特形脉冲的设计与计算机模拟  

The design and computer simulation of a shaped pulse

作　　者：许峰[1] 黄永仁[2] 

机构地区：[1]安徽理工大学数理系,淮南232001 [2]光谱学与波谱学教育部重点实验室,华东师范大学物理系,上海200062

出　　处：《物理学报》2002年第11期2617-2622,共6页Acta Physica Sinica

基　　金：安徽省教育厅自然科学基金 (批准号 :2 0 0 1KJ2 2 5ZC)资助的课题

摘　　要：根据Liouville vonNeumann方程从理论上对特形脉冲做了全面的描述 ,提出了一种具体的调幅特形脉冲设计方案 :首先将待设计的脉冲展成一个有限Fourier级数 ,然后根据Bloch方程的解析解准确计算出各阶正弦、余弦波的频谱 ,再将这些频谱组合后与该脉冲的理想频谱进行比较构成误差函数 ,最后运用鲍威尔 -模拟退火组合优化算法计算出全局最优Fourier系数 ,即可得到所需脉冲的表达式 .应用此设计方案 ,得到了体系处于热平衡态时的特形激励脉冲和反转脉冲的具体表达式 .计算机模拟表明 。An overall theoretical description of a shaped pulse is given, and a concrete design scheme of a shaped pulse is presented: A desired shaped pulse is expanded as a finite Fourier series and its frequency domain profile is calculated. according to the analytical solutions of Bloch equations. The profile is compared with the desired target profile to give a multidimensional error function. The Powell-simulated annealing optimization algorithm is then used to find the global minimum on this function. Finally, the desired shaped pulse is gained. In this manner, a shaped excitation pulse and a shaped inverse pulse in common use of NMR are designed. The simulation results show that these pulses have good selectivity and the excitation can be guaranteed to be uniform across the effective bandwidth and of a constant phase.

关 键 词：设计 计算机模拟 核磁共振 特形脉冲 BLOCH方程 鲍威尔-模拟退火组合优化算法 

分 类 号：O482.532[理学—固体物理] TN78[理学—物理]