针对磁共振射频脉冲的时频域分析方法比较研究

Comparison of Time-Frequency Analysis Methods for Radio Frequency Pulses Used in Magnetic Resonance

射频脉冲可实现样本自旋体系的精确操控,进而产生预期的核磁共振(NMR)信号,在NMR信号产生过程中扮演重要角色.该文分别采用短时傅里叶变换(STFT)、连续小波变换(CWT)和维格纳-威利分布(WVD)几种时频域分析方法对射频脉冲(优化形状脉冲)进行特性分析和比较.结果表明,三种方法各自具有优缺点,结合各自优势对射频脉冲进行各种方法分析,可以更好地理解复杂脉冲的幅度、相位特性在时频域的分布情况.该文的研究方法将为直观理解复杂射频脉冲对自旋体系的作用机制提供参考.

Accurate manipulation of spin systems can be achieved by radio frequency （RF） pulses, which play a key role in nuclear magnetic resonance （NMR）. This paper analyses the time-frequency characteristics of RF pulses, such as the optimal shaped pulse, using different time-frequency analysis methods such as short-time Fourier transform （STFT）, continuous wavelet transform （CWT） and Wigner-Ville distribution （WVD）. The performances of these methods were then compared. The results indicated that combination of the above methods may achieve a better performance in analyzing the amplitude and phase distribution of complex RF pulse in joint time-frequency domain. The research provides a reference for understanding of the effects of complex RF pulses on specific spin systems.