为了解决低轨双星时差(Time difference of arrival,TDOA)、频差(Frequency difference of arrival,FDOA)定位精度低这一问题,提出了一种应用虚拟参考站(Virtual reference station,VRS)技术来实现对低轨双星TDOA/FDOA进行精密修正的方...为了解决低轨双星时差(Time difference of arrival,TDOA)、频差(Frequency difference of arrival,FDOA)定位精度低这一问题,提出了一种应用虚拟参考站(Virtual reference station,VRS)技术来实现对低轨双星TDOA/FDOA进行精密修正的方法。该方法利用合作辐射源在未知辐射源附近建立一个物理上并不存在的虚拟参考站,然后再利用此虚拟参考站修正未知辐射源的时频误差。通过仿真分析,VRS处虚拟时差构建误差比虚拟频差构建误差要小,并且VRS对未知辐射源TDOA/FDOA系统误差的修正精度分别可以达到97%和95%。利用修正后的时频差对未知辐射源定位,其定位精度相对于未修正前有极大的提高。展开更多
A novel method for automatic ultra-precision alignment is presented.This method relies on the modified Moiré technique,and alignment marks are used in the form of gratings.The modified Moiré technique can ef...A novel method for automatic ultra-precision alignment is presented.This method relies on the modified Moiré technique,and alignment marks are used in the form of gratings.The modified Moiré technique can effectively improve detecting sensitivity of signals and simplify the control system by using only one pair of laser-Moiré sensors.We present the mathematical model and simulation results of diffracting two gratings.The effect of various parameters on Moiré signals is studied theoretically and experimentally,and the results are found to be consistent.A computer controlled alignment device using one pair of Moiré sensors is designed.The device can achieve a fully automatic precision alignment by the modified Moiré signal.The experimental result shows that the alignment device can obtain the resolution of 5 nm and the positioning accuracy of ±0 5 μm.展开更多
文摘为了解决低轨双星时差(Time difference of arrival,TDOA)、频差(Frequency difference of arrival,FDOA)定位精度低这一问题,提出了一种应用虚拟参考站(Virtual reference station,VRS)技术来实现对低轨双星TDOA/FDOA进行精密修正的方法。该方法利用合作辐射源在未知辐射源附近建立一个物理上并不存在的虚拟参考站,然后再利用此虚拟参考站修正未知辐射源的时频误差。通过仿真分析,VRS处虚拟时差构建误差比虚拟频差构建误差要小,并且VRS对未知辐射源TDOA/FDOA系统误差的修正精度分别可以达到97%和95%。利用修正后的时频差对未知辐射源定位,其定位精度相对于未修正前有极大的提高。
文摘A novel method for automatic ultra-precision alignment is presented.This method relies on the modified Moiré technique,and alignment marks are used in the form of gratings.The modified Moiré technique can effectively improve detecting sensitivity of signals and simplify the control system by using only one pair of laser-Moiré sensors.We present the mathematical model and simulation results of diffracting two gratings.The effect of various parameters on Moiré signals is studied theoretically and experimentally,and the results are found to be consistent.A computer controlled alignment device using one pair of Moiré sensors is designed.The device can achieve a fully automatic precision alignment by the modified Moiré signal.The experimental result shows that the alignment device can obtain the resolution of 5 nm and the positioning accuracy of ±0 5 μm.
