HP 8753E manual Gain Compression

The second/third harmonic response can be displayed directly in dBc, or dE3 below the fundamental or carrier (see Figure 6-84). The ability to display harmonic level versus frequency or RF power allows “real-time” tuning of harmonic distortion. Further, this swept harmonic measurement, as well as all of the traditional linear amplifier measurements can be made without reconnecting the test device to a different test configuration.

21 Jun 1994 12-45.43

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Figure 6-84.

Swept Frequency AmpHer Measurement of 2nd and 3rd Harmonic Distortion (dBc)

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 dE3 is called the 1 dE? 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.

Once that point is identified, you can perform a power sweep of that CW frequency to measure the input power at which the 1 dB compression occurs and the absolute power out (in dBm) at compression.

6-W Application and Operation Concepts