A cascaded circular-polarisation-selective surface (CPSS) based on bisected split rings is presented. The proposed CPSS allows the transmission of one sense of circular polarisation while reflecting the other sense. To validate the proposed design, a nine-layer prototype that operates in the Ka band has been designed, fabricated and tested. Experimental results show that transmission coefficients higher than −1 dB and axial ratios lower than 3 dB are obtained for one sense of circular polarisation, whereas transmission coefficients lower than −20 dB are obtained for the opposite sense over the frequency band from 26.39 to 35.43 GHz.

A compact asymmetric coplanar strip (ACS)-fed ultra-wideband (UWB) antenna for diversity applications is presented. The proposed antenna is composed of two circular radiating elements and orthogonal ACS-fed mechanisms to achieve diversity performance across the UWB from 2.66 to 11.08 GHz, and occupies a very compact size of 28.5 × 28.5 mm². By introducing a rectangular stub diagonally between the two circular radiating elements, an interport isolation better than 15 dB is achieved. Furthermore, the proposed antenna shows nearly omnidirectional radiation patterns, stable gains and a low envelope correction coefficient. The simple feeding structure, compact size and uniplanar design make it easy to be integrated within the portable device for wireless communications with diversity operations.

A dual-band coplanar waveguide (CPW)-fed bow-tie slot antenna is proposed, which consists of a bow-tie slot, a pair of sector parasitic patches and a modified grounded plane with a band-notch property. The impedance matching, the resonant mode, the radiation patterns and the current distributions are studied. To generate dual-band characteristics, a V-shaped slot is etched on the radiating ground. Experimental and simulated results demonstrate that the antenna exhibits two separate impedance bandwidths of 1450 MHz (about 32.8% centred at 4.43 GHz) and 3500 MHz (about 37.8% centred at 9.25 GHz), which satisfy aircraft radar and X-band applications.

A novel artificial magnetic conductor based on a low-profile implementation of a capacitively loaded resonant structure is presented, with increased performance in terms of miniaturisation. In addition, a comprehensive analysis of all the parameters involved in downsizing is provided, establishing a fair methodology for comparing the performance of different size reduction strategies.

In [1] the authors present a charge/flux formulation of the equations of memristive circuits, which seemingly show that the memristor should not be considered as a dynamic circuit element. Here, is shown that this approach implicitly reduces the dynamic analysis to a certain subset of the state space in such a way that the dynamic contribution of memristors is hidden. This reduction might entail a substantial loss of information, regarding e.g. the local stability properties of the circuit. Two examples illustrate this. It is concluded that the memristor, even with its unconventional features, must be considered as a dynamic element.

The Comment of Riaza is acknowledged. In response, it is argued that by establishing the complete corresponding relations between the voltage-current relation and the constitutive relation of memristors, the conclusions in the original Letter are appropriate. It is further illustrated that if the voltage-current model is used, the memristor is regarded as a dynamic element, whereas if the flux–charge model is utilised, the memristor is treated as a non-dynamic element. The results indicate that the memristor initial conditions described by the constitutive relation should be assigned in the modelling of memristive circuits, and the dynamic nature of memristors is related with the memristive circuit model.

Intra-prediction in high-efficiency video coding (HEVC), in comparison with previous video coding standards, provides higher coding efficiency, at the expense of increased computational complexity. The coding efficiency is increased, mainly due to the various transform block sizes and increased number of modes. An efficient bottom-up pruning algorithm for mode decision is presented, to reduce the computational load of intra-prediction. Experimental results show that the proposed algorithm achieves about 39% reduction in mode decision time in intra-prediction, compared with the HEVC test model 11.0, with negligible coding gain degradation.

A novel hashing scheme based on a deep network architecture is proposed to tackle semantic similarity problems. The proposed methodology utilises the ability of deep networks to learn nonlinear representations of the input features. The equivalence of the neuron layer and the sigmoid smoothed hash functions is introduced, and by incorporating the saturation and orthogonality regulariser, the final compact binary embeddings can be achieved. The experiments illustrate that the proposed scheme exhibits superior improvement compared with conventional hashing methods.

An error-correcting code (ECC) immune to bit errors can make memory performance severely degraded since incomplete-word ECC write requests lead to inefficient operations on a dual in-line memory module (DIMM). A DIMM controller efficient for such ECC operations is proposed. The key idea is that read-to-write and write-to-read operations caused by incomplete-word ECC write requests are split into independent read and write operations, and then the read and write operations are individually scheduled under data coherence constraints. Experimental results show that the proposed DIMM controller achieves 11% shorter memory latency, and 9.3% higher memory utilisation, on average, than the latest conventional DIMM controller in industrial multimedia applications. Moreover, it achieves up to 2.1 times higher memory performance on synthetic benchmarks.

The block orthogonal matching pursuit (BOMP) algorithm aims to recover block sparse signals whose non-zero components have a block structure. Sensing and measurement dictionaries are alternatively optimised to have small inter- and sub-block mutual coherences. The computational complexity of the proposed algorithm is low. With the designed dictionaries, the performance of the BOMP algorithm improves.

Magnetic random access memory based on magnetic tunnel junctions (MTJs) is among the most attractive technologies of emerging non-volatile memories. However, the integration of spin-based devices in integrated circuits is still hindered by a lack of established standard electrical simulator models. Many of such models have been proposed during the past decade which can be classified into two categories: the first ones are based on the physical Landau-Lifshitz-Gilbert (LLG) equation describing real-time MTJ magnetic switching dynamics; the second one uses analytical expressions for switching thresholds derived from the LLG equation. The aim of this reported work was to investigate for the first time the capability of each strategy to fulfil the need of industrial standard electrical simulation tools and pave the path towards a standard industrial model. Multi-simulator compatibility, efficient runtime, accuracy and reliability are the three main assets of a device model. It is shown that using the Cadence^® tools suite with the Spectre^® simulator, the LLG modelling strategy overcomes the analytical approach in terms of accuracy and speed with a 7× faster runtime. Both models require nearly the same hardware memory resources.

A broadband right-angle transition from a substrate-integrated waveguide (SIW) to a rectangular waveguide (RWG) is proposed. A coupling aperture etched on the broad wall of the SIW and two stepped ridges embedded in the RWG flange are designed for good matching between both waveguides. A Ka-band prototype is designed and fabricated. Good agreement between the measured and simulated results is obtained. The measured results show an insertion loss <0.55 dB and a return loss below −15 dB from 31.3 to 38.35 GHz. This broadband transition may be used in microwave and millimetre-wave circuits and systems.

A tunable helical bandpass filter with high selectivity designed for 30–88 MHz operation is presented. The two-pole tunable filter is discretely tuned by connecting PIN switched capacitor banks at the terminal ends of the helix. The filter schematic provides two finite transmission zeros located in the lower and upper stopbands, respectively. The experimental filter has an insertion loss between 1.65 and 2.75 dB with its return loss better than 13 dB. The 3-dB fractional bandwidth of the filter is 3.3%–3.7% and the shape factor (BW_{30 dB}/BW_{3 dB}) is smaller than 5.5 over the entire tuning range. The input power handling capability is greater than 45 dBm. The measured results show good agreement with the simulated ones.

A technique to implement and control the bandwidth of notch bands in an ultra-wideband (UWB) bandpass filter (BPF) based on signal superposition is described. The filter is realised by employing two wideband BPFs in a parallel configuration to establish two signal paths between input/output ports. The proposed technique can substantially increase the bandwidth of the notch band by ∼370% in comparison with the notch-band filter designs based on transversal signal interaction. The proposed filter exhibits a quasi-elliptical response over the span of the UWB spectrum defined by the Federal Communication Commission. The compact filter design has a size of 88.92 mm².

Miniaturised stacked-coil radio-frequency (RF) transformers were fabricated with thick metal layers using the low-cost anodised aluminium substrate process. The transformer consists of a 34 μm-thick substrate-buried copper lower coil and a 30 μm-thick copper/gold upper coil with a 3 μm-thick benzocyclobutene (BCB) interlayer between the coils. Owing to extremely low losses and tight coupling, the fabricated transformers achieved very low insertion losses as low as 0.28 dB and high maximum available gains of up to 0.96 at GHz frequencies. The results verify that the stacked-coil transformer with thick metal layers can be a promising component for high-performance miniaturised RF circuits.

A Ku-band high-power and high-power-added efficiency (PAE) high-power amplifier (HPA) monolithic microwave-integrated circuit (MMIC) is demonstrated with a 0.25 μm gallium nitride (GaN) high electron mobility transistor technology on a silicon carbide substrate. Measured continuous-wave performances for the two-stage HPA in-fixture exhibit 17.5–18.3 W of output power (P _OUT) and 36.4–39.5% of PAE over the frequency range of 13.5–14.5 GHz. The fabricated two-stage HPA MMIC with all matching networks is as small as 3.3 × 3.5 mm, generating an output power density of 1522 mW/mm².

A planar low-temperature cofired ceramic helical bandpass filter with a compact size is presented. The proposed filter is constructed from short-circuited λ_g /4 helical resonators, while the size is reduced significantly by winding resonators vertically. Two single-sided transmission zeros can be created by the proposed mixed electric and magnetic coupling structure. A prototype with size of 6.2 × 4 mm² (0.049 × 0.032λ_g ²) has been fabricated for demonstration. The measured fractional bandwidth is 5.9% at 0.845 GHz, and two transmission zeros are observed at 0.90 and 1.07 GHz.

A compact branch-line coupler with an ultra-wide upper stopband is proposed based on a new type of transmission line. Consistent numerical and measurement results of the coupler are shown. The proposed branch-line coupler operating at 0.875 GHz exhibits a stopband from 2.8 to 12.9 GHz with suppression levels better than −20 dB. The occupied size of the proposed branch-line coupler is only 17.6% that of a conventional one operating at the same frequency.

One order of magnitude detection enhancement of bow-tie-shaped InGaAs-based terahertz detectors by on-chip incorporation of the secondary diffractive optics is reported. Zone plates were produced directly on the bottom surface of 500 µm-thick InP substrate using the direct laser write technique after an array of InGaAs detectors was formed on the front surface of the wafer. Measurements of detected signal dependence on the angle of the incident wave were performed at 0.76 THz and compared with finite-difference time-domain simulation results. Good correlation of the results shows that the observed enhancement is indeed caused by the focusing performance of the zone plate rather than by the exceptional sensitivity of the single detector.

A new design of oxide-confined 980 nm vertical-cavity surface-emitting lasers (VCSELs) particularly well-suited for very-short-reach (∼2 m and shorter) optical interconnects is presented. A new record for temperature-stable high bit rate VCSELs is achieved. Error-free data transmission at 46 Gbit/s is achieved up to a record-high temperature of 85°C. The maximum bit rate and −3 dB bandwidth at room temperature are 50 Gbit/s and 24.7 GHz, respectively.

A 2-tap low-swing voltage-mode transmitter which compensates the loss of channel at high frequency is proposed. The output driver of the proposed 2-tap transmitter consists of only two voltage-mode drivers, and thereby the design complexity of the pre-driver is greatly reduced compared with that of conventional 2 ^N -segmented voltage-mode drivers, where N is the number of equalisation control bits. The output impedance of each voltage-mode driver is adjusted not only to make the overall output impedance matched with the characteristic impedance of the channel, but also to achieve the desired equalisation coefficient by adopting the proposed calibration circuitry. With a high equalisation coefficient, the proposed output driver consumes less power compared with the hybrid voltage-mode driver with current-mode equalisation. The proposed transmitter is implemented using a 90 nm low-power CMOS process technology and achieves 0.79 pJ/bit without equalisation and 0.98 pJ/bit with 6 dB equalisation, at the data rate of 5 Gbit/s.

The depth-dependent changes of macroporous etching in aqueous hydrofluoric (HF) solutions are addressed. Macroporous etching of n-type silicon in HF acid produces high aspect ratio structures. However, an irregular etch profile can emerge as the pore depth increases, in particular branched regions emerging from vertical pores. The root cause of this non-ideal etch profile is investigated, focusing on the dark current component of electrochemical etching. The dark current during etch progression was simulated, and it was found that increased dark current resulted from increasing the interfacial contact between the electrolyte and silicon surface. A software-mediated photocurrent compensation method is developed that periodically samples the dark current component of the etch and adjusts the overall etch current, achieving stable pore formation.

A multi-pixel 64 × 48 time-of-flight (TOF) range sensor whose speciality is high immunity against ambient light is presented. The chip was fabricated in a 0.35 µm 1P4M CMOS process, whereby a single pixel occupies an area of 45 × 60 µm² achieving a fill factor of 50%. The measured distance shows a 1σ deviation below 3.7 mm in the optimum operating range for the sensor. The measurement results show that the sensor successfully acquires the distance even when some parts of the scenery are illuminated with 180 klx ambient light. Furthermore, the most accurate method to characterise particular pixels in a multi-pixel array is for the first time used in a multi-pixel TOF sensor.

Interposers for inter-chip interconnects should perform stably under high-temperature conditions and rapid temperature change due to the heat generated by mounted large-scale integration (LSI) chips. Athermal silicon optical interposers integrated with quantum dot lasers and other temperature-insensitive components on a single silicon substrate are demonstrated, and error-free data links at 12.5 Gbit/s operating from 25 to 125°C are achieved without any bias adjustment. Since maximum junction temperatures in most LSIs have been below 125°C now and will be in the future, the interposers are tolerant of heat generated by LSIs, and are suitable for inter-chip interconnects.

GaSb-based type-I quantum well laterally coupled distributed feedback diode lasers emitting in the methane absorption band near 3.27 µm were designed and fabricated. The first-order index grating with a period of 480 nm was defined by e-beam lithography and etched on both sides of 6 µm-wide shallow ridge waveguide. Coated 2 mm-long devices demonstrated stable continuous-wave single-frequency operation in a wide temperature range with an output power of 15 mW at +17°C and 40 mW at −20°C. The Bragg wavelength temperature tuning rate was ∼0.27 nm/K.

The rate-equation model for a semiconductor laser under optical feedback is a useful tool for studying complex laser dynamics. Optical feedback from scatterers suspended in fluid flow and rough bodies in motion consists of many, spectrally close, Doppler-shifted frequency components with random phase. How this type of feedback is included in the well-established Lang and Kobayashi model is clarified, resulting in simulated results that agree well with the experiment in both time and frequency domains. Equipped with this model, the dynamic effects of laser feedback systems measuring flow or rough targets in motion may be studied numerically.

A theoretical model is established to reveal the change of thermal strain distribution due to temperature variation in a quadrupolar fibre coil without a spool. In the proposed model, the change of fibre coil thermal strain is calculated by considering both the thermal expansion of the fibre itself and the expansion of the curing glue adhered. Moreover, four experiments are performed which measure the fibre coil strain by a stress analyser in 0, 25, 40 and 50°C. Experimental results show excellent agreement with theoretical values, which verifies the proposed model.

A new method of splicing polymer optical fibres by irradiation of megahertz ultrasonic waves is demonstrated. The lowest connection loss of 1.5 dB is obtained at 2 MHz, and a high mechanical strength of 59 N (close to the strength of the base polymer) is achieved at 1 MHz. It is shown that the loss and strength are in a trade-off relationship, and that the duration of ultrasonic irradiation has a certain optimal value of ∼1 s.

A novel scheme with an antenna array and a vector delay lock loop (VDLL) is proposed for improving the anti-jamming capability of the global positioning system (GPS) receiver. The VDLL is used to supply reference information relying on the unique structure of the coarse/acquisition code for blind beamformers. A spectral self-coherent restoral with a sparse constraint algorithm is presented to suppress interference and preserve the satellite signal without the direction of arrival of the satellite signal. Simulation results show that the proposed method can not only successfully suppress interference but also ensure the reliability of the VDLL in the presence of interference.

The issue of extracting micro-Doppler (mD) information of the coning target radar echoes with or without Doppler aliasing is considered using scattering centre reconstruction combined with the time–frequency analysis (TFA) method. The effectiveness of the presented method is investigated using real measured radar signal experiments. For radar echoes without Doppler aliasing, extraction of the mD information of the coning target using traditional TFA can be obtained. However, using the presented method the mD information is more precise. For radar echoes with Doppler aliasing, there are significant differences in precision between the traditional TFA and the presented methods, and the mD information is smeared using the traditional TFA. Nevertheless, the extraction of mD information can be achieved by the presented method.

Airborne circular stripmap synthetic aperture radar (CSSAR) has the advantages of short revisit time and large coverage, and thus is an attractive tool for wide-area surveillance and ground moving-target indication (GMTI). To enhance the CSSAR/GMTI system's surveillance capability and moving-target detection performance, an efficient imaging algorithm is proposed. The proposed algorithm can finely focus the stationary scene and coarsely focus multiple moving targets simultaneously without a priori knowledge of the targets’ motion parameters and position parameters. Moreover, the proposed algorithm is interpolation free and can be efficiently implemented using only complex multiplications and fast Fourier transforms. Simulation results validate the proposed algorithm.

Low power levels of global positioning system (GPS) signals make them susceptible to radio frequency interference (RFI) from intentional or unintentional sources. Reliance of safety critical and modern applications on GPS has made GPS critical infrastructure which must be protected. Time-difference-of-arrival (TDOA) is a common approach for locating emitters. The TDOAs are estimated by correlating signals received at different sensor nodes. However, RFI detection can be hampered by the in-band GPS signals which create undesired correlation peaks that can be mistaken for weak RFI. A sub-space projection-based approach for removing the GPS signals and leaving the RFI is proposed, and its performance is evaluated using signals from two synchronised Spirent GPS signal generators captured using a NordNav multi-front-end receiver. The results show that the proposed approach can remove the GPS signals, resulting in better RFI detection and localisation performance under various scenarios.

The impact on the extracted low-frequency noise (LFN) parameter values due to LFN variability in CMOS devices is investigated. First, it is demonstrated that the noise level dispersion follows a log normal statistical distribution. Then, based on this feature, it is explained why the mean values from the linear data are different from the mean values (or median values) calculated from the log noise data. Finally, the consequence of this finding in terms of LFN characterisation issues and Monte Carlo LFN variability circuit simulation is discussed.

Finite-impulse-response (FIR) lowpass second-degree differentiators (with coefficients that are based on an optimal design approach) are presented. By minimising the filter variance, the differentiator rejects noise above the cut-off frequency, with steep roll-off in the transition-band, and showing close-to-ideal magnitude response accuracy in the passband. The proposed FIR differentiators are used to estimate the principal frequency of a non-ideal power system, based on a variant of Sarkar and Sengupta's algorithm. Use of an FIR filter, rather than an infinite-impulse-response (IIR) filter, for fundamental frequency estimation is shown to improve the accuracy of frequency estimation.

Wireless local area network (WLAN) devices emitting in the 2.4 GHz band may raise questions concerning human exposure mainly when a person stands near an antenna. Proximity far-field level variation with distance, in the range 40 cm to 1 m is investigated experimentally in order to extract peculiarities of the radiated field in comparison with theoretical predictions. Electric field strength depends on the method of measurement (not yet standardised for quasi-stochastic signals) and on some key characteristics of transmission. The field level proved to differ from theory: it is lower than predicted and it does not always follow the inverse law with distance. The time–amplitude and the duty-cycle methods of weighting to obtain a realistic field level allowed highlighting the dependence of the field strength on the traffic direction, on the type of the transmitted file and on the actual data rate and its statistical distribution. In the proximity of access points, downloading conducts to the highest fields, whereas near laptops, uploading does this. A data file transfer implies a higher level of exposure than a video file transfer, but one should consider the data rate dispersion. The proximity field does not significantly depend on the distances between the WLAN devices.

Accommodating an increasing number of machine-to-machine (M2M) devices is one of the main issues faced by the cellular networks. In a typical M2M setup, several devices may try to connect to the network simultaneously. Long-term evolution advanced (LTE-A) networks use a random access procedure for this purpose, which is not sufficient to cater for a large number of devices. The conventional procedure is extended by allowing several devices to access the network with reduced collisions. Mathematical analysis and simulation results show that the proposed scheme increases the access probability as well as the number of successful transmissions.

Recently, the present authors proposed to combine time sharing with hierarchical modulation to increase the transmission rate of broadcast systems. The proposal involves grouping the receivers in pairs in order to transmit with hierarchical modulation. Several grouping strategies were introduced but the optimal matching remained an open question. In this reported work, it is shown that the optimal grouping is the solution of an assignment problem, for which efficient algorithms exist such as the Hungarian method. Based on this algorithm, the performance of the optimal grouping in terms of spectrum efficiency for a digital video broadcasting – satellite – second generation (DVB-S2) system is studied.