Measuring Gain Compression; Diagram Of Gain Compression - Agilent Technologies 8719D User Manual

Measuring Gain Compression

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 dB is called the 1 dl3 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 dI3 compression occurs and the absolute power out (in dBm) at
compression. The following steps provide detailed instruction on how to apply various features
of the analyzer to accomplish these measurements.
If the default output power of your analyzer is not high enough to force the
Note
amplifier under test into compression, then the following procedure may have
to be performed with the addition of Option 007 or Option 085. Refer to "Hi
Power Measurements" for information on using Option 085.
1. Set up the stimulus and response parameters for your amplifier under test. To reduce the
effect of noise on the trace, press:
2. Perform the desired error correction procedure. Refer to Chapter 5, "Optimizing
Measurement Results," for instructions on how to make a measurement correction.
3. Hook up the amplifier under test.
4. lb produce a normalized trace that represents gain compression, perform either step 5 or
step 6. Step 6 is optional
M a k i n g M e a s u r e m e n t s
Figure 2-46. Diagram of Gain Compression