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Agilent
PNA Microwave Network Analyzers
Application Note 1408-9
Amplifier and CW Swept Intermodulation-
Distortion Measurements
Table of Contents
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Intermodulation-Distortion Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Hardware Alternatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Test Methodology Alternatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Technique A. Four Channels, Basic Calibration, CW IMD . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Technique A. Four Channels, Basic Calibration, Swept IMD . . . . . . . . . . . . . . . . . . . . . . . 14
Technique B. One Channel, Basic Calibration, CW IMD . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Technique B1. One Channel, Segmented Sweep, Basic Calibration, CW IMD . . . . . . . . . 29
Technique B2. One Channel, Linear Sweep, Basic Calibration, CW IMD . . . . . . . . . . . . . 33
Technique C. Four Channels Scalar-Mixer Calibration, CW IMD . . . . . . . . . . . . . . . . . . . . 37
Appendix A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Note: The step-by-step procedures in this application note were written for PNA (836xA/B)
and PNA-L (N5230A) network analyzers with firmware revision A.04.06. If you have a PNA
or PNA-L with a different firmware revision, the step-by-step procedures or screenshots
may vary. The concepts and general guidelines still apply.
Introduction This application note covers testing of an amplifier's intermodulation distortion products
using Agilent's microwave (MW) PNA Series of vector network analyzers. The MW PNA
Series can also be used for testing amplifier linear parameters, gain compression, and
harmonics. Agilent Application Notes 1408-7 and 1408-8 cover the topics of linear testing,
gain compression, and harmonics respectively.
Amplifiers are a fundamental building block of microwave systems, and characterizing the
performance of amplifiers is a critical factor in the design process. Network analyzers are
traditionally used for linear amplifier measurements, while spectrum analyzers are used
for nonlinear measurements such as harmonics and intermodulation distortion. However,
many of the modern network analyzers, including the Agilent MW PNA Series, can be
used for nonlinear measurements as well, by enabling the frequency-offset functionality.
Most amplifier test systems include a network analyzer for reflection measurements.
If the network analyzer can also be used for nonlinear measurements, then capital
equipment costs are reduced.
2
Intermodulation-Distortion Intermodulation distortion (IMD) is a measure of the nonlinearity of an amplifier. When
two or more sinusoidal frequencies are applied to an amplifier, the output contains addi-
Measurements tional frequency components called intermodulation products. For an amplifier with input
signals at f1 and f2, the output will contain signals at the following frequencies: nf1 + mf2,
where n, m = 0,