Side lobes not visible in FFT of rect function

1. What does zero padding do in FFT?
2. What does an FFT spectrum show?
3. Why are FFTs mirrored?
4. How do you reduce spectral leakage?

What does zero padding do in FFT?

``Zero-padding'' means adding additional zeros to a sample of data (after the data has been windowed, if applicable). For example, you may have 1023 data points, but you might want to run a 1024 point FFT or even a 2048 point FFT.

What does an FFT spectrum show?

The resulting digital time record is then mathematically transformed into a frequency spectrum using an algorithm known as the Fast Fourier Transform, or FFT. The FFT is simply a clever set of operations which implements Fourier's theorem. The resulting spectrum shows the frequency components of the input signal.

Why are FFTs mirrored?

Because both the positive and negative frequency sinusoids are 90 degrees out of phase and have the same magnitude, they will both respond to real signals in the same way.

How do you reduce spectral leakage?

We have seen that spectral leakage is reduced by tapering the digital signal by a window function before the DFT takes place. A generalization of this technique is the short-time discrete Fourier transform (STDFT).