HOW CAN I PLOT A CURVE OVER THE SPECTROGRAM OF A LOGARITHMIC CHIRP

I want to represent the true frequency of a logarithmic chirp. So I want to plot a curve over the spectrogram plane can you help me with this??

[Buba]

See the link below for guide

https://www.mathworks.com/help/signal/ref/spectrogram.html

Answer 1

[William Rose]

@raj,

YOu can follow the spectrogram command with "hold on" and then make additinal plots on the same image.

[William Rose]

@raj,

For example:

t = 0:1/1e3:10;     %time vector (s)
f0=10;  f1=400;     %start, end frequencies (Hz)
y = chirp(t,f0,t(end),f1,'logarithmic');
pspectrum(y,t,'spectrogram')        %compute and plot spectrogram of the chirp 
ax=gca; ax.YScale = 'log';          %make y axis log scale

Now add a plot of the expected frequency versus time

%Next: compute expected frequency versus time
fexp=f0*exp((t/t(end))*log(f1/f0));     %expected frequency
hold on; plot(t,fexp,'-r')              %plot expected freq. vs. time