Instantaneous frequency (IF) estimation based on Two-step method introduced in:
"A Two-Step Procedure for Estimation of Instantaneous Rotational Speed With Large Fluctuations, Urbanek, T. Barszcz, J. Antoni, Mechanical Systems and Signal Processing 38 (1) , pp. 96-102"
Copyright: Jacek Urbanek, PhD, 2013
x - time signal
fs - sampling frequency [Hz]
win - time window length [s]
df - frequency window width for filtration [Hz]
overlap - time window overlap [%] (0 - 100%)
start - starting point for the estimation [Hz]
tol - tolerance for time-frequency IF estimation [Hz]
For exemplary signal:
For improved results try to manipulate "df" and "tol" parameters. You might also change spectrogram options.
For manual selection of starting frequency use the attached spectrogram_JU code.