A novel dual-band compact patch wireless fidelity (Wi-Fi) antenna using μ-negative (MNG) transmission lines (TLs) for the smart helmet is presented. In the smart helmet scenario, rescue agent is able to communicate with the other rescue agents, control centre, and drones via the helmet by Wi-Fi dual bands. For the smart helmet communication, the antenna, which consists of two MNG-TL loops located on the outside and inside, is devised. The dual-band corresponds to the zeroth-order resonance (ZOR) and second-positive-order resonance (SPOR) of the outer MNG-TL. The ZOR frequency of the outer MNG-TL is near the Wi-Fi 2.4 GHz band, and the SPOR frequency of the outer MNG-TL, excited by the coupling between the inner and outer MNG-TL loops, is the Wi-Fi 5 GHz band. The prototype of the proposed antenna has been fabricated and measured. The bandwidth of the antenna includes Wi-Fi 2.4 and 5 GHz bands with high radiation efficiencies of >49% and a compact size of 27.6 mm × 27.6 mm × 1.27 mm (1/4.5λ × 1/4.5λ × 1/98.4λ at the lowest operating frequency).

A dual-sleeve wideband monopole antenna with loaded plasma cylinders is proposed for shipborne systems in lower very high frequency (VHF) range. The monopole with sleeves, engineered as vertical polarised element, operates at the frequency from 30 to 100 MHz. It performs good radiation ability with low elevation angle in E-plane. The monopole antenna height over feed point is 0.33λ at the lowest band. Plasma cylinder array as reflector is mounted above the monopole to restrain the deformation of patterns. Impedance and pattern measurements are conducted; the VSWR ≤ 2:1 bandwidth of the sleeve antenna is >107%. Unmanned aerial vehicle system is introduced to measure the radiation patterns at 110 MHz. Obtained results confirm that the proposed antenna is a variable candidate for communications with ships and flying vehicles in anti-stealth systems.

A compact dual-circular polarised metamaterial inspired antenna is proposed for nanosatellite payload communication. The antenna consists of two-layered stacked structure with a sandwich rectangular parasitic layer between two layers. Two double negative metamaterial cells. Two unit cells of DNG metamaterial structure are applied inside the pentagonal radiator to enhance 3 dB axial ratio (AR) bandwidth and beamwidth. Two orthogonal feedings are utilised to generate dual-circular polarisation (CP). The antenna achieves measured 710 MHz (3.06–3.77 GHz) of −10 dB impedance bandwidth with 160 MHz (3.02–3.18 GHz) and 210 MHz (3.05–3.26 GHz) of 3 dB AR bandwidth for port 1 and port 2, respectively. The 3 dB AR beamwidth of 165° for port 1 and 212° for port 2 is exhibited with an average realised gain of 5.15 dB. A 1U nanosatellite structure has been utilised to realise the antenna performance while operation in real-time environment.

A bulk-linearised composite MOSFET is presented, with an extended linear range and an equivalent saturation voltage of up to several hundred mV even in weak inversion. Some preliminary measurements are presented as well as a 300 MΩ equivalent resistor, with almost a 1 V quasi-linear range. A low frequency, 28 dB gain, biomedical bandpass filter/amplifier is also shown, taking advantage of the linearised MOSFETs to consume only 16 nA of supply current.

A trench insulated gate bipolar transistor (TIGBT) with emitter-embedded gate is proposed. The emitter-embedded gate could increase the gate-to-emitter capacitance C _GE without affecting the miller capacitance C _GC. Therefore, the ratio of C _GC to C _GE is significantly reduced, which suppresses the gate self-charging effect effectively. As a result, an excellent controllability on the turn-on dI _CE/dt of the TIGBT and the dV _KA/dt of the free-wheeling diode (FWD) is obtained. The simulation results based on a 1.2 kV TIGBT show that, in comparison with the conventional TIGBT, the lower limit of the reverse-recovery dV _KA/dt of the FWD can be reduced by 91.2% and the turn-on loss could be reduced by 53.1% under the same dV _KA/dt.

Recently, centre loss that aiming to assist Softmax loss with the objectives of both inter-class dispension and intra-class compactness simultaneously, has achieved remarkable performance on convolutional neural network-based face recognition. However, its advantages highly rely on the centre feature assumption, which influences the capacity of the final obtained face features. Inspired by the centre loss approach, a novel Orientation Truncated Centre Learning is proposed, which takes advantage of an orientation truncated centre function to make the centre feature learning have more suitable orientation for deep face recognition. Three metrics are proposed to evaluate how discriminative are the distributions of the learned features for MNIST visualisation. Experimental results on several challenging benchmarks, including fine-grained labelled faces in the wild (FGLFW), labelled faces in the wild (LFW), YouTube faces (YTF), and benchmark of large-scale unconstrained face recognition (BLUFR), show that the proposed approach can easily generate more favourable results than several state-of-the-art competitors.

Belief propagation and variants are the usual decoding algorithms for low-density parity check codes. The successive overrelaxations are applied to increase the convergence speed of the decoding process. Performances are reported and improvements over the reference algorithms are observed. This technique is also compatible with the high-speed parallel group decoding involved in modern standards such as DVB-S2.

A deep learning (DL)-assisted and combined side-channel attack (SCA) is exploited to disclose the secret key of an advanced encryption standard (AES) cryptographic circuit with a countermeasure. Different physical leakages of the protected AES cryptographic circuit such as power dissipation and electromagnetic (EM) emission are captured together at first. Then the deep neural networks are utilised to model the relationship between the power noise and the EM noise by analysing the captured power dissipation and EM emission profiles. Ultimately, a special power attack is performed on the protected AES cryptographic circuit to leak the secret key efficiently through using the EM noise to filter the power noise. As demonstrated in the results, for the conventional SCAs, the secret key of the protected AES cryptographic circuit is undisclosed to the adversary even if 1 million plaintexts are enabled. By contrast, only analysing 32,500 number of plaintexts are sufficient to leak the secret key if the DL-assisted and combined SCA is executed.

Recent sampling results show that ideal piecewise polynomials can be modelled as finite-rate-of-innovation (FRI) signals and perfectly recovered by spectral estimation. However, there is no any generic FRI model for non-ideal piecewise polynomials. An FRI model is proposed as an extension of the VPW-FRI (pulses with variable width) model for non-ideal piecewise polynomials which have uncertain transition zones near discontinuity points. The derivative of non-ideal piecewise polynomials as differentiated VPW pulse streams is assumed. The proposed model can be sampled by arbitrary kernels and recovered by a modified annihilating filter. For the extended model, simulation results analyse several factors that affect the model anti-noise property and verify its superiority of better matching performance for real non-ideal signals in comparison of the FRI model for ideal piecewise polynomials.

A novel position-aided fast millimetre-wave beam training using compressive sensing (PAF-CS) is proposed. In particular, the position information is used to obtain the angle-of-arrival, and this operation can facilitate beam alignment with significantly reduced system overhead. Aiming to resolve the position uncertainty, the PAF-CS method first identifies a critical area by using the statistical information of the position error, and finds the best beams by using CS method. Theoretical analysis and simulation validate the superiority of the PAF-CS method.

An improved extension method based on protograph extrinsic information transfer (PEXIT) charts is proposed to design rate-compatible quasi-cyclic low-density parity-check (QC-LDPC) codes with more flexible rates and better performance. The masking matrix of the highest-rate code can first be constructed column by column to own the lowest decoding threshold. Then, an extension algorithm is proposed to obtain the masking matrices of lower-rate codes with flexible rates. Finally, the base matrices with small amount of short cycles are designed and the parity-check matrices of rate-compatible QC-LDPC codes are obtained through matrix extension. Simulations show that compared with the existing codes, the proposed codes have more flexible rates while achieving better performance.

This Letter introduces a CMOS depth sensor with a multi-resolution single-photon avalanche diode (SPAD) array and area-efficient filter circuit with a programmable reference for environment-adaptive noise suppression. Four SPADs compose a macro-pixel for detecting targets at a short distance with high resolution, whereas 4 × 4 SPADs are reconfigured to a super-pixel for a long distance with enhanced signal-to-noise ratio. To provide environment-adaptive noise suppression in the miniaturised SPAD array, an area-efficient filter circuit with a programmable reference is proposed: a digital macro-filter corresponding to a macro-pixel and an analogue super filter corresponding to a super-pixel. The prototype chip was fabricated with a 110 nm CMOS image-sensor process, including 128 SPAD farm arrays and 128 analogue front-end circuits. With high background light of over 90 klx and a high dark-count rate of over 27.1 kHz, the time-of-flight could be measured by filtering out invalid pulses from noise without using multiple time-to-digital converters per pixel, which enables the implementation of miniaturised LiDAR-sensor systems on a chip.

A novel quarter-guided-wavelength (1/4λ) dielectric-strip resonator (DSR) with one short-circuited end is proposed to design a compact and low-loss filter at X-band. One end of the DSR is metallised and then shorted to ground effectively to achieve a half-cut conversion from 1/2λ DSR. As a result, the resonator length is reduced by half while the unloaded quality factor (Q _u) of the 1/4λ DSR only has a slight reduction as compared to the corresponding 1/2λ DSR. For demonstration, a third-order DSR bandpass filter centred at 10.45 GHz is designed, implemented and measured. Good agreement between simulated and measured results can be obtained, showcasing the advantages of compact size and low loss.

A tri-band bandpass filter design by using conventional stub loaded step impedance resonator (SLSIR) is presented. The proposed SLSIR consists of three tri-loaded open-circuited stubs parallel attached to a short and open-circuited stub. A tri-band bandpass filter is designed using two proposed symmetrical SLSIR's separated by a short-circuited stub. In this configuration, the filter produces three bands of frequencies at 0.9, 2.4 and 5.5 GHz, respectively. It is shown that the resonating frequencies can be independently controlled by loaded stubs. For better out of band rejection and increased selectivity, four finite frequency transmission zeros around three passband edges are achieved. The obtained fractional bandwidths are 23, 10 and 17% centred at 0.9, 2.4 and 5.5 GHz, respectively. The proposed design topology is fabricated on a substrate RT/Duroid 5880. The simulated and measured results show good accordance. The fabricated prototype has a compact size of at 0.9 GHz.

A novel X-band low phase noise oscillator is proposed by taking advantage of the enhanced quality factor of air-filled substrate integrated waveguide (AFSIW) resonators. A pair of AFSIW resonators is embedded in a feedback loop, which forms a high-selectivity bandpass filter, to greatly reduce the phase noise of a heterojunction FET oscillator. A prototype is designed, fabricated and measured. At an output signal of 9.85 GHz, the phase noise is −146.8 dBc/Hz and the figure of merit is −210.6 dBc/Hz at 1 MHz offset frequency. An improvement of about 10 dB in phase noise performance is obtained compared with published substrate integrated waveguide resonator-based oscillators.

A quad-band Gysel power divider based on the coupled-line network is proposed. The closed-form equations are derived to solve even- and odd-mode impedances of the coupled lines. For illustration, a prototype operating at 0.6, 1.41, 2.14 and 2.95 GHz is designed and fabricated. The measured results show a good agreement with the simulated ones.

Substrate-integrated waveguide triple-band bandpass filter composed of two dual-mode (TE₁₀₁ and TE₂₀₁) rectangular cavities coupled with two single-mode (TE₁₀₁) ones is synthesised and designed based on dual-mode resonances and split-type dual-band symmetrical frequency response. By applying the dual-mode frequency and coupling controlling techniques, the centre frequencies and fractional bandwidths (FBWs) of the three passbands can be allocated more flexibly. An experimental prototype centred at 11.578, 12.468 and 14.985 GHz with respective FBWs of 2.21, 2.21 and 2.3% is synthesised, designed, fabricated and measured for demonstration, showing good agreement between the measured and simulation results.

Literature survey shows that the modal chart for first 13 modes of cylindrical dielectric waveguide (CDWG) is incomplete. It is found that the 12th mode, i.e. mode has been missed out which exists between and modes. CDWG is reinvestigated here theoretically and the complete modal chart for first 15 modes is given here.

We report a high-power optically-pumped vertical-external-cavity surface-emitting laser emitting at around 1180 nm. The free-running laser produced 72 W of output power at a heatsink temperature of 0°C and 53 W near room temperature (20°C). The GaAs-based gain mirror was bonded to a 2-mm-thick diamond attached to a TEC-cooled copper mount in order to enable efficient heat extraction for high-power operation. Moreover, the spectrum of the laser was narrowed down to 0.06 nm by employing a combination of a birefringent filter and an etalon inside the cavity which yielded a maximum of 19 W at a heatsink temperature of 20°C. The demonstration opens a new perspective for the realisation of sodium laser guide star adaptive optics employing frequency doubling of 1180 nm radiation.

Dual active bridge is a promising bidirectional topology characterised by its versatility and operation. Power calculation is based on the average current flowing through the load. Therefore, power calculation becomes rigorous task as separate computation is needed for each mode. To mitigate the complexity of the power computation, a novel unified harmonic based power calculation has been proposed.

The target localisation problem is considered using the bistatic range measurement in multistatic passive radar. The well-known two-step weighted least-squares algorithm is widely used to locate a single target, in which the nuisance variables are normally introduced in the first step. Whereas the nuisance variables can be categorised as either target–transmitter ranges based or target–receiver ranges based. The influence of nuisance variables selection on target positioning accuracy is investigated in this Letter. Some basic criteria on choosing nuisance variables are presented and validated through simulations.

Low-cost, low-power wireless sensor nodes that operate in Cauchy noise are required for applications that are located near highly trafficked roads, highways, and bridges, where solar or other green power operation is desirable. A novel suboptimal Cauchy detector of notable simplicity, suitable for low-power sensor nodes, is proposed. The novel suboptimal detector approaches the performance of the optimal detector very closely while surpassing the performance of popular previously published suboptimal Cauchy detectors by 1–4 dB.