The ability to use low-frequency microwave sensing techniques to see through optically opaque objects is of great interest. One potential solution to the problem of seeing inside buildings and facilities is the use of low-frequency synthetic aperture radar. This provides the advantage of remote sensing and greater coverage than existing through-wall observation techniques. The Bright Sapphire II instrument is a low-frequency wideband quad polar synthetic aperture radar and offers such measurement capability. The first results of airborne trials are presented.

Low-frequency (LF) synthetic aperture radar (SAR) images offer a viable approach to determining the architecture and contents of buildings and underground bunkers via remote sensing. Often however, standard 2D SAR images can be difficult to interpret due to component signatures from different heights being projected into the scene leading to confused results. In this research, measurement results have shown that the full Nyquist 2D aperture scan approach to 3D through-wall LF SAR provides focussed 3D resolution of a wall and contents behind it in a number of frequency bands. Full-scale radar system upgrades are ongoing in order to investigate numerous other scenarios, however in the meantime, sparse 2D aperture scanning investigations have been undertaken with a prototype radar scanner. Whilst this kind of collection cannot achieve the low sidelobe levels of full Nyquist 2D aperture collections, these prototype scanner measurements are much faster to collect, and have shown encouraging results of sufficient image quality to determine the 3D configuration of prominent features in the target scene, albeit with higher sidelobe or image artefact levels.

The use of through-wall radar imagery for remote intelligence of building interiors is promising but challenging. Relevant information about human targets and room layout features is typically buried in clutter. In this Letter, the authors propose a methodology for automated extraction of information about stationary human targets behind walls. Based on treatment of the individual blobs found in the imagery, the method consists of thresholding, segmentation, classification and 3D visualisation. Although further optimisation of each of the steps is required, they demonstrate with two examples, including one cluttered scene, that the combination of these steps is effective at eliminating large amounts of clutter and identifying human targets behind walls.

The development of a through-wall synthetic aperture radar (SAR) simulator, which is being used to investigate the SAR artefacts originating from vibrating target's, known as paired echoes is explained. The simulation and experimental results both show that paired echoes can be detected and imaged through a wall, with a noticeable reduction in intensity, resulting in the number of visible echoes to be reduced in brightness and appear shifted in location in a through-wall SAR image.

Through-wall radar allows for remote intelligence of building interiors including stand-off detection and tracking of persons inside a building. However, reliable radar tracking of people inside a building is not trivial. Conventional, monostatic through-wall radar measures the backscatter of moving people. The backscatter from a human is relatively low compared with the scattering from building features or furniture. The forward scatter radar (FSR) concept is proposed to detect and possibly track moving people in specific areas of a building. The FSR concept exploits the forward scatter (FS) of objects, which is typically larger than their backscatter; for humans a factor of 20 is possible. It is shown that stand-off detection of moving people inside a building can be performed reliably and consistently based on their FS.

A new method for simple and robust in-building motion detection is introduced. The proposed technique relies on a single frequency continuous wave (CW) signal and can therefore be integrated with inexpensive commercial off-the-shelf (COTS) components.

The phenomenology of electrical signatures being unintentionally injected onto the mains electricity supply by a range of common household devices is investigated. Measurements were made of both current time series and voltage spectra of a variety of devices, using commercially available measurement equipment designed for electromagnetic compatibility testing. The measurements give strong evidence that multiple devices can be identified from either their current transient when switched on or off, or their voltage spectrum when running. While some devices are readily identifiable, even in the presence of large amounts of noise, for low power devices it may be necessary to perform filtering of the mains signal to obtain spectra with a suitable signal-to-noise ratio. For certain types of device, spectral signatures of particular instances of the same device appear to be separable in high signal-to-noise ratio environments. For example, it may be possible to identify a specific laptop charger among other chargers of the same make and model. The relevant measurements can be made outside buildings, and when combined with other intelligence, could be used to obtain remote intelligence of building interiors.

A fast tracking system is demonstrated that is based on single laser illumination and a few single-pixel single photon avalanche diode (SPAD) detectors that improves on the previous tracking of non-line-of-sight motion by a factor of 300 in laser power. With an average illumination power of only 2 mW, a 15 cm ×15 cm object located up to 2.5 m away is tracked whilst outside of the direct line-of-sight and moving at approximately 6 cm/s.

A concept and first results of combining multispectral light detection and ranging (LiDAR) with positioning sensors to produce spatially resolved target identification in indoor environment is presented. The aim is to enhance the sensor-based indoor localisation with a multispectral target identification and mapping. There is a growing need for automatic and mobile mapping and surveillance in buildings and locations where satellite positioning is not available. LiDAR is a common sensor in feature-based simultaneous localisation and mapping. As multispectral LiDARs are emerging and becoming increasingly popular in research applications, the multi/hyperspectral point clouds are likely to improve object recognition and enable a new level of autonomous surveillance in the near future. The first results show that position solution can be obtained using sensors attached to the LiDAR.

Effectiveness of early response is critical to the successful outcome of search-and-rescue operations with the likelihood of survival witnessing a steep decline after 72 h. Due to the unpredictable and sudden nature of incidents official response is often slow, resulting in people lacking formal training being responsible for early response. To facilitate these people, low-cost technological solutions for assisting in search-and-rescue missions are introduced. A framework is introduced and three prototypes build around the framework and the suitability of different sensing technologies for assisting search-and-rescue missions is discussed.

A novel method to realise a single-feed circularly polarised (CP) microstrip antenna with wide beamwidth and axial-ratio (AR) beamwidth is investigated. Two diagonal metal walls are put at the diagonal sides of the microstrip antenna. The diagonal metal walls can excite the orthogonal radiation fields with the same amplitude and 90° phase difference on the radiating patch for CP with wide beamwidth and AR beamwidth. Some parameters which effect on the performances of the antenna are studied. The simulated and measured results of the reflection coefficients, radiation patterns and AR radiation patterns are presented. The 3-dB beamwidths of the right-hand CP (RHCP) radiation patterns in the xoz-plane and the yoz-plane are 105° and 157°, respectively. The 3-dB AR beamwidths of the RHCP radiation patterns in the xoz-plane and yoz-plane are 100° and 155°, respectively. Good CP characteristics of the new structure antenna have been obtained in the whole operating frequency band.

A single-feed circularly polarised (CP) patch antenna loaded with a single dielectric superstrate for a wideband high-gain CP radiation is presented. Along with the gain enhancement, the emphasis is on extra CP radiation of the antenna caused by the superstrate, which broadens the axial-ratio (AR) bandwidth significantly. A prototype antenna was fabricated and measured at a frequency of 11 GHz. The antenna with overall size of 40 × 40 × 17.45 mm has a voltage standing wave ratio <2 bandwidth of 24.35% (10.1–12.9 GHz), a 3 dB AR bandwidth of 13.6% (10.3–11.8 GHz), a peak gain of 13.17 dBic, a 3 dB gain bandwidth of >26% (10.0–13.0 GHz), and a radiation efficiency of >90%. The presence of superstrate produces a ∼350% increase in 3 dB AR bandwidth and a ∼7 dB increase in the broadside gain relative to the conventional CP patch antenna.

A compact bi-directional leaky-wave antenna (LWA) based on TE₂₀ mode substrate integrated waveguide (SIW) is proposed at X-band. The microstrip power divider–slotline transitions are utilised to excite TE₂₀ mode SIW array in order to enhance the overall radiation capability of the designed structure. The rectangular slots are etched out on the top and bottom plane of SIW such a way that the orientation of the slots can perturb the distribution of electric field at TE₂₀ mode and provide bi-directional radiation. The proposed antenna is working within the frequency range of 9.6–11.2 GHz (S ₁₁ < −10 dB) having the beam scanning range of 66° from both top and bottom side of the structure with maximum gain of 14 dBi. All experimental results show a fair agreement with the simulated data.

A novel differential-fed dipole antenna with compact size is proposed and investigated. The size of the antenna is only 0.8λ ₀ × 0.8λ ₀ × 0.13λ ₀ (where λ ₀ is the free-space wavelength at the centre frequency). By utilising a pair of complementary sources, the antenna achieves good unidirectional radiation performances. The antenna has an impedance bandwidth of 38.5% for from 1.63 to 2.4 GHz. The boresight gain ranges from 7.8 to 9.6 dBi. The cross-polarisation level is lower than −25 dB while the front-to-back ratio is above 12 dB across the operating frequency band. Moreover, the antenna is simple structured and easy to be fabricated.

An effective method to design an ultra-wideband antenna using a vertical narrow strip element is described. The proposed low profile antenna has good radiation characteristics such as polarisation purity, omnidirectional radiation pattern and good efficiency over the entire band of operation, which are the most desirable characteristics required for a wireless system to operate in the present high interference environment. The designed antenna has a measured return loss of below −10 dB and low cross polarised uniform omnidirectional pattern measured in anechoic chamber for the frequency range of 2.85 to 10.6 GHz.

The authors report on the implementation of a path planning algorithm on the TrueNorth neurosynaptic system. Their implementation exploits processing in the temporal domain within the architectural constraints of the TrueNorth chip to deduce the optimal path. The optimal path is computed on the TrueNorth chip for grid maps with dimensions as large as 173 × 168 nodes consuming ∼70 mW at an operating voltage of 0.8 V.

The impedance and dielectric properties of biological samples are often used to estimate the number of cells growing in a culture, and monitor the cell growth in real time. For these type of studies, high-cost and complex commercial equipment is often required. The design and implementation of a standalone device for impedance spectroscopy of cell samples is presented, featuring low cost, portability and easy reconfigurability of frequency and voltage. The device can generate sinusoidal, square and triangular signals with frequencies up to 125 kHz, at voltages in the range from 0 V to 100 mV. Cell growth experiments were carried out with yeast cultures, and the results are compared with a commercial Agilent 4284A LCR meter. The error percentages for magnitude and phase measurements are <5%.

The extended Kalman filter (EKF) has been widely used in communication, signal processing and navigation control. In this Letter, the authors applied EKF, for the first time to their knowledge, to simultaneously estimate fluorescence lifetimes and instrument response functions (IRF) for time-domain fluorescence lifetime imaging microscopy (FLIM) systems (we focus on gating and time-correlated single-photon counting techniques in this work). Monte-Carlo simulations were performed to test its performances in comparison with previously reported methods. Simulation results show that the proposed algorithm can achieve comparable or better results than the others. More importantly, with EKF there is no need to measure the IRF of the FLIM system.

The demand of the fast acquisition in 3D ultrasound (3D-US) imaging leads to the dense population of speckle noise which causes the difficulty in medical diagnosis. In this Letter, 3Dadaptive regularisation Savitzky–Golay (3D ARSG) filter is proposed as the real-time filter for removing speckle noise in 3D-US imaging. The 3D ARSG filter uses the local intensity homogeneity to classify between noisy and texture regions. The intensity in the noisy regions is heavily smoothed, while the resolvable edges remain sharp. The experiment on the denoising of the 3D simulated models and the 3D-US images indicated that 3D ARSG filter provided the image with far less noise and crisper objects’ boundary than conventional methods. In addition, the proposed filter preserves the structural details with regard to the dimension and can denoise images in real time.

A phase-locked loop (PLL) architecture based on a 2D phase comparator matrix is introduced. In its general form, multiple phases of the input reference clock are compared with multiple phases of the feedback clock, allowing for wider bandwidth (BW) and lower phase noise generation of the PLL. Based on matrix phase detector architecture, a 6.25 GHz PLL achieving 5 GHz BW and exhibiting 55 fs-rms jitter is designed in 28 nm CMOS bulk technology.

A novel rotor position estimation method for doubly salient EM motor (DSEM) sensorless startup is proposed. On the basis of the feature the series self-inductances of two energised phases are the greatest among all of the three two-phase series self-inductances under the basic conduction mode of DSEM, the voltage vector of next conduction state is selected as the test pulse which is injected for rotor position estimation. Moreover, the acceleration pulse, traditionally injected only for speedup, is newly proposed to be utilised for rotor position estimation. The rotor sector is obtained by comparing the two response currents, one of which is sampled at the end of test pulse, and the other is sampled when the acceleration pulse lasts to the duration of test pulse. Since only one test pulse is required, the sensorless startup performance of DSEM is improved in terms of less test time consuming, smaller estimation error as well as greater output torque. The experiments on a 12/8-pole DSEM validate the correctness of the proposed rotor position estimation method.

A new license plate detection method for challenging environments is proposed. Background clutters are common in road scene images and the detection of license plates (occupying only a small part of an image) is considered as a difficult problem. In order to address this problem, a two-step approach is developed: first vehicle regions are detected and the license plate in each vehicle region is localised. This vehicle region detection based approach provides scale information and limits search ranges in license plate detection, so that one can reliably detect license plate regions. To be precise, the faster region-based convolutional neural network algorithm for the vehicle region detection is adopted and candidates for license plates in each detected region with the hierarchical sampling method are generated. Finally, non-plate candidates are filtered out by training a deep convolutional neural network. The proposed method is evaluated on the Caltech dataset and the method showed a precision of 98.39% and a recall of 96.83%, which outperforms conventional methods.

Decision fusion is the most important step in ensemble machine learning schemes. One of the greatest challenges of decision fusion is the discrete nature of decisions. This challenge causes decision fusion solutions to become variations of the voting algorithm from statistical perspective. However, increasing the redundancy of decisions imposes a serious computational challenge for real-time systems. Resorting to fewer decisions imposes uncertainty challenges. In this Letter, the authors present a methodology to generate saliency maps for decision fusion. Specifically, they propose a local saliency map for decision fusion using a local majority filter. They choose semantic segmentation via pixel labelling produced from a random decision forest model as a case study. The local saliency map is used to derive three intermediate labelled images that are added to the voting pool and hence rectifying the final decision. The results of the proposed solution reduced the error by 26% and increased robustness by 16% with only two decisions.

To display massive data accurately and in real time, a visualisation algorithm based on the viewpoint motion model is proposed. A Hilbert-R tree is constructed to index massive data. Further, the massive data is divided into a visible area, a potential area, and an unloading area using the viewpoint motion model. According to the index, corresponding data blocks are loaded into the memory, and data blocks of the visible area further transferred into the graphic processing unit (GPU) memory for rendering. When the viewpoint is changed, the data block of the potential area in the memory is directly loaded into the GPU. Experimental results show that under the premise of ensuring the quality of rendering, massive data can be displayed interactively, and the speed of displaying increases by 36–78%.

A new multimodal object description network (MODN) model for dense captioning is proposed. The proposed model is constructed by using a vision module and a language module. As for vision module, the modified faster regions-convolution neural network (R-CNN) is used to detect the salient objects and extract their inherited features. The language module combines the semantics features with the object features obtained from the vision module and calculate the probability distribution of each word in the sentence. Compared with existing methods, a multimodal layer in the proposed MODN framework is adopted which can effectively extract discriminant information from both object and semantic features. Moreover, MODN can generate object description rapidly without external region proposal. The effectiveness of MODN on the famous VOC2007 dataset and Visual Genome dataset is verified.

Balancing diversity and accuracy of individuals is crucial for improving the performance of an ensemble system, since they are two important but incompatible factors for ensemble learning. When multiple individuals are combined with the corresponding weights, the diversity should be dominated by individuals and their weights, whereas the weights are normally ignored in the analysis of diversity in most research. Inspired by this, the authors propose a novel ensemble method which seeks an optimal combination to maximise diversity and accuracy of weighted individuals with the constraint on the minimal ensemble error. Furthermore, a new expression is given based on the generated individuals and their weights to exploit the diversity of an ensemble. Experimental results illustrate that the proposed method outperforms relevant existing methods.

When observing a scene by a perspective camera through multiple refractive planes (e.g. underwater imaging), distortions and illusions, mainly caused by the refractions occurring at the interfaces between the different mediums, will be brought into the imaging system. Traditional pin-hole camera model becomes invalid in handling such case. A novel general camera model is presented, which is in fact a virtual pixel-wise varifocal model and can be used to encode multilayer refractions effectively. The model is built up based on two important findings. One is that the air between the camera centre and the nearest layer can be modelled as an air layer. The other one is that a ray passing through the air layer and these multiple layers causes only lateral displacement without changing its direction. The proposed camera model guarantees fast calculation of the backward projection. The forward projection equation is also derived and an efficient solving algorithm is proposed. Synthetic and real experiments are designed to verify the effectiveness and efficiency of the proposed theory.

Although action recognition is a widely studied field in computer vision, the recognitions of aggressive activities and crowd violence actions are comparatively less studied. Nowadays, so many surveillance cameras have been installed in the streets and there is a demand for intelligent crowd activity detection systems. A method for violence detection in videos is proposed. The primary contribution is a novel transfer learning-based violence detector that gives promising results compared with the existing detectors. First, the optical flows of the input videos are computed via Lucas–Kanade method. Then, several 2D templates are constructed with overlapping optical flow magnitudes and orientations. These templates are supplied to a pre-trained convolutional neural network as input and deep features of different layers are extracted. Cubic kernel support vector machine and subspace k-nearest neighbours classifiers are trained for prediction and the proposed method is tested with three different datasets that commonly used in violence detection studies.

A quintuple-mode wideband filter based on a single cavity is proposed. A pair of shorting pins is inserted into the cuboid cavity along the symmetry plane. The cavity filter is fed by a pair of coaxial cables and the inner conductor is inserted into the cavity with a circular disc at the end of the probe. The pair of inserted probes and the pair of shorting pins excite five resonant modes in the cavity. The proposed filter has the central frequency at 5.8 GHz with a bandwidth of 70%. Meanwhile the wideband filter has transmission zeros at the lower and upper-stopbands to improve the selectivity and out-of-band performance. The measured insertion loss is <0.65 dB, and all measured results have a reasonably good agreement with the simulated results.

A compact microstrip low-pass filter (LPF) with ultra-wide stopband using the analysed triangular-shaped resonator is presented. To achieve LC equivalent circuit of the triangular-shaped resonator, the structure of a rectangular-shaped resonator is adopted. To investigate the behaviour of the proposed triangular-shaped resonator, transfer function of the main triangular resonator is calculated. The designed LPF has −3 dB cut-off frequency of 1.52 GHz with the stopband bandwidth around 12fc and total circuit size of 0.062λ_g × 0.104λ_g . The proposed LPF has the figure of merit of 46,718, which shows its good performance. The proposed filter is designed, simulated and fabricated. It is observed that the measurement results are well matched with simulation results.

A compact and high-performance microstrip diplexer is designed by using stub-loaded parallel-coupled lines and half-wavelength resonators. First, the traditional equivalent circuit of the parallel-coupled line is extended to consider the length effect of the loaded stub. Second, by choosing the length of the stub, the multiple transmission zeros can be introduced and allocated to reduce the coupling between two signal channels and improve the isolation between two out-put ports. Finally, a prototype of the proposed microstrip diplexer is designed and fabricated. The simulated insertion losses are 1.34 dB at 1.8 GHz (first band) and 1.28 dB at 2.4 GHz (second band), while the measured ones achieve 1.54 and 1.47 dB, respectively. More than 40-dB isolation level is obtained over the whole concerned frequency range.

The fabrication and analysis of a flexible and stretchable 3D printed passive ultra-high frequency (UHF) radio-frequency identification (RFID) tag are presented. The tag is fabricated on a flexible 3D printed Ninjaflex substrate and the conductive part of the tag consists of stretchable silver conductive paste dispensed with direct write method. The details of the 3D printing of the substrate, the characterisation of the substrate material at the UHF band, the direct write dispensing of the tag antenna, and the simulation and wireless measurement results of the fabricated tag are outlined. Moreover, to verify the flexibility and stretchability of the tag, strain reliability results of the tag are presented. Measurement results show that initially the manufactured tag achieves a 10.6 m read range. After 100 times of harsh stretching, the read range is still 7.4 m. Overall, the performance of the tag is robust and concludes that the fabrication methodology can be used in the manufacturing of RFID tags for future identification and sensing applications.

A wide-stopband Wilkinson power divider (WPD) is proposed, which can be realised by using open dual-transmission line (TL) stub and L-type artificial lowpass TL structures. To further achieve miniaturisation, synthetic TLs are also employed. The simulated and measured results are consistent, and the measured |S ₂₁| and |S ₃₁| (insertion losses) have shown stop-bandwidth of larger than 18.33 GHz (1.67–20 GHz) and 18.28 GHz (1.72–20 GHz), respectively, under the condition of 30 dB harmonic suppression level. The wide-stopband of the WPD can cover 2f_o –22.2f_o (f_o = 0.9 GHz), and the occupied area of the WPD (not include the feeding network) is only 0.11λ _g × 0.06λ _g (λ _g: guided wavelength at f_o ).

A reflection-type microwave amplifier using InP-based resonant tunnelling diodes (RTDs) has been designed and fabricated. The implemented amplifier shows a low dc-power consumption of 270 μW with RF gains of more than 11 dB at 5.61 GHz. Temperature-dependent characteristics of the RTD amplifier have been investigated at a high temperature. With increasing temperature from 25 to 100°C, the centre frequency shift was measured to be 60 MHz. The RF gains (S ₂₁/S ₁₂) and the return losses (S ₁₁/S ₂₂) of the amplifier decreased from 11.45/11.32 and −7.96/−8.11 dB at 25°C to 7.06/6.91 and −11.36/−11.15 dB at 100°C, respectively. The S-parameter degradation phenomena are shown to mainly arise from the temperature dependence of the negative differential resistance (R _D) characteristic for the fabricated RTD.

A novel high-step-up DC/DC converter (HSUDC) is proposed and then the expression of power-loss calculation to estimate the efficiency of the converter is derived. The HSUDC can work at interleaved manner and mainly includes two power switches, four diodes, two coupled inductors and three capacitors. It can step up a low voltage to a much higher level for further grid-connection applications, which are therefore suitable to process the power generated by distrusted energy resources. Magnitude of power loss dominates the power density of a converter. Therefore, a theoretical and systematic estimation for HSUDC is developed, advancing the compact design towards converter building. Estimated results are compared with the practical measurements from a prototype to verify the correctness of the estimation.

To cope with the current imbalance situation of multi-phase buck converters with wide duty ratio range applications in continuous conduction mode (CCM) and discontinuous conduction mode (DCM), a current-balance method is proposed. In CCM, with small power loss, current balance can be achieved by comparing the replica currents flowing through the sensing transistors. In DCM, an additional offset cancellation circuit is designed to eliminate the intrinsic offset voltage mismatch existing in main-loop comparators. Then each phase sequentially performs a switching operation to share the switching stress. Experimental results show that the current imbalance is decreased to 0.15% under duty ratio from 0.1 to 0.75. Load current is well distributed between phases in both the CCM and DCM without tricky implement.

A dual-passive snubber (DPS) for dual-switch forward converter is presented. Snubber networks provide zero-current turn-on and zero-voltage turn-off conditions for dual switches. DPS achieves soft switching conditions for power diodes at secondary side of transformer. The detailed circuit operation of converter with proposed passive snubber, theoretical analysis and design example are presented. The measured result taken from a laboratory prototype rated at 160 W (32 V/5 A), input voltage of 150 V-DC and switching frequency of 300 kHz. The peak efficiency is 93%.

A generalised n-level multilevel converter that has no shoot-through problem and thus is operated without dead time at each commutation is proposed. It is obtained by modifying the traditional neutral-point clamped multilevel converter topology based on dual-buck converter concept. The m-phase n-level converter can be readily constructed by using the proposed multilevel converter topology. The half-bridge five-level inverter, as an example case, is presented along with the operating principle and modulation and control methods. Experimental results show the feasibility and validity of the proposed converter.

A comparative evaluation of the different, very popular powder magnetic materials for a voltage source inverter output filter coil core is presented. The basic continuous model of the inverter is simply based on the output filter transfer function. This model is used in the majority of inverter control designs. That is why the change of inductance and the increase of the equivalent serial resistance that is caused by power losses in the core and any other parasitic parameters of the coil should be known in the operating point because they depend on the frequency and the amplitude of the magnetising current. The theoretical calculation of these parameters variability is very inaccurate because of the complex voltage waveform on the coil, so the direct measurements of the inverter control transfer function are presented in aim to enable the choice of the most useful magnetic material for the inverter design.

For small slowly moving targets detection in spiky sea clutter, a fast scan-to-scan integration preprocessing algorithm is proposed. By introducing a velocity steering vector, the scan-to-scan integration is achieved by matrix operations instead of traditional target path searching algorithms. The concept is demonstrated using measured data collected from an airborne maritime surveillance radar. Results show that the computation complexity of the back-end track-before-detect block can be reduced by two orders under the considered scenario.

A compact design for a 2.5 kW solid-state power amplifier (PA) based on 330-W laterally diffused metal–oxide semiconductor transistors over 1.2–1.4 GHz is proposed. The design procedure is started with the design and implementation of a 330-W unit amplifier (UA) independently. Optimum load and source impedances of the UA are obtained by pulling the source and load impedances with the aid of the simulator utility provided in Advanced Design System. The input–output matching networks are designed and implemented using multi-section microstrip transmission lines. In order to construct a 2.5-kW high PA (HPA), the eight pieces of designed UA are combined. A low-loss 1–8 way planar binary power divider with an 8–1 way planar binary power combiner is used to divide and combine the microwave signals through eight UAs. The HPA delivers 63.7–64.3 dBm output power with 16.7–17.3 dB power gain and 55–60.4% power-added efficiency over 1.2–1.4 GHz. To the best of the authors' knowledge, the most compact HPA design using packaged transistor at L-band with such high output power level ever reported is presented.

Industrial WLAN devices suffer from interface delay and poor CPU performance, which would incur an inevitable cost of throughput for aggregation schemes. An enhanced aggregation scheduler is proposed. In this proposed method, the originator's behaviour in both the upper media access control (MAC) and the lower MAC layer is modified. The originator pre-stores subframes of the next aggregated data units despite that the block Ack is not received. Through utilising the modified method, the hardware delay overhead was minimised. Implementation on own chipset indicates that with this aggregation scheduler, higher throughput can be achieved than conventional scheduler, especially when using high rates.

A round-robin transmission model is proposed for machine-type communication gateways (MTCGs) served by long-time evolution e-NodeBs (eNBs). The function of the MTCGs is to collect and buffer data from their subscribed MTC devices (MTCDs) until they are served by an eNB. The service of each MTCG follows an independent and identically distributed G/G/1 queue model, which can be employed with any distribution according to the MTCD traffic characteristics. The system performance is analysed based on queuing theory.