HP 8753D, User Manual, Page: 328 / 678

Figure 6-43. Load Match E
LF
The measured value , S
21M
, consists of signal components that vary as a function of the
relationship between E
SF
and S
11A
as well as E
LF
and S
22A
, so the input and output reection
coecients of the test device must be measured and stored for use in the S
21A
error-correction
computation. Thus , the test setup is calibrated as described above for reection to establish
the directivity , E
DF
, source match, E
SF
, and reection frequency response , E
RF
, terms for the
reection measurements .
Now that a calibrated port is available for reection measurements , the thru is connected and
load match, E
LF
, is determined by measuring the reection coecient of the thru connection.
Transmission signal path frequency response is then measured with the thru connected. The
data is corrected for source and load match eects , then stored as transmission frequency
response , E
TF
.
Note
It is very important that the exact electrical length of the thru be known.
Most calibration kits assume a zero length thru. F or some connection types
such as Type-N, this implies one male and one female port. If the test system
requires a non-zero length thru, for example , one with two male test ports , the
exact electrical delay of the thru adapter must be used to modify the built-in
calibration kit denition of the thru.
Isolation, E
XF
, represents the part of the incident signal that appears at the receiver without
actually passing through the test device (see Figure 6-44). Isolation is measured with the test
set in the transmission conguration and with terminations installed at the points where the
test device will be connected.
Application and Operation Concepts 6-61