HP 8642A - Page 280

Performance Tests
4-12. SWR TEST
SPECIFICATION:
DESCRIPTION:
4-30
Model 8642A/B
PERFORMANCE TESTS
Electrical Characteristics Performance Limits
Conditions
SWR <1.5:1
<0 dBm
<2.0:1
;::0 dBm
SWR measurement is divided into two parts: High Level SWR and Low
Level SWR.
In
the High Level SWR Test, the HP 8642 frequency is set to the frequency
of interest because the ALC loop output impedance is seen directly at the
front panel RF output connector. This is the only frequency where the HP
8642 output impedance is valid. In this test the maximum and minimum of
the standing wave are measured directly on a measuring receiver. The SWR
is computed from the ratio of these two values.
In
the Low Level SWR Test, the return loss is measured at each attenuator
step for worst case frequencies. Return loss is measured by first measuring
the power that will be applied to the HP 8642 RF Output. (This is done
through the SWR bridge to calibrate out the loss of the bridge. Then the HP
8642 is connected to the SWR bridge and the reflected power is measured.
The difference between the two measurements is the return loss. Note:
The HP 8642 frequency
is set so that it will not interfere with the
measurement.
o 0 0 I . I 0 6ST~~d
REF EXT
INPUT
MEASURING
o 0 0 DD 00000 0 0 00
RECEIVER
DODD DOCJDO 0 0
OOCDO 88 El888§! 0$
HP 8642A1B
-< • RF
RF
N • OUTPUT
INPUT
SYNTHESIZED
n. I
SIGNAL GENERATOR
w'
J- •
'" .
• STEP 2B~
SHORT
I
.... a ....
I SENSOR I
~:""" I MODULE I
RF OUTPUT
OUT.J SWR BR I DGE
~
RF
RF INPUT OUTPUT
REFERENCE
REF EXT
SIGNAL
INPUT
GENERATOR
Figure 4 -8. SW R Test Setup