In this Letter, the authors propose to apply the harmonic regeneration noise reduction (HRNR)-based Wiener filter (W-HRNR) to detect acoustic emission (AE) signal from the noisy environment. HRNR technique can regenerate the harmonics to overcome the distortion which occurs with overestimation of conventional Wiener filter and to preserve the essential signal content for accurate detection of AE signal. W-HRNR is implemented in short-time Fourier transform domain. Decision direct method is employed to estimate the spectral gain and signal-to-noise ratio (SNR) of the signal in each frame. Evaluation of the algorithm is carried out using peak-SNR (PSNR) and mean square error (MSE). The performance of the proposed algorithm has been demonstrated using a simulated AE burst signal and AE signals acquired from compression test and drilling test. Results have proven the remarkable performance of W-HRNR over existing conventional Wiener filter for AE with accurate detection by preserving the useful signal information even under high noise conditions at low frequencies. Moreover, W-HRNR also achieved a significant improvement in PSNR and MSE over the conventional filter.

In this letter, to overcome the drawbacks in reconfigurable antennas and maintain all the advantages in planar antennas, a compact 12 port integrated UWB and narrow band (NB)/wideband antennas for cognitive radio MIMO applications with polarisation diversity is presented. The proposed system has one pair of UWB antennas for sensing the spectrum and five pairs of NB/wideband antennas for communication. Each pair has two identical antennas, which are orthogonal to each other for polarisation diversity. Sensing antennas linked with ports (P1 and P7) have operating bandwidth of 3–11 GHz, whereas the antennas linked with ports (P2 and P8), (P3 and P9), (P4 and P10), (P5 and P11), and (P6 and P12) have operating bandwidths of 3.5–5.8 GHz, 2.8–3.5 GHz and 5.6–8 GHz (dual band), 8–8.4 GHz and 9–9.8 GHz (dual band), 8.4–9 GHz, and 9.8–11 GHz, respectively. Moreover, the overall volume of the antenna is 58mm × 50mm × 1.6 mm and the entire UWB spectrum is covered by NB/wideband antennas. Also, without any decoupling network, isolation of better than 20 and 15 dB is achieved between every two identical and non-identical antennas, respectively.

A reflective metasurface based on the quasi-spiral element is proposed to achieve broadband orbital angular momentum vortex beams for multi-polarisations. The quasi-spiral element can provide linear and smooth phase responses covering about 360° from 10 to 15 GHz with a relative bandwidth about 40% by adjusting the length of four phase delay lines. Additionally, the metasurface can generate vortex beams with optional charges in vertical, horizontal and circular polarisations which are determined by the polarisation of feed antenna. Finally,we have designed and fabricated a 24 × 24 cm² metasurface prototype. The simulated and measured results show that the reflective metasurface can generate broadband vortex beams with orbital angular momentum effectively. As the structure is simple, lightweight and easy to fabricate, the proposed method is applicable to generate broadband vortex beams for multi-polarisations.

The capability of orthogonal projection (OP) approach degrades severely in the presence of array model mismatch, especially when the training samples are mixed with the strong desired signal. Therefore, an improved OP robust adaptive beamforming is proposed based on correlated projection and eigenspace processing in wide input signal-to-noise ratio to remove the desired signal self-null effect and improve robustness. In the proposed approach, the interference subspace is constructed combining the correlated projection and eigenspace processing first. Then, the interference-plus-noise covariance matrix is accurately reconstructed via super-resolution spatial spectrum estimator to eliminate desired signal from sample covariance matrix. Subsequently, the desired signal steering vector is corrected applying correlated projection and then the adaptive weighted vector is modified by OP approach. Simulation results demonstrate that the capability of the proposed approach is almost consistently same as the optimal beamformer in many scenarios.

A wideband circularly polarised patch antenna with multi-section λ/4 transmission lines is proposed. The multi-section lines are directly connected to the patch radiator. The feeding circuit and patch are on the same layer, which makes it easy for integration. There is no coupling structure, and consequently, the parasitic radiation from the feeding circuit can be minimised. The whole antenna structure is designed according to the traditional filter design theory. Two minima in the axial ratio response come up to achieve wideband characteristic. Finally, the proposed antenna structure and wideband performances are experimentally verified by an antenna prototype.

In this Letter, four differential All-Pass Networks are presented to introduce phase-shift at millimetre waves using a linear-phase synthesis procedure. The proposed networks achieve 1-3.5 dB insertion loss while having across the whole bandwidth, showing an almost constant group-delay, an RMS gain error of less than 0.15 dB and a phase-error of less than .

Multi-row read plays an important role in in-memory computing and its precision affects the accuracy of the calculation. In this brief Letter, a discharge compensation method is proposed for the linearisation of multi-row read operations in static RAM. Current mirrors are added to bitlines to compensate for the discharge voltage. With compensation, the integral non-linearity decreases by 72% compared with the situation without compensation. In addition, a wordline signal generation circuit based on replica bitline is proposed to reduce area cost.

Spin-orbit torque magnetic tunnel junction (MTJ) based non-volatile flip-flops (NVFFs) have been introduced to provide zero-leakage standby state without data loss in power-gating mode. In this Letter, the data-aware backup scheme for NVFF, where significant energy can be saved by performing data backup only when the stored data and the current data are different is proprosed. Low-area backup signal generator is also proposed for the proposed data backup scheme. The simulation results with 65 nm process show 88.7% reduction in backup energy when the stored data and the current data are equal.

This Letter proposes a fusion strategy for multistream convolutional networks, the lattice cross fusion. This approach crosses signals from convolution layers performing mathematical operation-based fusions right before pooling layers. Results on a purposely worsened CIFAR-10, a popular image classification data set, with a modified AlexNet-LCNN version show that this novel method outperforms by the baseline single stream network, with faster convergence, stability and robustness.

Uniform constant composition codes are particular cases of constant composition codes, where every symbol of the alphabet appears times in the codewords. A construction of optimal uniform constant composition codes with no restrictions over the alphabet is presented.

Low density parity check (LDPC) codes are still intensively studied investigating their iterative decoding convergence performance. Since the probability distribution function of the decoder's log-likelihood ratio messages was observed to be approximately Gaussian, a variety of low-complexity approaches to this investigation were proposed. One of them was presented in Chung et al.'s 2001 paper, involving the function , therein specified, and its inverse. In this Letter, a new approximation of the function is given, such that, unlike the other approximations found in the literature, it is defined by a single expression (i.e. it is not piecewise defined), it is explicitly invertible, and it has less relative error in any x than the other approximations.

This Letter presents a radio-frequency energy storage solution for monitoring corrosion on bridge in wireless sensor network system. In this monitoring system, wireless terminals and sensors are installed on the bridges to monitor surface corrosion remotely. The proposed energy storage module to supply power to the sensors consists of a rectifier, a supercapacitor, and a DC–DC boost converter. The rectifier circuit is designed to convert 920 MHz RF energy to DC source. Experimental results demonstrate that the harvested energy can power up the sensor nodes for several times in a week, at input power density of 0.81 μW/cm².

A new three-state switchable diplexer based on dual-mode stub-loaded stepped-impedance resonators (SL-SIRs) has been proposed. The three-state diplexer comprised six SL-SIRs with a distributed coupling structure. By appropriately adjusting the structural parameters of the SL-SIRs, a two-pole filtering response can be implemented at each channel passband. In addition, three p-i-n diodes, which were connected to the T-junction of the input coupled-line, were used to control the switching between the three operating states. Moreover, each operating state can be switched independently. For the purpose of demonstration, a three-state switchable diplexer was designed and fabricated using microstrip technology. The simulated results were consistent with the measured results, which indicate that the proposed switchable diplexer not only has a good in-band performance but also provides good isolation of better than 25 dB between output channels.

Regenerative amplification of 946 nm pulses which are sliced from 12 mW continuous wave laser diode is reported. Near-transform-limited 2.9 ns pulses with highly stable and smooth temporal shape were obtained with the energy of 25 mJ/50 Hz and M ² < 1.2.

SAR tomography is an important way for the 3D reconstruction of urban areas. Facade extraction is a very important procedure in the 3D reconstruction of buildings. Density estimation and curve model are common ways to extract facade points. However, it may fail to locate the facade position when the building is relatively low. In this Letter, multipath-based information of building structures are incorporated for the 3D reconstructions of buildings based on SAR tomography. Facade points can be detected with additional features. Experiments are carried out to show the validity of the authors' methods.

Tomography SAR (TomoSAR) imaging can achieve three-dimensional (3D) imaging, which is significant for urban 3D mapping. When the baseline of TomoSAR is sparse, the scattering centres of several different altitudes in the same resolution unit are aliased together, which affects the accuracy of TomoSAR imaging. To solve this problem, an altitude ambiguity suppression method based on dual-frequency interfering and multi-frequency averaging is proposed. Firstly, dual-frequency interfering is used to obtain the radar cross-section (RCS) of targets and the sum of the results of the cross interference between targets and ambiguities in different positions. Then multi-frequency averaging is used to suppress the power of the cross-interference, and finally the RCS of target is accurately obtained. Simulation results verify the effectiveness of the proposed method.

When driving on an iron-bridge, stationary iron-clutters cause disturbances in the detection of a moving target in an automotive radar system. In this Letter, the authors propose a moving target detection method that utilises phase similarity of the spatial domain on an iron-bridge. To analyse the spatial domain via the array antenna signal of the up- and down-chirp beat-frequencies, the frequency-modulated continuous wave (FMCW)-phased array radar signal was used. It is possible to match the up- and down-chirp beat-frequencies of each object, moving target, and stationary iron-clutters, by using the proposed method. Not only the moving target but also the ego-vehicle and moving target velocity are detected through this matching. The suitability of the proposed method is verified by on-road measurement data using a 77 GHz FMCW-phased array radar.

By means of the restricted isometry property of order k and the restricted orthogonality property of order (k,k), this Letter mainly establishes an improved sufficient condition for a recently emerged -minimisation to guarantee the robust signal recovery. The obtained condition is proved to be much better than the state-of-the-art ones for almost all parameters k.

In this work, the software-defined perimeter (SDP) is considered for the Message Queuing Telemetry Transport (MQTT) protocol framework in the Internet of Things (IoT) applications. In fact, the SDP provides an additional layer of security with or without SSL/TLS by replacing the traditional login method (username/password) with a single-packet authorisation (SPA) process. This will blacken the end devices, by cloaking and causing them to be inaccessible by attackers. Consequently, this prevents the log-in information from being compromised in the absence of encryption. Eventually, the framework is evaluated through an implementation testbed and system proved to be secure against denial of service active and off-line dictionary types of attacks, even with the use of weak login credentials. All the while, achieving measurable efficiency over the traditional use of MQTT.

In the process of maximising the utilisation of spatial and radio resources, interference is the major factor limiting the system capacity. In this Letter, a novel multi-carrier signal alignment (MCSA) scheme based on diagonal-block channel matrix is first proposed, to mitigate the interference in downlink multi-input multi-output non-orthogonal multiple access (MIMO-NOMA) cellular networks. The maximum degree of freedom (DoF) can be achieved by the iterative design of MCSA. Simulation results show the effectiveness and superiority of the proposed MCSA scheme in improving the sum-rate and DoF, by fully using multiple antennas and multiple carriers.