An improved signal-dependent QTFD based on iterative regional RGK optimization for multi-component LFM signals.

•The proposed IRRGD method can resolve strong and weak components of multi-component LFM signals under a proper trade-off between auto-term resolution and cross-term suppression in the TFD.•The proposed IRRGD reduces two major distortions of the original RGD: distortions parallel to the IF of the signals and the energy extension distortions at the birth and death time of signals.•The proposed method for detecting the number of LFM components can be easily extended and generalized to improve other signal-dependent QTFDs.