Agilent Technologies E8247C PSG CW - Manual (Page 180)

170 Chapter 8
Multitone Waveform Generator
Overview
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
www.agilent.com and searching for “AN 1410” in Test & Measurement.