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13 votes
Accepted

Bandwidth of an entire song

First of all, kudos to you: I appreciate the effort and thinking you've managed to articulate in your question. The DFT is a mathematical tool. As such, the parameters used to compute it can hide or ...
Jdip's user avatar
  • 6,265
9 votes
Accepted

Why doesnt DFT Padding cause sinc like features

The OP is showing very good insight in all the comments stated. A product in the time domain with a rectangular pulse is convolution in the frequency domain with a Sinc. In fact zero padding in time ...
Dan Boschen's user avatar
  • 52.1k
7 votes
Accepted

FFT: Sinewave frequency displacement when zero-padding

(I show only positive frequencies): which is part of the problem here :-) You would get the expected behavior if you used a complex sine, i.e. $x[n] = e^{j2\pi\frac{n}{N}}$ but a sine wave actually ...
Hilmar's user avatar
  • 45.4k
5 votes

Question about zero padding example in Lyons book on Understanding DSP

@gschro, I understand your puzzlement. Find the equation for computing a DTFT, in a textbook or on the Internet, and carefully examine it. In that equation $omega$ is a continuous frequency variable ...
Richard Lyons's user avatar
5 votes
Accepted

Question about zero padding example in Lyons book on Understanding DSP

On the left side of Figure 3-21(a) the discrete 16-sample input sequence is represented by the dots. (The lightly-shaded sinusoidal curve is shown for reference only!) On the right side of Figure 3-21(...
Richard Lyons's user avatar
4 votes

Why doesnt DFT Padding cause sinc like features

@George kirby. I suggest you discard that notion of "multiplying a step function on top of the original signal to form a longer time sequence". I believe such a multiplication is not ...
Richard Lyons's user avatar
2 votes

Why doesnt DFT Padding cause sinc like features

lots of good stuff in the above answer. But you can absolutely see the sinc function in the frequency domain - just pick a sin wave that's got a period that evenly divides the new signal length. For ...
njudell's user avatar
  • 21
2 votes
Accepted

What is wrong with this sinc interpolation? (Zero padding in frequency domain)

Zero padding the frequency samples (just as the OP has done in padding out the center of the array and maintaining symmetry) and using the inverse DFT is almost identical to interpolating with a Sinc ...
Dan Boschen's user avatar
  • 52.1k
1 vote
Accepted

Periodicity problem with FFT for generating "starburst" from aperture

This is not because of lack of padding, or periodicity assumptions. What you are seeing is aliasing. You defined your input image as the sampling of an infinitely sharp object, which has infinitely ...
Cris Luengo's user avatar
  • 2,584
1 vote

Matlab: Different 1-D FFT results with and without zero-padded

The mean of signal $x$ is not zero. Try on the first line: $X=\texttt{fft}(x-\texttt{mean}(x))$.
9herbert9's user avatar
1 vote

How to increase the spectral resolution?

Actually, you can achieve exact frequency retrieval from the DFT samples: Super-Resolving a Frequency Band. What is interesting is that you have an exact formula to characterize the frequency with ...
Guo Ruiming's user avatar

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