基于瞬时频率的窗宽递增寻优的短时傅里叶变换

讨论了窗函数在时频分析中的作用,分析了S变换的缺陷,指出了依据分析频率调整窗宽和使用窄窗均严重影响时频分析效果.以短时傅里叶变换为基础,提出了一种窗宽根据信号自身时变特征进行自主调节的时频分析方法,该方法以瞬时频率的变化作为判断信号频谱结构发生变化的依据,通过在瞬时频率变化之前逐次递增窗宽,使窗函数能够覆盖信号中的局部平稳区域的大部甚至全部,从而可对信号中的各局部平稳段得到最佳的时频分辨率.通过对线调频信号、时变信号和含噪声信号的分析和比较可知,本方法可准确描述信号的时间分布特征,并可同时获得最佳的频率分辨率,且对噪声不敏感,具有一定的先进性和实用性.

A Novel STFT of Window Duration Increasing Optimization Based on Instantaneous Frequency

What role the window function plays in time-frequency analysis and the shortcoming of S transform are discussed.It is revealed that the result of the analysis is affected greatly if the window is narrow or the window duration is adjusted according to the analysis frequency.Based on STFT,a new method of time-frequency analysis is presented,where the window duration is adjusted automatically according to the time-varying characteristic of signal.Taking the change of instantaneous frequency as the criterion for the change of signal spectrum structure,the method can increase window duration before the change of instantaneous frequency so as to cause the window to cover the whole or majority of local stationary signal,thus obtaining the optimum time-frequency resolution for all local of stationary signal.The method proposed applies to analyzing and comparing the chirp signal,time-varying signal and the noisy overlapped signal.The results show that it can exactly represent the time-frequency distribution of signal with optimum time-frequency resolution obtained,and is non-sensitive to noise.The method is therefore regarded as advanced and practical.