A compact direct digital frequency synthesizer （DDFS） for system-on-chip implementation of the high precision rubidium atomic frequency standard is developed. For small chip size and low power consumption, the phase...A compact direct digital frequency synthesizer （DDFS） for system-on-chip implementation of the high precision rubidium atomic frequency standard is developed. For small chip size and low power consumption, the phase to sine mapping data is compressed using sine symmetry technique, sine-phase difference technique, quad line approximation technique,and quantization and error read only memory （QE-ROM） technique. The ROM size is reduced by 98% using these techniques. A compact DDFS chip with 32bit phase storage depth and a 10bit on-chip digital to analog converter has been successfully implemented using a standard 0.35μm CMOS process. The core area of the DDFS is 1.6mm^2. It consumes 167mW at 3.3V,and its spurious free dynamic range is 61dB.展开更多
In this paper, we analyze and design a new type of servo system with noninteger voltage controlled crystal oscillator （VCXO） for rubidium atomic frequency standard （RAFS）, which does not require fractional frequen...In this paper, we analyze and design a new type of servo system with noninteger voltage controlled crystal oscillator （VCXO） for rubidium atomic frequency standard （RAFS）, which does not require fractional frequency synthesizer. By the estab- lishment of the loop equations with noises and drifts, we prove that all the components of the loop can affect its performance in- dex, and in which, RAFS long-term frequency stability is mainly determined by frequency multiplier, quantum system, and servo amplifier; the short-term one is mostly decided by VCXO. Owing to the elimination of the frequency synthesizer and its additive mixing unit, we can reduce phase noise and stray of the servo sys- tem, and it is favorable for miniaturizing the RAFS system. In addition, we adopt some targeted optimization measures to im- prove the frequency stability index. The good short-term fre- quency stability index is also validated by the test results.展开更多
To obtain frequency-temperature compensation in a sapphire loaded cavity for hydrogen maser, a dielectric named SrTiO3 is employed whose temperature coefficient of permittivity is opposite to that of sapphire. Based o...To obtain frequency-temperature compensation in a sapphire loaded cavity for hydrogen maser, a dielectric named SrTiO3 is employed whose temperature coefficient of permittivity is opposite to that of sapphire. Based on theoretical analysis and computer simulation, a TE011 mode of a sapphire loaded cavity associated with two small rings of SrTiO3 with different thickness is solved, and the useful parameters that influence the temperature coefficient of cavity are calculated. Finally an experiment is brought forward and its results are very close to the computing results. When the thickness of SiTiO3 dielectric is 7 mm and the diameter is 17 mm in configuration b, the temperature coefficient of cavity is decreased from -58.8 kHz/K to -8.2 kHz/K and the quality factor is 40248.展开更多
介绍一种基于压缩SF6气体绝缘的正立式标准电容器的,可测量600 k V工频电压,1 200 k V冲击电压。使用有限元分析软件ANSOFT对高压套管进行仿真计算,套管的接地屏蔽以及中间电位屏蔽的位置和尺寸进行优化设计。中间电位屏蔽上的电压系数k...介绍一种基于压缩SF6气体绝缘的正立式标准电容器的,可测量600 k V工频电压,1 200 k V冲击电压。使用有限元分析软件ANSOFT对高压套管进行仿真计算,套管的接地屏蔽以及中间电位屏蔽的位置和尺寸进行优化设计。中间电位屏蔽上的电压系数k=41.6%时,套管利用率最佳。对于电极的设计,依据电场大小确定高压电极的直径和上下圆弧的尺寸,不断优化屏蔽电极的尺寸,尽可能均匀低压电极表面的电场强度。雷电冲击耐受电压1 440 k V下,装置壳体内部最大电场为18.1 k V/mm。为了改善标准电容器的频率特性,设计时低压电极与外壳内壁的距离仅15 mm。根据标准电容器的尺寸和材料,计算得到温度系数为2.05×10^(-5)/K,600 k V时的电压系数为5.5×10^(-7),偏心引起的电容量变化为3.95×10^(-5),为电极安装之后的固定误差。展开更多
针对小型化高精度铷原子频标应用需求,设计了体积为11 m L的小型化开槽管微波腔.实验测量了微波腔内微波场的方向因子,结果为0.83.利用该微波腔设计了小型化铷频标物理系统,形成了铷频标桌面系统.测试了系统的短期频率频率稳定度,结果优...针对小型化高精度铷原子频标应用需求,设计了体积为11 m L的小型化开槽管微波腔.实验测量了微波腔内微波场的方向因子,结果为0.83.利用该微波腔设计了小型化铷频标物理系统,形成了铷频标桌面系统.测试了系统的短期频率频率稳定度,结果优于2×10^(-12)/τ^(1/2),远高于一般商用小型化铷原子频标.展开更多
文摘A compact direct digital frequency synthesizer （DDFS） for system-on-chip implementation of the high precision rubidium atomic frequency standard is developed. For small chip size and low power consumption, the phase to sine mapping data is compressed using sine symmetry technique, sine-phase difference technique, quad line approximation technique,and quantization and error read only memory （QE-ROM） technique. The ROM size is reduced by 98% using these techniques. A compact DDFS chip with 32bit phase storage depth and a 10bit on-chip digital to analog converter has been successfully implemented using a standard 0.35μm CMOS process. The core area of the DDFS is 1.6mm^2. It consumes 167mW at 3.3V,and its spurious free dynamic range is 61dB.
文摘In this paper, we analyze and design a new type of servo system with noninteger voltage controlled crystal oscillator （VCXO） for rubidium atomic frequency standard （RAFS）, which does not require fractional frequency synthesizer. By the estab- lishment of the loop equations with noises and drifts, we prove that all the components of the loop can affect its performance in- dex, and in which, RAFS long-term frequency stability is mainly determined by frequency multiplier, quantum system, and servo amplifier; the short-term one is mostly decided by VCXO. Owing to the elimination of the frequency synthesizer and its additive mixing unit, we can reduce phase noise and stray of the servo sys- tem, and it is favorable for miniaturizing the RAFS system. In addition, we adopt some targeted optimization measures to im- prove the frequency stability index. The good short-term fre- quency stability index is also validated by the test results.
文摘To obtain frequency-temperature compensation in a sapphire loaded cavity for hydrogen maser, a dielectric named SrTiO3 is employed whose temperature coefficient of permittivity is opposite to that of sapphire. Based on theoretical analysis and computer simulation, a TE011 mode of a sapphire loaded cavity associated with two small rings of SrTiO3 with different thickness is solved, and the useful parameters that influence the temperature coefficient of cavity are calculated. Finally an experiment is brought forward and its results are very close to the computing results. When the thickness of SiTiO3 dielectric is 7 mm and the diameter is 17 mm in configuration b, the temperature coefficient of cavity is decreased from -58.8 kHz/K to -8.2 kHz/K and the quality factor is 40248.
文摘介绍一种基于压缩SF6气体绝缘的正立式标准电容器的,可测量600 k V工频电压,1 200 k V冲击电压。使用有限元分析软件ANSOFT对高压套管进行仿真计算,套管的接地屏蔽以及中间电位屏蔽的位置和尺寸进行优化设计。中间电位屏蔽上的电压系数k=41.6%时,套管利用率最佳。对于电极的设计,依据电场大小确定高压电极的直径和上下圆弧的尺寸,不断优化屏蔽电极的尺寸,尽可能均匀低压电极表面的电场强度。雷电冲击耐受电压1 440 k V下,装置壳体内部最大电场为18.1 k V/mm。为了改善标准电容器的频率特性,设计时低压电极与外壳内壁的距离仅15 mm。根据标准电容器的尺寸和材料,计算得到温度系数为2.05×10^(-5)/K,600 k V时的电压系数为5.5×10^(-7),偏心引起的电容量变化为3.95×10^(-5),为电极安装之后的固定误差。
文摘针对小型化高精度铷原子频标应用需求,设计了体积为11 m L的小型化开槽管微波腔.实验测量了微波腔内微波场的方向因子,结果为0.83.利用该微波腔设计了小型化铷频标物理系统,形成了铷频标桌面系统.测试了系统的短期频率频率稳定度,结果优于2×10^(-12)/τ^(1/2),远高于一般商用小型化铷原子频标.
