Hioki 8847 - Page 359

Appendix 5 FFT Definitions
A25
Appendix
The following example shows input sine waves of 1050 and 1150 Hz analyzed
with different window functions. Because the frequencies in this example are
close to one another, a rectangular window with a narrow main lobe is able to
separate and display both frequencies, but a Hann window with a wide main lobe
displays the two as a single spectral component.
Flat top window
Time-Domain Waveform Spectrum
Analysis Using a Rectangular Window Analysis Using a Hann Window
N-10
Amplitude
0
0 2 4 6 8 10
-80
-60
-40
-20
0
Frequency (1/W)
Gain [dB]
100 500 1000 5000 10000
-100
-50
0
Frequency [Hz]
Amplitude [dB]
100 500 1000 5000 10000
-100
-50
0
Frequency [Hz]
Amplitude [dB]