Table of Content

15 February 2024, Volume 44 Issue 1

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Research Trends of Nuclear Clock Technology

LUO Xingqi, LI Wei, LI Chunjuan, LIU Yina, JIAO Tingyu, YANG Ming, SHI Bin, LIU Yuntao

2024, 44(1):  1-6.  doi:10.12060/j.issn.1000-7202.2024.01.01

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The new clock based on atomic nucleus transition,nuclear clock,has important research value.Its principle is to use the electromagnetic wave frequency generated by atomic nucleus transition to accurately measure time.At present,the most promising nucleus for nuclear clock is considered to be the first excited state of ²²⁹Th nucleus ^229mTh.How to excite ²²⁹Th nucleus to the first excited state and obtain the parameters of the first excited state ^229mTh are the focus of current research.The latest measurement data of the excited state energy is E_is=8.28±0.17 eV,which corresponds to the direct laser excitation of ²²⁹Th to ^229mTh with a wavelength of 149.7±3.1 nm.This provides a data reference for the direct laser excitation of the excited state.In addition to direct laser excitation,electron bridge excitation is also an indirect excitation method worth considering.Some potential applications of nuclear clock technology are also introduced,such as the new definition of second,the study of time variation of fundamental constants and dark matter detection.

Overview of Magnetic Measurement Development Based on Quantum Measurement Technology

LI Xiaofang, CHENG Huafu, BAO Zhong, WANG Dongping, ZHANG Feng

2024, 44(1):  7-13.  doi:10.12060/j.issn.1000-7202.2024.01.02

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Aiming at the development history of magnetic quantum measurement technology and the capacity of magnetic quantum metrology standards established based on quantum magnetometers in various countries,proton magnetometers,Nuclear Magnetic Rsonance(NMR) magnetometers,and optical pump magnetometers that have been applied to magnetic quantum metrology standards is studied;Presenting the principles of quantum magnetometers such as CPT magnetometer,SERF magnetometer,diamond NV color-center magnetometer;By summarizing the domestic and international development status of quantum magnetometers with high accuracy,low magnetic field noise and good stability tandards,analyzing the easibility and advantages of replacing the current magnetic parameter metrology standards by using the technical characteristics of various quantum magnetometers;It proposes the potential research direction of quantum measurement technology in the quantization of magnetic measurement standards in the future.

Ion Trap for Single-ion Optical Frequency Standards

JI Qianqian, HAN Lei, SUN Jingxin, CHEN Xing, SU Yabei, CHEN Yu, SHEN Tong, DING Yudong, XUE Xiaobo

2024, 44(1):  14-19.  doi:10.12060/j.issn.1000-7202.2024.01.03

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As the core technology and physical reference system of quantum frequency standards and quantum computing,ion trap has important application prospect and plays an important role in the fields of precision measurement,quantum computing,and high precision positioning and navigation.An ion preparation and trap system based on Paul ion trap is proposed for photo-ionization,ion-trap and laser Doppler cooling.The multi-channel and multi-wavelength laser frequencies are stabilized with a digital PID control method.In the experimental system,the weak fluorescence signal of single-ion is detected representing the single-ion is trapped.The laser frequency drift is stabilized from 500 MHz to ±0.8 MHz.The ion temperature reaches 5.53 mK via laser cooling,approaching the Doppler cooling limit.

Design of the Vibration Isolator for Atomic Beam Chamber of a Transportable Optical Clock

YAO Jiamin, FENG Jinyang, WU Shuqing, ZHANG Lu, XUE Xiaobo

2024, 44(1):  20-28.  doi:10.12060/j.issn.1000-7202.2024.01.04

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Miniatured transportable optical clock has been paid much attentions in recent years as a portable instrument supporting the comparison of clocks from different stations.For an optical clock aiming to operate in vehicles when they are stopped,vibration noise shows an important influence on its frequency shift through disturbing the tilt of the beam generated by the atomic beam chamber.A novel design method of a vibration isolator applied for optical system in transportable optical clock has been proposed,including finding the quantitative relation from the vibration of the chamber base to the beam tilt and the introduced stability to the clock,measuring the real vibration of a cabinet holding the optical clock,and designing three-axis vibration isolator for the atomic beam chamber.A detailed design of a vertical vibration isolator applying TS-300 and 500BM-1 vibration isolation platform is described.It is displayed by calculation and simulation that the stability of the optical clock introduced from the beam tilt caused by vibration noise is considered to be no more than 2.94×10^-15 τ^-1/2 when the clock is placed at the center of the cabinet.Moreover,a better value of theoretical stability introduced by vibration of 1.12×10^-15 τ^-1/2 can be expected with the optimization of the sensor in the vibration isolator according to the simulated results.

Design of Adjustable High Voltage Power Supply for Electron Multiplier of Cesium Atomic Clock

ZHAO Yulong, CHEN Jiang, MA Pei, LIU Zhidong, WANG Dongjun, DONG Pengling, WANG Ji, XUE Xiaohui

2024, 44(1):  29-33.  doi:10.12060/j.issn.1000-7202.2024.01.05

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The electron multiplier is used to amplify and output the transition signal of cesium atomic,the power supply is an important part of the electron multiplier,In the case of gain attenuation,the power supply requirement of the electronic multiplier changes,this paper presents a design scheme of high voltage power supply base on shunt regulation combined with voltage doubling rectifier circuit,the shunt adjustment technology was adopted to realize the power supply output voltage control in the low voltage part,the transformer combined with voltage doubling rectifier circuit to complete high power supply voltage output range is -306~-3 150 V and low power ripple.The power supply telemetry circuit realizes the output voltage telemetry.The spaceborne cesium atomic clock has been tested in orbit for a long time.The test results show that the power supply designed in this paper realizes a wide range of voltage output and can be telemetered within the control range.the power ripple of less than 3.23 V ensures that the indicators of the cesium atomic clock are not affected.

Study of Electron Tunneling Sensing Mechanism in Metal/Air/Metal Microinterfaces Formed by Microsphere Probing

BIAN Xingyuan, ZHAO Dongfang, CUI Junning

2024, 44(1):  34-40.  doi:10.12060/j.issn.1000-7202.2024.01.06

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In order to meet the challenging requirements of high-precision measurement of internal structures such as deep holes and grooves in high-end/cutting-edge instruments and equipments such as inertial gyroscopes and aerospace engines using non-contact sensing methods,research has been conducted on the sensitive mechanisms in the metal/air/metal micro-interface formed by probing a measured part with a spherical sensitive element.From the perspectives of the electron transport mechanism in the thin layer of insulating medium and the change of the insulating medium properties leading to electron transport,various electron transport mechanisms,including electron tunneling,were analyzed in terms of formation conditions and current density characteristics.It was revealed that the Fowler-Nordheim tunneling effect was the main mechanism for the generation of sensing current in the metal/air/metal micro-interface formed by probing with the spherical sensitive element,laying the foundation for exploring a new principle of three-dimensional non-contact nano-sensing methods.

Research on Clock Difference Prediction Based on Improved PSO-BP Model

ZHANG Yingbo, LIU Yinhua, LIU Ya

2024, 44(1):  41-47.  doi:10.12060/j.issn.1000-7202.2024.01.07

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In order to solve the problem that the clock error prediction caused by falling into the local optimal solution during the training process of BP neural networks,the improved particle swarm optimization BP neural network is used for the clock difference forecast model.Firstly,the method of generating several essential parameters in the particle swarm optimization algorithm is improved.Then the initial weights and thresholds of the BP neural network are used as the positions of the particles.The improved particle swarm optimization algorithm iteratively searches the optimal initial weights and thresholds of the network to improve the clock error prediction of BP neural networks,stability and accuracy.This paper analyzes the improvement principle and uses this model to predict clock error,which proves the effectiveness of the optimization of the algorithm after analyzing the global optimal fitness curve and the experiments of the BP model before and after the particle swarm optimization many times,forecasting the clock difference.Compared with the traditional forecasting models such as the ARMA model and GM(1,1) mode,the accuracy of the clock difference forecast based on the improved particle swarm optimization neural network model is improved by 86.5% and 79%,respectively.

Application of Linear Interpolation Methods to Improve the Performance of GPS Common-View Time Comparison

MA Huiying, WANG Weixiong, WU Wenjun

2024, 44(1):  48-55.  doi:10.12060/j.issn.1000-7202.2024.01.08

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In order to solve the problems of the decrease in accuracy of GPS Common View(CV) time comparison with the increase of baseline and the inability to perform common-view time comparison in case of very long baselines,the linearization property of the satellite-ground clock differences based on the international standard GNSS common-view files is used to calculate the interpolation results,which increases the number of available satellites.Finally,the CV results of different satellites are weighted to improve the performance of GPS CV in case of long baselines and to reduce baselines length constraint on CV.The one-month satellite-ground clock differences from three timekeeping laboratories,National Time Service Center(NTSC),Korea Research Institute of Metrology and Science(KRISS),and Physikalisch-Technische Bundesanstalt(PTB),are selected as the data samples,and the satellite-ground clock differences of individual satellite are linearly interpolated with a time interval of 300 s,then the time comparison results of all the satellites at the same time are weighted equally to obtain the final results.The results show that the Root Mean Square(RMS) of time difference between the linear interpolation CV results and the GPS PPP results on NTSC-PTB and KRISS-PTB links are 0.53 ns and 0.8 ns,respectively,which are improved by 48% and 54% compared to the traditional CV.

Research on Remote Time Frequency Source Discipline and Control Methods Based on Multi GNSS Fusion#br#

CHI Wenbo, KOU Qiongyue

2024, 44(1):  56-60.  doi:10.12060/j.issn.1000-7202.2024.01.09

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In response to the problems of multiple transmission error influencing factors and reliance on unidirectional timing in current time-frequency source disciplined control,this study investigates a remote time-frequency signal reproduction and disciplined control method based on GNSS co view,analyzes the relationship between satellite time difference and elevation angle,determines the size of satellite weight values,and proposes a fusion and verification scheme based on satellite observation elevation angle to reduce errors caused by multipath effects.A fusion disciplined control algorithm and implementation strategy were proposed,and a fusion scheme based on multiple GNSS systems was designed.The feasibility of the scheme was verified through multiple GNSS systems and multi frequency data fusion experiments,which improved the disciplined performance of time frequency sources.

A Method to Timing Errors Range Calibrating of Electronic Stopwatch

CHANG Wei, WEN Hai, WU Yingfa

2024, 44(1):  61-65.  doi:10.12060/j.issn.1000-7202.2024.01.10

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In order to meet the requirements of temporary measurement guarantee of high aging tasks,based on the comparative measurement method,the existing measuring equipment of the target range such as time development and control terminal and high-speed video equipment is used to form a measurement calibration device to realize the simultaneous calibration of the timing error of multiple electronic stopwatches,and to calibrate the error of any timing length of the electronic stopwatch.Then,taking the calibration results of the daily difference index of the electronic stopwatch as an example,the measurement uncertainty is assessed and the calibration results given by the superior measurement technical organization are verified.The results show that the above method is more convenient,fast and easy to operate,and the calibration results are scientifically and credible.In the case of meeting the test uncertainty ratio,the emergency measurement guarantee method of using the existing test and measurement equipment resources to solve the temporary calibration problem is feasible and worth popularizing.

Research on Inject Variable Parameter Sinusoidal Jitter Signal for Bit Error Rate Tester

JIA Maohua, TONG Qiong, LI Xiuhua, ZHAO Xianfeng, LIU Ting

2024, 44(1):  66-70.  doi:10.12060/j.issn.1000-7202.2024.01.11

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For ultra-high speed transmission system,the channel model becomes less than ideal,so it can extremely result in bad consequences by accessing signals that exceed the jitter tolerance.The jitter tolerance of different information transmission systems is also different.Most systems can not tolerate jitter beyond 0.5 UI,while some systems can transmit the signal with jitter beyond 1 UI.This requires that the bit error rate tester can generate a bad signal with controllable jitter frequency and amplitude in the evaluation of ultra-high speed transmission system.Traditional jitter injection method of adjusting data phase is difficult to exceed the range of 1 UI.In the article,we describe a method of inject variable parameter sinusoidal jitter signal for bit error rate tester.This method completed the jitter injection of the output signal by sinusoidal frequency modulation of input clock for the code generator.It achieved the injection effect of 0.1~10 UI jitter range,and has been successfully applied to a ultra-high speed bit error rate tester.

Research on Data Link Signals Generation Method

ZHENG Jianfeng, SHI Jiankang, DAI Ouzhixiong, KUAI Wenqin, LIANG Tingting, WANG Ziheng

2024, 44(1):  71-75.  doi:10.12060/j.issn.1000-7202.2024.01.12

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The construction of a complex electromagnetic environment is a necessary condition for modern military training,and the simulation of foreign typical signals is a key aspect.According to surveying the time-domain and spectrum characteristics,and modulation methods of Link-16 and Link-22 data link signals,we propose a data link signal generation method that base on Frequency Hopping(FH) communication,stochastic sequence spread spectrum,8PSK,64QAM,and 16QAM modulation techniques.Compared to real data link signals,the data link signal generated by this method has high similarity in time-domain and frequency-domain characteristics,and has advantages such as low hardware cost,simple structure,and easy implement.And the generated data link signals were tested,and the results showed that the time-domain and spectrum characteristics of the signals were consistent with theoretical expectations,providing a new approach for data link signals generation.

Simulation of Heat Transfer Process in an OCXO under Extreme Environment

LI Jikang, PENG Huili, YU Dejiang, ZHENG Zhenrong

2024, 44(1):  76-82.  doi:10.12060/j.issn.1000-7202.2024.01.13

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The crystal is the core component of the oven-controlled crystal oscillator,which needs to keep the temperature constant,and the great change of the external ambient temperature will surely affect the stability of the output frequency signal of the crystal.According to the working state and mechanism of the OCXO,a mathematical model of the heat transfer process in the steady state is established,the thermal stability of the crystal in high and low temperatures is investigated,and the influence of the output power of the power tubes on the temperature at the crystal in different ambient temperatures is emphasized,and the data during the actual operation of the OCXO are used for verification.The results show that the data obtained through simulation are basically consistent with the measured data;when the ambient temperatures are -40 ℃,25 ℃ and 70 ℃,respectively,the temperature at the stabilized crystal is 85 ℃,and the corresponding output power after stabilization of the power tubes is 3.95 W,1.42 W and 0.74 W.The output power of the power tubes is adjusted to make the temperature at the crystal constant.By adjusting the output power of the power tubes,the crystals can reach the preset temperature and keep it constant under extreme environments,so that the crystals can have high frequency stability and low phase noise level,and ensure the output of high-precision clock signals.

Design of General Simulation Training System Based on Embedded Technology

HU Kaibing, GAO Yuan, LIU Dongxue

2024, 44(1):  83-87.  doi:10.12060/j.issn.1000-7202.2024.01.14

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In order to meet the requirements of simulation training and testing of transmission equipment,a general aircraft simulation training system based on embedded technology is proposed.The simulation system can identify aircraft model information,load the corresponding software,collect control information such as external power supply and power transfer control,and then execute the cooperation according to the communication protocol analysis.Meanwhile,the simulation system has self-test function through the test items set by the program.The simulation training system has high flexibility and adaptability,which provides a general hardware platform.The system can effectively improve the coverage of the aircraft simulation function and shorten the development time.

Research on Optimization Method of Energy Efficiency Resource Allocation for Green Broadband Communication based on 5G#br#

ZHAO Jing

2024, 44(1):  88-92.  doi:10.12060/j.issn.1000-7202.2024.01.15

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Aiming at the optimization of energy efficiency in 5G communication,the maximization of energy efficiency resource allocation in large-scale MIMO-OFDMA system among downlink users is analyzed.Secondly,an energy efficiency maximization resource allocation algorithm based on the minimum rate requirement is proposed.After the bandwidth is reasonably allocated,the power and the number of antennas are allocated to improve the optimal energy efficiency of the system.Finally,based on the Lagrange function,the optimal energy efficiency objective function is converted into a convex optimization problem to solve the optimal solution.In the experimental phase,a typical wireless communication network is taken as an example to analyze.The results show that the proposed algorithm has the best comprehensive performance in terms of energy efficiency,throughput,and the optimal number of base station antennas compared with NSGA-Ⅱ and FP-based resource allocation algorithms.The proposed model provides a reference for the study of the optimal resource scheduling scheme of 5G communication system.

Power Prediction Method of Distributed Photovoltaic Access Distribution Network Considering Information Time Shift

SHANG Qinggong, HANG Zhou, SHANG Nuan

2024, 44(1):  93-98.  doi:10.12060/j.issn.1000-7202.2024.01.16

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In order to reduce the error of power prediction values for distributed photovoltaic access distribution networks,a distributed photovoltaic access distribution network power prediction method considering information time shift is proposed.Using Pearson correlation coefficient to describe the correlation between key meteorological factors and photovoltaic output power of NWP,determine the optimal time shift,and correct the meteorological information offset caused by geographical location;using random forest algorithm to process distributed photovoltaic output data and screen high contribution feature parameters;after learning feature parameters using a bidirectional GRU neural network,each time step of the input time series is captured using a one-dimensional convolutional neural network;introducing attention mechanism to reduce the impact of meteorological time shift on distributed photovoltaic output and achieve the output of power prediction results.The experimental results show that this method can calculate the Pearson correlation coefficient between distributed photovoltaic output and meteorological data,and determine its optimal time shift;the error between predicted values and actual values is relatively small under different meteorological conditions.