Fluke 9640A Series, Instruction Manual

Page: 98 / 324

9640A
Instruction Manual
3-50
Applying an Offset to a Frequency-Modulated Output Signal
Using the
FM Modulation
screen the user can introduce an offset value for all four
parameters of the signal:
Frequency
,
Level
,
Mod Rate
, and
Deviation
. Once the offsets
are in place, they remain active until they are changed or until the Instrument is powered
on again.
Use the following procedure to set an offset for one or more of the four signal
parameters:
1.
Create a frequency-modulated output signal as described in the previous procedure.
2. Select the desired field:
Frequency
,
Level
,
Mod Rate
, or
Deviation
(parameter
field).
3. Select the
Offset
for the parameter (bottom of the screen). An Offset label appears on
the right of the screen.
4. Press the
Offset
soft key to select the offset field.
5. Press the
Offset
soft key, and enter the desired offset value. Notice that the value in
the parameter field follows the offset value.
6. To toggle the offset value off and on, use the
Toggle Offset
soft key at the bottom of
the display.
7. To disable the offset, use the
Offset Disable
soft key at the bottom of the display.
8. Repeat this procedure, as needed, for each signal parameter.
17
Creating a Phase-Modulated Output Signal
Use the following procedure to create a phase-modulated output signal and, if required, to
define the incremental step values by which the frequency, level, modulation rate and
deviation of the output signal can be increased and decreased. Refer to Table 3-18 for a
list of the fields available on the
Modulation
screen and the limits associated with each
field.
Note
Phase modulation is generated by applying sinusoidal frequency
modulation with peak deviation derived from the phase deviation and rate
settings (F
d
=
φ
d
x F
rate
).
1. Press

.
2. Press the
Modulation Select
soft key to expand the selections at the bottom of the
screen.
3. Press the P
M
soft key to activate the P
M Modulation
screen.
4. Select the
Frequency
field, and enter the desired output frequency.
5. If a frequency step is required, press the
Frequency
soft key again until a
Freq Step
field appears at the bottom of the screen.
a.
Select the
Freq Step (Step Size)
field.
b. Enter the desired frequency step in the field.
6. Select the
Level
field and enter the desired output level.