bluuebunny/crossref_metadata_2025 huggingface dataset:
Wideband signal DOA estimation method based on keystone transform
Authors: Wang Ning , Zhou Ming , Zhong Bing , Li Siming , Chen Yawei
Published: October 2019

Here, a wideband signal direction‐of‐arrival (DOA) estimation method was proposed. By applying the keystone transform, the phase difference caused by different frequency is eliminated, and then the narrowband DOA estimation method can be used directly. Compared with the traditional method, the proposed approach can achieve better estimation accuracy than incoherent subspace method and coherent subspace method at low signal‐to‐noise ratio. The theoretical derivation of the method is given. Monte–Carlo simulations are provided to demonstrate the performance of the proposed scheme.
Generation of unconventional OAM waves by a circular array
Authors: Liu Kang , Cheng Yongqiang , Wang Hongqiang , Qin Yuliang , Wang Zhan
Published: October 2019

In recent years, orbital angular momentum (OAM) waves have been applied to improve the performance of radar target detection and imaging. However, the phase singularity of conventional OAM beams and the doughnut‐shaped intensity distribution will degrade the performance of target detection. To solve the divergence problem in OAM multiplexing systems, the generation method of OAM beams propagating along a transverse plane is proposed using a uniform circular array, which is validated by full‐wave simulation. Compared with conventional OAM beams, simulation results indicate that the generated beams with different OAM modes all propagate along the transverse plane while maintaining the regular wavefront shapes. This work can provide the development of new radar paradigm with technical support.
Radar track prediction method based on BP neural network
Authors: Song Li , Shengli Wang , Dingbao Xie
Published: October 2019

Taking into account the complex electromagnetic environment in which the radar target is located, it is difficult for the traditional track prediction method to adapt for the high complexity, randomness, and uncertainty of the manoeuvring target track. This study proposes a radar track prediction method based on backpropagation (BP) neural network. According to the historical track of the radar target, this method uses BP neural network to model its movement law and obtain the target's predicted track. Finally, the track prediction experiment was conducted with measured data and compared with the Kalman filter track. The results show that the proposed method has higher track prediction accuracy and can be used for radar track prediction.
Target detection approach for DRM‐based passive bistatic radar
Authors: Zhao Zhixin , Zhou Xinhua , Weng Tao , Zhou Xin , Zhang Kaikai
Published: October 2019

This study discussed the problem of target detection for digital radio mondiale (DRM)‐based passive bistatic radar (PBR). In the surveillance signal, the power of zero Doppler contribution (ZDC) is stronger than the echoes of weak targets. These targets can hardly be shown in the range‐Doppler map of classical cross‐ambiguity function (CAF). The clutter should be removed before using CAF‐matched correlator. The authors utilised Doppler channel detector (CHAD) to solve the above problem for DRM‐based PBR in this study. It can unify the ZDC rejection and the target detection in one process. Compared to CAF detector, the CHAD had a lower random pedestal for low Doppler frequency shifts. The results of experiment data proved the effectiveness of the CHAD for DRM‐based PBR.
Recognition of radar active‐jamming through convolutional neural networks
Authors: Wang Yafeng , Sun Boye , Wang Ning
Published: October 2019

Radar application in modern warfare becomes more and more rigorous because of the rapidly developed radar countermeasures, especially active jamming in recent years. It costs a radar many resources for anti‐jamming in order to detect a target. Hence, it is of great value to recognise the active jamming and thereafter take measures to distinguish target from the numerous jamming. Traditional methods of recognition jamming are blamed for its low efficiency and low accuracy. Radar researchers are looking forward to a new way to do the recognition work. Machine learning has made great advancements in many areas such as image classification, language translation, signal processing and many other recognition tasks, due to its great performance and high accuracy. The authors applied a machine learning method, i.e. convolutional neural networks, to recognise active jamming here. The authors’ results demonstrate that convolutional neural networks have strong ability to distinguish active jamming and thus provide them adequate preparation for anti‐jamming process.
CS–MMPF‐based weak target detection and tracking with range ambiguity
Authors: Tan Shuncheng , Wang Guohong , Sun Dianxing , Yu Hongbo
Published: October 2019

To address the problem of target detection and tracking with the range ambiguous radar in low signal‐to‐noise ratio environment, a novel weak target detection and tracking algorithm based on the compressed sensing (CS) and multiple model particle filter (MMPF) is proposed. The general solution is that constructing an over‐complete atom dictionary according to the echo model of target, obtaining a sparse representation of the target echo signal with the CS method, and conducting a threshold detection with the obtained atom energy distribution and judge whether a target is present or not firstly; roughly extracting the ambiguous measurement of weak target by resolving the least square problem constrained by one‐norm minimisation if a target is present then proposing an ambiguous measurement‐based MMPF manoeuvring target tracking method, and realising an effective detection and tracking of manoeuvring weak target in the presence of range measurement ambiguity lastly. Simulation results demonstrate that the proposed method can improve the radar performance of target detection and tracking effectively, and succeeds in range ambiguity resolving.
Adaptive cardinality balanced multi‐target multi‐Bernoulli filter based on cubature Kalman
Authors: Wang Haihuan , Lyu Xiaoyong , Ma Long
Published: October 2019

The sequential Monte Carlo cardinality balanced multi‐Bernoulli (SMC‐CBMeMBer) filter provides a good framework to cope with the multi‐target tracking problem. However, the standard SMC‐CBMeMBer filter suffers from the particles’ degradation problem seriously. Using the measurements to construct the proposal density in the step of predict can effectively solve the above problem, but this kind of approach brings an amount of computation and causes the overestimation of the target number. To examine the quality of each predicted particle adaptively and use the cubature Kalman filter (CKF) to refine the poor‐quality particles with the aid of the current measurements is proposed in this study. This method manages to alleviate the particles degradation problem without increasing the computational complexity seriously since only a part of the particles is refined by the CKF. Also, the proposed method can avoid cardinality overestimation caused by abuse of measurements. A range of simulations is performed to test the performance of the proposed method. The results confirm the effectiveness and robustness of the novel method.
Total least square clutter cancellation in passive radar
Authors: Wang Haihuan , Lyu Xiaoyong , Ma Long
Published: October 2019

In this study, a total least square (TLS) based cancellation method is proposed for suppressing direct and multipath clutter signals in passive radar. The TLS algorithm is first used to estimate the distribution of the clutter signals over delay bins. Then the clutter signal subspace is constructed by delaying the reference signal according to the estimated number and delay bins of the clutter signals. Finally, the surveillance signal is projected into the orthogonal subspace of the clutter space. Compared to the typical extended cancellation algorithm, the proposed method uses a smaller but more accurate order of clutter space, so it can get accurate estimate of the clutter amplitudes by only using a limited length of signals. This indicates the proposed method is with the potential to suppress time‐variant interference where only a small number of signal samples is available.
Radar target classification using improved Dempster–Shafer theory
Authors: Mehta Parth , De Anindita , Shashikiran Dayalan , Ray Kamla Prasan
Published: October 2019

This study considers the problem of coarse classification of targets using multifunction radar. Several methods are available for classification such as decision trees, Dempster–Shafer, Bayes, neural networks, etc. A different approach to assign the mass functions based on fuzzy logic in the Dempster–Shafer framework is proposed in this study. The method is evaluated for classification of different kinds of targets like aircraft, ballistic missiles, satellites, chaff and actual clouds, and unknown targets. With the proposed method, improvement in classification accuracy is observed, compared to existing mass functions. The technique is found to be computationally efficient and suitable for real‐time systems.
Radar emitter intrapulse signal blind sorting under modified wavelet denoising
Authors: Wang Xuebao , Huang Gaoming , Zhou Zhiwen , Tian Wei , Yao Jialun , Gao Jun
Published: October 2019

With the electromagnetic environment becoming more and more complex and the analysis demand of the radar emitter intropulse signal presenting more and more urgent, a modified method of the radar emitter intrapulse signal blind sorting under wavelet denoising is proposed. This study aims to improve the weak adaptability to the noise of the fast independent component analysis (FastICA) algorithm and its blind source separating performance. In this method, a pre‐processing of noise based on the modified wavelet denoising is added. Then the FastICA algorithm is used to sort the unknown radar emitter intrapulse signal for the next intrapulse signal analysis. Simulations and analysis indicate that the modified method improves the signal to noise ratio of the received intermediate signals and the blind sorting performance.
Stochastic configuration network‐based SAR image target classification approach
Authors: Wang Yan P. , Zhang Yi B. , Zhang Yuan , Fan Jun , Qu Hong Q.
Published: October 2019

Synthetic aperture radar (SAR) image interpretation is a great scientific application challenge. The classification of SAR image targets has become one of the main research directions for SAR image interpretation. Therefore, achieving fast and accurate SAR image target classification has always been a research hotspot in this field. Here, the authors propose a classification method based on a regularised stochastic configuration network (SCN), which randomly assigns the input weights and biases with constraint and finds out the output weights all together by solving a global least squares problem. Experimental results on the moving and stationary target acquisition and recognition benchmark dataset illustrate that the regularised SCN classifies ten‐class targets to achieve an accuracy of 94.6%. It is significantly superior to the traditional SCN model and effectively improves the generalisation ability of the network.
BLUE filter with fused range estimation
Authors: Hu Sheng , Wen‐bo Zhao , Si‐yuan Tang
Published: October 2019

The non‐linear filter is subject to divergence for close‐range target tracking; an adaptive best linear unbiased estimation (BLUE) filter with fused range estimation is presented. After proposing the notion of predicted range, the weighted estimation of the predicted and measured ranges is used in the converted measurement model to track the target. The adaptive BLUE filtering parameters with Rayleigh range measurement are derived. Simulation results show the adaptive BLUE filter exhibits better robustness and accuracy with modest computational burden.
Modified reference window for two‐dimensional CFAR in radar target detection
Authors: Wang Weijiang , Wang Runyi , Jiang Rongkun , Yang Hao , Wang Xiaoyu
Published: October 2019

The constant false alarm rate (CFAR) technology plays an important role in radar target detection. In cell averaging CFAR detectors, a reference window is usually adopted to estimate the average interference power in the range–Doppler matrix and to obtain the detection threshold, which should be set high enough to limit false alarm rate to a tolerably small rate. The conventional rectangular window, cross window, and column window are investigated in this study, which may suffer from a degraded detection performance due to involving some extraneous reference cells. Therefore, a modified reference window for two‐dimensional CFAR is proposed to improve performance, depending on the distribution characteristics of radar targets in range and Doppler dimensions. The experimental results demonstrate its performance advantages on detection probability, CFAR loss, and figure of merit.
Research on aperture‐level simultaneous transmit and receive
Authors: Qiu Jian , Yao Yuan , Wu Guangxin
Published: October 2019

This study uses adaptive digital beamforming to provide high isolation between a transmitter and a receiver, which proved effective in achieving simultaneous transmit and receive. Uniform linear array is chosen as the research object, and the cost function is constructed by combining the coupling matrix and beam pointing constraints; then the optimal weighted vector is obtained under the linearly constrained minimum variance rule. The method will provide at least 110 dB isolation without affecting the performance of target detection, which provides certain reference significance in engineering.
FPGA‐based fault injection design for 16K‐point FFT processor
Authors: Mao Chuang‐An , Xie Yu , Wei Xin , Xie Yi‐Zhuang , Chen He
Published: October 2019

There are a number of satellites working in the harsh space environment. The charged particles in space may strike the electron devices causing the undesired influences, such as soft errors in memory devices or permanent damage in hardware circuits. Aiming at reliability evaluation of very‐large‐scale integration circuits implemented in SRAM‐based field programmable gate arrays, a fault injection platform is constructed based on the soft error mitigation controller in this study. The authors adopt a 16K‐point fast Fourier transformation processor as the design under test (DUT) and inject errors into different positions. The effectiveness of this platform is varied by comparing the results of DUT with Golden data. Compared with the traditional reliability testing techniques, the fault injection method proposed in this study has the advantages of low cost, short test period and low resource consumption. Hence, the proposed fault injection design is suitable for circuits consuming huge resources and large number of repeating tests.
DOA estimation for different frequency with different angles based on wideband co‐prime array
Authors: Wang Geng , He Minghao , Tang Yuwen , Feng Mingyue , Han Jun , Fan Xikun
Published: October 2019

Most of the signals received in the field of wireless communication, radar, and sonar are wideband, so there is an active research on wideband direction‐of‐arrival (DOA). Many approaches of DOA estimation for different frequency with same angles have already been proposed, such as off‐grid sparse learning via iterative minimisation (OGSLIM). Based on the OGSLIM algorithm, this study proposed frequency group decision strategy (FGDS). Based on the different information of the number of signals at different frequency bins, FGDS can obtain the estimation results of DOA at each frequency bin. The results of simulations demonstrate that the proposed algorithm outperforms other reported ones.
Robust space‐time adaptive processing based on covariance matrix reconstruction and steering vector correction
Authors: Hu Xueyao , Zhang Xinyu , Li Yang , Wang Hongyu , Wang Yanhua
Published: October 2019

Clutter presents considerable heterogeneity in forward‐looking airborne radar (FLAR) applications and conventional space‐time adaptive processing (STAP) methods are sensitive to model mismatch. As a result, when a strong target signal contaminates the training samples, despite the use of guard cells, the performance of conventional STAP methods degrades significantly. In this study, a robust method, which involves reconstructing a target‐free covariance matrix and correcting the presumed steering vector to prevent target cancellation in FLAR, is proposed. First, the target‐free covariance matrix is reconstructed through integrating the spatial–temporal spectrum over a sector separated from the desired frequency and direction of targets. Subsequently, the mismatch between presumed steering vector and actual steering vector is corrected via quadratic optimisation. In addition, the processing scheme is applied to real‐measured clutter data, and the experimental results validate the effectiveness of the proposed method.
Two‐dimensional deceptive jamming mitigation algorithm for SAR imaging using frequency diverse array
Authors: Lin Chenchen , Huang Puming , Li Yu , Wang Weiwei
Published: October 2019

The synthetic aperture radar (SAR) may be threatened greatly by the deceptive jamming within its main‐lobe. To tackle this problem, a two‐dimensional self‐adaptive frequency diverse array (FDA)‐based SAR processing scheme is proposed in this study. Considering that transmit and receive steering vectors of FDA are range‐angle dependent, in FDA‐SAR, the spectrum distributions of true targets and jamming in joint transmit‐receive frequency domain depends on the actual locations of scattering points and the jammer, respectively. Therefore, the false signal can be distinguished due to the mismatch in either range or angle. Then by employing a two‐dimensional self‐adaptive filter, the phony targets can be mitigated even if the jammer locates in the main beam. In the end, the simulation results showed that it achieves enhanced suppression capability and smaller ineffective area comparing with the static spatial filter in conventional multichannel SAR.
Approximate regularised maximum‐likelihood approach for censoring outliers
Authors: Han Sudan , De Maio Antonio , Pallotta Luca , Carotenuto Vincenzo , Iommelli Salvatore , Huang Xiaotao
Published: October 2019

This study considers censoring outliers in a radar scenario with limited sample support. The problem is formulated as obtaining the regularised maximum likelihood (RML) estimate of the outlier index set. Since the RML estimate involves solving a combinatorial optimisation problem, a reduced complexity but approximate RML (ARML) procedure is also devised. As to the selection of the regularisation parameter, the cross‐validation technique is exploited. At the analysis stage, the performance of the RML/ARML procedure is evaluated based both on simulated and challenging knowledge‐aided sensor signal processing and expert reasoning data, also in comparison with some other outlier excision methods available in the open literature. The numerical results highlight that the RML/ARML algorithm achieves a satisfactory performance level in the presence of limited as well as sufficient sample supports whereas the other counterparts often experience a certain performance degradation for the insufficient training volume.
Long‐time coherent integration for high dynamic DSSS signal
Authors: Wang Fengyu , Yang Jun , Tian Jing , Cui Wei , Xiang Jinzhi
Published: October 2019

A novel coherent integration method for high dynamics direct sequences spread spectrum (DSSS) signal is presented. The presented method is based on adjacent cross‐correlation function (ACCF) and Lv's distribution (LVD). ACCF is firstly used to compensate the code phase drift and reduce the Doppler frequency migration order. After that, LVD is used to accomplish the integration and obtain the parameter estimates. The presented method can estimate motion parameters without any searching procedure. Compared with the existing methods, the presented method can achieve a good balance between the computational cost and the detection and estimation performance. Numerical simulations are provided to verify the effectiveness of the proposed method.
Tracking fluctuating targets in extremely heterogeneous clutter using amplitude information
Authors: Li Feng , Zhuo Bangsheng , Peng Xiangjun , Cheng Miaomiao , Yao Di
Published: October 2019

This study analyses the radar fluctuating target detection in G 0 ‐distributed clutter using dynamic programming – track before detect (DP‐TBD) algorithm. G 0 ‐distributed clutter is often used to fit the complex circumstances. The authors use chi‐square distribution to model the fluctuating targets. The log‐likelihood ratio (LLR) is taken as the scoring function of DP‐TBD. This study makes contribution to simplify the double integral into single integral in LLR and applies numerical integration with variable resolution to evaluating the LLR. Simulations prove the simplified integral equals the original integral and using LLR in DP‐TBD is able to improve the performance of detecting fluctuating targets in G 0 ‐distributed clutter.
Antenna beam angle calibration method via solar electromagnetic radiation scan
Authors: Qi Xiaoyang , Wang Junling , Zhao Lizhi , Ji Jingming
Published: October 2019

Regular calibration is essential to antenna beam‐pointing angle of mobile radar considering system errors caused by the transition to a new site or deformation of the radar antenna structure. Traditional antenna beam‐pointing calibration methods based on calibration towers, aircraft etc. are more widely used. However, these calibration methods are either too complex or too expensive for mobile radar. Since solar has relatively stable radio intensity and its angle of view can be accurately calculated, this study proposed a fast antenna beam pointing calibration method by using solar electromagnetic radiation as a calibration reference. In this method, radar controls its antenna beam pointing to the predicted observing angle of solar and tuning the antenna beam to scan the sun on azimuth and elevation until the amplitude of received radio signal achieved its maximum, then the azimuth and elevation of antenna beam is the value for antenna beam‐pointing calibration. Finally, this study verified the validity of the calibration method by the real calibration data of radar. This method has been applied to a mobile radar with a 0.5° beam width. The results show that the integrated error of the calibration can be <0.01°.
Visual time‐sensitive SAR target detection technology based on human brain mapping
Authors: Yin Kuiying , Li Qixue , Liang Jimin , Liu Chuan , Niu Chang , Wang Zhongbao
Published: October 2019

To detect targets from synthetic aperture radar (SAR) images, this study describes a visual time‐sensitive SAR target detection technology based on human brain mapping. Expert brain central responding messages are introduced into the automatic analysis method of SAR images. A fusing detection model between brain central responding messages and features of SAR targets is built by expert on‐line brain–machine combined modelling. The experimental results show that the technology paper proposed succeeds in automatically detecting and recognising targets of SAR images in actual combat environment, and owns better detection results and higher detection efficiency than DARPA's work. In conclusion, this study proposes an ideal man–machine fusion technology which is worthy of high research value and broad application prospect.
Real‐valued propagator method for fast DOA estimation via polynomial rooting
Authors: Meng Xiang‐Tian , Xue Jing‐Hong , Yan Feng‐Gang , Yan Xue‐Wei
Published: October 2019

In this study, the problem of low‐complexity direction‐of‐arrival (DOA) estimation is addressed, and a novel real‐valued propagator method (PM) is presented with a uniform linear array. The covariance matrix is divided into two subarrays and an equivalent noise subspace is obtained by exploiting the standard PM algorithm without eigenvalue decomposition. By a coordinate mapping technique, the complex PM cost function has been converted into a real‐valued polynomial whose order only rely on the number of arrays. Using such a mathematical fact, source DOAs can be estimated by polynomial rooting instead of peak searching. The proposed method is able to reduce significant complexity with comparable root‐mean‐square error performance to the standard PM, which is finally verified by numerical simulations.
Robust adaptive beamforming method based on desired signal steering vector estimation and interference‐Plus‐noise covariance matrix reconstruction
Authors: Huang Junsheng , Su Hongtao , Yang Yang
Published: October 2019

Here, the authors propose a robust adaptive beamforming method based on desired signal steering vector estimation and interference‐plus‐noise covariance matrix reconstruction, so as to attenuate the influences of the desired signal steering vector mismatch and the limited training snapshots on the performance of adaptive beamformer. More precisely, the desired signal steering vector is estimated by minimising the sine value of the angle between the presumed desired signal steering vector and the eigenvectors of sample covariance matrix. Besides, the sample covariance matrix is reconstructed by reducing the dispersion extent of the noise eigenvalues and eliminating the desired signal component from the sample covariance matrix. The proposed method can not only accelerate the convergence speed of adaptive beamforming algorithm, but also avoid the desired signal cancellation phenomenon when the desired signal is present in the training snapshots. Simulation results demonstrate the superiority of the proposed method.
Method to suppress narrowband interference for OFDM radar
Authors: Wang Xinhai , Zhang Gong , Zhang Yu , Leung Henry , Wen Fangqing
Published: October 2019

Orthogonal frequency division multiplexing which is called OFDM for short is not only a popular modulation technique in communication systems but also a good method to generate radar signals. A joint radar and communication system could be realised by an OFDM system according to some off‐the‐shelf works. The radar functionality is mainly considered here, which requires the system to equip with the ability to suppress interference. The typical radar signal, frequency‐modulated continuous wave, can be viewed as narrowband interference for a large bandwidth OFDM radar with comparably short duration of OFDM symbols. Here, an interference suppression algorithm suitable for any type of narrowband interference is proposed for OFDM radar. The atomic norm minimisation (ANM) method involved in compressed sensing is introduced to obviate the interference. Then, the data with little interference can be reconstructed by reformulating the ANM as a semi‐definite program. Meanwhile, the level of noise is quelled effectively in terms of the atomic norm soft‐thresholding method and the gridless version of SPICE. Finally, the numerical simulation is performed to verify the effectiveness of the proposed method.
Nautical radar clutter suppression and small target detection based on image spectrum filtering and Hough transform
Authors: Bao Zhonghua , Zhang Chunlei , Lu Jianbin
Published: October 2019

Here, a new clutter suppression and small target detection method was presented for nautical radars based on image spectrum filtering and Hough transform (HT). It is well known that sea clutter can be decomposed into texture component (TC) and spiky component (SC). First, the raw echo image was transferred to spectrum field, taking use of the narrow band feature of TC clutter in the image spectrum field, a 2D filter named as invert clutter response filter was designed to filter the energy of TC clutter in image spectrum field and then recovering the echo image. After that, a 2D CFAR detector was used to get a coarse detection report. Since the influence of the remaining SC clutter, quite a lot of false‐alarmed detections may appear for the coarse detections. To solve this problem, the HT technique was proposed to extract real target track lines from many but distributed SC clutter caused false alarms. Measured and simulated results show that the proposed method is quite effective.
DOA estimation with extended sparse and parametric approach in multi‐carrier MIMO HFSWR
Authors: Liu Aihua , Zhang Xin , Yang Qiang , Deng Weibo
Published: October 2019

To obtain a higher angle resolution of multiple‐in multiple‐out high‐frequency surface wave radar (MIMO HFSWR) for direction of arrival (DOA) estimation with a limited number of antenna sensors, multiple working frequencies are proposed to enlarge the aperture of the virtual array of the MIMO HFSWR. The scenario that all targets have the identical reflection at all working frequencies is studied, which permits the abstraction of a virtual received data vector by using all frequencies. This virtual data vector can be taken as the measurement of a virtual non‐uniform linear array (VNLA) with a single reference working frequency. To extend the sparse and parametric approach (SPA) to the VNLA for DOA estimation, the manifold separation technique is utilised to decompose the array steering vector of the VNLA into two different parts, one is a characteristic matrix that is related to the array itself. The other is a Vandermonde vector that contains the DOAs of the targets. Then the authors use the Vandermonde structure to develop a SPA‐liked method for the DOA estimation. Simulation results are provided to confirm the validity of the proposed method.
Adaptive processing method for interference cancellation in sky‐wave OTHR
Authors: Jia Dongdong , Zhang Baiqiang , Xie Junhao
Published: October 2019

An algorithm is proposed to cancel the spatially non‐stationary high‐frequency (HF) interference in the returns of sky‐wave over‐the‐horizon radar (OTHR). The algorithm could suppress the interference in side‐lobe effectively based on spatial adaptive processing. Meanwhile, the algorithm preserves the temporal coherence of the clutter echoes using the zeroth Doppler channel output, of which the clutter‐to‐interference‐plus‐noise ratio is improved, to constraint the weight vectors. The performance results demonstrate the superiority of this algorithm.
Robust adaptive beamforming method for large‐scale array with automatic diagonal loading and steering vector estimation
Authors: Yu Lei , Fan Yanqi , Wei Yinsheng , Xu Rongqing
Published: October 2019

Here, the authors propose a novel robust adaptive beamforming method, which is robust to both of the covariance matrix mismatch and the steering vector estimation mismatch. Their method was based on a recently proposed adaptive beamforming technique for large‐scale arrays. In this beamforming technique, a sparse sub‐array having much smaller number of antenna elements is first selected from the original physical array to perform digital sampling, and then the beamforming coefficients for the original full array are calculated by using only the digital samples from the selected sub‐array. In their robust method, they calculate the diagonal loading level automatically by using the spatial‐matched method. Then, the steering vector of the desired signal is estimated by maximising the beamformer output power under a constraint that the estimated steering vector does not converge to any of the interference steering vectorsor their linear combinations. Numerical examples are provided to demonstrate the effectiveness of the proposed method against covariance matrix mismatch and steering vector error.
Efficient 2D adaptive beamforming algorithm based on sparse array optimisation
Authors: Wang Chaoyu , Zhu Can , Chen Chunlin , Li Hongtao
Published: October 2019

In this study, a 2D adaptive beamforming algorithm for sparse array is proposed. Firstly, a signal model based on matrix completion theory for adaptive beamforming in sparse array is established, which is proved to satisfy null space property. Secondly, in order to enhance the performance of reconstructing complete received signal matrix, genetic algorithm is used to optimise the sparse sampling array. Thirdly, the accelerated proximal gradient algorithm is adopted to reconstruct the complete received signal matrix. Finally, the adaptive beamforming weight is provided directly to form beam patterns, which can be obtained as a result of reconstructing complete received signal matrix. The proposed method could improve the utilisation rate of the sparse array elements and reduce the computational complexity in interference suppression. Simulation results show the effectiveness of the method.
CP‐based OFDM radar–communications signal using interval linear phase compression modulation
Authors: Wang Yuanhang , Zhang Tianxian , Kong Lingjiang , Yang Xiaobo
Published: October 2019

In this study, a signal design algorithm for radar–communications system is investigated. An arbitrary pulse length orthogonal frequency‐division multiplexing with sufficient cyclic prefix (CP‐based OFDM) signal is designed as the radar–communications signal, the communication symbols are embedded by proposing an interval linear phase compression (ILPC) modulation. Firstly, the authors construct the model of CP‐based OFDM signal, and analyse the impact of the communication symbols embedding. Then, to decrease the impact caused by the communication symbols embedding, the ILPC modulation is proposed. To guarantee the performances of the CP‐based OFDM radar–communications signal, a time/frequency domain iterative filtering and clipping method is used. This algorithm can be used to design a CP‐based OFDM signal that has a balanced performance in communications and radar. Finally, numerical results are provided to verify the validity of the proposed algorithm.
Research on sensitivity analysis of wind power consumption capability of integrated energy system based on unified optimal power flow model
Authors: Mu Yongqiang , Wang Chunsheng , Kang Guangyou , Wang Zheng , Jiang Tao , Li Jianfeng , Dou Wenlei
Published: October 2019

A sensitivity analysis method for the wind power capacity of integrated energy systems based on unified optimal power flow is proposed, aiming at the large‐scale grid‐connected wind power problem of integrated energy systems with multiple energy sources and strong coupling characteristics. Based on the unified optimal power flow model of integrated energy system with power system, heat system and gas system, this study establishes the sensitivity analysis method of integrated energy system operation state. Based on the sensitivity matrix, the influence of wind power consumption capability by capacity of energy coupling unit on wind power consumption is analysed. The results of the example show that the proposed method can provide auxiliary information for the safe and stable operation of the integrated energy system, and effectively improve the wind power acceptance level.
High‐resolution SAR altimeter with wide‐angle echoes coherent accumulation
Authors: Tang Weijie , Zhang Zenghui , Yu Wenxian
Published: October 2019

Wide‐angle synthetic aperture radar (SAR) altimeters, which are able to obtain higher azimuth resolution and better height measurement result, demonstrate a promising prospect of application. Accumulating scattering echoes received from different angles can greatly suppress noise and promote estimation accuracy. However, traditional methods of accumulation cannot work well in wide‐angle SAR altimeters due to variety of scattering characteristics. To address this problem, this study first researches on basic principles, scattering function and signal models of wide‐angle SAR altimeters. Based on these models, echoes of various angles are coherent accumulated to estimate the parameters. A cylindrical target on the sea surface is used as an example in the simulation. The results indicate that the precision of parameter estimation is improved by two to four orders of magnitude if the scattering characteristics varying with azimuth angles are taken into account in the step of echoes accumulation.
Micro‐Doppler signature for drone detection using FSR: a theoretical and experimental validation
Authors: Musa Surajo Alhaji , Raja Syamsul Azmir Raja Abdullah , Sali Aduwati , Ismail Alyani , Abd Rashid Nur Emileen
Published: October 2019

Drone inexpensive and operational flexibility contributed to its exponential increase by civil users, apart from military applications. This resulted in posing threats due to drone misuses, such as smuggling, unlawful imaging and other significant vulnerability that makes its detection necessary. The study demonstrated a theoretical model of extracting the m ‐Doppler signature due to rotating blades of a quadcopter drone, in forward scattering radar (FSR) geometry. The model was further validated experimentally by using a parabolic dish antenna in the receiver system of the FSR geometry. Before these, some reported efforts made to detect the drone by using different methodologies such as acoustic, video, audio‐visual, radio frequency, radar systems and other non‐technical approaches like netting were briefly presented. The result of the authors’ investigation revealed that the drone could be detected from the signature generated due to rotating blades based on the blade orientation. This signature can further be used to identify the drone from other flying targets existing within the same surveillance area.
Target moving trajectory estimation by multiple receivers based on GPS forward scattering radar
Authors: Gao Chaoqun , Yang Dongkai , Wang Bo , Zhu Yunlong
Published: October 2019

The estimation of target moving trajectory by the multiple receivers based on global positioning system (GPS) forward scattering radar has been first presented in the study, which cannot be obtained by the traditional method. A new estimation approach has been considered using the following information. First, the starting and ending time at which the target pass through the baseline of GPS transmitter–receiver can be obtained. Second, the azimuth and elevation angles of GPS satellites are extracted in combination with the satellite sky map at the recording time. On the basis, the target moving trajectory can be obtained by the established model. In order to validate its feasibility, the experiment has been completed in the open area of Beihang University, which regards the human as the target. Four GPS receivers have been employed to record the data. The experimental results show that the estimation of target trajectory is consistent with the real situation, which proves the practical applicability of the proposed technique.
Enhanced off‐grid DOA estimation by corrected power Bayesian inference using difference coarray
Authors: Ma Yanan , Cao Xianbin , Wang Xiangrong
Published: October 2019

Sparse Bayesian inference for on‐grid direction‐of‐arrival (DOA) estimation using difference coarray was investigated in the authors’ previous work to estimate more signal sources than the number of physical antenna elements. Sparse Bayesian inference is derived based on a linear inverse model and the DOAs of incident signals are indicated by the sparse support of the power spectrum for a predefined dictionary. Thus, the DOA estimation accuracy of Bayesian inference is limited by the accuracy of power estimation. An enhanced off‐grid DOA estimation algorithm by combining coarray Bayesian inference with power correction is proposed in this study. Simulation results show that the additional step of corrected power increases the DOA estimation accuracy significantly.
Performance analysis of one‐step prediction‐based cognitive jamming in jammer‐radar countermeasure model
Authors: Gao Lu , Liu Li , Cao Yang , Wang Shangyue , You Shixun
Published: October 2019

Strong adaptive radar, such as cognitive radar (CNR), can perform various missions while ensuring its own security in electronic warfare, via detecting environments and changing the radar parameters in real time. Unfortunately, most of the current military countermeasures, such as jamming‐based electronic countermeasures, have rarely been related to jamming for CNR. Since the behaviours of radar in the traditional design of the jammer‐radar scenario are always static, it is easy to create a subjective or local optimal jamming effect. In order to dynamically analyse the execution process of a complete jamming radar mission, this work establishes an equivalent attack‐defence game in which the radar is regarded as a defence decision agent, and the jammer is an attack decision agent. The attributes of the game's players, the rules of the game, and the conditions for the end of the game are set clearly by setting reasonable parameters. After searching for antagonism strategies by exhaustive method, it can be found that the survivability of the predictive cognitive jamming is much stronger than that of the normal jamming based on real‐time sampling data of radars. This conclusion is demonstrated through a 1 ms simulation of the game process.
Organic‐free indium‐doped cesium lead iodide perovskite for solar cell application
Authors: Murugadoss Govindhasamy , Thangamuthu Rangasamy , Rajesh Kumar Manavalan , Ravishankar Ramamoorthy
Published: October 2019

Herein, organic‐free all‐solid‐state based perovskite solar cells (PSCs) are successfully fabricated by one‐step method. The absorption position of the non‐perovskite cesium lead iodide (δ‐CsPbI3) was significantly shifted towards longer wavelength side by substituting indium (In) ion with different stoichiometric ratio. The authors demonstrated a facile route to achieve high efficiency by the fabrication of room temperature stable mixed‐phase CsPbI3 perovskite. Photovoltaic efficiency of doped perovskite is four times increased compared to pure yellow phase CsPbI3. To the best of the authors’ knowledge, this is the first demonstration of In‐doped‐CsPbI3 based PSCs, which was fabricated under completely open‐air atmosphere.
High-efficiency continuous casting of GCr15 bearing steel bloom based on cooperative control technique of complex electromagnetic stirring and soft reduction
Authors: An Hanghang , Bao Yan Ping , Wang Min , Yang Quan , Wang Xiang Hong , Dang Yan Yin
Published: October 2019

GCr15 bearing steel exhibits comparatively serious center macro-segregation in the continuous casting of bloom with the increase of casting speed. In the present work, the influence of complex electromagnetic stirring (M + F-EMS) and mechanical soft reduction (MSR) on the center macro-segregation in the continuous casting of 220 × 260 mm blooms of GCr15 bearing steel have been comparatively investigated to increase casting speed in order to ensure a good internal quality. Based on numerical simulation and experiments, M + F-EMS and MSR have been comprehensively evaluated and compared by combination of industrial trials. The results show that center carbon segregation first decreases and then increases with the increase of casting speed in both processes without optimization. For M + F-EMS process, when casting speed increases from 0.75 to 0.85 m · min−1, the average degree of center carbon segregation decreases from 1.2 ∼ 1.26 to 1.18 ∼ 1.25 by asymmetrical optimization; with regard to combination of M + F-EMS and MSR process, when casting speed increases from 0.75 to 0.9 m · min−1, the average degree of center carbon segregation decreases from 1.2 ∼ 1.26 to 1.08 ∼ 1.1 and the solute element distribution becomes homogeneous by optimization. In comparison, significant reduction of the center macro-segregation with the increase of casting speed can be achieved for combination of M + F-EMS and MSR process, however, it is infeasible for M + F-EMS process in the present technology situation.
Intensivmedizin bei älteren Patienten – Berücksichtigung von altersbedingter Organdysfunktion und Vulnerabilität
Authors: Michels Guido , Müller-Werdan Ursula
Published: October 2019

Was ist neu?

Altersphysiologische Organ- bzw. Organsystemveränderungen Alle Organe des Menschen durchlaufen eine altersbedingte Funktionseinschränkung bzw. einen Alterungsprozess. So bleiben Herz, Lunge, Nieren, Gastrointestinaltrakt, Hormon- und Immunsystem und v. a. dem Gehirn geringere physiologische Reserven, um gegenüber Noxen oder abweichenden Bedingungen ihre Funktion erhalten zu können. Bei intensivpflichtigen Patienten stellt v. a. ein Delir einen prognostisch ungünstigen Faktor dar. Umso wichtiger ist hier ein effektives Management.

Altersbedingte Vulnerabilität Nicht das Lebensalter allein wirkt sich auf die vergleichsweise erhöhte Sterblichkeit bei älteren Patienten aus. Zu den entscheidenden Vulnerabilitätsfaktoren zählen auch v. a. die Gebrechlichkeit, der Ernährungszustand, die kognitive Funktion sowie die Schwere der aktuellen Krankheit und Komorbiditäten.

Begrenzung des Therapieziels Den immer größeren technischen Möglichkeiten der Medizin stehen oft die ethischen Forderungen entgegen: Respekt vor Autonomie, Nicht-Schaden, Fürsorge, Gerechtigkeit. Entscheidend ist schließlich der Patientenwille, auch wenn es oft eine Herausforderung darstellt, diesen bestimmen und befolgen zu können.
Stereoselective Preparation and Reactions of Chiral Secondary Alkyllithiums
Authors: Skotnitzki Juri , Kremsmair Alexander , Knochel Paul
Published: October 2019

The preparation of chiral non-stabilized open-chain alkyl­lithium reagents prepared from the corresponding chiral secondary alkyl iodides and their subsequent transmetalation to the corresponding secondary alkylcopper or alkylzinc derivatives is reviewed. These new organometallic reagents allow the stereoselective preparation of a broad range of chiral molecules.

1 Introduction

2 Stereoselective Preparation of Secondary Alkyllithiums

3 Preparation of Stereodefined Secondary Alkylcopper Reagents

4 Preparation of Stereodefined Secondary Alkylzinc Derivatives and Their Stereoselective Cross-Coupling with Alkenyl and Aryl Halides­

5 Conclusion
Effect of combining local velocity and chemical reaction on the interaction between diffusion and stresses in large deformed electrodes
Authors: Xu Yongchuan , Zheng Bailin , Zhang Kai , Peng Yingzha , Wang Feng
Published: October 2019

A general framework to study the effects of chemical reaction, local deformation velocity and their interaction on the two-way coupling between stress and Li diffusion in a spherical silicon electrode under galvanostatic operation is presented in this work. The reversible chemical theory is adopted as a start up to obtain the reaction equation and the influence of local deformation velocity on the flux is taken into consideration. This is such a complex problem that an analytical solution can hardly be found. Therefore, a numerical method is subsequently used to solve the derived coupled partial differential equations (PDEs) in nonlinear elasticity with finite deformation to analyze the diffusion-induced stress (DIS) in the electrode. The numerical results of lithium concentration, radial stress and hoop stress suggest that in comparison with the local deformation velocity, the reversible chemical reaction plays a much more significant role in altering the distribution of DIS and Li concentration. The local deformation could raise the concentration gradient and result in larger magnitude of DIS, while the chemical reaction could hinder the diffusion process as well as the swelling of the electrode material. It is also observed that the local deformation could promote the chemical reaction near the surface of the electrode but retard it in the core. Furthermore, the effects of the current density are also discussed. For a smaller lithiation rate, the interaction between chemical reaction and local deformation has a tendency of decreasing, which could have significant contribution to enhance the stability level and the cycle performance of lithium-ion batteries.