Tektronix 2715, Руководство пользователя

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Spectrum Analyzer Menus
6–28
2715 User Manual
You can place the 2715 in the analog display mode by turning off all the display
registers using [A], [B], [C], and [D] (see Display Storage on page 4–20).
However, a more convenient method when two or more registers are active, is to
use item 0 on the Display menu. Item 0 is a toggle that switches the 2715
between analog and digital display modes. If the 2715 is in the digital display
mode, pressing item 0 turns off all display registers (enters analog display
mode). When in the analog mode, pressing item 0 performs one of two actions:
H
If analog mode was entered using item 0, the register configuration prior to
entering analog mode is restored.
H
If analog mode was entered by manually turning off all registers with [A],
[B], [C], and [D], the last register turned off is reactivated.
13. Ensure the C and D display registers are active. Save the C register and
change the center frequency to 280 MHz so you can distinguish the two
active traces.
14. Press [DSPL] [0].
Notice that only the analog signal remains.
15. Press [DSPL] [0] again.
Both the saved C digital display and the current D digital display return (the
same register configuration that was in use prior to entering the analog mode
by selecting item 0).
16. Turn on the B register, and then turn off all registers in the order D, C, B.
17. Press [DSPL] [0].
Notice that the B register, the last one turned off, is the only one reactivated.
18. Reset the center frequency to 300 MHz and turn on only the D register.
Ensemble Averaging
In general, ensemble averaging techniques are used for the same reason as filters,
to enhance the desired signal-to-noise ratio. Narrow resolution BW or video
filters reduce the noise by reducing the 2715’s bandwidth. Unfortunately, they
also require slower sweep speeds, and in the cases of broadband signals, the
filters may limit the signal energy. For these applications, we can use ensemble
averaging. However, if ensemble averaging is used with pulsed waveforms
without taking special care to synchronize the 2715 to the signal, erroneous
measurements result. This is because of the way scanning spectrum analyzers
determine the spectrum of pulsed signals. See Tektronix application note
26W-7037-1, Spectrum Analyzer Fundamentals, for more information about
pulse measurements.
Changing the Display
Mode