Windowing in frequency domain. how to cut a spectrum using window function in frequency domain?

1. What is window function in FFT?
2. What does a windowing function do?
3. How does windowing reduce spectral leakage?
4. How do you reduce spectral leakage?

What is window function in FFT?

A window function provides a weighted selection of a portion of a time waveform for fast Fourier transform (FFT) analysis. It is generated by multiplying the original time waveform by a user-defined window function of some width. In this case, width equals two times the number of analysis lines.

What does a windowing function do?

Window functions perform calculations on a set of rows that are related together. But, unlike the aggregate functions, windowing functions do not collapse the result of the rows into a single value. Instead, all the rows maintain their original identity and the calculated result is returned for every row.

How does windowing reduce spectral leakage?

Spectral leakage is caused by discontinuities in the original, noninteger number of periods in a signal and can be improved using windowing. Windowing reduces the amplitude of the discontinuities at the boundaries of each finite sequence acquired by the digitizer.

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).