Measure An Ampli Er With High Input Levels - HP 8510 User Manual

Measure an Amplifier with High Input Levels
Figure 10-3 shows the setup for measurement of an ampli er with about 20 dB of gain that
needs an input level of about 40 dBm. A 40 dB gain ampli er is installed in the rear panel
PORT 1 links to boost the signal level to the desired value without exceeding +43 dBm (20
watts). The signal level at the test port is about +60 dBm, making the signal levels at the a1
mixer and the b1 mixer over +30 dBm. In order to avoid damage:
The ATTENUATOR PORT 1: attenuator must be set to 30 dB in order to reduce the a1
and b1 signal levels to below 10 dBm;
On the transmission return side, the ampli er output is about 60 dBm, making it necessary
to add 20 dB of loss between it and Port 2 in order to reduce the signal level incident at
Port 2 to less than +43 dBm for the HP 85110A, and +47 dBm for the HP 85110L;
The ATTENUATOR PORT 2: step attenuator must be set to 30 dB in order to protect the
b2 mixer; and
The reverse pole of the forward/reverse switch must be protected by installing an attenuator
or isolator in the rear panel PORT 2 links to reduce the signal level at the reverse pole of
the switch to below +20 dBm.
The coupler is used in the transmission return signal path because it provides the necessary
loss and will probably provide a more stable signal path than a high power attenuator that
would otherwise be required. A high power termination is required to terminate the through
arm of the coupler.
Use these examples as a guide for considerations that are special to your test setup.
Figure 10-3. Measuring an Amplifier with High Input Levels
10-4 High Power Measurements