Rohde & Schwarz Smart Instruments UP300, Руководство по эксплуатации

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R&S UP300/350 Analyzer
Operating Manual, 11/2007 6-253 E-1147.2759.00
Selecting the FFT Size
Use For a detailed measurement, select a higher FFT resolution. As the FFT size
increases, the signal resolution also increases and the noise bandwidth
decreases. However, the higher the FFT size is, the lower the measurement
speed will be.
You can select FFTs with the following size:
ƒ 1024
ƒ 2048
ƒ
4096
ƒ 8192
ƒ 16384
Note: The setting is always valid for both channels (Ch 1&2).
Selecting the
FFT size
1. Press the function key in the menu.
A selection field containing the available settings is displayed. The
default setting is “1024“.
2. Use the rotary knob
[11] to select a setting.
3. Press the ENTER key
[5] to close the selection field.
The new setting is stored and displayed in the parameter field.
Selecting the FFT Window
Use According to system theory, the FFT regards a signal section as being
continued infinitely and periodically. Usually, however, infinite continuity is not
possible at the section boundary. Discontinuity at the section boundary would
be evaluated as a pulse (with white spectrum). This pulse spectrum is
superimposed on the actual (useful) signal spectrum ("leakage").
Remedy: The signal section intended for the FFT is
attenuated with respect to zero at both ends by a greater or lesser degree by
means of the window function. The FFT then regards the signal as
continuous. Window functions therefore help to minimize this "leakage" (this
is, however, accompanied by a reduction in selectivity).
Ch 1&2