Horizontal Local-Squeezing Frequency-Domain Chirplet Transform
Dezun Zhao, Shu Du, Tianyang Wang · IEEE Transactions on Instrumentation and Measurement · 2025
Calculating the group delay (GD) and reassigning amplitude coefficients for transient signals are crucial in time-frequency analysis (TFA) theory. The definition-based GD calculation brings the non-reassigned points problem, and the synchrosqueezing transform (SST) is susceptible to noise interference due to the uncertainty of the squeezing boundary. Therefore, a novel TFA method termed horizontal local-squeezing frequency domain chirplet transform (HLSFCT) is developed. In the HLSFCT, a GD estimation criterion is first designed on the basis of the geometrical characteristic of the chirplet transform (CT) window function and its derivative, which solves the problem of non-reassigned points. Then, a squeezing boundary calculation algorithm is constructed to eliminate noise interference, and it is implemented by the local maximum location of the absolute value of the first-order derivative of the CT window function and the local minimum location of the absolute value of its second-order derivative. Finally, a frequency domain local-squeezing operator is designed to adaptively obtain time-frequency coefficients on the GD trajectory based on a GD estimation criterion and boundary conditions. The effectiveness of the HLSFCT in energy concentration and noise robustness is verified against the state-of-the-art results on a simulated multicomponent transient signal and two different bearing fault signals.