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## A Guide to the FFT-2nd Edition Plus

version 1.1 (147 KB) by

A guide to the use of the fft algorithm.

4.28571
21 Ratings

Updated

The fft of 3 functions are compared with their analytic transforms. The method proposal produce results that are super imposable with the theoretical predictions.
Odd and even number of points are considered.
(The algorithm works correctly in both cases).

Dimitar

### Dimitar (view profile)

I get same results when using
X1=fftshift(fft(fftshift(x1)));
X2=fftshift(fft(fftshift(x2)));
X=X1+X2;
xo = ifftshift(ifft(ifftshift(X)))
OR
X1=(fft((x1)));
X2=(fft((x2)));
X=X1+X2;
xo = (ifft((X)))

My intervals are symmetric and power of 2.
Are these correct and is this normal in matlab 2013b?

Why do we need to use fftshift twice?

How about power measurement? What is the correct way plot the power of the signal after using this algorithm. I'm using modulated periodic signal.

b3824855

### b3824855 (view profile)

Thank you very much! This is exactly what I was looking for.

shan Kou

### shan Kou (view profile)

its very good - explains finally why we need fftshift twice. However, it should be stressed that the method works only for data of even size. For odd size data, the amplitude is correct but spectral phase will be wrong.

shan Kou

### shan Kou (view profile)

Robert Kariniemi

Excellent description of the theory of the FFT.
But my code threw up errors...cannot define functions at this point?? Could not run it now. I will have to look into it a little.

li taotao

Great,I like this file very much

Fabrice Chane-Ming

M. Ashrith Kumar

its very good !! but slightly need for improvement

B. Roossien

It's a good start, but the script contains the "clear all" and "close all" commands, which is a very bad habit to do.

Andrey Worobey

Thanks so much man!!!

I have been looking for the solution for a year!

Vishnuvenkatesh Dhage

Yani Jerome

I've found FourierTransform.m (ID 13327) very usefull too

you you

ilaria eos

michel sebes

ISABEL CRISTINA GOMEZ

Gracias

Wynn Ko Ko

Need to be improved.

Gunasekaran Shanmgam

Gives nice overview of all FFT's

this is a good file for the users also beginers for filter designers thanks for the support

srinu jella

u guys r impoptant for students like us. because we are in the initial stage of learning.we can learn from u .

ding ding

very useful to a novice like me!
3q

peng peng

helpful for student as me !

Robert Chen

It's very useful to me.
Thank you very much!