Effect of amplitude variation on instantaneous frequency estimation

The effect of amplitude variation on instantaneous frequency (IF) estimation is studied. Theoretical analysis shows that the estimation on the linear frequency modulated (LFM) signals with time-varying amplitude is unbiased, only if the Wigner-Ville distribution (WVD) of time-varying amplitude reaches its maximum at zero frequency no matter in which time, which extends the scope of using the peak of WVD to estimate IF. The simulations using LFM signals with Gaussian envelope testify that IF can be accurately estimated using the peak of WVD. Furthermore, the statistical result of estimation on the signals with amplitude descending before rising is better than that of the signals with constant amplitude when the amplitude variation rate is moderate.