Text preview for : 5988-8644EN.pdf part of HP 5988-8644EN HP Publikacje 5988-8644EN.pdf
Back to : 5988-8644EN.pdf | Home
Agilent
PNA Microwave Network Analyzers
Application Note 1408-7
Amplifier Linear and
Gain Compression Measurements
Table of Contents
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2
Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
Transmission Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
Reflection Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
Gain Compression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
Accuracy Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
Difference between Power Level Accuracy and Power Level Linearity . . . . . . . . . . . . . . .17
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
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 linear S-parameters and gain
compression using Agilent's microwave (MW) PNA Series of vector network analyzers.
The MW PNA Series can also be used for testing amplifier nonlinear parameters such as
harmonics and intermodulation distortion. Agilent Application Notes 1408-8 and 1408-9
cover the topics of harmonics and intermodulation distortion testing 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.
2
Definitions
Gain
Amplifier small signal gain is defined as the ratio of an amplifier's output power delivered
to a Z0 load to the input power delivered from a Z0 source, where Z0 is the characteristic
In this application note, the device impedance in which the amplifier is used (50 ohms in this note). In logarithmic terms,
under test (DUT) is an amplifier with the gain is the difference in dB between the output and input power levels at a particular
following specifications. frequency.
Frequency range 0.10 to 1000 MHz Reverse isolation
Minimum small Reverse isolation is a measure of transmission from output to input. The measurement of
signal gain 20 dB isolation is similar to the measurement of small signal gain, except that the stimulus is
applied to the amplifier's output.
Input SWR 1.5:1
Output SWR 2.0:1 Deviation from linear phase
Ideally, the phase shift through an amplifier is a linear function of the frequency applied.
Output 1 dB compression +3 dBm The amount of variation from this theoretical phase shift is called deviation from linear
phase or phase linearity.
Group delay
Group delay is a measure of the transit time through an amplifier at a particular frequency.
Note
It is defined as the derivative of the phase response with respect to frequency. Similar to
MW PNA [front-panel keys] are shown in
brackets, while the softkeys are displayed in deviation from linear phase, it is a measure of amplifier distortion.
bold; "menu item" refers to the Windows