后向投影(back projection,BP)成像算法能够适应非均匀孔径,但是其运算效率过低限制了其工程应用。很多学者基于子孔径划分的原理提出了不少改进的快速后向投影(fast back projection,FBP)算法,但是目前对于子孔径划分后如何进行运动补...后向投影(back projection,BP)成像算法能够适应非均匀孔径,但是其运算效率过低限制了其工程应用。很多学者基于子孔径划分的原理提出了不少改进的快速后向投影(fast back projection,FBP)算法,但是目前对于子孔径划分后如何进行运动补偿还未有深入研究。就不同的运动情况对FBP算法的运动补偿进行了研究,包括最简单的仅有方位向误差的直线运动补偿,同时存在方位向和距离向运动误差的情况,到存在有意机动的曲线航迹,最后提出了一套完整的基于传感器测量的任意孔径快速后向投影成像算法。实测数据处理结果证明了所提的算法能够适应不同运动情况进行快速成像。展开更多
在直接序列扩频(DSSS)通信对抗系统中,伪码(PN)序列估计是一个重要的研究课题。针对在某些情况下权值向量不收敛的问题,提出了一种基于快速正交投影逼近子空间跟踪(OPAST)算法和滑动窗技术的直扩信号PN码序列估计算法,对非同步接收DSSS...在直接序列扩频(DSSS)通信对抗系统中,伪码(PN)序列估计是一个重要的研究课题。针对在某些情况下权值向量不收敛的问题,提出了一种基于快速正交投影逼近子空间跟踪(OPAST)算法和滑动窗技术的直扩信号PN码序列估计算法,对非同步接收DSSS信号按照宽窗口分段,利用快速OPAST算法提取主特征向量,滑动窗技术实现码同步。该算法迭代权值向量具有正交性以及良好的收敛性,同时解决了常见相位模糊问题。算法具有较低复杂度,数据存储量少,易于硬件实现与实时处理。仿真结果表明,在-10 d B的较低信噪比背景环境中,该快速OPAST算法可以正确有效地估计出PN码序列。展开更多
Fast neutron spectrometers will play an important role in the future of the nuclear industry and nuclear physics experiments, in tasks such as fast neutron reactor monitoring, thermo-nuclear fusion plasma diagnostics,...Fast neutron spectrometers will play an important role in the future of the nuclear industry and nuclear physics experiments, in tasks such as fast neutron reactor monitoring, thermo-nuclear fusion plasma diagnostics,nuclear reaction cross-section measurement, and special nuclear material detection. Recently, a new fast neutron spectrometer based on a GEM（Gas Electron Multiplier amplification）-TPC（Time Projection Chamber）, named the neutron-TPC, has been under development at Tsinghua University. It is designed to have a high energy resolution,high detection efficiency, easy access to the medium material, an outstanding n/γ suppression ratio, and a wide range of applications. This paper presents the design, test, and experimental study of the neutron-TPC. Based on the experimental results, the energy resolution（FWHM） of the neutron-TPC can reach 15.7%, 10.3% and 7.0% with detection efficiency higher than 10^-5 for 1.2 Me V, 1.81 Me V and 2.5 Me V neutrons respectively.展开更多
文摘后向投影(back projection,BP)成像算法能够适应非均匀孔径,但是其运算效率过低限制了其工程应用。很多学者基于子孔径划分的原理提出了不少改进的快速后向投影(fast back projection,FBP)算法,但是目前对于子孔径划分后如何进行运动补偿还未有深入研究。就不同的运动情况对FBP算法的运动补偿进行了研究,包括最简单的仅有方位向误差的直线运动补偿,同时存在方位向和距离向运动误差的情况,到存在有意机动的曲线航迹,最后提出了一套完整的基于传感器测量的任意孔径快速后向投影成像算法。实测数据处理结果证明了所提的算法能够适应不同运动情况进行快速成像。
文摘在直接序列扩频(DSSS)通信对抗系统中,伪码(PN)序列估计是一个重要的研究课题。针对在某些情况下权值向量不收敛的问题,提出了一种基于快速正交投影逼近子空间跟踪(OPAST)算法和滑动窗技术的直扩信号PN码序列估计算法,对非同步接收DSSS信号按照宽窗口分段,利用快速OPAST算法提取主特征向量,滑动窗技术实现码同步。该算法迭代权值向量具有正交性以及良好的收敛性,同时解决了常见相位模糊问题。算法具有较低复杂度,数据存储量少,易于硬件实现与实时处理。仿真结果表明,在-10 d B的较低信噪比背景环境中,该快速OPAST算法可以正确有效地估计出PN码序列。
基金Supported by National Natural Science Foundation of China(11275109)
文摘Fast neutron spectrometers will play an important role in the future of the nuclear industry and nuclear physics experiments, in tasks such as fast neutron reactor monitoring, thermo-nuclear fusion plasma diagnostics,nuclear reaction cross-section measurement, and special nuclear material detection. Recently, a new fast neutron spectrometer based on a GEM（Gas Electron Multiplier amplification）-TPC（Time Projection Chamber）, named the neutron-TPC, has been under development at Tsinghua University. It is designed to have a high energy resolution,high detection efficiency, easy access to the medium material, an outstanding n/γ suppression ratio, and a wide range of applications. This paper presents the design, test, and experimental study of the neutron-TPC. Based on the experimental results, the energy resolution（FWHM） of the neutron-TPC can reach 15.7%, 10.3% and 7.0% with detection efficiency higher than 10^-5 for 1.2 Me V, 1.81 Me V and 2.5 Me V neutrons respectively.
