A low-profile substrate integrated waveguide (SIW) cavity antenna with enhanced bandwidth is proposed. Three slots are etched to divide a single cavity into multiple sub-cavities. Four fraction modes including a half mode, a quarter mode and two-eighth modes are excited by a capacitively coupled feeding. Bandwidth enhancement can be achieved when these fraction modes have close frequencies and couple with each other. A fabricated prototype centred at 3.55 GHz has been measured. With the size of 0.43λ₀ × 0.43λ₀ × 0.04λ₀, the proposed design achieves the bandwidth of 13.5% and an efficiency of 85%. The proposed antenna has advantages of low profile, enhanced bandwidth and high efficiency, which is a good candidate for the fifth generation wireless systems.

In this Letter, a circularly polarised (CP) antenna is proposed. The proposed antenna is realised by combining two angled C-shaped structures. By setting different widths (W _L and W _R) for the left and right angled C-shaped structures, respectively, an asymmetric structure is obtained. Therefore, the proposed antenna exhibits CP characteristics. From repeated simulation results, the authors find that the optimum ratio W _L: W _R to make the proposed structure operate as a CP antenna is 5: 8. Moreover, the measured reflection coefficient is lower than −2.4 dB within a stopband up to 12 GHz. This means that wide harmonics suppression (up to the fifth harmonic) is successfully achieved.

In this Letter, a dual-band antenna with an improved gain is proposed. The structure features 9.7 and 10.4 dBi gain within 2.4 GHz to 2.5 GHz and 5 GHz to 6 GHz bands, respectively. This makes it suitable for WLAN and ISM applications. The structure comprises an asymmetrical pair of radiators and slots suspended over a reflector. The antenna is optimised in a two-stage process using a trust-region-based gradient search algorithm. The design is compared to the state-of-the-art radiators reported in the literature. The numerical results are validated through measurements of the fabricated antenna prototype.

This Letter presents the development of a dual linearly polarised microstrip antenna for S- and C-band with improved isolation and bandwidth. The antenna is dual linearly polarised at each of the bands. The S-band patch is proximity coupled to two orthogonal feed lines, whereas the C-band patches are aperture coupled to other two mutually orthogonal feed lines. The antenna results in an impedance bandwidth ≥ 3.65% with an isolation ≥ 26 dB at the S-band ports. At the C-band ports, it also displays an isolation ≥ 45 dB over the entire operating bandwidth of ≥ 21%. All these results are improved compared to the earlier reported investigations.

A design of partially reflective surface (PRS) for Fabry–Perot resonator antenna to simultaneously achieve axial ratio bandwidth and broadside-gain enhancement is demonstrated. A simple wideband stacked patch antenna that operates at X-band (8–12 GHz) is used as a radiation source to demonstrate the performance of this design. The proposed antenna has a PRS array comprising of 11 × 11 unit cells tapered which features 16.9 dBi maximum broadside gain and 12.7% common bandwidth from 8.8 to 10.0 GHz.

In this Letter, the authors report on the design, optimisation and electrical measurements of a new fully integrated multiplexing selector fabricated in 0.7-µm indium phosphide (InP) double-heterojunction bipolar transistor technology. All parts of the circuit were optimised to obtain 200-Gbit/s class of operation. They present electrical performances at 140 and to a record speed of 212 Gbit/s, highlighting their respective measurement challenges. The power consumption of the circuit is 0.5 and 0.8 W for a differential output amplitude of 240 and 730 mV, respectively. This selector has been successfully used as modulator driver in optical transmission experiments up to 204 Gbit/s.

Clock is regarded as the heartbeat of modern synchronous digital integrated circuits. However, with the CMOS technology shrinking, it becomes critical to deliver high-quality global clock signal with low propagation delay and hence conventional metallic interconnect seems to meet its bottleneck, as a clock distribution network (CDN) might consume up to 50% of the overall power. To address these problems, this Letter proposes a novel combination of wireless and conventional metallic interconnect to improve the performance of on-chip clock distribution. By incorporating integrated wireless clock transceivers and efficient modulation technique, overall performance has been increased significantly with a total delay reduction of 66.8% compared with a new cornerstone tapered H-tree model from 400 to 130 ps. In addition, clock uncertainties are now predictable according to the displacement of transceivers, 33 ps of clock skew at 2.5 GHz input with highly unbalanced loads could be found within the proposed CDN, and hence, indicates a promising potential of future high-performance on-chip clock distribution.

In this Letter, a novel convolutional neural network (CNN) attack is explored as a new kind of malicious attack to disclose the secret key of cryptographic circuits. A cryptographic circuit with the known secret key is set as the reference model for training the CNNs. Moreover, a matrix that includes the information of an input plaintext and the known secret key of the cryptographic circuit is built as the input training data of the CNNs. A Sigmoid function and a step function are used to normalise and classify the power dissipation of the cryptographic circuit to generate the output training data of the CNNs, respectively. After training the CNNs, a cryptographic circuit with the unknown secret key can be cracked by hypothesising all the possible keys to test the well-trained CNNs, because the correct secret key enables the CNNs to achieve the highest testing accuracy among all the hypothesised keys. As demonstrated in the results, the proposed CNN attack successfully reveals the secret key of a unprotected (protected) cryptographic circuit after analysing about 500 (100,000) data.

Wireline communication circuits often include serialisers/deserialisers using multiphase signals for multiplexing or sampling. From a power efficiency viewpoint, configurations are desired in which a single differential clock at frequency f is distributed to decentralised multiphase generators as opposed to distribution at 2f with local frequency dividers. A bang–bang phase detector (BBPD) is presented for such a multiphase generator operated from 4 to 16 GHz. Owing to the 2-octave frequency range, a wide input phase range is required for which the BBPD may not generate false locks. This is achieved by an implementation in which down pulses at the output of a fully symmetrical set/reset latch are stretched via pulse-width extension circuitries. A sampling pulse generated from one of the input phases can then easily capture the extended down pulses across a wide input phase range to unambiguously indicate phase leading or phase lagging to the control logic of the multiphase generator. The proposed circuitry has been implemented in a 7 nm CMOS technology. A comparison to alternative BBPD approaches implemented in the same technology shows that the proposed architecture outperforms them in terms of achievable input phase range.

A voltage controlled oscillator (VCO) applied to phase-locked loop with multi-node coupling triple mode redundancy is proposed in this Letter. The proposed VCO consists of three independent operating VCOs. These VCOs are coupled through a metal oxide metal capacitor to synchronise the output of the three independent VCOs. The proposed VCO does not introduce loop delay, and the frequency and phase noise do not decline.

This work details manufacturing processes developed to integrate an unpackaged silicon die onto a paper substrate, as part of constructing a hybrid inkjet-printed paper-based circuit. This integration between rigid components and flexible substrates is beneficial in low-cost applications and capitalises on the advantages of both the well-established integrated circuit technology and the emerging paper-based electronics platforms. A superglue incline at the chip edge formed a ramp for printing the silver interconnects between the paper-based circuit and the chip pads. Two printing protocols are compared, the first a single layer using 5 μm drop spacing, and the second using a 35 μm drop spacing for three layers. An unpackaged RFID tag die is successfully integrated and is presented as proof of concept.

An unusual behaviour of a ring oscillator (RO) is described, namely the RF interference in the supply can lock the operational frequency of the RO. The lock is not an oscillator-level lock, but a gate-level lock. Transistor-level simulations are performed on various technologies. The locking phenomenon appears in all simulated cases and follows certain rules. Moreover, the model is also verified with an RO test board. In contrast to traditional injection locking, where the injection is applied to the signal pin of the oscillator, the locking behaviour introduced is caused by the injection in the supply. To the best of knowledge, this type of locking phenomenon has been reported and demonstrated for the first time.

Male-based factors have very critical effects in infertility. The determination of male factors is based on the semen analysis performed by multiple aspects such as motility, morphological and concentration. Normally, tests are applied by experts manually. Therefore, the results are highly subjective. Automation of analysis minimises the human factor. In this respect, a number of studies on the computerised semen analysis have been recently reported. One of the most important steps in computerised approaches is the region of interest extraction. In this Letter, a novel masking technique is introduced with the aim of better region of interest extraction, in which each sperm is individually analysed by head and tail specified stages. In this approach, wavelet-based image enhancement techniques and gradient analysis are jointly utilised for finding the sperm orientation. Later, elliptic masks are employed for the sperm segmentation along this orientation. As the evaluation methods, firstly proposed technique's segmentation performance is assessed by visual inspection. Secondly, the k-nearest neighbours (k-NN) classification results of proposed approach's outputs are compared with the outputs of classical k-means segmentation and also the raw images. Results indicate that 93.5% of all the sperms are correctly segmented by proposed masking approach and up to 13% increase is observed in k-NN classification.

The bilateral filter is a fundamental smoothing tool in image processing and computer vision due to its outstanding edge-preserving ability. However, the computational complexity depends on the size of the support of the spatial kernel. This drawback makes bilateral filtering time-consuming and significantly limits its applications. A novel strategy to turn the range kernel of the bilateral filter into a sum of exponential functions is proposed. As the convolution with the exponential function can be accelerated by the box filtering, the computational complexity of the bilateral thus becomes . Experimental results disclose that the proposed algorithm is competitive with the state-of-the-art algorithms in terms of filtering accuracy and computational efficiency.

A new method is developed to deblur seriously blurred images taken in a long exposure of camera in the fast motion. It is different from most of the existing deblurring methods that result in a poor quality for processing serious blur images, and few papers concerned the deblurred image quality, the authors study referenceless image quality assessment method to deblurring image. A blurred image is modelled based on a fast motion scene. Due to the consistent characteristics of direction motion blurs and ringing artefacts generated with the direct deconvolution, an adjacent-column-greyscale-difference index is proposed, which combines with an effective spatial quality evaluator to reduce the artefacts and improve quality of the deconvolution image. The process of the proposed method is automatic and fast in the image deblurring, it is verified on both the synthetic-blurred and the real-scene-blurred images, which outperforms the existing methods in reducing serious blurs of forward motion images.

This Letter first proposes an algorithm for compressing the sets of the similar images with priorities. The proposed algorithm includes four modules, i.e. priority assigned, depth- and priority-constrained minimum arborescence generation, disparity reduction, and residue coding. Experimental results demonstrate that the proposed algorithm can effectively compress the similar images with priorities, and achieves similar rate-distortion performance to the state-of-the-art image set compression algorithm which has no constraints of depth and priority.

Several recent deep network architectures tried to handle the depth estimation process as an image reconstruction problem, in order to overcome the shortfall that the ground truth depth data is not sufficiently available. The authors introduce and validate an efficient deeper network architecture for unsupervised depth estimation with an automated parameter optimisation. In addition, a hybrid appearance loss function is also proposed to improve the depth estimation accuracy and effectiveness. The authors' proposed model achieves the advantage that individual element of the loss function is weighted using normal distribution characteristics of a Gaussian model. The proposed ideas are validated on KITTI dataset achieving best reported results among recent state-of-the-art methods.

This Letter introduces a class of fixed-length to variable-length balanced binary line codes. By considering fixed size blocks of source digits, a balanced line code is constructed by appending a minimum number of 0's or 1's to each such block in order to produce words having equal number of 0's and 1's, i.e. balanced words of variable length. By taking into account the design constraint of being easily implementable in practice, the construction introduced achieves high coding efficiency and is at least asymptotically optimal in terms of redundancy.

Generalised space shift keying (GSSK) technique proposed for massive multi-input–multi-output systems has a higher information transmission rate due to the activation of multiple antennas at the same time, and also has significant advantage in terms of hardware cost. However, the maximum likelihood detector has a very high complexity which makes it computationally intractable for large-scale GSSK systems. In this Letter, a sparse detector is proposed by exploiting the inherent property of sparsity in GSSK. Different from the existing compressed sensing (CS)-based detectors, the proposed detector utilises Euclidean distance instead of inner product operation for antenna matching. Moreover, it can remove erroneous antenna indices by backtracking to promote the detection performance. The simulation results show that the proposed scheme outperforms the existing CS-based detectors while maintaining low complexity.

Error correction performance of finite-length polar codes has been a major concern in the past decade. This Letter presents a method for improving the error correction performance of cyclic redundancy check (CRC)-aided successive cancellation list decoding for polar codes of medium block-lengths with high code rates. In the proposed decoding scheme, a one-time repetition of least reliable bit-channels along with partial protection of the message is employed to correct the error(s) when decoding fails. The results show an improvement of nearly 0.2 dB in error correction performance.

In this Letter, a miniaturised tri-band lowpass–bandpass (LP-BP) filter is proposed by using lumped-element structure. The lowpass passband (LP) and the first bandpass passband (1-BP) are produced by using the transmission zeros to divide a lowpass filtering response into a dual-band LP-BP filtering response. The second bandpass passband (2-BP) is produced by further loading a lumped-element circuit. As an example, an LP with 3 dB cut-off frequency of 1 GHz, and two BPs centred at 2.45/5.2 GHz for the WLAN applications are designed. The fabricated tri-band LP-BP filter has low passband insertion losses of 0.08/0.69/1.38 dB, and occupies a compact circuit area of 0.055λ _gc × 0.063λ _gc.

Visible-light communications (VLCs) are emerging as a valid alternative to radio-frequency systems for the provision of Internet connectivity to aircraft passengers through the LED reading lamps. In this Letter, the authors investigate the minimum required level of emitted flux in order to support the communication with the users' terminals. A VLC system employing 1 lm of flux is able to achieve an average per-user capacity comparable with the one currently in use for 4G (6 bit/s/Hz) over an electrical bandwidth of 10 MHz, which is sufficient to support the latest multimedia services (40 Mb/s for Blu-ray video streaming).

The authors demonstrate distributed temperature sensing based on slope-assisted Brillouin optical correlation-domain reflectometry (BOCDR) with a long measurement range of >10 km. They find that to achieve such a long-range measurement, a delay line in a reference path needs to be at least four times longer than the sensing fibre. In addition, they show that the use of such a long delay line induces forward-propagating Brillouin-scattered light in the reference path, which deteriorates the signal-to-noise ratio (SNR) of the system and should be suppressed. Finally, by exploiting a beyond-nominal-resolution effect of the slope-assisted BOCDR, they detect a 3-m-long heated section in a 13-km-long silica fibre in a distributed manner; the reason for its low SNR is also discussed.

The authors report a one-piece flexible liquid level optical fibre sensing probe in this Letter, which is meant to measure the liquid level inside the cryogenic propellant tanks of spacecraft and rockets. The ultra-lightweight sensing probe can be used in both aerospace vehicles and in any type of cryogenic fluid storage system. In contrast to current liquid gauging technologies such as Delta-P pressure sensor, capacitance probe, ultrasonic sensor, and silicon diode liquid level sensing probe, the fibre optic continuous liquid level sensor has unique advantages in terms of gauging accuracy, reliability, simplicity, and maintenance. The sensor uses one single optical fibre probe to measure the liquid level and the liquid distribution of cryogenic propellant. Every point of the sensing fibre is a ‘point sensor’ that is able to distinguish liquid and vapour. The physical location of each ‘point sensor’ can be determined with 1 mm spatial resolution or better. The optical fibre probe can be installed in a propellant tank with the same manner as currently used silicon diode liquid level sensing probe via only one single feed-through to connect to an optical signal interrogation unit located outside the tank. Experiments on measuring liquid nitrogen level are demonstrated.

Binary offset carrier (BOC) signals are applied in modernised global navigation satellite system. High-order BOC signals provide good performance in spectrum separation and signal tracking. However, for high-order BOC signals, the sampling frequency is much higher than that of binary phase-shift keying signals, which increases computational complexity. Meanwhile, the zero crossings in the correlation function degrade the detection performance. In this Letter, band-pass sampling is introduced for BOC signals to reduce the computational complexity and remove the zero crossings. A delayed replica of the received signal is used to construct a complex signal which is sampled with a much lower sampling frequency than the Nyquist frequency. The correlation function of the sampled signal has no secondary peaks. Thus, the detection probability is higher and the computational complexity is lower.

A high-performance normally off recess-gated aluminium gallium nitride (AlGaN)/GaN metal–insulator–semiconductor field-effect transistor (MISFET) is successfully demonstrated with operation temperature of 200°C which was fabricated by using a self-terminating gate recess etching technique. At 200°C, by employing a high-quality aluminium oxide/silicon nitride bilayer as gate dielectrics, the fabricated device exhibits a high threshold voltage of 4.5 V, a high drain current density of 321 mA/mm, a low off-state leakage current of 20 μA/mm as well as a high on/off current ratio of ∼10⁶. Furthermore, a high forward gate breakdown voltage of 23.6 V (∼7.9 MV/cm) and an off-state breakdown voltage as high as 1055 V are obtained in the fabricated device, both of which, as far as it is known, is the highest reported value in normally off GaN devices operated at 200°C. The high threshold voltage, large drain current density, low off-state leakage current, high gate breakdown voltage as well as high off-state breakdown voltage make this normally off recess-gated AlGaN/GaN MISFET very suitable for high-temperature power switch applications.

This Letter presents capacity analysis of Fisher–Snedecor F fading channels under different transmission strategies. To this end, novel analytical expressions are proposed for optimal rate adaptation with constant transmit power, channel inversion with a fixed rate and truncated channel inversion with fixed rate schemes in this Letter. Then, analytical results are illustrated for different fading and shadowing parameter values.

In this Letter, the authors study analytical performance of various soft data fusion (SDF) schemes over generalised fading channels in a cognitive radio network. Two generalised fading models, namely, and are considered individually in the sensing channels and various SDF techniques are implemented at the fusion centre. Novel analytical frameworks for cooperative detection probability are developed subject to SDF and generalised fading and validated through computer simulations. Optimal values of the detection thresholds are determined where an average error rate is minimum.

This Letter proposes a new symbol detection scheme for an uplink wide-banded cyclic prefixed filter bank multiple access system. The feature of the proposed scheme is that it eliminates the analysis filter bank processing that is commonly employed in the existing schemes. By leveraging a particular interleaving structure, the large matrix inversion operation is decomposed into parallel matrices inversions with small sizes. The benefits of the proposed scheme include lower complexity and higher spectral efficiency. In addition, the detection performance is also improved, which is verified by simulations.

An estimator of the spatial correlation coefficient for frequency selective time invariant MIMO channels is proposed. Numerical results show that the proposed SCC estimator performs better than the widely used classic SCC estimator. Based on numerical simulations, the trade-off between the maximum tolerable mean-squared error of the proposed SCC estimator and the measurement bandwidth is shown.