Synchronous sampling is very essential in underwater multilinear array seismic exploration system in which every acquisition node(AN)samples analog signals by its own analog-digital converter(ADC).Aiming at the proble...Synchronous sampling is very essential in underwater multilinear array seismic exploration system in which every acquisition node(AN)samples analog signals by its own analog-digital converter(ADC).Aiming at the problems of complex synchronous sampling method and long locking time after varying sampling rate in traditional underwater seismic exploration system,an improved synchronous sampling model based on the master-slave synchronous model and local clock asynchronous drive with non phase locked loop(PLL)is built,and a high-precision synchronous sampling method is proposed,which combines the short-term stability of local asynchronous driving clock with the master-slave synchronous calibration of local sampling clock.Based on the improved synchronous sampling model,the influence of clock stability,transmission delay and phase jitter on synchronous sampling error is analyzed,and a high-precision calibration method of synchronous sampling error based on step-by-step compensation of transmission delay is proposed.The model and method effectively realize the immunity of phase jitter on synchronous sampling error in principle,and compensate the influence of signal transmission delay on synchronous sampling error.At the same time,it greatly reduces the complexity of software and hardware implementation of synchronous sampling,and solves the problem of long locking time after changing the sampling rate in traditional methods.The experimental system of synchronous sampling for dual linear array is built,and the synchronous sampling accuracy is better than 5 ns.展开更多
The Electro-optical sampling delay scanning technique can be used for electron beam bunch length measurement. A novel non-synchronous delay scanning technique based on the electro-optical sampling measurements is pres...The Electro-optical sampling delay scanning technique can be used for electron beam bunch length measurement. A novel non-synchronous delay scanning technique based on the electro-optical sampling measurements is presented. Based on Beijing Free Electron Laser （BFEL）, the electron beam bunch length was measured with the electro-optical sampling technique for the first time in China. The result shows that the electron beam bunch length at BFEL is about 5.6±1.2 ps.展开更多
数字化变电站采用固定采样频率10 k Hz采样数据,每周期采样点数为200,不为2的整数次幂;且基波频率的波动会导致非同步采样,直接运用离散傅里叶或快速傅里叶变换分析谐波,会对测量结果产生较大误差,不满足电力系统谐波分析精度的要求。...数字化变电站采用固定采样频率10 k Hz采样数据,每周期采样点数为200,不为2的整数次幂;且基波频率的波动会导致非同步采样,直接运用离散傅里叶或快速傅里叶变换分析谐波,会对测量结果产生较大误差,不满足电力系统谐波分析精度的要求。算术傅里叶变换(AFT)算法简单且并行性好,对计算点数无限制,适用于分析离散信号的频谱。但该算法需要不均匀的采样点,目前电力系统所得到的是均匀采样的数据,因此运用AFT时需先对均匀采样的离散信号进行插值,而插值过程将不可避免地引入误差,影响到AFT算法的谐波分析精度。AFT常用的插值算法为零次插值,此方法存在较大误差,严重影响谐波分析精度,不能满足电力系统的要求。对比了四种平面插值算法,通过仿真分析比较了这四种方法对AFT谐波分析精度的影响。最后选用三次样条插值算法来提高AFT的谐波分析精度。仿真结果表明:在非同步采样条件下,用三次样条插值的AFT谐波分析方法精确度高,稳定性好,满足谐波分析精度的要求,为电力系统谐波分析开辟了新思路。展开更多
基金National Key Research and Development Program of China(No.2018YFE0208200)National Natural Science Foundation of China(Nos.61971307,61905175,51775377)+5 种基金National Key Research and Development Plan Project(No.2020YFB2010800)The Fok Ying Tung Education Foundation(No.171055)China Postdoctoral Science Foundation(No.2020M680878)Guangdong Province Key Research and Development Plan Project(No.2020B0404030001)Tianjin Science and Technology Plan Project(No.20YDTPJC01660)Project of Foreign Affairs Committee of China Aviation Development Sichuan Gas Turbine Research Institute(Nos.GJCZ-2020-0040,GJCZ-2020-0041)。
文摘Synchronous sampling is very essential in underwater multilinear array seismic exploration system in which every acquisition node(AN)samples analog signals by its own analog-digital converter(ADC).Aiming at the problems of complex synchronous sampling method and long locking time after varying sampling rate in traditional underwater seismic exploration system,an improved synchronous sampling model based on the master-slave synchronous model and local clock asynchronous drive with non phase locked loop(PLL)is built,and a high-precision synchronous sampling method is proposed,which combines the short-term stability of local asynchronous driving clock with the master-slave synchronous calibration of local sampling clock.Based on the improved synchronous sampling model,the influence of clock stability,transmission delay and phase jitter on synchronous sampling error is analyzed,and a high-precision calibration method of synchronous sampling error based on step-by-step compensation of transmission delay is proposed.The model and method effectively realize the immunity of phase jitter on synchronous sampling error in principle,and compensate the influence of signal transmission delay on synchronous sampling error.At the same time,it greatly reduces the complexity of software and hardware implementation of synchronous sampling,and solves the problem of long locking time after changing the sampling rate in traditional methods.The experimental system of synchronous sampling for dual linear array is built,and the synchronous sampling accuracy is better than 5 ns.
基金Supported by National Natural Science Foundation of China (10575116)
文摘The Electro-optical sampling delay scanning technique can be used for electron beam bunch length measurement. A novel non-synchronous delay scanning technique based on the electro-optical sampling measurements is presented. Based on Beijing Free Electron Laser （BFEL）, the electron beam bunch length was measured with the electro-optical sampling technique for the first time in China. The result shows that the electron beam bunch length at BFEL is about 5.6±1.2 ps.
文摘数字化变电站采用固定采样频率10 k Hz采样数据,每周期采样点数为200,不为2的整数次幂;且基波频率的波动会导致非同步采样,直接运用离散傅里叶或快速傅里叶变换分析谐波,会对测量结果产生较大误差,不满足电力系统谐波分析精度的要求。算术傅里叶变换(AFT)算法简单且并行性好,对计算点数无限制,适用于分析离散信号的频谱。但该算法需要不均匀的采样点,目前电力系统所得到的是均匀采样的数据,因此运用AFT时需先对均匀采样的离散信号进行插值,而插值过程将不可避免地引入误差,影响到AFT算法的谐波分析精度。AFT常用的插值算法为零次插值,此方法存在较大误差,严重影响谐波分析精度,不能满足电力系统的要求。对比了四种平面插值算法,通过仿真分析比较了这四种方法对AFT谐波分析精度的影响。最后选用三次样条插值算法来提高AFT的谐波分析精度。仿真结果表明:在非同步采样条件下,用三次样条插值的AFT谐波分析方法精确度高,稳定性好,满足谐波分析精度的要求,为电力系统谐波分析开辟了新思路。
