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Beamspace maximum likelihood algorithm based on sum and difference beams for elevation estimation

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Journal of Systems Engineering and electronics 2024年第3期35卷 589-598页

作者： CHEN Sheng ZHAO Yongbo HU Yili PANG Xiaojiao National laboratory of Radar signal processing Xidian UniversityXi’an 710071China

Beamspace super-resolution methods for elevation estimation in multipath environment has attracted significant attention, especially the beamspace maximum likelihood(BML)algorithm. However, the difference beam is rarely used in superresolution methods, especially in low elevation estimation. The target airspace information in the difference beam is different from the target airspace information in the sum beam. And the use of difference beams does not significantly increase the complexity of the system and algorithms. Thus, this paper applies the difference beam to the beamformer to improve the elevation estimation performance of BML algorithm. And the direction and number of beams can be adjusted according to the actual needs. The theoretical target elevation angle root means square error(RMSE) and the computational complexity of the proposed algorithms are analyzed. Finally, computer simulations and real data processing results demonstrate the effectiveness of the proposed algorithms.

关键词： elevation estimation beamspace multipath environment maximum likelihood

Interference mitigation and target detection for automotive FMCW radar with range-Doppler sparse regularization

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Science China(Information Sciences) 2024年第9期67卷 342-343页

作者： Yan HUANG Yunxuan WANG Xiao ZHOU Hui ZHANG Yuan MAO Guisheng LIAO Wei HONG State Key lab of Millimeter Waves Southeast University Department of Computer Science University College London National Key lab of Radar signal processing Xidian University

The invention of vehicles has shaped our modern society and accelerated our economy while causing many tragic incidents simultaneously. Some advanced driver-assistance systems(ADAS) based on surrounding environment se... 详细信息

关键词： Radar interference

A robust vector tracking loop structure based on potential bias analysis

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Chinese Journal of Aeronautics 2024年第4期37卷 405-420页

作者： Qiongqiong JIA Yiran LUO Bing XU Li-Ta HSU Renbiao WU Tianjin Key lab for Advanced signal processing Civil Aviation University of ChinaTianjin 300300China Interdisciplinary Division of Aeronautical and Aviation Engineering The Hong Kong Polytechnic University999077Hong KongChina Department of Geomatics Engineering University of CalgaryCalgary T2N1N4Canada

This paper proposes a robust vector tracking loop structure based on potential bias analysis. The influence of four kinds of biases on the existing two implementations of Vector Tracking Loops(VTLs) is illustrated by theoretical analysis and numerical simulations, and the following findings are obtained. Firstly, the initial user state bias leads to steady navigation solution bias in the relative VTL, while new measurements can eliminate it in the absolute VTL. Secondly, the initial code phase bias is transferred to the following navigation solutions in the relative VTL, while new measurements can eliminate it in the absolute VTL. Thirdly, the user state bias induced by erroneous navigation solution of VTLs can be eliminated by both of the two VTLs. Fourthly,the multipath/NLOS likely affects the two VTLs, and the induced tracking bias in the duration of the multipath/NLOS would decrease the performance of VTLs. Based on the above analysis,a robust VTL structure is proposed, where the absolute VTL is selected for its robustness to the two kinds of initialization biases;meanwhile, the instant bias detection and correction method is used to improve the performance of VTLs in the duration of the multipath/NLOS. Numerical simulations and experimental results verify the effectiveness of the proposed robust VTL structure.

关键词： Global Navigation Satellite System(GNSS) Vector Tracking Loop(VTL) Multipath Non-Line-of-Sight(NLOS) Tracking bias propagation Least Absolute Shrinkage and Selection Operator(LASSO)

Properties of focused Laguerre–Gaussian beam propagating in anisotropic ocean turbulence

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Chinese Physics B 2024年第2期33卷 386-393页

作者：王新光马洋斌袁邱杰陈伟王乐赵生妹 College of Science Nanjing University of Posts and TelecommunicationsNanjing 210003China Institute of signal processing and Transmission Nanjing University of Posts and TelecommunicationsNanjing 210003China Key lab of Broadband Wireless Communication and Sensor Network Technology(Ministry of Education) Nanjing University of Posts and TelecommunicationsNanjing 210003China National laboratory of Solid State Microstructures Nanjing UniversityNanjing 210093China

We analyze the properties of a focused Laguerre–Gaussian(LG)beam propagating through anisotropic ocean turbulence based on the Huygens–Fresnel *** the Rytov approximation theory,we derive the analytical formula of the channel capacity of the focused LG beam in the anisotropic ocean turbulence,and analyze the relationship between the capacity and the light source parameters as well as the turbulent ocean *** is found that the focusing mirror can greatly enhance the channel capacity of the system at the geometric focal plane in oceanic *** results also demonstrate that the communication link can obtain high channel capacity by adopting longer beam wavelength,greater initial beam waist radius,and larger number of transmission ***,the capacity of the system increases with the decrease of the mean squared temperature dissipation rate,temperature-salinity contribution ratio and turbulence outer scale factor,and with the increase of the kinetic energy dissipation rate per unit mass of fluid,turbulence inner scale factor and anisotropy *** to a Hankel–Bessel beam with diffraction-free characteristics and unfocused LG beam,the focused LG beam shows superior anti-turbulence interference properties,which provide a theoretical reference for research and development of underwater optical communication links using focused LG beams.

关键词： vortex beam orbital angular momentum focusing mirror anisotropic turbulence

Persymmetric adaptive polarimetric detection of subspace range-spread targets in compound Gaussian sea clutter

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Journal of Systems Engineering and electronics 2024年第1期35卷 31-42页

作者： XU Shuwen HAO Yifan WANG Zhuo XUE Jian National Key laboratory of Radar signal processing Xidian UniversityXi’an 710071China Xi’an Electronic Engineering Research Institute Xi’an 710100China Beijing Institute of Radio Measurement Beijing 100039China School of Communications and Information Engineering Xi’an University of Posts and TelecommunicationsXi’an 710121China

This paper focuses on the adaptive detection of range and Doppler dual-spread targets in non-homogeneous and nonGaussian sea *** sea clutter from two polarimetric channels is modeled as a compound-Gaussian model with different parameters,and the target is modeled as a subspace rangespread target *** persymmetric structure is used to model the clutter covariance matrix,in order to reduce the reliance on secondary data of the designed *** adaptive polarimetric persymmetric detectors are designed based on the generalized likelihood ratio test(GLRT),Rao test,and Wald *** the proposed detectors have constant falsealarm rate property with respect to the clutter texture,the speckle covariance *** results on simulated and measured data show that three adaptive detectors outperform the competitors in different clutter environments,and the proposed GLRT detector has the best detection performance under different parameters.

关键词： sea clutter adaptive polarimetric detection compound Gaussian model subspace range-spread target persymmetric structure

Long-term ultrastable frequency dissemination via a 50-km spooled fiber link using a two-section DFB laser

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Chinese Optics Letters 2024年第1期22卷 164-169页

作者：尹知谦张川博管世健周昕王亚光王磊磊郑满航刘奕彤张云山朱兴邦方涛陈向飞 Engineering Research Center of Precision Photonics Integration and System Application Ministry of Education&Key Laboratory of Intelligent Optical Sensing and ManipulationMinistry of Education&National Laboratory of Solid State Microstructures&College of Engineering and Applied Sciences&Institute of Optical Communication Engineering&Nanjing University-Tongding Joint Lab for Large-Scale Photonic Integrated CircuitsNanjing UniversityNanjing 210023China College of electronics and Optical Engineering and College of Flexible electronics Nanjing University of Posts and TelecommunicationsNanjing 210023China The 41st Research Institute of China electronics Technology Group Corp Qingdao 266000China

The stable long-distance transmission of radio-frequency(RF)signals holds significant importance from various aspects,including the comparison of optical frequency standards,remote monitoring and control,scientific research and experiments,and RF spectrum *** demonstrate a scheme where an ultrastable frequency signal was transmitted over a 50 km coiled *** optical RF signal is generated using a two-section distributed feedback(DFB)laser for direct modulation based on the reconstruction equivalent chirp(REC)*** 3-dB modulation bandwidth of the two-section DFB laser is 18 GHz and the residual phase noise of-122.87 dBc/Hz is achieved at 10-Hz offset *** report a short-term stability of 1.62×10^(-14)at an average time of 1 s and a long-term stability of 6.55×10^(-18)at the measurement time of 62,000 s when applying current to the front section of the DFB *** applying power to both sections,the stability of the system improves to 4.42×10^(-18)within a testing period of 56,737 *** applying temperature variations to the transmission link,long-term stability of 8.63×10^(-18)at 23.9 h can still be achieved.

关键词： frequency dissemination two-section DFB laser phase stability

MXene Enhanced 3D Needled Waste Denim Felt for High‑Performance Flexible Supercapacitors

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Nano-Micro Letters 2024年第2期16卷 383-394页

作者： Wei Fan Qi Wang Kai Rong Yang Shi Wanxi Peng Handong Li Zhanhu Guo Ben Bin Xu Hua Hou Hassan Algadi Shengbo Ge Key laboratory of Functional Textile Material and Product of the Ministry of Education School of Textile Science and EngineeringInstitute of Flexible electronics and Intelligent TextileXi’an Polytechnic UniversityXi’an 710048People’s Republic of China Co‑Innovation Center of Efficient processing and Utilization of Forest Resources College of Materials Science and EngineeringNanjing Forestry UniversityNanjing 210037People’s Republic of China Henan Province International Collaboration lab of Forest Resources Utilization School of ForestryHenan Agricultural UniversityZhengzhou 450002People’s Republic of China Integrated Composites lab Department of Mechanical and Construction EngineeringNorthumbria UniversityNewcastle Upon Tyne NE18STUK College of Materials Science and Engineering Taiyuan University of Science and TechnologyTaiyuan 030024People’s Republic of China Department of Electrical Engineering Faculty of EngineeringNajran University11001 NajranSaudi Arabia

MXene,a transition metal carbide/nitride,has been prominent as an ideal electrochemical active material for ***,the low MXene load limits its practical *** environmental concerns and sustainable development become more widely recognized,it is necessary to explore a greener and cleaner technology to recycle textile by-products such as *** present study proposes an effective 3D fabrication method that uses MXene to fabricate waste denim felt into ultralight and flexible supercapacitors through needling and *** 3D structure provided more sites for loading MXene onto Z-directional fiber bundles,resulting in more efficient ion exchange between the electrolyte and ***,the carbonization process removed the specific adverse groups in MXenes,further improving the specific capacitance,energy density,power density and electrical conductivity of *** electrodes achieve a maximum specific capacitance of 1748.5 mF cm-2 and demonstrate remarkable cycling stability maintaining more than 94%after 15,000 galvanostatic charge/discharge ***,the obtained supercapacitors present a maximum specific capacitance of 577.5 mF cm^(-2),energy density of 80.2μWh cm^(-2)and power density of 3 mW cm^(-2),*** resulting supercapacitors can be used to develop smart wearable power devices such as smartwatches,laying the foundation for a novel strategy of utilizing waste cotton in a high-quality manner.

关键词： MXene 3D needled waste denim felt Supercapacitors Carbonization

Stability-enhanced RF signal transmission over long fiber-optic links

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Chinese Optics Letters 2024年第5期22卷 131-136页

作者：尹知谦郑满航张川博管世健周昕刘奕彤刚泽宇聂佳强张云山朱兴邦方涛陈向飞 Engineering Research Center of Precision Photonics Integration and System Application Ministry of Education&Key Laboratory of Intelligent Optical Sensing and ManipulationMinistry of Education&National Laboratory of Solid State Microstructures&College of Engineering and Applied Sciences&Institute of Optical Communication Engineering&Nanjing University-Tongding Joint Lab for Large-scale Photonic Integrated CircuitsNanjing UniversityNanjing 210023China College of electronics and Optical Engineering and College of Flexible electronics(Future Technology) Nanjing University of Posts and TelecommunicationsNanjing 210023China The 41st Research Institute of China electronics Technology Group Corp Qingdao 266000China

We propose a method for optimizing the phase stability of microwave signal transmission over long ***,the design of the photon link was modified to reduce the radio frequency(RF)signal’s baseline noise and increase ***,a low-noise driver circuit was developed for a two-section distributed feedback(DFB)laser designed using reconstruction equivalent chirp(REC)technology to create an ultra-stable laser,and its performance was characterized through linewidth *** results indicate that the DFB laser achieved narrower linewidth,improving system phase *** an injection current(30 mA)is applied to the reflection section of the two-section DFB laser,the laser linewidth will be narrower(1.38 MHz),further enhancing the system’s phase transmission *** a 1 Hz offset frequency,a residual phase noise of-88.65 dBc/Hz is *** short-term stability with an averaging time of 1 s is 1.60×10^(-14),and the long-term stability over a testing time of 60,000 s is 3.41×10^(-18).Even after incorporating temperature variations,the long-term stability reaches 8.37×10^(-18) at 22 h.

关键词： frequency dissemination two-section distributed feedback laser phase stability

Off-grid DOA estimation via a deep learning framework

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Science China(Information Sciences) 2023年第12期66卷 222-237页

作者： Yan HUANG Yanjun ZHANG Jun TAO Cai WEN Guisheng LIAO Wei HONG State Key lab of Millimeter Waves Southeast University Key laboratory of Underwater Acoustic signal processing of Ministry of Education Southeast University School of Information Science and Technology Northwest University National Key lab of Radar signal processing Xidian University

Direction-of-arrival(DOA) estimation problem is one of the most important tasks for array signal processing. Conventional methods are limited by either the computational complexity or the resolution. In this paper, a novel deep learning(DL) framework for super-resolution DOA estimation is developed, where the grid mismatch problem is fully considered into the DL DOA estimation and the offset between the real DOA and the discrete sampling grid is thereby trained as a part of the network output. Specifically, we first model the DOA estimation problem as a multi-classification task and obtain the on-grid estimation result with a resolution of 1° as the first output. Then we designed another regression module to estimate the offset between target angles and the corresponding grids. By combining both on-grid and offset estimation results, the accurate off-grid estimation is achieved. In addition, the method of fusing low-level features and high-level features by skip connection is adopted between the on-grid estimation module and the offset estimation module. The high-level features in the first part of the network are combined with the original input to improve the training speed and the estimation accuracy. Herein, our training dataset contains a large number of off-grid signal data, which is close to the practical application. Also, the utilization of the off-grid part information improves DOA estimation performance compared to existing DL-based methods,achieving more accurate DOA estimations. Numerous simulation results have demonstrated the superiority of the proposed method in DOA estimation precision, and a good performance advantage maintains even when using a limited number of snapshots. Further, we test the proposed method on the real millimeter-wave radar system, and it outperforms the other state-of-the-art methods, especially for two adjacent targets in the same range and Doppler bin.

关键词： direction-of-arrival (DOA) estimation deep learning (DL) off-grid array signal processing