User`s guide

Chapter 8 185
8 Multitone Waveform Generator
In the following sections, this chapter describes the multitone mode, which is available only in
E8267D PSG Vector Signal Generators with Option 601 or 602:
• “Overview” on page 185
• “Creating, Viewing, and Optimizing Multitone Waveforms” on page 186
See also: Chapter 3, “Basic Digital Operation,” on page 71
Overview
The multitone mode builds a waveform that has up to 64 CW signals, or tones. Using the Multitone
Setup table editor, you can define, modify, and store waveforms for playback. Multitone waveforms
are generated by the internal I/Q baseband generator.
The multitone waveform generator is typically used for testing the intermodulation distortion
characteristics of multi- channel devices, such as mixers or amplifiers. Intermodulation distortion
(IMD) occurs when non- linear devices with multiple input frequencies cause unwanted outputs at
other frequencies or interfere with adjacent channels. The multitone waveform generator supplies a
waveform with a user- specified number of tones whose IMD products can be measured using a
spectrum analyzer and used as a reference when measuring the IMD generated by a
device-under-test.
Multitone waveforms are created using the internal I/Q baseband generator and stored in ARB
memory for playback. Although the multitone mode generates a high- quality waveform, a small
amount of IMD, carrier feedthrough, and feedthrough- related IMD occurs. Carrier feedthrough may be
observed when an even number of tones are generated, since there are no tones at the center carrier
frequency to mask the feedthrough. To minimize carrier feedthrough for an even- numbered multitone
signal, it is necessary to manually adjust the I and Q offsets while observing the center carrier
frequency with a spectrum analyzer.
For measurements that require more than 64 tones or the absence of IMD and carrier feedthrough,
you can create up to 1024 distortion- free multitone signals using Agilent Technologies Signal Studio
software Option 408.
NOTE For more information about multitone waveform characteristics and the PSG vector signal
generator multitone format, download Application Note 1410 from our website by going to
http://www.agilent.com and searching for “AN 1410” in Test & Measurement.