Table of Content

25 March 2020, Volume 40 Issue 1

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A Memory of the Early-stage Atomic Clocks Development in China

WANG Yi-qiu

2020, 40(1):  1-11.  doi:10.12060/j.issn.1000-7202.2020.01.01

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This conference is held every two years by four committees.This year is the 20^th anniversary.For the last 20 years,the research of atomic clocks in our country has achieved remarkable progress.We have now become a large country developing atomic clocks.While what we do is mostly following others,the original innovative research is still not much.Without changing this situation,it would be difficult to stand on our own and contribute to the economic development of our country.In this paper,we briefly review our history of developing the atomic clocks,in the meantime we look back to some stories of fundamental research.It is the deeply analyzing of those experimental phenomena that we can achieve the progress under poor conditions.The important role of the skillful craftsman is also mentioned.This paper also talks about the spirit of cooperation between different organizations.In general,this paper tells some stories in the course of developing atomic clocks,and expresses some opinions about the atomic clock industry.There are still quite a lot of difficulties revitalizing the nation.We have to overcome these difficulties with original innovative work.Thus,the spirit and tradition of studying and hardworking is still necessary.

Design of Cryogenic Sapphire Oscillator with High Frequency Stability

ZHU Xi, CHEN Hai-bo, HUANG Kai, GAO Lian-shan, WANG Liang

2020, 40(1):  12-16.  doi:10.12060/j.issn.1000-7202.2020.01.02

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Cryogenic sapphire crystal has a characteristic of low loss.Based on this property，sapphire loaded cavity operating on the whisperinggallery mode WGH_12,0,0 has been constructed.The Q factor can achieve 4.0×10⁸ when the cavity temperature is controlled at 6.4 K.Then on this basis，positive feedback loop oscillator is implemented.In order to improve the frequency stability，the phase of oscillator is controlled according to POUND circuitry.While to test the relative frequency stability，two cryogenic sapphire oscillators are set in one cryocooler cryostat.The two CSOs oscillate at 9.204 GHz and 9.205 GHz，respectively.After mixing and calculating，the relative frequency stability of 3.28×10^-15/s is obtained.

Stabilizing the Optical Frequency by Laser-induced Fluorescence in Optically Pumped Cs Beam Frequency Standard

ZHAO Xing-wen, CHEN Hai-jun, YANG Lin, WEI Qiang, LI Dong-xu, LI Yu-ao

2020, 40(1):  17-22.  doi:10.12060/j.issn.1000-7202.2020.01.03

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For Optically Pumped Cesium Beam Frequency Standard,the stability of the reference source which is used to stabilize laser frequency,determine the frequency stability of the laser system,and then that of the Optically Pumped Cesium Beam Frequency Standard.Two methods can be used to stabilize laser frequency,which are by saturated absorption spectroscopy(SAS),and by laser-induced fluorescence.We compared the two methods and achieved preliminary results：compared to SAS,the short-term stability has not deteriorated significantly,while the long-term stability has improved significantly：3.21E-14/100 000s,1.13E-14/400 000s,and still under test.The application of frequency stabilization technology of cesium beam tube has potential to improve the long-term stability and enhance environmental adaptabilityof the Cesium Atomic Clock.

Simulation Study of Box Type Electron Multiplier System with Different Paths

WANG Yun-jia, WANG Yi-fei, GAO Lian-shan, LI Wei

2020, 40(1):  23-28.  doi:10.12060/j.issn.1000-7202.2020.01.04

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Models of box type electron multiplier system with different paths were established by CST software.Adjacent dynodes configurations were divided into “Z” and “U” types.The electric field distribution,electron trajectory and electron multiplier gain of the two minimum dynodes configurations units and derivative paths were calculated.The simulated results show that the dynodes with different configurations have a slight different internal electric field,but the electron trajectory and electron multiplier gain are quite different.In view of the rationality of assembling box type multiplier system actually,basic principles of dynodes configurations were summarized by computational analysis.In the case of eight dynodes,configurations paths were optimized reasonably.

Research on Consistency between Master and Backup Clock in Time-keeping System

YANG Fan, CHEN Xue-jun, ZHANG Ran

2020, 40(1):  29-32.  doi:10.12060/j.issn.1000-7202.2020.01.05

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Master clock system is an important part of time-keeping system，its operating state is directly related to the performance of time-keeping system.In order to improve reliability，it is very important to establish backup system.In this paper，the methods of maintaining consistency between the master and backup clock is studied，the consistency system is built.The model of clock difference is established through analyzing the characteristic of clock，then the frequency of backup clock is steered，to realize the consistency between master and backup clock.The steering result shows that the master-backup time difference is keeping in 1ns，frequency deviation is keeping in 10E-15 scale.

Long Base-line Common View Time Comparison based on BDS-3

WU Wen-jun, WANG Wei-xiong, WANG Xiang, GAO Zhe, AN Wei, DONG Shao-wu

2020, 40(1):  33-37.  doi:10.12060/j.issn.1000-7202.2020.01.06

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GNSS common view is one of the major remote time transfer methods.BeiDou common view(CV)time comparison has been performed based on the timekeeping system maintained by National Time Service Center，Chinese Academy of Sciences(NTSC)and Institute of Photonics and Electronics，Czech Academy of Sciences(TP)via BDS-3，the Asia-Euro CV time comparison was carried out.Firstly，the single-station BeiDou satellites visual number and satellite elevation are analyzed.Then，the noise reduction processing was carried out by the Vondark filter used the method of the frequency response.Finally，the results of the comparison between the BDS-3 and the BDS-2 and GPS CV were compared.The results show that in the current stage of BeiDou global networking，although the BDS-3 has fewer visible satellites than the BDS-2，the accuracy of the common view is 1.16ns，which is about 19% higher than that of the BDS-2.It is more closed to GPS than BDS-2.

Research on Common View Time Comparison of GPS Multi-receiver Combinations

ZHANG Jian, DONG Shao-wu, WU Wen-jun, WANG Wei-xiong, GUO Dong, YUAN Hai-bo

2020, 40(1):  38-45.  doi:10.12060/j.issn.1000-7202.2020.01.07

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GPS common view（CV）has always been one of the main technical means of international time comparison，in order to improve the performance of GPS common-view time comparison，utilizing multiple receivers of the two timekeeping laboratories of the National Time Service Center （NTSC）and the German Physikalisch-Technische Bundesansalt（PTB）,based on the technical principle of multi-receiver combination，compose two multi-receiver systems,use multi-receiver data fusion technique，calculate the observation data of two multi-receiver systems and verify the time comparison test.The results showed that Multi-receiver combination not only improves the reliability and stability of GPS common view，but also improves the accuracy of time comparison link.The multi-receiver link GPS CV time transfer standard deviation （STDEV）value is 1.36ns，compared with the single receiver link time，the result is improved on average19.4%.the stability can reach10^-14（1d）.

Design of High-frequency OCXO with High Stability

PENG Hui-li, CHEN Jin-he, HAN Yan-ju, YU De-jiang, QIAO Zhi-feng, ZHENG Hong-yao

2020, 40(1):  46-50.  doi:10.12060/j.issn.1000-7202.2020.01.08

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This paper describes a kind of high frequency oven-controlled crystal oscillator(OCXO) with high stability.This OCXO is designed using the method of low-frequency oscillation,low noise frequency multiplication and precision temperature control.The experimental results show that the short-term stability of the 100MHz OCXO reaches 2.68E-13/s,2.54E-12/100s；the daily aging rate is 7E-11/d and the harmonic rejection is better than -50dBc.The OCXO has experienced environmental tests such as random vibration,shock,and temperature shock,and the frequency deviations are all less than ±5E-9 before and after these tests.The OCXO demonstrated in this work can satisfy the need for high frequency and high stability signal source in many fields,and is helpful to simplify the system and reduce the volume of the equipment.

Research on Traceability of Multi-band Spectral Radiometer

WANG Shao-shui, FEI Feng, ZHAO Fa-cai, SUN Quan-she

2020, 40(1):  51-55.  doi:10.12060/j.issn.1000-7202.2020.01.09

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Spectral radiance meter is one of the key equipments to realize high precision spectral calibration of space remote sensing instrument in ground laboratory.Based on the radiance transfer principle of standard detector,a multi-band light shield with 10 measuring channels is developed by using field of view aperture,narrow-band interference filter and silicon photodiode.Spectral radiometer,the measured wavelength is in the range of 400 to 1100 nm.The instrument has a calibration channel and matches with the integral sphere monochrome light source to realize traceability of spectral radiance.The uncertainty of measurement is better than 2.2%.

Design on Special Metering Plug for DC Stabilized Power Supply without Voltage Sampling Terminal

JING Xiao-dong, ZHENG Shi-qi, REN Yu-long, LI Ying-hui, FAN Ya-jie, DU Lei

2020, 40(1):  56-60.  doi:10.12060/j.issn.1000-7202.2020.01.10

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In practical application,there is a certain difference between the output voltage of DC stabilized power supply in the no-load state and the on load state.This difference is called the stabilized load effect of DC stabilized power supply.The load effect of DC stabilized power supply is an important index to show its output voltage's ability to restrain the load change in the output circuit.According to its output terminal,DC stable power supply can be divided into two output forms,with and without voltage sampling terminal.In this paper,by analyzing the common connection method of DC stabilized power supply load effect calibration,a special plug is designed for the DC stabilized power supply without voltage sampling terminal,which makes the connection more convenient and quick when the minimum measurement error is introduced,thus improving the efficiency of DC stabilized power supply calibration.

Research on Multimeter Digital Recognition Technology based on Machine Vision

PENG Cheng, DING Wei, HOU Xu-Wei, LI Jun

2020, 40(1):  61-66.  doi:10.12060/j.issn.1000-7202.2020.01.11

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To improve the automation level of the handheld digital multimeter calibration system，two methods of digital recognition schemes based on machine vision were proposed by studying three different types of character recognition technology，namely image gray threshold method，target classification by traditional methods and deep learning.The test result shows that although the character recognition accuracy of two schemes can both reach 99.8%，there are significant differences in proportion of hardware resources and degree of programming difficulty.After this machine vision character recognition function has been successfully developed，it will provide useful reference for more metering test equipment without program-controlled communication interface，or similar digital recognition in some dangerous metering working environment which is not suitable for manual operation.

A Comprehensive Experimental Chamber Design and Simulation Technology based on Reverberation Chamber Platform Combining Electromagnetic Environment with Natural Environment

WU Jian, JIA Xiao-qing

2020, 40(1):  67-72.  doi:10.12060/j.issn.1000-7202.2020.01.12

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This paper presents a comprehensive experimental chamber design and a simulation technology based on reverberation chamber platform combining electromagnetic environment with natural environment.The test box integrates the environmental test condition and the electromagnetic radiation sensitivity test condition，which can simultaneously impose electromagnetic radiation interference on electronic equipment under various environmental conditions，such as high or low temperature，damp or heat，temperature cycle，and temperature shock，so as to assess the adaptability of electronic equipment under complex conditions of applying environmental stress and electromagnetic stress.Through design，simulation and test，it is proved that the technology meets all the expected indexes and is easy to be popularized，which can further reduce the cost of electromagnetic and environmental tests.

Design and Verification of Multi-channel Isolated Voltage Acquisition Board

SANG Shang-ming, YIN Cong-ru, WEN Xing-xi, ZHANG Xian, LUO Zhen, PENG Shuai

2020, 40(1):  73-78.  doi:10.12060/j.issn.1000-7202.2020.01.13

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This paper designs a multi-channel isolation voltage acquisition board based on the bus voltage and the secondary power supply voltage measurement in the test stage of satellite ground power supply and distribution.First briefly introduced the satellite bus voltage,the secondary power supply voltage and telemetry command signal is a typical interface card scheme based on mature CPCI-bus architecture to realize the generalized design of test equipment.Through the development practical products and system testing,the board can meet the requirements of multi-channel isolation voltage acquisition for power supply and distribution ground test equipment.

Research on Anti-jamming Performance of Array Antenna based on RLS Algorithm

DONG Hao, CONG Wei-jie, SHANG Feng

2020, 40(1):  79-84.  doi:10.12060/j.issn.1000-7202.2020.01.14

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Aiming at the influence of antenna array on the performance of the algorithm in the anti-jamming navigation system，based on the recursive least squares algorithm in the airspace zeroing algorithm，the steering vector of different array antenna models was established，and using MATLAB simulation，anti-interference performance was compared of array antenna and 4-element planar array antenna under the same interference signal.Validation analysis shows that there is a phenomenon of inconsistent signal receiving gain between the array elements of the conformal array antenna，which will affect the anti-interference performance of the algorithm.In contrast，the centered circular array in the planar array has a better anti-interference effect and a higher algorithm stability，which can generate an accurate “zero trap” in the direction of the interference signal.

Simulation of Nonlinear Characteristics of Space Traveling Wave Tubes for Satellite Internet Application

LIANG Xiao, QU Bo, GUO Heng-hui, LIU Meng-meng

2020, 40(1):  85-90.  doi:10.12060/j.issn.1000-7202.2020.01.15

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In order to study the nonlinear characteristics of space traveling wave tube(TWT)for satellite internet application，a numerical calculation program was written on the MATLAB platform using an improved one-dimensional large-signal model combined with the cold characteristics parameters of TWT calculated by CST.Using the written program，the main characteristics of amplitude modulation-amplitude modulation(AM-AM)and amplitude modulation-phase modulation(AM-PM)are calculated based on the model of two kinds of space TWT(Ka-band and Q-band).In parallel，third-order intermodulation distortion(IMD3) and noise power ratio(NPR)were also calculated.The effect of input power back-off on these nonlinear characteristics are analyzed and compared with the actual test results from a vector network analyzer，where the discrepancy between the calculated and test results is within 1dB.A simulation tool is provided for the design of high linearity TWTs.