Agilent Technologies 8719D, User Manual

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Amplifier
Parameters
The HP allows you to measure the transmission and reflection characteristics
of many amplifiers and active devices. You can measure parameters such as gain,
gain flatness, gain compression, reverse isolation, return loss (SWR), and gain drift versus
time. Additionally, you can measure vector parameters such as deviation from linear phase,
group delay, and complex impedance. All of the traditional linear amplifier measurements
can be made without reconnecting the test device to a different test For more
information on amplifier testing and making measurements, refer to Chapter 2, “Making
Measurements.
Figure Amplifier
Gain Compression
Vector network analyzers are commonly used to characterize amplifier gain compression versus
frequency and power level. This is essentially linear characterization since only the relative
level of the input to the output is measured. The narrowband receiver is tuned to a precise
frequency and, as a result, is immune from harmonic distortion.
Gain compression occurs when the input power of an amplifier is increased to a level that
reduces the gain of the amplifier and causes a nonlinear increase in output power. The point at
which the gain is reduced by 1 is called the 1 compression point. The gain compression
vary with frequency, so it is necessary to find the worst case point of gain compression in
the frequency band.
Once that point is identified, you can perform a power sweep of that CW frequency to measure
the input power at which the 1 compression occurs and the absolute power out (in at
compression.
and Operation Concepts 6-147