基于小波变换估计的超声多普勒血流频谱中频带展宽及修正

利用脉冲多普勒技术检测血流时，信号的频谱带宽是诊断疾病的重要依据之一。与传统的短时傅立叶变换比较，小波变换使用了不同宽度的函数窗，具有多分辨能力，对多普勒血流信号频谱的估计可以获得更精确的时频分辨率。但是，基于小波变换的频谱带宽中仍然包含有分析窗口和信号自身非平稳性引入的误差。本研究针对小波变换中窗口宽度变化的多分辨特点，给出了窗口效应和信号非平稳性频谱均方根带宽的表达式，提出了两种修正频谱带宽中窗口和非平稳展宽误差的方法。通过对模拟多普勒信号的修正实验，两种方法都取得了很好的修正效果。

Estimation of the Correct Wavelet Transform-Based Doppler Blood Flow Spectral Broadening

Wavelet transform(WT) has proved to be some improvements in time-frequency resolution for analyzing Doppler blood flow signals over the short time Fourier transform(STFT).However,the estimated spectral width of Doppler blood flow signals using the WT might include significant window and nonstationarity broadening errors.These errors are undesirable since it would tend to mask the effect of flow disturbance on the spectra width.In this paper,two methods for correction of window and nonstationary root-mean-squared(RMS) spectral width are proposed for the Doppler blood flow spectrum estimated using the WT.From the simulation study,it is found that both two methods have good correction performances.