Agilent Technologies E8247C, Руководство пользователя

Страница: 190 / 220

180 Chapter 9
Two-Tone Waveform Generator
Overview
Overview
The two-tone mode builds a waveform that has two equal-powered CW signals, or tones. The default
waveform has two tones that are symmetrically spaced from the center carrier frequency, and have
user-defined amplitude, carrier frequency, and frequency separation settings. The user can also align the
tones left or right, relative to the carrier frequency.
The two-tone waveform generator is designed for testing the intermodulation distortion characteristics of
non-linear devices, such as mixers or amplifiers. Intermodulation distortion (IMD) occurs when non-linear
devices with multiple input frequencies interfere with adjacent channels or cause unwanted outputs at other
frequencies. The two-tone waveform generator supplies a signal 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.
Two-tone waveforms are created using the internal I/Q baseband generator and stored in ARB memory for
playback. Although the two-tone mode generates a high-quality waveform, a small amount of IMD occurs.
In addition to IMD, a small amount of carrier feedthrough and feedthrough-related IMD may be present
when the spacing between the tones is centered on the carrier frequency. To minimize carrier feedthrough for
a two-tone signal, you must manually adjust the I and Q offsets while observing the center carrier frequency
with a spectrum analyzer. For measurements that require the absence of IMD and carrier feedthrough, you
can create distortion-free multitone signals using Agilent Technologies’ Signal Studio software Option 408.
NOTE
For more information about two-tone waveform characteristics and the PSG vector signal
generator two-tone format, download Application Note 1410 from our website by going to
www.agilent.com and searching for “AN 1410” in Test & Measurement.