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The fast Fourier transform is an efficient algorithm to compute the discrete Fourier transform (DFT) and its inverse.

1
vote
4answers
I just got a thought when generating matrices , plotting it and taking its FFT, Lets say, I have randomly input a matrix of length 256, [1 7 9 5 7 1 -2 0..................8] According to the FFT, the … resulting 256 FFT coefficients correspond to the following frequencies: 0, $f_s/256$, $2 f_s/256$, $3 f_s/256$, $\ldots$, $255 f_s/256$ but since the samples i taken has no sampling frequency defined …
asked Oct 21 '12 by Sufiyan Ghori
0
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2answers
After getting suggestion to first study FFT on square wave to understand FFT of discrete signal, I'm trying to understand the FFT of square wave. … x=square(2*pi*f*n); subplot(2,1 ,1) stem(n,x) Output wave, Now plotting its FFT subplot(2,1 ,2) F=fft(x) plot(2*abs(F). …
asked Oct 21 '12 by Sufiyan Ghori
0
votes
1answer
I plotted a simple Cosine wave and After taking its FFT the frequency can be seen easily but after modifying the original signal to add more lower and higher frequencies, the higher ones are visible but … the original signal and supposed to be plotted at point 5 of the FFt. …
asked Oct 21 '12 by Sufiyan Ghori
0
votes
2answers
When we plot FFT in a matlab it doesn't ask for Frequency , all we need to input the sequence and it simply shows the output using stem command. … Here is simple code for the FFT calculation , x=[1 2 1 0] n=0:3 y=fft(x) subplot(2,2,1) stem(n,y) …
asked Aug 29 '12 by Sufiyan Ghori
5
votes
Even i had confusion differentiating between these two terms at the beginning , have a look at this explanation from one of the Award winning DSP books. Amplitudes, Magnitudes,
answered Mar 21 '13 by Sufiyan Ghori
2
votes
1answer
In case of 1-D FFT it is far more easier to find number of harmonics and their Respective frequencies and amplitudes. …
asked Sep 30 '12 by Sufiyan Ghori
3
votes
1answer
8.0000 -4.0000 + 4.0000i 0 -4.0000 - 4.0000i If i calculate the fft instead of fft2 it will give the following output %FFT -> DFT of Vector %FFT2 -> DFT of Matrix 0 …
asked Sep 25 '12 by Sufiyan Ghori
1
vote
1answer
So, when we Sampled any signal at the rate lower than Nyquist Frequency we get aliasing, for instance, If the frequency of Cosine wave is 5Hertz and I had to make 5cycles in a second and if the sampl …
asked Sep 29 '12 by Sufiyan Ghori
3
votes
2answers
, and If we are plotting the 10 Oscillations i.e t = 10/f then the length of the Signal would be 100. and If we plot the FFT of that signal than the First point in FFT represent 10KHz i.e 1MHz/100 = 10KHz … the FFT plot ! …
asked Sep 28 '12 by Sufiyan Ghori
4
votes
3answers
I am having trouble identifying the frequency components of an image, Here I simply generated, 256x256 binary-image. a = [zeros(256,128) ones(256,128)]; imshow(a); Taking the image FFT and shifting the … Also if I calculate FFT of any 1-D sequence and plot that sequence there are certain values on negative, what does that mean? How could there be negative frequencies? …
asked Sep 25 '12 by Sufiyan Ghori
7
votes
2answers
How does the Amplitude of the Signal is changed when taking the FFT of a Signal, Have a look, The amplitude had changed from 2 to 30, and Here is my code for generating the above output, f=1e3; … = 100Hz % 2nd Point = 200Hz % 3rd Point = 300Hz % 4th Point = 400Hz % . % . % 10th Point = 1KHz <- Original Signal Frequency subplot(2,1 ,2) F=fft(x); plot(real((F))),grid on xlim ([0 20]) …
asked Sep 27 '12 by Sufiyan Ghori