Atek HP 8753D, User Manual, Page: 320 / 677

Figure 6-31. Sources of Error in a Reection Measurement
T o characterize the errors , the reection coecient is measured by rst separating the incident
signal (I) from the reected signal (R), then taking the ratio of the two values (see Figure 6-32).
Ideally , (R) consists only of the signal reected by the test device (S
11A
, for S
11
actual).
Figure 6-32. Reection Coecient
However , all of the incident signal does not always reach the unknown (see Figure 6-33).
Some of (I) may appear at the measurement system input due to leakage through the test
set or through a signal separation device . Also , some of (I) may be reected by imperfect
adapters between a signal separation device and the measurement plane . The vector sum of
the leakage and the miscellaneous reections is the eective directivity , E
DF
. Understandably ,
the measurement is distorted when the directivity signal combines vectorally with the actual
reected signal from the unknown, S
11A
.
6-54 Application and Operation Concepts