HP 85108, System Manual

Page: 67 / 136

Measure a 30 dB Amplifier. Figure 3-25 sho ws the setup for measuremen t of an amplier
ha ving ab out 30 dB of gain. Using the standard RF source p o w er setting of +9 dBm, the
signal lev el at P ort 1 is ab out +0 dBm, the lev el at the b2 mixer is ab out +5 dBm, and the
signal lev el at the rev erse p ole of the forward/rev erse switch is ab out +30 dBm. In order to
a v oid damage:
The A TTENUA TOR POR T: 2 step attenuator m ust b e set to at least 20 dB to protect the
b2 mixer; and,
An attenuator or isolator m ust b e added in the rear panel POR T 2 links to reduce the
signal lev el at the rev erse p ole of the switch to b elow +20 dBm.
If an y IF O VERLO AD message or O annotation is display ed on the net w ork analyzer when
y ou are op erating in the normal BW, non pulsed-RF mo de, the RF p o w er lev el m ust b e
low ered un til the message no longer app ears.
An isolator, pro viding ab out 30 dB of isolation b et w een P ort 2 and the switch, is the
b est c hoice b ecause it can preserv e the dynamic range for rev erse measuremen ts. Better
p erformance for the rev erse measuremen ts will b e obtained b ecause the isolator will minimize
the insertion loss from the rev erse p ole of the switch to P ort 2, and to a2.
Note
The net w ork analyzer can not sense IF Ov erload conditions in the pulsed-RF,
wide BW mo de of op eration. Alwa ys c hec k the user 1 through user 4 lev els to
b e sure they are b elow 010 dB indicated on the display .
Figure 3-25. Measuring a 30 dB gain Amplifier
Measure an Amplifier with High Input Lev els. Figure 3-26 sho ws the setup for measuremen t
of an amplier with ab out 20 dB of gain that needs an input lev el of ab out 40 dBm. A 40
dB gain amplier is installed in the rear panel POR T 1 links to b o ost the signal lev el to the
desired v alue without exceeding +43 dBm (20 w atts). The signal lev el at the test p ort is
Operation 3-31