Fft And Inverse Fft - HP 3563A Operating Manual

FFT and Inverse FFT

FFT computes a 1024-line
For FFTs on time domain traces, 1024 lines are produced; 801 or 1024 lines are saved and displayed
(depending on the selection of WINDOW LINES 801 or LINES 1024). Because of dithering in the
computation, FFTs on identical data
FIT operation is 1/1024. Figure 15-16 shows an example of the
Trace B Linear Spectrum Resulting from
Computing FFT of 5 kHz Sine Wave in
Trace A
FIT - I
performs an inverse fast Fourier transform
example. If you have performed an
FFT- I ,
the analyzer adds 223 zeros outside the frequency span to fill the 223 lines
domain using
FFT
discarded by the (if it was an 801 point data block; see the description in chapter 3 for LINES
FFT- I
801). The is 6 to 10 dB noisier than
Impulse Response in Trace B resulted
from Computing Inverse FFT of
Frequency Response in Trace B.
FFT
from either a 1024-point complex record or a 2048-point real record.
always produce identical results. The scale factor for the
do not
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Figure 15-16. FFT
FFT on a time record, then transformed it back to the time
FFT. The scale factor for the inverse FIT operation is 1.
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Figure 15-17. Inverse FFT
FFT
command.
TIME'
2
( FFT)
on the active trace. Figure 15-17 shows an
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