User Manual LW120
7. Using the dial, program the FSK Ramp Time to the desired
value
NOTE
Shifted frequency value in Ramped FSK mode must
always be higher than the carrier frequency. Reverse
setting will not allow the LW120 to execute FSK
operation. Also, SCLK2 - SCLK1
≥
10KHz
Sweep
In sweep modulation, the LW120 sweeps from start frequency set
by the Sclk parameter to stop frequency set by Sweep Stop
parameter. Both the sweep start and the sweep stop control the
sample clock generator at the rear-panel sine output. Sweep
modulation is also available from the front panel outputs, except the
frequency must be computed from the start sample clock and the
number of points that generate the start output waveform.
Confusing? Yes, a bit, but some examples below will remove your
confusion.
To generate Sweep you must specify five parameters:
1. Start Sample Clock
– This is the frequency of the sample clock
as displayed after you press the FREQUENCY button. Note that the
first line on the display shows Freq and some value and the second
line shows Sclk and value. This Sclk is what you need to interpret
your sweep start frequency. This is also the frequency that is
available as sine waveform at the rear-panel sine output. If you do
not care to work with your sine output but want to generate sweep
from the front panel, then you must define your sweep start
frequency first. Here is what you do:
When generating standard waveforms, your sample clock
frequency is computed automatically. In fact, when you program
your waveform frequency, the Sclk value is updated
automatically. You can not access or modify the sample clock
field, it is there for reference only. Although you can not change
the sample clock, this is the value you’ll be using for the sweep
stop frequency.
It is a bit simpler when you generate arbitrary waveforms. The
only value that you see on the display is Sclk and this is the
value of your sweep start frequency. It is also the frequency of
the sine waveform at the rear-panel sine output connector.
However, if you want to know the frequency of your signal at the
front panel outputs, then you must compute it yourself from the
sclk frequency, divided by the number of points in your active
segment. For example, if your sclk is 100MS/s and you have a
1000-points waveform, then your output frequency is 100 KHz.
Using The Instrument 3-33