Instantaneous Frequency of Complex Chirp
This example shows how to compute the instantaneous frequency of a signal using the Fourier synchrosqueezed transform.
Generate a chirp with sinusoidally varying frequency content. The signal is embedded in white Gaussian noise and sampled at 3 kHz for 1 second.
fs = 3000; t = 0:1/fs:1-1/fs; x = exp(2j*pi*100*cos(2*pi*2*t))+randn(size(t))/100;
Compute and plot the Fourier synchrosqueezed transform of the signal. Display the time on the x-axis and the frequency on the y-axis.
Find the instantaneous frequency of the signal by extracting the maximum-energy time-frequency ridge of the Fourier Synchrosqueezed transform.
[sst,f] = fsst(x,fs); fridge = tfridge(sst,f);
Overlay the ridge on the transform plot. Convert time to milliseconds and frequency to kHz.
hold on plot(t*1000,fridge/1000,'r') hold off