HP HP 8753E, User Manual, Page: 435 / 699

The second/third harmonic response can be displayed directly in or below the
fundamental or carrier (see 6-84). The ability to display harmonic level versus frequency
or RF power allows “real-time” tuning of harmonic distortion. this swept harmonic
measurement, as well as of the traditional linear amplifier measurements can be made
without reconnecting the test device to a different test configuration.
1 : - 4 5 . 3 4 3 1 : - 4 5 . 3 4 3
I I I
I
Figure 6-84.
Swept Frequency Measurement of and Harmonic Distortion
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 fundamental input to the fundamental output is measured. The narrowband
receiver is tuned to a precise frequency and, as a result, is immune from harmonic distortion.
You may want to quantify the harmonic distortion itself.
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
will vary with frequency, so it is necessary to find the worst case point of gain compression in
the frequency band.
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.
Application and Operation Concepts