Technical data

5-35
Operating Concepts
Measurement Calibration
Figure 5-32. 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:
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
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 Figure 5-33 on page 5-35. These errors are effectively
removed using the full two-port error model.
Figure 5-33. Major Sources of Error
S
11A
S
11M
E
DF
–()
E
SF
S
11M
E
DF
–()
E
RF
+
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