bluuebunny/crossref_metadata_2025_split huggingface dataset:
Highly compact quad‐band bandpass filter with flexibly controllable passbands
Authors: Zhang Fan , Gao Yang , Wang Yi , Zhang Yi , Dong Yuliang , Xu Jun 
Published: January 2021

AbstractThis letter reports a highly compact microstrip quad‐band bandpass filter based on two folded λ/4 stepped impedance resonators and three folded dual‐mode short stub‐loaded resonators. The two stepped impedance resonators not only form the first passband but also serve as the feed structure and provide the source‐load coupling path for the three higher passbands created by the short stub‐loaded resonators. Thus, a compact size can be obtained, and three pairs of transmission zeros can be realised near the three higher passbands to improve the frequency selectivity. It has been shown that the centre frequencies and bandwidths of the four passbands can be controlled independently. A microstrip quad‐band bandpass filter centred at 1.1/2.05/3/3.55 GHz is implemented and tested achieving an extremely small size of 0.07λg × 0.14λg, where λg is the guided wavelength at 1.1 GHz. This presents one of the smallest quad‐band bandpass filter ever demonstrated in the literature.
Low‐profile circularly polarized metasurface antenna with tailored reflection phase
Authors: Zhao Yi , Yao Xu , Wang Chun‐yu 
Published: January 2021

AbstractA low‐profile metasurface antenna with circularly polarized radiation and tailored anisotropic reflection is proposed in this letter. The metasurface antenna composed of excitation structure (microstrip line with coupling slot) and a metasurface layer. The metasurface functions for two goals, generating circularly polarized wave for radiation and tailoring reflection phase for scattering, respectively. The overall structure of the metasurface antenna is compact with a dimension of 0.67λ × 0.67λ × 0.05λ at 5 GHz. Numerical and measured results confirm that the metasurface antenna exhibits 11.1% −10 dB S11 bandwidth from 4.68 to 5.23 GHz, 10.8% 3 dB axial ratio bandwidth from 4.782 to 5.37 GHz and a maximum gain of 6.83 dBic. Besides, the metasurface antenna achieves anti‐phase reflection under orthogonal polarized incident waves at around 5 GHz. To demonstrate a potential application, 16 identical metasurface antennas are put in a 4 × 4 array. The metasurface antenna array achieves directive circularly polarized radiation with a maximum gain of 15 dBic. On the other hand, when under normal illumination, the scattering field of metasurface antenna array is redistributed due to phase cancelation, so that the backward radar cross section of the array is significantly reduced, which is applicable for military platform.
G‐MGF based performance analysis of coherent FSO systems with multiple receivers
Authors: Jeong Seongah , Kang Jinkyu , Lee Hoojin 
Published: January 2021

AbstractThis letter investigates the performance of coherent free‐space optical systems with multiple receivers especially through the generalised moment‐generating function based approach. Specifically, we first derive a closed‐form expression of the generalised moment‐generating function of the signal‐to‐noise ratio for the coherent free‐space optical systems. The derived generalised moment‐generating function formula is further utilised to effectively analyse the several performance metrics such as amount of fading and ergodic capacity. The accuracy of our theoretical analyses are corroborated via some numerical results.
AC amplifiers with ultra‐low corner frequency by using bootstrapping
Authors: Martincorena‐Arraiza Maite , Carlosena Alfonso , de la Cruz‐Blas Carlos A. , Lopez‐Martin Antonio J. 
Published: January 2021

AbstractA novel architecture for an AC (i.e. high‐pass) amplifier is proposed allowing a drastic reduction of the cutoff frequency to the sub‐Hertz range. It builds upon the classic AC configuration with a high gain amplifier and a parallel RC circuit in the feedback loop, by increasing the feedback resistance through bootstrapping. Resistance multiplying factors higher than four orders of magnitude are easily achievable. The basic principle can be applied to several practical implementations, though in this letter it is demonstrate with measurement results of an op‐amp based discrete implementation.
AlGaN/GaN high electron mobility transistor oscillator for high temperature and high frequency
Authors: Palacios Paula , Wei Muh‐Dey , Zweipfennig Thorsten , Hamed Ahmed , Beckmann Carsten , Kalisch Holger , Vescan Andrei , Negra Renato 
Published: January 2021

AbstractA high‐temperature 2.1 GHz oscillator based on a AlGaN/GaN high electron mobility transistor (HEMT) is successfully designed, implemented, and characterised for the first time. The system is explicitly designed such that the final circuit consists of a single transistor bonded to a printed circuit board (PCB), and no further passive components besides the transmission lines to attach the connectors are used. Extensive characterisation of the high electron mobility transistor has been carried out up to 300C in order to extract large‐ and small‐signal models. Since the system does not rely on passive tolerances and a specific model of the used transistor has been extracted, a sustainable oscillation of the design at high temperature is assured. The capabilities of the designed circuit are verified by measurements up to 230C, showing a promising performance with around 0 dBm output power and a phase noise of −74 dBc/Hz at 1 MHz offset at the highest characterised temperature.
Stable ant‐antlion optimiser for feature selection on high‐dimensional data
Authors: Li Mengmeng , Qin Wei , Zhang Jinhui , Wang Jichuan , Zheng Qibin , Liu Yi 
Published: January 2021

AbstractHigh‐dimensional data exists widely in the real world, such as gene, magnetic resonance imaging (MRI), text, web data and so on. Feature selection is an effective and powerful method that is often adopted to reduce dimensions of high‐dimensional data for promoting learning algorithm's ability to obtain useful information from them. However, feature selection stability lacks attention for a long time, which plays an important role in getting compelling results. This study proposes a stable feature selection approach called stable ant‐antlion optimiser (SALO) that is a modified hybrid evolutionary method combining ant colony optimisation and antlion optimiser. Several relative stable filter methods are employed to rank features as guide information, fisher discriminant rate is used to evaluate features as heuristic information, and F1 indicator and the similarity between feature subset and stable ranked feature list are taken as optimisation objects. Comprehensive experiments show the fantasy stability and excellent classification performance of our proposed sophisticated method.
CMOS image sensor for wide dynamic range feature extraction in machine vision
Authors: Kim Hyeon‐June 
Published: January 2021

AbstractThis letter presents a wide dynamic range (WDR) feature extraction (FE) readout scheme for machine vision applications using CMOS image sensors (CISs). The proposed scheme with the proposed pixel structure has two operating modes, the normal and WDR modes. In the normal operating mode, the proposed CIS captures a normal image with high sensitivity. In addition, as a unique function, a bi‐level image is obtained for real‐time FE even if a pixel is saturated in strong illumination conditions. Thus, compared to typical CISs for machine vison, the proposed CIS can reveal object features that are blocked by light in real time. In the WDR operating mode, the proposed CIS produces a WDR image with its corresponding bi‐level image. A prototype CIS was fabricated using a standard 0.35‐μm 2P4M CMOS process with a 320 × 240 format (QVGA) with 10‐μm pitch pixels. At 60 fps, the measured power consumption was 5.98 mW at 3.3 V for pixel readout and 2.8 V for readout circuitry. The dynamic range of 73.1 dB was achieved in the WDR operating mode.
Design of cooperative matched filter for detection of chemical agents
Authors: Yu Hyeong‐Geun , Lee Chang Sik , Park Dong‐Jo , Chang Dong Eui , Nam Hyunwoo 
Published: January 2021

AbstractA matched filter (MF) is one of the most widely used detectors for the detection of chemical agent (CA) clouds in the passive hyperspectral imaging system. To improve the detection performance of the MF, a linear cooperation scheme that allocates cooperation coefficients to the spectra of the neighbouring pixels is proposed. The optimal cooperation coefficients, which removes noise signatures whilst minimising the distortion of CA signatures, are acquired by finding the maximum likelihood estimator of the cooperation coefficients. It is proved that a moving average scheme that assigns the same coefficients is the optimal cooperation scheme. Finally, a cooperative MF with the optimal cooperation scheme is designed. It is demonstrated that the proposed cooperative MF is capable of robust detection performance via outdoor experiments with actual CA data measured by a Bruker HI‐90 instrument.
A 190.3‐dBc/Hz FoM 16‐GHz rotary travelling‐wave oscillator with reliable direction control
Authors: Sun Fangzhou , Zhou Yushi , Bai Zhanjun , Chen Yong 
Published: January 2021

AbstractThis letter presents a rotary travelling‐wave oscillator (RTWO) with reliable direction control in a standard 130 nm complementary metal–oxide–semiconductor (CMOS) technology. To achieve low phase noise (PN), and low power consumption, 16‐stages customised transmission line segments are designed and simulated on electromagnetic tools. The PN is investigated through modelling the RTWO as multiple standing‐wave oscillators. The proposed oscillator achieves 11.2% tuning range, 190.3 dBc/Hz figure‐of‐merit (FoM) at 1 MHz offset and 192.3 dBc/Hz FoM at 10 MHz offset with 5.8‐mW power consumption from 16‐GHz carrier.
Hybrid automatic repeat request‐based intelligent reflecting surface‐assisted communication system
Authors: Ai Yun , Mohamed Marshed , Kong Long , Al‐Saman Ahmed , Cheffena Michael 
Published: January 2021

AbstractThe intelligent reflecting surface (IRS) is an emerging technique to extend wireless coverage. In this letter, the performance of the hybrid automatic repeat request (hybrid ARQ) for an IRS‐assisted system is analysed. More specifically, the outage performance of the IRS‐aided system using hybrid ARQ protocol with chase combining is studied. The asymptotic analysis also shows that the outage performance is better and improves linearly by increasing the number of reflectors of the IRS‐aided system. The results also verify the potential of combining the ARQ scheme in the link layer of the IRS‐aided system and demonstrate that a very small change of path loss condition can impact the performance largely.
Cogging torque reduction based on segmented skewing magnetic poles with different combinations of pole‐arc coefficients in surface‐mounted permanent magnet synchronous motors
Authors: Xing Zezhi , Wang Xiuhe , Zhao Wenliang 
Published: January 2021

AbstractThe calculation and reduction of cogging torque are fundamental to the evaluation and optimisation of motor performance. Considering that the accuracy of the cogging torque calculated by analytical method (AM) is low, an accurate calculation model of the effective air‐gap length considering the actual stator slot structure and suitable for any motor is proposed, the cogging torque of 6p36s surface‐mounted permanent magnet synchronous motor (SPMSM) are calculated accurately and verified by finite element method (FEM). Furthermore, the segmented skewing magnetic poles with different combinations of pole‐arc coefficients are designed to weaken cogging torque, and the optimal combination of pole‐arc coefficients and tilting angle of the adjacent magnetic poles are summarised by AM and particle swarm optimisation (PSO) algorithm. Finally, the cogging torques of six SPMSMs with different slot‐pole combinations including 6p36s, 4p36s, 6p9s, 8p9s, 8p12s and 10p12s are analysed, and the results indicate that the cogging torque can be greatly weakened based on segmented skewing magnetic poles with different combinations of pole‐arc coefficients, and other performances of the motors are basically not affected.
Medium frequency diode rectifier unit based HVDC transmission for offshore wind farm integration
Authors: Zhang Zheren , Tang Yingjie , Xu Zheng 
Published: January 2021

AbstractThe offshore wind farms are the main trend of the wind power development in the future. The medium frequency diode rectifier unit based high voltage direct current transmission system is proposed here for offshore wind farm integration. Unlike conventional high voltage direct current solutions, the rated frequency of the offshore alternating current (AC) grid is increased to about 100∼400 Hz in the proposed system. Besides, a grid‐forming control scheme for the wind turbine converters is also proposed in this paper, where the machine side converter controls the direct current (DC) voltage and the grid side converter controls its output alternating current voltage in the global unified reference coordinate system. As a result, smaller and lighter passive components, such as the transformers, alternating current filters and reactive power (VAR) compensators, could be adopted in the offshore grid, which is beneficial for achieving higher economic efficiency. The small stability analysis and the time domain simulation of the proposed system are carried out based on a simplified model and power systems computer aided design/electromagnetic transients including DC (PSCAD/EMTDC) respectively, and the feasibility of the proposed schemes is verified.
Linear multi‐vector model‐based predictive control for grid side converters of renewable power plants under severe grid disturbances
Authors: Ramirez Dionisio , Castillo Rafael De Jesus , Zarei Mohammad Ebrahim , Serrano Javier 
Published: January 2021

AbstractGrid side converters of renewable power plants have to be capable of dealing with severe grid disturbances, such as, grid faults and voltage sags. Model‐based predictive control provides outstanding performance to grid side converters: fast dynamic response, good tracking error and high‐quality currents. However, choosing the best set of vectors for the modulation requires assessing all the possible combinations of vectors using a cost function, which is very time consuming. Thus, the modulation is normally carried out with only 1 or 2 vectors per PWM period to save computing time, but this turns the modulation non‐linear. This lack of linearity makes it impossible to use symmetrical components in unbalanced grids. A linear multi‐vector model‐based predictive control that controls the power of both sequences using a sole cost function and analyses the effect of the transient response of several sequence decomposition systems on the model‐based predictive control predictions and dynamic response is proposed. Moreover, the proposed multi‐vector provides low THD currents while keeping the computing time low. In addition, the paper addresses the extrapolation of the proposed multi‐vector model‐based predictive control to N‐level converters. The good performance obtained is supported by the results obtained in simulations and the laboratory.
Wake‐effect aware optimal online control of wind farms: An explicit solution
Authors: Chen Kaixuan , Qiu Yiwei , Lin Jin , Liu Feng , Zhao Xiaowei , Song Yonghua 
Published: January 2021

AbstractWake effects impose significant aerodynamic interactions among wind turbines. To improve the wind farm operating performance, practical wind farm online control considering wake effects becomes very important. To achieve online optimal wind farm control while responding to grid demands, this paper proposes a novel optimal wind farm supervisory control (SC) model and its explicit solutions. From the controller modelling perspective, the two major wind farm operating modes, the maximum power point tracking mode and the set‐point tracking mode, are first analysed and unified in one optimisation model while considering wake effects. In this way, wind farm power production and rotor kinetic energy reserve can be simultaneously considered to conveniently modify the operation mode in response to different grid demands. Aside from controller modelling, the collocation method is first introduced to address the online application problem of such wake‐effect aware optimal WF control. Although a few optimisation algorithms have been proposed to find the optimum offline, online optimal control is still challenging because of the computational complexity brought by wake model non‐linearity and non‐convexity. The proposed collocation method explicitly approximates the optimal solutions to the proposed supervisory control model, through which only a direct algebraic operation is required for online optimal control instead of repeated optimisations. Case studies are carried out on different wind farms under various wind conditions, showing that the wind farm power production potential and releasable power reserve are improved compared to traditional greedy control in both modes. The accuracy of the collocation method is verified. A detailed analysis of the wind farm production capacity under different wind speeds and directions is also provided.
Ultra‐short‐term multi‐step wind power forecasting based on CNN‐LSTM
Authors: Wu Qianyu , Guan Fei , Lv Chen , Huang Yongzhang 
Published: January 2021

AbstractThe fluctuation and intermission of large‐scale wind power integration is a serious threat to the stability and security of the power system. Accurate prediction of wind power is of great significance to the safety of wind power grid connection. This study proposes a novel spatio‐temporal correlation model (STCM) for ultra‐short‐term wind power prediction based on convolutional neural networks‐long short‐term memory (CNN‐LSTM). The original meteorological factors at multi‐historical time points of different sites throughout the target wind farm can be reconstructed into the input window of the model, and thus a new data reconstruction method is represented. CNN is used to extract the spatial correlation feature vectors of meteorological factors of different sites and the temporal correlation vectors of the meteorological features in ultra‐short term, which are reconstructed in time series and used as the input data of LSTM. Then, LSTM extracts the temporal feature relationship between the historical time points for multi‐step wind power forecasting. The STCM based on CNN‐LSTM proposed in this study is suitable for wind farms that can collect meteorological factors at different locations. Taking the measured meteorological factors and wind power dataset of a wind farm in China as an example, four evaluation metrics of the CNN‐LSTM model, CNN and LSTM individually used for multi‐step wind power prediction, are obtained. The results show that the proposed STCM based on CNN‐LSTM has better spatial and temporal characteristics extraction ability than the traditional structure model and can forecast the power of wind farm more accurately.
Control of solar PV‐integrated battery energy storage system for rural area application
Authors: Chauhan Shubhra , Singh Bhim 
Published: January 2021

AbstractThe inaccessibility of a utility grid is the challenge for rural and remote areas. This work presents the application of solar photovoltaic (PV) integrated battery energy storage (BES) for rural area electrification. The addition of a BES at DC link, is realised by means of a DC–DC bidirectional converter. The BES is discharged/charged in accordance with the solar PV generation and load variations. This converter control also maintains the voltage for the maximum power point tracking (MPPT) with perturb and observe (P & O) control at the DC link. The voltage source converter (VSC) works by means of voltage control algorithm in a solar PV‐BES system. The system manages the power for the load network with frequency and voltage regulation by the non‐ideal discrete proportional and resonant controller (PR). The fundamental component from the load current, is acquired using an adaptive digital filter, which improves the power quality. The utilization of buck‐boost converter with an optimum BES rating as related to the system, when it is linked directly at the VSC DC link. The system's operations at steady state and dynamic circumstances i.e. solar insolation change and load variation, load disconnection, are authenticated with test results on a developed prototype.
A current sensor based adaptive step‐size MPPT with SEPIC converter for photovoltaic systems
Authors: Kumar Vipin , Ghosh Sandip , Naidu N. K. Swami , Kamal Shyam , Saket R. K. , Nagar S. K. 
Published: January 2021

AbstractEfficient maximum power point tracking (MPPT) is an important problem for renewable power generation from photovoltaic systems. In this work, a current sensor based MPPT algorithm using an adaptive step‐size for a single ended primary inductance converter (SEPIC) based solar photovoltaic system is proposed. Due to lower sensitivity of power to current perturbation as compared to the voltage one, such a scheme is shown to yield better efficiency at steady‐state. A new adaptation scheme is also proposed for faster convergence of the MPPT technique. Hence, the proposed scheme yields better transient as well as steady‐state performance. A prototype converter is used along with digital implementation of the proposed MPPT technique to demonstrate the superiority of the proposed algorithm over the fixed step‐size and voltage based ones. Simulation and experimental results corroborates the same.
High-resolution international LOFAR observations of 4C 43.15
Authors: Sweijen F. , Morabito L. K. , Harwood J. , van Weeren R. J. , Röttgering H. J. A. , Callingham J. R. , Jackson N. , Miley G. , Moldon J. 
Published: January 2021

It has long been known that radio sources with the steepest spectra are preferentially associated with the most distant galaxies, the α − z relation, but the reason for this relation is an open question. The spatial distribution of spectra in high-z radio sources can be used to study this relation, and low-frequency observations are particularly important in understanding the particle acceleration and injection mechanisms. However, the small angular sizes of high-z sources together with the inherently low resolution of low-frequency radio telescopes until now has prevented high angular resolution low-frequency observations of distant objects. Here we present subarcsecond observations of a z = 2.4 radio galaxy at frequencies between 121 and 166 MHz. We measure the spatial distribution of spectra, and discuss the implications for models of the α−z relation. We targeted 4C 43.15 with the High Band Antennas of the International LOFAR Telescope with a range of baselines up to 1300 km. At the central frequency of 143 MHz we achieve an angular resolution of ~0.3″. By complementing our data with archival Very Large Array data we study the spectral index distribution across 4C 43.15 between 55 MHz and 8.4 GHz at resolutions of 0.4″ and 0.9″. With a magnetic field strength of B = 5.2 nT and fitted injection indices of αinjnorth = −0.8 and αinjsouth = −0.6, fitting a Tribble spectral ageing model results in a spectral age of τspec = 1.1 ± 0.1 Myr. We conclude that our data on 4C 43.15 indicates that inverse Compton losses could become comparable to or exceed synchrotron losses at higher redshifts and that inverse Compton losses could be a viable explanation for the α−z relation. Statistical studies of these objects will become possible in the future when wide-area subarcsecond surveys start.