FFT Analyzer Basic FAQ
Question number FAQ-0751
What types of time window functions are there, and how do you choose which one to use?
A practical way to reduce leakage error is to weight the beginning and end of the time window being cut so that they are smoothly set to zero. Such a weighting function is called a time window function. The most commonly used window function in FFT analyzers is the Hanning window.
Table 1 summarizes typical window functions and their applications.
Table 1 Typical time windows used in FFT analyzers
| kinds | Equivalent noise bandwidth | Level accuracy | Main uses |
|---|---|---|---|
| Rectangle | Δf | -3.9 dB | transient signal |
| Hanning | 1.5 Δf | -1.42 dB | General use, continuous signal |
| Flat Top | 3.6714 Δf | ±0.1 dB | periodic signal |
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Last updated: 2009-11-16