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Agilent
PNA Microwave Network Analyzers
Application Note 1408-8
Amplifier Swept-Harmonic Measurements
Table of Contents
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2
Swept-Harmonic Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2
Test Methodology Alternatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
Technique A1. Source Harmonics Not Filtered, Basic Calibration . . . . . . . . . . . . . . . . . . . .3
Technique A2. Source Harmonics Filtered, Basic Calibration . . . . . . . . . . . . . . . . . . . . . . . .8
Technique B. Source Harmonics Not Filtered, Scalar-Mixer Calibration . . . . . . . . . . . . . .12
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
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 harmonics, using the microwave
(MW) PNA Series of vector network analyzers. Linear parameters, such as gain and
return loss, are covered in Agilent Application Note 1408-7. Intermodulation distortion
is covered in Agilent Application Note 1408-9.
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 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 equip-
ment costs are reduced. The purpose of this application note is to demonstrate how to
use the Agilent MW PNA Series network analyzers to measure amplifier harmonics.
Swept-Harmonic Due to inherent nonlinearities, an amplifier generates additional responses, called harmonics,
at integer multiples of the stimulus frequency, or harmonics. Harmonic distortion is
Measurements defined as the difference in absolute power between the fundamental tone and the
harmonic response, expressed in dBc, for a specified input or output power.
In this application note, the device-
under-test (DUT) is an amplifier with the
Traditionally, harmonic measurements are made with a spectrum analyzer at several
following specifications.
continuous wave (CW) frequencies. Many frequencies must be tested for complete
Frequency range 1.4 to 2.4 GHz characterization, which can dramatically increase test time. With the MW PNA Series
Minimum small frequency-offset mode (FOM), you can make swept frequency harmonic measurements.
signal gain 10 dB This capability provides a real-time update of the measured harmonic response versus
frequency, very fast. The network analyzer source is set to the input frequency, while the
Input SWR 1.5:1 receivers are tuned to the desired harmonic (2nd, 3rd,...). Higher harmonics (4th, 5th,...)
Output SWR 2.0:1 can also be measured, as long as the maximum frequency does not exceed that of the
analyzer. MW PNA Series analyzers are available in 20, 40, 50, and 67 GHz models.
Output 1 dB compression +3 dBm
Third order intercept +14 dBm With the MW PNA Series, the power of the fundamental tone is measured on one channel,
while the harmonic response is measured on another channel. In both cases, the source
is set to the input frequency.
Note
MW PNA [front-panel keys] are shown in
brackets, while the softkeys are displayed in
bold; "menu item" refers to the Windows