3-12
SIGNAL MODULATION
The sweep generator provides AM, FM, and square wave modulation
of the output signal. All modulation modes—AM, FM, and square
wave—can be active simultaneously. The following paragraphs provide
descriptions and operating instructions for each modulation mode.
Use the Amplitude Modulation Mode, Frequency Modulation Mode,
and Square Wave Modulation Mode menu maps (Chapter 4, Figures
4-10, 4-11, and 4-12) to follow the menu sequences.
Amplitude
Modulation
Operating
Modes
The sweep generator has two AM operation modes—
Linear AM and Log AM. In Linear AM mode, sensi-
tivity is continuously variable from 0 %/V to
100%/V. The amplitude of the RF output changes
linearly as the external AM input changes.
In Log AM mode, sensitivity is continuously vari-
able from 0 dB/V to 25 dB/V. The amplitude of the
RF output changes exponentially as the AM input
changes.
Providing
Amplitude
Modulation
To provide amplitude modulation, first set up the ex-
ternal signal generator, then connect it to either the
681XXB front or rear panel
AM IN
connector.
Next, press
MODULATION
. At the resulting menu
display, press
AM
. The External AM Status Menu
(below) is displayed.
This menu contains an external AM status window
that shows the current menu selections and the
measured AM Depth. (The AM depth measurement
function measures the voltage of the external modu-
lation signal and calculates the percentage modula-
tion value.) This menu lets you perform the
following:
Turn AM on and off.
Select the Linear AM or Log AM operating
mode.
Set the AM Sensitivity
Select the input impedance (600
Ω
or 50
Ω
) of
the input connector.
LOCAL (FRONT
SIGNAL
PANEL) OPERATION
MODULATION
681XXB OM
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