65
Keysight InfiniiVision HD3-Series Oscilloscopes
User's Guide
4 FFT Spectral Analysis
FFT is used to compute the fast Fourier transform using analog input channels or a
lower math function. FFT takes the digitized time record of the specified source
and transforms it to the frequency domain. When the FFT function is selected, the
FFT spectrum is plotted on the oscilloscope display as magnitude in dBV versus
frequency. The readout for the horizontal axis changes from time to frequency
(Hertz) and the vertical readout changes from volts to dB.
Use the FFT function to find crosstalk problems, to find distortion problems in
analog waveforms caused by amplifier non-linearity, or for adjusting analog filters.
To display a FFT waveform:
1 From the menu, choose Analyze > FFT....
2 In the FFT dialog box, select On.
The following FFT spectrum was obtained by connecting a 2.5 V, 100 kHz square
wave to channel 3. The time domain horizontal scale is set to 50 µs/div. The
channel 3 vertical scale is set to 500 mV/div. The FFT Center frequency is 500 kHz,
the frequency Span is 1 MHz, and window is set to Hanning. The FFT waveform
vertical scale is set to 20 dBV, and the vertical offset is set to -40.0 dBV.
To Next Page
Loading...
