User Manual LW120
Refer to Figures 3-19 and Figure 3-20 throughout the following
description to learn how to program the LW120 to generate
frequency modulation.
Example 1, Modulating
Standard Waveforms
Using the Standard FM
Mode
This example will show how to generate frequency modulation
using the standard waveforms and the Standard FM Mode. The
output frequency will be set to 1 MHz, Deviation Range to 100 KHz
and 100 Hz sine as the modulating waveform. We’ll monitor the
frequency modulation from the front-panel outputs, then compare
the results to the rear-panel sine output connector.
1. Press the FREQUENCY button. Modify Freq to display
1.000000 MHz. Observe and note that the Sclk parameter is
showing 64.00000 MS/s. In standard waveform mode, the Sclk
parameter is set automatically by the instrument and cannot be
modified directly. The information that we need from this display
is the number of points that the LW120 needs to generate 1
MHz. We can find this out from sclk/freq = 64/1 = 64 points. The
number 64 will be needed later to compute the deviation range
parameter.
2. Press the UTILITY button
3. Select and press the Modulations option
4. Select and press the FM option
5. Select the FM State option
6. Rotate the dial clockwise to turn the FM function ON
Select and press the STD. FM Type option. Note that the default
modulating waveform is SIN (sinewave). Leave this option as is for
now. Later you can practice modifying the modulating waveform to
other shapes.
!
50
TTL
POWER
I
0
OUTPUT
LeCroy
MODEL
100 MS/s ARBITRARY WAVEFORM
!
50
CHAN
1
SYNC
CHAN
2
RESET
CURSOR
MAN
TRIG
TRIGGER
AMPLITUDE
FREQUENCY
UTILITY
WAVEFORM
5
6
Figure 3-19. Selecting FM Type
FM State ON
Slope POS
Mode CONT
More
7. Select the Dev parameter. This parameter sets the deviation
range value. Remember that we computed the number of points
that the LW120 is using for generating 1 MHz? We need to use
Using The Instrument 3-23