User`s guide

190 Chapter 8
Multitone Waveform Generator
Creating, Viewing, and Optimizing Multitone Waveforms
Figure 8-5
To Minimize Carrier Feedthrough
This procedure describes how to minimize carrier feedthrough and measure the difference in power
between the tones and their intermodulation distortion products. Carrier feedthrough can only be
observed with even- numbered multitone waveforms.
This procedure builds upon the previous procedure.
1. On the spectrum analyzer, set the resolution bandwidth for a sweep rate of about
100- 200 ms. This will allow you to dynamically view the carrier feedthrough spike as you make
adjustments.
2. On the signal generator, press
I/Q > I/Q Adjustments > I/Q Adjustments Off On to On.
3. Press
I Offset and turn the rotary knob while observing the carrier feedthrough with the spectrum
analyzer. Changing the I offset in the proper direction will reduce the feedthrough level. Adjust
the level as low as possible.
4. Press
Q Offset and turn the rotary knob to further reduce the carrier feedthrough level.
5. Repeat steps 3 and 4 until you have reached the lowest possible carrier feedthrough level.
6. On the spectrum analyzer, return the resolution bandwidth to its previous setting.
Carrier
Feedthrough
Intermodulation
Distortion
Tone 1
Carrier
Feedthrough
Distortion
Tone 10