Tektronix TDS5054, Руководство пользователя

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Creating and Using Math Waveforms
3- 154
TDS5000 Series User Manual
Gate
width
Zero phase reference
Time domain acquisition
Frequency domain samples
Gate position
Gate
Trigger
position
Duration
Figure 3- 43: Definition of gate parameters
The gate must reside within the duration interval of the source waveform. If the
source waveform duration is adjusted, and the gate position and width would
result in the gate being outside of that duration, then the gate position or width is
set within the limits.
The width of the gate affects the resolution bandwidth of the spectral analyzer.
See
Using Spectral Math Controls on page 3--152 for more details.
The data contained in the gated region is transformed to the frequency domain.
The gate is identified on the display using dashed markers (similar to cursors).
The default gate width setting is equal to the duration of the source waveform.
Using the Frequency Domain controls. The gated region of the source waveform is
transformed into a spectral phase or magnitude waveform. The horizontal units
are always Hz. The vertical units depend on whether phase or magnitude is
selected. The frequency domain controls for the spectral waveform are span,
center, and resolution bandwidth. The spectrum normally appears on the display
fit to a screen width of 10 divisions.
S pan is the frequency at the end of the spectral waveform minus the frequency at
the beginning of the waveform. The span control maximum value is equal to the
current sample rate divided by two. Therefore, if you are unable to increase the
span to the desired value and if you want to keep the same source waveform
duration, go to the timebase controls and increase the sample rate using the
resolution control. Or, if you want to also decrease the source waveform
duration, adjust the sample rate control. If you decrease the sample rate, the span
setting may decrease, if necessary, to keep the span less than the sample rate
divided by two.