
DC FM vs. EFC or 10 MHz A/B
Making measurements using a PLL requires that one of the sources being
measured is a VCO. A VCO can be used to track or tune at the Carrier
Frequency or at the down converted (IF) frequency. In both cases a variety
of block diagrams can be used.
Tuning the DUT can be done directly to phase lock the DUT to the
reference source. Although this technique is acceptable it is not common
due to hardware constraints at high frequencies.
SOURCE CONTROL
FOR
MEASUREMENT USING
R
PHASE LOCK LOOP
DUT
USER'S SRCE
MANUAL CNTRL
_REF S0URCE_
8662A
SYSTEM CNTRL
TIME BASE
_0N C0NV._
U729C
SYSTEM CNTRL
HP
I1S48R
TUNE VOLTPfGE
Figure 6-15. DUT Tune Voltage
Down Converters 6-37
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