon-on-insulator (SOI)) is demonstrated.

A low-power wideband common-gate (CG) low-noise amplifier (LNA) presented . The CG LNA uses double g _m enhancement to provide input matching under low-power consumption. Feed-forward noise cancellation (FFNC) is employed in the LNA to suppress the noise from the CG transistor. The LNA is designed and fabricated in TSMC 130-nm CMOS technology. This LNA can achieve a maximum gain of 14 dB with a 3 dB bandwidth from 350 to 950 MHz. The LNA consumes 0.5 mA current under a 0.8-V supply. The average noise figure of the LNA is 4.0 dB. The core area of the LNA is 0.06 mm².

Considering more practical scenarios in the designing of joint routing, channel-assignment and scheduling algorithms in multichannel wireless networks, a modified routing selection scheme based on a performance guaranteed MP mechanism is put forward. The assumption made in MP, that the balance factor chosen for each link α_l = α for all links l is not reasonable, is pointed out and may influence the performance of MP badly in the case of channels with large diversity. Focusing on this point, a balance factor used for channel assignment in MP is taken into account in the stage of route selection and the limitation of original MP is relaxed. As a result, the proposed joint algorithm is able to better adapt to the condition of channels with large diversity. It is proved that the modified policy for MP is able to achieve the same capacity region as that of original MP.

A technique to improve the accuracy of an electrical energy consumption monitoring system is proposed. This system is based on a network of Hall effect wireless sensors attached to the wire at the output of every circuit breaker in the electrical distribution panel. The readings provided by the Hall effect sensors show significant gain errors due to their sensitivity to the distance between the sensor and the monitored wire. To mitigate these gain errors and increase the system accuracy, the addition of a single high-precision current transformer sensor at the main electrical input is proposed, measuring the total current. This signal is used as the reference signal in a least-mean square algorithm to compensate for the unknown gains of the Hall effect sensors. Experimental results using three prototype Hall effect sensors show that the proposed solution converges within 1.7 min, reducing the average current measurement error from 2.54 to 0.46 A_rms.

The exact bit error rate (BER) analysis of a space-time coded radio frequency identification (RFID) system is presented, where the tag has multiple antennas and the reader has a single antenna. In the analysis, the forward and backward channels exhibiting independent but not necessarily identically distributed Nakagami-m fading are considered, and the diversity order that the system can achieve is found to be Nmin(m _h, m _g), where N is the number of antennas at the tag and m _h and m _g are the fading parameters corresponding to the forward and backward channels, respectively. The analytical results are verified through comparison with the simulation results.

The channel access method, defined in the IEEE 802.11ac draft, forces stations (STAs) to transmit data over the widest currently available channel supported by the basic service set (BSS). Unfortunately, the transmission in a wide channel is very inefficient if data frames are short. A channel width selection scheme (CWSS) is proposed which reduces the bandwidth used by the STA, if the transmitted data frame is not sufficiently long. Simulation results show that the CWSS allows a better bandwidth utilisation in an environment of overlapping 802.11ac BSSs. The CWSS is compatible with the channel access procedure defined in the IEEE 802.11ac.

Direct conversion transmitters are widely used in wireless systems for their inherent features of being simple and low cost. In this architecture, the inphase (I branch) and quadrature signal (Q branch) will be unconverted to the RF frequency band by quadrature modulation. However, the drawback of the direct conversion architecture is that it is sensitive to IQ imbalance caused by the impairment of analogue devices in I and Q branches. It then results in interferences in mirror frequencies which degrades the signal quality. Therefore, the accurate measurement of IQ imbalance is crucial. A diode-based method to measure the broadband IQ imbalance is proposed which does not need additional measurement instruments. Measurement results show the effectiveness of this method.

Energy has newly become a scarcer resource for the wireless networks, like spectrum. To utilise the limited resources efficiently and fairly in the downlink OFDMA systems, a novel resource allocation problem is investigated to make the balance between energy efficiency (EE) and spectrum efficiency (SE), the tradeoff between fairness and SE/EE. The problem is first formulated as an optimisation problem, which is NP-hard. Then, the existence of an optimal solution is proved, and an algorithm is designed to obtain the optimal solution. Finally, the numerical results show that the proposed algorithm achieves the SE–EE balance and provides a good tradeoff between fairness and SE/EE.

A 600 GHz data transmission using the combination of a photonic emission using a uni-travelling carrier photodiode and an electronic detection is investigated. A high-definition television transmission at this carrier frequency with a very low power at the receiver is reported. Only 10 nW of terahertz (THz) power at 600 GHz was sufficient to ensure a successful high-definition video transmission. This combination of photonics at emission and heterodyne detection lead to achieving THz wireless links with a safe level of electromagnetic exposure.

The IEEE 802.15.6 standard for wireless body area network (WBAN) includes a slotted Aloha based protocol as an option for contention based medium access control. This protocol is different from the long studied classical version in that it has inherent considerations for certain priorities of users. An analytical model is presented for saturation throughput with this protocol in a network that is heterogeneous in user priorities. The model is validated against simulation.