Characterizing nonstationary signals with widely changing instantaneous frequency features is a challenging issue for time-frequency analysis (TFA) method. A novel TFA method termed second-order synchroextracting wavelet transform (SSEWT) is proposed for this purpose. The method extends the existing synchroextracting transform to the context of wavelet transform, and introduces the second-order instantaneous frequency estimate to improve its capability of processing nonstationary signals. The proposed method provides concentrated time-frequency representation with multiple resolutions, and retains good invertibility. The theories concerned and discrete implementation of the SSEWT are presented. Numerical simulations and experimental data collected from rotating machinery are employed to verify the competitive advantages of the SSEWT in revealing the local time-frequency features of nonstationary signals.

对于瞬时频率特征变化很大的非平稳信号进行表征是时频分析（TFA）方法面临的挑战。为此，提出了一种新颖的TFA方法，称为二阶同步提取小波变换（SSEWT）。该方法将现有的同步提取变换扩展到小波变换的上下文中，并引入了二阶瞬时频率估计，以提高其处理非平稳信号的能力。所提出的方法提供了具有多种分辨率的集中的时频表示，并且保持了良好的可逆性。介绍了相关理论和SSEWT的离散实现。