Estimation of evolutionary spectrum based on STFT and modified group delay

This paper proposes a new estimator for evolutionary spectrum (ES) based on short time Fourier transform (STFT) and modified group delay (MGD). Here, the STFT enables cross term suppression and the MOD preserves the frequency resolution of the rectangular window. It is applicable to deterministic and random signals generated by time varying systems. The proposed method provides signal to noise ratio enhancement due to the use of MGD. The results indicate that for linear chirp signals and for time varying random process, its frequency resolution is close to that of WVD and better than evolutionary periodogram (EP) and STFT. Further, its noise immunity is better than those of EP and STFT.