User Manual LW120
ms.
We’ll now check the results at the rear-panel sine output connector
and compare what we get there to what we see on the front panel.
Remove the cable from the main output connector and connect to
the rear-panel SINE OUT connector. Here is what you should
expect to see when you check this output:
1. Waveform is sinewave having fixed amplitude level of 1V
into 50
Ω
.
2. Sine waveform sweep from 25.6 MHz to 102.4 KHz in 10
ms. Sweep step is linear.
Example 2, Generating
Sweep Using Arbitrary
Waveforms
This example will show how to generate sweep modulation using
the arbitrary waveforms. The start frequency will be set to 100 Hz
and the stop frequency to 25 KHz. We’ll be using linear sweep in
the up direction in 10 ms. We’ll monitor the sweep modulation from
the front-panel outputs, then compare the results to the rear-panel
sine output connector.
Before we start with our LW120 setting, we must know the length of
the arbitrary segment that we’ll use. To simplify matters, let us
download a triangular waveform to the segment that was
constructed using 100 waveform points. From this point it is easy to
compute the frequency and the sample clocks that we need for the
above example.
We want the start frequency to be 100 Hz. Bearing in mind that the
output frequency is equal to the sample clock frequency divided by
the number of points, the start sample clock must be programmed
to be 10 KS/s (10K / 100 = 100 Hz).
1. Press the FREQUENCY button. Modify Sclk to display
10.00000KS/s.
2. Now it is time to check if the number of points will not conflict at
the stop frequency. We can check this by dividing the maximum
possible sample frequency by the number of points from the
above calculations.
Fstop_max = 100MS/s / 100Pts = 1MHz
In this case we should be safe because we plan to sweep to
25KHz only.
3. Now we have to compute the sample clock frequency at the
stop point. Knowing already the number of points we have in
this waveform, the sample clock frequency at the stop point is
computed using the following equation:
Fstop = 100Pts x 25KHz = 2.5MS/s.
4. Press the UTILITY button
5. Select and press the Modulations option
6. Select and press the Sweep option
Using The Instrument 3-37