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Agilent AN 1287-6
Using a Network Analyzer
to Characterize High-Power
Components
Application Note
DUT
Table of Contents
3 Introduction
3 Defining high power
4 Why high-power measurements can be challenging
5 Network analyzer configurations for measuring
high-power devices
6 Configuration 1
7 Configuration 2
9 Configuration 3
11 Configuration 4
12 Configuration 5
14 Configuration 6
14 Additional configurations
15 Source leveling
15 Source leveling using power-meter calibration
16 Source leveling using external leveling
17 Calibration -- purpose and types
17 Calibrating tips for best results
17 Dynamic accuracy
18 Choosing calibration power levels
18 Calibrating at one power level versus two power levels
19 Common problems of high-power measurements
19 Amplifiers with AGC loops
19 On-wafer devices (pulsed measurements)
23 Appendix
23 Network analyzers--definition and capabilities
25 Test sets
26 Calibration
27 Suggested reading
Introduction Defining high power
This application note describes linear and nonlinear What might be considered "high-power device
measurements of high-power components and how output" (e.g., 30 dBm or 1 Watt) in one application
to use a network analyzer for making them. It covers can be insignificant in another application, such as
the power limitations of a network analyzer, and a radar test that uses devices with power levels in
special network-analyzer equipment configurations the 60 dBm (1,000 Watt) range. In this note, "high
for high-power measurements. How to improve power" refers to a power level above the compres-
the accuracy of high-power measurements and sion level and certainly above the damage level of
solve common problems when making high-power a standard network analyzer. Therefore, a power
measurements are also described. amplifier with an output beyond the measurement
capability of a standard network analyzer would be
To get the most from this note, you should have a classified as a high-power device. We extend our
basic understanding of network analyzers and the definition to also include devices that require a
measurements you can make with a network ana- drive level that is higher than a standard network
lyzer. For a basic review, please see the Appendix analyzer can provide. So a high-power device is
at the end of this note. Additional network analysis one that delivers more power than a standard
literature and study materials can be ordered network analyzer can measure, or requires more
through Agilent Technologies. A reference list is input power than the analyzer can provide.
included at the end of the note.
3
Why high-power measurements can be 2. High-power measurements require special
challenging network-analyzer configurations. This can mean
Two main challenges exist when measuring high- adding attenuation or a coupler between the out-
power devices: put of the device under test (DUT) and the input
of the test instrument to protect the receiver. It
1. The measurements performed on high-power can also mean adding amplification to the stimulus
devices can be different than those required to signal if more power is required. Calibration and
characterize lower-power devices. Measurements accurate measurements become significantly more
of high-power devices also can be performed dif- complex as additional equipment is added to the
ferently than those made at lower power levels. test setup. In some configurations the additional
hardware can make some types of calibration
Pulsed measurements are a good example. impossible, or limit the number of measurable
Measurements typically are not pulsed at lower parameters. For example, reverse S-parameters
power levels since device overheating tends not to cannot be measured in some configurations. The
be a problem. High power can heat up a device, inability to perform certain calibrations can limit
affecting its measured characteristics. Many on- the accuracy of the measurements.
wafer measurements, for example, require pulsed
RF and pulsed DC bias, which reduces the average This application note will show configurations
power dissipation and keeps the temperature of ranging from those that are easy to assemble but
the device constant. may have limited accuracy or measurement capa-
bility, to more complex configurations that are
very accurate and can make the same measure-
ments as a standard network analyzer.
4
Network analyzer configurations for measuring The configurations are ordered by the degree of
high-power devices measurement capability. In general, the increased
The high-power test configurations described in capability results in increased complexity in the
this note are designed to boost the power coming configuration. The first configuration is simple --
from the network analyzer's source as necessary, it uses a standard network analyzer and doesn't
and also to protect components such as the require high drive power, which means the network
receivers, couplers, and switches inside the analyzer's source does not need to be boosted. The
network analyzer from excessive power levels. other configurations measure devices that require
high-power inputs and also have high-power out-
To select the correct network analyzer configura- puts. Measuring these devices requires amplifying
tion, you will need to consider the DUT and the the network analyzer's source signal somewhere
required measurements and accuracy. This section along the RF path before it reaches the DUT. The
shows high-power test configurations including the high output power also requires protection for the
necessary hardware, how to set up and calibrate couplers, receivers, and switches inside the analyzer.
these configurations, and the advantages and
limitations of each.
Available high-power measurements Available calibrations
Forward
Forward transmission
Boosted transmission and reflection Forward/ Full
Configuration Complexity source only only reverse two-port Response
1 low X X X
2 low X X X
3 medium X X X
4 medium X X X
5 high X X X X
6 high X X X
5
Configuration 1 Network analyzer
Configuration summary