10
–19
FFT Setup
Setting Up FFT Span and Resolution
The FFT (Fast Fourier Transform) converts a time domain
waveform into frequency domain spectra similar to those of
an RF spectrum analyzer display. But unlike the analyzer,
which has controls for span and resolution bandwidth, FFT
span is determined by sampling rate, while resolution
bandwidth is inversely proportional to record length.
Frequency Resolution
∆
f
Correctly setting up an FFT starts with the frequency resolution,
or
∆
f. This parameter is the spacing of samples in the frequency
domain display. The
∆
f is set by inputting the time duration of
the time domain signal to the FFT. If an acquisition channel
(Channel 1 or 2, or 3 or 4) is the source, then the waveform
duration is the capture time: the TIME/DIV setting multiplied by
ten.
The relationship between capture time and frequency
resolution is illustrated here.
TIME
CAPTURE TIME
= 10 X TIME / DIV
FREQUENCY
AMPLITUDE
AMPLITUDE
∆
f
FREQUENCY
RESOLUTION
ACQUIRED WAVEFORM
FAST FOURIER TRANSFORM (FFT)
∆
f = 1/ CAPTURE TIME
Summary of Contents for 9300C Series
Page 1: ...Operator s Manual LeCroy 9300C Series Digital Oscilloscopes Revision A January 1998 ...
Page 8: ...1 3 billed for parts and labor related to the repair work and for shipping ...
Page 18: ...4 1 4 Introduction to the Controls Two Channel Front Panel ...
Page 19: ...4 2 Introduction to the Controls Four Channel Front Panel ...
Page 92: ......
Page 111: ...11 3 Dual Quad ...
Page 112: ...11 4 Display Parameter s XY only ...
Page 113: ...11 5 XY Single XY Dual ...
Page 138: ...12 21 Ø FLASH UPDATE Offering the Update from and Update Program menus illustrated next page ...
Page 139: ...12 22 UTILITIES The full screen warning message shown when FLASH UPDATE has been selected ...
Page 142: ...13 2 WAVEFORM STORE RECALL ...
Page 182: ......
Page 189: ...A 15 9344C Series 9350C Series 9354C Series 9354CTM 50 000x 9344CL 9350CL 9354CL 100 000x ...
Page 252: ...E 6 Appendix E ...
Page 275: ...Index 9370C 9374C Series A 18 9384C Series A 24 Zoom menu 10 7 Zoom of Math Functions 10 1 ...