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SSRN 2023年

作者： Jia, Qiongqiong Wu, Renbiao Tianjin Key Lab for Advanced Signal Processing Civil Aviation University of China Tianjin300300 China

The vector tracking loop (VTL), where the internal aiding is achieved with multi-channel information sharing, is generally superior to the traditional scalar tracking loop (STL). Multipath effect on the VTL is illustrated and theoretical models of multipath induced tracking bias to the VTL, for both the coherent and non-coherent discriminators, are established. Correctness of the established models are validated by numerical simulations. It is revealed that the multipath induced tracking bias to the VTL is dependent on the code phase offset, which is originated from its internal aiding nature. Conclusions are drawn based on the established models: multipath induced tracking bias to the VTL is not greater than it to the STL in constructive multipath case, while in destructive multipath case, the bias envelop of VTL is not superior to STL. We finally define the positive and negative maximum biases as the maximum VTL bias envelop to stand for the worst case performance. Abnormal phenomenon appears in the maximum VTL bias envelop is also analyzed in detail, with the conclusion that the discriminate curve distortion becomes more severe as the correlator spacing and the relative amplitude of the multipath signal increase. © 2023, The Authors. All rights reserved.

关键词： Global positioning system

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Improving Integrality of Detected Moving Objects Based on Image Matting

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Chinese Journal of Electronics 2025年第4期23卷 742-746页

作者： Liang Zhang Haili Wang Tao Deng Xiaomei He Tianjin Key Lab for Advanced Signal Processing Civil Aviation University of China Tianjin China Training Center of Engineering Technology Civil Aviation University of China Tianjin China

The integrality of moving objects is the basis for video-based object tracking and action analysis. But it often becomes unreliable as a result of shadow elimination when the object has similar properties with real shadow. The proposed methods manage to improve the integrality of detected moving objects as much as possible, by image matting operated on candidate shadow regions. Existing approaches for image matting require manual labeling of foreground and background. Considering the moving feature points in shadow may cause classification errors, we propose automatic scribbling methods based on Scale invariant feature transform (SIFT) and Speeded-up robust feature (SURF) respectively. Experiments demonstrate that our methods eliminate real shadow effectively and improve object segmentation in the case of object parts and shadows presenting similar characteristics.

关键词： Object segmentation Transforms Manuals Object tracking labeling

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Navigation domain multipath characterization using GNSS direct position estimation in urban canyon environment 35

Navigation domain multipath characterization using GNSS dire...

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35th International Technical Meeting of the Satellite Division of the Institute of Navigation, ION GNSS+ 2022

作者： Huang, Jihong Sun, Rui Yang, Rong Zhan, Xingqun Chen, Wantong School of Aeronautics and Astronautics Shanghai Jiao Tong University Shanghai China Tianjin Key Lab for Advanced Signal Processing Civil Aviation University of China Tianjin China

ISBN: (纸本)9781713871361

Multipath is a common factor that degrade the performance of Global Navigation Satellite System (GNSS), especially in urban canyon and indoor environments. Due to the reflection of surrounding buildings, multiple Non-Line of Sight (NLOS) signals will arrive receiver antenna with various paths, and the Line of Sight (LOS) signals parameters such as the amplitude and phase will suffer significant distortions and fluctuation. However, due to the random feature of temporal, spatial and frequency diversity across the signal bands, it is difficult to accurately characterize the multipath effect. In this paper, a new attempt has been made to characterize the multipath fading in navigation domain using GNSS direct position estimation (DPE) algorithm. Live tests were conducted in viaduct and urban environments in Shanghai with both traditional two-step and DPE algorithm. The results show the robust of DPE no matter the receiver is moving or static. And the navigation domain manifolds for viaduct and urban scenarios are compared to characterize the multipath fading. The results demonstrate the feasibility of navigation domain multipath characterization using GNSS direct position estimation in urban canyon environment. © 2022 by Institute of Navigation. All rights reserved.

关键词： Navigation

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Speech Recognition Model of Civil Aviation Radiotelephony Communication Based on Improved Conformer

Speech Recognition Model of Civil Aviation Radiotelephony Co...

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2022 International Conference on Automation, Robotics and Computer Engineering, ICARCE 2022

作者： Xiao, Zewei Jia, Guimin Shi, Bo Civil Aviation University of China Tianjin Key Lab for Advanced Signal Processing China Civil Aviation University of China College of Electronic Information and Automation Tianjin China

ISBN: (纸本)9781665475488

Radiotelephony communication has a special grammatical structure and pronunciation, and it is difficult to apply the model of generic speech recognition directly to the field of radiotelephony communication. We propose a Conv1DSlide-Conformer model for speech recognition of radiotelephony communication. The sliding-window attention mechanism is used instead of the self-attention mechanism to improve the decoding speed of the model and increase the adaptability of the model to radiotelephony communication. The convolutional module is used instead of the feedforward neural network module to make the encoder focus more on local information. The improved Conformer model processes the FBANK features of radiotelephony communication and can extract high-dimensional features that better fit the characteristics of radiotelephony communication. The use of concatenated temporal classification (CTC) combined with a data augmentation strategy assists training to speed up convergence during model training and reduce the complexity of model training. Decoding is assisted by CTC and language models to improve the performance of speech recognition. The experimental results show that the improved Conformer speech recognition model in this paper reduces the word error rate to 8.1% and 7.8% on the actual Chinese radiotelephony communication speech dataset. © 2022 IEEE.

关键词： Radio telephone

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Clutter Suppression of Wind Farm for Airborne Radar Based on EFA

Clutter Suppression of Wind Farm for Airborne Radar Based on...

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2021 CIE International Conference on Radar, Radar 2021

作者： Zhang, Ying Zhang, Xinyun He, Weikun Wang, Xiaoliang Civil Aviation University of China Tianjin Key Lab for Advanced Signal Processing Tianjin China

ISBN: (纸本)9781665498142

With the rapid development of wind power generation, the clutter generated by wind farms may lead to the problems such as decreased detection probability, increased false alarm rate, and target track divergence. Research on the wind farm clutter mitigation technology for airborne radar is vital. Considering the special problems of the wind farm clutter mitigation for airborne radar, such as the less prior information and the more complicated spectrum of the echoes, it is difficult to suppress the wind farm clutter with non-Gaussian and dynamic characteristics. In this paper, the extended factored approach (EFA) algorithm is used to suppress the wind farm clutter through space-time adaptive processing of airborne array radar echoes. The EFA algorithm does not need the prior information of wind farm clutter or a large number of training data and can adaptively form null with a certain width in the Doppler domain. The null is used to suppress the wind farm clutter, which can avoid the interference of the wind farm clutter on the detection of aircraft targets and improve the detection probability of airborne radar. The experiment results verify the effectiveness of the proposed method. © 2021 IEEE.

关键词： airborne radar clutter suppression extended factored approach wind farms

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Wind Field Inversion and Reconstruction Based on ADS-B Data 3

Wind Field Inversion and Reconstruction Based on ADS-B Data

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3rd IEEE International Conference on Civil Aviation Safety and Information Technology, ICCASIT 2021

作者： Xiaoyun, Shen Zixuan, Zhao Siyuan, Zhang Weidong, Jiao Chong, Ma Tianying, Wang Tianjin Key Lab for Advanced Signal and Image Processing Civil Aviation University of China Tianjin China

ISBN: (纸本)9781665425186

To accurately perceive sudden airflow changes during flight and avoid aviation safety risks caused by sudden weather at high altitudes, it is necessary to invert and reconstruct the wind field during flight. Based on the random sample consensus estimation, the improved Least Squares algorithm is used to fit the Automatic Dependent Surveillance-Broadcast (ADS-B) data. Firstly, the vertical wind profile is constructed by inverting the wind vectors at different altitude levels at the fixed airport location and compared with the meteorological data of the European Center for Medium-Range Weather Forecasts (ECMWF) to verify the feasibility and accuracy of the algorithm. Then, the wind field under the complete track of a specific flight is reconstructed to obtain the wind field distribution along the route. Finally, regional wind fields at different altitudes are reconstructed using multiaircraft data in a fixed range. The experimental results show that this method can better reflect the real complex wind field structure. © 2021 IEEE

关键词： Weather forecasting

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Track prediction algorithm based on GA-BPNN 3

Track prediction algorithm based on GA-BPNN

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3rd IEEE International Conference on Civil Aviation Safety and Information Technology, ICCASIT 2021

作者： Jiao, Weidong Ma, Chong Tianjin Key Lab for Advanced Signal and Image Processing Civil Aviation University of China Tianjin China

ISBN: (纸本)9781665425186

A track prediction algorithm is proposed based on the Genetic Algorithm (GA) and Back Propagation neural network (BPNN), in which the GA is used to optimize the initial weights and thresholds of hidden layers of the network. Firstly, a 5-5-4 topology of the BPNN for track prediction is established according to the characteristics of track prediction. Its inputs are historical tracks, and the output just is the predicted track. Secondly, the weights and thresholds of the BPNN are regarded as genes of individual in GA to construct chromosomes, individuals, and populations. Then, the optimal solution of the GA is used as the weights and thresholds of the BPNN for network training to get a better output. In the experiment, the track data are derived from Automatic Dependent Surveillance-Broadcast, and experimental results show that the proposed algorithm can improve both the accuracy and time efficiency of the BPNN. In addition, we use the predicted track of the proposed method to detect flight conflict by constructing conflict scenarios. The detecting process and results are visualized in the Geographic Information System, and the correct results of detecting again show that the proposed method is reliable. © 2021 IEEE

关键词： Forecasting

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ESA-Net: A network for enhancing small target detection performance in SAR imagery aircraft

ESA-Net: A network for enhancing small target detection perf...

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IET International Radar Conference (IRC 2023)

作者： Ping Han Han Zhao Tianjin Key Lab for Advanced Signal Processing Civil Aviation University of China Tianjin People's Republic of China

ISBN: (数字)9781837240982

In synthetic aperture radar (SAR) image aircraft target detection, aircraft small targets have a lower AP than aircraft targets and large targets due to the small number of pixel points they occupy and background clutter interference. To solve this problem, this paper proposes a network for enhancing the performance of aircraft small target detection for SAR images(ESA-Net). The network is designed based on yolov5s with a backbone network BH-CSPDarknet and a detection head ***-CSPDarknet allocates more computational resources in the shallow layer of the network to process high-resolution feature maps, which effectively extracts richer feature information of aircraft small ***-Head provides appropriate feature preferences for classification and localisation tasks to provide TFA-Head provides appropriate feature information for classification and positioning task feature preferences, which can effectively suppress the background clutter interference while enhancing the aircraft small target features. The experimental results using the SAR-ADRD dataset show that the method improves the average accuracy of YOLOv5s by 1.9% and the average accuracy of aircraft small targets by 15.6%.

关键词：

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Path planning based on fuzzy-control Dynamic Window Approach 3

Path planning based on fuzzy-control Dynamic Window Approach

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3rd International Conference on Control and Intelligent Robotics, ICCIR 2023

作者： Chen, Wantong Yang, Qianqian Chen, Min Li, Xiaoqiang Liu, Zhuo Tianjin Key Lab for Advanced Signal Processing Civil Aviation University of China Tianjin China School of Electronic Information and Automation Civil Aviation University of China Tianjin China Beijing Sky Aviation Co. Ltd China Sichuan Jiuzhou Aerocont Technologies Co. Ltd China

ISBN: (纸本)9781510671867

A method integrating rapidly-exploring random tree (RRT) and improved dynamic window approach (DWA) is proposed to realize obstacle avoidance of mobile robots in complex dynamic obstacle environments. Based on the known environment information, the global optimal safe path is generated using the improved RRT algorithm. To address the problem of too many invalid nodes in the expansion of the RRT algorithm, the efficiency of the algorithm is improved by introducing a bidirectional alternating search (BAS) strategy;the forward search tree and the backward search tree alternate searching paths with new nodes as the target nodes until the paths meet;and the redundant nodes in the paths are removed using path node filtering to shorten the path. Secondly, the DWA algorithm is used to track the improved RRT algorithm to plan the path. When unknown obstacles appear in the environment, the weights of the DWA algorithm evaluation function are dynamically adjusted by fuzzy control to avoid the obstacles and return to the original route in time. Finally, the simulation experiments verify that the proposed improved fusion algorithm in complex dynamic environment has short running time, small path cost, and always keeps a safe distance from the obstacles to ensure the optimal path is tracked while safely avoiding the dynamic obstacles. © 2023 SPIE.

关键词： Fuzzy control

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Airport Runway Conflict Detection And Visual Simulation

Airport Runway Conflict Detection And Visual Simulation

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Aerospace Engineering and Systems (ISAES), International Symposium on

作者： Tao Song Siyuan Zhang Xiaoyun Shen Siming Yan Tianjin Key Lab for Advanced Signal Processing Civil Aviation University of China Tianjin China Technical Support Department Chongqing Sub-bureau of Southwest China Reginal ATMB Chongqing China

ISBN: (数字)9798350350418

ISBN: (纸本)9798350350425

In order to prevent runway intrusion events due to the incorrect deployment of aircraft by controllers with insufficient situational awareness, a 3D visual simulation system for runway conflict detection is designed. By analyzing different types of conflict scenarios of aircraft arrival and departure, the runway conflict models are constructed, and for different conflict models, the spatial distance method is used to determine whether runway incursion of the aircraft occurs. Then the combination of spatial distance and time threshold are used for the conflict alarm. The runway protection area is constructed, the aircraft motion model of the airport surface is established based on the data of airport surveillance data. The visual simulation of the arrival and departure conflict detection algorithm is realized on the Unreal Engine 4 platform. The experimental results show that according to the arrival and departure conflict detection, when aircrafts are close to each other and less than the encounter time threshold, the system can detect the runway conflict in real time and give the alarm.

关键词： Visualization Solid modeling Analytical models Three-dimensional displays Atmospheric modeling Airports Aircraft manufacture Aircraft Detection algorithms Engines

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