User`s guide

372 Agilent X-Series Signal Generators User’s Guide
Multitone and Two–Tone Waveforms (Option 430)
Using Two–Tone Modulation
Figure 14-2
Minimizing Carrier Feedthrough
This procedure describes how to minimize carrier feedthrough and measure the difference in power
between the tones and their intermodulation distortion products. Before beginning this procedure, it
is important that a recent I/Q calibration has been performed on the instrument. The procedure for
performing an I/Q calibration (refer to “I/Q Calibration” on page 210).
This procedure builds upon the previous procedure.
1. On the spectrum analyzer, set the resolution bandwidth for a sweep rate of about
100 to 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 Internal Baseband Adjustments > 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.
7. Turn on waveform averaging.
Intermodulation
Distortion
Two–Tone
Channels
Carrier Feedthrough
Distortion
Carrier
Feedthrough
For details on each key, use key help as described on page 44.