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15 December 2019 Volume 32 Issue 12
  
    A Power Feedback Circuit of IF Signal With Dual-Coupled and Dual-Mixed
    ZHENG Renping,YANG Qinghui,ZHANG Huaiwu
    Electronic Science and Technology. 2019, 32(12):  1-5.  doi:10.16180/j.cnki.issn1007-7820.2019.12.001
    Abstract ( 313 )   HTML ( 279 )   PDF (1053KB) ( 95 )  
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    In ALC system, there is a major limitation of commonly used power feedback circuits: the amplitude modulation dynamic range is restricted by the level detector and associated circuitry, which is typically much lower than the power variable range of the linear modulator. This paper introduced a dual-coupled and dual-mixed IF signal power feedback circuit, so that the detector could feedback and adjust the power amplitude of the RF output signal only by detecting the power of the fixed IF signal. The test showed that when the RF input signal of the circuit changed at 24 GHz, the obtained IF signal was fixed, which was equal to 54 MHz of the crystal signal. And when the attenuation of the linear modulator changed from 0 to 31.5 dB, the IF signal power had a good linear relationship with the RF output signal power, which met the expected design requirements.

    Design and Implementation of a Receiver for Leaky Cable Intrusion Detection System
    XU Tao,ZHANG Yi,ZHAO Nengwu,WANG Yuhao,LI Minyue,LU Hongmin
    Electronic Science and Technology. 2019, 32(12):  6-10.  doi:10.16180/j.cnki.issn1007-7820.2019.12.002
    Abstract ( 234 )   HTML ( 19 )   PDF (978KB) ( 33 )  
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    Recently, the perimeter intrusion detection system based on leaky cable has attracted much attention of researchers and markets in security field because of its good security concealment, terrain fitting installation, omnibearing vigilance and all-weather work ability. In this paper, a new design method of zero-IF quadrature demodulation receiver was proposed. This method transformed high frequency signal into baseband signal for processing, which avoided the high cost of ultra-high speed AD devices used in the conventional design, and improved the performance of leaky cable intrusion detection system. ADS simulation results suggested that the receiver had 2.8 dB noise figure and 69 dB link gain in the 80120 MHz working frequency band. The test results showed that the receiver had 3.2 dB noise figure and 67 dB link gain in the same working frequency band, and the measured results were in good agreement with the simulation results. The system test revealed that the positioning accuracy of the perimeter intrusion detection system constructed with this receiver was better than 10 m, the false alarm rate and missed alarm rate were better than 5%.

    A Level Shift Circuit for High Voltage Motor Driver
    YU Ruirong,ZHANG Qidong
    Electronic Science and Technology. 2019, 32(12):  11-16.  doi:10.16180/j.cnki.issn1007-7820.2019.12.003
    Abstract ( 402 )   HTML ( 94 )   PDF (1162KB) ( 69 )  
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    In order to overcome the disadvantages of unsatisfactory and unstable output voltage range for the traditional level shift circuit, this paper designed a two-stage level shift circuit with high stability and low power consumption. The first-stage circuit with fixed bias was adopted to eliminate the dependence of NMOS and PMOS electrical parameters and improve the stability. The second-stage circuit widened the output voltage range and provided reliable gate voltage to PMOS high side. The simulation results showed that the designed level shift circuit converted low voltage to high voltage, and the output range met the requirements of the high side gate driver. This circuit achieved two types of drive control both Single-polarity and Bi-polarity in high voltage motor driver.

    A Real-time Full Network Performance Anomaly Detection Algorithm Based on Principal Component
    ZHANG Tianqi,ZHANG Shunkang
    Electronic Science and Technology. 2019, 32(12):  17-21.  doi:10.16180/j.cnki.issn1007-7820.2019.12.004
    Abstract ( 285 )   HTML ( 90 )   PDF (859KB) ( 66 )  
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    Network performance anomaly detection is of great significance to promote the healthy development of the network. In order to solve the problem that the existing anomaly detection methods are mostly offline and cannot provide good real-time online detection performance, the principal component analysis method was used to establish the anomaly detection model, and the network anomaly detection threshold was adjusted adaptively by combining historical performance data with recent network performance fluctuations. The real-time online anomaly detection was realized and the data was collected on NFV network. The experimental results showed that the proposed method reduced the false alarm rate by 5% to 8% compared with the offline detection method which was widely used, indicating the greater use value of the proposed method for network operators.

    Exponential Voltage Generation Method for Crystal Oscillator Temperature Compensation
    SUN Xiaohua,WANG Hongxing,ZHANG Qidong
    Electronic Science and Technology. 2019, 32(12):  22-26.  doi:10.16180/j.cnki.issn1007-7820.2019.12.005
    Abstract ( 307 )   HTML ( 12 )   PDF (752KB) ( 38 )  
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    In order to obtain a more accurate clock source, the crystal oscillator was compensated to reduce the frequency variation with temperature. Compared with different temperature compensation methods of crystal oscillators, analog temperature compensation had higher performance. The focus of the analog temperature compensation circuit was to obtain the compensation voltage exponentially. This paper presented an analog multiplier method. Four MOSFETs were connected to the inputs of the fully differential amplifier. Combining the current-voltage relationship in the linear region multiplied the two analog signals. Different compensation voltages which were linear, quadratic, cubic, quadratic, and fifth power relationship with temperature would be generated. These voltages were superimposed by the summing circuit and could be used for high-order temperature compensation of the crystal oscillator. The differential mode gain of the fully differential amplifier was 78.6 dB, and the two inputs were multiplied by multiplier. Temperature stability of ±2 ppm deviation was achieved.

    9 kHz1.4 GHz High Precision Fast Random Frequency Hopping DDS Frequency Synthesizer
    WANG Jiamin,YANG Qinghui,ZHANG Huaiwu
    Electronic Science and Technology. 2019, 32(12):  27-32.  doi:10.16180/j.cnki.issn1007-7820.2019.12.006
    Abstract ( 326 )   HTML ( 10 )   PDF (1073KB) ( 39 )  
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    In order to adapt to the high requirements of microwave system for frequency synthesizer, including high accuracy, fast switching, random hopping, a frequency synthesizer based on DDS chip AD9914 was designed. The implementation of the fast frequency control word algorithm in the FPGA was combined with the LFSR to generate random frequency hopping points. FPGA was used to control the AD9914 and the frequency synthesizer was capable of achieving frequency accuracy of 10-5 Hz and random frequency sweeping within 100 ns. The experimental results showed that when the output frequency was between 9 kHz to 1.4 GHz, frequency point was very accurate, the full-frequency sweeping could be realized and the frequency hopping switching time was 90 ns, which achieved the goal of high-precision agile frequency signal generator and had broad application prospects.

    Natural Scene Text Recognition Algorithm Based on Attention-CTC
    HE Wenjie,LIU Jingbiao,PAN Mian,LÜ Shuaishuai
    Electronic Science and Technology. 2019, 32(12):  32-36.  doi:10.16180/j.cnki.issn1007-7820.2019.12.007
    Abstract ( 445 )   HTML ( 15 )   PDF (826KB) ( 56 )  
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    In order to solve the problems of the difficulty of character segmentation in text recognition and the recognition accuracy dependent on dictionary in natural scene, a text recognition algorithm with attention mechanism and connection time classification loss was proposed. The convolutional neural network and the bidirectional long-term memory network were used to extra the feature of the image. The Attention-CTC structure was used to decode the feature sequence, which effectively solved the problem of Attention decoding unconstrained. The algorithm avoided additional alignment preprocessing and subsequent syntax processing on the tag, which sped up the training convergence rate and significantly improved the text recognition rate. Experimental results showed that the algorithm was robust to texts with complex fonts and complex backgrounds.

    Kinematics Analysis and Simulation for a Novel 5-DOF Serial-Parallel Robot
    CHEN Jiupeng,SAN Hongjun,LI Pengfei,ZHANG Daoyi,XIONG Binzhou
    Electronic Science and Technology. 2019, 32(12):  37-43.  doi:10.16180/j.cnki.issn1007-7820.2019.12.008
    Abstract ( 330 )   HTML ( 12 )   PDF (1106KB) ( 46 )  
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    Parallel robots have higher strength stiffness, but the working space is smaller; tandem robots have larger working space, but the strength stiffness is smaller. With the advantages of both parallel mechanisms and serial mechanisms, the serial-parallel mechanism has more extensive application prospects. In this paper, a novel 5-DOF serial-parallel robot was introduced to realize the machining of complex curved surface. The structure characteristics and motion properties were analyzed and the degree of freedom was calculated by screw theory. The forward and inverse kinematic solution of robot were deduced by numerical and analytical method respectively. The 3D model of the robot was built with SolidWorks and imported into ADAMS for kinematics simulation. The results showed that the robot could realize the processing of complex surface, and could provide help for industrial production.

    Exploration and Teaching Research of Innovation Experiment of Solar Blind Ultraviolet Communication
    ZHENG Ruilin
    Electronic Science and Technology. 2019, 32(12):  43-47.  doi:10.16180/j.cnki.issn1007-7820.2019.12.009
    Abstract ( 270 )   HTML ( 11 )   PDF (1005KB) ( 23 )  
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    E laser/mercury lamp and ultraviolet photodiode were mostly used as the light source and the detector in the solar blind ultraviolet communication system. The overall system was difficult to meet the experimental teaching requirements of electronic communication engineering for their large in volume and complicated in operation. Therefore, it was urgent to establish a new innovative experimental teaching platform of optical communication. In this paper, a new compact solar blind ultraviolet communication system was designed and constructed, which used ultraviolet LED as the light source, visible PIN tube as the detector, and the fluorescent glass as the spectrum converter to realize long-distance and high-sensitivity solar blind ultraviolet transmission and detection. This novel system not only increased the output signal amplitude, but also increased the maximum photocurrent to 23.3 μA. Through practical teaching, it was found that the innovative experimental platform played an important role in improving comprehensive ability, understanding and efficient of students to use of solar blind ultraviolet communication experimental equipment.

    Designof Pedestrian Flow Statistics System on Video Monitoring
    YIN Tao,CUI Jiadong
    Electronic Science and Technology. 2019, 32(12):  48-52.  doi:10.16180/j.cnki.issn1007-7820.2019.12.010
    Abstract ( 381 )   HTML ( 20 )   PDF (1715KB) ( 39 )  
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    Aiming at the problems of backward pedestrian statistics, non-real-time and backward statistical data, intelligent video surveillance and image recognition were proposed for real-time pedestrian traffic statistics. The system calculated the pedestrian target characteristics according to the integral channel idea, and used the Adaboost algorithm to train the classifier to locate and identify the pedestrian target in the image frame. Based on the identified targets, the CPU multi-task model was used to improve the kernel correlation filtering algorithm to track the target in real time and obtain the pedestrian traffic. The test results showed that the system can recognize, track and count pedestrian targets in real time. The average recognition rate was 93%, and the improved multi-task model increased the tracking rate by about 20%.

    Molecular Dynamics Simulation of Monocrystal Germanium Nanocutting with Vacancy Defects
    ZHANG Yifei,LI Shan,YANG Xiaojing,WU Shaohua,LIU Hao
    Electronic Science and Technology. 2019, 32(12):  53-57.  doi:10.16180/j.cnki.issn1007-7820.2019.12.011
    Abstract ( 179 )   HTML ( 10 )   PDF (1168KB) ( 19 )  
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    In order to study the nano-cutting process of monocrystal germanium with vacancy defect, a monocrystal germanium cutting model with vacancy defect was constructed and simulated by molecular dynamics simulation. In this paper, the change of system potential energy and the change of cutting force during cutting process are considered from the atomic point of view. The study explained the material removal process and the formation mechanism of chip, and analyzed the influence of vacancy defect on cutting. The results showed that more vacancies could lead to the increase of system potential energy in the cutting process of monocrystal germanium. This result indicated that the increase in vacancy defects was able to exacerbate system instability.

    The Study of Improved Self-adaptive Genetic Algorithm in Association Rules
    LI Cunjin,SUN Hong
    Electronic Science and Technology. 2019, 32(12):  58-63.  doi:10.16180/j.cnki.issn1007-7820.2019.12.012
    Abstract ( 231 )   HTML ( 13 )   PDF (979KB) ( 32 )  
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    Aiming at the low efficiency of traditional association rules in the data mining process under the big data environment, genetic algorithm was integrated. Meanwhile, the traditional genetic algorithm was also optimized to apply to the mining of association rules. Aiming at the traditional adaptive genetic algorithm, the crossover operator and mutation operator were optimized adaptively, and then the degree of interest was added to eliminate some rules that had no practical effect. Experimental results showed that combining cloud computing technology and the improved algorithm in the extraction of association rules could optimize its mining efficiency and overcame the shortcomings of adaptability and usability, which not only accelerated the convergence speed of the algorithm, but also improved the quality of understanding.

    Study on Electromagnetic Properties of Transition Metals Based on Density Functional Theory
    QING Xiaomei,ZHEN Siqi
    Electronic Science and Technology. 2019, 32(12):  64-68.  doi:10.16180/j.cnki.issn1007-7820.2019.12.013
    Abstract ( 209 )   HTML ( 9 )   PDF (851KB) ( 12 )  
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    The electronic and magnetic properties of metal transition metal disulfides (mTMDC) had been studied by adjusting the size limits from 2D to 1D. Compared with the semiconductor TMDC obtained by experiments, the combination of mTMDC monolayer and nanoribbon was greater and the stability was better. Compared with its semiconductor TMDC, the 2D MX2 (M = Nb, Ta; X = S, Se) single layer was a non-ferromagnetic metal. When the band width of mTMDC nanoribbons approaches 13 and 7, i.e., when the sawtooth and armchair edge terminals were formed respectively, the mTMDC transited from metal to semiconductor; when the bandwidth of mTMDC nanoribbons further decreases, these nanoribbons will be converted back to metal. Zigzag terminal acceptance tapes were Ferromagnetic Semiconductors whose magnetism could also be adjusted by hydrogen edge passivation, while armchair nanoribbons were non-ferromagnetic semiconductors. The results showed that mTMDC had a wide range of physical properties, ranging from metal to semiconductor, non-ferromagnetic to ferromagnetic, and was very suitable for applications requiring stable narrow bandgap semiconductors with different magnetic properties.

    Network Information Security Management Technology Based on Intrusion Monitoring
    LIU Dongwei
    Electronic Science and Technology. 2019, 32(12):  68-71.  doi:10.16180/j.cnki.issn1007-7820.2019.12.014
    Abstract ( 185 )   HTML ( 11 )   PDF (650KB) ( 26 )  
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    In view of the problem that network security faces the threat of illegal intrusion and poor real-time defense, this paper designed a network information security management technology based on Intrusion monitoring. By adding intrusion monitoring module to the existing network model, the three modules of network information acquisition, information processing and information analysis were combined for intrusion monitoring. In order to improve the accuracy of intrusion monitoring, this paper used the decision tree method based on data dimension reduction to identify abnormal data, and effectively realizes different types of abnormal data monitoring. The system validation showed that the intrusion detection method proposed in this paper had a good monitoring effect for different types of intrusions, and had an improvement of more than 8% compared with the existing algorithms.

    Research on Workpiece Location Technology Based on Monocular Vision
    YANG Yunhui
    Electronic Science and Technology. 2019, 32(12):  72-75.  doi:10.16180/j.cnki.issn1007-7820.2019.12.015
    Abstract ( 226 )   HTML ( 16 )   PDF (618KB) ( 35 )  
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    Aiming at the problem of position and pose location of common workpiece, a workpiece location scheme using monocular vision platform and CAD model was proposed. In order to clarify the specific design of this scheme, this paper introduced the calibration method of monocular camera, the related technology of workpiece image recognition, designed the image preprocessing process of workpiece, and finally proposed a monocular vision localization algorithm based on CAD model. The experimental results showed that, compared with the location scheme based on priori relationship, the location scheme had higher accuracy and better flexibility, and could meet the needs of common workpiece location.

    Intelligent Home Control System Based on PLC
    CHAO Fen
    Electronic Science and Technology. 2019, 32(12):  76-79.  doi:10.16180/j.cnki.issn1007-7820.2019.12.016
    Abstract ( 1079 )   HTML ( 74 )   PDF (571KB) ( 131 )  
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    In view of the fact that the traditional home life can no longer meet people's requirements of intelligent, humanized and safe home life, this paper designed and developed a set of intelligent home control system based on PLC. The control system collected and processed information in the home environment through different sensors, and sended alarm information to the household when the data was abnormal. At the same time, households can also use the system for remote control of access control and lighting in the home environment and operate devices,and has a certain degree of real-time and accuracy. With the popularization of smart home concept and in-depth research, the system will played a greater rolein smart home life.

    Research on Mobile Signaling Data Acquisition Technology under LTE Core Network Architecture
    LONG Pin
    Electronic Science and Technology. 2019, 32(12):  80-83.  doi:10.16180/j.cnki.issn1007-7820.2019.12.017
    Abstract ( 291 )   HTML ( 12 )   PDF (656KB) ( 25 )  
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    As an significant support of the LTE core network, the mobile phone signaling data acquisition system under the LTE core network is a tool that can effectively monitor the signaling network in real time. In order to meet the technical research requirements of mobile phone signaling data acquisition system, this paper studied the LTE core network signaling system architecture and the corresponding signaling data acquisition system structure, and proposed the signaling data collection scheme and analized scheme under the LTE core network architecture. At the same time, the corresponding key technologies were given. The mobile phone signaling data acquisition technology under the LTE core network architecture studied in this paper had made certain contributions to the stability, security and efficiency of the signaling network. At the same time, for the development and research of signaling monitoring and acquisition system, the research content provided in this paper was of great significance.

    Research on Recognition Method of Legal Documents Based on Deep Learning
    MENG Xin
    Electronic Science and Technology. 2019, 32(12):  84-86.  doi:10.16180/j.cnki.issn1007-7820.2019.12.018
    Abstract ( 306 )   HTML ( 18 )   PDF (14316KB) ( 234 )  
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    In order to improve the construction efficiency of the knowledge base of digital legal documents, this paper proposed a method of legal document recognition based on the theory of deep learning. This method constructed deep neural network based on long and short term memory (LSTM) network element structure, and realized entity recognition in natural language. After testing, this method could effectively extract the names of people, places and institutions in legal documents. In the test set used in this paper, compared with the CRFs algorithm, this method could achieve about 10% improvement in accuracy, recall and F.

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