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Window Functions and Its role in Spectrum Analysis

The cutoff of the signal produces leakage. The FFT produces fence effect. These errors can't be removed. But we can minimize them by useing window function. Below is some commonly used window function:
The window function that has a narrow main band have a good frequency resolution and a bad amplitude resolution. The window function that has a wide main band have a bad frequency resolution and a good amplitude resolution.

The applet produces two test signals:
Select different window functions to cut off signals and to see their difference in the spectrum.
Java Learning Program

Window Function and Its Role