HP 8753D, Руководство пользователя, Страница: 326 / 678

Device Measurement
Now the unknown is measured to obtain a value for the measured response , S
11M
, at each
frequency (see Figure 6-40).
Figure 6-40. Measured S
11
This is the one-port error model equation solved for S
11A
. Since the three errors and S
11M
are
now known for each test frequency , S
11A
can be computed as follows:
S
11 A
= S
11 M
0
E
D F
E
S F
(S
11 M
0 E
D F
) + E
RF
F or reection measurements on two-port devices , the same technique can be applied, but
the test device output port must be terminated in the system characteristic impedance . This
termination should have as low a reection coecient as the load used to determine directivity .
The additional reection error caused by an improper termination at the test device's output
port is not incorporated into the one-port error model.
Two-P ort Error Model
The error model for measurement of the transmission coecients (magnitude and phase) of a
two-port device is derived in a similar manner . The potential sources of error are frequency
response (tracking), source match, load match, and isolation (see Figure 6-41). These errors are
eectively removed using the full two-port error model.
Application and Operation Concepts 6-59