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7-43
Operating Concepts
Measurement Calibration
This re-reflection effect and the resultant incident power variation are caused by the
source match error, E
SF
as shown in Figure 7-27.
Figure 7-27 Source Match E
SF
Frequency response (tracking) error is caused by variations in magnitude and phase
flatness versus frequency between the test and reference signal paths. These are due
mainly to coupler roll off, imperfectly matched samplers, and differences in length and loss
between the incident and test signal paths. The vector sum of these variations is the
reflection signal path tracking error, E
RF
as shown in Figure 7-28.
Figure 7-28 Reflection Tracking E
RF
These three errors are mathematically related to the actual data, S
11A
, and measured
data, S
11M
, by the following equation:
S
11M
E
DF
S
11A
E
RF
1
E
SF
S
11A
–
-----------------------------------------+=