Plotting Power Spectrum Density in Matlab

[yongs90]

Homework Statement

I have an autocorrelation function given by
R([itex]\tau[/itex]) = [itex]J_0[/itex](2[itex]\pi[/itex][itex]f_d[/itex][itex]\tau[/itex])

I have already plotted it in Matlab using the following commands
ts=0.0000001;
fs=1/ts;
fd=100;

tau=0:0.0000001:0.05;
R=besselj(0,2*pi*fd.*tau);

How do I plot its PSD in Matlab and the plotted picture looks like this:
http://www.mypicx.com/09032011/Temp/

Homework Equations

The Attempt at a Solution

When I use the command pwelch(R), it just won't yield the picture.
http://www.mypicx.com/09032011/blabla/

I will obtain something different. How do I scale it so that I will resemble the picture given. thanks

 

[KataKoniK]

Hello,

In order to plot the PSD (power spectral density) of your autocorrelation function in Matlab, you can use the command pwelch as you have mentioned. However, in order to obtain a plot similar to the one given in the forum post, you will need to specify the sampling frequency and the window length for the pwelch command.

The sampling frequency can be specified by using the 'Fs' parameter, and the window length can be specified by using the 'N' parameter. For example, you can use the following command to obtain a similar plot:

pwelch(R,[],[],[],fs,'onesided')

The 'onesided' parameter ensures that only the positive frequencies are plotted, which is the case in the given picture. You can also play around with the 'N' parameter to obtain a smoother or more detailed plot.

I hope this helps. Let me know if you have any further questions.