A frequency and polarisation reconfigurable printed monopole antenna using switching PIN diodes is presented. This antenna is made up of a printed monopole, two switching circuits and a reflector. By controlling the on-off states of these two switching circuits on the finite ground plane, a frequency and polarisation reconfigurable antenna is achieved. To verify this design, this antenna is fabricated and measured. The measured results show that this antenna has four states. These states are: state 1, 2.02–2.56 GHz (23.6%); state 2, 2.32–2.95 GHz (23.9%); state 3, 1.92–2.70 GHz (33.8%); state 4, 1.88–2.67 GHz (34.7%). In states 1 and 2, this antenna radiates linearly polarised wave as a traditional printed monopole. In states 3 and 4, this antenna radiates left-hand circularly polarised wave and right-hand circularly polarised wave, respectively.

Two ground radiation antennas with polarisation diversity performance were proposed for MIMO WLAN applications in wearable devices. The antennas can simultaneously excite the vertical mode and horizontal mode of the ground plane and the phase difference between the two modes can be controlled by utilising an inductor-loaded metal strip in the ground plane, generating circular polarisation. A 3:1 VSWR bandwidth of 140 MHz with high isolation (above 17 dB) and a 3 dB axial ratio bandwidth of 100 MHz was obtained. The opposite rotations generated by the two antennas resulted in good diversity performance, which was verified by the measured envelope correlation coefficient.

Based on capacity maximisation metric, an iterative swapping antenna selection method is proposed for massive multiple-input multiple-output (MIMO). Then a ‘local’ swapping algorithm is proposed for massive MIMO antenna selection, which swaps the target antennas ‘locally’. A ‘global’ swapping algorithm is also proposed to reduce the computational complexity, which exchanges the target antennas ‘globally’. Both of the proposed algorithms are near optimal, due to the consideration of the influences of the unselected antennas and the selected ones on the antenna to be selected. Last, numerical simulations are provided to validate the proposed algorithms.

Discretised liquid metal is actuated in a 2 × 2 pixel grid to demonstrate pixelated reconfiguration. Within each pixel, continuous electro-wetting actuates liquid metal from a lower to an upper reservoir, allowing that pixel to either appear or disappear without employing switches between adjacent pixels. Liquid metal is actuated within 0.3 s and is reversible.

Lung cancer is an insidious disease, producing no symptoms until the disease spreads widely in the human body. Mutations of genes are the first alarm of such a disease in the human body. Therefore, classifying these mutations could provide guidance for the treatment decisions for lung cancer. In this Letter, a novel accumulated grey-level image (AGLI) method for gene representation is introduced, where each base in gene sequence is represented by accumulated number based on its order in gene sequence and then reflected into image domain. AGLI is incorporated with 2D principle component analysis to build accurate and low-dimensional algorithm for classifying the genetic mutations. Proposed algorithm was applied on the top 10 effective genes in lung cancer, where an accuracy of 99.27% was achieved. Experimental results show that the proposed algorithm enhanced the accuracy of classification and reduced the classification time for mutation in lung cancer relative to the existing methods.

We propose confocal laser feedback microscopy for in-depth imaging of highly scattering samples. This technique provides a compact configuration for microscopy in reflectance mode; it is based on laser feedback interferometry which is a sensing technique where the laser acts as both transmitter and receiver of the beam. Operating at 850 nm, it offers an ideal platform for non-invasive and in vivo imaging of soft biological tissues. To explore the technique, the authors performed microscopic imaging of micro-glass-spheres (with diameter sizes of 10–20 µm) deep within an agar gel sample, at depth of 0.43 mm from the surface. Experimental results show the feasibility of a compact, low-cost, and simple laser-scanning microscope with possible biomedical imaging applications.

A compact low-supply-voltage yet low-noise digital bang–bang PLL (DBBPLL) is proposed. The bang–bang phase detector is based on a dynamic double-tail latch which enables high time-to-voltage gain and low input-referred noise under tight power-supply headroom. The ring-based digitally controlled oscillator (DCO) is made of multiple g _m-controlled delay units and a constant-g _m-biased current DAC. By combining these two blocks, the DCO can now better tolerate supply noise and process variations. A prototype DBBPLL has been implemented in a mainstream 28 nm CMOS process with a compact die area of 0.014 mm². When operating at 2.6 GHz, it consumes 2.9 mW with 0.75 V supply and achieves low in-band phase noise of −105 dBc/Hz.

Flip-flop based phase-frequency detectors are widely used in phase-locked loop circuits. These devices are usually assumed to behave linearly although they consist of non-linear parts. In this work, a flip-flop based phase-frequency detector circuit is analysed. Analytic output signal models are derived for arbitrary input signal frequencies and phases. Exact and approximate closed-form solutions are found for different frequency ratios. The model is validated by numerical time-domain simulations.

This Letter proposes a modified method for the dynamic harmonic analysis of signals with non-stationary harmonics, which is based on the previously proposed multiple-resonator observer structure. An optimisation technique is applied to reshape frequency responses of the basic transfer functions. This method, by using a parallel structure with common feedback, is very robust and, in addition, allows a reduction of the computational burden. The proposed method has been investigated for up to 64 harmonics, using LabView software package, under different conditions, and confirmed to be valuable and efficient tool for signal components estimation.

The optimal refined instrumental variable method for the estimation of the Box–Jenkins (BJ) model is modified so that it functions as an optimal filter and state-estimation algorithm. In contrast to the previously developed minimal and non-minimal state-space (NMSS) forms for an Auto-Regressive Moving Average with eXogenous variables (ARMAX) model, the new algorithm requires the introduction of a novel extended NMSS form. This facilitates representation of the more general noise component of the BJ model. The approach can be used for adaptive filtering and state variable feedback control.

A mixed noise model is proposed and the multi-frame blind deconvolution is used to restore the images of space objects under the Bayesian inference framework. To minimise the cost function, an algorithm based on iterative recursion was proposed. In addition, three limited bandwidth constraints of the point spread functions were imposed into the solution process to avoid converging to local minima. Experimental results show that the proposed algorithm can effectively restore the turbulence degraded images and alleviate the distortion caused by the noise.

Paralleling with the revolutionary development of the Internet, there has been increasing concern about the copyright infringement of digital media. A central problem in copyright protection is to accurately and efficiently identify the illegal copies of copyrighted contents. Perceptual hash function, which summarises the perceptual characteristics of digital media to a short digest, is a low-cost solution to this problem. Owing to the easy-to-manipulate nature of digital media, a major challenge in designing perceptual hash function is to achieve the robustness against distortion. To tackle this problem, an associative memory-based hash function is introduced. The proposed work repairs the distortions on local image structures via associative memory-based de-noising, in the hope of simulating the self-correcting mechanism in human memory. The shape invariant descriptors of de-noised structures are then encoded to binary bits. Experimental results confirm that the proposed work outperforms representative algorithms, and it can achieve an equal error rate of in content identification with only 80 bits.

Speeded up robust features (SURFs) are considered to be the most efficient feature extraction algorithm and it has been implemented in powerful hardware for real-time operation due to its characteristics of data-intensive computation of high complexity. Especially, the computational load of the descriptor extraction procedure is very significant and the overall performance of SURF can be improved by speeding up the descriptor extraction step with increasing parallel hardware accelerators. However, simply increasing the hardware accelerators is burdensome because of causing significant area and power consumption. Therefore, a reconfigurable hardware architecture is proposed that enables achieving the maximum performance of the descriptor extraction step with making the best use of the existing accelerators without any additional ones. Experimental results show that the proposed architecture improves the performance of the descriptor extraction step by 24.77–47.45% with negligible area overheads when compared with the existing hardware implementations of the SURF algorithm.

Aperiodic Hamming correlation (APHC) is more accurate to measure performances of the frequency hopping (FH) communication systems than periodic Hamming correlation. A class of no-hit-zone FH sequences (FHSs) with respect to APHC which has not yet been studied previously, is studied. A bound on no-hit-zone FHSs with respect to APHC is established. Further, a class of no-hit-zone FHSs with respect to APHC is constructed, which is optimal with respect to the new bound.

An efficient on-chip leakage sensing unit is proposed, which is composed of four stages. Device under test (DUT) arrays include 16 types of transistors for leakage measurement. Threshold detector monitors the crossing point of inverter threshold causing the transition. Transition time is inversely proportional to the leakage current of the selected DUT. This time information of threshold detector is converted to voltage manner through the time-to-voltage converter with the diode stacked voltage generator. The generated voltage is transferred to voltage controlled oscillator (VCO) for frequency conversion which is the final output of leakage sensor. The proposed sensor provides leakage information of the various types of devices by using the same sub-circuit within on-chip. The prototype sensor occupies 0.00035 mm² area and consumes 1200 μW with eight DUT arrays within a chip. Experimental results show the well-correlated frequency output with device leakage current.

This Letter reports a 360° reflective-type phase shifter in 100-nm InGaAs pHEMT technology. A triple-resonating load technique is proposed and the optimum conditions are derived to achieve full 360° phase-shift range and minimise the insertion loss variation. The implemented reflective-type phase shifter achieves a measured phase-shift range of 360° and an insertion loss of at 94 GHz. Measured return loss is better than 14 dB across 360° phase-shift range.

A simple wideband filtering-response power divider (FPD) with sharp passband selectivity and good UWB isolation is presented. By ingeniously integrating multimode resonators and stub attached coupled-line isolation network, the FPD is initially built. Compared to those in the literatures, the presented wideband FPD features its simple structure and good wideband performance. For demonstration, a prototype FPD with a central frequency of 2.46 GHz and 3 dB fractional bandwidth of 22.8% is implemented. Final results indicate that this FPD possesses not only sharp frequency selectivity and wide stopband attributing to six created transmission zeros, but also an isolation better than 16 dB over an UW isolated frequency band (from DC to 2.67f ⁰).

In this letter, a dual-mode microstrip bandpass filter (BPF) with compact size and high selectivity is designed with a short-stub centred loaded resonator. Owing to the frequency-dependent source–load coupling and the intrinsic characteristics of the short-stub loaded resonator, three transmission zeros that are located near the passband edges and in the upper-stopband can be generated to improve the selectivity. The compact BPF with fractional bandwidth of 3.5% located at 2.4 GHz for WLAN application has been designed and fabricated, and good agreement between simulation and measurement verifies the validity of this design methodology.

A novel microstrip lowpass filter with outstanding features is designed, simulated, fabricated and analysed. The proposed structure has the capability to improve frequency response in transition band and remove the 13th unwanted harmonics in the stopband. The proposed design comprises many resonators and cell attenuators. It features an UW stopband, high suppression factor and high sharp roll-off. To adjust the cut-off frequency, the transfer function and LC equivalent circuit of the main resonator are calculated. Results show that cut-off frequency and relative bandwidth of stopband of the filter are 2 GHz and 171%, respectively. Also, insertion loss <0.11 dB and return loss more than 18 dB have obtained for filter form DC to 2 GHz. The fabricated filter reaches a high figure of merit of 72,093.

A compact seventh-order wideband bandpass filter (BPF) with sharp roll-off skirts using coupled lines and open stubs (OSs)/shorted stubs (SSs) is proposed. Seven transmission poles in the passband and four deep transmission zeros from 0 to 2f ₀ (f ₀ denotes centre frequency of the passband) can be realised with the help of half-wavelength OSs and quarter-wavelength SSs. For demonstration, a wideband BPF prototype is designed, fabricated with a measured 3-dB fractional bandwidth of 78% (1.22–2.77 GHz) and transition band roll-off rates of over 175 dB/GHz. Good agreement between the simulations and measurements validates the design method.

A novel narrowband balanced absorptive bandstop filter (BABSF) with wideband bandpass response is proposed, which consists of four coupled-line sections with open-circuited stubs, two half-wavelength transmission lines, and two ground resistors. Excellent differential-mode response with narrowband bandstop response and wideband bandpass property is realised for high frequency selectivity. Good common-mode suppression can be achieved, rejecting the interference noise. For demonstration, a BABSF prototype operating at 2 GHz is designed with good agreement between simulated and measured results.

A high accuracy optical indoor positioning scheme is proposed and experimentally demonstrated, which only employs a single light-emitting diode (LED) as the beacon and a camera as the receiver. The camera obtains the angle of arrival of the light using the projection model of the lens, and simultaneously works as photodiodes to measure the received light strength with properly controlled analogue gain and exposure time. The joint measured angle of arrival and received light strength are utilised as the fingerprint to determine the position of the receiver. The experimental results show that the proposed positioning scheme achieves a high precision where the 95th percentile accuracy is 1.97 cm.

We propose an all-optical switch based on a microfibre Mach–Zehnder interferometer (MMZI) in which the MMZI is considered with a microfibre loop resonator (MLR) in one arm of it. The authors numerically demonstrate that the enhanced phase shift of the MLR near its resonance wavelengths can be used for constructive/destructive interference and switching functionality of the MMZI. The calculated switching threshold power of the switch is about 2 mW, which can be further reduced by the use of an MLR with more finesse, and the rising and falling times are computed with 21 and 91 ps, respectively. Natural connection to silica single mode fibres, easy configuration and high speed make it as a suitable choice for all-optical signal processing and communications applications.

The dual active bridge (DAB) is the mostly used DC–DC converter in bidirectional power flow applications. It has several advantages such as high-power density, galvanic isolation, robustness, among others. However, in applications in which direct and reverse power flow have great difference, the converter efficiency can be penalised. A recent proposed isolated converter known as integrated full-bridge-forward DC–DC converter is specifically designed to this application and has low number of active devices compared to DAB converter. In order to evaluate the features of both converters, this Letter proposes a comparative analysis between these two topologies. Besides theoretical details about the converters, this Letter focuses on the comparison of experimental results, including efficiency and zero voltage switching range.

Automatic target recognition of ground surveillance radars is a beneficial practice that reduces cost, error, duration of detection and response time. The identification of echoes from eight classes using an RF pulsed Doppler radar is studied. Instead of traditional methods, the wavelet packet analysis (WPA) is used. WPA, by providing arbitrary time–frequency resolution, enables analysing signals of stationary and non-stationary nature. It has better time representation than Fourier analysis and better high-frequency resolution than wavelet analysis. WPA subimages are further analysed to obtain feature vectors of log energy entropy in all cases except one case where norm entropy is used. These features are fed into a multilayer perceptron for classification which is done in a hierarchical scheme and composed of binary classification steps. Hundred per cent accuracy was possible in all steps except two which were realised at 99.5 and 98.2%. An overall classification rate of 98.2% was achieved. The results were compared with other published results that report accuracy in the same application field. The proposed method achieved the highest accuracy although it had the highest number of classes. The method provides a promising tool for the automatic recognition of ground surveillance radar targets.

In multi-channel high-resolution and wide-swath (HRWS) synthetic aperture radar (SAR) processing, range sampling time errors and phase mismatches severely degrade the reconstruction performance of unambiguous Doppler spectrum. To address this problem, an improved channel mismatch estimation algorithm for multi-channel HRWS SAR is presented in this Letter. The technique of combining phase wrapping and weighted least-squares fitting is capable of realising a robust estimation of range sampling time errors and constant phases between adjacent channels. Then, Doppler centroid as well as channel phase mismatches can be estimated from these constant phases based on the theory of spatial cross-correlation coefficient (SCCC). Compared to the conventional algorithm, the improved performance can be achieved by using the proposed two-step procedure. The effectiveness of the proposed algorithm is confirmed by experimental results based on airborne real data.

This Letter presents an interferometric synthetic aperture radar (InSAR) imaging method based on L1 regularisation joint reconstruction model via complex approximated message passing (CAMP). The proposed method enables to ensure the preservation of background information via CAMP and interferometric phase difference information among multiple channels via L1 regularisation joint reconstruction model. Compared with conventional matched filtering results, the proposed method can improve the performance of interferometric phase noise reduction and the continuity of interference fringes, which has broad application prospect in InSAR imaging. Experiments carried out on real data confirmed the effectiveness of the proposed method with improved performance.

This Letter presents an Si FinFET on heterodielectric BOX, where the effect of trap charges can be avoided. The investigation is based on a 3D simulation study. The BOX height also plays a significant role in the device characteristics. The effect of trap charges using homodielectric and heterodielectric BOX is verified by plotting the electron density across a 2D cross section in the middle of the channel. The authors further investigated the effect of temperatures, ranging from room temperature to higher temperatures. The FinFET, with heterodielectric BOX, shows no trap effect even when the temperature is varied. On the other hand, a visible temperature effect is observed in case of homodielectric BOX. Moreover, in case of homodielectric BOX, the ON–OFF performance metric, (Q) is affected in presence of trap charges; whereas no change is observed when a heterodielectric BOX is used. As such, it is found that the FinFET with heterodielectric BOX is more reliable and useful for current semiconductor industries.

A multi-stage least mean square (MLMS) algorithm based on polynomial fitting in time-varying systems is proposed. As the name implies, the MLMS algorithm is divided into different stages in sequence. In non-stationary environments, the optimal weight coefficients of the adaptive filter are variable with time and they are assumed to be approximated by a polynomial. According to the conditions above, the convergence of the MLMS algorithm is verified through theoretical analysis and formula derivation. Similar to the least mean square (LMS) algorithm, the step size μ must be chosen in the specific range to guarantee the feasibility and effectiveness of the MLMS algorithm. Compared with the LMS, LMF and NLMS algorithms, the MLMS algorithm provides the best convergence performance in the simulation experiments.

Learning automata (LA) has been widely encountered in signal processing for images, speeches, videos and so on. One special type of LA, i.e. the CALA (continuous action-set LA) issue is handled. It first fills the existing gap aimed at the classic Beigy's algorithm, based on which a novel adaptive CALA (ACALA) algorithm is proposed. The proposed ACALA algorithm includes a sampling process and an iterating process, where the learning parameters are adaptively adjusted, not only between the two stages but also inside the core stage. Experiments with regard to noisy function optimisation reveal its outperformance, in accordance with the general evaluation system built. Specifically, the final result of the proposed algorithm could always judge as the global optimum even in noise-added scenarios, regardless of the initial parameters.

This Letter presents a sufficient condition under which the multipath matching pursuit (MMP) algorithm recovers sparse signals perfectly in compressive sensing problems. The derived sufficient condition is much more relaxed than the existing one.

A novel oscillator-based adaptive notch filter (OSC-ANF) algorithm is presented. The proposed algorithm has robustness against the impulsive noise because it is derived by using the maximum correntropy criterion (MCC). In addition, the variable step-size MCC-OSC-ANF algorithm is proposed to improve the frequency estimation performance. Experimental results show that the proposed algorithms perform better than the previous algorithm under impulsive noises.

The energy optimisation problem of wireless communications as a power consumption tradeoff between the transmitter and receiver is considered. The goal is finding the right balance between the transmission power and the amount of digital signal processing at the receiver. The problem then consists of deriving the optimal signal-to-noise ratio. Receiver cost functions from real implementations are defined and the constrained optimisation problem for single and multiuser links is solved. The numerical analysis shows that there is an optimal ratio between transmission power and signal processing which can lead to a 30% power reduction for noise limited systems.

The multi-slot reservation-based hybrid medium access control (MAC) protocol with collision prevention is analysed under a high-density deployment scenario. Extensive simulations are conducted to validate the accuracy of the proposed model (i.e. within 4% maximum relative error), which plays a theoretical guiding role in the MAC layer design and optimisation of a heterogeneous network system.

In multi-untrusted relay networks, the transmission should be carefully devised to guarantee both security and performance. A novel scheme with symbol separation and beamforming is proposed to improve secure transmission. First, the best two relays with the strongest channel gains are selected to deliver the separated real and imaginary parts of the confidential symbols. Then, directional beamforming is carefully designed to maximise the receptions of the real and imaginary parts at the two selected relays and to zero force the receptions at the other relays. The proposed scheme ensures a perfect physical layer security with high BER at untrusted relays, and an improved BER performance at the destination. Numerical simulations show the correctness and efficiency of the proposed scheme.