4-25 Limit Chapter 4 — Spectrum Analyzer
4-38 MS20xxA VNA Master UG 10580-00166 Rev. C
Limit Edit
This soft key displays a submenu that allows creating or editing of single or
multi-segment limit lines. The currently active limit point is marked by a red circle on
the display.
Move Limit Limit/Point
Selects whether activity from the Frequency and Amplitude soft keys (described
below) affect the entire limit or only the active limit point. Values shown in the
Frequency and Amplitude soft keys represent values for the current limit point.
If Move Limit is set to Limit, any change to these values for the active point will
result in similar changes for all points in the limit.
Frequency, ## Hz
The frequency of each inflection point in a limit line can be individually set.
When a new point is added, it takes on a value halfway between two existing
points, or it takes on the stop frequency of the current sweep if no point is higher
in frequency than the one being added. See the Add Point soft key description for
more details. Use the keypad, the Left/Right arrow keys, or the rotary knob to
change the frequency of an inflection point.
Amplitude, ### dBm
The amplitude of each inflection point can also be individually set. By default,
when a new point is added, it takes on the amplitude that is on the limit line at
the frequency where the point was added. Use the keypad (using the ± key to set
a negative value), the Up/Down arrow keys, or the rotary knob to move the point
to the desired value. The unit of the amplitude limit is the same as the current
vertical amplitude unit. See the
Add Point soft key description in the next
paragraph for more details.
Add Point
The precise behavior of this soft key depends upon which inflection point is active
at the time that the key is pressed. If the active limit point is somewhere in the
middle of a multi-segment limit line, then a new limit point is added that is
halfway between the currently active point and the point immediately to its
right. The amplitude of the inflection point will be such that it falls on the limit
line. For example, if a limit point exists at 2.0 GHz with an amplitude of -30 dBm,
and if the next point is 3.0 GHz with an amplitude of -50 dBm, then the added
point will be at 2.5 GHz with an amplitude of -40 dBm. The frequency and
amplitude values of the new point can be adjusted as needed with the Frequency
and Amplitude soft keys.
If the last limit point is active (assuming it is not at the right edge of the display),
then the new limit point will be placed at the right edge of the display at the
same amplitude as the point immediately to its left. Points may not be added
beyond the current sweep limits of the instrument.
Delete Point
This soft key deletes the currently active point. The active point becomes the
point that is immediately to the left of the point that was deleted.
Next Point Left
This soft key selects the inflection point that is immediately to the left of the
current active point, making this newly selected point active for editing or
deletion. With each key press, the selection of the active point moves to the left of
10580-00166C.book Page 38 Thursday, February 21, 2008 12:52 PM
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