Atek HP 8753D, Руководство пользователя, Страница: 93 / 677

Measuring Gain Compression
Gain compression occurs when the input power of an amplier is increased to a level that
reduces the gain of the amplier and causes a nonlinear increase in output power . The point at
which the gain is reduced by 1 dB is called the 1 dB compression point. The gain compression
will vary with frequency , so it is necessary to nd the worst case point of gain compression in
the frequency band.
Once that point is identied, 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. The following steps provide detailed instruction on how to apply various features
of the analyzer to accomplish these measurements .
Figure 2-41. Diagram of Gain Compression
1. Set up the stimulus and response parameters for your amplier under test. T o reduce the
eect of noise on the trace , press:
4 A V G 5
NNNNNNNNNNNNNNNNN
IF BW
NNNNNNNNNNNNNN
1000 4 21 5
2. P erform 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 amplier under test.
4. T o produce a normalized trace that represents gain compression, perform either step 5
or step 6. (Step 5 uses trace math and step 6 uses uncoupled channels and the display
function
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
D1/D2 to D2 ON .)
5.
Press 4 DISPLA Y 5
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
DATA ! MEMORY
NNNNNNNNNNNNNNNNNNNNNNNNNN
DATA/MEM to produce a normalized trace .
6. T o produce a normalized trace , perform the following steps:
a.
Press 4 DISPLA Y 5 and select
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
DUAL CHANNEL ON to view both channels simultaneously .
Making Measurements 2-45