Agilent Technologies 8753ET User Manual page 415

Device Measurement
Now the unknown is measured to obtain a value for the measured response, S
to Figure 7-33.
Figure 7-33 Measured S
This is the one-port error model equation solved for S
each test frequency, S
11A


S
11M
S
= -----------------------------------------------------------
11A

E S
SF 11M


For reflection 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 reflection coefficient as the load used to determine directivity. The additional reflection error caused by an
improper termination at the test device's output port is not incorporated into the one-port error model.
Two-Port Error Model (ES Models Only)
The error model for measurement of the transmission coefficients (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 as shown in
the full two-port error model.
11
can be computed as follows:

– E
DF

E
+
E
–
RF
DF
. Since the three errors and S
11A
Figure 7-34. These errors are effectively removed using
Operating Concepts
Measurement Calibration
, at each frequency. Refer
11M
are now known for
11M
7- 47