国内外频率标准发展现状

时间频率在国家经济建设、科学研究、国家安全具有十分重要的意义。本文介绍了国内外高稳晶振、铷原子频率标准、守时型氢原子频率标准和铯原子频率标准、微型相干布局囚禁原子钟、低温蓝宝石微波源和超稳激光微波源以及铯原子喷泉钟的国内外发展情况、技术指标等。铷原子频率标准打破国外垄断，为北斗导航系统提供高精度的时间基准，守时型氢原子频率标准和铯原子频率标准已实现工程化，但日频率稳定度和日频率漂移率指标有待进一步提高，铯喷泉基准方面已接近国际先进水平，新型原子频标发展方兴未艾。

Research on Calibration Technology for Amplitude and Phase #br# Characteristics of Large Double Reflector Compact Field

The compact field is the key device for antenna and target RCS testing.It can calibrate the spherical wave from the feed to a quasi-planar wave at close range.In order to evaluate whether the electromagnetic wave distribution generated in the quite zone of the compact field conforms to the quasi- planar wave characteristics,it is necessary to build a high-performance microwave amplitude-phase transmitting and receiving system and a large-scale multi-degree-of-freedom high-precision scanning system on site.In this paper,the performance calibration requirements of a large double reflector compact field are taken as an example.From the aspects of on-site measurement of amplitude and phase system construction,large-scale complex scanning system design,and on-site measurement implementation,the related technologies of field calibration of compact field quite zone performance are analyzed in detail.The measured results show that the calibration system built on site meets the performance requirements of the long-distance large double-reflection surfacecompact field quiet zone,and the values of each test parameter meet the design requirements of the compact field.