Should I use the absolute value of fast Fourier transform or the conjugate in signal analysis?

100 views (last 30 days)
I found this example in MATLAB and I saw that they used the value of conjugate.
Pyy = Y.*conj(Y)/251;
I tried to calculate the magnitude using abs function rather than this line. I get nearly the same output.
Therefore, I am puzzled; should I use the way in this example or the magnitude way?

Accepted Answer

Star Strider
Star Strider on 18 Nov 2020
Note that the plot is ‘Power Spectral Density’. Power is the square of magnitude.
The abs value is the square root of the complex value times its conjugate.
Star Strider
Star Strider on 23 Nov 2020
As always, my pleasure!
The second argument is not necessary. The fft function will use the row length of the argument to determine the row length of the output. The second argument is only necessary if you want to zero-pad the inplut in order to increase the frequency resolution of the output.

Sign in to comment.

More Answers (1)

Bruno Luong
Bruno Luong on 18 Nov 2020
Y.*conj(Y) is abs(Y)^2


Find more on Loops and Conditional Statements in Help Center and File Exchange




Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!